Method and apparatus for canceling a transmit signal spectrum in a receiver bandwidth

Abstract

A method and apparatus for attenuating a transmit signal spectrum in a receiver bandwidth. The apparatus relates to an adaptive, digital, coherent, spectral canceller. The method comprises digitizing both a corrupted receiver signal and a reference transmit signal and then digitally implementing an adaptive coherent spectral canceller module to suppress a residue transmit spectral signal power within the receiver bandwidth.

Description

CLAIM OF PRIORITY[0001] This application is a continuation of, and claims priority from U.S. patent application Ser. No. 09 / 487,396, filed Jan. 18, 2000, which is incorporated in its entirety by reference herein.[0002] 1. Field of the Invention[0003] The present invention relates to wireless communications. More specifically, the invention relates to canceling transmitter signal energy in a receiver bandwidth.[0004] 2. Description of the Related Art[0005] There is a growing need for low cost, high performance radio transceivers that can operate in a full duplex mode in support of such applications as code division multiple access (CDMA), global system for mobile communications (GSM) and time division multiple access (TDMA) remote units and base stations.[0006] Currently, a standard transceiver comprises a transmitter, a receiver and a duplexer. One problem with standard transceivers is some of the transmit signal leaks into the receiver, which corrupts the received signal processed ...

AI Technical Summary

Problems solved by technology

One problem with standard transceivers is some of the transmit signal leaks into the receiver, which corrupts the received signal processed by the receiver.

Imperfect duplexers create two problems.

A second problem is noise from the transmitter leaks into the receiver and raises its noise figure.

These changes, however, are undesirable from the standpoint of transmitter efficiency.

Automatic gain control used to extend the dynamic range of a receiver may be undesirable for spectrally crowded applications such as cellular communications because the automatic gain control may make the receiver sensitivity dependent upon signals and interference that are outside the signal channel.

For example, it is possible for a strong signal in an adjacent channel to capture the receiver front end desensitize the receiver such that a weak signal in the channel of interest is undetectable.

This is particularly harmful in a base station receiver where the receiver receives incoming signals from multiple remote units.

Furthermore, the use of automatic gain control will likely require the digital coherent canceller to track the gain changes which will introduce errors and noise.

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