Microwave pulse generator and pulse-echo ranging system

A microwave transducer head, characterized in that it comprises first and second pulse generators, said pulse generators comprising a semiconductor, having a reverse biased P-N junction, coupled into a microwave resonator, and a trigger circuit incorporating the semiconductor and effective to initiate a transient non-destructive avalanche discharge through said junction of energy stored in the circuit and wherein the semiconductor P-N junction is provided by a small signal silicon junction diode, and means to trigger said pulse generators at a predetermined repetition frequency, the resonators of the pulse generators having approximately the same resonant frequency, an antenna coupled to said resonator of the first pulse generator, and to the resonator of said second pulse generator through a mixer having intermediate frequency output through an amplifier tuned to a specific frequency, the trigger circuit of the second pulse generator being timed to operate subsequent to the trigger circuit of said first pulse generator by a delay which varies linearly for successive pulses to provide an aliased frequency offset between the pulses from the two generators equal to the specific frequency, whereby to cause energy received by said antenna at the frequency of said first generator to be mixed with energy from said second generator by the mixer, to produce a signal at said intermediate frequency output which is a time-stretched alias of signals received by the antenna.

A pulse-echo ranging system, comprising a receiver and echo-processing means for receiving the signal at the intermediate frequency output, identifying a wanted echo therein, and determining the range represented by the delay of the wanted echo, characterized in that the signal is received from a transducer head, said transducer head having first and second pulse generators, said pulse generators comprising a semiconductor, having a reverse biased P-N junction, coupled into a microwave resonator, and a trigger circuit incorporating the semiconductor and effective to initiate a transient non-destructive avalanche discharge through said junction of energy stored in the circuit and wherein the semiconductor P-N junction is provided by a small signal silicon junction diode, and means to trigger said pulse generators at a predetermined repetition frequency, the resonators of the pulse generators having approximately the same resonant frequency, an antenna coupled to said resonator of the first pulse generator, and to the resonator of said second pulse generator through a mixer having intermediate frequency output through an amplifier tuned to a specific frequency, the trigger circuit of the second pulse generator being timed to operate subsequent to the trigger circuit of said first pulse generator by a delay which varies linearly for successive pulses to provide an aliased frequency offset between the pulses from the two generators equal to the specific frequency, whereby to cause energy received by said antenna at the frequency of said first generator to be mixed with energy from said second generator by the mixer, to produce a signal at said intermediate frequency output which is a time-stretched alias of signals received by the antenna, and wherein the trigger circuits for the pulse generators are similar and each includes voltage controlled delay circuits, one having a constant control voltage applied thereto, and the other having a linearly ramped control voltage applied thereto from a ramp generator, and the range is determined on the basis that the wavelength of the received signal is equal to that of the microwave energy generated by the first pulse generator.