CMOS RF polar transmitter for UHF RFID reader applications

Abstract

An emerging issue of mobile RFID readers is that the area occupied by the circuitry of the mobile RFID reader should be small enough for integration with other communication systems such as GSM and W-CDMA in a handset application. By virtue of its ability to be scaled down, CMOS technology is considered as the best way to integrate the whole transceiver of an RFID reader in a single chip at low cost. In order to realize full integration, the power amplifier should be also integrated in a single chip with CMOS process. Some research has been made toward a fully-integrated CMOS PA for RFID reader applications. Since the RFID reader adopts binary-Amplitude Shift Keying (ASK), conventional transmitters of RFID readers with direct up-conversion architecture are based on the I/Q modulation scheme which utilizes a linear PA to convey data by means of the amplitude of the signal. However, the linear PA in CMOS technology suffers from poor power efficiency, especially when the envelope of transmitted signal varies frequently. Thus, in order to increase the power efficiency, a polar transmitter with a switch-mode PA is preferable. In this thesis a fully-integrated switch-mode CMOS PA fabricated in 0.25-㎛ CMOS process is presented, and polar transmitter architecture for a UHF mobile RFID reader using binary-ASK is proposed. The CMOS PA is designed with a cascode structure and shows a class-E operation with more than 24 dBm of output power at 910 MHz and with more than 35 % of power-added efficiency (PAE) from 860 MHz to 960 MHz under 2.5-V supply voltage. The polar transmitter with the CMOS PA modulates the amplitude signal by turning on and off the common gate transistors of the cascode structure. To comply with the transmit mask regulation of EPC global class-1 generation-2, an analog pulse-shaping filter is attached in front of the cascode gate node of the PA. In addition, a fully-integrated switch-mode CMOS PA fabricated in 0.18-㎛ process which can be also applied to...