Wide band low phase noise QVCO based on superharmonic injection locking

A wide band, injection-coupled LC quadrature voltage control oscillator is presented. In the proposed circuit, two oscillators are injection locked by coupling their second-order harmonics in anti-phase, forcing the outputs of two oscillators into a quadrature phase state. As the common-mode point sampling the second harmonic frequency, flicker noise of the tail current is suppressed, the phase noise is reduced.The proposed design accomplishes a wide tuning frequency range by a combination of using a 5-bit switch capacitor array(SCA) for discrete tuning in addition to linearly varying AMOS varactors for continuous tuning. The proposed design has been fabricated and verified in a 0.18 m TSMC CMOS technology process. The measurement indicates that the quadrature voltage controlled oscillator has a 41.7% tuning range from 3.53 to 5.39 GHz. The measured phase noise is 127.98 d Bc/Hz at 1 MHz offset at a 1.8 V supply voltage with a power consumption of 12 m W at a carrier frequency of 4.85 GHz.