A dual-band RF front-end for WCDMA and GPS applications

In this work, a dual-band radio frequency (RF) front-end, which can be operated for wideband code division multiple access (WCDMA) and Global Positioning System (GPS), is developed. This RF front-end includes two differential low noise amplifiers, double-balanced mixers of I and Q channels and a multiphase voltage-controlled oscillator (VCO). The front-end architecture without external components is implemented by the low intermediate frequency (IF) technique which is very suitably for circuit integration. As compared to the other RF front-ends receiving multi-frequency bands, the proposed front-end utilizes two low noise amplifiers, shared mixers and multiphase VCO to reduce the hardware complexity. In addition, this architecture is easily scaled to receive more than two frequency bands. Here, a multiphase VCO consisting of a phase-setting unit and range-programmable VCO is utilized to generate two frequency bands having four phases. The frequency band is determined by the number of paralleled inverter rings in the proposed range-programmable VCO. Compared to conventional oscillators, the proposed multiphase VCO can improve phase noise and phase accuracy due to the closed-loop trigger between the phase-setting unit and the range-programmable VCO. By using the TSMC IP6M 0.18 μm CMOS technology, the proposed dual-band RF front-end was designed at a supply voltage of 1.8 V to have a gain of 30 dB for IF at 2 MHz, IIP3 of -30 dBm and a noise figure of 5 dB.