In this paper, a multi-band compact H-shaped

A new nondegenerate dual-mode microstrip patch filter structure is introduced. The proposed filter is based on a square microstrip patch with four slots etched in symmetrical form. Besides its simple structure, the filter has the advantages of small size and low loss. The full-wave IE3D package is used to analyse the proposed structure. Design curves that relate the mode resonance frequencies and fractional bandwidth against slot parameters are presented. A bandpass filter is designed, analysed and tested at 2.15 GHz. Experimental results show good agreement with theoretical results.

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A reduction in the overall size of the stepped impedance low pass filter is proposed in this article. The high impedance line sections are converted to T‐sections and the low impedance line sections are converted to π‐sections. Analysis and design equations for such conversions are presented. This method accomplishes a prominent size reduction in sharp response filters with multi‐stepped impedance sections. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2398–2403, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22766

Abstract-This paper presents a novel method to suppress the higher order harmonics in the microstrip patch antennas. A practical 0.75 GHz microstrip patch antenna is fed with a quarter-wave feedline designed by exploiting the dispersion properties of shunt-capacitorloaded transmission-line metamaterials. It is shown that two higher order harmonic modes at 1.25 and 1.5 GHz are completely eliminated. In addition, there is about a one-fourth reduction in the length of the impedance matching quarter-wave feedline.

In this paper, a new idea of reconfigurable 3 6 dB branch line coupler is proposed. The proposed coupler is tuned through a simple open and short circuit at the coupler's branches' edges. At the short edges case, a 3 dB branch line coupler is obtained. In this case, the coupler's branches are considered as microstrip transmission lines with 0.3 mm slot width which is etched in each coupler's branch. At the open edges case, the coupler's branches are considered as asymmetric coupled microstrip lines. In this case, a 6 dB branch line coupler is obtained. Both CST and IE3D simulators are used to optimize the reconfigurable 3 6 dB branch line coupler dimensions. As a prototypes, two BLCs are designed, analyzed and tested at the "on" and "off" states at 2.5 GHz.The measured S-parameters confirm the proposed concept of the reconfigurable 3 6 dB branch line coupler.

(c Ϫ b)/r is larger, the discrepancies between the present results and those given in [5,6] are larger for the even-mode case, and the maximum discrepancy is higher than 5%. This conforms with the feature of field distributions, because when aspect ratio (c Ϫ b)/r is larger, the even-mode fringe fields are stronger between the side ground plane and the shielded conductor for the present structure. Consequently, in this case these two structures are no longer comparable.Figures 3(a) and 3(b) show the odd-and even-mode characteristic impedances of the present CCPW structure as a function of the aspect ratio (d Ϫ c)/r with the ratio (b Ϫ a)/r as a parameter for r1 ϭ 1, r2 ϭ 12.9, a/r ϭ 0.1, (c Ϫ b)/r ϭ 0.05, respectively. The values calculated by [5] for the triple-coupled conductor-backed CPW line and by [7] for the CCPW with rectangular shielding are also given. It is observed from Figure 3 that when a/r and (c Ϫ b)/r are given, the characteristic impedance values of the odd-and even-modes for the present CCPW structure increase with the aspect ratios (d Ϫ c)/r and (b Ϫ a)/r. Moreover, for the odd-mode case, the deviations among the impedance values of those three structures are very small. This shows that the characteristics of the present structure are similar to those structures proposed in [5,7]. It is also found that for the evenmode case, when the aspect ratio (b Ϫ a)/r is larger, the results for present structure are in good agreement with those for the rectangular shielded structure, while larger deviations emerge between results for the present structure and those for the triple-coupled CPW line structure. This phenomenon may also be attributed to the increase of fringe fields, and verifies that the analysis used in this Letter is reasonable.

Abstract-A lowpass filter with a very sharp transition band using defected ground structures (DGS) is described. The lowpass filter was designed by using three dumbbell slots at the ground plane. Two of those dumbbell slots are the reshaped rectangular and the third dumbbell slot is an inverted triangle. The lowpass filter designed at cutoff frequency of 3.0 GHz, which is suitable for GSM900, GSM1800 and UMTS applications of the mobile communications. The equivalent circuits for the proposed lowpass filter and its corresponding LC parameters are given. The proposed lowpass filter provides a size of 33 × 30 mm 2 , and have good transition band with good performance in the passband and have wide rejection up to 9.25 GHz plus harmonic suppression in the stopband.Measurements results show good agreements with the simulated results.