US 2006/0215775 A1 · Digital cancellation of radio frequency interference

Abstract

A method and system of canceling radio frequency interference (RFI) sourced from a narrow-band radio frequency transmitter to interfere with the operation of a multi-carrier modulation system. The spectral components of the RFI can be represented as a Taylor series of 1/(m−1/2) where m is an integer and (m−1/2) is a normalized approximate distance between the frequency of interest and the center frequency of the RFI. The coefficients of the Taylor series are obtained by solving a set of linear equations using the Fourier output at several properly chosen frequencies where the RFI components dominate. The coefficients for the Taylor series are formulated as linear combinations of the FFT output at the chosen frequencies and are computed and stored beforehand. Simple multiplications and additions are needed for obtaining the Taylor series coefficients from the FFT output at the chosen frequencies. The coefficients of the Taylor series can be obtained for any frequency, and the spectral component of the RFI can be estimated and removed from the MCM signals.

Claims19

Dependent claims

A method of estimating a spectral component of interference at a particular frequency, comprising:

selecting a frequency of interest from a first plurality of frequencies in a frequency band;
generating the frequency domain data for the first plurality of frequencies;
determining whether there is interference at any one of the first plurality of frequencies;
determining the peak output of the frequency domain data at a location in the frequency band where the interference spectral components dominate;
selecting the frequency domain data from a second plurality of frequencies near the spectral peak of the interference among the first plurality of frequencies;
obtaining a first set of coefficients using linear combinations of the frequency domain data of the second plurality of frequencies using a second set of coefficients that are pre-computed and stored in a look-up table;
and quantifying the interference component at the frequency of interest using a Taylor series on the reciprocal of the spectral distance between the frequency of interest and the spectral peak of the interference using the first set of coefficients.

4 more elements

A method of estimating a spectral component of interference at a particular frequency, comprising:

selecting a frequency of interest from a first plurality of frequencies in a frequency band;
generating the frequency domain data for the first plurality of frequencies;
determining the peak output of the frequency domain data at a location in the frequency band where radio frequency interference spectral components dominate;
selecting the frequency domain data from a second plurality of frequencies near the spectral peak of the radio interference among the first plurality of frequencies;
and
obtaining the interference component at the frequency of interest using a linear combination of the frequency domain data from the second plurality of frequencies using a set of pre-computed coefficients.

3 more elements

A system comprising:

a receiver for receiving and processing analog signals;
an analog-to-digital converter connected to the receiver to convert the analog signals into a first sequence of digital samples;
a time-domain windowing function to select and process a portion of the first sequence of digital samples and generate a second sequence of digital samples;
a discrete-time to discrete-frequency transformer connected to receive the second sequence of digital samples and to convert them into a set of frequency domain data;
and
an interference canceller connected to the discrete-time to discrete-frequency transformer to remove the interference contribution by computing the interference component at the frequency of interest by calculating a linear combination of the frequency domain data from a plurality of frequencies using a set of pre-computed coefficients.

3 more elements

Dependencies are inferred from the claim text.

Digital cancellation of radio frequency interference

Life of this patent

Digital cancellation of radio frequency interference

Life of this patent

Abstract

Claims19