Importance

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Abstract

A circuit and method are disclosed herein for a multi-phase voltage-controlled LC oscillator. The oscillator is configured as a ring containing N sections, each of which has an LC tank circuit that determiines the oscillation frequency. All the oscillator sections produce a signal at the same frequency, but with a constant phase angle offset between one section and the next. Thus, for example, a 4-phase version of the oscillator would have 4 sections, producing signals with phase angles of 0.degree., 90.degree., 180.degree., and 270.degree.. The phase offset in each section results from the use of amplified quadrature signals to drive the LC circuits. An advantage of this approach to obtaining multiple phases is enhanced frequency stability, since the LC circuits in the oscillator sections all operate at resonance. Frequency modulation is accomplished without the use of varactors or other voltage-controlled tuning devices. Instead, a quadrature current summed into the LC tank circuit of each section increases or decreases the resonant frequency. A transconductance amplifier regulates the quadrature current, so the oscillation frequency can be controlled using an external voltage.

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First Claim