Abstract: A transmit system for collision avoidance systems having autocalibration. A four element antenna array is provided. Each element is selectively connectable to a transmitter through a power divider and a isolator. Three of the elements further have a programmable phase shifter in line to the transmitter. A phase detector having a first input selectably connectable to one of the elements and a second output connected to the transmitter is provided. By selectively connecting one element to the transmitter and one element to the phase detector and then selectively programming the appropriate phase shifters, the differentiated phase delay in each channel of components associated with an antenna element can be calibrated.

Abstract: The invention comprises a weather radar system in which a magnetron transmitter is controlled in frequency by injecting therein a low power locking signal from a stable frequency source. Frequency lock between the source and the magnetron is maintained without requiring injection signals of excessive power by an automatic frequency control (AFC). The AFC determines the frequency and phase error between the injection signal and the magnetron output and adjusts the frequency of the source so as always to be within a narrow band of frequencies centered about the natural frequency of the magnetron. Over the long term, therefore, the frequency of the source will vary by an amount equal to the change in the natural frequency of the magnetron occurring during that time. Over the short term, however, the difference in frequency between the injection signal and the magnetron output is zero, while the phase difference is less than 90.degree..