A New HF VCO With Quadrature Outputs

A new architecture of mutually coupled regenerative oscillators is presented. It has been used to design a low-noise high-frequency VCO capable of producing two output signals in quadrature with essentially identical properties. The phase relation between the quadrature outputs is frequency independent and extremely stable. A new way of coupling the regenerative oscillators is suggested in order to improve the frequency stability of the coupled oscillator system. Results obtained from a test chip have verified the viability of the new oscillator concept. The oscillator circuit has been realized in a medium-frequency (fT = 3GHz) bipolar process. The tuning range extends to 500MHz. At an oscilation frequency of 200MHz, measured phase noise was¿121dBc/Hz at 1MHz distance from the carrier.