Dual-band and harmonic suppression of filter designs based on asymmetric half-wavelength resonator

In this paper, a dual-band bandpass filter based on half-wavelength resonator is realized by adding shunt stubs. The added stubs are separately located on either side of the resonators to generate a second passband. To demonstrate the idea, transmission zeros and ABCD matrix of the filter are investigated. The filter is centered on 2.4 and 3.95 GHz with bandwidths 260 and 150 MHz, respectively. Furthermore, a novel bandpass filter based on half-wavelength resonator is designed to suppress harmonics. Rectangular grooves and perturbation stub are used to suppress the harmonics and improve the performance of the filter. Advantages of small size and low insertion loss can be obtained. At last, agreement between simulated and measured results validates the design theory.