An 11.5 GHz Cascode VCO with Low Phase Noise in InGaP/GaAs HBT Technology

A MMIC cascode VCO is designed, fabricated, and characterized for an X-band Low Noise Block(LNB) system using InGaP/GaAs HBT technology. A phase noise of -116.4 dBc/ Hz at an offset frequency of 1 MHz and an output power of 1.3 dBm is obtained at 11.526 GHz using a 3 V bias and a current consumption of 11 mA. The characteristics of this VCO are comparatively better than those with the different VCO configurations fabricated with other technologies. Also, simulated oscillation frequency and second harmonic suppression agree with the measured results. And, phase noise is improved due to the use of the small value of series resistor of inductor in frequency determining network plus the InGaP ledge in the HBT. The chip size is 830 x 781μm 2.