A High-Precision and Wide-Range DPFM/DPWM Generation Method Using FPGA

Abstract

Current digital pulse width modulation (DPWM) implementations prioritize high-precision duty cycle control, but they suffer from relatively lower frequency adjustment precision, which is inadequate for applications requiring high frequency resolution, such as RF Class-D power amplifiers. To address this limitation, this paper introduces a cost-effective FPGA-based method for generating multichannel high-precision and wide-range digital pulse frequency modulation (DPFM) signals. This method allows for the simultaneous generation of multiple adjustable duty cycle and frequency pulses, with precise control over the phase shift between different pulse channels. This solution innovatively enables high-precision regulation of both period and duty cycle across a broad frequency spectrum. It utilizes a hybrid architecture that integrates multiple counters with delay units, thus expanding the adjustable range for both cycle and duty cycle while preserving high precision. In this paper, employing IDELAYE2 as the delay unit, the PFM signals generated have a minimum frequency of 12 Hz and a maximum of 15 MHz, with all adjustments—period, duty cycle, and phase shift—achieving an accuracy of 39 ps. The scheme's validity is confirmed using the Xilinx ZYNQ XC7Z100 series FPGA, demonstrating an average deviation of approximately 6 ps between the nominal and actual measured values, linearity $R^2$ = 0.9993.