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    Theory and bandwidth enhancement of cascaded double-stage distributed amplifiers
    (2010-01-01)
    Worapishet, Apisak
    ;
    Roopkom, Ittipat
    ;
    Surakampontorn, Wanlop
    Theoretical analysis and bandwidth enhancement of the cascaded double-stage distributed amplifiers (CDSDA) are presented. The characteristics of the general cascaded multi-stage distributed amplifiers (CMSDA) with open idle drain terminations at intersections for a high gain are investigated with lossy artificial lumped line models. This reveals the inherent bandwidth limitation of the CMSDA due to interference from the reverse wave reflection at the open drain terminations. To achieve simultaneous high gain and bandwidth, drain line impedance tapering is introduced to enable a counterbalance of the reverse wave by partial reflection of the forward wave at each of the impedance junctions. Detailed analysis and design considerations are provided where it is shown that typical parasitic drain capacitance of transistors makes the drain line tapering practically viable for the CMSDA up to the double-stage configuration. Extensive validation of the theoretical analysis and the tapered drain line technique are given through the experiment of a 3.2 GHz 25.2-dB hybrid CDSDA, and through the simulation of a 13.8 GHz 14-dB CDSDA using a 0.18 μm CMOS process. © 2006 IEEE.
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    Probe-fed rectangular ring antenna with a cross-strip for low cross-polarization
    (2006-05-01)
    Srimoon, Duang Arthit
    ;
    Phongcharoenpanich, Chuwong
    ;
    Krairiksh, Monai
    In this paper, a probe-fed rectangular ring with a cross-strip for wireless local-area network system is proposed. The antenna is analyzed by using the three-dimensional finite-difference time-domain method. The effects of various parameters on the characteristics of the antenna are studied. The computed and measured results for the return loss and co- and cross-polarization patterns are presented and compared. A prototype antenna operating at 2.44 GHz shows an impedance bandwidth (2:1 VSWR) of 13.06% and a gain of 9.5 dBi. Good radiation characteristics, including a cross-polarization level in both E- and H-planes greater than 26 dB and a front-to-back ratio (F/B) of radiation pattern greater than 16 dB, have been obtained. © 2006 IEEE.
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    A couple microstrip antenna employing serrated coupling
    (2005-02-01)
    Saksiri, W.
    ;
    Krairiksh, M.
    Microstrip antenna is suitable for mobile handsets due to its light weight and compactness. The disadvantages of narrow bandwidth is necessary to be improved for modern wireless communication systems. This paper proposes the serration of coupled microstrip antenna to improve in the impedance characteristics. Return loss of this antenna is analyzed in terms of serration. The obvious measured characteristics improvement can be observed. They are found to be useful for practical wireless communication systems.