All-digital aliasing-free PWM transmitter with reduced filtering requirements

TL;DR

This paper introduces a new all-digital PWM transmitter that reduces aliasing and filtering needs, suitable for advanced wireless communication.

Contribution

The paper proposes an all-digital AF-PWM transmitter combining MP-BLPWM and AN-PSPM for aliasing-free signal transmission.

Findings

The transmitter achieves 37.9 dBc ACLR for 5G-NR and 42.2 dBc for LTE when used with a Class-D PA.

EVM measurements are 1.3% for 5G-NR and 0.9% for LTE, showing high signal quality.

The design eliminates aliasing and reduces filtering requirements through finite harmonics PWM.

Abstract

The paper presents an All-Digital Aliasing-Free PWM (AF-PWM) transmitter, which combines multiphase band-limited PWM (MP-BLPWM) and accumulated N phase-shift pulse modulation (AN-PSPM), and its FPGA-implementation. As the architecture is based on MP-BLPWM, which generates finite harmonics PWM, this eliminates image and aliasing distortion, and improves spectral performance. However, finite harmonics PWM leads to large amplitude variation, which is converted to two voltage level signals using AN-PSPM, leading toward all-digital implementation. The transmitter’s performance is experimentally validated for 5G-NR and LTE signals, both with and without a switched-mode power amplifier (Class-D PA). Measurement results demonstrate that, when used with the PA, the transmitter achieves ACLR values of 37.9 dBc for 5G-NR and 42.2 dBc for LTE signals. Furthermore, the EVM of the proposed transmitter with the Class-D PA is measured at 1.3% for 5G-NR and 0.9% for LTE, highlighting its effectiveness for advanced wireless communication applications.

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