Comparison of Tunable Microwave Bandpass Filters

The development of software-defined radio and Radio-over-Fiber solutions for the future 5G systems necessitates the availability of small, cost-effective and tunable microwave filters. Possibility of integration is another requirement. As variable capacitance diodes are lossy in the millimeter wave (mmW) region, other solutions are utilized, e.g. tuning via changing the dielectric constant of ferroelectric ceramics by applying a biasing electric field. In this paper we compare the computer-simulated operation of a diode-controlled bandpass filter and a filter containing a ferroelectric material – the filters operate in the 3–4GHz microwave region and both are compatible with hybrid integrated circuit technology.