Abstract

Corner-reflector mixers have been successfully used in heterodyne receivers at submillimeter wavelengths (100-500 μm) for a variety of applications including ground-based and airborne astronomy.¹ The mixers generally consist of a long-wire (4λ) whisker antenna attached to a Schottky diode, plus a 90° corner reflector with its vertex spaced 1.2λ from the whisker.² At shorter wavelengths near 100 μm, however, difficulties in fabricating an accurate 4λ mixer make it desirable to use longer antennas and larger vertex displacements, if such is possible without loss in efficiency. In general, the optimum position of the antenna is at the peak of the standing wave distribution of the electric field induced inside the reflector by a plane wave incident at the main lobe angle of the whisker antenna. We have found that this spacing is easily calculated for any antenna length I from the relation s = λ/2·sin(θ), where the main lobe angle is given by θ = arccos(1 − 0.371λ/I). Antenna patterns calculated from such configurations with whisker lengths between 4λ and 10λ give approximately symmetric main lobes with widths ranging from 14° to 8°. These predictions are confirmed by our measurements over a range of wavelengths. In addition, our design which inverts the traditional geometry of the whisker bend leads to a greatly simplified mixer structure with no discontinuities in the reflector surfaces.

© 1986 Optical Society of America