TH-3 microwave Radio system: Modulators

In a TH-3 repeater the required frequency downconversion, upconversion, and shift is performed by three similar solid state modulators. The choice of an unbalanced design resulted in a simple modulator microwave structure which can be easily tuned and uniformly reproduced. The shift and transmitter modulators use a varactor diode for high pump efficiency while, in the receiver modulator, a Schottky diode is used to achieve a low noise figure and broadband operation.