Miniaturized Circularly Polarized Stacked Patch Antenna on Reactive Impedance Surface for Dual- Band ISM and Wi. MAX Applications.
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Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 1. School of Electrical and Electronic Engineering, Nanyang Technological University, 5. Nanyang Avenue, Singapore 6. Copyright . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper proposes a compact microstrip patch antenna for operating in 2. The CP radiation in dual- bands is a result of two multilayered truncated corner stacked square patches, while the reactive impedance surface (RIS) is used for antenna size miniaturization for the lower operating frequency band.
Since the overall lateral antenna dimensions are controlled by the lower frequency band (higher wavelength), reducing the electrical size of the antenna for lower band results in overall smaller antenna dimensions. The measured 3- d.
SUN et al.: DUAL-BAND CIRCULARLY POLARIZED STACKED ANNULAR-RING PATCH ANTENNA FOR GPS APPLICATION 51 Fig. Simulation results of frequency ratio with the changing of. Photograph of the fabricated antenna. RADIOENGINEERING, VOL. 1, APRIL 2014 195 Dual Band Circularly Polarized Modified Rectangular Patch Antenna for Wireless Communication Vijay SHARMA1, M. Shaped Circularly Polarized patch antenna with small fre-quency ratio for GPs application.Asymmetrical S-shaped slot. Design and Performance Analysis of Dual band Circularly Polarized C-Slot Patch Antenna Author. Design of Stacked Microstrip Dual-band Circular. RANI, DESIGN OF STACKED MICROSTRIP DUAL-BAND. Circularly Polarized Dual Frequency Patch Antenna for TTC applications M. Samsuzzaman Faculty of Engineering and Built. X shape microstrip patch antenna for Ku/K band applications,' Modern Applied Science, vol. Miniaturized Circularly Polarized Stacked Patch Antenna on Reactive Impedance Surface for Dual-Band ISM and WiMAX Applications.
A coplanar waveguide fed dual-band circularly polarized rectangular slot antenna. Misran, “Circularly polarized S band dual frequency square patch antenna using glass microfiber reinforced PTFE composite. Circularly Polarized Slotted/Slit-Microstrip Patch Antennas. The circularly polarized reader antenna is useful in particular when tag antenna.
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B axial ratio bandwidths of the in- house fabricated antenna prototype are 6. The maximum gain at boresight for the lower band is 2. The overall volume of the proposed antenna is 0. Introduction. Compact circularly polarized microstrip antennas (CPMAs) are useful for portable handheld devices because of their insensitivity to the change in polarization caused by the transmitting and receiving antenna orientations, as well as ionospheric rotation. For handheld and portable wireless communication devices, the antenna. That is the reason why some commercial receivers use linearly polarized (LP) antennas to receive circularly polarized signals.
LP antennas are smaller in size than the corresponding circularly polarized (CP) antenna . The problem is exacerbated when the antennas are supposed to radiate in two or more bands.
There are many CPMAs proposed in the literature . Generally, a single feed microstrip patch antenna generates a linearly polarized wave, unless some perturbation is introduced in the antenna patch to excite two orthogonal modes for CP radiation. This is usually achieved by making slots or slits . Since then, the introduction of artificial magnetic conductors (AMCs) has opened a new perspective to design smaller and more efficient microstrip antennas . AMCs are also called high impedance surfaces (HISs), and from now these two terms will be used interchangeably in this paper. A modification of the AMC was suggested in .
These electromagnetic metasurfaces find application in enhancing the radiation properties of the antennas like operating frequency bandwidth, direction of antenna radiation, and size miniaturization. Both AMCs and RISs comprise periodic structures of different shapes and sizes . The difference between the two is in their operating frequency. In a perfect electrical conductor (PEC), the image of an electric current parallel to the surface is always out of phase by 1. But in a metasurface the phase difference between the current and its image (the reflection phase) varies from 1. At one particular frequency, the reflection phase is zero, and the image current is in the same phase as that of the physical current above it. At this frequency, the metasurface is AMC or HIS.
When the reflection phase is 1. At all other frequencies, the surface has reactive impedance and is called a reactive impedance surface. Because of the difference in electrical properties, HISs and RISs have different applications when it comes to antenna design. HIS is more suitable for use as a reflector for antennas that have a bidirectional radiation pattern, where it limits antenna radiation in a particular direction. HISs are more effective than the conventional PEC reflectors because they can be brought really close to the radiating structure (separation as small as 0. Some monopole/dipole antennas have also been designed on HIS ground plane, thus resulting in low- profile antenna structures.
On the other hand, RIS is a good substitute for the traditional high- dielectric substrate used for the size reduction. The inductive reactance of the RIS cancels the near- field capacitance of the microstrip antenna, resulting in a broader bandwidth and a compact size . Besides these two general uses, there are metasurface based antennas that do not fall into these categories.
Metasurfaces have been used to enhance the properties of both planar and nonplanar antennas. Both these works involve a nonisotropic metasurface, and the reflection phases are +9. That was achieved using periodic rectangular patches for designing the metasurface. Cross- dipole antennas over AMCs were studied in . In both cases, the axial ratio performance of the intrinsically CP cross- dipole antenna is improved by the presence of the AMC surface.
An on- chip CP antenna for use in the 6. GHz Wi- Fi Band was presented in . A CP antenna over a nonuniform HIS was presented in . If designed properly, slot antennas radiate CP waves efficiently but are bidirectional in nature. To make them unidirectional, a reflector has to be used. A PEC reflector has to be kept at a minimum separation of 0.
This makes the antenna profile thick. The problem can be solved by using AMC reflector that can be brought very close to the radiating structure. The image current generated by the reflecting surface is now in phase with the antenna current for the optimized frequencies of operation.
Hence the two do not cancel each other and the reflector can be brought very close to the main antenna, resulting in a low- profile antenna structure. This has been investigated in . It does this by spatially distributing the image current so that there is minimum mutual coupling between the antenna current and its image. It also stores the magnetic energy that compensates for the near- field electric energy of the radiating structure .
It has been shown that the use of RIS substrate can result in the increase of both impedance bandwidth and the AR bandwidth for CP antennas. The use of RIS for reducing the patch size of single- layer microstrip antennas has been proposed in . This results in the RIS becoming even more optimized for CP radiation, with more AR bandwidth than a conventional RIS.
The CP radiation in dual- bands (2. The RIS is used in the inductive region for decreasing the resonance frequency for the lower band and improving the antenna radiation performance.
The compact CP patch antenna loaded with RIS is designed, fabricated, and tested. Commercially available electromagnetic (EM) solver CST Microwave Studio (MWS) . This paper is divided into four sections following this introduction. Section 2 explains in detail the concept of artificial impedance surface (AIS), AMC, and RIS.
Section 3 describes the design of the metasurface and the patch radiators and how both interact with each other. The simulated and measured results are discussed in Section 4. Section 5 concludes this paper by summarizing all the results obtained.
AIS, AMC, and RISThe difference between RIS and AMC is their frequency of operation. To avoid confusion, the structure is called AIS in general. AIS can be modelled as a circuit comprising an inductance and capacitance in parallel.
When the circuit is at the resonant frequency, it is AMC. At other frequencies, the net impedance is either inductive or capacitive and hence it is called RIS. The terms HIS and AMC can be used interchangeably.
This is because two things can be observed at the resonance frequency. First of all, the resonant condition of a parallel LC circuit leads to a very high impedance (which is theoretically infinity). And, secondly, the magnetic field tangential to the surface is zero (shown in Figure 1(b)). This is analogous to an electric conductor which has a zero tangential electric field (shown in Figure 1(a)). That is why these surfaces are called magnetic conductors. As they are not found in nature and are created artificially, the name given to them is artificial magnetic conductor (AMC). Figure 1: Comparison of electric field and magnetic field in (a) electric conductor and (b) magnetic conductor.
The difference in properties between AMC and RIS is the result of difference in their reflection phase. In AMC, a charge and its image have the same phase. Hence a horizontal current over AMC has the same orientation as its image current (it is opposite for a vertical current). This is in contrast with an electric conductor, which has the image out of phase from the main charge by 1.
For RIS working in the inductive mode, the reflection phase is between 1. For a normal incident wave, the reflection phase of a surface with impedance is given bywhere is the intrinsic impedance of free- space . The exact mathematical model is given in . This causes the image current amplitude to vary with frequency so that at a certain frequency the image current has minimum amplitude as shown in Figure 3.
Also, the normalized impedance can be chosen such that the stored energy in the image source compensates for the energy stored by the source itself; that is, if the antenna shows a capacitive loading and its image stores the magnetic energy, resonance can be achieved at much lower frequency than the resonance in free- space by proper integration with an inductive RIS. Figure 2: Image distribution of an infinitesimal dipole over a surface with impedance . Also, AIS is AMC at a single specific frequency, while it exhibits inductive behaviour over a wide range of frequencies.
Proposed Antenna Geometry and Design. The complete view and the cross- sectional view of the proposed antenna over RIS structure are shown in Figures 4(a) and 4(b), respectively. The antenna comprises two stacked truncated corner square patches (TCSP) placed on RIS substrate. The upper patch has a side length while the lower one has a side length .
The antenna is fed by 5.