Advances in mechanically tuned, frequency agile, coaxial magnetrons

Magnetron oscillators with pulse to pulse frequency agility are used in radar service to provide ECCM capability and to provide target signal enhancement by reduction of glint and clutter return signals. A family of frequency agile coaxial magnetrons called "dither-tuned" tubes has been developed for this service. They are tuned by a motor driven eccentric or cam connected to the oscillator cavity tuner. Initial 200 kilowatt peak power, X band tubes of this class operated with a near sinusoidal frequency tuning mode over typical tuning ranges of 40 to 80 MHz at 75 Hz tuning rates. A readout voltage signal related to the oscillator frequency for slaving the receiver local oscillator to the transmitter was derived from a resolver directly coupled to the shaft of the eccentric. The resolver is a transformer with a rotating secondary winding. 100 KHz AC voltage applied to the primary produces an output AC voltage proportional to the angular position of the eccentric and hence the tuner position and frequency.