A STUDY ON MULTI-BAND LINEAR CMOS POWER AMPLIFIERS FOR WIRELESS MOBILE COMMUNICATION APPLICATIONS

Abstract

In this Dissertation, a study on multi–band linear CMOS power amplifiers (PAs) for wireless mobile communication applications is performed. Since mobile and radar applications are allocated at different center frequencies with various bandwidths, a single PA is required to support number of frequency bands for size and cost reduction. Even though the CMOS technology take advantage of cost–benefit and possibility of integration with other circuits, designing linear multi–band CMOS PAs generating high output power has been challenging due to low breakdown voltage and nonlinear nature of the CMOS device. Next, three design techniques to realize broadband/multi–band linear PAs are presented. First, a broadband linear stacked–FET CMOS PA for LTE handset applications is demonstrated. The PA is based on continuous Class–F mode of operation, where a proposed output matching network controls fundamental loads and their harmonics using a low pass network and a shunt resonator. An adaptive bias circuit with a low pass filter, as a linearization, generates an average bias depending on each output power. The proposed stacked PA, including the integrated bias circuit, is fabricated in a 0.11–μm RF CMOS technology. The measurement results show that the peak average power is improved by 1.5 dB under an ACLR_E–UTRA of -30 dBc, for a 16–QAM 7.5 dB PAPR LTE signal. From 1.55 GHz to 2.05 GHz, the designed PA delivers a linear output power of 24.3–25.2 dBm with a drain efficiency of 25.6–28.6 % at the ACLR_E–UTRA of -30 dBc, under the same bias condition. These results show the proposed CMOS PA is useful for broadband highly linear applications. Second, a reconfigurable S/X–band PA integrated into a 0.18–μm RF CMOS process is developed. A switchable transformer for output matching is operate by tuning its primary winding and a shunt capacitor under a 50 Ω load, with passive efficiency of more than 63 %/67 % for the S/X–band. Series resonance circuits with bond wires are employed at common–mode nodes, greatly improving the X–band performance of the PA. Despite the use of inter–stage matching without any tunable elements, the PA presents a power gain of more than 19.5 dB at both 3.0 and 8.0 GHz. The PA provides a saturated output power of 24.8/21.5 (21.5) dBm with a power–added efficiency (PAE) of 32.8 %/11.1 % (10.7 %) at 3.0/8.0 (9.0) GHz. The 1–dB bandwidth is 0.6/2.0 GHz (2.8–3.4 GHz/7.5–9.5 GHz) for the S/X–band. This amplifier demonstrates suitable performance for dual band high–resolution radar transceivers. Last, a reconfigurable broadband linear PA for long–range WLAN 802.11 af/ah handheld applications is presented, which is fabricated in a 0.18–μm RF CMOS process. The reconfigurable operation (Mode 1: 450–650 MHz/Mode 2: 650–1100 MHz) at a proposed in/output matching network provides the PA with broadband behavior. The output network is realized by a switchable transformer which shows peak maximum passive efficiencies of 65.03 %/73.45 % at 0.45/0.725 GHz. To compensate AM–to–PM distortion, an adaptive power cell at the common gate transistor is utilized and phase variation is enhanced by 0.7º. With simulated continuous wave sources, an 1–dB bandwidth according to a saturated output power is 0.45–1.1 GHz (FBW: ~84 %), presenting the output power/PAE of above 26.73 dBm/20 %. For two tone simulations with 40 MHz tone spacing, an average output power shows more than 23.7 dBm, under an IMD3 of -30 dBc. Therefore, the suggested design can deliver a linear amplification for a broadband/wideband signal of wireless linear communication applications.