15-GHz-band low-power and low phase-noise LC VCO IC with a second harmonic filter in 130-nm SiGe BiCMOS

In this paper, a second harmonic filtering technique is presented for improvement of phase noise performance of a Class-C LC-VCO IC. The second harmonic filter is employed to terminate the output port of the LC-VCO in low impedance at second harmonic frequency, which mainly prevents the noise modulated by the transistor nonlinearities. In addition, since the impedance of the second harmonic filter becomes capacitive at the fundamental frequency, the phase-noise performance is improved. Class-C operation is also effective for less power and better phase-noise performance. The LC-VCO IC was fabricated and evaluated in 130-nm SiGe BiCMOS technology. The LC-VCO IC has presented a measured phase noise of -118.1 dBc/Hz at 5 MHz offset from the 15.2 GHz carrier frequency with a dc power consumption of about 2.25 mW.