使用基板合成波導之帶通濾波器及振盪器研製

Abstract

在有線或無線通訊系統中，微波濾波器及振盪器皆是重要之關鍵電路元件。由於通訊應用的增加，5GHz 以下的頻段已漸不敷使用，所以須設計及發展更高頻段元件技術，以符合無線通訊之需求。隨著頻率愈高，就須克服更多問題，如電路損失，製作及量測等問題。為了要減少濾波器之損失，和降低振盪器之相位雜訊，本論文使用基板合成波導設計相關元件。 論文中使用基板合成波導共振腔，分別製作三種型式之帶通濾波器，及四種型式之振盪器。第一種濾波器操作在40~48 GHz，基板合成波導共振腔使用低溫共燒陶瓷材質，其饋入結構採用類似同軸線之探針激發方式，最低之插入損失為1.173 dB，而反射損失高於7 dB。第二種濾波器操作在30 GHz，基板合成波導共振腔亦使用低溫共燒陶瓷材質，其饋入結構採用類似同軸線之電流迴圈激發方式。此外，為了配合晶片量測，亦設計轉接電路，藉著使用此種饋入方式，可以不用任何耦合金屬連通柱或方形切角微擾，即可激發兩個正交模態。濾波器之最低插入損失在30.85 GHz 為2.211 dB，反射損失高於15dB，3 dB 頻寬約5.4%，其兩個傳輸零點分別在27.6 及32.45 GHz，插入損失皆高於33 dB。第三種濾波器操作在60 GHz，為串接兩個雙模共振腔，其中一個共振腔同時存在TE102 模態及TE301 模態，以產生一傳輸零點於通帶之左側，而另一共振腔同時存在TE102模態和TE201 模態，以產生一傳輸零點於通帶之右側。 在振盪器方面，皆用平行迴授之架構設計。第一個振盪器設計以圓形共振腔作為迴授電路，在11.79 GHz 之輸出功率為1.434 dBm，而偏移工作頻率100 kHz 之相位雜訊為-92.72 dBc/Hz。第二個振盪器設計以矩形共振腔作迴授電路，在11.79 GHz 之輸出功率為2.271 dBm，偏移工作頻率100 kHz 之相位雜訊為-85.23dBc/Hz。第三個振盪器設計以半波長微帶線諧振器作迴授電路，在12.12 GHz 之輸出功率為3.826 dBm，偏移工作頻率100 kHz 之相位雜訊為-75.31 dBc/Hz。第四個振盪器則設計以矩形共振腔作迴授電路，在9.94 GHz之輸出功率為4.274 dBm，而偏移工作頻率100 kHz 之相位雜訊為-100.8 dBc/Hz。最後，濾波器及振盪器之量測結果整理於表中。本論文以基板合成波導設計之帶通濾波器及振盪器，應有助於微波及毫米波頻段之無線通訊系統開發。

Microwave filters and oscillators are key components in wired or wireless communication systems. With the increasing wireless communication applications, the frequency band below 5 GHz become more and more intensive. Therefore, the research and development of components and technology in the higher frequency bands are essential to meet the needs of wireless communication. In the higher frequency design, problems require more efforts to overcome, such as circuit losses, difficulties of manufacturing, and measurement. In order to reduce the filter loss and oscillator phase noise, substrate integrated waveguide (SIW) is selected in this study instead of other transmission lines. In this thesis, three types of bandpass filters and four types of oscillators are designed with the use of SIW cavity. For the first kind of filter, a LTCC SIW cavity filter operated from 40 GHz to 48 GHz is designed. Its feeding structure is like the probe excitation using coaxial line. The lowest measured insertion loss is 1.173 dB and return loss is higher than 7 dB. For the second kind of filter, a LTCC dual-mode SIW cavity filter at 30 GHz is designed. Its feeding structure uses a current loop excitation integrated with a transition circuit for the probe measurement. Two orthogonal modes are designed to be excited in a single cavity without any perturbation of coupling vias or square corner cutting. The lowest measured insertion loss is 2.211 dB at 30.85 GHz, the return loss is higher than 15 dB, and the 3-dB bandwidth centered at 30.85 GHz is about 5.4%. The two transmission zeroes outside the passband are located at 27.6 and 32.45 GHz with insertion loss higher than 33 dB. For the third kind of filter, a bandpass filter at 60.5 GHz is designed with cascading two dual-mode SIW cavities. TE102 mode and TE301 mode are excited in one cavity to yield a transmission zero located at the left side of passband, whereas TE102 mode and TE201 mode are excited in the other cavity to yield the other transmission zero at the right side of passband. For oscillators, all of them are designed using parallel feedback structure. With the feedback of a circular SIW cavity, the first oscillator is measured to give 1.434 dBm output power at 11.79 GHz and phase noise of -92.72 dBc/Hz at 100 kHz offset from the carrier. The second oscillator using a rectangular SIW cavity is measured to give 2.271 dBm output power at 11.79 GHz and phase noise of -85.23 dBc/Hz at 100 kHz offset from the carrier. The third oscillator with the use of half-wavelength microstrip line resonator is measured to give 3.826 dBm output power at 12.12 GHz and phase noise of -75.31 dBc/Hz at 100 kHz offset from the carrier. The fourth oscillator with the use of a rectangular SIW cavity is measured to give 4.274 dBm output power at 9.94 GHz and phase noise of -100.8 dBc/Hz at 100 kHz offset from the carrier. Finally, the measured results of three bandpass filters and four oscillators are summarized in a table. All the findings and studies of this thesis on the implementation of SIW passive and active devices in the microwave and millimeter-wave ranges may have the potential in the applications of communication systems.