新型高次諧波抑制低通瀘波器之設計

A NOVEL SPUR-FREE LOW PASS FILTER DESIGN

本文提出一種新型高次諧波抑制低通濾波器設計可用於抑制諧波與寄生訊號。此低通濾波器具有極寬截止頻帶與高回拒寄生訊號的能力，能滿足現代無線通訊系統的要求。而且，此濾波器於截止頻率附近具有相當陡峭的衰減斜率，同時通帶處的介入損失亦是很小，電路尺寸比同級的步階阻抗式低通濾波器還要小。此濾波器的設計公式是由耦合線與傳輸線的等效電路取得。使用IE3D電磁模擬軟體計算其電氣特性。模擬結果與電路實際量測結果有相當良好的一致性。

In this paper, a novel spur-free low pass filter suppressing harmonics is proposed. This low pass filter has a broad stop band and a high rejection ratio which can meet the requirements for modern wireless communication systems. Furthermore, the filter shows a very sharp attenuation slope above the cutoff frequency and a low insertion loss in the pass band, and is quite small compared to stepped impedance low pass filters of the same order. The design formula of this novel low pass filter is based on the equivalent circuit of coupled lines and transmission lines. The filter is evaluated by an IE3D electromagnetic simulator. The simulated data are in good agreement with the experimental results.