Characteristics of a multibeam antenna using quasi-optical hybrid ring antenna-mixer array

This paper addresses a principle of multibeam quasi-optical antenna mixer array. At first, the multibeam antenna using this technique is presented. The multibeam antenna, composed of quasi-optical hybrid ring antenna-mixer, is measured at K-band. The antenna element consists of back-to-back aperture coupled patch antenna to couple the RF signal at 18.4 GHz to the sigma port of a hybrid ring mixer while the LO signal at 17.5 GHz is coupled to the delta port. The HSCH-9101 GaAs beam lead Schottky diodes are used to transform the RF signal to intermediate signal at 1.45 GHz. This antenna can solve the retransmitted LO signal problem by using hybrid ring structure. The results show the isolation between the LO to RF is better than -20 dB at 18.298 GHz, and the isotropic conversion loss of lower sideband is better than 15 dB at 18.95 GHz. Injection locking characteristics of the tilted two-patch antenna is considered. It is used to investigate locking characteristics of nonlinear oscillators, and it is used to be a guideline for selecting the local oscillator frequency in the multibeam quasi-optical antenna-mixer array. The 4/spl times/1 quasi-optical hybrid ring antenna-mixers are fabricated and measured. The multibeam operation can be specified by fixing the angle of the LO transmitting antenna at each LO frequency that will be operated at the same time. The result shows three IF signals and three radiation patterns.