Abstract: The present invention provides a covert radar system in which radar signals emitted are capable to search receiver thermal noise and, therefore, are substantially undetectable in the normal radar operating range.

Abstract: A radar ranging system is disclosed which employs a frequency modulated and phase coded transmission signal which can have up to a 100 percent duty cycle and which performs time tracking of the radar target and does not require extreme accuracy in frequency modulation, or extreme receiving antenna to transmit antenna isolation.

Abstract: A high frequency signal is converted to a signal characteristic of two simultaneously present, closely spaced high frequency signals. A high frequency signal is passed through a controllable bi-phase modulating switch. The switch is controlled by the resultant output of a multiplier which multiplies the sign of two phase-related pulse trains.

Abstract: A pulsed coherent radar altimeter is described which employs a narrow band receiver and utilizes a novel digital coherent pulse generator. A coherent pulse radar transmits a pulse comprised of the sum of at least two phase related RF signals closely spaced in frequency. The phase shift due to platform motion and return surface irregularity of the return signal is approximately the same for each carrier. The receiver produces a signal representative of the difference of the two carriers which is substantially free of decorrelation effects, and which can be processed in a narrow band receiver to produce range information.

Abstract: A digital pulse compression radar system with interrupted, phase coded, high duty ratio transmissions which allow contiguous range resolution cells to be established in coverage space and provide adequate airframe impulse excitation recovery time to render high duty ratio, phase coded, radar feasible for airborne applications.Each pulse is subdivided into a predetermined number of subpulses or bits, which are phase coded with (in-phase or out-of-phase) reference to a master oscillator. In the preferred embodiment, the code is built up from a PRN code staggered over .sup.2 n-1 pulses, each containing m resolution elements, where n is an arbitrary number designating the degree of the code and where m is an arbitrary number or is equal to the number of bits per pulse. The correlation properties of the code are such that when all bits of the returned pulses representing a word align with the delayed transmitted word, all bits add. When the bits do not align precisely, the bits generally cancel each other.

Abstract: A microwave radar type of intruder detection system incorporating signal sensing, storing and comparison logic which enables the system to self-adapt to any preselected environment and produce a signal in the event of a predetermined change from the ambient conditions of the preselected environment.