Abstract

There is nowadays a strong demand for microwaves of oxceptionaly high spectral purity. A straight-forward example of the importance of such microwaves can be encountered in radar technology. Radars are commonly divided into two categories: pulsed radars, which can determine the distance of a target with the delay-time of a microwave pulse’s echo; and continuous-wave radars, which are rather suitable for the evaluation of velocities, as they measure Doppler shifts induced by moving targets. However, very accurate measure of these Doppler shifts is possible only when the emitted microwave is very pure, that is. almost free of phase noise. However the purity of the microwaves generated by electronic circuitry has significant limitations.

© 2007 IEEE