Abstract: A frequency synthesizer has in series a digital synthesizer, mix and divide circuits, and a mix only circuit. Each mix and divide circuit includes a mixer having an IF input, a LO input and a RF output, a filter, and a frequency divider. A segment of a digital word selects a tone from a tone generator and also selects a passband of the filter. The selected tone is coupled to the LO input of the mixer. The frequency divider divides the filtered RF output of the mixer. The mix only circuit is at the output of the last of the series connected mix and divide circuits. The mix only circuit is similar to a mix and divide circuit, but does not have a frequency divider. The digital synthesizer provides a signal to the input of the first of the series connected mix and divide circuits, the frequency of which corresponds to a segment of a digital word. The filter is preferably a voltage tunable bandpass filter.

Abstract: A voltage tumble filter has several parallel coupled half wavelength lines. Each open end of a line is coupled to ground through a corresponding varactor. Voltage may be distributed to the varactors through a thin wire attached a quarter wavelength from each varactor.

Abstract: Local oscillator power is supplied to an array of single-ended microwave mixers by an offset horn. Each mixer has an integral antenna element.