Microstripantennas  are becoming increasingly useful because they can be printed directly onto a circuit board. These antennas are also becoming very pervasive within the mobile phone market. Microstripantennas are low cost, low profile & simply fabricated. These are relatively cheap to manufacture & design because of the simple 2-dimensional physical geometry. These are also less weight, conformal shaped, capable of dual & triple frequency operations. These are extremely efficient, easily integrated to circuits, easy to planer & non- planer surfaces and are compatible with MMIC design. All these features make patchantennas widely implemented in many applications, such as high performance aircrafts, wireless communication, satellite and missile applications. However microstripantennas have disadvantages also, narrow bandwidth being a serious limitation. Different techniques are projected to improve it, and one of the methods proposed by various researchers is by cutting slots on it. In this paper we have designed a MicrostripPatch antenna using proposed by various researchers is by cutting slots on it. In this paper we have designed a MicrostripPatch antenna using circular and square slots on the rectangular microstrip antenna.
applications is the next topic in this paper. These antennas usually have multiple ports with the same angular and phase differences between them. Therefore, considering the active 𝑆-parameters and the realised gain is necessary for these antennas. In fact, the original antennas such as quadrifilar helical antennas (QHAs) and conical QHAs have proven in the past to be reliable. However, the issue is more important when the antennas are miniaturised, since the coupling between the ports is increased, such as for the QHAs with meandered or folded arms, the conical QHAs with folded arms, etc. [12-20]. In this paper, two structures are re-examined; multi-fed spiral antennas with folded arms [21, 22] in section 3 and quadrifilar square helical antennas (QSHAs) with folded arms  in section 4. It is indicated that the situation is better for these antennas compared with the U-slotted microstrippatch, since the differences between the gain and the realised gain are very less at the operating frequencies. However, the realised gains of the QSHAs at 145 MHz are reduced significantly due to the fundamental limitations for the gain of an antenna.
This paper described the design of square spiral shaped patchantennas operable over a wide frequency range or at multi-frequencies by incorporating suitable tuning elements. Ansoft HFSS software is used for analytical modelling and simulation. A good impedance matching is observed near the frequencies 1.6 GHz, 2 GHz, and 2.4 GHz using two symmetrical tuning elements as shown in Fig. 3 for the multifrequency operation of mobile hand set. The same antenna with four symmetrical tuning elements (Fig.5) can be used for broad band communication over a band width of 25.6%.
Dual-polarized resonant cavity antennas for dual-band operation have been reported in the literature by using double  or single layer  PRS. Similarly, wideband dual-polarized resonant cavity antennas have also been reported with diﬀerent PRS structures. In , wideband dual-polarized RCA was reported for 5G wireless local networks (WLANs) application. The feed antenna consisted of two orthogonal bow-tie dipoles over ground plane. The measured bandwidth was 5.3–6.3 GHz (17.2%). The gain of the antenna was 12.1 dBi at 5.5 GHz. In , a broadband resonant cavity antenna operating at Ka band with high gain and dual-polarization was reported. A double-sided complementary-circular patch PRS was used in the above mentioned antenna to enhance the directivity and radiation bandwidth. Further, a squarepatch coupled with two orthogonal slots and fed by two microstrip lines was also applied as the primary feed to achieve dual-polarization operation. The impedance bandwidth of the
Abstract—In this paper, a metamaterial loaded square-shaped fractal antenna with two iterations is presented and discussed. A metamaterial loading consists of split ring resonators (SRRs) which enhances the bandwidth of the antenna keeping the dimensions and size of the antenna same. The square-shaped fractal antenna, which is in the form of three concentric rings, was simulated and fabricated, and the results were shown and discussed. The antenna resonates at three distinct frequency bands 4.3719 GHz, 7.7437 GHz and 10.6374 GHz with the gains of 1.1974 dB, 4.2745 dB and 4.7233 dB, respectively for resonant frequencies. The bandwidths for the antenna are 185 MHz, 198 MHz and 386 MHz for distinct resonant frequencies. The antenna is fabricated using an FR-4 substrate, and the measured resonant frequencies are 4.08 GHz, 7.545 GHz and 10.24 GHz. In metamaterial loading condition, the antenna resonates at 4.0105 GHz, 6.8474 GHz and 8.0632 GHz with bandwidths of 636 MHz, 347 MHz and 1.33 GHz at resonant frequencies. The appreciable bandwidth is achieved in such a small antenna without changing dimensions and size of the antenna. The simulated, experimental results and comparison are also presented in this paper. The results show that the proposed method can be used to design high bandwidth and compact fractal microstrippatchantennas without increasing dimensions.
At the same time, MPAs need to be extremely small and compact to satisfy the severe size constraints of some critical applications such as mobile cellular handsets, card less phones and blue tooth devices.The miniaturization of normal MPA size (i)has typically been accomplished by loading ;which can take various forms, such as (i)using a high permittivity substrates ,(ii)Using shorting ports or shorting pins ,or (iii)modifying the basic patch shape.
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.
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 circular patchmicrostrip antenna with Diamond shape slot is given by Garima, et al. . In this paper a circular patchmicrostrip antenna having a concentric diamond shape slot is presented. Its configuration is shown in figure (1).
Fractals mean asymmetrical fragments. Fractals describe a composite set of geometries ranging from self similar/ self-affine to other irregular structure. Fractals are generally composed of various copies of themselves at different scales and hence do not have a predefined size, which makes their use in antenna design very capable. Fractal antenna engineering is an issuing field that employs fractal concepts for developing new types of antennas with prominent characteristics. Fractal shaped antennas show some attractive features which results from their geometrical properties . The inimitable features of fractals such as self-similarity and space filling properties enable the realization of antennas with interesting feature such as multi-band operation and miniaturization. A self-sowed set is one that consists of scaled down copies of itself. This property of self-similarity of the irregular fragment geometry  aids in the design of fractal antennas with multiband feature. The self-sown current distribution on these antennas is expected to cause its multiband characteristics. The space-filling characteristics of fractals tend to fill the area occupied by the antenna as the order of iteration is increased. Higher order fractal antennas feat the space-filling property and enable miniaturization of antennas. Fractal antennas and arrays also display lower side-lobe levels. Fractals have been applied successfully for miniaturization and multi-band operations of simple antennas generally dipole, loops and patchantennas. It has been observed that such as approach result in decrease of the input impedance bandwidth .
With the rapid development of wireless communication systems, circularly polarized (CP) antennas have gained much attention than ever. It is because they not only are capable of allowing for better mobility and weather penetration, but also alleviate multipath distortion and polarization mismatch losses between the receiving and transmitting antennas. In recent years, many microstrip CP antennas of the single-fed type are reported in the literature, such as a corner-truncated squarepatch with a novel coaxial feed , wideband CP microstripantennas with annular-ring slot or cross-shaped slot [2– 4], stacked CP microstripantennas using a new C-type single feed or a S-shaped impedance matching network [5–7], and a broadband microstrip antenna using an artificial ground structure with rectangular unit cells . However, these CP antennas have relatively narrow impedance and AR bandwidths (generally less than 10%). For microstripantennas of the dual-fed or tri-fed type [9–11], circular polarization can be generated with the use of an external polarizer, resulting in wide impedance and AR bandwidths. A circular patch antenna, employing four sequentially rotated L-probes and a novel wideband 90 ◦ hybrid feed network, delivers 10-dB impedance and 3-dB AR bandwidths of 79% and 82%,
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 squarepatch , 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% .
By the passage of time, microstripantennas became one of the rapid growing segments in the industry of telecommunication and believed to be the vital and preferred medium for the future. These days, this type of antenna has a large demand by the end user and consumer for integrated wireless digital application. Antenna that will be used in this application such as WiMAX should be low profile, low weight, low volume and broad bandwidth. 
Feed point Location of an Inset Fed Rectangular Patch (x o , y o , w f , L f ). There are different methods of feeding a patch antenna like: probe feed, microstrip line feed, aperture coupled feed and proximity coupling feed. But of all, microstrip line feed and the coaxial probe feed are commonly used because of their simplicity. Microstrip inset feed method was used in this design for proper input impedance matching  and the line parameters were designed using a standard input impedance of 50Ω. Feed point location where input impedance is approximately 50Ω can be calculated using [3, 4]. (0.61 )]} (10)
The design method that proved very effective while producing the previous broadband antenna, also proved useful when producing the triangular broadband antenna. Initially the narrowband triangular patch was made using the copper tape and tuned to match the input impedance. The initial construction led to the patch resonating at a frequency higher than 2.45 GHz. numerous attempts were required before the correct dimensions were achieved which allowed the patch to resonate at 2.43 GHz. It was deliberately tuned for 2.43 GHz keeping in mind the frequency shift that will occur from adding parasitic elements. Input impedance was found to be very large at the vertex along the feed axis. The 50-ohm impedance matching can be obtained by feeding the antenna at either above or below the null position at the centre of the patch. The optimum feed coordinates were found to be Y f =
Microstrippatchantennas are light weight and low proﬁle antennas that are inherently narrowband in the order of 1%–2% . In emerging wireless communications and radar systems, however, large bandwidths are necessary to transmit massive amounts of data and to enhance the resolution in radar systems. Hyung and Lee  proposed a novel technique to increase the bandwidth of single-layer patchantennas to 30% by cutting a U-shaped slot from the patch. The U-slot antenna has been further studied and analyzed to develop design procedures [3, 4] to estimate the structure’s multiple resonating frequencies that are eventually coupled together to widen the frequency band. Recent advances in the ﬁeld of wearable technology have created a strong demand for antennas that are ﬂexible and mechanically robust for long-time use. The bending eﬀects on the rectangular patch antenna were studied for wearable applications in [5–11]. A cylindrical-rectangular cavity model for bent patchantennas was analyzed in [10, 11]. In [5, 6], the bending eﬀects of narrow- and multi-band patchantennas on the input impedance, resonant frequencies, and radiation performance were studied, where the shift in the resonant frequencies was well explicated. However, the bending eﬀect on the impedance bandwidth of wideband antennas has not been investigated, to the best of our knowledge.
The presented study introduces a new concept of reconfigurable antenna patch where the outer patch dimensions are kept constant. Using this concept, the patch resonance frequencies can be controlled and adjusted to the desired band. Three new compact circular microstrip antenna configurations have been proposed to verify the concept of patch reconfiguration. The proposed antennas have been designed, analyzed, and simulated using CST Microwave Studio simulator. The three proposed antennas have been fabricated on FR-4 substrate and their parameters have been measured. Good agreement has been obtained between the simulated and the measured values. The proposed antenna configurations have achieved enhanced parameters as compared to the current 4G antennas. The gain is improved by 20% and the radiation efficiency is enhanced by 10%. The operating bandwidth has been widened several of hundreds of megahertz (270–1000). Finally, the presented antenna configurations achieve perfect VSWR (1.1–1.5).
patch for phi=70 degree & theta= 30 degree; port 1 (in x- axis) is 90 degree offset from port 2, generating LHCP. The antenna simulated, works as a linearly polarized antenna, when only one port, either port 1 or 2, is acting as source & the other is idle. Hence, it is a single antenna, containing simple design geometry, which performs as a linearly polarized antenna, when either of the port is on or both ports are on without 90 degree phase shift between them. For circular polarization, 90 degree phase shift has been provided between the two ports with same amplitude, with square slotting in patch for proper impedance matching, making it an easy to fabricate, polarization reconfigurable antenna.
They were connected to the ground plane by two small rectangular slots which are shown in Figure 1(d). On the other hand, Figures 1(f) to (i) represent the evolution of patch from ring to proposed shape. A square and discrete small ring slots are added to create some extra resonant frequencies inside the antenna bandwidth to support our ultra-bandwidth specification. The antenna will resonate on 6.8 GHz caused by squarepatch using Eq. (5):
Consider a probe located at the center of a circular patch antenna with radius of R as shown in Fig. 1. Perfect electric/magnetic conductor (PEC/PMC) as well as the non-reflective perfectly matched layer (PML) boundary conditions are used at the outer boundary ρ = R. Various boundaries here are beneficial for the validation of the circuit model derived although only PMC boundary is a useful approximation for a patch antenna analysis. The inner and outer radii of the probe are denoted as a and b, respectively. The probe height or the separation of two plates is h. Between two plates is a dielectric material with a relative permittivity of ε r . Note that a probe in an infinite plate
In H-plane coupling when two microstripantennas having the same patch width ‘a’ and the same length ‘b’ (incase of E-plane coupling length may be diﬀerent) is brought closer keeping the distance ‘d’ between the two edges less then 0.2λ, the resonant frequency of the antenna diﬀers from the design frequency. The shift is also pronounced if the distance ‘d’ is more than 0.2λ due to the presence of the fringing ﬁeld of the isolated element.