A Dual-Phase Center-Aligned 7-Bit Digital Pulsewidth Modulator for Polar Transmitters

• Published in: IEEE transactions on microwave theory and techniques Vol. 70; no. 11; pp. 1 - 8
• Main Authors: Kuo, Chien-Hung, Yeh, Jian-Tzu, Chen, Jau-Horng, Chen, Yi-Jan Emery
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Clocks; Delays; Envelope elimination and restoration (EER); Frequency modulation; mobile communication; Modulation; Nonlinearity; power amplifier; Pulse duration modulation; Pulse width modulation; pulse-modulated polar transmitter (PMPT); pulsewidth modulation (PWM); Quadrature amplitude modulation; Radio signals; Radio transmitters; Transmitters; Voltage control; Waveforms
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2022.3205586

This article presents a dual-phase center-aligned 7-bit digital pulsewidth modulator for the envelope modulation of pulse-modulated polar transmitters (PMPTs). The digital pulsewidth modulator operates at a clock frequency and delivers the modulation frequency of 100 MHz. A delay-locked loop (DLL) consisting of 128 delay cells is used to generate the pulse edges for synthesis of center-aligned pulsewidth modulation (PWM) waveforms. The pulsewidth resolution is 78.1 ps. The measurement results show that the integral nonlinearity (INL) and differential nonlinearity (DNL) of the output pulses are within <inline-formula> <tex-math notation="LaTeX">\pm</tex-math> </inline-formula>0.4 and <inline-formula> <tex-math notation="LaTeX">\pm</tex-math> </inline-formula>0.3 LSB, respectively, in the duty cycle range of 2.12%-96.51%. Tested with a 20-MHz 256-quadrature-amplitude modulation (QAM) 5G new radio (NR) signal, the transmitter signal using the output of the modulator achieves the adjacent channel leakage ratio (ACLR) of <inline-formula> <tex-math notation="LaTeX">-</tex-math> </inline-formula>33.8 dBc.