Nonlinear distortion compensating receiver and nonlinear distortion compensation method
Disclosed are a nonlinear distortion compensating receiver and nonlinear distortion compensation method, wherein nonlinear distortion is reduced with a simple circuit configuration. A correction (opposite characteristics) filter ( 104 ) has characteristics opposite that of the frequency characteristics of a direct sampling mixer ( 102 ) and corrects signals sampled by the direct sampling mixer ( 102 ). In the main path, a LPF ( 106 ) extracts a frequency band component of a desired signal from the corrected signal. In the replica path, a BPF ( 107 ) extracts the frequency band component of a blocker signal from the corrected signal. A cubing circuit ( 108 ) uses the frequency band component of the blocker signal to generate a replica signal for the nonlinear distortion. An adaptive filter ( 110 ) performs filter processing on the replica signal while updating the filter coefficients. A subtractor ( 111 ) subtracts the output signal of the adaptive filter ( 110 ) from the frequency band component of the extracted desired signal and outputs the subtraction result as the desired signal.
1. A nonlinear distortion compensation receiver comprising:
a sampling mixer that samples an input signal by frequency-converting and band-limiting the input signal;
a correction filter that has an inverse characteristic of a frequency characteristic of the sampling mixer, corrects the frequency characteristic of a signal that is sampled by the sampling mixer, and outputs the corrected signal as a correction signal;
a main signal extracting section that extracts a main path signal including a frequency band component of a desired wave from the correction signal;
a replica signal generation section that extracts a frequency band component of an interfering wave from the correction signal as a replica path signal, and generates a replica signal of a nonlinear distortion component generated in the sampling mixer by using the frequency band component of the extracted interfering wave;
an adaptive filter that performs adaptive filter processing to the replica signal with updating a filter coefficient; and
a subtraction section that subtracts an output signal of the adaptive filter from the main path signal extracted by the main signal extracting section and outputs a subtracted result as a desired wave signal,
wherein the adaptive filter updates the filter coefficient based on an output signal of the subtraction section.
2. The nonlinear distortion compensation receiver according to claim 1 , wherein the nonlinear distortion compensation receiver is a low intermediate frequency type receiver, the nonlinear distortion compensation receiver further comprising a conversion section that frequency-converts the correction signal into a zero IF, at a rear stage of the correction filter.
3. The nonlinear distortion compensation receiver according to claim 1 , wherein
the generation section generates a replica signal of n-th order distortion as the replica signal, n being an integer that equals or exceeds two; and
the adaptive filter performs the adaptive filter processing to replica signals of the n-th order distortion.
4. The nonlinear distortion compensation receiver according to claim 1 , wherein the signal sampled by the sampling mixer is a complex signal formed by an in-phase signal and a quadrature signal.
5. The nonlinear distortion compensation receiver according to claim 1 , further comprising a conversion section where the input signal is an orthogonal frequency division multiplexing signal, and that is provided in the rear stage of the correction filter, fast-Fourier-transforms an output signal of the correction filter, and outputs a Fourier-transformed signal, wherein:
the main signal extracting section extracts the main path signal from the Fourier-transformed signal; and
the replica signal generation section generates the replica signal from the Fourier-transformed signal.
6. The nonlinear distortion compensation receiver according to claim 1 , wherein the correction filter can adaptively update the filter coefficient.
7. A nonlinear distortion compensation method comprising:
sampling an input signal by frequency-converting and band-limiting the input signal;
correcting a frequency characteristic of the signal that is sampled by the sampling, and outputting the corrected signal as a correction signal by using an inverse characteristic of the frequency characteristic of sampling processing;
extracting a main path signal including a frequency band component of a desired wave from the correction signal;
extracting a frequency band component of an interfering wave from the correction signal as a replica path signal and generating a replica signal of a nonlinear distortion component generated in the sampling processing by using the frequency band component of the extracted interfering wave;
performing adaptive filter processing to the replica signal with updating a filter coefficient; and
subtracting the replica signal where the adaptive filter processing is performed, from the extracted main path signal, and outputting a subtracted result as a desired wave signal,
wherein the adaptive filter processing updates the filter coefficient based on a signal that shows the subtracted result.