Front end processor for data receiver and nonlinear distortion equalization method
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsMikihiro Ouchi, Ippei Kanno, Hisaya Kato
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Abstract
An OFDM baseband signal that has undergone a synchronization carrier modulation or a differential carrier modulation is inputted to a complex signal converter for nonlinear distortion equalization so as to be converted according to the N-th order function conversion characteristics (N>1). Then, nonlinear distortion in the OFDM baseband signal is compensated for. At this time, the following is used as a conversion equation: y(n)=x(n)+Σam(n)xm(n)(m>1) wherein the values of the input signal, the output signal and the coefficient for m-th order distortion equalization at time n are, respectively, x(n), y(n) and am(n).
Claims39
A front end processor for a data receiver which receives a digital modulation signal that has been amplified in a saturated region during either the process of transmission or of reception, comprising:
- a quadrature detector which receives data train of modulated digital signal, and converts said data into a complex base band signal x(n) with quadrature detecting;
- and
- a nonlinear distortion equalizer which calculates a signal y(n) by using a coefficient am(n) for m-th order distortion equalization (m is an arbitrary natural number) so as to remove m-th order distortion included in said complex baseband signal x(n), which calculates a signal s(n), of which the phase synchronization is established, from said signal y(n) and which calculates an error signal between said signal s(n) and the closest mapping point d(n), wherein said front end processor for a data receiver updates the value of said coefficient am(n) for m-th order distortion equalization so that said error signal becomes of the minimum.
A nonlinear distortion equalization method which compensates for waveform distortion in a complex input signal, comprising the following steps of:
- converting a complex input signal to a complex signal for non linear distortion compensation according to the N-th function conversion characteristics (N>1);
- low pass filtering to allow only the low frequency components of the output of said complex signal for nonlinear distortion equalization to pass;
- reproducing a carrier wave to establish the phase synchronization of the output of said low pass filtering;
- calculating an error signal between the output of said carrier wave reproduction step and an ideal reception point;
- and
- updating coefficient of said N-th power function conversion characteristics, with using said error signal and correcting the phase rotation in said carrier wave reproduction step,
- wherein a conversion equation of said N-th function conversion characteristics is formed as:
- y(n)=x(n)+Σam(n)xm(n)(m>1)
- where the values of the input signal, the output signal and the coefficient for m-th order distortion equalization at time n are, respectively, x(n), y(n) and am(n), and
- a conversion equation of said N-th function conversion characteristics and a coefficient update equation are formed as:
- xm(n)=|xm−1(n)|x(n).
A nonlinear distortion equalization method which compensates for waveform distortion in an OFDM baseband signal that has undergone a synchronization carrier modulation, comprising the following steps of:
- converting an OFDM baseband signal that has undergone a synchronization carrier modulation to a nonlinear distortion equalization signal according to the N-th function conversion characteristics (N>1);
- carrying out an FFT conversion on said nonlinear equalization signal;
- carrying out synchronization demodulation processing of the output of said FFT processing;
- calculating an error signal from the output of said synchronization demodulation processing and an ideal reception point;
- and
- updating coefficient of said N-th function conversion characteristics by using said error signal,
- wherein the conversion equation of said N-th function conversion characteristics is formed as:
- y(n)=x(n)+Σam(n)xm(n)(m>1)
- where the values of the input signal, the output signal and the coefficient for m-th power distortion equalization at time n are, respectively, x(n), y(n) and am(n);
- and
- the conversion equation of said N-th function conversion characteristics and the coefficient update equation are formed as:
- xm(n)=|xm−1(n)|x(n);
- and
- wherein said synchronization demodulation step includes the following steps of:
- calculating the transmission path characteristics H(k) the output of said FFT processing;
- and dividing output of said FFT processing by H(k) so as to carry out a synchronization demodulation.
A nonlinear distortion equalization method which compensates for waveform distortion in an OFDM baseband signal that has undergone a differential carrier modulation, comprising the following steps of;
- converting an OFDM baseband signal that has undergone a differential carrier modulation to a nonlinear distortion equalization signal according to the N-th function conversion characteristics (N>1);
- FFT processing so as to carry out an FFT conversion on said nonlinear distortion equalization signal;
- carrying out differential demodulation processing using an output of said FFT processing and a signal gained by delaying the output of said FFT processing by one OFDM symbol;
- calculating an error signal between the output of said differential demodulation processing and an ideal reception point;
- and
- updating the coefficient of said N-th function conversion characteristics by using said error signal,
- wherein the conversion equation of said N-th function conversion characteristics is:
- y(n)=x(n)+Σam(n)xm(n)(m>1)
- where the values of the input signal, the output signal and the coefficient for m-th order distortion equalization at time n are, respectively, x(n), y(n) and am(n);
- and
- the conversion equation of said N-th function conversion characteristics and the coefficient update equation are formed as:
- xm(n)=|xm−1(n)|x(n);
- and
- wherein said a differential processing demodulation is carried out by dividing the output of said FFT processing by a signal, which is gained by delaying the output of said FFT processing by said one OFDM symbol.
A nonlinear distortion equalization method which compensates for waveform distortion in an OFDM baseband signal that has undergone a differential carrier modulation, comprising the following steps of:
- converting an OFDM baseband signal that has undergone a differential carrier modulation to a nonlinear distortion equalization signal according to the N-th function conversion characteristics (N>1);
- FFT processing so as to carry out an FFT conversion on said nonlinear distortion equalization signal;
- carrying out differential demodulation processing using an output of said FFT processing and a signal gained by delaying the output of said FFT processing by one OFDM symbol;
- calculating an error signal between the output of said differential demodulation processing and an ideal reception point;
- updating the coefficient of said N-th function conversion characteristics by using said error signal, wherein the conversion equation of said N-th function conversion characteristics is:
- y(n)=x(n)+Σam(n)xm(n)(m>1)
- where the values of the input signal, the output signal and the coefficient for m-th order distortion equalization at time n are, respectively, x(n), y(n) and am(n);
- and
- the conversion equation of said N-th function conversion characteristics and the coefficient update equation are formed as:
- xm(n)=|xm−1(n)|x(n);
- and
- wherein said differential demodulation processing is carried out by multiplying the complex conjugate of a signal, which is gained by delaying the output of said FFT process by said one OFDM symbol, by the output of said FFT process in said differential demodulation processing.
Dependencies are inferred from the claim text.