In this article, a novel design of band‐notched monopole antenna with U‐shaped slot capable to work for both WLAN (2.4 – 2.5 GHz) and UWB (3.1‐10.6 GHz) applications is proposed. This antenna comprises the multilateral structure of the circular radiating patch with U‐shaped slot fed by a 50Ω microstripline feed and on bottom of the antenna a partial ground plane is used. A U‐shaped slot is etched on the circular radiating patch. With this design the antenna gives the WiMAX (3.2‐4.2 GHz) band‐notched characteristics. The parametric study of the proposed antenna is investigated using the Ansoft HFSS software and the results are compared with experimental results and they are good in agreement with each other. The antenna can operate in the range of 2.36 to more than 12 GHz with notched band of 3.3‐4.20 GHz for 3.5 GHz WiMAX. Also, this antenna exhibits a good omni‐directional radiation patterns and stable peak gain over the desired frequency bands which will satisfy the UWB communication system. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2496–2501, 2015

The effect of slot on patch and on ground plane of rectangular microstrip antenna for effective size reduction, wide bandwidth, and high gain has been presented. A 60.57% of virtual size reduction is achieved by taking ground plane same as that of patch on another similar substrate and by keeping 1-mm air gap between them. Furthermore, 51% of bandwidth and 8.73 dB of gain are achieved by embedding group of slots on the patch, wide slot on the ground plane and by doubling the thickness of substrate.

0.02 mm. The simulated and measured result of frequency response and phase response are shown in Figures 10 and 11, respectively. Good agreement is also observed between the simulated and the measurement results. The measured results of the miniaturized coupler are summarized in the Table 1. CONCLUSIONSAn extremely compact dual-band branch-line coupler operating in 0.9 GHz and 2.4 GHz is presented in this study. The size of this miniaturized coupler is reduced by 74% of the circuit dimension compared with the origin design with good circuit performance. Response of the miniaturized dual-band branch-line coupler and its equivalent circuit are in good agreement, and optimizing circuit performance using the circuit model could be implemented. Furthermore, the design is without lumped elements, via-holes, bound wires, and can be easily fabricated by using standard PCB etching processes, making this dual-band coupler suitable for MIC and MMIC applications. pedance bandwidth of microstrip antennas [1][2][3]. Among all the techniques, the aperture coupled feeding technique is simple and more effective as it has the freedom in designing the required feed line to energize the elements in enhancing the impedance bandwidth. Since in the aperture coupling the microstrip line feed and the antenna elements are separated by a ground plane, the effect of the feed line radiation on the antenna radiation characteristics is less, which improves the quality of antenna radiation pattern [4]. Further use of parasitic element in the form of gap-coupled to the radiating elements and use of slots will also effective in enhancing the impedance bandwidth. This concept has been utilized in designing the four-element gap-coupled slot rectangular microstrip array antenna (FGSRMSA). The obtained experimental results are discussed and presented in this letter. DESIGN AND EXPERIMENTAL DETAILSIn the present study, the antennas are fabricated on low cost glass epoxy substrate material of thickness h ϭ 1.66 mm and permittivity r ϭ 4.2. The geometry of conventional corporate fed four-element gap-coupled rectangular microstrip array antenna (FGRMSA) is as shown in Figure 1. The antenna geometry consists of radiating elements of length L R and width W R . A common parasitic element of length L P and width W P is placed between the radiating elements along their widths, which forms the gap coupling. The distance between the parasitic and radiating elements S is optimized and is taken as 0.025 g , where g is the operating wavelength in cm. The spacing between two radiating elements D R is kept at a distance of 1.5 0 /2. Usually in the array configuration the spacing between the two radiating elements is kept at a distance of 0 /2 for minimum side lobes [5]. But in this case, it is difficult to accommodate corporate feed arrangement between the two radiating elements when distance is 0 /2. If this distance is increased, accordingly the feed line has to be extended, which may increase radiation losses in the feed line. Hence, corporate feed arrangement...

This paper presents the design of a simple rectangular microstrip antenna (RMSA) for wide bandwidth and large virtual size reduction. The conventional RMSA has been modified by using only microstripline feed with reduced substrate area. The modified RMSA gives 3.71% of bandwidth and resonates at 4.59 GHz. This bandwidth has been enhanced to 90.70% with a virtual size reduction of 33.33% by using a ground plane 64.50% smaller than the ground plane used in the modified RMSA. If the ground plane is reduced to 74.50% the antenna gives a highest virtual size reduction of 50%. The enhancement of bandwidth and virtual size reduction are achieved without altering the size of the rectangular patch and nature of broadband radiation characteristics. The proposed antennas are simple in their design and they may find application in WLAN.

between Q avg and Q t can be obtained with only 1024 samples. This scheme is able not only to reduce the required memory size in the monitoring unit but also to provide estimation for the Q-factor faster than the conventional scheme. CONCLUSIONThis article proposes a novel sampling technique for improving the sampling uniformity with a low number of sampling points. The proposed technique can increase the measurement convergency and accuracy of Q avg by adding deterministic jitter to the sampling pulses. This makes the sampled histogram close to the one obtained with a large number of sampling points. Consequently, we can obtain faster Q-factor monitoring by reducing the data points in a histogram. It also reduces the hardware complexity by reducing the required memory size. The monitoring results are quite independent of the difference between the data rate and the sampling rate. ACKNOWLEDGMENTThis work is supported by the National Science Council (NSC) of Taiwan (R.O.C.) under grants NSC94-2213-E002-061 and NSC95-2221-E-002-194. In recent years, the use and interest in microstrip antennas (MSAs) has become widespread because of its significant merits of smallsize, light-weight, low-profile, low-cost, direct integrability with microwave circuitry, and the ability to conform to the surface of a host object. One of the most attractive features of the equilateral triangular microstrip antenna is that, the area necessary for the patch becomes about nearly half when compared wtih rectangular, square, or circular MSAs designed for the same frequency. Such features make MSAs useful for many applications in radar and wireless communication systems [1]. However, one of the principle limitations of MSAs is their narrow impedance bandwidth. Many techniques are available in the literature for the enhancement of impedance bandwidth of MSAs [2, 3]. One such technique is the use of aperture coupling. This technique is simple and more effective as it has the freedom in designing the required feed line to energize the elements for enhancing the impedance bandwidth. Since in the aperture coupling the microstrip-line feed and the antenna elements are separated by a ground plane, the effect of the feed line radiation on the antenna radiation characteristics is less, which improves the quality of antenna radiation pattern [4]. Further, the slot-loading technique is also effective in broadening the impedance bandwidth. Hence in this study, the aperture coupling and slot loading techniques has been used in designing the antennas. The experimental results are presented and discussed. DESIGNING AND EXPERIMENTAL DETAILSThe proposed antennas are designed using low cost glass epoxy substrate material S 1 of thickness h ϭ 1.66 mm and dielectric constant r ϭ 4.2. The use of high dielectric constant substrate material reduces radiation losses because most of the EM-field is concentrated in the dielectric between the conductive strip and the ground plane. Another benefit of having a high-dielectric constant is that the antenna size decreases ...