The Effect of Real-Time Radar Transmitter Amplifier Impedance Tuning on Range and Doppler Detection Accuracy

Radar transmitter power amplifiers with tunable matching networks, designed to allow real-time spectrum flexibility, may require hundreds of milliseconds to reconfigure; which is typically a significantly longer duration than the coherent processing interval (CPI) of a radar. As such, it is desirable to perform accurate radar detection during the reconfiguration. The tuning operation, however, may affect the Doppler detection accuracy, due to the change in the tuner transmission phase during the measurement. Since Doppler error is proportional to the speed with which a mechanical tuning element is moved, fast tuners can cause significant impact on Doppler detection accuracy. Measurement results with a 90 W reconfigurable evanescent-mode cavity impedance tuner on the transmitter are presented for detection during reconfiguration, and approaches for ensuring accurate radar detection while reconfiguring are discussed.