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A Low Phase-Noise X -Band MMIC VCO Using High-Linearity and Low-Noise Composite-Channel {\hbox {Al}}_{0.3}{\hbox {Ga}}_{0.7}{\hbox {N/Al}}_{0.05}{\hbox {Ga}}_{0.95}{\hbox {N/GaN}} HEMTs

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6 Author(s)
Cheng, Z.Q. ; Dept. of Electron. & Comput. Eng., Hong Kong Univ. of Sci. & Technol. ; Yong Cai ; Jie Liu ; Yugang Zhou
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A low phase-noise X-band monolithic-microwave integrated-circuit voltage-controlled oscillator (VCO) based on a novel high-linearity and low-noise composite-channel Al0.3Ga0.7N/Al0.05Ga0.95 N/GaN high electron mobility transistor (HEMT) is presented. The HEMT has a 1 mumtimes100 mum gate. A planar inter-digitated metal-semiconductor-metal varactor is used to tune the VCO's frequency. The polyimide dielectric layer is inserted between a metal and GaN buffer to improve the Q factor of spiral inductors. The VCO exhibits a frequency tuning range from 9.11 to 9.55 GHz with the varactor's voltage from 4 to 6 V, an average output power of 3.3 dBm, and an average efficiency of 7% at a gate bias of -3 V and a drain bias of 5 V. The measured phase noise is -82 dBc/Hz and -110 dBc/Hz at offsets of 100 kHz and 1 MHz at a varactor's voltage (Vtune)=5 V. The phase noise is the lowest reported thus far in VCOs made of GaN-based HEMTs. In addition, the VCO also exhibits the minimum second harmonic suppression of 47 dBc. The chip size is 1.2times1.05 mm2

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Microwave Theory and Techniques, IEEE Transactions on  (Volume:55 ,  Issue: 1 )