Tunable, distributed, voltage-controlled oscillator

Abstract

Techniques and structures for tuning integrated, distributed voltage-controlled oscillators (DVCO's) across a wide microwave frequency range are disclosed. One type of DVCO implements a tuning circuit that includes a pair of interconnected amplifying transistors and a current source connected to the transistors, such that a differential voltage input to the circuit adjusts the current to each transistor and effectively adjusts the “electrical length” of one of the transmission lines on which the output frequency is oscillating. This, in turn, adjusts the time delay and thus frequency of the signal propagating on the lines across a wide frequency band. This technique is called “current-steering.” In a preferred embodiment, the tuning circuit is balanced with a complementary tuning circuit to effectively adjust the electrical length of the second transmission line in the oscillator. In another technique that provides for more coarse, but wider range, broadband frequency tuning, the time delay, and thus, frequency, of the DVCO is adjustable by varying the capacitive loading on the transmission lines, by introducing a coupling capacitor between the transmission lines and tuning the intrinsic capacitances of the gain transistors with a dc bias input.