Importance

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Abstract

A frequency-adjustable direct current biasing circuit is disclosed for providing a DC bias voltage or a DC connection to ground for an RF or microwave circuit without substantially affecting the RF or microwave signal of the circuit. The biasing circuit includes a transmission line having a first portion for connection to the RF circuit and a second portion connected to a low-impedance-to-ground structure, such as a bypass capacitor or a DC path to ground. The electrical length between the first and second portions is about 90 degrees. The biasing circuit further includes an open ended tuning stub coupled to the transmission line that has a length that is adjustable. By adjusting the length of the tuning stub, the biasing or grounding circuit can provide better isolation for RF energies at different selected frequencies. Also disclosed herein is a dielectric resonator oscillator (DRO) that uses the frequency-adjustable biasing circuit. Further disclosed is a DRO that includes a FET gate return having an RF-shunted, relatively high resistance coupled to the gate of a field effect transistor by way of a quarterwave transmission line. This improved FET gate return provides for reduced phase noise of the DRO.

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First Claim