Combined Linear and \Delta-Modulated Switch-Mode PA Supply Modulator for Polar Transmitters

• Published in: IEEE journal of solid-state circuits Vol. 44; no. 2; pp. 404 - 413
• Main Authors: Kitchen, J.N., Chu, C., Kiaei, S., Bakkaloglu, B.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.02.2009; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Buck converters; Circuit properties; CMOS process; Delta (\Delta) modulator; Delta modulation; Design. Technologies. Operation analysis. Testing; Electric potential; Electric, optical and optoelectronic circuits; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; Envelopes; Exact sciences and technology; Integrated circuits; linear regulator; Modulation; Modulators; Noise levels; polar modulation; power amplifiers; Power supplies; Radio frequencies; Radio frequency; Regulators; Rejection; RF signals; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Signal convertors; switching amplifiers; Switching, multiplexing, switched capacity circuits; Telephone sets; Transmitters; Voltage; Performance evaluation; Mobile phone; State of the art; Output power; Input signal; Transmitter; Power supply; polar modulation; Linear control; Complementary MOS technology; Delta modulation; power amplifiers; Selector switch; Closed loop; Modulator; Direct current convertor; Spurious free dynamic range; Power electronics; Noise shaping; Phase shift keying; switching amplifiers; Delta (A) modulator; Power amplifier; Low-power electronics; Linear regulator
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2008.2011010

A combined linear and delta-modulated (DeltaM) switch-mode PA supply modulator for polar transmitters in wireless handsets is designed in a 0.25 mum CMOS process. The modulator employs a DeltaM switch-mode DC-DC buck converter to enhance the efficiency of a linear regulator at backed-off supply voltages and powers. The delta-modulator's noise-shaping characteristic, linear regulator's power supply rejection, digital pre-emphasis of the input envelope, and a closed-loop amplitude path from the PA output are simultaneously used to achieve state-of-the-art modulator performance. The presented supply modulator follows the input signal's envelope with 20 dB output dynamic range, maximum efficiency of 75.5% at an output power of 30.8 dBm, and 75 dB SFDR for envelope signals up to 4 MHz occupied RF bandwidth. For a 1625 kb/s 8 PSK RF input signal at 900 MHz, polar modulation of a commercial low-power GSM-900 PA provides 10 dB ACPR improvement.