Analogue filters will always be needed for interfacing between digital systems and the 'real' analogue world. In fact, the high frequency integrated analogue filter has become a key component in achieving ubiquitous communication and computing. In recent years, the renewed interest in analogue, mixed-signal and RF circuits due to the need for system-on-chip design and the market for wireless communications has led to a new peak of research into high frequency integrated analogue filters.