利用SiNx/Si薄膜結構發展在次毫米波段接收機的本地振盪源分流器

Abstract

由於大型電波望遠鏡的造價昂貴，其觀測時間一直以來都是個相當珍貴的資源。多像素的外插接收機是一個可以提升電波望遠鏡單位時間資料接收量、並減少每個天體所需觀測時間的方法。而緊緻的多像素模組是一個建立大型多像素陣列的關鍵。依據外插接收機的接收結構，在這個多像素模組中，必須要有一個元件來處理複數本地震盪訊號(LO)。本論文利用SiNx/Si薄膜結構來發展在200 GHz到240 GHz的LO訊號分流器，以在晶片上的平面電路來處理LO訊號的分流來讓像素的排列可以更加緊緻。

我們設計了三片晶片，分別是一片1-to-2的LO等效功率分配器晶片做為基礎的分流結構測試，以及兩個不同傳輸線條件的1-to-1的LO功率發射器晶片作為分流結構的量測基準。LO等效功率分配器主要由三個結構所組成，在SiNx/Si薄膜上用來連接波導與平面電路的過度探針(發射器)、作為平面傳輸線的共面波導(CPW)、以及讓訊號分流的CPW形式的威爾金森功率分配器。我們以HFSS電磁模擬軟體來驗證這些結構的可行性。其計算出功率分配器的S11與S21(S31)在操作頻率分別小於-17 dB和大於-5 dB。這三個晶片已通過製程被成功製造出來，而薄膜製程的細節亦會在本論文中討論。同樣地，晶片封裝模組的設計與量測環境的設定亦囊括在論文中。其中一個20mm 1-to-1晶片的量測顯示其性能有-1.3 dB與-5.5 dB兩種可能，這兩個數值是相對於等長的矩形波導的性能。而造成量測上有這兩種可能的原因仍在調查。

Multipixel receiver is an intuitive way to increase the mapping speed of radio telescope and reduce the observation time of each target. To build the large format array, a compact and easy to be scaled up multi-pixel receiver module is crucial. Multiple local oscillator (LO) source is a necessary part in this module. In this thesis, we will present our study on chip-type LO power distributor's work at the frequency from 200 GHz to 240 GHz, which is based on SiNx/Si membrane structure.

We designed a 1-to-2 LO power divider as our starting point. Two types of 1-to-1 LO power transmitters are also designed as the baseline. The LO power divider includes a transition probe (emitter) on SiNx/Si membrane in the waveguide, the coplanar waveguide (CPW) transmission line, and Wilkinson power divider in the CPW form. The design of these elements was simulated by an EM simulator, HFSS®. The calculated S11 and S21 (S31) of power divider would be below -17 dB and higher than -5 dB respectively. The fabrication process of membrane structure has been developed, and it will be explained in detail in this thesis. The housing block design and measurement device setting are also included. One type of the 20 mm 1-to-1 coupler has been measured and presented in the thesis. The measurement result shows two possibilities of chip's performance. Comparing to the isometric rectangular waveguide, one is -1.3 dB, and the other is -5.5 dB. The reason for these two possible results is still under investigation.