| 摘要 |
A synthesizer incorporating voltage tunable capacitors, comprising at least one resonator coupled into a base circuit of a bipolar transistor, the at least one resonator including at least one voltage tunable capacitor; the bipolar transistor including a collector which terminates in a radial micro strip stub and an emitter which produces an output via an impedance matching circuit, a buffer amplifier and an RF filter; a frequency divider, programmable phase locked loop and loop filter receiving the output of the RF filter and providing the input to a controller; an integral switch mode power supply providing power to the base circuit via a first power supply filter, and the controller via a second power supply filter. The controller scales the user-selected control voltage range to the levels required by the voltage tunable capacitors associated with the at least one resonator. The resonator of the synthesizers incorporating parascan(TM) varactors of the present invention can be at least one at micro strip resonator and the bipolar transistor can be a Si-bipolar transistor. The emitter of the bipolar transistor is further terminated into a short-circuited micro strip stub, thus preventing lower modes of oscillation to exist. The present invention can further comprise a buffer amplifier or circulator associated with the impedance matching circuit to reduce the pulling effect where needed. Also, the present invention can further comprise a buffer amplifier in the output circuit to amplify the output power where needed. In a preferred embodiment of the present invention the controller can be a simple one-transistor controller and the controller can have a user-specified frequency response, thus aiding integration with phase-locked loop synthesizers.
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