Tuning Characteristics of Multipath Ring Oscillators

Abstract

A multipath ring oscillator is composed of i chain of inverters, the outputs of which are weighted and combined to provide the feedback signal. Multipath oscillators may be operated in two basic modes, viz, the mux mode and quadrature controlled mode. In the mux mode the frequency of oscillation is controlled by varying the effective number of inverter stages while the quadrature mode utilizes injected quadrature currents to control the frequency.

The performance characteristics of multipath ring oscillators are presented. Experimental results on tuning characteristics of several two-path and three path VCOs are presented. Results are also given for a PLL using phase frequency detector and charge pump, and for a crystal controlled VCO using a ring.

Indexing terms:

• Ring oscillator
• Inverter
• VCO
• Mux