Interference cancellation in an OFDM receiver

A receiver, interference signal technology, applied in the field of interference caused by nonlinear distortion, can solve problems such as proportional interference of second-order intermodulation

Inactive Publication Date: 2011-11-23
TELEFON AB LM ERICSSON (PUBL)
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  • Abstract
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Problems solved by technology

Both direct second-order intermodulation and the latter mechanism produce int...

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  • Interference cancellation in an OFDM receiver
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  • Interference cancellation in an OFDM receiver

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Embodiment Construction

[0021] A homodyne or direct conversion receiver can be considered a variant of a traditional superheterodyne receiver. Generally, a superheterodyne receiver receives a signal in a first frequency band and mixes the received signal with a locally generated oscillator signal to convert it to a second or intermediate frequency (IF) band. By choosing the local oscillator frequency a constant amount away from the desired signal in the first frequency band, the desired signal always appears at the same frequency in the IF band, facilitating selection by a fixed tuned IF filter.

[0022] In the homodyne variant, the selected "mid" frequency band is DC or zero frequency. The local oscillator must then be tuned to the center of the desired received signal. At the mixer output, the modulation of the desired signal (typically manifested as spectral components above and below the center frequency of the desired signal) is "folded." Thus, signal components at a frequency offset Δf above ...

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Abstract

Circuits and methods are disclosed for compensating for received signal distortion caused by non-linearittes in wideband receivers. An exemplary receiver includes a distortion waveform generator (106) configured to approximate non-linear response characteristics of a downconverter circuit (104a-b, 105) used to downconvert the received radio frequency signal. The resulting estimated distortion waveform is filtered, using filter(s) (107c) substantially similar to those used for filtering an intermediate frequency signal that includes the desired signal and non-linear distortion products caused by strong interfering signals. The filtered estimated distortion waveform and intermediate frequency signal are sampled, to obtain a sampled distortion signal and a sampled signal of interest. The sampled distortion signal and the sampled signal of interest are divided into a plurality of frequency channels. For a selected number of frequency channels, the sampled distortion signal for a frequency channel is scaled, and subtracted from the corresponding sampled signal of interest for the same frequency channel to obtain reduced-interference signal samples for the frequency channel.

Description

technical field [0001] The present invention relates generally to wireless receiver systems and, in particular, to methods and apparatus for suppressing interference in such receivers due to non-linear distortion from strong interfering signals. Background technique [0002] In the field of wireless receivers, efforts are constantly being made to minimize the amount of tuning circuitry used. By reducing the number of tuned circuits, a larger portion of the receiver can be integrated, resulting in a smaller and often cheaper device. This effort has led to widespread interest in homodyne receivers (also known as direct conversion receivers) and low-IF or near-zero IF receivers. [0003] A well-known and common disadvantage of some prior art homodyne and low intermediate frequency receivers is susceptibility to strong interfering signals. A typical front-end circuit for a wireless receiver includes a filter immediately after the antenna input, the bandwidth of which filter is...

Claims

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Application Information

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IPC IPC(8): H04B1/12H04B1/30
CPCH04B1/123H04L27/2647H04B1/30
Inventor 保罗·W·登特斯文·马特森
Owner TELEFON AB LM ERICSSON (PUBL)
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