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Claims  |
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What is claimed is:
1. A wireless audio and video signal transmitter and receiver system
capable of accepting both external baseband audio and video signal inputs
and an external modulated audio/video signal input modulated at a
particular television channel, wherein the transmitter transmits an
audio/video signal to one or more remote receivers which regenerate the
original audio/video signal providing both baseband audio and video signal
outputs as well as a modulated audio/video signal output at said
particular television channel, said wireless audio/video signal
transmitter and receiver system comprising:
transmitter means for connection to audio/video signal sources and are
capable of accepting said external modulated audio/video signal input as
well as said external baseband audio and video signal inputs, said
transmitter means including:
modulated audio/video signal input means for permitting an external
audio/video modulated signal to be connected to said transmitter means,
said modulated audio/video signal input means serving to convert said
external modulated audio/video signal into a first internal baseband video
signal and a first internal audio subcarrier signal corresponding to said
external modulated audio/video signal input;
baseband audio signal input means for permitting an external baseband audio
signal to be connected to said transmitter means, said baseband audio
signal input means serving to convert said external baseband audio signal
into a second internal audio subcarrier signal;
baseband video signal input means for permitting an external baseband video
signal source to be connected to said transmitter means, said baseband
video signal input means providing as an output a second internal baseband
video signal;
video/RF switch means operably and electrically connected to said modulated
audio/video signal input means, said baseband audio signal input means and
said baseband video signal input means, said video/RF switch means serving
to permit the selection between said first internal audio subcarrier
signal and said second internal audio subcarrier signal, and said first
internal baseband video signal and said second internal baseband video
signal, thus providing for the alternative selection by the user between
said external modulated audio/video signal input and said external
baseband audio/video signal input in a manner which obviates the need for
the use of an RF switch; said video/RF switch means providing an audio
subcarrier audio signal output and a baseband video signal output;
video filter means operably and electrically connected to said baseband
video signal output of said video/RF switch means providing a filtered
video signal output;
AM modulator means electrically connected to said audio subcarrier signal
output of said video/RF switch means and said filtered video signal output
of said video filter means, said AM modulator means serving to AM modulate
both said filtered video signal output and audio subcarrier signal output
towards converting said signal outputs to a modulated IF frequency signal;
up converter means electrically connected to said AM modulator means for
converting said modulated IF frequency signal to an RF frequency signal;
RF amplifier means electrically connected to said up converter means for
amplifying said RF frequency signal;
transmitter antenna means electrically connected to said RF amplifier means
for transmitting said amplified RF signal;
one or more receiver means capable of providing an external modulated
audio/video signal output as well as external baseband audio signal and
baseband video signal outputs, said one or more receiver means each
including:
receiver antenna means for receiving said amplified RF signal transmitted
by said transmitter means;
receiver front end means electrically connected to said receiver antenna
means for amplifying and filtering said received RF signal;
down converter means electrically connected to said receiver antenna means,
said down converter means serving to convert said received RF signal to an
IF signal having a frequency corresponding to the carrier frequency for
said modulated IF frequency signal;
receiver filter means electrically connected to said down converter means
providing a filtered IF signal output;
modulated audio/video signal output means electrically connected to said
receiver filter means for providing a modulated audio/video signal output
on said particular television channel;
modulated audio/video signal demodulator means electrically connected to
said receiver filter means, said modulated audio/video signal demodulator
means serving to provide a composite audio and video output signal;
baseband audio signal output means, electrically connected to said
modulated audio/video signal demodulator means, for providing a baseband
audio signal output; and
baseband video signal output means, electrically connected to said
modulated audio/video signal demodulator means, for providing a baseband
video signal output;
whereby said wireless audio/video signal transmitter and receiver system
permits the wireless transmission and remote reception of audio/video
signals from a signal source such as a VCR to a reception device such as a
television monitor.
2. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said down converter means converts said
received RF signal directly to an IF signal corresponding to the carrier
frequency for television channel 3 of 61.25 MHz whereby said IF signal can
be directly provided on the receiver means as a channel 3 television
interface having a full double sideband signal resulting in minimal
degradation in picture quality.
3. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said transmitter means transmits said
audio/video signal on one of two user selectable RF channels of 914 MHz
and 919 MHz by providing for the user selectable AM modulation at IF
frequencies of 245 MHz and 250 MHz, which correspond to RF frequencies of
914 and 919 MHz.
4. The invention according to claim 1 wherein said one or more receiver
means of said wireless audio and video signal transmitter and receiver
system further includes modulated audio/video signal bypass means operably
and electrically connected to said modulated audio/video signal output
means of said receiver means, said modulated audio/video signal bypass
means serving to connect said transmitted RF signal to the output of said
modulated audio/video signal output means when said wireless audio and
video signal transmitter and receiver system is in use and further serving
to alternatively connect an external modulated audio/video signal source
applied to said modulated audio/video signal bypass means to the output of
said modulated audio/video signal output means when said wireless audio
and video signal transmitter and receiver system is not in use.
5. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said modulated audio/video signal input means
comprises:
modulated audio/video signal input connector means for accepting connection
of said externally modulated audio/video input signal;
first modulated audio/video signal detector means for converting said
external modulated audio/video input signal to a composite internal
baseband video signal and audio subcarrier signal;
audio subcarrier filter and amplifier means electrically connected to said
modulated audio/video signal detector means for removing unwanted video
information from said audio subcarrier signal providing said first
internal audio subcarrier signal; and
video buffer means electrically connected to said modulated audio/video
signal detector means providing said first internal baseband video signal.
6. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said baseband audio signal input means
comprises:
baseband audio signal input connector for accepting connection of said
external baseband audio signal;
pre-emphasis network means electrically connected to said baseband audio
signal input connector, said pre-emphasis network means serving to boost
high frequency components of said external baseband audio signal toward
removing noise components from said signal when demodulated;
audio subcarrier modulator electrically connected to said pre-emphasis
network means for modulating said external baseband audio signal
generating an audio subcarrier signal output; and
audio subcarrier signal buffer means electrically connected to said audio
subcarrier modulator providing as an output said second internal audio
subcarrier signal.
7. The wireless audio and video signal transmitter and receiver system
according to claim wherein said baseband video signal input means
comprises:
baseband video signal input connector for accepting connection of said
external baseband video signal.
8. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said video/RF switch means comprises a DPDT
switch the first half of which permits the selection between said first
internal audio subcarrier signal and said second internal audio subcarrier
signal, and the second half of which permits the simultaneous selection
between said first internal baseband video signal and said second internal
baseband video signal.
9. The wireless audio and video signal transmitter and receiver system
according to claim 8 wherein said video filter means comprises:
baseband video filter amplifier electrically connected to said second half
of said RF/video switch, baseband video filter buffer electrically
connected to said baseband video filter amplifier; and baseband video
filter lowpass filter electrically connected to said baseband video filter
buffer, said baseband video filter amplifier, said baseband video filter
buffer and said baseband video filter lowpass filter serving to remove
unwanted audio subcarrier frequency components from said baseband video
signal.
10. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said AM modulator means provides a double
sideband output signal at 245 MHz or 250 MHz and further includes AM
modulator balanced-to-unbalanced converter electrically connected to said
AM modulator means, AM modulator bandpass filter electrically connected to
said AM modulator balanced-to-unbalanced converter; AM modulator variable
attenuator electrically connected to said AM modulator bandpass filter, AM
modulator amplifier electrically connected to said AM modulator variable
attenuator, AM modulator matching pad electrically connected to said AM
modulator amplifier, and AM modulator lowpass filter electrically
connected to said AM modulator matching pad towards removing spurious
components from said modulated audio/video signal.
11. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said up converter utilizes a fixed local
oscillator to convert said modulated audio/video signal to said RF signal.
12. The wireless audio and video signal transmitter and receiver system
according to claim wherein said RF amplifier means comprises RF section
bandpass filter electrically connected to said up converter means, RF
section matching pad electrically connected to said RF section bandpass
filter, RF section amplifier electrically connected to said RF section
matching pad; combination highpass/notch filter electrically connected to
said RF section matching pad; RF section matching amplifier means
electrically connected to said combination highpass/notch filter; and RF
section lowpass filter electrically connected to said RF section matching
amplifier means.
13. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said receiver front end means comprises input
amplifier means, input bandpass filter means and high gain input
amplifier, connected in series, said receiver front end means serving to
amplify and filter said received RF signal.
14. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said receiver filter means comprises receiver
filter lowpass filter electrically connected to said down converter means,
receiver filter amplifier electrically connected to said receiver filter
lowpass filter, and receiver filter bandpass filter electrically connected
to said receiver filter amplifier toward eliminating undesired frequency
components above and below said external modulated audio/video signal and
frequency components generated by said down converter means.
15. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said modulated audio/video signal output
means comprises: modulated audio/video signal output attenuator
electrically connected to said receiver means for controlling signal
strength, modulated audio/video signal output buffer electrically
connected to said attenuator and modulated audio/video output signal
connector electrically connected to said modulated audio/video signal
output buffer.
16. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said modulated audio/video signal demodulator
means comprises: audio/video signal demodulator highpass filter
electrically connected to said receiver filter means, second modulated
audio/video signal detector means for providing said composite audio/video
output signal corresponding to said modulated audio/video signal input to
said transmitter means, said second detector means electrically connected
to said audio/video signal demodulator highpass filter.
17. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said baseband audio signal output means
comprises: audio subcarrier bandpass filter electrically connected to said
modulated audio/video signal demodulator means for filtering out unwanted
video signal components, audio output audio subcarrier demodulator means
electrically connected to said audio output bandpass filter for
demodulating the audio subcarrier signal and converting said audio
subcarrier signal to said baseband audio signal, audio output amplifier
electrically connected to said audio subcarrier detector, and de-emphasis
means electrically connected to said amplifier.
18. The wireless audio and video signal transmitter and receiver system
according to claim 1 wherein said baseband video signal output means
comprises: video output buffer electrically connected to said modulated
audio/video signal demodulator means, video output lowpass filter
electrically connected to said video output buffer for filtering out
undesired audio components of said video signal; video output level
control means electrically connected to said video output lowpass filter;
and final video output buffer electrically connected to said video output
level control means.
19. The wireless audio and video signal transmitter and receiver system
according to claim 5 wherein said modulator audio/video signal input means
further includes modulated audio/video signal output connector
electrically connected to said audio/video signal input connector for
providing a modulated audio/video signal output signal corresponding to
said modulated audio/video signal input signal.
20. The wireless audio and video signal transmitter and receiver system
according to claim 6 wherein said baseband audio signal input means
further includes baseband audio signal output connector electrically
connected to said baseband audio signal input connector for providing a
baseband audio signal output corresponding to said baseband audio signal
input.
21. The wireless audio and video signal transmitter and receiver system
according to claim 7 wherein said baseband video signal input means
further includes baseband video signal output connector electrically
connected to said baseband video signal input connector for providing a
baseband video signal output corresponding to said baseband video signal
input. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates generally to the transmission of audio/video
television signals, and, in particular, to a wireless audio and video
transmitter and receiver system apparatus capable of accepting both
external baseband audio and video signal inputs and an external modulated
audio/video signal modulated at a frequency corresponding to a particular
television channel. In the present wireless audio and video transmitter
and receiver system apparatus the transmitter transmits an AM modulated
audio/video signal via an RF carrier in the 900 MHz band to one or more
remote receivers which regenerate the original audio/video signal
providing both baseband audio and video signal outputs as well as a
modulated audio/video signal output at the particular television channel.
Advances in technology and manufacturing have resulted in the video
cassette recorder (VCR) becoming virtually common place in households
which own a television set. In homes owning multiple television sets, the
VCR is typically placed adjacent to and hardwire connected to a single
designated television set. Should one desire to view a video cassette, one
has to view the video cassette on the particular television set to which
the VCR is physically attached. Should one wish to view the video cassette
on another television set, one alternative is to disconnect the VCR from
its designated television set and reconnect the VCR to a 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 signal to be
directed to the desired television set. 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 susceptable to
damages 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 wires run from television to television as
well as risk damage to any connecting cables. 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 900 MHz
by taking advantage of revised FCC regulations which have allocated the
band of 902 MHz to 928 MHz for this application.
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
audio and video signal transmitter and receiver system apparatus capable
of accepting both a modulated audio/video signal and baseband audio and
baseband video signals as inputs to a transmitter.
It is additionally an object of the present invention to provide for the
user to select between the external modulated audio/video signal and
external baseband audio/video signals as inputs to the transmitter.
It is yet a further object of the present invention to convert the external
modulated audio/video signal input and the baseband audio and video signal
inputs to common audio subcarrier and baseband video signals to permit the
selection between said inputs to be performed with a mechanical switch in
place of costly RF switching components.
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 corresponding
to a modulated audio/video signal in turn corresponding to a standard
television channel frequency, so as to provide for the direct interface to
a television set.
It is a further object of the present invention to provide for the user to
select between two RF channels of 914 MHz and 919 MHz for transmission of
an audio/video signal by providing for the user selectable AM modulation
at IF frequencies of 245 MHz and 250 MHz.
It is an object of the present invention to provide for filtering of the
received audio/video signal without the use of SAW filters.
These and other objects of the invention will become apparent in light of
the present specification and drawings.
SUMMARY OF THE INVENTION
The present invention comprises a wireless audio and video signal
transmitter and receiver system apparatus capable of accepting both
external baseband audio and video signal inputs and an external modulated
audio/video signal modulated at a particular television channel, such as
television channel 3. The wireless audio and video signal transmitter and
receiver system apparatus serves to transmit an audio/video signal to one
or more remote receivers which regenerate the original audio/video signal
providing both baseband audio and video signal outputs as well as a
modulated audio/video signal output at the predetermined particular
television channel.
In the preferred embodiment of the invention, the modulated external
audio/video signal is modulated at channel 3, such that the transmitter
accepts a channel 3 input, in addition to the baseband inputs. The
receiver thus regenerates the channel 3 output, in addition to the
respective baseband video and audio outputs.
Transmitter means are provided for connection to an audio/video signal
source, such as a video cassette recorder (VCR), and is capable of
accepting an external modulated audio/video signal input, such as channel
3, as well as external baseband audio and video signal inputs, which
inputs are typically provided as RCA jack terminals on the connector
portions of VCRs.
The transmitter means includes modulated audio/video signal input means for
permitting an external audio/video modulated signal source to be connected
to the transmitter means wherein the modulated audio/video signal input
means serves to convert the external modulated audio/video signal into a
first internal baseband video signal and a first internal audio
sub-carrier signal which both correspond to the external modulated
audio/video signal input. Baseband audio signal input means are provided
for permitting an external baseband audio signal source to be connected to
the transmitter means. The baseband audio signal input means serves to
convert the external baseband audio signal into a second internal audio
sub-carrier signal.
Baseband video signal input means are provided for permitting an external
baseband video signal source to be connected to the transmitter means. The
baseband video signal input means provides as an output a second internal
baseband video signal.
In order to permit the user of the wireless audio and video signal
transmitter and receiver system apparatus to select between the external
modulated audio/video signal modulated at the particular television
channel and the baseband audio and video signal as an input to the
transmitter means, a video/RF switch is provided. The video/RF switch is
operably and electrically connected to the modulated audio/video signal
input section, the baseband audio signal input section and the baseband
video signal input section of the apparatus. The video/RF switch means
thus serves to permit the user to select between the first internal audio
sub-carrier signal and the second internal audio sub-carrier signal, and
the first internal baseband video signal and the second internal baseband
video signal. The switching of audio sub-carrier signals and baseband
video signals in the manner contemplated by this invention can be
performed with a mechanical switch thus obviating the need for the use of
an RF switch since both alternative inputs to the video/RF switch are at
audio sub-carrier and video baseband frequencies respectively. The
video/RF switch thus provides as an output the user selected audio
sub-carrier signal and the user selected baseband video signal.
The transmitter means further includes video filter means operably and
electrically connected to the baseband video signal output of the video/RF
switch. The video filter means serves to remove any audio sub-carrier
components from the baseband video signal output of the video/RF switch.
The modulated audio/video signal input means likewise serves to remove
unwanted video signal components from the audio sub-carrier signal which,
however, is performed prior to the audio sub-carrier signal passing
through the video/RF switch.
AM modulator means is provided and is electrically connected to the audio
sub-carrier signal output of the video/RF switch means and the filtered
video signal output of the video filter means. The AM modulator means
serves to AM modulate both the filtered video signal output and the audio
sub-carrier signal output towards converting said signals to a modulated
IF frequency audio/video signal. The output of the AM modulator means is
connected to the up converter means which serves to convert the modulated
IF frequency signal to an RF frequency signal.
RF amplifier means are provided and are electrically connected to the up
converter means and serves to amplify the RF frequency signal generated by
the up converter means.
Transmitter antenna means are provided and electrically connected to the RF
amplifier means for transmitting the amplified RF signal to the one or
more receiver means.
One or more receiver means are provided, each of which is capable of
providing an external modulated audio/video signal output as well as
external baseband audio signal and baseband video signal outputs.
Receiver antenna means are provided with each receiver means for receiving
the RF signal transmitted by the transmitter means.
Receiver front end means is electrically connected to receiver antenna
means and serves to amplify and filter the received RF signal. Down
converter means, electrically connected to the receiver antenna means, are
provided and serves to convert the received RF signal to an IF signal
which has a frequency corresponding to the carrier frequency for the
modulated audio/video signal. In the example referred to above, the down
converter means converts the received RF signal to an IF signal having a
frequency corresponding to television channel 3.
Receiver filter means are provided and are electrically connected to the
down converter means. The receiver filter means provides a filtered IF
signal output by removing from the IF signal frequency components above
and below the frequency of the modulated audio/video signal as well as
frequencies which may be present due to the local oscillator present in
the down converter operation.
Modulated audio/video signal output means are electrically connected to the
receiver filter means for providing a modulated audio/video signal output
on the particular television channel, in the present example, channel 3.
Modulated audio/video signal demodulator means are provided and are
electrically connected to the receiver filter means. The modulated
audio/video signal demodulator means serves to provide a composite audio
and video output signal. Baseband audio signal output means are
electrically connected to the modulated audio/video signal demodulator
means and serves to provide a baseband audio signal output. Likewise,
baseband video signal output means are provided and are electrically
connected to the modulated audio/video signal demodulator means and serves
to provide a baseband video signal output. Accordingly, the wireless
audio/video signal transmitter and receiver system apparatus permits the
wireless transmission and remote reception of audio/video signals from the
signal source, such as a VCR, to a reception device, such as a television
monitor, which monitor is located remote from and not physically connected
to the signal source.
In one embodiment of the invention, the wireless audio and video signal
transmitter and receiver system apparatus includes down converter means
which converts the received RF signal directly to an IF signal which
corresponds to the carrier frequency for television channel 3, namely,
61.25 MHz. In this manner, the IF signal provided by the down converter
means can be directly provided to the receiver means as a television
channel 3 interface having a full double-side band signal which results in
minimal degradation of picture quality.
In the preferred embodiment of the invention the transmitter means of the
wireless audio and video signal transmitter and receiver system apparatus
transmits the audio/video signal on one of two user selectable RF
channels. In the embodiment illustrated, those channels are 914 MHz and
919 MHz. This is accomplished by providing for the user selectable AM
modulation of the audio sub-carrier and baseband video signals such that
AM modulation occurs at IF frequencies of 245 MHz and 250 MHz which
correspond to RF frequencies of 914 MHz and 919 MHz respectively.
The receiver means of the wireless audio and video signal transmitter and
receiver system apparatus preferably further includes modulated
audio/video signal bypass means. Modulated audio/video signal bypass means
are operably and electrically connected to the modulated audio/video
signal output means of the receiver and serves to connect the transmitted
RF signal to the output of the modulated audio/video signal output means
when the transmitter and receiver system apparatus is in use. The
modulated audio/video signal bypass means further serves to alternatively
connect a modulated audio/video signal source applied to the receiver
means to the output of the modulated audio/video signal output means when
the receiver is not in use. The television monitor connected to the
receiver means will receive the output of the receiver means directly when
the system apparatus is in use and, alternatively, will thus receive an
auxiliary input to the receiver means when the receiver is not in use,
such auxiliary input typically being an additional signal source such as a
local antenna, VCR, or cable system connection.
In the preferred embodiment of the invention, the modulated audio/video
signal input means comprises modulated audio/video signal input connector
means for accepting connection of the external modulated audio/video input
signal. First modulated audio/video signal detector means are provided for
converting the external modulated audio/video signal input to a composite
internal baseband video signal and an audio sub-carrier signal. Further
included are audio sub-carrier filter and amplifier means electrically
connected to the modulated audio/video signal detector means for removing
unwanted video information from the audio sub-carrier signal towards
providing a first internal audio sub-carrier signal. The modulated
audio/video signal input means further includes video buffer means
electrically connected to the modulated audio/video signal detector means
for providing the first internal baseband video signal.
The baseband audio signal input means of the present apparatus preferably
comprises baseband audio signal input connector for accepting connection
of the external baseband audio signal, pre-emphasis network means which
are electrically connected to the baseband audio signal connector. The
pre-emphasis network means serves to boost the high frequency components
of the internal baseband audio signal toward removing noise components
when the signal is demodulated. Baseband audio sub-carrier modulator is
included and is electrically connected to the pre-emphasis network means
and serves to modulate the external baseband audio signal thereby
generating an audio sub-carrier signal output. Audio sub-carrier buffer
means are electrically connected to the baseband audio sub-carrier
modulator towards providing as an output therefrom a second internal audio
sub-carrier signal.
The baseband video signal input means of the present apparatus comprises a
baseband video signal input connector for accepting connection of the
external baseband audio signal.
In the present invention, the video/RF switch comprises a double-pole
double-throw switch the first half of which permits the selection between
the first internal audio sub-carrier signal and the second internal audio
subcarrier signal. The second half of the double-pole double-throw switch
serves to permit the selection between the first internal baseband video
signal and the second internal baseband video signal.
The baseband video filter of the present apparatus preferably comprises a
baseband video filter amplifier electrically connected to the second half
of the video/RF switch, baseband video filter buffer electrically
connected to the baseband video filter amplifier and baseband video filter
lowpass filter electrically connected to the baseband video filter buffer.
The baseband video filter amplifier, video filter buffer and video filter
lowpass filter serve to remove unwanted audio sub-carrier frequency
component from the baseband video signal.
The AM modulator means of the present apparatus provides a double-side band
output signal at 245 MHz or 250 MHz, in the present preferred embodiment
of the invention. The AM modulator means further includes balanced to
unbalanced converter electrically connected to the AM modulator means,
bandpass filter electrically connected to the balanced to unbalanced
converter, variable attenuator electrically connected to the bandpass
filter and an amplifier electrically connected to the variable attenuator.
In addition, matching pad and lowpass filter connected in series to the AM
modulator amplifier all of which serves to remove spurious and harmonic
components from the modulated audio/video signal, which spurious and
harmonic components may otherwise interfere with other operating devices.
The up converter means of the present invention utilizes a fixed local
oscillator to convert the modulated audio/video signal to an RF signal.
The RF amplifier means to which the signal passes in the present invention
comprises a bandpass filter, matching pad, amplifier, combination
highpass/notch filter, two amplifiers and lowpass filter all of which are
connected in series. The transmitter antenna comprises a coax balun and
dipole antenna which serves to transmit the RF signal to the receiver.
The receiver antenna means comprises a loop antenna and a coax balun which
is connected to the receiver front end means which comprises an amplifier,
input bandpass filter centered at 917 MHz and a high gain amplifier
connected in series. The input filter provides image rejection at 795 MHz.
The receiver filter means preferably comprises a lowpass filter, amplifier,
bandpass filter all connected in series serving to eliminate undesired
frequency components above and below the external modulated audio/video
signal (channel 3) and the frequency components which are generated by the
local oscillator present in the down converter means.
The modulated audio/video signal output means of the present apparatus
comprises a signal output attenuator electrically connected to the
receiver means for controlling signal strength, signal output buffer
electrically connected to the attenuator means and modulated audio/video
signal output connector electrically connected to the signal output
buffer.
In the present invention, the modulated audio/video signal demodulator
means preferably comprises highpass filter electrically connected to the
receiver filter means, a second modulated audio/video signal detector
means for providing a composite audio/video signal corresponding the
modulated audio/video signal input to the transmitter means and second
detector means electrically connected to the audio/video signal
demodulator highpass filter.
The baseband audio signal output means of the present invention preferably
comprises an audio subcarrier output bandpass filter electrically
connected to the modulated audio/video signal demodulator means for
filtering out unwanted video signal components. Audio sub-carrier
demodulator means are electrically connected to the audio subcarrier
bandpass filter for demodulating the audio subcarrier signal and
converting the signal to the baseband audio signal, amplifier is
electrically connected to the sub-carrier detector and de-emphasis means
are electrically connected thereto.
The baseband video signal output means of the preferred embodiment of the
invention comprises video output buffer electrically connected to the
modulated audio/video signal demodulator means, video output lowpass
filter electrically connected to the video output buffer for filtering out
undesired audio components from said video signal, video output level
control means electrically connected to the video output lowpass filter
and final video output buffer electrically connected to the video output
level control means.
In the present embodiment of the invention, the modulator audio/video
signal means further includes modulated audio/video signal output
connector which is electrically connected to the audio/video signal input
connector and which provides a modulated audio/video signal output signal
which corresponds to the input signal. In this manner, the signal source
which is applied to the transmitter may be connected in such a manner as
to bypass the transmitter and connect to a television monitor at the
transmitting end of the system. Likewise, the baseband audio signal input
means and the baseband video signal input means each further respectively
include baseband audio signal output connector and baseband video signal
output connector connected to the respective baseband audio signal input
connector and baseband video signal input connector towards providing such
"bypass" operation of the transmitter.
In operation, the transmitter of the present invention is connected to the
signal sources, typically a VCR as one source and a second source such as
a camcorder. The input source selection is then performed through
actuation of the video/RF switch on the transmitter. The transmitter may
be operated on either of two RF channels, channel A or channel B.
Alternate selection permits the user to select a second channel if
interference is present on the first channel. Of course, the receiver is
to be set on the same RF channel as the transmitter. The baseband outputs
of the receiver can be used to connect to the input of a VCR while the
modulated signal output can be connected directly to the VHF input of the
television set. In the present invention, both the baseband and modulated
outputs of the receiver are available simultaneously.
At the receiver, a VHF/UHF input is provided for connection to a variety of
VHF/UHF television signal sources. For example, the VHF/UHF input can be
the channel 3 output of another VCR or a cable signal. When the receiver
power is turned off, whatever signal is applied to the VHF/UHF input is
looped through to the channel 3 output.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1, FIG. 2 and FIG. 3 of the drawings comprise a block diagram
illustrating the functional modules of the transmitter means comprising
the present invention;
FIG. 4 of the drawings is comprised of FIGS. 4A and 4B.
FIGS. 4A and 4B are schematic circuit diagrams illustrating the modulated
audio/video signal input means, baseband audio signal input means,
baseband video signal input means and video/RF switch means of the
transmitter means of the present invention;
FIG. 5 of the drawings is a schematic circuit diagram of the power supply
circuitry for the transmitter means of the present invention;
FIG. 6 of the drawings is composed of FIGS. 6A and 6B.
FIGS. 6A and 6B are schematic circuit diagrams of the AM modulator means of
the transmitter means of the present invention;
FIG. 7 of the drawings is composed of FIGS. 7A and 7B.
FIGS. 7A and 7B are schematic circuit diagrams of the up converter means,
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