Microstrip Patch Antennas (or simply patch antenna) are increasingly useful because the antenna is printed directly onto a circuit board. Additional benefits of patch antennas is that they are easily fabricated making them cost effective. Design, optimization and development of X-band microstrip patch antenna array for high gain, low sidelobes and impedance matching Abstract: The objective was to design and fabricate a four element X-band microstrip array centered at 7.5 GHz which has high gain, low sidelobe levels and is simultaneously well matched to the source.
A microstrip antenna array for a satellite television receiver.
Diagram of the feed structure of a microstrip antenna array.
In telecommunication, a microstrip antenna (also known as a printed antenna) usually means an antenna fabricated using microstrip techniques on a printed circuit board (PCB).[1] It is a kind of internal antenna. They are mostly used at microwavefrequencies. An individual microstrip antenna consists of a patch of metal foil of various shapes (a patch antenna) on the surface of a PCB (printed circuit board), with a metal foil ground plane on the other side of the board. Most microstrip antennas consist of multiple patches in a two-dimensional array. The antenna is usually connected to the transmitter or receiver through foil microstriptransmission lines. The radio frequency current is applied (or in receiving antennas the received signal is produced) between the antenna and ground plane. Microstrip antennas have become very popular in recent decades due to their thin planar profile which can be incorporated into the surfaces of consumer products, aircraft and missiles; their ease of fabrication using printed circuit techniques; the ease of integrating the antenna on the same board with the rest of the circuit, and the possibility of adding active devices such as microwave integrated circuits to the antenna itself to make active antennas.
Patch antenna[edit]
The most common type of microstrip antenna is the patch antenna. Antennas using patches as constitutive elements in an array are also possible. A patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate, such as a printed circuit board, with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. Common microstrip antenna shapes are square, rectangular, circular and elliptical, but any continuous shape is possible. Some patch antennas do not use a dielectric substrate and instead are made of a metal patch mounted above a ground plane using dielectric spacers; the resulting structure is less rugged but has a wider bandwidth. Because such antennas have a very low profile, are mechanically rugged and can be shaped to conform to the curving skin of a vehicle, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices.
Advantages[edit]
Microstrip antennas are relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry. They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency. A single patch antenna provides a maximum directive gain of around 6-9 dBi. It is relatively easy to print an array of patches on a single (large) substrate using lithographic techniques. Patch arrays can provide much higher gains than a single patch at little additional cost; matching and phase adjustment can be performed with printed microstrip feed structures, again in the same operations that form the radiating patches. The ability to create high gain arrays in a low-profile antenna is one reason that patch arrays are common on airplanes and in other military applications.
Such an array of patch antennas is an easy way to make a phased array of antennas with dynamic beamforming ability.[2]
An advantage inherent to patch antennas is the ability to have polarization diversity. Patch antennas can easily be designed to have vertical, horizontal, right hand circular (RHCP) or left hand circular (LHCP) polarizations, using multiple feed points, or a single feedpoint with asymmetric patch structures.[3] This unique property allows patch antennas to be used in many types of communications links that may have varied requirements.
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Rectangular patch[edit]
The most commonly employed microstrip antenna is a rectangular patch which looks like a truncated microstrip transmission line. It is approximately of one-half wavelength long. When air is used as the dielectric substrate, the length of the rectangular microstrip antenna is approximately one-half of a free-space wavelength. As the antenna is loaded with a dielectric as its substrate, the length of the antenna decreases as the relative dielectric constant of the substrate increases. The resonant length of the antenna is slightly shorter because of the extended electric 'fringing fields' which increase the electrical length of the antenna slightly. An early model of the microstrip antenna is a section of microstrip transmission line with equivalent loads on either end to represent the radiation loss.
![]() Specifications[edit]
The dielectric loading of a microstrip antenna affects both its radiation pattern and impedance bandwidth. As the dielectric constant of the substrate increases, the antenna bandwidth decreases which increases the Q factor of the antenna and therefore decreases the impedance bandwidth. This relationship did not immediately follow when using the transmission line model of the antenna, but is apparent when using the cavity model which was introduced in the late 1970s by Lo et al.[4] The radiation from a rectangular microstrip antenna may be understood as a pair of equivalent slots. These slots act as an array and have the highest directivity when the antenna has an air dielectric and decreases as the antenna is loaded by material with increasing relative dielectric constant.
The half-wave rectangular microstrip antenna has a virtual shorting plane along its center. This may be replaced with a physical shorting plane to create a quarter-wavelength microstrip antenna. This is sometimes called a half-patch. The antenna only has a single radiation edge (equivalent slot) which lowers the directivity/gain of the antenna. The impedance bandwidth is slightly lower than a half-wavelength full patch as the coupling between radiating edges has been eliminated.
![]() Other types[edit]
Another type of patch antenna is the planar inverted-F antenna (PIFA).The PIFA is common in cellular phones (mobile phones) with built-in antennas.[5][6]The antenna is resonant at a quarter-wavelength (thus reducing the required space needed on the phone), and also typically has good SAR properties.This antenna resembles an inverted F, which explains the PIFA name. The PIFA is popular because it has a low profile and an omnidirectional pattern.[7]These antennas are derived from a quarter-wave half-patch antenna. The shorting plane of the half-patch is reduced in length which decreases the resonance frequency.[8]Often PIFA antennas have multiple branches to resonate at the various cellular bands. On some phones, grounded parasitic elements are used to enhance the radiation bandwidth characteristics.
The folded inverted conformal antenna (FICA)[9] has some advantages with respect to the PIFA, because it allows a better volume reuse.
References[edit]
External links[edit]
Aperture Coupled Microstrip Patch Antenna Array For High Gain At Millimeter Waves
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Microstrip_antenna&oldid=911127123'
Gain Enhancement of a Microstrip Patch Antenna Using a Reflecting Layer
1Functional Devices Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
2Department of Electrical and Electronic Engineering, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 3Wireless and Photonic Network Research Center, Department of Computer and Communication Systems Engineering, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia
Received 20 December 2014; Revised 5 March 2015; Accepted 5 March 2015
Microstrip Patch Antenna Array Design To Improve Better Gains
Academic Editor: Giampiero Lovat
Copyright © 2015 Anwer Sabah Mekki et al. 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.
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Abstract
A low profile, unidirectional, dual layer, and narrow bandwidth microstrip patch antenna is designed to resonate at 2.45âGHz. The proposed antenna is suitable for specific applications, such as security and military systems, which require a narrow bandwidth and a small antenna size. This work is mainly focused on increasing the gain as well as reducing the size of the unidirectional patch antenna. The proposed antenna is simulated and measured. According to the simulated and measured results, it is shown that the unidirectional antenna has a higher gain and a higher front to back ratio (F/B) than the bidirectional one. This is achieved by using a second flame retardant layer (FR-4), coated with an annealed copper of 0.035âmm at both sides, with an air gap of 0.04 as a reflector. A gain of 5.2âdB with directivity of 7.6âdBi, F/B of 9.5âdB, and â18âdB return losses () are achieved through the use of a dual substrate layer of FR-4 with a relative permittivity of 4.3 and a thickness of 1.6âmm. The proposed dual layer microstrip patch antenna has an impedance bandwidth of 2% and the designed antenna shows very low complexity during fabrication.
1. Introduction
Microstrip patch antennas have been of interest for a long time due to their low profile, low cost, easy printability, and fabrication, as well as the capability of being embedded within other devices. However, there are many disadvantages, such as low gain and narrow bandwidth [1, 2]. The gain of an antenna refers to the ratio of its radiation power in a specific direction to its power in the isotropic direction [3]. Many researchers are working to enhance the gain of the patch antennas using different designs, ideas, and materials [4â11]. On the other hand, narrow bandwidth system implementation improves system selectivity in a number of applications, including military, security, digital enhanced cordless telecommunications, and low power systems [12]. At the same time, due to the new technologies, most designers tend to reduce the size and increase the efficiency of the devices.
One of the common methods to enhance the gain and directivity is the use of reflector planes. In [13], using the concept of complementary antennas, a planer antenna is presented with a U-shaped metal reflector to achieve a unidirectional propagation; the resultant antenna has a low profile, high F/B, and high gain along the operating frequency range. Moreover, in [14], a multiple metal back reflector is proposed for a wideband slot antenna. In [15], using a metallic cavity shaped as a reflector with a magnetoelectric dipole antenna, the proposed antenna exhibits a high gain with high F/B in the operating frequency range with relatively large dimensions.
But in [16], using a substrate rather than metal as a reflector is introduced to enhance the F/B radiation with aperture coupled antennas. In [17], a high impedance surface (HIS), in the shape of arrays of square cells, is used to reduce the back lobe propagation. The design shows an enhancement in the gain along the frequency range and high F/B. In [18], a dual band, unidirectional coplanar waveguide fed antenna (DB-CPWFA) is proposed. The reflector contains the ground plane, dielectric material, and artificial magnetic conductor. However, the dimensions of the antennas in the previous works are considered relatively large [13â18]. Therefore, achieving high gain while minimizing the size of the antenna is crucial. Kurogaze anime saint seiya.
Microstrip Patch Antenna Design
In this paper, a new microstrip patch antenna is designed, simulated, and fabricated. The effect of the reflector layer on the gain and directivity is studied and evaluated. Furthermore, the air gap thickness between the two layers of the substrates is investigated. By tuning and optimization, the desired characteristics are achieved and the effect of the multigeometrical shapes is shown. The simulation results are compared to the DB-CPWFA [18] and the conventional microstrip patch antenna [19]. The simulated results are validated by the measurements and the effect of the reflector layer is verified. The measurement results demonstrate that the gain, directivity, and F/B ratio of the antenna have been significantly improved.
2. Proposed AntennaMicrostrip Patch Antenna Array Gain Calculator
The proposed dual-layer microstrip patch antenna design was developed by taking the design of the conventional square patch antenna, then changing it by removing symmetrical parts from the left and right sides, changing the right angles to curves, and finally introducing a circular slot in the ground plane. Finally, the proposed design is accomplished using a second layer of FR-4, which is coated with a copper film at both sides, spaced 0.04 from the ground layer.
Microstrip Patch Antenna Design
In order to make the patch antenna operate at the desired characteristics, a tuning and optimization technique is introduced. Therefore, in order to make the design more flexible and workable during this procedure the proposed antenna contains multigeometrical details. In antenna designs, sacrificing some parameters is compulsory in order to enhance others [20].
Microstrip Patch Array Antenna Design
Figure 1 illustrates the dimensions of the proposed antenna. The overall dimensions are 60âmm à 55âmm à 8.3âmm. The substrate is FR-4, with a permittivity of 4.3 and loss tangent of 0.025, coated with annealed copper of 0.035âmm thickness at both sides. Four spacers are used, which are made of Teflon PTFE (polytetrafluoroethylene), which is a lossy material, with 2.1 relative permittivity. A second FR-4 layer, which is coated with annealed copper of 0.035âmm thickness at both sides, is placed at a distance of 0.04 from the first FR-4 layer. The second FR-4 layer acts as a reflector to redirect the propagation density from the back lobe to the main lobe. Hence, for the same radiation efficiency, increasing the directivity, , means increasing the gain, , as follows [3]:where is the radiation efficiency.
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