使用LTCC技術設計一新型高Q值螺旋帶通濾波器

Abstract

本篇論文提出一個新型LTCC高Q值螺旋帶通濾波器電路架構。首先使用模擬軟體計算出諧振器的無載Q值，針對LC並聯諧振器與螺旋諧振器無載Q值作比較，計算出結果無載Q值分別為50與431，後續針對螺旋諧振器的無載Q值進行優化其長寬比例，得到最佳的無載Q值為579，並得到螺旋諧振器在寬與長比例為0.5時有最大的無載Q值，後使用優化過的螺旋諧振器完成本篇的LTCC高Q值螺旋帶通濾波器，由於電與磁的耦合效應產生了額外的三個傳輸零點，此三個傳輸零點的頻率可以由耦合的量大小作調整。濾波器整體的尺寸為2.5 mm x 2.0 mm x 1.4 mm，通帶2.50~2.7 GHz的插入損耗最大為2.5 dB，在2.4 GHz的衰減即可達16 dB，在高頻2.98 GHz也可衰減到20 dB，工作再LTE頻帶並且有效地改善與WI-FI之間的干擾，由此可以看出其很高的頻率選擇性，本篇針對LTCC螺旋帶通濾波器的模擬與實驗結果比對十分相符。

A novel low-temperature co- fired ceramic (LTCC) bandpass filter is proposed based on the helical resonator circuit. Firstly, calculating and comparing the unloaded Q factor between LC resonator and helical resonator utilize EM simulation tools, they are 50 and 431. Then optimize the unloaded Q factor of helical resonator with changing the width/length ratio, it can be found that when width/length ratio is close to 0.5 has the optimal unloaded Q factor is 579, then using the optimized helical resonator to design the LTCC high Q bandpass filter. A compact bandpass filter with high selectivity was designed at the center frequency of 2.6 GHz and fabricated using the proposed LTCC helical resonator. This filter has compact size of 2.5 mm x 2.0 mm x 1.4 mm and exhibits a low insertion loss of less than 2.5 dB in the passband. Moreover, three transmission zeros that are located at 2.34 GHz, 2.33 GHz ,and 3.0 GHz. At 2.4 GHz, the attenuation of more than 16 dB. Effectively improved the problem of LTE and WI-FI interference.