A low complexity and high modularity design for continuously variable bandwidth digital filters

TL;DR

This paper introduces a low-complexity, highly modular digital filter design enabling continuous bandwidth variation, suitable for SDR applications, using a novel sampling rate converter based on Pascal structure.

Contribution

It proposes a new fractional delay filter and sampling rate converter with reduced hardware complexity and high modularity for continuously variable bandwidth digital filters.

Findings

Requires fewer multipliers than existing converters

Enables arbitrary bandwidth variation through a single filter structure

Demonstrated in SDR channelizer applications

Abstract

Digital filters with variable bandwidth can be used for a variety of applications. Arbitrary change in the bandwidth of a digital Finite Impulse Response (FIR) filter can be acquired using sampling rate converters. In this paper, a sampling rate converter is proposed which is generated from Pascal structure, a fractional delay filter having low hardware complexity and high modularity. The proposed sampling rate converter requires lesser number of multipliers for implementation when compared with the sampling rate converters in the literature. A low pass filter having a single bandwidth sandwiched between two sampling rate converters can contribute multiple bandwidths in such a way that each bandwidth is an arbitrary variation of the original bandwidth. A two stage Frequency response masking approach (FRM) is used for the hardware efficient design of the original low pass filter. A low complexity and high modular novel design for a continuously varying bandwidth of a digital FIR filter is proposed in this paper using the proposed sampling rate converter. The modularity of the Pascal structure can be used to control both pass band ripple as well as stop band attenuation of the continuously variable bandwidth FIR filter design. Different communication standards in a Software defined radio (SDR) channelizer is realized using the proposed design of continuously variable bandwidth filter.