EP0318334A1
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EP
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Apparatus and method for converting a frequency division multiplex to a time division multiplex
Assignee: British Telecommunications PLC
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Filing: 1988-11-28
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Granted: —
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Expires: 2008-11-28
Abstract
Abstract Apparatus for converting a frequency division multiplex (fdm) signal to a time domain multiplex (tdm) signal in which a voltage controlled oscillator (21) whose output is a staircase of reference frequencies mixed by a mixer (20) with a received fdm signal. Each received frequency is output in turn at a common intermediate frequency from a bandpass filter 22 thereby forming a fdm signal after passing through a demodulator (23) and low pass filter (24). The conversion may take place in the optical domain by mixing optical reference frequencies with an optical fdm signal in, for example, a coherent heterodyne optical receiver.
Inventors
- 👤 David William Smith
- 👤 Godfrey Richard Hill
- 👤 Roy Andrew Lobbett
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 12:18
CPC Classifications
H; H04; H04J; H04J14/00; H04J14/08
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
128 words
Apparatus for converting a frequency division multiplex into a time division multiplex comprising a reference frequency generator for repeatedly generating a series of reference frequencies in steps at a rate synchronised to the data rate of the frequency division multiplex, the number of reference frequencies being equal to the number of carrier frequencies in the frequency division multiplex signal; mixing means for mixing the frequency division multiplex signal and the reference frequencies to generate intermediate frequencies, the combination of respective pairs of carrier and reference frequencies generating a common intermediate frequency; a bandpass filter for passing only the common intermediate frequency from the output of the mixing means; and demodulating means for generating a data signal from the common intermediate frequency signal as a time division multiplex signal.
Claim 2
Dependent Claim
128 words
Apparatus for converting a frequency division multiplex into a time division multiplex comprising a reference frequency generator for repeatedly generating a series of reference frequencies in steps at a rate synchronised to the data rate of the frequency division multiplex, the number of reference frequencies being equal to the number of carrier frequencies in the frequency division multiplex signal; mixing means for mixing the frequency division multiplex signal and the reference frequencies to generate intermediate frequencies, the combination of respective pairs of carrier and reference frequencies generating a common intermediate frequency; a bandpass filter for passing only the common intermediate frequency from the output of the mixing means; and demodulating means for generating a data signal from the common intermediate frequency signal as a time division multiplex signal.
Claim 3
Dependent Claim
37 words
Apparatus according to either of claims 1 and 2, wherein the repeat frequency of the series of frequencies generated by the reference frequency generator is substantially twice the data rate of the incoming frequency division multiplex signal.
Claim 4
Dependent Claim
19 words
Apparatus according to either of claims 1 and 2 in which the reference frequency generator generates optical reference frequencies.
Claim 5
Dependent Claim
20 words
Apparatus system according to either of claims 1 and 2, wherein the reference frequency generator comprises a voltage controlled oscillator.
Claim 6
Independent Claim
100 words
A method of converting a frequency division multiplex into a time division multiplex comprising repeatedly generating a series of reference frequencies in steps at a rate synchronised to the data rate, the number ofreference frequencies being equal to the number of carrier frequencies in the common frequency division multiplex signal; mixing the common frequency division multiplex signal and the reference frequencies to generate intermediate frequencies, the combination of respective pairs of carrier and reference frequencies generating a common intermediate frequency; and demodulating the common intermediate frequency to generate a data signal in the form of a time division multiplex signal.
Claim 7
Independent Claim
100 words
A method of converting a frequency division multiplex into a time division multiplex comprising repeatedly generating a series of reference frequencies in steps at a rate synchronised to the data rate, the number ofreference frequencies being equal to the number of carrier frequencies in the common frequency division multiplex signal; mixing the common frequency division multiplex signal and the reference frequencies to generate intermediate frequencies, the combination of respective pairs of carrier and reference frequencies generating a common intermediate frequency; and demodulating the common intermediate frequency to generate a data signal in the form of a time division multiplex signal.
Claim 8
Dependent Claim
21 words
A method according to claim 5, wherein the repeat frequency of the series of frequencies is substantially twice the data rate.
Claim 9
Independent Claim
29 words
A method according to either of claims 5 and 6 in which the reference frequency generator generates optical reference frequencies and the mixing takes place in the optical domain.
Claim 10
Dependent Claim
177 words
A communication system comprising a primary station; and a plurality of secondary stations, each of the stations having signal transmitting means and signal receiving means, a first communication link extending from the primary station to signal splitting means for supplying signals from the primary station to each of the secondary stations, and a second communication link extending from signal combining means, which receives signals from each of the secondary stations, to the primary station wherein the signal transmitting means of the primary station and the signal receiving means of the secondary stations are adapted to transmit and receive respectively multiplex signals, the signal transmitting means of the secondary stations are adapted to transmit signals at respective carrier frequencies, the signal combining means combining these signals into a common frequency division multiplex signal and the receiving means of the primary station is adapted to receive the common frequency division multiplex signal, the primarystation including apparatus for converting the common frequency division multiplex signal into a time division multiplex as claimed in any one of claims 1 to 4.
Claim 11
Dependent Claim
14 words
A system according to claim 8, in which the communication links comprise optical waveguides.
Claim 12
Independent Claim
40 words
A system according to either of claims 8 and 9 wherein the signal splitting means and the signal combining means are provided by a common element, a common communication link being provided between the common element and the primary station.
References Cited (Backward Citations)
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