s control commands to various functional assemblies in the mobile phone [1]. Figure 10.5 shows a high level handset architecture showing these three components. 10.4.1 The 3G mobile devices are becoming increasingly complex and feature hungry. This trend, coupled with the demand for low cost, thin profile, handset designs, is driving the need for smaller RF subsystems and tighter integration. The critical elements of RF are transceivers and power amplifiers as shown in Figure 10.6. ANTENNA FILTER MIXER FILTER AMPLIFIER Duplexer Frequency Baseband filter Synthesizer Processor FILTER MIXER AMPLIFIER Figure 10.6 RF Transceiver and PA. Reproduced from C 2008 Fujitsu [7] Smart Wireless Devices 10.4.1.1 Transceivers A typical RF transceiver includes filters, low-noise amplifiers, oscillator, mixer, and SO on. Mobile phones have followed a progression from high intermediate frequency (IF) designs to Zero-IF designs, also known as direct downconversion. Zero-IF receivers feature better spurious response than low IF designs. This advantage is due to the fact that low-IF receivers have to contend with image tones, and direct downconverters, in general, display higher tolerance to spurs generated by PLLs (Phase Locked Loop). Though, Zero-IF is advantageous it is susceptible to DC offsets at the mixer output. The DC offset issue gets further complicated due to 1/f "flicker" noise which is introduced into the receiver when directconversion architectures are implemented in CMOS (Complementary metal-oxide-semiconductor) [8]. CMOS is a technology for constructing integrated circuits (ICs). An antenna can be an integral part of the transceiver or may be mounted externally (on the top of the car). The antenna's main function is to convert the electrical energy into electromagnetic energy. The performance of the antenna system can enhance or seriously reduce the performance of mobile phones. 10.4.1.2 Power Amplifiers PA remains a very critical and standalone element of the handset. PA, as one of the most important components of a m