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

Area of Science:

• Electrical Engineering
• Digital Communications
• Signal Processing

Background:

• Existing Pulse Width Modulation (PWM) techniques often suffer from spectral distortion and aliasing.
• Advanced wireless standards like 5G and LTE demand high spectral purity and efficient signal transmission.

Purpose of the Study:

• To present an All-Digital Aliasing-Free PWM (AF-PWM) transmitter architecture.
• To demonstrate its effectiveness for 5G-NR and LTE signals, particularly when paired with a Class-D power amplifier.

Main Methods:

• The AF-PWM transmitter combines multiphase band-limited PWM (MP-BLPWM) for finite harmonic generation and accumulated N phase-shift pulse modulation (AN-PSPM) for all-digital conversion.
• Field-Programmable Gate Array (FPGA) implementation was utilized for the transmitter.
• Experimental validation was performed using 5G-NR and LTE signals, with and without a switched-mode power amplifier (Class-D PA).

Main Results:

• The MP-BLPWM approach eliminates image and aliasing distortion, enhancing spectral performance.
• When integrated with a Class-D PA, the transmitter achieved Adjacent Channel Leakage Ratio (ACLR) of 37.9 dBc for 5G-NR and 42.2 dBc for LTE.
• Error Vector Magnitude (EVM) measurements were 1.3% for 5G-NR and 0.9% for LTE when used with the Class-D PA.

Conclusions:

• The proposed AF-PWM transmitter offers superior spectral performance and signal integrity.
• Its all-digital nature and effective distortion reduction make it suitable for advanced wireless communication systems.