International Journal of Engineering and Technology

A coherent study of tuning properties of resonantcap IMPATT oscillator at Ka-band has been carried out by mechanical and electronic means. It is experimentally observed that output power of IMPATT oscillator passes through a maximum, with an optimum combination of cap diameter and cap height. An empirical relation is obtained between cap diameter and wavelength of the optimised resonant cap oscillator, which agrees well with theoretical relation. Electronic tuning is carried out by varying the dc bias current with the optimized cavity parameters. It is observed that the variations of oscillation frequency and power output with dc bias current are characterised by three ranges of bias current. The effect of sliding short tuner position on the performance of the oscillator at optimised condition has also been studied. Finally, the injection locking of the free running oscillator has been studied with a Ka-band signal generator as a reference source. The injection locked IMPATT oscillator shows a good phase noise performance.