Frequency division multiplex communications system
First Claim
1. A frequency division multiplex communication system, comprising:
- a plurality of subscriber stations coupled to a transmission line, each of said stations including at least one transmitter and at least one receiver having respectively an assigned transmitting frequency and an assigned receiving frequency;
said assigned frequencies being related by a fixed frequency separation corresponding to the difference in transmitter and receiver intermediate frequencies;
mixer means for mixing a predetermined frequency with said intermediate frequencies to derive an independent sideband signal such that one sideband thereof contains communication information and the other of sideband thereof contains signalling data;
bandpass filter means at said transmitter and said receiver having a passband of approximately twice the difference in frequency between said transmitter intermediate frequency and said receiver intermediate frequency for rejecting undesired mixing products such that the desired sideband signal is selected;
means for coupling said independent sideband signal onto said transmission line; and
means for coupling a common reference frequency onto said transmission line to obtain simultaneous communications and signalling in the same frequency band without interference therebetween.
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Accused Products
Abstract
An FDM communication system is disclosed wherein two separate intermediate frequencies are utilized in such manner that the difference between transmitting and receiving frequencies thus generated is the difference between the two separate intermediate frequencies, thereby providing the capability of using independent sideband transmission instead of single sideband transmission, thus providing additional channel capacity. A single synthesizer is utilized and a single bandpass filter selects the appropriate upper or lower sidebands of transmission for full duplex operation. One of the two available sidebands is then used for communication, with the other sideband available for signalling, monitoring, break-in or other telecommunication functions.
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Citations
18 Claims
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1. A frequency division multiplex communication system, comprising:
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a plurality of subscriber stations coupled to a transmission line, each of said stations including at least one transmitter and at least one receiver having respectively an assigned transmitting frequency and an assigned receiving frequency;
said assigned frequencies being related by a fixed frequency separation corresponding to the difference in transmitter and receiver intermediate frequencies;mixer means for mixing a predetermined frequency with said intermediate frequencies to derive an independent sideband signal such that one sideband thereof contains communication information and the other of sideband thereof contains signalling data; bandpass filter means at said transmitter and said receiver having a passband of approximately twice the difference in frequency between said transmitter intermediate frequency and said receiver intermediate frequency for rejecting undesired mixing products such that the desired sideband signal is selected; means for coupling said independent sideband signal onto said transmission line; and means for coupling a common reference frequency onto said transmission line to obtain simultaneous communications and signalling in the same frequency band without interference therebetween. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a frequency division multiplex communication system, a subscriber station comprising:
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a transmitter and a receiver coupled to a transmission line, said transmitter and receiver having respectively an assigned transmitting frequency and an assigned receiving frequency, said assigned frequencies being related by a fixed frequency separation corresponding to the difference in transmitter and receiver intermediate frequencies; mixer means for mixing a predetermined frequency with said intermediate frequencies to derive an independent sideband signal such that one sideband thereof contains communication information and the other sideband contains signalling data; bandpass filter means at said transmitter and said receiver having a passband of approximately twice the difference in frequency between said transmitter intermediate frequency and said receiver intermediate frequency, for rejecting undesired mixing products such that the desired sideband signal is selected; means for coupling said independent sideband signal onto said transmission line; and means for a common reference frequency onto said transmission line to obtain simultaneous communications and signalling in the same frequency band without interference therebetween. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for frequency division multiplex communication including the steps of:
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coupling a plurality of subscribers to a transmission line, each of said subscribers having assigned transmitting and receiving frequencies, said frequencies being related by a fixed frequency separation, said separation being the difference in intermediate frequencies used in generating of the transmitting and receiving frequencies; mixing a synthesized frequency with said intermediate frequencies to derive an independent sideband signal such that one sideband thereof contains communication information and the other sideband thereof contains signalling data; bandpass filtering undesired mixing products to reject and pass undesired and desired upper and lower sideband signals respectively of said mixing products at a passband of approximately twice the difference in frequency between said transmitting and receiving intermediate frequencies; and coupling a common reference frequency onto said transmission line together with said independent sideband signal such that simultaneous communications and signalling in the same frequency band without interference therebetween. - View Dependent Claims (18)
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Specification