Multiplex communications – Communication over free space – Combining or distributing information via frequency channels
Reexamination Certificate
1999-10-15
2001-07-03
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via frequency channels
C370S315000, C370S492000, C455S042000, C455S555000, C342S125000
Reexamination Certificate
active
06256303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to wireless signal transmission systems and apparatus and, specifically, to wireless transmission system capable of transmitting audio or video signals in either analog or digital format via high frequency carrier signals in the 900 MHZ range and, even more specifically, to wireless signal transmission systems wherein a transmitter coupled to a signal source is linked via a wireless connection to a remote receiver and output device.
2. Description of the Art
Various wireless audio and video signal transmission systems have been devised which transmit audio and/or video signals, such as television signals, radio signals, etc., by a wireless link from a signal source to a signal receiver or output device capable of converting the received signals to audio and/or video sounds.
Local wireless television transmission systems which transmit television or radio signals from a local source, such as a television, VCR, radio set or radio stereo receiver, frequently transmit such signals within a frequency band above 900 MHZ and, preferably, within a frequency band of 902 MHZ to 928 MHZ. This frequency band is desirable because at higher carrier frequencies, the bandwidth of the transmitted signal occupies a smaller region of the transmission bandwidth than at lower carrier frequencies. This leaves more channels available for use and results in decreased RF interference and noise as well as greater flexibility in channel selection.
Many televisions and radio stations now include stereo audio signals in their transmissions. Thus, a wireless signal transmission apparatus must have a capability of transmitting stereo audio signals. Conventionally, stereo audio signals are transmitted by adding the right and left audio channels to form a first signal and subtracting the right and left channels to form a second signal which is modulated on a subcarrier of 38 KHz. The subcarrier is suppressed and the combination of the first signal, the subcarrier modulated second signal, and a 19 KHz pilot signal form a multiplexed stereo signal which modulates a carrier for transmission to a remote receiver. Conventional integrated circuits for producing such multiplexed stereo signals, known as stereo encoder circuits, are available commercially.
Such high frequency wireless transmission systems conventionally include a transmitter which is capable of transmitting a television or radio mono or stereo signals and a remote receiver, both having appropriate antennas for transmitting and receiving the source signals as a modulated high frequency carrier. Heretofore, the remote receiver has been mounted in close proximity to or formed as a part of a signal output device, such as an AM/FM stereo receiver, television, for example. The distance or separation between the remote receiver antenna and the output device is relatively limited due to the low power level signals transmitted at the high carrier frequency. This small transmission range limits the use of additional speakers or an additional receiver and speakers which may not be located in the same general area as the first transmitter and the output device.
Audio and video signals are now available through the Internet typically in the form of streaming broadcast of radio or television programs, recorded music, etc. The audio and/or video signals are downloaded from the Internet signal source by a user's Internet service provider and input through a modem to the user's computer. The computer generates signals to an audio and/or video output card which then transmits analog output signals to speakers coupled to the computer or to a monitor for broadcast of the signals.
Frequently, however, the audio system or the monitor employed with a computer is not as sophisticated as the user's home stereo system or television. Further, a user's computer may not be located in the same room or area of a home as the multi-component stereo system or television.
Thus, it would be desirable to provide a wireless signal transmission apparatus which is capable of retransmitting high frequency audio and/or video signals modulated on a high frequency carrier by a first transmitter and transmitted wirelessly via the high frequency carrier to a remote receiver for re-broadcast. It would also be desirable to provide a wireless signal transmission apparatus which has an expanded transmission range as compared to previously devised high frequency transmission systems. It would also be desirable to provide a wireless high frequency signal transmission system which is capable of re-broadcasting streaming broadcast signals from the Internet or any other audio and/or video source to a remote receiver which may located at a considerable distance from the originating transmission source.
SUMMARY OF THE INVENTION
The present invention is a signal transmission apparatus capable of transmitting audio and/or video signals from a suitable signal source via a high frequency (900 MHZ) carrier to a remote receiver which down converts the high frequency carrier signal to a lower frequency carrier signal and combines it with the modulated signal before transmitting the second modulated signal to a further remote receiver capable of demodulating and generating audio and/or video output.
According to one aspect of the present invention, the apparatus includes a first transmitter adapted to be coupled to the signal source for providing audio and/or video frequency signals in either analog or digital format. The signal source may be any source capable of generating audio signals, such as a sound generator circuit in a computer, a CD player, an AM/FM tuner or AM/FM stereo receiver, and/or video signals, such as a cable TV signal, VCR, satellite downlink, television broadcast, etc.
A first oscillator produces a high frequency carrier signal. Means are provided for combining the high frequency carrier signal with the audio and/or video frequency signals to form a first modulated signal transmitted by an antenna from the first transmitter.
A first receiver, remote from the first transmitter, is connected to an antenna for receiving the first modulated signal. Means are provided for down converting the first modulated signal from the high frequency carrier signal of the first transmitter to a second modulated signal including a lower frequency carrier signal. A second transmitter is coupled to the first receiver and the converting means for retransmitting the second modulated signal to a further remote receiver capable of generating audio sounds and/or displaying video images after demodulating the received modulated signal.
According to one aspect of the invention, the first selectable means are connected to the first oscillator to generating one of a plurality of discrete carrier frequency outputs from the first oscillator. Preferably, the oscillator output frequencies are in the 900 MHZ range.
In another aspect, the first selectable means comprises means for inputting one of a plurality of discrete voltages to the first oscillator. These voltages may be, in one aspect of the invention, provided by user control of a multiposition switch on the base unit containing the first transmitter.
According to another aspect of the present invention, the second selectable means is coupled to the remote receiver for generating one of a plurality of discrete second carrier frequencies from a second oscillator coupled to the second transmitter.
In another aspect of the present invention, a second oscillator is coupled to the first receiver for converting the carrier frequency of the first modulated signal to a lower frequency carrier. The second selectable means further includes means for selecting one of a plurality of crystals, each enabling the second oscillator to oscillate at a discrete frequency.
According to the invention, the converting means further comprises means for converging the high frequency carrier signal of the first modulated signal received by the receiver to a lower carrier signal use
Drakoulis Niko
Pace Ronald G.
Pedigo Michael K.
Phillips Russell A.
Akoo, Inc.
Hom Shick
Olms Douglas
Young & Basile PC
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