本論文研究一種使用基板合成波導(Substrate Integrated Waveguide)的三階雙工器(Diplexer)，雙模態共振腔的正交〖TE〗_102以及〖TE〗_201模態可以實現雙通道的傳輸，使不同中心頻率和比例頻寬的帶通濾波器能合併成一個，雙模共振腔以及腔體之間的耦合可以獨立控制，使得在中心頻率的選擇和比例頻寬的調整提供設計上的靈活度。
第一個電路在使用兩個雙模腔體和兩個單模的腔體所組成，中心頻率為12GHz和14GHz，3dB比例頻寬分別是5%和4.4%，基於雙模腔體互相正交的特性，調整輸入/輸出端口的饋入線長度寬度和調整雙模腔體和單模腔體之間的耦合窗位置，可以有效控制比例頻寬和抑制高階的模態，因此可以實現雙模SIW雙工器。
第二個電路為調整三階基板合成波導雙工器中的單模共振腔，藉由矩形波導截止頻率公式可以得知腔體寬長比、頻率比和模態發生順序的關係，設置耦合窗口在腔體中心以及諧波交錯，使通帶外的抑制效果更好，透過將輸出端口放置在電場最弱的地方可以達到一定的隔離度實現寬阻帶雙模SIW雙工器。
第三個電路為三階基板合成波導雙頻帶濾波器，使用與第二片相同的設計方法，耦合窗口以及透過腔體長寬比，諧波交錯這兩種方法，可以實現寬阻帶SIW雙頻帶濾波器。

This thesis introduces a substrate integrated waveguide (SIW) third-order diplexer. The orthogonal modes of 〖TE〗_102 and 〖TE〗_201 in a dual-mode cavity are exploited to realize the dual channel transmission. Two third-order SIW filter with different central frequencies and fractional bandwidths are synthesized and designed. both the central frequencies and fractional bandwidths of the two channels can be designed flexibly and independently by controlling the resonant frequencies and mutual couplings of cavities, especially dual-mode cavity.
The first circuit consists of two dual mode cavities and two single mode cavities. The central frequencies are 12 GHz and 14GHz, and the 3dB fractional bandwidth is 5% and 4.4%, respectively. Based on the properties of these orthogonal dual mode cavities, adjusting the length and width of the feeding line at the input/output port and adjusting the position of the coupling window between the dual-mode cavity and the single-mode cavity can effectively control the fractional bandwidth and suppress higher-order modes. In addition, the position of the coupling window between the dual-mode resonator and the single-mode resonator could help spurious higher order modes. Thus, a dual-mode SIW duplexer can be implemented.
The second circuit uses rectangular single mode cavity to replace the first one's square cavity. The relationship between the cavity W/L, the frequency ratio and mode occurrence sequence can be known by the cut-off frequency formula of rectangular waveguide. The coupling window is set at the center of the cavity and use the harmonics staggered to suppress the performance of outside the passband. Wide stopband dual mode SIW diplexer can be realize
The third circuit is a wide stopband third-order SIW dual-band filter, designed using the same method as the second one. In addition, by two kinds of suppression techniques, the harmonic staggered technique and centered coupling windows, wide stopband SIW dual-band filter can be achieved.

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