Note: Descriptions are shown in the official language in which they were submitted.
CA 02532952 2006-01-30
PORTABLE AUDIO DEVICE HAVING REDUCED SENSITIVITY TO RF
INTERFERENCE AND RELATED METHODS
Field of the Invention
The present invention relates to the field of
electronic devices, and, more particularly, to portable
audio devices and related methods.
Background of the Invention
Cellular communications systems continue to grow in
popularity and have become an integral part of both personal
and business communications. Cellular telephones allow users
to place and receive voice calls most anywhere they travel.
Moreover, as cellular telephone technology has increased, so
too has the functionality of cellular devices and the
different types of devices available to uses. For example,
many cellular devices now incorporate personal digital
assistant (PDA) features such as calendars, address books,
task lists, etc. Moreover, such multi-function devices may
also allow users to wirelessly send and receive electronic
mail (email) messages and access the Internet via a cellular
network and/or a wireless local area network (WLAN), for
example.
Accordingly, because of the widespread use and reliance
on cellular devices, many users carry their cellular devices
on their person much of the day. Yet, since cellular devices
are frequently communicating with a cellular network even
when a user is not participating in a phone call, they are
frequently emitting radio frequency (RF) signals. When in
close proximity to other electronic equipment, such as
personal audio devices (e.g., portable radios, MP3 players,
etc.), these RF signals may cause interference which results
1
CA 02532952 2006-01-30
in an audible buzz or other undesirable sound from the
personal audio device.
One exemplary portable audio device is disclosed in
U.S. patent application publication no. 2003/0059071. This
application is directed to an integrated personal audio
device that provides hearing protection for a user. The
device includes a flexible band configured to extend at
least partially around a head of a user. An audio
transmitter is coupled to the band. The band has two legs
that terminate at respective end portions. Each end portion
is coupled to an audio speaker, which is electrically
connected to the audio transmitter. A hearing protector is
mounted onto each respective audio speaker. Moreover, the
audio transmitter may include RF shielding to filter radio
interference associated with nearby electric equipment, for
example.
While such devices may provide some reduction in
unwanted RF interference, further RF interference protection
may be required to significantly mitigate the effects of RF
interference from a nearby cellular device, for example.
Brief Description of the Drawings
FIG. 1 is a schematic block diagram of a portable audio
device having reduced sensitivity to RF interference from an
adjacent mobile wireless communications device according to
the invention.
FIG. 2 is a schematic block diagram of an alternate
embodiment of the portable audio device of FIG. 1.
FIG. 3 is front view of the portable audio device of
FIG. 2 illustrating a display and user input device thereof.
2
CA 02532952 2006-01-30
FIG. 4 is a schematic diagram of the recharging power
input circuit and associated first RF filter elements of
FIG. 2.
FIG. 5 is schematic diagram of the stereo headphone
audio analog signal output circuit and associated second RF
filter elements of FIG. 2.
FIG. 6 is a schematic block diagram of the line input
digital signal inputs and associated third RF filter
elements of FIG. 2.
FIG. 7 is a schematic diagram of the line out audio
analog signal output circuit and associated second RF filter
elements of FIG. 2.
FIG. 8 is a schematic block diagram of the microphone
audio analog input circuit and associated fourth filter
elements of FIG. 2.
Detailed Description of the Preferred Embodiments
The present description is made with reference to the
accompanying drawings, in which preferred embodiments are
shown. However, many different embodiments may be used, and
thus the description should not be construed as limited to
the embodiments set forth herein. Rather, these embodiments
are provided so that this disclosure will be thorough and
complete. Like numbers refer to like elements throughout,
and prime and multiple prime notation are used to indicate
similar elements in alternate embodiments.
Generally speaking, a portable audio device is
disclosed herein having reduced sensitivity to RF
interference over a predetermined frequency range from an
adjacent mobile wireless communications device. The portable
audio device may include a portable housing, a battery
carried by the portable housing, a recharging power input
3
CA 02532952 2006-01-30
connected to the battery, a digital signal input, and an
audio analog signal output. The portable audio device may
further include a memory carried by the portable housing and
powered by the battery for storing digital audio files input
thereto via the digital signal input. In addition, a
digital-to-analog converter (DAC) may be carried by the
portable housing and powered by the battery for converting a
selected digital audio file from the memory into an analog
audio signal. Moreover, an audio analog amplifier may be
connected between the DAC and the audio analog signal
output. At least one first RF filter may be connected to the
recharging power input for reducing RF interference over the
predetermined frequency range from the adjacent mobile
wireless communications device. Additionally, at least one
second RF filter may be connected to the audio analog signal
output for reducing RF interference over the predetermined
frequency range from the adjacent mobile wireless
communications device.
More particularly, the portable audio device may
further include at least one third RF filter connected to
the digital signal input for reducing RF interference over
the predetermined frequency range from the adjacent mobile
wireless communications device. By way of example, the at
least one third RF filter may be a parallel connected
capacitor. The portable audio device may also include an
audio analog input connected to the audio analog amplifier,
and at least one fourth RF filter connected to the audio
analog signal input for reducing RF interference over the
predetermined frequency range from the adjacent mobile
wireless communications device. The at least one fourth RF
filter may include a series connected inductor and a
parallel connected capacitor, for example.
4
CA 02532952 2006-01-30
By way of example, the at least one first RF filter may
include a parallel connected capacitor, and the at least one
second RF filter may include a series connected inductor and
parallel connected capacitor. In addition, the predetermined
frequency range may be from about 30MHz to 6GHz, for
example. Also, the stored digital audio files may be digital
stereo audio files, MP3 files, etc. Moreover, the portable
audio device may further include at least one display
carried by the portable housing, and at least one user input
device carried by the portable housing.
A related method aspect is for reducing sensitivity of
a portable audio device, such as the one described briefly
above, to RF interference over a predetermined frequency
range from an adjacent mobile wireless communications
device. The method may include connecting at least one first
RF filter to the recharging power input for reducing RF
interference over the predetermined frequency range from the
adjacent mobile wireless communications device, and
connecting at least one second RF filter to the audio analog
signal output for reducing RF interference over the
predetermined frequency range from the adjacent mobile
wireless communications device.
Referring initially to FIG. 1, a portable audio device
20 advantageously has reduced sensitivity to RF interference
over a predetermined frequency range from RF electromagnetic
(EM) energy 21 from an adjacent mobile wireless
communications device 22. In particular, the RF signals
transmitted by the mobile wireless communications device 22
are within one or more predetermined frequency ranges or
bands, as will be appreciated by those skilled in the art.
These transmissions can cause interference at the portable
audio device 20 that results in undesirable audible noises,
CA 02532952 2007-11-05
such as buzzing, for example. As will be described further
below, the portable audio device 20 advantageously includes
a plurality of RF filters to reduce the sensitivity of the
device to such close-proximity RF interference from the EM
energy emanating from the mobile wireless communications
device 22.
The portable audio device 20 illustratively includes a
portable housing 23, a battery 24 carried by the portable
housing, a recharging power input 25 connected to the
battery, a digital signal input 26, and an audio analog
signal output 27. The digital signal input 26 may be a
universal serial bus (USB) 2.0 input, for example, which
allows the portable audio device to be connected to a
personal computer (PC) to download digital audio files
(e.g., digital stereo files, MP3 files, etc.) to be stored
in a memory 30. The recharging power input 25 may be
connected to a DC power adapter, for example. In some
embodiments, the recharging power input 25 may be connected
to the voltage line of the USB port so that the device 20 is
charged when connected to a PC or other USB host, for
example. The audio analog signal output may be a headphone
output and/or stereo line outs for connection to a separate
audio system, etc., for example. Of course, other suitable
inputs/outputs may be used in some embodiments, as will be
appreciated by those skilled in the art.
The portable audio device 20 also illustratively
includes a digital-to-analog converter (DAC) 31 carried by
the portable housing 23 and powered by the battery 24 for
converting a selected digital audio file from the memory 30
into an analog audio signal, as will be appreciated by those
skilled in the art. Moreover, one or more audio analog
amplifiers 32 is illustratively connected between the DAC 31
6
CA 02532952 2006-01-30
and the audio analog signal output 27. The audio analog
amplifier(s) 32 amplifies the analog output signals to the
appropriate level for a headphone or stereo line out, for
example, as will be appreciated by those skilled in the art.
At least one first RF filter 33 is illustratively
connected to the recharging power input 25 for reducing the
RF interference over the predetermined frequency range or
ranges of interest from the adjacent mobile wireless
communications device 22. By way of example, the
predetermined frequency range may be from about 30MHz to
6GHz. Additionally, at least one second RF filter 34 is
illustratively connected to the audio analog signal output
27 also for reducing the RF interference over the
predetermined frequency range from the adjacent mobile
wireless communications device 22. The recharging power
input 25 and audio analog signal output 27 are particularly
susceptible to the RF interference. Yet, by matching the RF
filters 33, 34 to a predetermined frequency range or ranges
typically associated with a cellular or other wireless
communications device (e.g., personal area network (PAN),
WLAN device, etc.) that may be in close proximity to the
portable audio device 20, the overall sensitivity of the
device may be significantly reduced to provide an improved
user experience.
Turning now additionally to FIG. 2, further aspects are
now described with reference to a portable audio device 20'
which illustratively includes at least one third RF filter
35' connected to the digital signal input 26' also for
reducing RF interference over the predetermined frequency
range from the adjacent mobile wireless communications
device 22. In the illustrated embodiment, the digital signal
input 26' has stereo line inputs. Furthermore, the audio
7
CA 02532952 2006-01-30
analog signal output comprises a stereo headphone output
27a' and stereo line output 27b', each of which has a
respective filter element 34a', 34b' and audio analog
amplifiers 32a', 32b'.
The portable audio device 20' also illustratively
includes an audio analog input 36', such as a microphone
input, connected to the audio analog amplifiers 32a', 32b'.
At least one fourth RF filter 37' is further connected to
the audio analog signal input 36' again for reducing RF
interference over the predetermined frequency range from the
adjacent mobile wireless communications device 22.
Referring additionally to FIG. 3, the portable audio
device 20' further illustratively includes a display 38'
carried by the portable housing 23', and a user input device
(i.e., buttons 39') also carried by the portable housing. A
controller or processor (not shown) may cooperate with the
buttons 39' and the display 38' to allow a user to select
digital audio files (e.g., songs, etc.) to be converted to
audio signals (i.e., played) from a menu on the display, as
will be appreciated by those skilled in the art. In the
illustrated example, "Song 2" is selected from among the
listed songs. Of course, other types of user input devices
may be used instead of or in addition to the buttons 39',
such as a touch screen, scroll wheels, track balls, etc., as
will also be appreciated by those skilled in the art.
Moreover, it should be noted that the portable audio device
20' may also be used for displaying digital images and/or
video, as will also be appreciated by those skilled in the
art.
The portable audio device 20' also illustratively
includes respective connectors/plugs 40'-44' for the
recharging power input 25', digital signal input 26', audio
8
CA 02532952 2006-01-30
analog input 36', and audio signal outputs 27a', 27b', as
will be appreciated by those skilled in the art. Other
features and components common to portable audio devices
such as MP3 players and portable radios which are well known
to those of skill in the art may also be included.
Turning now to FIGS. 4-8, particular examples of the
above-noted RF filters are now described. The recharging
power input circuit 25' includes digital voltage inputs
DBVDD and DCVDD connected to the appropriate power supplies
(e.g., 1.42 or 3.3V), a digital ground input DGND, an analog
voltage input AVDD connected to a 3.3V source, an analog
ground AGND, and an additional voltage input HPVDD connected
to a 3.3V source and associated ground HPGND. The first RF
filter 33' illustratively includes a capacitor Cl connected
between the digital voltage input DBVDD and digital ground
DGND (i.e., connected in parallel with DBVDD), a capacitor
C2 connected between the digital voltage input DCVDD and
digital ground DGND, a capacitor C3 connected between the
analog voltage input AVDD and analog ground AGND, and a
capacitor C4 connected between the additional voltage input
HPVDD and associated ground HPGND. Furthermore, capacitors
C5, C6 are connected in parallel with the capacitor Cl,
capacitors C7, C8 are connected in parallel with the
capacitor C2, capacitors C9, C10 are connected in parallel
with the capacitor C3, and capacitors C11, C12 are connected
in parallel with the capacitor C4.
The stereo headphone output circuit 27a' illustratively
includes a left headphone output LHPOUT and a right
headphone output RHPOUT. The left headphone output LHPOUT
has a series connected capacitor C20 and a parallel
connected resistor R1 connected thereto, and the right
headphone output similarly has a series connected capacitor
9
CA 02532952 2006-01-30
C21 and a parallel connected resistor R2 connected thereto,
as shown in FIG. 5. Moreover, the second RF filter 34a'
illustratively includes a series connected inductor Ll and a
parallel connected capacitor C22 connected to the left
headphone output LHPOUT, and a series connected inductor L2
and a parallel connected capacitor C23 connected to the
right headphone output RHPOUT as shown.
The stereo line input circuit 26' illustratively
includes a left line input LLINEIN and a right line input
RLINEIN. A resistor R3 and capacitor C31 are connected in
series with the left line input LLINEIN, and a resistor R4
capacitor C30 are also connected in parallel with the left
line input. Similarly, a resistor R5 and capacitor C33 are
connected in series with the right line input RLINEIN, and a
resistor R6 and capacitor C32 are also connected in parallel
with the right line input as shown in FIG. 6. The third RF
filter 35' illustratively includes a capacitor C34 parallel
connected to the left line input LLINEIN, and a capacitor
C35 parallel connected to the right line input RLINEIN.
The stereo line output circuit 27b' illustratively
includes a left line output LOUT and a right line output
ROUT (FIG. 7) . A capacitor C40 and resistor R10 are series
connected to the left line output LOUT, and a resistor R11
is also parallel connected to the left line output.
Moreover, a capacitor C41 and resistor R12 are series
connected to the right line output ROUT, and a resistor R13
is parallel connected to the right line output. The RF
filter 34b' illustratively includes an inductor L10 series
connected and a capacitor C42 parallel connected to the left
line output LOUT. The RF filter 34b' further illustratively
includes an inductor Lil series connected and a capacitor
C43 parallel connected to the right line output ROUT.
CA 02532952 2006-01-30
In addition, the microphone input circuit 36'
illustratively includes a microphone input MICIN and a
microphone bias input MICBIAS, as shown in FIG. 8. A
capacitor C50 and resistor Rmic are series connected to the
microphone input MICIN, and a resistor R14 and capacitor C51
are also parallel connected to the microphone input.
Furthermore, a resistor R15 is series connected to the
microphone bias input MICBIAS. The fourth RF filter 37'
illustratively includes capacitors C52 and C53 parallel
connected to the microphone input MICIN, as well as a series
connected inductor L12 as shown.
It will be appreciated that the above noted the
selection of the above-noted filter components will be based
upon the given frequency band of interest, and the
additional circuit components connected to the various
inputs/outputs in a given embodiment. Moreover, it will also
be appreciated by those skilled in the art that various
circuits such as the recharging power input circuit 25',
stereo headphone output circuit 27a', stereo line input
circuit 26', stereo line output circuit 27b', and microphone
input circuit 36' may be implemented with an audio
coder/decoder (codec) chip, for example. Moreover, various
components discussed above may be implemented using a
combination of hardware and software modules, as will also
be appreciated by those skilled in the art.
A related method aspect is for reducing sensitivity of
a portable audio device 20 to RF interference over a
predetermined frequency range from an adjacent mobile
wireless communications device 22. The method may include
connecting at least one first RF filter 33 to the recharging
power input 25 for reducing RF interference over the
predetermined frequency range from the adjacent mobile
11
CA 02532952 2006-01-30
wireless communications device 22. The method may further
include connecting at least one second RF filter 34a' to the
audio analog signal output 27a' also for reducing RF
interference over the predetermined frequency range from the
adjacent mobile wireless communications device 22, as
discussed further above. Additional method aspects will be
appreciated from the foregoing description and need not be
discussed further herein.
Many modifications and other embodiments will come to
the mind of one skilled in the art having the benefit of the
teachings presented in the foregoing descriptions and the
associated drawings. Therefore, it is understood that
various modifications and embodiments are intended to be
included within the scope of the appended claims.
12
