Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR CONTROLLING A TRANSMSSION SYSTEM, USE OF THIS
METHOD, TRANSMISSION SYSTEM, RECEIVING UNIT AND HEARING AID
The present invention relates to a method for
controlling a transmission system, further to an
application of the method, to a transmission system,
to a receiving unit and to a hearing device.
Miniaturized FM (frequency-modulated) transmission
systems have been used already for a considerable time
with hearing devices. Essentially the transmission
system consists of a microphone-fitted transmitter and a
receiver connected to the hearing device. It is
critically important that the receiver per se be as
compact and as lightweight as possible in order that the
unit consisting of receiver and hearing device be of a
size readily tolerated by its wearer.
A receiver of the cited kind is known from the US patent
5,734,976 and uses FM transmission wherein the carrier
frequency is set by a quartz crystal.
As a result this known state of the art incurs the
drawback that changing the carrier frequency, and hence
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the transmission channel, entails exchanging the quartz
crystal. Therefore, this system precludes rapidly
switching between different transmission channels.
Moreover the known system is a drawback for the hearing-
device manufacturer because a large number of quartz
crystals must be kept in stock in order to allow
switching between transmission channels in a reasonably
short time.
Accordingly, it is the object of the present invention
first to create a method allowing rapidly switching from
one transmission channel to another. At the same time,
the switchover between different transmission channels
shall not cause interferences in the audio signal.
According to the present invention, there is provided a
wireless transmission system comprising:
- a plurality of hearing devices, each hearing device
comprising a signal processing unit and an electro-
acoustic transducer, the signal processing unit
being operatively connected to the electro-acoustic
transducer,
- means for transmitting a plurality of audio signals
to the hearing devices, wherein each audio signal is
transmitted at a predefined carrier frequency,
- each hearing device further comprising means for
receiving of at least one of the plurality of audio
signals, said means for receiving at least one of
the plurality of audio signals being operatively
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connected to at least one of the signal processing unit and the electro-
acoustic transducer,
- means for remotely generating and wirelessly transmitting
configuration parameters to the hearing devices for configuring the
means for receiving of at least one of the plurality of audio signals,
- each hearing device further comprising means for receiving the
configuration parameters, said means for receiving the configuration
parameters being comprised in said means for receiving at least one of
the plurality of audios signals, and
- each hearing device further comprising means for tuning the means for
receiving at least one of the plurality of audio signals to an audio signal
according to the configuration parameters,
wherein the plurality of audio signals as well as the configuration parameters
are
transmitted wirelessly via independent transmission channels, whereby the
configuration parameters are transmitted at a predefined carrier frequency via
a
common transmission channel shared by all said means for remotely generating
and wirelessly transmitting configuration parameters and all said means for
receiving the configuration parameters.
According to the present invention, there is also provided a wireless
transmission system comprising:
- a plurality of hearing devices, each hearing device comprising a signal
processing unit and an electro-acoustic transducer, the signal
processing unit being operatively connected to the electro-acoustic
transducer,
- means for transmitting a plurality of audio signals to the hearing
devices, wherein each audio signal is transmitted at a predefined
carrier frequency,
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- each hearing device further comprising means for receiving at least
one of the plurality of audio signals, said means for receiving at least
one of the plurality of audio signals being detachably coupled to the at
least one haring device, ands said means for receiving at least one of
the plurality of audio signals being operatively connected to at least
one of the signal processing unit and the electro-acoustic transducer,
- means for remotely generating and wirelessly transmitting
configuration parameters to the hearing devices, for configuring the
means for receiving at least one of the plurality of audio signals,
- each hearing device further comprising means for receiving the
configuration parameters, said means for receiving configuration
parameters being comprised in said means for receiving at least one of
the plurality of audio signals, and
- each hearing device further comprising means for tuning the means for
receiving at least one of the plurality of audio signals to an audio signal
according to the configuration parameters,
wherein the plurality of audio signals as well as the configuration parameters
are
transmitted wirelessly via independent transmission channels, whereby the
configuration parameters are transmitted at a predefined carrier frequency via
a
common transmission channel shared by all said means for remotely generating
and wirelessly transmitting configuration parameters and all said means for
receiving the configuration parameters..
The invention offers the following advantages: Problem-
free and interference-less switching from a signal which
is modulated in amplitude, frequency and/or phase to
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another signal can be implemented by adjusting
configuration parameters in the receiving unit. Because
of the low transmission rate, the control channel may be
of low power compared with the information channel. As a
result, the control channel does not require a special
authorization procedure and the required' components can
be put together in exceedingly economical manner.
Preferably, by using a synthesizer in the receiving unit
to generate the frequencies required to demodulate the
received signals, extremely rapid and flexible matching
to the employed carrier frequencies is made possible and
consequently rapid switching from one information channel
to another is assured.
The invention is elucidated in illustrative manner below
in relation to the attached drawings. It is shown in
Fig. 1, schematically, a transmission system according
to the present invention with a receiving unit
according to the present invention,
Fig. 2 a functional block diagram of the receiving unit
according to the present invention of Fig. 1,
and
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Fig. 3 a control unit used in the transmission system
of Fig. 1.
Fig. 1 schematically shows a transmission system
according to the present invention consisting of a set of
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components required according to application or mode of
operation.
Part of the transmission system are a transmitter Si
...
Sn and a receiving unit 1 which are connected by a
wireless link hereafter called the information channel
120. If, as in the present case, the signal being
transmitted is an audio signal, then this signal shall be
modulated at a carrier frequency in the transmitter Si
... Sn prior to transmission, for instance using known
amplitude, frequency and/or phase modulation. Obviously
depending on the transmission power being used and the
particular carrier frequency, the information channel 120
also is suitable for long-range transmission or
transmission through buildings. Known applicable
modulation procedures illustratively are described in
ELECTRONIC ENGINEERS' HANDBOOK (Donald Christansen, 4th
ed., McGraw-Hill, chapter 18).
The presence of n transmitters S1, ..., Sn indicates that
various audio signals to be transmitted are modulated at
different carrier frequencies so that different audio
signals can be received in one receiving zone provided
there be corresponding tuning to the particular carrier
frequency in the receiving unit 1. Conceivably however,
merely one transmitter is used instead of the n Si, ...,
Sn transmitters, where said single transmitter is fitted
with several, preferably n transmission channels. The
principle of the present invention also covers this
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embodiment of transmitter design. Either design shall be
implied hereafter where n transmitters Si, ..., Sn are
mentioned.
5 In order to tune the receiver 1 to one of the
transmitters S1, ..., Sn and hence to a particular audio
signal, the transmission system of the present invention
comprises a control channel 110, 111, 112, 113
transmitting configuration parameters corresponding to
the particular transmitter Si, ..., Sn to the receiving
unit 1. For this purpose the transmitters Si, ..., Sn
have access within themselves or in separate components
to corresponding means generating and transmitting the
configuration parameters. Illustratively, such means may
be selectively a control unit 102 and/or a remote control
107. Regarding the link - i.e. for the control channel -
between the receiving unit 1 and the control unit 102 or
remote control 107, they also are wireless and are
indicated by the reference signs 110 and 112,
respectively, in Fig. 1. If the transmitters Si, ..., Sn
themselves are fitted with corresponding means generating
and transmitting the configuration parameters, then said
parameters shall be transmitted through the control
channel 113 to the receiving unit 1. It is pointed out
that even though according to Fig. 1 various control
channels are conceivable (such as reference signs 110 to
113 in Fig. 1) as regards transmission principles they
are one and the same transmission channel because the
specifications of the latter, such as rate of
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transmission and carrier frequency, preferably remain
unchanged for one and the same transmission system.
In a preferred embodiment of the present invention,
frequency-shift keying (FSK) modulation is used in the
control channel, the transmission rate being 1,280 bits/s
and the channel center frequency being 40,960 kHz.
Switching or tuning to a specific carrier frequency and
hence to a given audio signal, is not initiated in the
receiving unit 1 per se in the present invention, but
instead and in preferred manner by using one of the
control channels 110, 112, 113. In the preferred
embodiment of the transmission system of the present
invention, the information channel 120 used by the audio
signal in no way shall transmit any other data. On the
one hand, this feature allows switching from one audio
signal to another without requiring manual adjustments in
the receiving unit 1. On the other hand, the receiving
unit 1 can be remote-controlled, allowing wide
applicability of the transmission system of the present
invention as discussed below.
Furthermore, a configuration unit 105 is provided in the
transmission system of the present invention enabling
again to configure/program the receiving unit 1 and any
further components connected to said receiving unit 1
through a wireless link 111 (control channel). Because,
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in the configuration phase, the receiving unit 1 can be
positioned near the configuration unit 105, comparatively
few demands are placed on the link 111, that is,
satisfactory data transmission can be carried out at low
transmitting power. This feature is especially critical
because, as shown in Fig. 1, the link 11 is bidirectional
and furthermore and in particular as regards a
miniaturized receiving unit 1, only very little energy is
available inside the receiving unit 1 in the sending
mode.
A computer unit 106, for instance a commercial PC, is
used as an input and processing accessory to program the
receiving unit 1. As a result, it is possible to manage
the entire transmission system, new program drivers in
particular being downloaded into the receiving unit 1.
By means of back-transmitting, it is possible for
instance to feed version data from the receiving unit 1
through the configuration unit 105 to the computing unit
106 where they shall be processed further.
As regards the application shown in Fig. 1, the receiving
unit 1 is detachably connected to a hearing device 100.
All functions relating to the wireless signal
transmission are implemented in the receiving unit 1.
Because of different requirements on the rate of signal
transmission and range of transmission when transmitting
audio signals and when transmitting control signals, the
receiving unit 1 is fitted with two antennas, namely an
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antenna A for audio signals, and a receiving coil of
substantially smaller dimensions for the control signals.
As shown by Fig. 1, the control unit 102 is connected, on
the one hand, to a loop antenna 101 and, on the other
hand, to an input/computing unit 103. Said unit 103 again
is used only for data input and preferably is in the form
of a commercial personal computer (PC), and in this case
communication between the control unit 102 and the
input/computing unit 103 takes place for instance through
a standardized Universal Serial Bus (USB).
Whereas the control unit 102 connected to the loop
antenna 101 is used to transmit low-power control signals
to the receiving unit 1, the remote control 107 is used
to transmit control signals over short distances, again
at low transmitting power. The various embodiments are
elucidated in the applications described below.
The main application of the present invention concerns a
transmission system in which the receiving unit 1 is
linked to a hearing device 100, and as a result the
potential users are not restricted to the hearing-
impaired but also cover people with normal hearing.
It is highly significant in the present invention that
the user of the hearing device 100, which is coupled to
the receiving unit 1 of the present invention, need not
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tune this device to a given channel, including a
particular carrier frequency, or ascertain which signal
processing is required in order to receive and hear the
desired audio signal, because these steps are implemented
by the receiving unit 1 which shall be configured by the
configuration parameters picked up by the receiving coil
15. The needed configuration parameters are transmitted
from the control unit 102, from the remote control 107 or
from one of the transmitters S1, ..., Sn directly through
a universal communications link, that is the control
channel 110 or 112 or 113 to the receiving unit 1,
without interfering with a transmitted audio signal. The
control channel 110 or 111 or 113 is operable only over
short distances and comprises its own modulation
procedure at a carrier frequency in agreement with
international standards. In Europe this is the EN 300
330 standard (Radio Equipment and Systems; short range
devices technical characteristic and test methods for
radio equipment in the range of 9 kHz to 25 MHZ and
inductive loop systems in the frequency range of 9 kHz to
MHZ) and in the USA it is the Code of Federal
Regulations standard 47 (Telecommunication FCC Part 15,
subpart C: Intentional Radiators) apply.
25 In a preferred embodiment of the present invention, the
following parameters are transmitted through the control
channel 110 or 111, or 113 :
- the carrier frequency of a desired audio signal;
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a switching signal to complete turn OFF the
receiving unit 1;
- a switching signal causing the received audio signal
to be superposed on a microphone signal within the
hearing device;
- a mute command to turn OFF the audio signal;
- a signal controlling the volume of the received
audio signal.
The receiving unit 1 is configured on the basis of all or
some configuration parameters exclusively transmitted
through the control channel 110 through 113.
As shown by Fig. 1, the control channel 110 through 113
is used in the following cases:
In the first place, by means of the remote control 107
operated by the user to control the receiving unit 1 in
the hearing device 100 of the transmission system of the
present invention.
In the second place, by means of the control unit 102
connected to the loop antenna 101, whereby each user,
i.e. this user's receiving unit 1 is provided with the
particular configuration parameters if within the
detection range of the loop antenna 101. One or more
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codes are assigned to each user so that the users may be
addressed singly or in groups. Such a transmission
system is used in particular in schools where all the
advantages of automatic adjustment will apply, in
particular the fact that knowledge of the transmission
channel (carrier frequency etc.) is not required.
Further applications are conceivable to assembly spaces,
for instance conference rooms, churches or railway
stations: As soon as such a space is being entered, the
hearing-device receiver is automatically tuned to
transmission channel of said assembly place.
Be it mentioned in this respect that in a further
embodiment, the hearing device is replaced with merely an
electro-acoustic transducer coupled to the receiver. In
this instance, the various functions offered by a hearing
device are not available.
In the third place, the control channel is used to
transmit data which shall be stored in a memory of the
receiver, that is, the receiver, i.e. its memory, can be
programmed through the control channel.
In a preferred embodiment of the invention, individual or
several transmitters Si through Sn are fitted with a
transmitter generating a control signal or they transmit
the configuration parameters. The transmitted
configuration parameters are code-enhanced and this code
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causes a specifically addressed receiving unit 1 to
configure according to the configuration parameters.
Fig. 2 is a functional block diagram of a receiving unit
1 of the present invention detachably connected in the
manner shown in Fig. 1 to a hearing device 100.
A frequency or phase modulated signal SIN is received by
an antenna A, and first is fed to a filter/amplifier unit
2 fitted with an externally connected adjusting unit 19
to tune to the desired frequency band. The output of the
filter/amplifier unit 2 is connected to the input of a
mixer 3. A second input of the mixer 3 is connected to
the output signal from a synthesizer 6 that shall be
discussed further below. A demodulator 4 is connected to
and follows the mixer 3 together with which it generates
a demodulated signal S which is fed to an amplifier 5
adjusted by an adjustment unit 7. The output signals Souti
and Soutz were matched in the amplifier 5 and are fed
either directly to a loudspeaker or to a hearing device
(omitted from Fig. 2).
In one embodiment variation of the receiving unit 1 of
the present invention, an I`S unit 13 is connected to the
amplifier 5. The 12S unit 13 is an interface to control a
digital 3-conductor bus. Reference is made in this
respect to applicant's international patent application
PCT/CH99/00009 with publication no. WO 99/13699. Said
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application is an integral part of the present one. The
I`S unit 13 comprises a digital output from which a
digital audio signal SDIGITAL is fed back for instance
directly to the hearing device 100 (Fig. 1).
Also an audio-frequency generator 14 is provided and
connected to the amplifier 5 generating a signal to be
superposed on the signal S. In this manner, a given state
of the receiving unit 1, for instance low battery-voltage
or setting at the standard carrier frequency, can be
acoustically communicated to the user. To receive
corresponding control signals, the audio-frequency
generator 14 is connected to the adjustment unit 7 which
shall be elucidated below.
The transceiver coil already discussed in relation to
Fig. 1 is denoted by 15 and receives the configuration
parameters through the so-called separate control
channel. To tune this transceiving coil 15 operating as
an antenna, a series capacitor 16 follows said coil and
preferably shall be variable. The transceiver coil 15 and
the capacitor 16 are connected to a transceiver 8 which
in turn is connected to the adjustment unit 7.
The adjustment unit 7 constitutes the real control center
of the receiving unit 1 and besides the already mentioned
components, namely the amplifier 5, the audio-frequency
generator 14 and transceiver 8, additionally controls the
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synthesizer 6 wherein the mixed frequencies used in the
mixer 3 are generated, and a monitoring unit 10
monitoring and optimizing the energy budget in the
receiving unit 1, as a result of which the longest
possible and most problem-free operation is assured.
The adjustment unit 7 assumes sequence control and
further data from a memory 11 connected through a bus
system to the adjustment unit 7. The memory 11 is non-
volatile and programmable, for instance an EEPROM
(electrically erasable programmable read-only memory). It
is well known that higher voltages are required to
program such memories than are typically needed by the
other components. For that reason a voltage multiplier 9
with capacitors 18 is employed. Such a design attains
voltages as high as several times that of the basic
source.
Most of the components shown in Fig. 2 are contained
within a box shown in dashed lines. Those are the
components which preferably are integrated onto a chip in
applicable CMOS technology. All other components such as
the capacitors 18, the antenna A, the transceiving coil
15, the adjusting unit 21 etc. are outside the integrated
circuit to which they are connected by appropriate
terminals. The memory 11 is included in latter components
and in practice has been exposed to severe overloads and
therefore its life is shorter than that of the other
components.
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Lastly a single switch 17 driven by the user is present
at the receiving unit 1 to initiate for instance the
following functions:
- By "briefly" closing the switch 17, the following
operational modes will be switched between each
other: "transmit the audio signal", "audio signal
with superposed microphone signal", and "no audio
signal" (toggle mode);
- By closing the switch for a "long time", and after
receiving the audio signals, the frequency band is
scanned (scan mode);
- By closing the switch of a "very long time", the
receiving unit 1 is disconnected; by closing the
switch 17 again, the receiver 1 is re-connected.
The above functions or their transitions can be initiated
by means of the remote control 107, the transmitter Si
through Sn or as called for also by means of the control
unit 102 (Fig. 2).
In order to minimize energy consumption in the receiving
unit 1, steps are taken in the demodulator 4 in addition
to those carried out by the monitoring unit 10.
Illustratively, the amplifier 5 is automatically
squelched as soon as the demodulator 4 ascertains that an
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audio signal no longer is being received. This state is
transmitted by the adjustment unit 7 and the amplifier 5
through the connection SQ and as a result the components
demodulating the transmitted audio signal SIN can be
deactivated. As a result, the energy consumption drops as
desired in the receiving unit 1. At the same time, any
noise shall be eliminated because being not at all
transmitted to the subsequent hearing device 100 (Fig.
1).
Fig. 3 is a functional block diagram of a control unit
102 connected to a loop antenna 101 of Fig. 1.
Substantially,.the control unit 102 consists of a
microcomputer 200 which is radially connected to a memory
204, an input/output unit 203, a display 202, a modulator
201 and an interface 205. Preferably the interface 205 is
designed to drive an USB (universal serial bus) type bus
system.
In a further embodiment of the present invention, data
correcting the transfer function of the information
channel are fed to the receiving unit 1. Such correction
information is ascertained by calculating a desired total
transfer function of the information channel based on the
uncorrected total transfer function. In this manner, any
undesired characteristics of the original total transfer
function can be corrected.
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It is hereby emphasized again that even though the
receiving unit of the present invention and the
transmission system of the present invention were
discussed with respect to an illustrative hearing device,
application in no way is restricted to such a field.
Instead the present invention is applicable to arbitrary
fields wherein information channels must be controlled.
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