Comparison of Two Filtering Techniques in Differential LC VCO Using Asymmetric Tank Structure

This paper presents two InGaP/GaAs HBT differential cross coupled VCOs designed with low phase noise for adaptive feedback-interference cancellation systems (AF-ICS). The main idea is using low pass and band pass filtering technique for noise frequency. With this the designed VCO, Is´ one achieved a phase noise of -130.40 dBc/Hz at 1 MHz offsets from the carrier frequency of 1.619 GHz and 2nd one achieved - 127.93 dBc/Hz at 1 MHz offsets from the carrier frequency of 1.604 GHz. Each VCO dissipates output power of-6.68 dBm and -10 dBm by supplying 5 V. Two pairs of BC junction diode are used as varactor to get a broad band tuning range for both VCOs.