Design and Implementation of a Nearly Nyquist Polyphase Filter Structure Sampling Rate Converter for 5G Systems

With the continuous development and progress of the 5G NR (New Radio) standard, it is imperative to explore the design of a digital sampling rate converter that is apt for a 5G NR communication system. In this paper, a digital sampling rate converter based on the idea of Nearly Nyquist is designed by adopting a polyphase filter structure suitable for communication systems and combining the zero inter-symbol interference (ISI) requirement and other characteristics (e.g., passband ripple and stopband attenuation) in the communication systems. Following MATLAB simulation tests of the 5G NR over-the-air testing, the resultant ISI was found to be insignificant when compared with the ideal Nyquist system, with the added advantage of enhanced stopband attenuation capability and the fixed-point characteristic of the filter coefficients. Moreover, the proposed sampling rate converter has been successfully implemented on a suitable Field-Programmable Gate Array (FPGA), with results affirming conformity with expectations, and its maximum operational clock frequency of 614 MHz, adequately catering to the needs of the 5G NR communication system.