Optimization of Bandwidth and Insertion Loss using Currents of CMOS Quadrature LC Oscillators

Abstract

This paper presents analytical approaches for estimation of the Bandwidth and Insertion loss related to LC-Tanks quadrature oscillators. In parallel coupled quadrature oscillators, transconductances due to the currents of switching and coupling transistors in LC tank effects on the quality factor (Q). Equations are obtained from Q which is considered as a loaded Q (QL). The transconductances due to the currents of switching and coupling transistors effect on the QL and consequently, the bandwidth. In this way, the bandwidth is adjustable by the currents of CMOS transistors of quadrature oscillators. The insertion loss becomes important when a resonant circuit is as a matching network or band-pass filter. A new estimation for insertion loss of LC tanks as matching networks of quadrature oscillators is obtained rely on loaded Q (QL) and also QU which refers only to the each passive component itself, apart from rest of the circuit. The proposed analysis, have critical roles for quadrature oscillator’s applications which the bandwidth is imperative and also avoiding the excessive casualties is considered. To evaluate, a 5 GHz Parallel Coupled Quadrature Oscillator implemented using RLC tank as resonator and practical TSMC 0.18 m technology. The results confirm the proposed analysis