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| Improvement of TWT Nonlinearity with a Field Effect Transistor Predistortion Circuit |
| Hu Xin①③ Wang Gang② Wang Zi-cheng② Luo Ji-run① |
①(Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China)
②(Space Traveling Wave Tube Research and Development Center, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China)
③(Graduate University of Chinese Academy of Sciences, Beijing 100039, China) |
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Abstract In this paper, a Field Effect Transistor (FET) operating in close to cut off frequency is used to replace the attenuator and the phase-shifter in most TWT predistortion circuit, which can realize good control for the amount of gain expansion with little phase expansion variation. The experiments with practically designed circuit show that, in the frequency range of 8.38~8.58 GHz, about 6 dB gain expansion and 45 degrees phase shift can be compensated for the TWTA saturation response in input power dynamic range, and the improvement of about 15.4 dB Carrier to Intermodulation (C/IM) at TWTA Output Power Back Off (OPBO) of only -3 dB can be reached with the linearizer.
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Received: 28 July 2010
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Corresponding Authors:
Hu Xin
E-mail: huxinhust@126.com
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2011, Vol. 33 
