The present invention provides a millimeter-wave passive FET switch by using impedance transformation network to transfer the effective capacitance seen from the drain to source of an FET at off-state to low impedance, while transfer low impedance seen at on-state to high impedance. Since both on-state and off-state are transferred to high impedance, and low impedance respectively, a high-performance switch can be achieved. Since the size of the transformation network is small, the performance of the switch can be promoted with low cost.

This invention provides a multistage frequency multiplier having a plurality of frequency doublers. Each doubler incorporates a three-terminal transistor device and is connected to an adjacent doubler via an interstage network. The network comprises a transmission line having its electrical parameters selected to achieve conjugate impedance matching at the intermediate harmonic frequency generated by the corresponding doubler. This network also includes a quarter-wavelength open-ended stub for suppressing a main input frequency component received by the corresponding frequency doubler. A shunt resistor on the transistor gate is preferably used to stabilize the network. This interstage network simplifies overall circuit topology to reduce total circuit size, and provides increased drive power levels to permit broader bandwidth and stabilize required output level from a local oscillator. This invention is particularly useful in high-speed, large-capacity communications systems and in microwave and millimeter-wave radar applications.