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Abstract

A diversity signal strength indicator for transmission site selection in a cellular-like mobile radio system produces an output strength indication signal which is proportional to the logarithm of the average strength of two diversity input signals. The two input diversity signals are time multiplexed together to form a composite signal, and a log amplifier/envelope detector then produces an intermediate log signal which is proportional to the logarithm of the envelope of the composite signal. The intermediate log signal is then operated on by a peak detector to produce a peak intermediate log signal which is then passed through a low pass filter to produce an output strength detection signal proportional to the average of the intermediate log signal and thus proportional to the logarithm of the average strength of the diversity input signal. The peak detector is preferably comprised of a capacitor charged through a diode for storing the peak levels of the intermediate log signal and a current source for draining the charge on the capacitor at a substantially uniform rate which is independent of the magnitude of the peak signal which is stored during time periods between peak signals. In another embodiment, the time multiplexed composite signal is first detected and then passed through a squaring circuit, a low pass filter and then a log amplifier to produce an output indicator circuit proportional to the logarithm of the average strength of the input diversity signals. The diversity signal strength indicator is employed in combination with a site selection system for selecting suitable ones of a plurality of transceiver sites for actuation and reception of signals to be transmitted to a remote portable unit.

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