To support the tremendous demands on mobile-data traffic, researchers are motivated to overcome the global bandwidth shortage by exploring the underutilised millimetre-wave frequency spectrum. A millimetre-wave communication system has a large bandwidth, which can be exploited to provide a fast data-transfer rate up to multi-gigabits per second. However, as millimetre-wave filters operate in a higher frequency band, they are highly sensitive to component value variations, resulting in complex and expensive manufacturing processes. The Chained-Function Waveguide Filter offers a robust and compact filter with reduced sensitivity to manufacturing errors, providing a low-cost and reliable solution to achieving sustainable filter synthesis for 5G and beyond.