Mode-coupled stubs-tuned planar resonator based spectral pure signal source for wireless communication systems

A novel compact coupled planar resonator (CCPR) based VCO (voltage controlled oscillator) using mode-coupling technique was developed in response to expensive high Ceramic and SAW resonators based signal source for wireless communications. One of the problems related to the conventional Ceramic/SAW based resonators (with high Q and low phase noise) is the challenge for integration in IC form. Instead of employing the distributed planar uncoupled transmission line resonator for integration that exhibits low Q and high phase noise, this work describes a CCPR based VCO that supports user-definable frequency band in compact size and amenable for integration in the IC form. The measured phase noise for a carrier frequency 622 MHz is better than -135 dBc/Hz at 10 kHz offset, and to our knowledge, this is the best phase noise performance for this class of VCOs using printed resonator in 0.5'times0.5' circuit board size so far reported. The reported topology is not limited to this frequency, can be extended for other higher frequency by incorporating mode-injection stubs across the CCPR for desired operating frequency.