The range (R) to a target (12) is precisely determined by controlling the amplitude of the carrier before modulation using a feedback signal derived from the detected return. The amplitude of the carrier is adjusted (40) so that all return pulses have a constant amplitude. Hence, for any given range, all return pulses cross threshold at the same time, thereby eliminating ranging errors due to phase distortion. The return pulses are threshold detected (54) and converted to a CW signal, which is then down converted. The phase information, which is indicative of target range, is preserved in the down conversion process and is extracted by phase comparison (72) with a reference signal to determine the target range.
A pulse detection system for expanded time radar, laser and TDR sensors detects specific cycles within bursts of cycles. A sensor transmits and receives short bursts of RF cycles. A transmit pulse detector triggers on a selected cycle of the detected transmit burst and starts a range counter. A receive detector triggers on a selected cycle within a received echo burst to stop the range counter, thereby indicating range. Cycle selection is enabled by an analysis window of time. The detection system can provide accuracies on the order of one picosecond and is well-suited to accurate ranging along an electromagnetic guide wire.
A system is provided for determining range to a wave energy source. The system includes a transmitter for transmitting a burst of pulses of wave energy in response to a trigger signal. A receiver is provided for determining a time of arrival of the burst and from such determined time of arrival, the range to the wave energy source. The receiver includes: an envelope detector for detecting an envelope of the burst; a network for producing an output in response to an early point on the detected envelope occurring prior to a peak in the detected envelope; a timer, responsive to the trigger signal and the network output for determining the time of arrival of the burst; and a processor, responsive to such determined time of arrival, for determining the range of the wave energy source from the transmitter. The receiver includes a differentiator network for producing an output in response to the nth derivative of the detected envelope, where n is an integer greater than one; and, the timer is responsive to the trigger signal and the differentiator output for determining the time of arrival of the burst. The receiver also includes a means for confirming detection of a valid burst after the detection of the early point and a means to transmit and wherein the previously recorded time of arrival point only if it is followed by a valid burst confirmation.
A system and method for measuring a parameter of a target in accordance with embodiments of the present invention includes transmitting at least one signal towards a target and receiving at least a portion of the transmitted signal back from the target. The measured parameter is one of distance velocity, or reflectivity. The transmitted signal is of the coherent burst waveform, and upon reception is processed with equivalent time sampling, AGC with minimal, if any, error, and a discrete Fourier transform.
