EP0725477A2
Expired / Lapsed
EP
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Distortion compensator
Assignee: NTT Inc
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Filing: 1996-01-17
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Granted: —
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Expires: 2016-01-17
Abstract
Abstract In order to carry out high-precision control of distortion compensation, the received signal is split into two, one of the resulting signals ("the first signal") is passed to a distortion generator (11) with similar characteristics to the distortion produced at the transmitting side, and the phase and amplitude of the other of the resulting signals ("the second signal") are controlled. By adding these two signals, the desired signal is suppressed and only the distortion component is extracted. This process is controlled by correlation detection of the desired signal. Next, the distortion component contained in the second signal is removed by controlling the phase and amplitude of this extracted distortion component and adding the result to the second signal. This process is controlled by detecting the correlation between the extracted distortion component and the error component contained in the signal after the addition. This enables compensation for distortion produced at the transmitting side to be performed at the receiving side, whereby the transmitting equipment can be reduced in size.
Inventors
- 👤 Shuta Uwano
- 👤 Kazuji Watanabe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 06:24
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/32; H03F1/3223
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
271 words
Distortion compensator characterised in that it has: pseudo-distortion generator (11) to which is input a digitally multiplexed quadrature phase modulated intermediate frequency signal containing odd order distortion, and through which this intermediate frequency signal passes, and which has been set to be equivalent to the source of the aforementioned odd order distortion; first phase and amplitude varying circuit (12) through which this intermediate frequency signal passes; first adder (19) which essentially subtracts the output of this first phase and amplitude varying circuit from the output of the aforementioned pseudo-distortion generator (11); second phase and amplitude varying circuit (13) through which the output of this first adder passes; second adder (14) which adds the output of this second phase and amplitude varying circuit and the aforementioned intermediate frequency signal so as to eliminate the aforementioned odd order distortion; and error detection circuit (400) which extracts the error component from the output of this second adder; and further characterised in that it also has: first correlation detector (52) which calculates the correlation between the aforementioned intermediate frequency signal and the output of the aforementioned first adder (19), and which controls the amount of phase shift and the amplitude of the aforementioned first phase and amplitude varying circuit (12) so that this correlation is minimized; and second correlation detector (53) which calculates the correlation between the output of the aforementioned first adder (19) and the error component that is output from the aforementioned error detection circuit (400), and which controls the amount of phase shift and the amplitude of the aforementioned second phase and amplitude varying circuit (13) so that this correlation is minimized.
Claim 2
Dependent Claim
174 words
Distortion compensator as set forth in Claim 1, which has first phase demodulator (100) to which the output of the aforementioned second adder is supplied; second phase demodulator (101) to which the aforementioned intermediate frequency signal is supplied; and third phase demodulator (105) to which the output of the aforementioned first adder (19) is supplied; wherein: the aforementioned first correlation detector comprises a means which calculates the correlation between the output of this third phase demodulator (105) and the output of the aforementioned second phase demodulator (101), and which controls the amount of phase shift and the amplitude of the aforementioned first phase and amplitude varying circuit (12) so that this correlation is minimized; and the aforementioned second correlation detector comprises a means which calculates the correlation between the output of the aforementioned third phase demodulator (105) and the output of the aforementioned first phase demodulator (100), and which controls the amount of phase shift and the amplitude of the aforementioned second phase and amplitude varying circuit (13) so that this correlation is minimized.
Claim 3
Dependent Claim
25 words
Distortion compensator as set forth in Claim 2, wherein the aforementioned first and/or the aforementioned second phase and amplitude varying circuit comprises a transversal filter.
Claim 4
Dependent Claim
66 words
Distortion compensator as set forth in Claim 1, which has a first phase demodulator to the input terminal of which is supplied the intermediate frequency signal, and to the output terminals of which are connected the aforementioned first phase and amplitude varying circuit and the aforementioned second adder; and wherein a second phase demodulator is inserted between the aforementioned pseudo-distortion generator and the aforementioned first adder.
Claim 5
Dependent Claim
25 words
Distortion compensator as set forth in Claim 4, wherein the aforementioned first and/or the aforementioned second phase and amplitude varying circuit comprises a transversal filter.
Claim 6
Dependent Claim
71 words
Receiving device which has branch filter (82) to which is input an intermediate frequency signal comprising digitally multiplexed quadrature phase modulated signals that have been frequency multiplexed onto a large number of carriers, said branch filter splitting this input into a digitally multiplexed quadrature phase modulated intermediate frequency signal corresponding to each carrier; wherein a distortion compensator as set forth in any of Claims 1-5 is provided for each respective carrier.
Claim 7
Dependent Claim
33 words
Receiving device as set forth in Claim 6, wherein the pseudo-distortion generator which provides pseudo-distortion for the aforementioned distortion compensator is common to these distortion compensators that are provided for each respective carrier.
Claim 8
Dependent Claim
42 words
Central base station which has optical-to-electrical converter (8) to which is input an optical multiplexed signal, and the electrical signal output of which is connected to the input of aforementioned branch filter (82) of the receiving device set forth in Claim 6.
Claim 9
Dependent Claim
110 words
Radio communication system which has a radio base station device which is connected to a large number of mobile terminals by radio channels, said radio base station device having a frequency converter which converts the signals received from this large number of mobile terminals to intermediate frequencies, and electrical-to-optical converter (5) which converts the intermediate frequency signals output from this frequency converter to optical signals; wherein the optical signal that is output from the aforementioned electrical-to-optical converter (5) is connected, by means of optical transmission line (6), to the input of the aforementioned optical-to-electrical converter (8) which is provided in a central station device as set forth in Claim 8.
References Cited (Backward Citations)
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