Ka 頻帶平衡交叉式二極體混頻器與X頻帶次諧波電阻性混頻器包含低雜訊放大器

Abstract

本論文主要是設計製作了兩種混波器 , 一為毫米波ka頻帶交叉平衡式二 極體波導混波器 , 一為微波X頻帶次諧波電阻性電晶體混波器 ,這包括 RF前級低雜訊放大器 ; 非線性CAD軟體用來模擬設計 ,並且量測及比較其 特性.首先 , 完成一個Ka頻帶 , 具低轉換損耗 ,高LO-RF-IF三端隔絕的 平衡式波導混波器 , 此種混波器非常適合在毫米波 , 因其以具低損秏 ,低散射的懸吊式傳輸線做電路 . 這種混頻器線路非常適合用於積體電路 技術 ,重量輕 , 體積小 , 且堅固 , 可適用於一般通訊系統 . 實驗結果 顯示RF從32到34GHZ , 轉換損耗小於8dB ,三端隔絕至少22dB.其次 ,我們 設計一種新的電阻性混頻器 , 此種混頻器的轉換損耗跟二極體混波器差 不多 ,但有較低的雜訊度 , 很高的IP3及P1-dB , 它利用零閘端偏壓的 MESFET通道電阻來完成頻率轉換 , 這個通道電阻具有很線性 , 很低的交 互調變特性 . 為了知道其 特性及能力, 一開始先設計一個單一MESFET 在X頻帶的電阻性混波器 , 其實驗結果顯示RF 從9.5到11GHZ , 轉換損 耗小於9dB ,三階交互調變輸出點是16.9dBm , 一dB壓抑輸出點是4.5dBm ;接著設計一個X頻帶半諧波電阻性混波器 , 此種混頻器的LO頻率只 須 一半 , 且可以抑制A-LO雜訊 , 由於LO本身相消 , 隔絕度很高 . 其實驗 結果顯示RF從 9.5 到10.5GHZ , 轉換損耗小於11dB.最後 , 我們為這個X 頻帶混頻器設計一個兩級的RF前級低雜訊放大器 ,實驗結果顯示其在10.5 GHz有20dB的增益 , 2dB的雜訊度 , 大於20dB的輸入及輸出反射損耗, 及 在整個頻帶上的穩定. Two type of different mixer are designed,Fabricated,and measured in this thesis. One is the millimeter-wave Ka-band cross-bar waveguide balanced diode mixer,the other is the microwave X-band subharmonically resistive mixer, the two-stage RF low-noise prea- mplifier are also made for the X-band mixer. The nonlinear CAD tools are used to simulate their performance. Comparison of these mixers are also discussed. The first type of the mixer is a ka-band low-conversion loss, high LO-RF-IF isolation balanced cross-bar waveguide diode mixer. The suspended stripline circuit is used, it is very suitable for millimeter-wave because of its low dilectric loss and low disper sion. The use of hybrid circuit technologies and beam- lead diodes provides the advantage of low cost, light weight and small size which is suitable for communication systems. Experimental results from 32 GHz to 34 GHz exhibits a conversion loss of less than 8 dB,and more than 22 dB isolation. The second type of the mixer is a new type of resistive mixer. The mixer conversion loss is the same as the diode mixer, the noise figure is lower than the diode mixer;and the IP3 and P1-dB is higher than the diode mixer, which uses the zero drain bias channel resistance of a GaAs MESFET to achieve frequency mixing. This channel resistance is high linear,very low intermodulation can be achieved. To understand this mixer, first, we design a single MESFET X-band resistive mixer. The mixer conversion loss is less than 9 dB from 9.5GHz to 11 GHz, 16.9 dBm output third- order intermodulation intercept point, and 4.5 dBm output 1-dB compression point. After this single-end mixer,a subharmonical MESFET X-band resistive mixer is made, the mixer LO-frequency is only half of the RF frequency. The AM-LO noise is suppressed. A high isolation is obtained intrinsically due to LO-cancellation. The conversion loss is less than 11 dB from 9.5 Hz to 10.5 Hz.