Research On Novel Balanced Band-Pass Filter With Dual-Band Responses

With the development of wireless communication technology, a variety of new wireless communication systems emerge, which has greatly promoted the development of microwave devices, especially filter technology. Balanced circuits are widely used in modern communication systems due to their good common-mode rejection capability, which results in good immunity to the environmental noise as compared with their single-ended counterparts. Dual-band balanced band-pass filters play an important role and are valuable to research. This paper focuses on the research and design of novel planar micro-strip structure balanced band-pass filter with dual-band responses, and gives detailed summary and systematic analysis of the progress of theories and practices in the field of micro-strip line resonator and the design of high performance multi-band band-pass filters and balanced band-pass filters. A novel balanced band-pass filter with dual-band responses is proposed, using the structures of plane open-loop resonator, SIR, CLR, DSPSL, and TGV. The predicted and measured performances are in good agreement with each other, showing good common-mode suppression, managed dual-band responses, excellent out-of-band rejection and high selectivity. The fabricated filter has a size of0.25λg×0.08λg, where λg is the guided wavelength of the micro-strip line at the center of the lower pass-band, meeting the design requirements of miniaturization.