Apparatus and method for detecting intermodulation distortion in

Details Apparatus and method for detecting intermodulation distortion in Apparatus and method for detecting intermodulation distortion in

1991-07-26

1994-06-14

Eisenzopf, Reinhard J.

Telecommunications

Transmitter and receiver at separate stations

Distortion, noise, or other interference prevention,...

455295, 455303, 455308, 455310, 375102, H04B 126

Patent

active

053218477

ABSTRACT:
A radio frequency receiver (300) typically contains electronic devices commonly used in amplifying or mixing circuits (315) which are seldom ideal. The non-ideal characteristics of these devices lead to intermodulation (IM) distortion. A measurement of the amplitude of the received signal (301) is taken both unattenuated (503) and attenuated (507). The difference between the two measurements is compared (511) to predetermined limits (L1, L2 or L3) wherein the received signal (310) is determined to be valid, invalid or unsure. A valid received signal is demodulated in the receiver (300). An invalid signal, confirming the presence of IM distortion, is rejected. The unsure signal may be rejected or demodulated as determined by the receiver designer. This type of signal characterization is particularly useful for cellular radiotelephones (101) attempting to gain access to the system provider (111) in which it is registered.

REFERENCES:
patent: 4126828 (1978-11-01), Kumagai
patent: 4430619 (1984-02-01), Epsom et al.
patent: 4955073 (1990-09-01), Sugayama
patent: 5170392 (1992-12-01), Riordan
Electronic Industries Association (EIA)-553 Mobile Station-Land Station Compatibility Specification. Sep. 1989.
Technical Paper entitled, "Intercept Point and Undesired Responses", by Richard C. Sagers, in care of Motorola, Inc., and presented before the 32nd IEEE Vehicular Technology conference, May 23-25, 1982.

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