Band tunable microstrip bandpass filter using defected single patch resonator

Triangular patch resonator bandpass filters with tunable operation are developed to perform nicer filter properties of low passband insertion loss, transmission zeros and wide stopband. With tunable fractal-shaped defection acts as perturbation, filter operation frequency and operation band can be controlled, and the responses of undesired resonant modes are greatly weakened even suppressed. The new design brings filter more function which does not require changing the dielectric substrate or patch size. The designed filters have outstanding advantages of single patch with compact size and without resonator coupling gaps, simple circuit topology, nicer performances, miniaturization and can be easily tuned for more applications. All these features are well popular for wireless communication systems.