Analysis of Two Filtering Techniques in Differential LC VCO Design using Asymmetric Tank Structure

Abstract

This paper presents two InGaP/GaAs HBT (heterojunction bipolar transistor) differential cross-coupled voltage controlled oscillators (VCO) designed with low phase noise for adaptive feedback–interference cancellation systems (AF-ICS). The main idea is to use low pass and band pass Altering technique for noise frequency. With this, the designed VCO, the first one achieved a phase noise of −130.40 dBc/Hz at 1 MHz offsets from the carrier frequency of 1.619 GHz and the second one achieved −127.93 dBc/Hz at 1 MHz offsets from the carrier frequency of 1.604 GHz. Each VCO dissipates an output power of −6.68 dBm and −10 dBm respectively by supplying 5 V. Two pairs of base-collector (BC) junction diode are used as varactor to get a broad band tuning range for both VCOs.