A low phase-noise VCO for multi-band transceiver using fully packaged MEMS electrostatic varactors

This paper reports the low-phase noise performance of the VCO (Voltage Controlled Oscillator) using the digital MEMS varactors with the MIM (Metal-Insulator-Metal) capacitors and an electrostatically actuated contact switch. A packaged 2-bit MEMS varactor was operated at 35 V dc to alter the capacitor values in four different states ranging from 0.55 pF to 0.73 pF with a 0.06-pF-step at 1 GHz. A 2-bit MEMS-VCO module was also assembled by using the MEMS chip on the high frequency PWB (Printed Wiring Board, 40 mm × 35 mm). Due to the digital operation, the free-running oscillation frequency was controlled in between 802 MHz to 822 MHz. A phase noise level was measured on a 1-bit MEMS VCO module to be as low as -101 dBc/Hz at a 10 kHz offset from the peak frequency 776 MHz.