can be observed that the radiation patterns are not uniform totally in azimuth plane. This may be due to two factors. One is the current distribution is not totally uniform around the central axis, because the feeding point departs from the central point. The other is that the ground plane is a little smaller in this design. Figure 9 shows the simulated and measured elevation radiation pattern (x-z plane) at 2.11 and 2.29 GHz. As revealed in elevation pattern, approximations to a conical beam patterns are achieved and the peak gain occurs at elevations of about 40 . The value of the null at 270 shows a great level in comparison with the simulated result, which is mainly caused by the parasitic effect of SMA connector and transmission line loaded at the back of this antenna. From Figures 8 and 9, it is seen that the antenna has similar radiation pattern for the two status of the PIN diode. The measured gains of 4.2 and 3.5 dBi are achieved at 2.11 and 2.29 GHz, respectively. The gain at 2.29 GHz is a little smaller than that at 2.11 GHz due to the insertion loss of the PIN diode [9].ABSTRACT: In this article, a novel microstrip lowpass filter with complementary split-ring resonators (CSRRs) is presented. By properly controlling the width of the transmission line and rotating the angle of CSRRs, a wide stopband with sufficient rejection level can be achieved. The full-wave electromagnetic simulator IE3D is used; moreover, the prototypical microstrip lowpass filter is fabricated and measured. Simulated results and experimental responses are compared; moreover, the match between simulation and measurement validates the proposed structure.

In this article, a method is discussed to design and optimize a planar monopole antenna by particle swarm optimization (PSO) algorithm based on FEKO. The simple rectangular monopole antenna with an L slot is proposed for DCS-1800 (1.7-1.88 GHz), PCS-1900 (1.85-1.99 GHz), UMTS (1.92-2.17 GHz), WLAN (2.4-2.484 GHz), and WiMAX (2.305-2.69GHz) operations. Planar monopole antennas with characteristic of broad band can adequately cover the overall operating band (1.7-2.69 GHz). For the purpose of suppressing the interference from other systems, the PSO/FEKO method is employed not only to maintain the return loss less than -10 dB within the desired bandwidth but also to urge the S 11 at extreme frequencies equal to -10 dB, respectively. Details of the evolutionary design method of PSO based on FEKO are presented. The L-slot planar monopole antenna can be easily fabricated using a single metal plate, making the proposed antenna easy to construct at a low cost. Details of the experimental and theoretical results for the optimized antenna are presented and compared, testifying the validity of this design method.I.

A compact dual-band planar monopole antenna for 2.4/5GHz WLAN application is presented. The two resonant modes of the proposed antenna are associate with four slots which contribute to the upper resonant frequency and can reduce the size of the lower resonant length. The parametric study is performed to understand the characteristics of the proposed antenna. Experimental results show that the designed antenna can provide excellent performance for 2.4/5GHz WLAN system, including sufficiently wide frequency band, moderate gain, and nearly omnidirectional radiation coverage.

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