Dual polarization demodulation with cross polarization cancellation
First Claim
1. A digital signal demodulation system which cancels an interference, in which a common radio frequency is used for both a vertical polarization wave and a horizontal polarization wave, comprising:
- a first demodulator for demodulating a first polarization signal;
a second demodulator for demodulating a second polarization signal;
a first A/D converter coupled with an output of said first demodulator, operating with a clock signal regenerated by said first demodulator;
a second A/D converter coupled with an output of said second demodulator, and said second A/D converter operating with the clock signal regenerated by said first demodulator;
a first transversal filter coupled with an output of said second A/D converter for providing a compensation signal from said second A/D converter output;
a first combiner coupled with an output of said first A/D converter and an output of said first transversal filter;
a first control coupled with an output of said first combiner and the output of said second A/D converter, for adjusting tap coefficients of said first transversal filter; and
an output terminal coupled with the output of said first combiner.
1 Assignment
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Accused Products
Abstract
In a digital demodulation system (FIGS. 2, 3, 4, 7, 8) in a dual polarization radio system, having a first demodulator (4) and a first A/D converter (14) for a main signal, a second demodulator (5) and a second A/D converter (15c) for an interference signal (cross polarization signal), a transversal filter (18) for providing a compensation signal for cancelling an interference component in the main signal depending upon the demodulated interference component; the second A/D converter (15c) for providing the interference component in digital form is operated with a clock signal (102) regenerated in the main signal branch (4, 14) so that system operates correctly even when the main signal and cross polarization signal are in an asynchronous condition. The A/D converter (14, 15c, 105) is provided with an attenuator (104) for compressing amplitude of an input signal to avoid saturation of the circuit (105) in case of fading and/or distortion, and a ROM table (107) for correcting digitalized output after equalization and/or cancellation. Tap coefficients of the transversal filter (18) are obtained by a control (19) through a ZF method when inter-symbol interference is small, and a MLE method when inter-symbol interference is large. Further, an integration constant for the coefficients is adaptive depending upon inter-symbol interference.
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Citations
4 Claims
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1. A digital signal demodulation system which cancels an interference, in which a common radio frequency is used for both a vertical polarization wave and a horizontal polarization wave, comprising:
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a first demodulator for demodulating a first polarization signal; a second demodulator for demodulating a second polarization signal; a first A/D converter coupled with an output of said first demodulator, operating with a clock signal regenerated by said first demodulator; a second A/D converter coupled with an output of said second demodulator, and said second A/D converter operating with the clock signal regenerated by said first demodulator; a first transversal filter coupled with an output of said second A/D converter for providing a compensation signal from said second A/D converter output; a first combiner coupled with an output of said first A/D converter and an output of said first transversal filter; a first control coupled with an output of said first combiner and the output of said second A/D converter, for adjusting tap coefficients of said first transversal filter; and an output terminal coupled with the output of said first combiner. - View Dependent Claims (2, 3, 4)
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Specification