Design of Digital Filters for 5G Communication Front Ends Utilising Bilinear Transform

Abstract

Vehicle-to-vehicle (V2X) communications is one of the many services supported by 5G, using lower frequency bands and high-frequency millimetre-wave spectrum, along with other radio technologies like ultra-wideband (UWB) and improved sensing and processing techniques. Filters are essential in the domains of telecommunication systems and digital and analogue signal processing. With the introduction of 32-bit word lengths and floating-point capabilities, digital filters have gained popularity recently, despite historical accuracy concerns related to finite word length. This paper delineates the design and analysis of digital filters for 5G communication front ends utilising the bilinear transform technique. As bandwidth and signal integrity demands escalate in 5G networks, meticulous filter design is crucial for optimal performance in sub-6 GHz systems. Chebyshev Type I, elliptic, and Bessel filters were used and evaluated based on how they respond to different frequencies, their delay characteristics, and how well they maintain signal quality when using modulation schemes like 16-QAM. The results show that Bessel filters keep the signal clear without any distortion, have a consistent group delay, and achieve an EVM of about 99.9991%, making them the best choice for baseband extraction. Elliptic filters exhibited the sharpest change in response, with more than 60 dB reduction in unwanted signals and an EVM of 99.9026%, making them suitable for applications requiring high selectivity. Chebyshev filters had the sharpest drop-off, with a passband ripple of 0.49 dB and an EVM of 99.9996%, which means they greatly reduce unwanted signals but at the cost of some loss in signal clarity. All filters validated BIBO stability using pole-zero analysis. The Chebyshev filter is optimal for situations that require significant attenuation in a small space, although this comes at the cost of some signal clarity. The results confirm that digital filters, when carefully matched to the application requirements, work reliably for real-time 5G systems.