The Novel Bandpass Filter Designs Using the Microstrip Line Structure

• Main Authors: Pow-Wen Chen, 陳柏彣
• Other Authors: Min-Hua Ho
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/55574604069610218619

碩士 === 國立彰化師範大學 === 電信工程研究所 === 96 === Abstract In this thesis, multi-band microwave bandpass filters (BPFs) designed using cross-coupled stepped-impedance resonators (SIRs) were studied. Three microwave filters,including two dual-band and one single-band BPFs were designed, implemented, andinvestigated. The first dual-band BPF circuit consists of λ/2 and λ/4 stepped impedance resonators (SIRs) for the WLAN applications. The filter covers both the operating frequencies of 2.45 GHz and 5.2-5.8 GHz. The doubly parallel-coupling mechanism is used in the filter design to reduce the insertion losses and to gain a wider bandwidth (BW). The cross coupling configuration and the tapped-line I/O feed are adopted in this filter design to provide the attenuation poles for improving the signal selectivity and stopband rejection levels. Experiments were conducted to verify the circuit performance. The second BPF proposed in this thesis was a dual-band bandpass filter using λ/4 stepped impedance resonators (SIRs) embedded with spur-line for the WLAN applications. The filter covers both the operating frequencies of 2.45 GHz and 5.2-5.8 GHz . The crossly coupled mechanism is used in the filter design to provide attenuation poles by the passband edges for enhancing the signal selectivity and to increase stopband rejection levels. The tapped-line is incorporated in feed structure to save the circuit space. The spur-line is embedded in each I/O SIRs to push the upper stopband limit to a higher frequency. Experiments are conducted to verify the circuit performance. A good agreement is observed between the simulation and the measurement. Finally, we employ the stepped-width-slots spur-line (SWSS) in the parallel-coupled microstrip BPF to eliminate the higher harmonics due to coupled-lines’ even- and odd-mode effect. The ABCD matrix of the SWSS based on the even- and odd-mode of parallel-coupled line model is developed to analyze the structure frequency response. Single SWSS or two SWSSs are embedded in each of the coupled-lines to suppress signals of multiple frequencies for extending stopband region. Results obtained in this research can be applied to commercially practical RF and microwave systems. The techniques presented in this research are expected to serve as a useful reference for microwave filter designers in this and related research fields.