جستجوی مقالات مرتبط با کلیدواژه « Microstrip Antenna » در نشریات گروه « فنی و مهندسی »

In this article, a microstrip antenna with suitable dimensions and wide circular polarization bandwidth has been designed, simulated, and built. This antenna is designed with an incomplete ground plane and dual feeding. Also, this antenna has an incomplete ground plane in a creative way, which is removed from the ground plane, in the proposed antenna with dual input and a quarter circular patch, which is presented with wide changes in the ground plane with the aim of creating a wide bandwidth and a suitable axial ratio. The antenna includes two long transmission lines and two ports in the antenna patch. The fabricated antenna has external antenna dimensions of 40 × 50 mm2 and FR4 substrate height of 1.6 mm. Using the incomplete ground plane in the proposed antenna improves the impedance matching and increases the parameters S and axial ratio (AR). The measurement results show that the proposed antenna with an incomplete ground plane can reduce the coupling and improve the circular polarization. The measurement and simulation results show that the proposed antenna has a wide bandwidth from 4.89 to 6.85 GHz for return loss.

In this article, a rectana microstrip antenna with optimal dimensions in the GSM band is proposed to harvest Rf energy and convert it into electricity. The proposed antenna is a special model of bow-tie antenna whose triangles are placed at 90 degrees to each other and it is fed in dipole form with SMA connector. The dimensions of the antenna are 10 x 10 cm with an FR4 substrate with a thickness of 1.6 mm, which is designed to receive in the GSM frequency band, i.e. 900 and 1800 MHz. The recommended antenna gain is 1.8dBi. The advantage of the proposed antenna compared to the examined antennas is the high efficiency of the RF to DC converter circuit and its small size. So that the efficiency factor obtained for it is 76%, which is 12% more than the previous examples. Also, the volume occupied by the proposed structure is at least 87.2% less than the structures presented in other references for this frequency band. On the other hand, due to the flatness of the proposed structure, this antenna has the ability to be used on flat surfaces such as the wall or body of various objects, while the antennas proposed in other references are 3D and lack this capability.

Passive Millimeter Wave Imaging Systems (PMWIS) are used to detect hidden objects. Millimeter waves, generated by thermal radiation, pass through textiles, smoke, fog, and living tissue, and these types of systems create high resolution images and they do not need external incident wave. In this research, a PMWIS at a frequency of 35 GHz has been designed and simulated and the basic parameters of this system such as spatial resolution and temperature have been calculated for the intended application. An Antipodal Fermi Tapered Slot Antenna (AFTSA) was designed and built with the Substrate Integrated Waveguide (SIW) and Grounded Coplanar Wave Guide (GCPW) impedance converter. The gain and radiation pattern of the antenna and the reflector antenna were calculated so that it had a suitable spatial resolution for the use of hidden object detection. The proposed system with linear scanning method (Raster) is able to form an image with a spatial resolution of 3.35 cm at a distance of 1.5 m from center of the antenna reflector and a temperature resolution of 0.11 k. In this system, the desired spatial resolution can be obtained by changing the position of the antenna and the more complex scanning methods.

The stealth technology is one of the most important strategies for protecting fighters and warships in the enemy's territory. Reducing the radar cross-section (RCS) of the antennas used in the radar of these fighters and ships is one of the stealth technology techniques. In this research, the methods of the radar cross section reduction for the microstrip antennas and their effects on performance of the antennas are presented. First, the radar cross section definition and the related governing relationships are presented and the importance of RCS reduction is discussed. Then, six main methods of radar cross-section reduction for microstrip antennas are introduced. These methods are: antenna shaping, electronic band gap (EBG), complementary split ring resonators (CSRRs), ground plane with frequency selective surface (FSS), metamaterial absorbers (MMA), and microstrip resonators. In each section, the radar cross section (RCS) of the reference and modified antennas are compared and the advantages and disadvantages of the relevant method is outlined.

A compact multiple-input–multiple-output (MIMO) antenna is presented for Long Term Evolution (LTE) applications. The antenna consists of a common square patch for ports and two ground plane with two separated microstrip feed lines. The antenna feed lines are placed perpendicularly to each other to obtain high isolation, and a T-shaped slot is added to reduce the mutual coupling of antenna elements in the operating frequency band. In this design two L-shaped radiator-elements are used for exiting two resonance frequencies that have connected to the patch by two metalized vias.  The proposed MIMO antenna has a compact size of 38×37.5 mm, and the antenna prototype is fabricated and measured. The measured results show that the proposed antenna design achieves an impedance bandwidth of larger than 1.92–2.67 GHz for port-1 and 1.69-2.96 GHz for port-2, low mutual coupling of less than 10 dB, and a low envelope correlation coefficient across the frequency band, which are suitable for portable LTE applications.

Circular polarization is one of the most popular polarization approaches used in different communication systems such as radar, satellite, GPS and WiMAX systems. In this article, we want to design a wideband cylindrical antenna with circular polarization and maximum frequency coverage from 1.7 to 2.7 GHZ. If the optimum load impedance of the amplifier at different frequencies are close, the antenna can be used as an optimal load for the amplifier. In this paper the output of the antenna after application of signals in the S band is also investigated and the effects of the antenna radiation on the amplifier circuits have been considered to some extent.

In this paper, the two novel reconfigurable polarized microstrip antennas with capability of switch between linear and circular polarization are presented. The main idea in this work is using some narrow graphene strips, as variable surface impedance, in the middle and the edges of a traditional square patch. The graphene strips are activated and deactivated by applying the two different DC voltages. Based on surface conductivity of graphene, the surface impedance of these strips are calculated in both of active and deactivate modes. The simulated results show that the polarization of the proposed antennas can be changed in two or three different cases in the frequency of X band. As a main advantage of the proposed antennas, the change of graphene bias voltage has no destructive effect on radiation patterns and antenna input impedance. In addition, the DC bias voltage of the graphene surfaces in active mode are not high.

In this paper, the design, synthesis, and simulation of 12 linear arrays of microstrip antenna is considered with cosecant squared pattern in 9.8 GHz. The structure involves 3 layers: the feed network has 2 bottom layers and the top layer is the microstrip patch excited by a slot. One of the advantages is low cross-polarization (less than -50 dB) that is due to removing the radiation fields of the feed network. For synthesis of cosecant squared pattern, the genetic algorithm method is used while the mutual coupling is considered. In this method, the far fields of each array are applied to the optimization. Proportional to the amplitudes and calculated phases by genetic algorithm, the feed network is designed. The simulation results verify the accuracy of design and synthesis.

For further and various applications of communication systems, we lead to using the overall of electromagnetic spectrum. Also, because of the developing f multiband wireless systems, antenna designers are enforced to design antennas matched to the operation in multi-band and multi-frequency. On the other hand, nowadays, the use of light-weight, simple, small and inexpensive antennas is an essential requirement for covering multi bands. In this paper, a microstrip antenna is designed and suggested fractal-based and utilized FR4 substrate with small size and light, and also ability to resonance in multi-frequency by increasing fractal repetitions and self-similarity property. Therefore, this proposed structure causes the antenna resonance in more frequencies, and also leads to miniaturization of its size. This antenna operates in 1-10 GHz range includes five frequency resonance for the most of convenient applications. Also, it has appropriate pattern and circular polarization which increases its applications. The antenna has been fabricated and there is a good agreement between measurement results and full wave simulation using HFSS software.

In this paper a novel structure of Microstrip Yagi-Uda antenna is introduced to use in two frequency bands of 0.915GHz and 2.440GHz. FR4 with dimension of 12×12.5 cm2 and height of 1.6 mm is used as substrate. A prototype of the antenna is fabricated to check its operation. Comparison of the simulation and measurement results confirms the operation of antenna. Return loss of the antenna at the operation frequencies is more than 20dB. Gain of the antenna at 0.915 GHz and 2.440 GHz is respectively 6.15 dB and 9.55 dB. Appropriate return loss, high gain at the operation frequencies, desired F/B ratio, low cost and compact size made this antenna suitable for various communication applications.

This study deals with a design and implementation of a microstrip patch antenna array that are feeding by Inset and Proximity methods. Results showed that antenna would have high frequency bandwidth and better impedance matching in Inset feeding. Also in Proximity feeding, unwanted radiation vanished because T-shape connections were eliminated. Simulation and experimental results cleared that antenna in the Proximity method has a smaller size, more gain and better impedance bandwidth than the Inset method. This paper chooses dielectric material FR4 with dielectric substrate permittivity of 4.4 by h=1.6mm. Therefore, operational frequency and input impedance are equal to 3.03 GHz and 50 ohm. Meanwhile, results showed impedance bandwidth and gain increased from 2.7% and 2dB for single arrays to 27.4% and 8dB for 5 arrays.

Recently Fabry-Perot (FP) resonator structures for enhancing directivity have found wide use in antenna design. FP Resonator antenna generally consists of primary radiator backed with a metal ground plane and a partially reflective surface (PRS). In this paper metamaterial unit cells is utilized as PRS in FP cavity for increasing microstrip antenna directivity. As a novel design an array of Omega unit cells is proposed and designed. FP antenna performance with Omega cover and superstrate of patch and SRR is simulated and compared. For validation of purposes, the antenna is designed and simulated through using of two different 3D full-wave electromagnetic simulation tools; CST Microwave Studio and Ansoft’s High Frequency Structure Simulator (HFSS).

Today، along with the advances in circuit printing technology it has become possible to fabricate band lines integrated with circuit elements. The band lines are known as microstrip lines and the whole packages are called microstrip antennas. The microstrip antennas have three layers، including conductive patch layer، dielectric sub layer، and ground conductive layer. One of the most important problems of prevalent antennas is their inflexibility، which was addressed in the current paper using textile based structure with proper flexibility and flexural stiffness. This was done using ink jet printing techniques followed by electrolytic plating to provide diverse antenna patterns based on nickel particles. The coated surface was characterized by scanning electron microscope، elemental analysis and optical microscope. Moreover، the washing fastness and the other physical and mechanical specifications were measured using standard techniques. The elemental analysis of metal-coated fabric clearly indicated a high level of nickel. Furthermore، the morphological investigation proved the formation of homogenous nickel nanoparticle in a diameter range of 100-500 nm with an evident boundary and semi-spherical shape. In addition، the cumulative presence of particles in a sequence followed a cabbage-like structure originating from metallic crystals. The washing fastness tests revealed a high stability in electrical resistance after several washing steps. In the meantime، the antenna gain and the corresponding bandwidth were measured using spectrum analyzer. The results indicated a 1 kHz increase in bandwidth and 11 dB decrease in antenna gain for a large size compared to a small one. Meanwhile، the bandwidth of rectangular pattern showed a 0. 2 kHz increase and 2. 5 kHz decrease compared to spiral pattern. Finally، the four-probe electrical conductivity test demonstrated a high level of conductivity around 2632 S/cm.