Study of High Electron Mobility Transistors Microwave Circuits and Devices for MMIC Applications
| Autor: | Shu-Jenn Yu, 余書振 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 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. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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