Single Microstrip Open-Loop Resonator Bandpass Filter with Spurious Suppression

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

This research is engaged in synthesis of microwave bandpass filters with a compact size and good stopband characteristics. In general, half-wavelength open-circuited resonators have been often adopted in microwave bandpass filter design, since their structures are adequate for compact filter synthesis. One of the serious disadvantages is that the half-wavelength filters inherently have a spurious passband at the multiple of operation frequency, which degrades the stopband performance. This proposal adopts the single microstrip open-loop resonator in the microwave bandpass filter design. The resonator is simply a half-wavelength long open-circuited microstrip line whose two low-impedance sections are bent to form a triangle-like formation for saving space. The tightly-coupled ends has an end-coupled capacitance, which can create additional transmission zeros at upper stopband. Second, the frequencies of transmission zeros are tuned to collocate with the leading two higher order resonances by changing the line width of the slant sides of the resonator so that the circuit has a sharp transition and wide stopband. In addition to the formulation and simulation, we will also fabricate and measure practical circuits to demonstrate the significant improvement. Open-loop microstrip bandpass filters are highly used in wireless communication applications. In this research, we propose the design of the single open-loop resonator bandpass filter with a compact size and wider upper stopband. Since the novel resonator has a simple structure and a good performance, we believe, it will be adopted for commercial and academic applications.

Project IDs

Project ID:PB9607-2375
External Project ID:NSC96-2221-E182-002
StatusFinished
Effective start/end date01/08/0731/07/08

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