A high-performance 2.488 GHz surface transverse wave based voltage controlled oscillator without using submicron geometries

A simple, low-noise 2.488 GHz voltage controlled oscillator (VCO) circuit, stabilized with a 1.244 GHz two-port surface transverse wave resonator (STWR) and using frequency doubling is presented. Since no submicron fabrication for the STWR and no expensive parts are required, the VCO can be fabricated at a low cost and is suitable for series production. Phase noise is minimized by reducing the active parts to one transistor and two varactors in the sustaining amplifier, optimizing the bias and excess gain and implementing an external limiter also used as a frequency doubler. We found that, compared to class-A operation, up to 15 dB improvement in close-in phase noise is achieved if the sustaining amplifier transistor is biased for class-C steady state oscillator operation. The VCO draws 14 mA of current from a 3.3 V DC power source, provides 0 dBm of RF power and 310 ppm tuning range with a tuning voltage varied from 0 to +3.3 V. The laboratory prototypes demonstrate a phase noise suppression of -112 dBc/Hz at 1 kHz offset from carrier and their temperature stability is within 100 ppm over the temperature range -20 to +70 deg. C.