Absfracf-A unilateral 1.5-to 6-GHz varactorquadruple has been developed. The multiplier delivers 2+ watts at 50-percent conversion efficiency and has a maximum inputVSWR of 1.6 for all conditions of load impedance. The quadruple efficiencyis diode limited, not circuit liiited, with only 0.5 dB of the 3.O-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 chcuit complexity and circuitloss. Varactor multiplier stages are often cascaded using isolators to improve the stabiEty. The use of unilateralmultipliers eliminates the necessity for such isolators.