Image recovery mixer

Abstract

A microwave mixer is formed of three orthogonally oriented waveguides, each having a rectangular cross-section defined by a pair of opposed broad walls and a pair of opposed sidewalls wherein the ratio of cross-sectional dimensions typically is 2 :1. The mixer includes an input coupling probe, a mixing region, and an output filter disposed serially along a first of the waveguides. A second of the waveguides applies a reference LO signal via the probe to the mixing region, the mixing region including at least one diode with two diodes being employed in the preferred embodiment of the invention. A section of dielectric board serves to support the diodes of the mixing region, components of the filter, and the probe in the first waveguide. The third waveguide applies an RF input signal to the mixing region via an input port in a side of the first waveguide, and via an impedance matching taper and a waveguide section of reduced height which impedes egress of both an IF and an image signal produced in the mixing region by interaction of the LO and the RF signals. The filter is located at the mixer IF output port for reflecting an image-frequency signal back to the diodes of the mixing region for further interaction with the LO signal to generate additional IF signal in phase with the originally produced IF signal for additional power and a significantly higher signal-to-noise ratio.