In this paper, microstripcircularpatchantennas with four shorting pins are used as the array elements in order to reduce the excitation of the surface waves in the proposed dual frequency retrodirective array. This will minimize the mutual coupling between the array elements, improving the overall array performance by having higher gain, better radiation pattern, and better beam scanning (avoiding scan blindness). To obtain circular polarization, a narrow slot with a single feed is used. To obtain circular polarization with the narrow slot, it must be oriented at 45 ◦ to the feed axis and its length must be optimized in order to excite two orthogonal modes that have equal amplitudes and are 90 ◦ out of phase. Circular polarization is chosen for the wireless power transfer application to ensure devices receive the transmitted signal (the charging signal) regardless of their own antenna orientation. For wireless devices, the device’s own data signal (e.g., WIFI signal) can be used as the interrogating signal which the retrodirective array can use to direct its transmitted beam towards the wireless device for charging. In this work, we chose 2.4 GHz as the frequency of the interrogating signal and 5.8 GHz as the frequency of the transmitted signal used for power transfer. The goal is to have a system with the ability to scan the beam within a 60-degree sector, in order to maximize the power received by the devices within that sector.
Review of the literature shows that there has been a number of published papers on the subject of application of the phased array antennas [1–4], general analysis of phased array [5–8] and analysis of printed phased arrays such as probe fed dipole and rectangular patch antenna in an inﬁnite and ﬁnite array format [9–13]. Aperture coupled fed inﬁnite phased array of rectangular patches  and ﬁnite phased array of stacked circular patches  has also been analyzed. In  in order to evaluate the characteristics of aperture coupled microstripantennas in a ﬁnite array and derive the moment-method solutions for the unknown current distributions on the patches and slots, the reciprocity theorem and the spectral domain Green’s functions for a dielectric slab are used. But this work is pertained to a stacked microstrippatch and neither Green’s functions nor results are suitable for a single layer structure. Furthermore, no comparison is made between rectangular and circular patches in a ﬁnite array environment. To the knowledge of the authors no full wave analysis of the aperture coupled ﬁnite phased array of rectangular or circularpatchantennas is in evidence. It is well known that the inﬁnite array approximation, models the central element of a large but ﬁnite array quite well but it is diﬃcult to predict the behavior of the antenna elements positioned near the edges.
There are many advantages of microstripantennas such as conformal planar shape. There are extensive quantity of papers within the literature which deals with microstripantennas. Despite the fact that individual microstrippatch antenna has numerous benefits, it additionally has a few drawbacks, for instance, less gain, narrow bandwidth with low efficiency. These impediments can be overwhelmed by developing an array configuration. The ground plane with slot to reduce the size of microstrip antenna was proposed in 1 . To obtain the multiband operation planar inverted-L antenna was proposed in 2 .The methods to obtain the circularly polarized multiband microstrip antenna was proposed in 3. The advantage of circularly polarized antenna over the linear polarized one is that the orientation of the device on which the antenna is installed does not affect the received power. Antenna array for multiple input and multiple output application was discussed in 4 . The advantages, disadvantages and applications of microstripantennas were discussed in 5 .
With the fast expansion of present Wireless Communication Technology, microstripantennas are attracting many researchers . Though printed Microstripantennas are having advantages of simple geometry, ease of manufacture and little expensive, they suffer from drawbacks of narrow bandwidth and low gain . X band is used in radar applications like single polarization, dual polarization, synthetic aperture radar and phased arrays and X band radar frequency sub-bands are used in civil, military, and government organizations for weather monitoring , air traffic control, maritime vessel traffic control, defense tracking and vehicle speed revealing for law enforcement. Many techniques are there in the literature to provide X band microstripantennas which include bow tie antenna , using circularpatch , using nine element quasi yagi antenna , using dielectric resonator , having two slots on the ground plane , using fractal patterned iris loaded cross dipole slot  and having two dielectric resonators coupled to an S-shaped slot , Single Band-Notched UWB Square Monopole Antenna with Double U-slot and Key Shaped Slot.
The ISM radio band were for the use of radio frequency (RF) energy for industrial, scientific and medical purposes. The application in these bands such as Bluetooth and WLAN (wireless LAN) at 2.4GHz. The development of wireless communication system has been rapidly growth in this era with increasing demand in the level of enhancement and performance. A good antenna has high gain, small physical size, broad bandwidth and versatility. A microstrippatch antenna is one of the antennas that have the advantages such as light weight, small size, and low in cost, conformability and possibility of integration with active devices. The microstrip
The application of this type of antennas started in early 1970’s when conformal antennas were required for missiles. Rectangular and circular micro strip resonant patches have been used extensively in a variety of array configurations. A major contributing factor for recent advances of microstripantennas is the current revolution in electronic circuit miniaturization brought about by developments in large scale integration. As conventional antennas are often bulky and costly part of an electronic system, micro strip antennas based on photolithographic technology are seen as an engineering breakthrough.
This work is an effort to buildup on the works proposed in literature [6-15]. This paper presents the results of optimization and analysis of four different dielectric substrate circularmicrostrip antenna with circular polarization capability. Optimizations have been performed to get maximum gain and axial ratio bandwidth for the four different materials viz. Taconic TCL, FR-4, Bakelite, Rogers RT/Duroid 6006. The design frequency of 5.9GHz has been chosen to be used in all the designs. Simulation software High Frequency Structure Simulator (HFSS)  is used to design, simulate and optimize the proposed antennas.
The purpose of this work is to design a microstrippatch antenna using viable simulation software. IE3D, from zeland software,Inc., is an electromagnetic simulation and optimization software useful for circuit and antenna design. IE3D has a menu driven graphic interface for model generation, and uses a field solver based on full wave, method-of-moments to solve current distribution on 3D and multi-layer structures of general shape.
In this work, a precise and effective approach is applied to calculate important parameters of circularpatch an- tenna. Microstrippatchantennas of all shapes are widely used in communication systems where their small size, conformal geometry and low cost can be used to advan- tage. Due to the recent availability of low loss, commer- cial microwave ferrites there is an increasing interest in the performance of the patchantennas printed on ferrite substrates. Although some work [1-6] have been per- formed for microstrip antenna with GA approach for the patchantennas without magnetic biasing but analysis of almost all important parameters for ferrite substrate under magnetic biasing for circularpatch antenna is new one. Present analysis also incorporate the dispersion effects due to magnetic field biasing in the form of effective propagation constant (k) which is not discussed in the referenced articles. Some similar referenced works [7-11] also have done mathematically or by conventional me- thods for optimization but this technique is rather precise, accurate and sensitive to optimize parameters of patch antenna as well as other type of antenna also.
The reflector array antenna which is considered as a receiving antenna and the transmitting antenna is taken as a microstrippatch antenna, circularpatch antenna, patch antenna and patch antenna with a coaxial feed is designed, simulated and compared. After comparison of all these antennas, microstrippatch antenna shows the better performance in terms of return loss, gain and radiation pattern at a frequency of 79GHz.
Microstrippatch directional antennas have been used in many applications  - , because of their low profile, conformability, light weight, easy connectivity (feed), cheap realization and attractive radiation characteristics. A microstrippatch antenna is a wide-beam, narrowband antenna which is created by etching the antenna element (patch) in a metal trace material bonded to an isolating dielectric substrate . Most physical realizations feature a Printed Circuit Board (PCB), with a continuous metal layer attached to the opposite side of the substrate which creates a ground plain. Common microstrip antenna shapes are square, rectangular, circular, elliptical, but any continuous shape is possible. The Fig.2 shows the mechanical drawing of a rectangular patch antenna.
ABSTRACT: In this paper a circularmicrostrippatch antenna with embedded circular slots to obtain harmonic suppression and peripheral cuts for producing circular polarization (CP) is proposed and analyzed. Antenna is designed by taking into consideration the use of Active Integrated Antennas  and rectifying antennas (rectenna) . Low cost FR4 epoxy is used as the substrate and 2.45GHz/802.11a as the design frequency. Simulated 10dB return loss bandwidth of 171MHz and CP 3dB axial ratio bandwidth of 46MHz is obtained. Size reduction of 4% is also obtained as compared to the conventional circularpatch antenna with linear polarization (LP). Simulations and optimizations are performed by using High Frequency Structure Simulator (HFSS) software.
An explosive growth of the wireless radio frequency identification market such as electronic toll collection and more generally wireless road-to-vehicle communica- tion systems is currently observed in the microwave band. In the short range communications or contactless identi- fication systems, antennas are key components, which must be small, low profile, and with minimal processing costs [1,2]. The microstrippatchantennas are of great interest for aforementioned mentioned applications due to their thin and compact structures. The flexibility af- forded by microstrip antenna technology has led to a wide variety of design and techniques. The main limita- tions of the microstripantennas are low efficiency and narrow impedance bandwidth. The bandwidth of the mi- crostrip antenna can be increased using various tech- niques such as by loading a patch, by using a thicker substrate, by reducing the dielectric constant, by using gap-coupled multi-resonator etc [3–5]. However, using a thicker substrate causes generation of spurious radiation and there are some practical problems in decreasing the dielectric constant. The spurious radiation degrades the antenna parameters. Among various antenna bandwidth enhancement configurations, the two gap-coupled circu- lar microstrippatch antenna is most elegant one. So,
Patchantennas are based on printed circuit technology to create flat radiating structures on top of a ground-plane-backed substrate. The advantage of such structures is the ability of building compact antennas with low manufacturing cost and high reliability. However, it is in practice difficult to accomplish this while at the same time achieving high bandwidth and efficiency. Nevertheless, improvements in the properties of the dielectric materials and in design techniques have led to enormous growth in the popularity of microstrippatchantennas, and there are now a large number of commercial applications. Many shapes of patches are possible, with varying applications, but the most popular are rectangular, circular and thin strips .
In this technique bandwidth enhancement is done by changing/modifying the shape of radiating patch. It is found that some shapes of patches have lower Q factor as compared to other therefore having high bandwidth . These patches shapes include annular ring, rectangular/square ring, shorted patch and other geometries. There are several designs of broadband microstrippatch antenna with modified patches. A design of broadband circularpatchmicrostrip antenna with Diamond shape slot is given by Garima, et al. . In this paper a circularpatchmicrostrip antenna having a concentric diamond shape slot is presented. Its configuration is shown in figure (1).
Abstract—In this paper, three different compact circular-ring microstrippatch antenna structures have been proposed. These antennas have been analyzed, investigated and optimized using the CST- MW-simulator. The proposed designs are mainly based on the concept of patch shape reconfiguration while its overall dimensions are kept constant. The objective is to design dual and/or triple broadband antennas resonate within the fourth generation band (4G). The presented antennas are simulated and fabricated on cheaper and lossy FR-4 substrate, and their parameters are measured and compared. The obtained results show that the proposed antenna structures resonate within the 4G frequency band. The operating bandwidths have been varied between 270.0 MHz and 1000.0 MHz (about 4% up to 7% of center frequency). In addition, maximum VSWR value of less than 1.5 has been achieved. The obtained results verify the validity and the benefits of reconfiguring the patch shape. Finally, good agreement has been obtained between simulated and measured parameters.
In this paper, a set of new hybrid antennas including a semi-circular SIW cavity and microstrippatch providing wide impedance bandwidth is proposed. Different shaped patch including rectangular, semi-circlular and equilateral triangular are investigated numerically and experimentally. All proposed hybrid antennas are excited by an inset 50 W microstrip line, which facilitate integration with planar circuits and directly connection to a SMA connector. Also, they are implemented only on a single substrate using low cost PCB process. It is shown that placing a mircrostrip patch at an appropriate distance along the dielectric aperture of an HMSIW cavity-backed antenna, enhances antenna bandwidth and gain effectively. These hybrid antennas have been numerically investigated and results indicated fractional impedance bandwidth wider than 6% and gain higher than 7 dB. The best type of the proposed hybrid antennas, rectangular patch hybrid antenna which providing maximum impedance bandwidth is fabricated. The measured fractional impednace bandwidth of 10% with 7.5 dBi gain for is also obtained.
The design of Microstripantennas with circular polarization and wide bandwidth axial ratio is complex in most cases, in this sense, a circularpatch design with circular polarization and reconfigurable sense of rotation is presented in  achieving 27.39% impedance bandwidth for a reflection coefficient magnitude 𝑆11 < −10𝑑𝐵 in the range from 2.295 𝐺𝐻𝑧 to 3.025 𝐺𝐻𝑧 , a maximum gain of 6.04 𝑑𝐵𝑖 and a 13% axial ratio bandwidth for -3dB reference. Moreover, a design with circular ring geometry short-circuited and reconfigurable sense of rotation is presented in  where a 33.33% impedance bandwidth in 1.9𝐺𝐻𝑧 - 2.66𝐺𝐻𝑧 frequency range for a reflection coefficient less than -10 dB was achieved, a
Abstract: In recent advances there have been a growing demand for ultra wide technology. One of the most promising areas in UWB applications is Wireless Body Area Network (WBANs). Flexible fabric antennas are best suited in WBANs, which can be easily attached to a piece of clothing. For flexible antennas, textile materials form interesting substrates, because fabric antennas can be easily integrated into cloths. Textile materials generally have a very low dielectric constant, which reduces the surface wave losses and improves the impedance bandwidth of the antenna. If the antenna is made of textile material they will not make any harm to human body and will be totally wearable. This paper presents the design a flexible fabric textile antenna for (WBANs) operating in the frequency band of 2.39GHz to 2.5 GHz. The antenna consists in a simple metallic circular ring with slots in between. The performance investigation of circular ring microstrippatch antenna on three different dielectric substrates of same thickness or height (0.3mm).All these antennas are having different feeding port placement. The three dielectric materials which are investigated are cotton, cordura, 100%polyester. The output parameters of all these antennas are simulated using IE3D software. Among the three metallic circular ring antenna, antenna with cotton as a dielectric substrate gives optimum results in terms of Directivity, Gain, Bandwidth and Efficiency.
Circularly polarized (CP) antennas have been receiving much attention due to their abilities to eliminate the arising multipath effects and allow flexible orientation of the transmitter and the receiver. As far as single-fed microstripantennas are concerned, circular polarization can be generated with perturbation technologies such as using a nearly square patch , truncating patch corners , adding stubs or cutting notches along two opposite edges  and embedding a diagonal slot . However, the simple single-fed CP antennas have inherently narrow 3- dB axial-ratio (AR) bandwidth of less than 2% .