Planar Tunable 3rd Order Bandpass Filter for GPS Applications

A Chebyshev microstrip 3rd order tunable bandpass filter designed for GPS application is represented in this paper. The designed filter is operated at a downlink frequency of 1.5 GHz with a passband bandwidth of 0.2 GHz. The circuit of purpose is simulated using a substrate with a 3.38 dielectric constant, 0.813 mm substrate thickness, and 0.0027 loss tangent. This paper investigates two different methods of filter tunability which are the capacitively loaded coupled sections and tunability using a series capacitor. Moreover, the filter performance has been justified using the ideal capacitors and variable capacitors (Varactor) model. The proposed circuit has been designed and simulated using ADS software.