DESIGN AND ANALYSIS OF A HYBRID FEED ANTENNA FOR A FLUX-FLOW OSCILLATOR INTEGRATED 460 GHz SIS RECEIVER

We have designed a 460 GHz FFO-driven integrated SIS receiver in which the signal is fed via a quasi-optical hybrid antenna feeding system. Since in such quasi-optical SIS receivers the contribution of the quasi-optics to the overall receiver noise is considerable, it is important to be able to analyze the antenna efficiency in order to optimize its coupling and improve the noise temperature of the receiver. The goal of this paper is an attempt to analyze the gaussian coupling efficiency, far-field pattern and loss of the system, applying the geometrical optics-physical optics combined method to our hybrid integrated feed antenna. The computation of the loss contributed by different quasi-optical solutions can be a decision factor for selecting one particular design (optics materials, geometries, and configuration). Quite commonly adopted solutions employ a substrate hemispherical lens in conjunction with (or without) an objective lens of HDPE or Teflon located in the Fresnel region of the hemispherical lens. Such solutions have advantages and drawbacks, and other solutions, better for the receiver noise, may exist. In addition, computing the radiation characteristics of the quasi-optical system will be useful to interpret the integrated receiver measured performances and evaluate the diverse noise sources in this complicated system. A numerical tool based on the the ray-tracing and diffraction mixed approach was implemented to examine the radiation characteristics of the feed structure of FFO integrated SIS receiver.