A linear electronically tunable quadrature oscillator

Realization of a linear voltage controlled quadrature oscillator (LVCQO) using commercially available CFA (AD-844) and four-quadrant multiplier (AD-835) building blocks is proposed. The design is based on an electronically tunable allpass filter (ETAF) coupled with a voltage controlled integrator (VCI). Effects of device nonidealities, viz., parasitic capacitors and rolloff poles of port mismatch errors are insignificant, albeit the usable higher frequency ranges may be constrained. Experimental results with PSPICE simulation and hardware tests are included. Linear tuning of oscillation frequency (f_o) in a range of 1 ≤ f_o(MHz) ≤ 12 at low THD and satisfactory phase-noise margin had been reported.