在本篇論文中，我們提出以假晶式高電子移動率電晶體 (PHEMT) 元件設計的主動和被動的單晶微波積體電路 (MMICs) 新的設計電路，包括混頻器、低雜訊放大器和高功率放大器。由於傳統PHEMT 特性上的限制 ，我們提出新式通道的變晶式高電子移動率電晶體 (MHEMT) 結構，在X 頻帶之放大器應用上，有較大的小訊號增益及閘極電壓操作範圍。
首先，為了解決高頻高輸出功率的本地振盪器不易達成，我們設計毫米波頻帶的次諧波混頻器，我們利用了反並聯式配對二極體架構，設計了降頻次諧波混頻器，在射頻頻率由26 至38 GHz 的頻段內皆有良好之射頻及本地震盪源對中頻隔離度，其隔離度在頻段內皆大於20dB，而其最小轉頻損耗為13.7dB。
在Ku 頻帶低雜訊放大器應用上，我們設計了使用自偏壓式電路之三級低雜訊放大器，操作頻率範圍為14-18 GHz，不僅可以使用單一電源操作，同時提供溫度補償效果，有效地降低隨溫度影響的增益變化。另外在功率放大器方面，為了軍事通訊系統的需求，我們設計具有6-18 GHz 寬頻之功率放大器，為了改善增益及輸出功率的平坦度，我們提出一個新的匹配架構，使得功率放大器同時提供高的功率附加效率。此外，由我們設計的AlGaAs/InGaAs PHEMT 放大
器可以看出在高頻操作時遭遇較小的增益的問題，由於傳統的AlGaAs/InGaAs PHEMT 均勻式通道結構，“銦＂濃度較低，使得元件有較小的電壓增益，造成在放大器電路應用上，無法獲得較大的小訊號增益，而且在不同的閘極偏壓下，電壓增益的變化較大，所以為了在微波積體電路的應用上，我們在變晶式（metamorphic）高電子移動率電晶體中，設計了新式的通道結構，在擁有高增益的特性下，同時改善衝擊游離的現象、紐結效應及崩潰電壓特性。新型通道結構包含了銦組成為0.35 之的砷化銦鎵均勻式通道和銦組成為漸變式對稱式通道（0.5→0.65→0.5）的變晶式高電子移動率電晶體，由於通道有較大的平均能隙，元件的崩潰電壓皆大於15 V。同時，由對稱漸變式通道結構，可以明顯改善閘極工作電壓擺幅特性達到1.3 V
最後，我們配合S參數量測的數據，建立元件的小訊號模型，透過軟體模擬設計具有X頻帶（9-12 GHz）操作的增益放大器。與X頻帶放大器比較下，以變晶式高電子移動率電晶體設計之放大器可證實可擁有佳的增益，另外，對稱式通道之變晶結構高電子移動率電晶體，由於改善閘極工作電壓擺幅特，在不同閘極偏壓下，亦可以獲得優異且穩定之小訊號增工作特性。

This dissertation presents new designs of Monolithic Microwave Integrated Circuits (MMICs), including sub-harmonic mixer, low-noise amplifier, and high-power amplifier. Besides, in order to improve the device performance suitable for MMIC implementations, as compared to conventional AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT), we further investigate metamorphic HEMT (MHEMT) with new channel designs. For X-band amplifier designs and simulation, the proposed circuit demonstrates improved performances of small-signal gain and gate-voltage operating range.
First, we have designed a sub-harmonic mixer to prevent mixer for being operated at high frequency and high power oscillator. We have proposed an anti-parallel diode pair (APDP) sub-harmonic down-conversion mixer that has successfully shown minimum conversion loss of 13.7 dB and high RF/LO to IF isolations of 20 dB in Ka-band.
Then, for the low-noise amplifier MMIC applications, the designs of a self-bias pHEMT device with compact source capacitors and resistors have been proposed. We have successfully achieved a single-supply Ku-band three-stage low noise amplifier MMIC. Thermal sensitivity coefficients for the small-signal gain and the noise figure are superiorly low to be -0.023 dB/°C and 0.003 dB/°C. Next, for military and multipurpose system applications, a 6-to-18 GHz broadband power amplifier has been designed and fabricated. With a new matched network, the proposed power amplifier has improved the flatness characteristics of small-signal gain and output power. In addition, according to our devised AlGaAs/InGaAs pHEMT amplifier, the circuits have shown low small-signal gain at high frequency application. It is because of low “In” content in conventional uniform InGaAs channel pHEMT to degrade the device characteristics. Furthermore, the devised amplifiers have also shown gain variations at different gate biases. Consequently, for MMIC application, we have proposed MHEMT designs with novel channel engineering to relieve the impact-ionization effects within the channel, and to improve the breakdown voltage and kink effects at the same time. The proposed MHEMT devices include In0.35Al0.65As uniform-channel MHEMT and InxGa1-xAs MHEMTs with a V-shaped
symmetrically-graded InxGa1-xAs channel (x =0.5 → 0.65 → 0.5). The gate-drain breakdown voltages are improved to be higher than 15 V. Moreover, MHEMT with a symmetrically-graded channel has successfully demonstrated enhanced gate-voltage swing (GVS) of 1.3 V.
Finally, based on the measured S-parameters, we have extracted and established the small-signal device model for the symmetrical-channel MHEMT, such that to design a gain amplifier for X-band (9 ~ 12 GHz) application. The MHEMT amplifier has shown superior small-signal gain per stage over the X-band frequency regime, as compared to other amplifiers. Due to improved GVS characteristics of the symmetrical-channel MHEMT, superior gain linearity of the studied MMIC amplifier has been successfully accomplished.

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