A Unilateral 6-GHz 2 1/2-Watt Varactor Quadrupler

A unilateral 1.5- to 6-GHz varactor quadrupler has been developed. The multiplier delivers 2 1/2 watts at 50-percent conversion efficiency and has a maximum input VSWR of 1.6 for all conditions of load impedance. The quadrupler efficiency is diode limited, not circuit limited, with only 0.5 dB of the 3.0-dB conversion loss due to circuit losses. The design uses a unilateral circuit concept for even-order harmonic generators to achieve the low sensitivity to output mismatch and a balanced diode pair hybrid circuit configuration to reduce circuit complexity and circuit loss. Varactor multiplier stages are often cascaded using isolators to improve the stability. The use of unilateral multipliers eliminates the necessity for such isolators.