Abstract-A full wave spectral domain method of moment along with reciprocity theorem analysis of finite phased array of aperture coupled circular microstrip patch antennas is presented. Both the electric surface currents on the patches and the equivalent magnetic current on the apertures are considered. Results of reflection coefficient magnitude, active input impedance, active element gain, efficiency and pattern are provided for different array size and element separations. By optimizing the parameters of the array, a better scan performance can be achieved. Furthermore, a comparison is made between array of rectangular and circular patches, with equal patch surface area, and it is shown that the array of circular patches provide a better scan performance than the array of rectangular patches.

The slot antenna is attractive for use in many applications. These antennas have several useful properties such as wider impedance bandwidth compared with the microstrip patch antennas, and easier integration with solid-state, MIC, MMIC, and Micro Electro Mechanical Systems (MEMS). In this study, the novel wideband design of a coplanar waveguide fed fractal slot antenna is proposed and experimentally studied. The return loss, impedance matching and radiation pattern parameters of such a structure will be studied and in one case it would 936MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. INTRODUCTIONThese days, the Fractal structures are extensively used in the variety branches of science and technology. These non-Euclidean geometries exhibit some amazing behaviors such as self similarity, all because of their unique specifications. These fractal shapes have been used so far to achieve multi band radiating elements, increasing the band width of electrical equipments and decreasing the size of antennas. All these benefits are the consequences of a fact that, these geometries represent a certainly finite area, which is bounded in a theoretically infinite line. The fractal Koch shapes are the most representative examples of such antennas.Lots of studies were published in regard of broadening the bandwidth of coplanar waveguide antennas [1, 2]. In a work by Chiou et al. [2], a broadband design of a coplanar waveguide square slot antenna, which is loaded subsequently by four conducting strips was proposed. The obtained results shown that the impedance bandwidth, determined by 10-dB return loss can be reach to about 60%. The proposed antenna was quite simple and easy to fabricate but the return loss were always adjacent to Ϫ10 dB. This means that the antenna should be tuned in order to achieve more reliable values of return loss. In other hand, the cross polarization components of the radiation pattern couldn't be neglected in comparison with the co-polarization emissions. In another work by Bhobe et al. [3], a wideband coplanar waveguide antenna was demonstrated by creating a slot antenna with direct connection of internal and external conductors of the coplanar wave guide. Despite the fact that an impedance bandwidth of 57% was achieved, but the resulting structure is completely absolute when the application of active circuits with DC bias is required. In these cases, the direction contact of inner and outer conductors would result on a DC short circuit.The idea of coplanar antennas in shape of a Fractal Koch dipole where firstly proposed by Anagnostou et al. [4]. This work was in extension of another study, which is firstly proposed by Tzeremes et al. [5]. In these studies direct application of Fractal theory was imposed on a CPW slot antenna. The effects of fractal miniaturization in this type of antennas where explicit but these effects on bandwidth enhancement were negligible. For example, the bandwidth of the original study [5] were hardly boost to 9%.In Ref.[6], a printed wide-slot antenna fed by a s...

A micro electromechanical phase shifter base on the fractal geometries is proposed to work at Ku frequency band with at least 23% lower actuation voltage compared with the simple rectangular membrane counterparts. In this design the membrane of the switch is chosen to be a Koch fractal and then a distributed MEMS phase shifter is set up by cascading a distinct number of these switches. This phase shifter is analyzed to obtain its parameters such as differential phase shift, group delay, and insertion and return loss. It will be shown that this phase shifter could be used as a low loss and multi bit phase shifter system because of its low insertion loss and power consumption.

According to federal communication commission (FCC) rules, the 3.1 - 10.6 GHz band is allocated to the amateur ultra wideband (UWB) applications. On the other hand, the 5.15 - 5.825 GHz band is associated with the wireless LAN (WLAN) applications according to IEEE 802.11 and HIPERLAN/2 standards. Therefore, an unwanted intrusion will be expected between these two frequency requests. In This paper a comprehensive review will be done over a wide range of UWB microstrip antennas which all have the band notching property over the WLAN band to effectively avoid this interference. All the band notching techniques in the recent papers will be categorized in 4 distinct methods including the tuning stub, the shaped slot, the parasitic element, and the fractal geometry. A few typical papers will be introduced and evaluated in each category for declaration purposes. At last, a comparison will be done between these methods and the relative papers

Abstract-A 3-bit phase array system including phase shifter blocks and antenna elements has been developed on a coplanar waveguide (CPW) using micro electromechanical system (MEMS) technology. The non Euclidean Koch fractal geometry has been used to improve the frequency behavior of the entire system. It is shown that the fractal geometry makes the design to have lower profile, wider frequency bandwidth, and lower mutual coupling effects. It also decreases the actuation voltage of the MEMS switch elements. The fabrication process has been fully described and the measured values regarding every single block is presented.