兩種具寬截止帶之微帶線帶通濾波器

Abstract

本論文提出兩種方法壓抑平行耦合微帶線帶通濾波器之多重諧波。第一種是鋸齒耦合微帶線結構，藉由改變週期數目和調整幾何參數，分析此週期性結構所產生的截止帶之特性。利用不同週期數之耦合級所產生的不同截止帶，可串接成具有很寬的截止帶之帶通濾波器。本文並且實作一個三階電路，其量測結果顯示-30 dB之上截止帶可達中心頻率的十一點八倍。 第二種是將共振器施以加載開路殘段，先使每個共振器具有相同的通帶頻率，但具有不同的高階諧振頻率，藉多重高階諧波彼此抑制，以達到延伸上截止帶的效果。所製作的電路，量測數據與模擬結果相當一致。

This thesis presents two innovative parallel-coupled line filter structures for multi-spurious suppression. Parallel-coupled line filters with periodic corrugation are designed to realize a wide upper stopband with a satisfactory attenuation level. The stopband characteristics of the corrugated section are investigated by changing its geometric parameters and the number of periods. As a result, corrugated sections with various rejection bands are cascaded to construct a bandpass filter with a wide upper stopband. Measured responses of a tested third-order circuit show that the upper rejection band can be extended up to 11.8 times the passband frequency. In the second design, parallel-coupled line bandpass filters are synthesized based on stub-loaded resonators. The open stub behaves as a capacitor which can be trimmed to produce resonators with the same fundamental frequency, but different higher order resonant frequencies. The resonators with staggered higher order frequencies are designed to build a filter to achieve multi-spurious suppression in the upper stupband. Measured results show good agreement with simulated responses.