DETECTING INTERMODULATION DISTORTION IN A RADIO FREQUENCY RECEIVER

A radio frequency receiver (300) typically contains electronic devices commonly used in amplifying or mixing circuits (315), (339), the non-ideal characteristics of which lead to intermodulation (IM) distortion. A measurement of the amplitude of the received signal (301) is taken both unattenuated and attenuated. The difference between the two measurements is compared to predetermined limits wherein the received signal (301) 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 attempting to gain access to the system provider in which it is registered.