Importance

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Abstract

An adaptive signal level detector. The inventive detector includes a first circuit for receiving an input signal and providing a second signal identical to said input signal and delayed relative thereto. The amplitude of the delayed signal is compared to the maximum amplitude of the input signal. When the second signal is at a predetermined level relative to the input signal an output signal is provided. In a specific implementation, the invention (10) includes a first circuit (18) for detecting the signal level of the transmitted signal and providing a second signal in response thereto. The second signal is a logarithmic representation of the input signal The second signal is delayed (20) to provide a third signal. The third signal is subtracted (24) from the second signal to provide a fourth signal. When the fourth signal exceeds a predetermined threshold, an output signal is provided. The invention provides a threshold detection circuit that will detect the instant when the amplitude of the leading or trailing edge of a received pulse crosses a threshold which is a predetermined fraction of the peak pulse amplitude of the received signal independent of the amplitude thereof. The invention enables several different receivers at separate locations to detect the same point on a received pulse signal independently of variations in antenna gain, receiver gain or received signal strength. Because the invention provides measurement independent of pulse amplitude, highly accurate matching of receivers is no longer required. The inventive circuit will greatly enhance the accuracy of comparison of the time of arrival of an transmitted signal at separate receivers.

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First Claim