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.