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is obtained with ⌬L ϭ Ϫ1.5 mm. Figure 7 shows the results of the adjustments. CONCLUSIONInvestigations on two-segment DRAs have been presented in this paper. The resonant frequency was predicted by a new method. An optimum lower-segment design was introduced. A fast and efficient design algorithm which prevents a futile time-consuming trial-and-error process was demonstrated using these methods. Impedance bandwidths of up to 30% were achieved with the optimum design. Two numerical methods were used to examine the performance of the methods. The simulation results are in good agreement and confirm the proposed methods. Wide impedance bandwidth, compact size, and lack of metal in the antenna structure (for high radiation efficiency) contribute to make TSDRA a useful element in high-frequency fixed-broadband wireless applications such as LMDS. Recently, the number of dual-band handset phones capable of operating at two different cellular systems has increased. A handset phone available for dual-frequency bands requires the antenna to operate equally well at both frequency bands. Also, the antenna is required to have small size, light weight, high radiation efficiency, and wide bandwidth. In order to satisfy these requirements for each band, PIFAs have limitations in both bandwidth and antenna height (6 -8 mm from the substrate) [1]. Those structures cannot provide easy placement of the antenna on the substrate in a practical mobile phone. However, planar-type antennas are relatively easy to manufacture in a very accurately repeatable way. Therefore, the planar-type antenna can be considered one of the best candidates to meet these criteria. For the planar-monopole antenna, a variety of designs has been also reported [2,3]. This paper presents an internal dual-band antenna with a modified ground plane. This antenna is very suitable to be integrated on the circuit board of a communication device, leading to the attrac- tive feature of occupying very small volume in the system. In addition, with the use of this kind of printed monopole antenna, a concealed antenna for the system can be obtained. Thus, no protruding portions of the antenna appear [4,5]. In this paper, the measured data are compared with the simulation results in order to validate the proposed design methods. The descriptions and design considerations of the proposed antenna are presented in detail. ANTENNA CONFIGURATIONThe geometry of the proposed internal dual-band antenna for CDMA/PCS applications is shown in Figure 1(a). This novel antenna is mounted on FR-4 substrate whose permittivity is 4.6 and dimensions are 80 ϫ 40 mm. In Figures 1(b) and 1(c), segment[A] is a ground part of the antenna top plane, which is electrically shorted with bottom ground segment [E] through the via hole. Part [B] is a feeding point where the inner conductor of the feeding coaxial cable is directly connected. The outer conductor of the feeding coaxial cable is connected through segment [A]. In order to expand the bandwidth, part [C] of signal line is fabricated as a righ...

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