SAW-resonator stabilized voltage-controlled-oscillator for PLL-FM modulator

A voltage controlled oscillator using a SAW resonator does not need multiplication and tuning in the 100 MHz - UHF band so that miniaturization and circuit simplification can be achieved. It also has the feature that less power is dissipated than with a SAW delay line. In this paper the SAW resonator voltage-controlled oscillator (SAWR-VCO) is used as a modulator suitable for a phase locked loop (PLL) and its modulation sensitivity and distortion are analyzed. Tests confirm the analysis of SAWR-VCO performance. Finally a PLL modulator structure and the modulator circuit for use in an automotive mobile telephone unit is described.