Design considerations for anti-phase injected quadrature voltage controlled oscillators

The performance of the series cascode-injected quadrature voltage-controlled oscillator (CI-QVCO) topology is compared against its degeneration-injected counterpart (DI-QVCO) based on analyses of start-up loop gain, oscillation frequency, phase noise, tuning range, and quadrature phase error. Detailed analyses and extensive simulations show that in addition to offering comparable quadrature phase error performance, the DI-QVCO configuration exhibits superior phase noise performance, more robust start-up characteristics, and greater suitability for high frequency applications that require a relatively large tuning range.