Abstract
The pulse-modulated polar transmitter (PMPT) uses radio-frequency (RF) phase modulated signal with pulse-width modulated envelope to drive a power amplifier (PA) as a switch to achieve high linearity and high efficiency. However, as the signal bandwidth increases, various non-idealities limit the performance of the PMPT architecture. In this paper, a Gibbs-phenomenon reduction filter is proposed with a partial Fourier series of digital pulse-width modulation (PWM) such that the pulsed signal is more immune to the distortion in nonlinear high-efficiency RF PAs. For validation, a prototype transmitter was tested with a 20-MHz bandwidth 256-QAM 5G new radio (NR) signal at 2.14 GHz. The proposed method achieved a drain efficiency of 28.3%, error vector magnitude (EVM) of 1.67%, and adjacent channel leakage ratio (ACLR) of -45.4 dBc at an output power of 18 dBm using the prototype transmitter. Linearity requirements for base stations were met without the use of any digital predistortion methods.
Highlights
The radio-frequency (RF) power amplifier (PA) has always been the most power-consuming component in a wireless communication system
Since the proposed Gibbs-phenomenon-reduced digital pulse-width modulation (GRDPWM) is more immune to PA nonlinearity, the pulse-modulated polar transmitter (PMPT) is able to achieve an adjacent channel leakage ratio (ACLR) of −45.4 dBc, which exceeds the base station linearity specifications for the 5G New Radio (NR) standard without using any digital predistortion (DPD) techniques
In this paper, the problems raised by using partial Fourier series (PFS) of digital pulse-width modulation (DPWM) in PMPTs because of Gibbs phenomenon are discussed
Summary
The radio-frequency (RF) power amplifier (PA) has always been the most power-consuming component in a wireless communication system. Comparison of conventional DPWM, unfiltered and filtered PFS of an envelope signal in the time domain with PWM sampling frequencies fp = 100 MHz. respectively. The Gibbs-phenomenon-reduced digital pulse-width modulation (GRDPWM), which reduces the time-domain ripples in PFS of DPWM by adding the proposed Gibbs phenomenon reduction filter in (25), has the form of EGRDPWM (t) =. Performance Comparison of Conventional IQ signal, DPWM, PFS and GRDPWM
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