An S-band two-phase demodulator

The circuit described here is designed to pro vide image rejection by phase cancellation in a 2- to 4-kmc receiving system. Infinite image rejection is possible when the demodulator circuit delivers to the IF preamplifiers two equal amplitude IF output signals which differ in phase, by 90 degrees. The demonstration model is of split-block coaxial construction and provides an average of 14 db of discrimination against a cw image signal over the required range. Much higher discrimination is available for image pulses. Dual rf demodulation, IF outphasing, and gating of the IF amplifier are combined to accomplish image rejection.