Chih-Kai Wu

National Chiao Tung University, Hsinchu, Taiwan, Taiwan

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Publications (5)2.81 Total impact

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    ABSTRACT: Wideband downconversion mixers are demonstrated by using both 0.35-μm SiGe heterojunction bipolar transistor (HBT) and 2-μm GaInP/GaAs HBT technologies. A micromixer topology is implemented in the RF port while a differential type shunt–shunt feedback amplifier and a differential-to-single CE-CC output buffer are used in the IF stage. The frequency response analysis and systematic measurement approach for a wideband Gilbert mixer are proposed in this article for each individual stage of local frequency (LO), radio frequency (RF), and intermediate frequency (IF). The differential LO signals are generated by several off-chip 180° hybrids to cover more than 8:1 bandwidth. The SiGe HBT Micromixer achieves the conversion gain of 6 dB, IP1dB of −17.5 dBm, and IIP3 of −7 dBm with the 3.3-V supply voltage and the power consumption of 37.5 mW. On the other hand, the GaInP/GaAs HBT Micromixer achieves the conversion gain of 25 dB, IP1dB of −25 dBm, and IIP3 of −15 dBm with the 5-V supply voltage and the power consumption of 50 mW. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2254–2257, 2008; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.23642
    Microwave and Optical Technology Letters 06/2008; 50(9):2254 - 2257. · 0.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A wideband downconversion mixer is demonstrated using 0.35-mum SiGe heterojunction bipolar transistor (HBT) technology. A micromixer topology is implemented in the RF port while a differential type shunt-shunt feedback amplifier and a differential-to-single CE-CC output buffer are used in the IF stage. The frequency response analysis and systematic measurement approach for a wideband Gilbert mixer are proposed in this paper for each individual stage of local frequency (LO), radio frequency (RF), and intermediate frequency (IF). The differential LO signals are generated by several off-chip 180 degree hybrids to cover more than 8:1 bandwidth. The downconversion Gilbert mixer achieves the conversion gain of 6 dB, IP<sub>1</sub> <sub>dB</sub> of -17.5 dBm, and IIP3 of -7 dBm. The power consumption is 37.5 mW at 3.3 V supply voltage.
    Microwave Conference, 2007. APMC 2007. Asia-Pacific; 01/2008
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    ABSTRACT: This paper demonstrates a low-voltage wideband downconverter along with an integrated transformer RF balun using the 2-mum GalnP/GaAs HBT technology. This transformer is a symmetric type and plays a role as a single-to-differential balun. Without the parasitics between the transformer and the substrate, the transformer can work at higher frequencies. This transformer downconverter operates from 1.5 GHz to 14 GHz with around 20-dB conversion gain and 1.8-GHz IF 3-dB bandwidth. The frequency range of the mixing operation is wide and covers the digital video broadcasting via satellite (DVB-S) bands. This mixer hence is useful for DVB-S applications. Since there is no dc voltage drop on the transformer, the voltage supply of the mixer core is only 2.4 V and the current consumption is approximately 8.6 mA. The chip size of the entire mixer is 1 mm times 1 mm while the transformer occupies the estate of 150 mum times 150 mum.
    Microwave Symposium, 2007. IEEE/MTT-S International; 07/2007
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    ABSTRACT: A single-ended wideband downconversion Gilbert micromixer is demonstrated in this paper using 0.35-mum SiGe BiCMOS technology. A transimpedance amplifier with resistive feedback is utilized in the IF stage while a broadband Marchand balun is employed to generate wideband differential local oscillator signals. The planar Marchand balun topology employed in this paper can generate truly balanced signals even in the presence of the lossy low-resistivity (~10 Omegamiddotcm) silicon substrate. A systematic approach to measure the frequency response of each individual stage in a Gilbert mixer is developed in this paper. This single-ended wideband mixer has the conversion gain of 15 dB, IP<sub>1dB</sub> of -19 dBm, IIP<sub>3</sub> of -7 dBm, and the noise figure of 13 dB. The mixer works from 3.5 to 14.5 GHz
    IEEE Transactions on Microwave Theory and Techniques 01/2007; · 2.23 Impact Factor
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    ABSTRACT: A single-ended wideband downconversion Gilbert micromixer is demonstrated in this paper using 0.35-mum SiGe BiCMOS technology. Because of the wideband matching property of the micromixer, it can perform broad frequency translation. The TIA is utilized in the IF stage while a broadband Marchand balun is employed not only to generate differential LO signals but also to reserve the wideband operation of the mixer. This single-ended wideband mixer has the conversion gain of 15 dB, IP<sub>1dB</sub> of -17 dBm, and IIP<sub>3</sub> of -6.5 dBm and works from 3.5 to 14.5 GHz. The input return loss is below -14 dB and the chip size is 1times1 mm<sup>2</sup>
    Microwave Symposium Digest, 2006. IEEE MTT-S International; 07/2006