Active bandpass filter application with using Schottky diode for 2.4GHz ISM band for low power transceiver systems

This article discusses the development of an electronically tuned filter capable of a wide tunable frequency range and simultaneous 3-dB bandwidth variations at any frequency within its tuning range. Schottky-tunable filters are designed using high-dielectric, soft-substrate material for printed resonators as well as also high-Q ceramic resonators, and their test data are compared. The designed filter had a simple structure and the characteristics of wide tuning range of 2.40GHz to 2.70 GHz and low insertion loss of less than -12.20 dB. The concept of tuning a filter´s 3-dB bandwidth with voltage is demonstrated and the effect of the bandwidth tuning elements on the tunable filter performance is discussed.