GaAs MESFET-based MMIC VCO with low phase noise performance

We present a fully monolithic X-band MMIC VCO implemented in a GaAs MESFET process. Measurement results demonstrate a single sideband phase noise ratio of -91 dBc/Hz at a 100 KHz offset. This VCO achieves a maximum output power of 11.5 dBm with 550 MHz of frequency tuning range. The output power can be controlled over 12 dB while maintaining excellent phase noise. Second harmonic suppression of 20 dB or more is measured across the entire power and frequency range. This result is comparable to, or better than, the best reported result of VCOs implemented in HEMT and HBT processes.