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Method and apparatus for reduced intermodulation distortion in a radio transceiver
| Details |
Inventors: Hildebrand, Uwe; Unshelm, Thomas;
Assignee: Telefonaktiebolaget LM Ericsson (publ) (Stockholm, SE)
Primary Examiner: Anderson; Matthew D.
Assistant Examiner: Tran; Tuan
Attorney, Agent or Firm: Nixon & Vanderhye P.C.
A transceiver transmits first and second signals on first and second transmit radio frequencies. After detecting a received signal, intermodulation distortion caused by transmission of the first and second signals is suppressed, reduced, and/or eliminated using information associated with the first and second transmitted signals. More specifically, the information associated with the first and second transmitted signals is used to calculate or otherwise obtain a correction factor that corresponds to the intermodulation distortion. The correction factor is subtracted from the received signal to suppress the intermodulation distortion. |
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DETAILED DESCRIPTION Distortion is a significant problem in telecommunication systems.
While there are several types, distortion generally can be thought of as some modification of a waveform by introducing features not present in the original waveform or by suppressing or modifying features present in the original waveform.
The present invention is particularly concerned with intermodulation distortion.
Intermodulation is the modulation of components of a complex wave by each other producing waves having frequencies, among others, equal to the sums and differences of those components of the original wave.
In other words, intermodulation distortion results from spurious combination-frequency components in the output of a transmission system.
One environment where intermodulation distortion is a problem is in radio base stations used in mobile telecommunications systems.
Such base stations typically include plural transmitters and plural receivers, (i.
e.
, plural transceivers), and may employ a duplexer so that transmitter-receiver pairs can share an antenna for both transmitting and receiving radio frequency signals.
For example, in the well-known GSM 900 mobile communications system, the transmit band covers 35 MHz and includes a 175 transmit frequencies approximately 200 KHz wide.
Unfortunately, transmissions over certain pairs of these 175 transmit frequencies generate significant intermodulation products in the receive band.
As a result, frequency planning methods are required in order to avoid using such frequency pairs.
Another problem is that unused frequency pairs reduce the capacity of the base station.
These problems are overcome by compensating for intermodulation distortion in a received signal caused by transmission of first and second signals on first and second transmit radio frequencies.
In particular, after detecting a received signal, the intermodulation distortion is suppressed, reduced, and/or eliminated using information that is associated with the first and second transmitted signals
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