Note: Descriptions are shown in the official language in which they were submitted.
21~33835
BACKGROUND OF ~ INVENTION
The present invention relates generally to the
transmission of audio/video television and remote control signals
from a local location to a remote location, and, in particular,
to a wireless audio and video transmitter and receiver system
apparatus capable of accepting external baseband stereo audio and
video signal inputs. In the present wireless stereo audio/video
signal transmitter and receiver system apparatus the transmitter
transmits an FN modulated audio/video signal via an RF carrier in
the 900 MHz band to a remote receiver which regenerates the
original audio/video signal providing both baseband stereo audio
and video signal outputs as well as a modulated mono audio/video
signal output corresponding to a particular television channel.
In addition, a handheld RF remote control transmitter provided at
the remote location transmits RF remote control signals to a
remote control receiver which receives the RF remote control
signal and regenerates a corresponding IR remote control signal
to actuate the local stereo audio/video signal source device.
Advances in technology and manufacturing have resulted
in the video cassette recorder (VCR~ becoming virtually common
place in households which own a television set with such VCR's
almost always possessing stereo audio and remote control
capability. In homes owning multiple television sets, the VCR is
typically placed adjacent to and hardwire connected to a single
designated television set. Should the user desire to view a
video cassette, the user has to view the video cassette on the
particular television set to which the VCR is physically
attached. Sbould the user wish to view the video cassette on
another television set, one alternative is to disconnect the VCR
i from its designated television set, transport the VCR to the
;~ remote location and reconnect the VCR at the remote television.
Another alternative consists of hardwire connecting multiple
television sets to a single VCR using multiple selector switches
to "make" the desired connections to cause the VCR's audio/video
~3~8~
signal to be directed to the desired television set. Stereo
VCR's may further require additional wiring to accommodate the
stereo audio signal capabilities of such VCRs. Likewise, if one
desires to view a television program which is supplied to the
homeowner via a cable television network, the television which
the homeowner wishes to view must be connected to the cable
television network.
In theft prevention and other security applications,
where video cameras are utilized, video cameras must each be
physically hardwired to a monitoring station, or recording
device, often located at distances remote from the camera's
location. In such situations, great lengths of connecting wire
may be required, connections which are susceptible to damage over
time and/or cutting by one attempting to defeat a security
camera.
The limitations of such physical connections are
apparent in that one must either physically move the VCR about
the house or endure the expense and/or unsightliness of having
wire~ run from television to television as well as the ongoing
risk of damage to any such connecting cables.
In addition, where a audio,'video signal source such as
a VCR is connected to drive a remotely placed television the
standard remote control device typically supplied by the VCR
manufacturer is usually inoperative from the remote location
inasmuch as such standard VCR remote control devices most often
utilize infra-red (IR) light signals to communicate remote
instructions to the VCR. The standard remote control's use o~ IR
signals requires that the standard remote control be held by the
user in a "line-of-sight" with the VCR in order to operate since
infra-red signals will not penetrate walls, door~, floors or
other solid objects and instead usually will reflect off of or be
absorbed by such objects. Where walls, doors and floors separate
the VCR from the remote television, as is usually the case in
most home situations, the supplied IR remote control will not
function to control the VCR from the remote location
, : , , .: ~ , . - : . ~ . .
~`33~3~
necessitating that the user walk from the remote television to
the VCR to perform even the simplest function such as pausing a
video cassette tape being played.
Accordingly the present invention seeks to address
these limitations by providing for the wireless transmission and
reception of television signals on an RF band of 90~ MHz by
taking advantage of FCC regulations which allocates a portion of
the 900 MHz band for this application. In addition, the present
invention seeks to address the inoperability of typical standard
infra-red based remote control devices by providing for the
wireless transmission and reception of remote control signals on
an RF band on the order of 500 MHz and regeneration of IR remote
control signals at the location adjaoent the audio/video signal
source device to be controlled.
Moreover, the present invention seeks to provide for a
flexible wireless transmission and reception of television
signals in a manner which provides for the best possible
television picture at the remote television set using the least
costly combination of components.
Accordingly, it is an object of the present invention
to provide a wireless stereo audio/video signal transmitter and
receiver system apparatus having remote control extender
capability which is capable of accepting baseband stereo audio
and baseband video signals as inputs to a transmitter.
Another object of the present invention is to provide a
wireless stereo audio/video signal transmitter and receiver
system apparatus having remote control extender capability which
is capable of accepting a baseband stereo audio input and
transmitting to a remote receiver.
~It is yet a further object of the present invention to
-provide a transmitter which separately processes the two audio
channels forming the stereo audio signal, combines the stereo
audio and video signals and modulate the signals onto an RF
carrier.
.. .
: .. , :
i; , . . . .
., . :: .: : ~
~ `` 2033835
It is an object of the present invention to utilize FM
modulation in order to transmit a signal which does not possess
the limitations of AM modulated signals.
It is still a further object of the present invention
to provide a receiver which down converts a received RF signal to
an IF frequency.
It is yet another object of the present invention to
provide a handheld RF remote control transmitter capable of
transmitting an encoded RF remote control signal corresponding to
the remote control key code function generated by the standard IR
remote control device and thus able to penetrate walls, doors,
floors and other physical obstructions.
Another object of the present invention is to provide a
remote control receiver incorporated into the transmitter housing
which receives the RF remote control signal and regenerates the
appropriate IR remote control signal directing same toward the
audio/video signal source device toward actuating same.
Yet another object of the present invention is to
provide a remote control receiver which may be programmed by the
standard IR remote control device and handheld RF remote control
transmitter to recogni~e received RF remote control signals and
transmit corresponding IR remote control signals in response
thereto.
These and other ob;ects of the invention will become
~pparent in light of thn presont speclfioatioD ~=d dravlngs.
.
- : ". : ~ ,
. - :: : - : ' ~ , .' . : .: : : :~ ' :
.. . ... .
2~3383~
SUMMARY OF THE INVENTION
The present invention comprises a wireless stereo
audio/video signal transmitter and receiver system apparatus with
remote control capability which is capable of accepting an
external baseband stereo audio signal an external baseband video
signal from an external audio/video signal source. The wireless
stereo/video signal transmitter and receiver system apparatus
services to FN modulate a combined stereo audio/video signal
which is transmitted on an RF carrier to one or more remote
receivers which regenerate the original baseband stereo audio
signal and baseband video signal as well as a mono audio/video
signal modulated a particular television channel for use by a
remote external television or monitor device.
A transmitter is provided for connection to an external
audio/video signal source, such as a video cassette recorder
(VCR), and is capable of accepting external baseband stereo audio
signals and external baseband video signals as inputs to the
transmitter. Such inputs are typically provided as RCA jack
terminals on the connector portions of the VCR.
The transmitter includes a subcarrier modulator which
are electrically connected to the baseband stereo audio signal
input. The subcarrier modulator serves to provide pre-emphasis
to the stereo audio signals and separately FM modulates the
stereo audio signals towards converting the signals to modulated
subcarrier audio signals.
A baseband video signal input section is provided ~or
permitting an external baseband video qignal source to be
connected to the transmitter. A video signal processor is
provided and is electrically connected to the baseband video
signal input. The video signal processor serves to provide a
filtered pre-emphasized video signal output.
A combiner electrically connected to the subcarrier
modulator and the video signal processor serves to combine the
modulated subcarrier audio signals with the filtered pre-
: . . . -.
.: , ` ~. : . ` ~ : ~
2~33~35
emphasized video signal. The combined signal being further
processed by the transmitter IF signal processor which is
electrically connected to the combiner. The transmitter IF
signal processor serves to frequency modulate a voltage
controlled oscillator at 2SO MHz and provides as an output a
modulated audio/video signal output.
An up converter is provided and is electrically
connected to the combiner and serves to convert the modulated IF
frequency audio/video signal to an RF frequency signal. An RF
amplifier is provided and is electrically connected to the up
converter and serves to amplify the RF frequency audio/video
signal. Transmitter antenna electrically connected to the RF
amplifier serves to transmit the amplified RF audio/video signal
to the receiver.
A receiver is provided which is capable of receiving
the amplified RF audio/video signal output of the transmitter
antenna towards generating an external modulated mono audio/video
signal as well as an external baseband stereo audio signal and
baseband video signal output.
Receiver antenna is provided with each receiver for
receiving the RF signal transmitted by the transmitter.
Receiver front end, electrically connected to the
receiver antenna, serves to amplify and filter the received RF
signal. Down converter, electrically connected to the receiver
front end is provided and serves to convert the received RF
audio/video signal to an IF audio/video signal.
Receiver IF signal proces~or is provided and are
electrically connected to the down converter. A PLL detector is
electrically connected to the receiver IF signal processor and is
provided towards demodulating the IF signal output of the
receiver IF signal processor towards providing a combined
ba~eband video signal and modulated audio subcarrier signal
output.
Stereo audio signal demodulator electrically connected
to the PLL detector is provided where the stereo audio signal
3~
demodulator converts the modulated audio subcarrier signals to
baseband stereo audio signal outputs. A baseband video signal
generator is provided and is electrically connected to the PLL
detector. The baseband video signal generator provides a
filtered de-emphasized and amplified baseband video signal output
which may be connected to an external television de~ice via
baseband video signal output provided and electrically connected
to the baseband video signal generator.
Audio/video signal modulator electrically connected to
the stereo audio signal demodulator and the baseband video signal
generator is provided and serves to generate a modulated
composite mono audio/video signal output which corresponds to a
particular television channel, in the present example, channel 3
or channel 4. A composite audio/video signal output electrically
connected to the audio/video signal modulator permits the
modulated composite audio/video signal output to be connected to
the external television device.
Further provided is a handheld remote control
transmitter capable of controlling the functions of the external
audio/video signal source by replacing the standard IR remote
control typically provided with such external audio/video signal
sources. The handheld remote control unit includes a command
entry device which permits the user to enter a command towards
actuating a function of the external audio/video signal source as
well as command and coding device electrically connected to the
command entry device which serves to generate an encoded remote
control code sequence depending upon the command entered by the
user on the command entry device. Remote controller RF
transmitter is provided and are electrically connected to the
command encoding device for generating and transmitting an RF
remote control output signal.
The RF remote control output signal is received by the
remote control receiver which in the embodiment disclo9ed herein
is housed within the transmitter. Remote control receiver
, .., . ~.
: ~ , .,, ,, : , ,.
:, ,~ ,:
2033~3~
antenna is provided for receiving the actual RF remote control
signal from the handheld RF remote control transmitter. Remote
control RF receiver and remote control RF detector are provided
for respectively receiving the RF remote control signal
transmitted by the handheld remote control transmitter and
recovering the encoded remote control key code sequence towards
providing as an output the encoded remote control key code
- sequence. A controller electrically connected to the RF detector
is provided together with IR remote control signal transmitter
which is electrically connected to the controller. The I~ remote
control signal transmitter services to generate an IR remote
control signal under the direction of the controller in response
to the corresponding RF remote control signal generated by the
handheld remote control transmitter and received by the remote
control receiver.
An IR command signal receiver is provided for receiving
an IR command signal from the external audio/video signal sources
standard IR remote control towards programming the controller.
An IR command signal detector ls electrically connected to the IR
command signal receiver and serves to provide the controller with
the decoded IR command signal in response to the received RF
command signal.
Accordingly, in operation the wireless audio/video
signal transmitter and receiver system apparatus with remote
control extender capability permits the wireless transmisaion and
remote reception of audio/video signals from a signal source such
as a VCR to a reception device auch as a televi~ion monitor and
the wireless transmission and remote reception of RF remote
control signals from a handheld remote control transmitter
~ towards the regeneration of corresponding IR remote control
; signals towards activating the external audio/video signal source
device from the remote location.
; In the preferred embodiment of the invention, the
~, wireless stereo audio/video signal transmitter and receiver
system having remote control capability includes baseband stereo
. 9
.~
2~33~3~
audio signal input which are comprised of left and right channel
baseband audio signal input connectors for accepting connection
of the left and right channel external baseband audio signals.
The apparatus further includes baseband video signal inp~t which
are comprised of baseband video signal input connectors for
accepting connection of the external baseband video signal.
In the preferred embodiment of the invention, the
baseband video processor preferably comprises a first baseband
video processor buffer, a baseband video processor lowpass
filter, a second baseband video processor buffer, a baseband
video processor pre-emphasis network, first baseband video
processor amplifier, trap, second baseband processor amplifier
and video level control all connected in series to the baseband
video signal input connector where the baseband video processor
serves to remove unwanted frequency components from the baseband
video signal and pre-emphasized video signal.
The subcarrier modulator preferably comprises left and
right channel pre-emphasis network electrically connected to the
baseband stereo audio signal input connectors, which serve to
boost high frequency components of the external baseband stereo
audio signal towards removing noise components from the signals
when later demodulated. Additionally provided are left and right
channel baseband audio subcarrier modulator electrically
connected to the respective left and right channel pre-emphasi6
network for separately modulating the left and right channel
external baseband audio signal6 generating an audio subcarrier
signal output $rom each. The subcarrier modulator $urther
includes left and right channel audio subcarrier signal buffer
electrically connected to the left and right channel baseband
audio subcarrier modulator, respectively.
In the pre$erred embodiment of the invention, the
combiner comprises an audio signal combiner electrically
connected to the left and right channel audio subcarrier buffer
towards actively combining and amplifying the left and right
, .
:., . ~ . . . : ~ . ~ . .
, ~ ~ , , .;
8 3~
audio subcarrier signals towards providing a combined audio
signal output and a video signal combiner electrically connected
to the audio subcarrier signal combiner and the video level
control for combining and amplifying the input signals towards
generating a combined subcarrier audio/video signal.
Additionally, preferably provided is a video clamp electrically
connected to the video signal combiner.
- The IF signal processor preferably comprises a voltage
controlled oscillator, IF signal processor bandpass filter,
variable attenuator, second IF signal processor lowpass filter
all connected in series to the combiner, the output of which
services to frequency modulate the voltage controlled oscillator
thereby generating a modulated audio/video signal.
The RF amplifier of the present invention preferably
comprises an RF section bandpass filter electrically connected to
the up converter, RF section matching pad electrically connected
to the RF section bandpass filter, first RF section amplifier
electrically connected to the RF section matching pad, second RF
section amplifier electrically connected to the first RF section
amplifier and an RF section lowpass filter electrically connected
to the second RF section matching amplifier.
In the preferred embodiment of the invention the
receiver front end comprises a first low noise input amplifier,
an input bandpass filter and low noise high gain input amplifier
all connected in series with one another where the receiver front
end serves to amplify and filter the received RF signal.
~ he IF signal processor of the pre9ent invention
preferably comprises an AGC amplifier, first receiver IF signal
processor amplifier, AGC buffer, AGC detector and second IF
signal processor amplifier all connected in series.
Moreover, in the preferred embodiment of the invention
includes a stereo audio signal demodulator which comprises
demodulator buffer connected to the PLL detector, left and right
channel subcarrier demodulator for separately demodulating the
left and right channel audio signals each generating a baseband
` 11
' ' ' ' ' " ` ' . ' ' ' " . . ' ' .
', ' " " ' . ~` ~'"'`'"''. ' `' ' ;'" ~ .
~3383~
audio signal output and left and right channel de-emphasis
network electrically connected to the respective left and right
channel subcarrier demodulators serving to provide and de-
emphasized baseband left and right channel audio signal output.
The baseband video signal generator of the present
invention preferably comprises receiver video level control,
first video generator amplifier, video generator lowpass filter,
first video generator buffer, video generator de-emphasis
network, second video generator amplifier and second generator
buffer electrically connected in series to the PLL detector and
serving to provide a baseband video output signal.
The video signal modulator of the present invention
comprises an audio signal combiner electrically connected to the
stereo signal demodulator for combining the left and right
channel output signals towards creating a mono audio signal, a
video signal amplifier electrically connected to the baseband
video signal generator, and an audio/video signal modulator
electrically connected to the audio signal combiner and the video
signal amplifier towards providing a composite mono audio/video
signal modulated on a particular television channel. Further
provided is a video signal lowpass filter and video signal
attenuator connected in series to the audio/video modulator the
output of which is provided on a modulated composite audio/video
signal output connector.
In the preferred embodiment of the invention, the
remote control transmitter transmits said remote control co~mand
signals on an RF carrier of 500MHz, though another legally
allowed frequenay may be used. The remote control command
signals are generated by the remote control transmitter which
includes a push-button matrix keyboard for entering such
commands. The command are received by the remote control command
signal receiver comprises four gain blocks tuned to 50aMHz.
In the preferred embodiment of the invention the IR
remote control signal transmitter comprises a plurality of infra-
12
.
.. ; ,,~ .. ..
2033835
red emitting LEDs and the IR command signal receiver comprises ainfra-red sensor diode.
.
1~
i~
13
'1
2~33~3~
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 of the drawings is a pictorial representation of the
transmitter means, receiver means and remote control extender
means comprising the present convention together with the video
source for transmission (VCR) and the remote television;
Fig. 2 of the drawings is a block diagram illustrating the
functional modules of the transmitter means comprising the
present invention;
Fig. 3 of the drawings is a schematic circuit diagram
illustrating the baseband stereo audio signal input means,
baseband video signal input means, video processor means,
subcarrier modulator means and combiner means of the transmitter
means of the present invention;
Fig. 4 of the drawings is a schematic circuit diagram
illustrating the IF signal proce6sor means and up converter means
of the transmitter means of the present invention;
Fig. 5 of the drawings is a schematic circuit diagram
illustrating the RF amplifier means and transmitter antenna means
of the transmitter means of the present invention;
Fig. 6 of the drawings is a schematic circuit diagram of the
power supply circuitry for the transmitter means and the remote
control receiver means of the present invention;
Fig. 7 of the drawings is a block diagram illustration of
the functional modules of the remote control extender means of
the present invention comprising a handheld RF remote control
transmitter means and remote control receiver means;
Fig. 8 of the drawings is a floor chart diagram of the logic
operation of the handheld RF remote control transmitter means and
remote control receiver means of the remote control extender
means of the present invention;
14
.,, ,. ,, . , .~ .
3~
Fig. g of the drawings is a schematic circl~it diagram
illustrating the controller means of the remote control receiver
means of the remote control extender means of present invention;
Fig. 10 of the drawings is a schematic circuit diagram of
the IR transmitter means and the LED display means of the remote
control receiver means of the present invention;
Fig. 11 of the drawings is a schematic circuit diagram
illustrating the IR receiver means and IR detector means of the
present invention;
Fig. 12 of the drawings is a schematic circuit diagram
illustrating the RF receiver means of the remote control receiver
means of the present invention;
Fig. 13 of the drawings is a schematic circuit diagram
illustrating the RF detector means of the remote control means of
the present invention;
Fig. 14 of the drawings is a schematic circuit diagram
illustrating miscellaneous jumper configurations and capacitance
connections of the remote control means of the present invention;
Fig. 15 of the drawings is a bloc~ diagram illustrating the
functional modules of the receiver means comprising the present
invention;
Fig. 16 of the drawings is a schematic circuit diagram
illustrating the receiver antenna means, receiver front end means
and down converter means of the receiver means of the present
invention;
Fig. 17 of the drawings i~ a schematic circuit diagram
~' illustrating the receiver IF signal processor means of the
,j receiver means of the present invention;
Fig. 18 of the drawings is a schematic circuit diagram
illustrating the PLL detector means and stereo audio signal
- 15
-: .: :,
` ~' .
, , .
2~33~3~
demodulator means of the receiver means of the present invention;
Fig. 19 of the drawings is a schematic circuit diagram
illustrating the baseband video signal generator means and the
audio/video signal modulator means of the receiver means of the
present invention;
Fig. 20 of the drawings is a schematic circuit diagram of
the power supply circuitry for the receiver means of the present
invention.
16
: . , : .,; . :,. . :
. :~ , :., ~ ,.: . ..
203~83~
DETAILED DESCRIPTION OF THE DRAWINGS
While this invention is susceptible of embodiment in
many different forms, there are shown in the drawings and will
herein be described in detail a specific embodiment, with the
understanding that the present disclosure is to be considered as
an exe~plification of the principals of the invention and is not
intended to limit the invention to the embodiment illustrated.
Fig. 1 of the drawings is a pictorial representation of
the various elements which comprise the present invention 10,
namely, transmitter base unit 11, receiver unit 12, RF remote
control transmitter 13 and RF remote control receiver.
Additionally, external audio/video signal source 14 which
supplies the audio/video signal to be transmitted is illustrated
as a VCR together with remote television 15 which in this
configuration will display the transmitted audio/video signal.
Audio/Video signal source 14 is shown electrically connected to
transmitter base unit 11 via cable 16. Receiver unit 12 is
likewise shown electrically connected to remote television 15 via
cable 17. In a typical situation, audio/video signal source 14
and transmitter base unit 11 are positioned by the user at a
first location. Remote television 15 is typically located at a
second location remote from the first location. In operation,
audio/video signal source 14 provides a baseband stereo
audio/video signal output on cable 16 to transmitter base unit 11
which after processing FM modulates the stereo audio/video signal
and transmits the signal on an RF carrier which i~ received at
the remote second location by receiver unit 12. Receiver unit 12
in turn regenerates the original stereo audio/video signals and
provides baseband stereo audio/video signals on cable 17 to
remote television 15. In addition, receiver unit 12 is capable
of providing a mono audio/video signal modulated at either
channel 3 or channel 4 which may be received by the antenna
inputs of remote television 15.
In order to permit the user to actuate the remote
17
.
~33~3~
control functi~ns of audio/video signal source 14 from the remote
second location handheld RF remote control 13 as provided.
Handheld RF remote control transmitter 13 replaces the standard
remote control unit provided with video source 14, typically an
infra-red (IR) based device. Handheld remote control transmitter
13 is shown incorporating a matrix key pad, a mode select switch
(which permits the user to selectively control up to four (4)
separate remote audio/video signal sources 14), as well as a
"send" indicator which comprises an LED which notifies the user
that the handheld RF remote control transmitter 13 is operating
when the key pad is pressed. The key pad is shown comprising a
plurality of buttons corresponding to those found on typical
standard remote control devices and may provide for example,
volume control, channel control and direct channel entry
control.
Fig. 2 of the drawings is a block diagram illustrating
the functional modules of the transmitter 11 of the present
wireless stereo audio/video signal transmitter and receiver
system apparatus with remote control extender capability 10.
8aseband video signal input connector 21 comprises a connection
point for connecting the external baseband video signal to
transmitter 11. Baseband video signal output connector 22 is
shown electrically connected to buffer 23 which is in turn shown
electrically connected to baseband video signal input connector
21. Baseband video input signal connector 21 is thus fed into
buffer 23, the output of which i6 the loop-through baseband video
signal which permits connection to other electronic deViCes 9Uch
as additional VCR's or monitors or the like which may use the
baseband video input signal simultaneously with the present
invention. Baseband video signal input connectors 21 and
baseband video output connector 22 are both preferably RCA type
connectors.
Baseband video signal input connector 21 is shown
connected to the video processor section of the present
~,
18
`'
~ . , ~
2~3383~
transmitter. The baseband video signal passes through buffer 24,
lowpass filter 25, buffer 26 and video pre-emphasis network 27.
Lowpass filter 25 is a 4.5 MHz lowpass filter. Video pre-
emphasis network 27 follows the CCITT 405A specification. After
pre-emphasis, the video signal is amplified by amplifier 28 and
then passes through trap 29. Trap 29 is a 5.5 MHz trap which
serves to remove any video information at 5.5 MHZ that lowpass
filter 25 has failed to remove. After trap 29, the baseband
video signal is then buffered by buffer 30 after which the signal
passes through video level control 43 shown comprising a variable
resistor.
Baseband audio signal input connectors 31 and 33
provide a connection point at which an external baseband stereo
audio signal comprising left and right channels may be connected
to transmitter 11. As illustrated, the left channel is connected
to connector 31 and the right channel is connected to connector
33. A direct high impedance loop is associated with both
connectors 31 and 33 towards providing left and right baseband
audio signal outputs on connectors 32 and 34 respectively.
Connectors 31 through 34 preferably comprise RCA type connectors.
The left and right audio channel signals are separately
pre-emphasized by 75 microsecond pre-emphasizers 35 and 36,
respectively which form the initial state of the subcarrier
modulator section. The left channel audio signal is frequency
modulated onto a 5.5 MHZ subcarrier by subcarrier modulator 37
and the right channel audio signal is frequency modulated on a
6.5 MHz subcarrier by ~ubcarrier modulator 38. The le~t and
right channel subcarrier signals are then each buffered
separately by buffers 39 and 40, respectively, and are shown
combined with one another through an active audio signal
combiner/amplifier 41.
The output of audio signal combiner/amplifier 41
comprising the combined left and right channel subcarrier signals
is combined with the output of video level control 43 by
video/subcarrier combiner 42 the output of which is shown passing
19
:'
~33835
through video clamp 44. The IF section of the transmitter unit
follows. After the audio and video signals are co~bined by
video/subcarrier combiner 42, the combined signal is shown
passing to voltage controlled oscillator (VCo) 45. VCO 45
possesses a center frequency of 251.5 MHz wherein the combined
video/subcarrier signal serves to frequency modulate VCo 45.
From the output of VCO 45, the signal is shown being fed through
an elliptic bandpass filter 46 having a centex frequency of 252
MHz and possesses a bandwidth of 49 MHz. The output of bandpass
filter 46 is shown connected to variable attenuator 47 which is
controlled by RF level control 48. The signal thereafter passes
to lowpass filter 49, a four pole lowpass filter with a cutoff
freguency of 300 NHz.
The output of lowpass filter 49 is shown passing to up
converter 50 a NEC uPC1685 type device. Up converter 50 is
configured to have a fixed LO frequency of 665 MHz which is mixed
with the IF signal input centered at 251.5 MHz towards producing
RF signal at 916.5 NHz.
The output of up converter 50 then passes to the RF
amplifier section of the transmitter. As shown, the RF signal is
fed into a three pole bandpass filter 51 which is centered at
916.5 NHz and has a bandwidth of 15 MHz. Bandpass filter 51
output is fed to resistive pad 52 having a 3dB attenuation. The
signal is then shown fed to a hybrid amplifier 53 providing
approximately 18 dB gain. The signal thereafter is shown being
fed into amplifier 54 which provides 13 dB of gain and thcn into
amplifier 55 which provides an additional 13 dB of gain. The
output of amplifier 55 i5 shown connected to lowpass filter 56 a
three pole lowpass filter with a cutoff frequency of 1 GHz.
The filter 56 output is shown connected to balun 57
which in turn is connected to dipole antenna 58 towards
transmitting the modulated RF audio/video signal.
Fig. 3 of the drawings is a schematic circuit diagram
illustrating the baseband video signal input means 210, video
. ,
~ 20
: ,
! ' :' ' . ~ '
' " ~' "' , '~' . :
': . ' ' ';' .: . ' ' ' .
'" ,~ '' '` ............ '~
2~133~35
processor means 220, basaband stereo audio signal input means
230, subcarrier modulator means 240 and combiner means 250.
The baseband video signal input means 210 is shown
comprising external connectors 21 and 22. As illustrated, the
baseband video input signal connected to video input connector 21
passes through buffer 23 onto video output connector 22.
Video processor means 220 is shown comprising buffer 24
connected in series with lowpass filter 25. As designed, lowpass
filter 25 is effective at trapping signals at 6.5 MNæ but may be
less effective at trapping signals at 5.5 MHz. Video processor
means 220 further includes the series connection of buffer 26,
video pre-emphasis network 27, amplifier 28 (shown comprising a
two stage transistor amplifier) and trap 29. As illustrated an
designed, trap 29 serves to trap 5.5 MHz signals which may pass
through lowpass filter 25. The output of trap 29 passes through
buffer 30 and onto video level control 43 shown comprising a
variable lK resistor.
Baseband stereo audio signal input means 230 is shown
comprising left audio channel input connector 31, right audio
channel input connector 33, left audio channel output connector
32 and right audio channel output connector 34. As illustrated,
the audio channel inputs 31 and 33 are passed through a direct
high impedance loop to output connectors 32 and 34, respectively.
Connectors 31 through 34 preferably comprise RCA type connectors.
AB illustrated, both the left channel audio signal and right
channel audio signal pass through circuits which are identical
except for the fact that the left audio channel signal ls
frequency modulated onto a 5.5 MHz subcarrier by subcarrier
modulator 37 and the right audio channel signal is modulated onto
a 6.5 MHz subcarrier by subcarrier modulator 38. As shown,
subcarrier modulator 37 and 38 comprise LA7053 type IC devices.
The left and right aubcarrier signals are shown buffered by
buffers 39 and 40.
The left and right channel subcarrier signals are
combined through an audio combiner 41 an active
. I .
~ 21
'`
~ " , . ,., : , : ;
203383~
combiner/amplifier comprising a type 2N3904 device.
The video/subcarrier combiner 42 is shown formed by a
combination emitter follower buffer and constant current source
each composed of a type 2N3904 transi~tor device. The low
impedance output of video/subcarrier combiner 42 is shown passing
through video clamp 44 which is based upon a type lN4148 diode
device. Video clamp 44 holds the DC level of the signal constant
regardless of the average picture level (APL) and serves to keep
the VC0 45 centered.
Fig. 4 of the drawings is a schematic circuit diagram
illustrating IF signal processor 260 and up converter 270. IF
signal processor 260 is shown including voltage controlled
oscillator (VCo) 45 which has a center frequency of 251.5 MHz.
The combined video/subcarrier signal serves to frequency modulate
VC0 45 to a maximum peak to peak deviation of approximately 5
MHz. VC0 45 is shown including free running oscillator operating
at 25}.5 MHz and based upon a BFR92A transistor.
The output of VC0 45 is fed through an elliptic
bandpass filter 46 having a center frequency of 252 NHz and a
bandwidth of 40 NHz. The output of bandpass filter 46 is shown
connected to a PIN diode attenuator 47 which has a control range
of +/- 5dB on the IF signal at 252 MHz. Control is shown
accomplished by variable resistor 48. RF level control is
provided by the combination of variable resistor 48 and the type
HP3080 diode 47 together with flanking RC networks. The output
of attenuator 47 is shown passing through a four pole lowpass
filter 49 whiah has a cutoff frequency of 300 MHz.
Up converter section 270 is shown prlncipally
comprising up converter 50 an NEC uPC1695 device togather with
support componentry. Up converter 50 is shown configured to have
a fixed L0 frequency OL 665 MHz which when mixed with the
incoming IF signal centered at 251.5 MHz serves to produce an RF
signal at 916.5 MHz.
The RF output signal of up converter 50 is shown
22
. . .
. .
.. : ~ : :: . " :
`' ' ' ' ~`' ~` :
.
2~3~35
connected to a three pole bandpass filter 51. Bandpass filter 51
is centered at 916.5 MHz and has a bandwidth of 15 MHz. As
illustrated, filter 51 is formed by three tuned, coupled, short
circuited microstrip line sections. The output of filter 51 is
fed into a resistive PAD 52 having a 3dB attenuation.
Fig. 5 of the drawings is a schematic circuit diagram
illustrating the RF amplifier 280. The output of PAD 52 is shown
connected to amplifier 53 which as illustrated is a hybrid
amplifier having approximately 18dB gain. The signal is then
shown fed into two consecutive transistor amplifier stages,
amplifiers 54 and 55. Both amplifiers are identical in design
and are built around the NEC NE85639 RF transistor. Amplifiers
54 and 55 each provide a gain of 13 dB. The output of amplifier
55 is fed into a three pole lowpass filter 56 with a cutoff
frequency of 1 GHz and is shown comprising a microstrip line
device. The output of Filter 56 is connected to dipole antenna
58 a 1/2 wave antenna via a 3/4 wave section of RG178 coax cable.
The coax cable acts as both a balun S7 for the antenna as well as
part of the antenna matching network.
Fig. 6 of the drawings illustrates the schematic
diagram for the power supply for the transmitter 11. Transmitter
11 is designed to accept a filtered unregulated DC input which
may be provided from an external power adapter. The loaded DC
voltage from such an adapter is approximately 14.5 Vdc. The
unregulated voltage is internally regulated to +12 volts and to
+5 volts. The unregulated voltage is also provided on a four pin
connector to supply power to the remote control receiver which i~
housed withln the same cabinet as the transmitter 11. The
operation of power supply illustrated in Fig. 6 of the drawings
~I should be readily discernible to those skilled in the art.
Fig. 7 of the drawings is a block diagram illustration
of the functional modules of the remote control transmitter and
remote control receiver of the present wireless stereo
audio/video signal transmitter and receiver system apparatus With
remote control extender capability. Hand-held remote control
23
- : - : : ~. . . : :
2!~3383~
transmitter 13 is shown comprising keyboard 60 which is
electrically connected to encoder 61 which is in turn
electrically connected to RF transmitter 62. Keyboard 60 is
preferably a matrix keypad which resembles the standard infrared
(IR) remote control device typically supplied with a VCR and the
like and possesses prelabled buttons corresponding to such
functions as volume, channel and the like. Encoder 61 comprises
a combined keypad scanner and key code encoder which translate
actuation of the keyboard 60 into a key code wherein different
key code sequences are ~enerated depending upon which key of the
keyboard 60 is depressed. RF transmitter 62 serves to amplitude
modulate the key code data on an RF carrier centered at 500 MHz.
As contemplated, handheld RF remote control transmitter
13 may include a device select switch that allows selection
between one of four different remote controls whose key codes
have been programmed into the remote control receiver.
As an overview of the interaction between handheld RF
remote control transmitter 13 and remote control receiver 19, the
following is provided. The present apparatus is operated by
first "teaching" the remote control receiver 19 the IR key codes
for the various IR remote controls 18 associated with the
external audio/video signal source 14 and then "assigning" the
key codes to the corresponding key codes transmitted from the
handheld RF remote control transmitter 13.
The "teaching" is accomplished by placing remote
control receiver 19 into a "learn" mode via switch provided. In
the "learn" mode the user i5 prompted by LED indicators to
slmultaneous press a key on IR remote control 18 and a
corresponding key on handheld RF remote control transmitter 13 to
which the user wishes to assign the particular key function.
This process is repeated until all the keys are entered.
I Thereafter, remote control receiver 19 i9 switched back to a
! "normal" mode. once taught, remote control receiver 19 will
regenerate and emit the identical IR code it has learned when it
24
: . . ~ :: ' . :
` ! ` ; ` . ~
.
. , :~ ~:, ,
203383~
receives the corresponding RF key code transmitted by handheld
remote control RF transmitter 13.
Remote control receiver 19 contains RF receiver 63
which receives the RF signal transmitted from handheld RF remote
control transmitter 13 at 500 MHz. The output of RF receiver 63
is shown connected to RF detector 64 which recovers the amplitude
modulated data encoded by handheld RF remote control transmitter
13. The recovered key code data is shown connected to controller
65 a microprocessor based device. IR transmitter 66 i shown
electrically connected to controller 65 and serves to generate
the IR signal in response to handheld RF remote control
transmitter 13 which IR signal services to actuate the various
functions of controlled device 14.
When in the "learn" mode, controller 65 reads the IR
code data generated by standard remote control 18 and stores the
IR code in controller memory. It simultaneously stores in memory
the corresponding RF remote control transmitter key code. When
in the "normal" mode, the contro}ler 65 detects the RF key code
transmitted from handheld RF remote control transmitter 13 and
looks into its memory for the corresponding IR code. This IR
code is then retrieved and sent out through an array of IR
emitter diodes. IR receiver 67 is shown and is provided for
receiving the IR signal from the standard remote control 18. IR
detector 68 serves to detect the information key code transmitted
and feeds the key code data to controller 65 as illustrated in
the "learn" mode.
Fig~ 8 of the drawings is a flow chart diagram of the
logical operation per$ormed by handheld RF remote control
transmitter 13 and remote control receiver l9 of the present
invention. The logic of this chart and its operation should be
readily discernible to those skilled in the art having before
them the present disclosure and description of operation.
Fig. 9 of the drawings is a schematic circuit diagram
illustratins the controller 65 of remote control receiver 19.
Controller 65 is based primarily upon a type M50747 device a
,~: : : ,~ - : :
2~33835
"microprocessor~ on a chip incorporating a microprocessor, RAM
and ROM.
Fig. 10 of the drawings illustrates IR transmitter 66
and the LED display of remote control receiver 19 of the present
invention. IR transmitter 66 is shown comprising a plurality of
infrared emitting LED's. LED's 80, 81 and 82 are visible light
T.~D~5 and serve to prompt the user in the operation of remote
control receiver 19.
Fig. 11 of the drawings is a schematic circuit diagram
of IR receiver 67 and IR detector 68 of the remote control
receiver 19. IR receiver 67 is based upon a type 8406HONEY
infrared diode which serves to receive the infrared key codes
transmitted by the standard remote control 18. The output of IR
detector 68 comprises the key code sequence corresponding to the
particular key depressed upon standard remote control 18.
Fig. 12 of the drawings is a schematic circuit diagram
illustrating RF receiver 63 of the remote control receiver 19.
The RF receiver 63 is shown comprising four gain blocks tuned to
500 MHz, the frequency at which the handheld RF remote control
transmitter operates. The maximum field strength allowed for
this type of operation is 12.5 mV/m at three meters. With this
field strength, the resulting received signal level at the remote
control receiver is less than -70dBm when operating at a distance
of 100 feet. The RF receiver 63 is thus designed to be very
sensitive and may alternatively comprise a super-regenerative
type receiver.
Fig. 13 of the drawings illustrates RF detector 64 of
the remote control receiver 19. As previously described, power
for the remote control receiver 19 is provided by the power
supply circuitry contained within transmitter 11. Fig. 14 of the
drawings illustrates miscellaneous capacitance connections
associated with controller 65.
Fig. 15 of the drawings is a block diagram
illustrating the functional modules of the receiver 12 of the
26
- , , ~
:,
.. , ;~ . .
- ~
.
,~: . .~ - , :
.: . . :
,
present wireless stereo audio/video signal transmitter and
receiver system apparatus with remote control extender
capability. Receiver 12 uses an external UHF loop antenna 90
that is shown connected to the RF input section via a 3/4 wave
section of RG178 coaxial cable which serves as balun 91 as well
as part of the matching network for the antenna.
From the output of balun 91, the received RF signal is
shown coupled to low noise amplifier 92 built around the NEC
NE85639 RF transistor. The amplifier 92 has a noise figure of
approximately 2.OdB and thus is the dominant factor in
determining the overall receiver noise figure. From the output
of low noise amplifier 92, the RF signal is fed through a two
pole bandpass filter 93 centered at 916.5 MHz having a bandwidth
of 20 MHz. The filter output is shown fed to a second low noise
amplifier 94 identical in configuration to first low noise
amplifier 92.
The output of low noise amplifier 94 is shown connected
to down converter 95 which is formed by an NEC uPC1685 type
device configured to have variable LO frequency centered at 846.5
MHZ with a control range of +/-15 MHz. The resulting IF signal
from mixing the RF signal at 916.5 MHz with the LO signal at
846.5 M~z is an IF signal at 70 MHz.
Fro~ the IF signal output of down converter 95 tha
signal is applied to the input of AGC amplifier 96 which provides
a maximum of 25 dB of gain at 70 MHz. The output of AGC
amplifier 96 is shown connected to IF amplifier 97 which provides
a fixed gain of 25 d~, the output of which is conneated to buffer
98 and in turn to bandpass filter 101 a three pole bandpass
filter centered at 70 MHz having a bandwidth of 20 MHz.
The signal from buffer 98 is shown also connected to
the input RF detector 99. The output of RF detector 99 is
a dc level proportional to the RF carrier amplitude of the input
signal and is fed to the AGC control of AGC amplifier 96 via a
control amplifier lOO. The AGC loop defined by amplifiers 96 and
97, buffer 98, detector 99 and amplifier 100 serves ta keep the
27
'~` , . ' ' ' '. ' .' ' :
. ' ~ ' ' '
' ' ' ' ~ : ',
~3383~
RF level input to PLL detector 102 constant at -14 dBm.
The output of bandpass filter 101 is shown fed to the
input of PLL detector 102. The output of PLL detector 102 is a
combined pre-emphasized video/audio subcarrier signal similar to
that which was fed to the input of VC0 45 in transmitter 11.
From the PLL 102 detector output, the signal is shown
splitting into three separate signal paths. The first path is to
the AFC control amplifier 104. The AFC control signal derived
from the output of PLL detector 102 acts to maintain a stable IF
frcquency. The second path from PLL detector 102 is to buffer
105 which forms the initial stage of the subcarrier demodulator
section of the receiver 12. The third signal path is to a video
level controlled potentiometer 115 forming the initial part of
the baseband video signal generator.
The stereo audio signal demodulator section begins with
buffer 105 the output of which is shown connected to two
subcarrier bandpass filters. Filter 107 is centered at 5.5 MHz
for the left audio channel subcarrier and bandpass filter 106 is
centered at 6.5 MHz for the right channel subcarrier signal. The
outputs of filters 106 and 107 are shown connected to subcarrier
demodulators 108 and 109, respectively, where subcarrier
demodulators 108 and 109 are identical except that demodulator
108 is tuned for 6.5 MHz while demodulator 109 is tuned for 5.5
NHz corresponding to the right and left channels respectively.
The outputs of demodulators 108 and 109 are pre-emphasized
baseband audio aign41s are thus are shown connected to audlo de-
empha~izers 1}0 and 111, respectively. The de-emphasized left
and right audio signals are provided to the user through baseband
audio output connectors 113 and 114 corresponding to left and
right channels respectively and preferably comprise RCA type
connectors.
The output of video level control 115 is shown
connected to a amplifier 116 and then to a three pole lowpass
filter 117 having a cutoff of 4.5 MHz. From the output lowpass
28
- - . .
,
filter 117, the signal is buffered by buffer 118 and is shown fed
to the input of a video de-emphasis network 119. The video de-
emphasis network 119 follows the CCITT 405A specification. From
the output of de-emphasis network 119, the signal is fed to
amplifier 120 and then to buffer 121 which provides as an output
a baseband video signal which is provided to the user through an
RCA type connector 122. The video output level is lVpp.
Audio signal combiner 112 is shown connected to the
outputs of audio de-emphasizers 110 and 111 and serves to
combined the left and right channel audio signals into a single
mono signal. The output of amplifier 120 is shown connected to
amplifier 123. The combined mono audio signal and the baseband
video output of amplifier 123 are shown connected to modulator
124 which is a self contained AM TV modulator IC type MC1374 and
serves to modulate the two input signals to an AM double side
band format with a frequency modulated audio subcarrier at 4.5
MHz. Modulator 124 is selectable between television channel 3
and television channel 4 having carrier frequencies of 61.25 MHz
and 67.25 MHz respectively. The output of modulator 124 is shown
connected to a five pole lowpass filter 125 having a cutoff
frequency of 70 MMz. From filter 125, the signal is fed to 20dB
attenuator 126 and lastly to composite modulated signal output
connector 127 where the RF output level is -42dBm.
Receiver front end 310 is illustrated in schematic
representation in Fig. 16 of the drawings. Receiver front end
310 accepts a RF input from an external UHF loop antenna which is
connected via a 3/4 wave section of RG178 coaxial cables serving
as a balun, (not shown). From the output of the balun, the
signal is coupled to an antenna matahing component network formed
by the capacitor and microstrip line device illustrated. The
signal is then fed to the input of a low noise transistor
amplifier 92 built around the NEC NE85639 RF transistor. This
amplifier has a noise figure of approximately 2.OdB and is the
dominant factor in determining the overall receiver noise figure.
The output of low noise amplifier 92 is shown connected to a two
29
,
- . : . - . : .
. .
, ~ ~, ; .... : ''
2~3383~
pole bandpass filter 93. Filter 93 is centered at 916.5 MH7 and
has a bandwidth of 20 MHz, and is formed by two tuned coupled
short circuited microstrip line sections. The output of filter
93 is fed to a second low noise amplifier 94 which is identical
in configuration to low noise amplifier 92.
Down converter section 320 is shown formed principally
by an NEC uPC1685 type device. Down converter 95 is configured
to have a variable LO frequency centered at 846.5 MHZ with a
control range of +/-15 MHz. The resulting IF output from mixing
the inpUt RF signal at 916.5 MHz with the LO signal at 846.5 MHz
i8 an IF signal at 70 MHz. The frequency adjustment is
accomplished via a DC voltage applied to a UHF varactor diode in
the LO tank circuit as illustrated. This adjustment is provided
to compensate for component tolerances. In addition to the
frequency adjustment, a second varactor is used in the LO tank
circuit to provide a control means for the AFC signal. The AFC
control signal acts to maintain a stable IF frequency over a
range of +/-5 MHz. AFC control section 330 is illustrated in
`Fig. 16 and comprises an AFC control amplifier formed by two
LM358 type devices the input of which is derived from the output
of the PLL detector 102.
Fig. 17 of the drawings is a schematic circuit diagram
of receiver IF signal processor section 340 of receiver 12. As
illustrated, the input to receiver IF signal processor 340 comes
from the output of down converter 95. The IF output of down
converter 95 is applied to the input of an AGC (Automatic Gain
Control) amplifier 96 which is formed by an MC1350P device and
provides 25dB of gain at 70 MHz. Amplifier 96 can provide up to
60dB of AGC through a DC control signal applied to PIN 5 as
illustrated.
The output of AGC amplifier 96 is shown connected to IF
amplifier 97 which is an amplifier chain made up of three
cascaded common emitter amplifiers each type 2N3904 devices the
output of which is connected to buffer 98 an emitter follower
,:
.
~3~3~
buffer. From the output of buffer 98, the signal is fed to the
input o~ a three pole bandpass filter 101 which is centered at 70
MHz and has a bandwidth of 20 MHz.
The signal output from buffer 98 is also fed to the
input of an RF detector 99 which is formed by a 100 pico farad
capacitor together with a HP2800 device. The output of PF
detector 99, which is dc level proportional to the RF carrier
amplitude, is fed to PIN S of AGC amplifier 96 via a control
amplifier 100 which is formed by two LN358 devices. The action
of this AGC loop serve~ to keep the RF level at the input to PLL
detector 102 constant at -14 dBm.
Fig. 18 of the drawings illustrates a schematic circuit
diagram for PLL detector section 350 and stereo audio signal
demodulator section 360. The output of the 70 MHz bandpass
filter 101 is shown connected to the input of a PLL detector 102.
The output of PLL detector 102 is a combined pre-emphasized
video/audio subcarrier signal similar to what was fed to the
input of VC0 45 of transmitter 11. The output of PLL detector
102 on PIN 14 is a demodulated output comprising pre-emphasized
baseband audio signals combined and baseband video. From the
output of PLL detector 102, the signal splits off into three
separate signal paths. The first path is to the AFC control
amplifier section 330. The second path is to buffer 105 forming
the initial stage of the stereo audio signal demodulator section
360. The third path is to video level control potentiometer llS
forming the initial stage of the baseband video signal generator
370.
From the output of PLL detector 102, the signal passes
to buffer lOS the output of which splits and is applied to the
input of two subcarrier bandpass filters 106 and 107. 3andpass
filter 106 is centered at 6.5 MHz for the right channel
subcarrier and bandpass filter 107 is centered at 5.5 NHZ for the
left channel subcarrier. The outputs of bandpass filters 106 and
107 are applied to two separate subcarrier demodulators 108 and
109 respectively for the right and left channels respectively.
31
,
~; -
,- -, .. ~ . ' :.. . ' ~ :.. -:
-- 2033~3~
The two subcarrier demodulators 108 and 109 are identical except
that one is tuned for 6.5 MHz and the other is tuned for 5.5 MHz.
The output from the subcarrier demodulators 108 and 109
is pre-emphasized baseband audio. The baseband audio signals are
then de-emphasized through audio de-emphasizers 110 and 111 each
based upon an LM324 device. The de-emphasized left and right
audio signals are shown provided to the user through RCA
connectors 113 and 114. The audio output level is lVpp into a
600 Ohm load from a 600 Ohm source.
Further shown in Fig. 18 is audio signal combiner 112
the inputs to which come from the outputs of de-emphasizers 110
and 111. Audio signal combiner 112 serves to combine the left
and right audio siqnals to form a mono audio signal used in the
channel 3/4 modulator 124.
Fig. 19 of the drawings is a schematic circuit diagram
illustrating the baseband video signal generator 370 and
audio/video signal modulator 380. The initial stage of the
baseband video signal generator 370 is formed by video level
control potentiometer 115 shown as a variable resistor. The
signal is then fed into two stage transistor amplifier 116 and
then to a three pole lowpass filter 117 having a cutoff of 4.5
NHz. From the output of lowpass filter 117, the signal is
buffered by buffer 118 and fed into the input of video de-
emphasis network 119 which follows the CCITT 405A specification.
The output of video de-emphasis network 119 is fed into two stage
amplifier 120 based upon the 2N3904 and 2N3906 transistors and
then onto a emitter follower buffer 121. The buffered baseband
video signal output is provided to the user through an RCA
connector 122. The video output level is lVpp.
Audio/video signal modulator 380 comprises a self
contained AN TV modulator 124 which accepts the combined audio
signal from the audio signal combiner 112 as well as the baseband
video output source which is shown tapped off amplifier 120 as
further amplified by amplifier 123. Modulator 124 modulates the
32
;J`'~
- : ~,
20~3~
input signals to an AM double side band format with a frequency
modulated audio subcarrier at 4.5 MHz. The video depth of
modulation is set at 87.5%. The channel selection is made via a
switchable DC voltage applied to a varactor diode shown in the
oscillator tank circuit. The channel 3 carrier frequency is
61.25 NHz and the channel 4 carrier frequency is 67.25 MHz. The
RF output of the modulator is fed to five pole lowpass filter 125
having a cutoff frequency of 70 MHz. From the filter output, the
signal is fed to 20dB attenuator 126 and then finally out to the
user via an "F" connector 127. The RF output level is -42d8m.
Fig. 20 of the drawings is the power supply circuitry
for the receiver 12 of the present invention lO. The operation
and function of which is readily discernible to those skilled in
the art.
The foregoing description and drawings merely explain
and illustrate the invention and the invention is not limited
thereto, except insofar as the appended claims are so limited and
those skilled in the art who have the disclosure before them will
be able to make modifications and variations therein without
departing from the scope of the invention.
:
,
