Method for transmitting and receiving radar signals while blocking reception of self generated signals

A method which enables facilities, such as ships, airplanes, and land based sites, to transmit and receive radar signals to receive any incoming radar signal, while blocking reception of any signals generated by the facility itself, comprising:

• transmitting a primary rf signal of frequency f, that is continuous, or modulated by a lower frequency modulation than a carrier frequency f;
• relaying said signal to a transmitting antenna where it is transmitted and an unwanted signal is detected by the facilities receiving antenna and transported to a detector;
• generating a secondary signal which has the same carrier frequency and modulations as the primary signal and such that the carrier signal maintains a fixed phase relationship with the primary signal, by means of splitting off a fraction of the primary signal before the transmitting antenna, or by generating such a signal from a second rf generator synchronized to said primary signal, in frequency, phase and amplitude;
• and,
• relaying said secondary signal through components including a voltage controlled attenuator and a voltage controlled phase shifter, to adjust the amplitude and phase, to a place, at or between the receiving antenna and the detector, where it is added to the primary signal, after its amplitude has been adjusted to equal that of the primary signal, and its phase shifted so it is 180 degrees out of phase with the primary signal at the addition point;
• the signals will then sum to zero and will not affect the detector, it being crucial that a part of the secondary signal be transmitted by the primary transmission antenna and, if any other antennae be used in the transportation of the secondary beam the radiated secondary signal be contained so as not to interfere with the primary beam anywhere except to the place or the immediate vicinity of the place where the signals are added;
• the secondary signal is transported using a cable or waveguide and is added in a coupler to the primary signal from the receiving antenna for which, the same transport mechanism is provided between the receiving antenna and the detector.