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.

The antenna gains are shown in Figure 10. The proposed antenna possessed a moderate gain, and a sharp decrease of the gain is presented at the band-notched frequencies. CONCLUSIONA band-notched printed monopole antenna is investigated in this article, which presents a band-notched performance in the WLAN band by cutting a slot on the patch. Details of the proposed UWB and band-notched design are discussed, results of impedance bandwidth and radiation characteristics are given, and the parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated in this article. As have been shown that by adjusted the parameters of the antenna the width and location of the band-notched and the first resonant frequency can be tuned.

opening is also shown. As expected, in this case, the performance degradation is highly mitigated. These results indicate that the transition bandwidth is highly affected by the diameter D and the stub length, and the performance is effectively improved as the diameter D increases. To minimize the performance degradation due to the parasitic resonance, both the open stub inductance and the parasitic capacitance should be minimized. For the diameter of D ¼ 2.2 mm, wideband performance with a return loss less than 10 dB up to 21.7 GHz is achieved.