Circularly polarised back-to-back microstrip antenna with an omnidirectional pattern

To use circular microstrip antennas as circularly polarized radiators, perturbations such as slits are added to resolve degeneracy in the fundamental modes. In this paper, posts are inserted between the circular strip and the ground plane and the degeneracy is resolved. the theoretical investigations of this new circularly polarized microstrip antenna are discussed. In the derivation of the theoretical equations, the field is expanded in terms of Green's functions corresponding to the circular cavity region terminated by an admittance boundary. Numerical examples are given for the frequency characteristics of the axial ratio and the input impedance and for the post dimensions to resolve the degeneracy. the radiation patterns and gains are shown for this antenna. the theory has been confirmed by model experiments.

A number of studies on the characteristics of cylindrical rectangular and circular microstrip antennas have been available in the open literature. The investigations of cylindrical triangular microstrip antennas, however, are relatively scant. Since the triangular patch can be a good substitute for the rectangular patch in microstrip antenna and array designs, due to its physically smaller patch size than the rectangular and circular ones, the related studies become interesting and important. This motivates the present study. In this article, both the cavity-model and full-wave analyses of cylindrical triangular microstrip antennas are described. Curvature effects on the input impedance and radiation characteristics for the antenna with various cylinder radii at its fundamental TM/sub 10/ mode are analyzed. Measured input impedances and radiation patterns are also presented for comparison. In addition, curvature effects on the cross-polarization characteristics of a triangular microstrip antenna at the TM/sub 10/ mode are also analyzed.

In this paper we present a suspended rectangular and circular patch circularly polarized (CP) microstrip antenna with coplanar capacitive feed. Of the two circularly polarized (CP) antennas presented here, the first antenna uses fractal geometry with center slot within the rectangular patch and other having two perpendicular slots etched on circular patch in order to get circular polarization. The first antenna has an axial ratio bandwidth ( 11 11 11 is well below −20 dB in range of CP operation. Measured values fairly agree with the simulated results.

A compact single asymmetric coplanar waveguide feed (ACPW‐fed) dual circularly polarized microstrip antenna that operates at 1.8, 3.9, and 5.2 GHz in the entire operating frequency band 600 MHz–6 GHz for the radar detection of the improvised explosive devices (IEDs) carried by a person is introduced. The proposed novel quasi‐omnidirectional antenna consists of single sided rectangular ring microstrip patch antenna. L‐shaped slots are etched at the two opposite corners of the rectangular ring, introducing new resonance and circular polarization waves at the mid and upper bands, respectively. The achieved dual half‐rectangular ring patch antenna (DHRR‐patch) is loaded with strips of various shapes delicately placed at the center of the radiator, providing new resonance at the upper band and the improvement of the CP features. The matching technique designed based on CPW 50 Ω microstrip transmission line combined with the dual broad band matching techniques through quarter‐wave transformer in conjunction with open stubs and distributed lumped element method constitutes the novelty of the study. Based on quasi‐TEM mn (q‐TEM mn ) mode, ACPW‐fed and CP‐slots are employed to generate CP radiations at the q‐TEM 11 and q‐TEM 21 modes, respectively, while the ground plane width is optimized to enhance axial ratio bandwidth (AR‐BW). Input impedance and radiation pattern calculations of the conventional structure using transmission line and cavity model‐based q‐TEM 01 mode are conducted, respectively. Numerical experiments of the studied monolayer antenna are carried out using Advanced Design System (ADS) Version 2009 environment software employing internal one‐port option to excite the antenna. The prototype of the proposed antenna with a compact dimension (0.27 λ g × 0.38 λ g × 0.02 λ g at 1.8 GHz where λ g is the guided wavelength of the q‐TEM 01 mode) is fabricated on high loss laminate FR4 substrate of volume 43 × 38 × 1.6 (mm 3 ) and relative dielectric constant of 4.4 with simple laboratory‐based traditional printed circuit board (PCB) etching process. Measurement results show a fractional impedance bandwidth (FIBW) of 11.1%, 5.9%, and 7.1%, axial ratio (AR) of 4.6, 2.2, and 0.5 dB, and peak gain of 3.7, 4.7, and 6.1 dBic at 1.8, 4.0, and 5.2 GHz, respectively, demonstrating its suitability for IED detection applications. To verify the efficiency of the proposed model, measured results are compared with the simulated results and good agreement has been established.

A novel microstrip antenna with four L-slits for achieving circular polarization (CP) operation is proposed. By introducing two pairs of the centrosymmetric L-slits, the high cross-polar level is effectively suppressed. The characteristics of the input impedance, axial ratio, and radiation patterns are simulated. The results show that the good CP performance of the proposed antenna can be obtained.

A horizontally polarized omnidirectional microstrip antenna is proposed in this paper. The structure of designed antenna is with two back-to-back horizontally polarized microstrip antenna elements. Gain variation on main radiation plane of this new antenna is analyzed and radiation theory is deduced; formula of directivity on main radiation plane is given. Better omnidirectional characteristic of this antenna can be obtained by decreasing patch physical length. Both simulated and measured results verify the omnidirectional radiation patterns and input impedance characteristics. Good omnidirectional radiation patterns (gain variation inE-plane less than ±0.4 dBi) and input impedance characteristics are obtained; moreover, cross polarization less than −20 dBi is achieved.

A simple theory based on the cavity model is developed to analyze microstrip antennas excited by a slot in the ground plane. By using an equivalent magnetic current source at the feed, the electric field under the patch is obtained in terms of a set of cavity modes. In particular, the loci of the slot feed location for achieving the circular polarization and the input impedance are computed and found to be in excellent agreement with the experimentally measured results. Simple but surprisingly accurate formulas for slot-fed circularly polarized microstrip antennas are derived and compared with those for probe-fed counterparts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microstrip antennas or patch antennas are popular for their attractive features such as low profile, low weight, low cost, ease of fabrication and integration with RF devices. Micro strip antennas have been found favorable because they are inexpensive to manufacture and compatible with monolithic microwave integrated circuit designs (MMIC). They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonance frequency. A Microstrip or patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. The most commonly employed microstrip antenna is a rectangular patch. The major disadvantages of Microstrip antennas are lower gain and very narrow bandwidth. Microstrip patch antennas have some drawbacks of low efficiency, narrow bandwidth (3-6%) of the central frequency. Millimeter wave technology being an emerging area is still much undeveloped. As micro strip antennas have found wide variety of application areas, a number of techniques are evolved to improve its limited bandwidth. A good approach to improve the bandwidth is increasing the thickness of substrate supporting the micro strip patch. However problems exist on the ability to effectively feed the patch on a thick substrate and the radiation efficiency can degrade with increasing substrate thickness. A substantial research needs to be done in this area as its applications are numerous. The radiation patterns and S11 performance are used for the analysis of the different configurations. In the present endeavor a rectangular patch antenna is designed on thick substrate and simulated using MATLAB software and configuration on different dielectric susbstrates was used .

It is well-known that the circular polarization (CP) bandwidth of a microstrip antenna is greatly related to its impedance characteristic. Several broadband antenna structures have been proposed and studied, such as using a thick substrate with low permittivity and a multi-resonator structure. Another method to enhance the impedance bandwidth is using slot antennas instead of the microstrip antennas. In this paper, a new CP design developed from the ring slot antenna is proposed. The antenna structure composed of a wide slot and a parasitic patch is with wideband characteristics. By adjusting the distance between the wide respectively, which are obviously higher than that of a same-size microstrip antenna. Also, the CP designs of wide slot antennas have been investigated to further improve the CP bandwidth. By protruding a T-shaped [3] or an L-shaped strip [4] from the ground plane, the CP bandwidth of the wide slot antenna can reach to 18 %. However, the available designs for the slot antenna with more than 20 % CP bandwidth are relatively few in the open articles. In this paper, a new CP design developed from the ring slot antenna is proposed. The antenna structure composed of a wide slot and a parasitic patch is with wideband characteristics. By adjusting the distance between the wide slot and parasitic patch, the CP bandwidth can be varied between 5 and 45%. Details of the proposed designs and the obtained results are shown and discussed.

A new technique to design single-feed circularly polarized (CP) microstrip antenna is proposed. The CP radiation is obtained by adjusting the dimension of the etched fractal defected ground structure (FDGS) in the ground plane. Parameter studies of the FDGS are given to illustrate the way to achieve CP radiation. The CP microstrip antennas with the second and third iterative FDGS are fabricated and measured. The measured 10-dB return-loss bandwidth of the CP microstrip antenna is about 30 MHz (1.558 to 1.588 GHz), while its 3-dB axial-ratio bandwidth is 6 MHz (1.572 to 1.578 GHz). The gain across the CP band is between 1.7 and 2.2 dBic.

A new planar quasi-magnetic–electric circularly polarized (CP) antenna is proposed. The antenna has a simple planar structure with a small size and a single feed, and produces an omnidirectional CP radiation pattern. It is based on a quarter-wave shorted patch connected with two printed strips. The tangential electric field at the main open aperture of the shorted patch can be considered as an equivalent magnetic current, while the two strips contribute two electric currents. With a single feed, the proposed antenna exhibits an inherent phase difference of about 90° for the two kinds of currents, and therefore, a CP radiation is obtained. The antenna is designed and fabricated. Measured results show that the antenna has an impedance bandwidth of 4.3%. In the band of interest, the antenna generates a circular polarization and an omnidirectional pattern in the plane perpendicular to the magnetic and electric currents, with an average axial ratio below 1.5 dB and a gain between 2.4 and 3.3 dBi.

Radiation performance of a circularly polarized (CP) truncated corner square patch on a conventional ground plane (GP) has been enhanced by using a simple and novel configuration of stacked dual GP. The proposed configuration employs a single fed truncated corner square patch etched onto a substrate grounded with a patch shaped small GP and having second square shaped GP of standard size separated from the first one with an air gap at an optimized distance. This configuration is ideal for many wireless and satellite communication applications. Simulated results indicate the best achievable axial ratio (AR) of about 0.4 dB for a stacked dual GP CP antenna compared to an AR of 2.7 dB for a conventional single GP CP antenna, indicating an improvement in cross polarized (XP) isolation of about 18 dB. AR bandwidth has also been improved by almost 100% with the stacked dual GP configuration when compared with conventional CP antenna. Improved radiation performance has been achieved without affecting impedance bandwidth and peak gain of the patch. Analysis based on GP size variation of the conventional CP antenna and stacked dual GP antenna reveals that stacked dual GP configuration results in compact CP antenna with good radiation performance.

Based on a resonant cavity model, this work presents an effective computer aided design (CAD) algorithm to design singly fed circularly polarized (CP) rectangular microstrip patch antennas. The CAD algorithm allows precise prediction of the antenna performance. The analysis of radiation pattern, input impedance, and axial ratio parameters confirm the success of the design. The experimental results from a manufactured prototype operating at 2.25 GHz are in good agreement with the CAD predictions. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 32–41, 1999.

рассматривается конструкция рамочной антенны с дипольными излучателями, разработанная на основе классической рамочной антенны. Данная антенная система способна эффективно работать на двух частотах: 140 МГц и 390 МГц, что делает ее применимой для широкого круга задач, включая системы связи и радиомониторинга. Для анализа характеристик антенны было проведено компьютерное моделирование с использованием высокопроизводительного программного пакета CST Studio Suite. Это позволило детально изучить электродинамические параметры антенны, такие как диаграмма направленности, входное сопротивление и частотные характеристики. Для подтверждения результатов моделирования был изготовлен физический макет антенны, после чего проведены его экспериментальные исследования. Измерения показали, что коэффициент полезного действия (КПД) антенны составляет минус 0.42 дБ, а коэффициент направленного действия (КНД) достигает 2.26 дБ. Сравнение данных, полученных в результате моделирования и эксперимента, продемонстрировало их высокую степень совпадения, что подтверждает точность проведенных расчетов и измерений. Полученные результаты свидетельствуют о том, что предложенная конструкция антенны обладает стабильными характеристиками и может быть успешно использована в практических приложениях. Подчеркивается важность комплексного подхода, включающего как численное моделирование, так и экспериментальные исследования, для разработки и оптимизации современных антенных систем the paper considers the design of a loop antenna with dipole radiators, developed on the basis of a classic loop antenna. This antenna system can effectively operate at two frequencies: 140 MHz and 390 MHz, which makes it applicable for a wide range of tasks, including communication systems and radio monitoring. To analyze the antenna characteristics, we performed computer modeling using the high-performance CST Studio Suite software package. This made it possible to study in detail the electrodynamic parameters of the antenna, such as the radiation pattern, input impedance and frequency characteristics. To confirm the modeling results, we made a physical model of the antenna, after which we studied it experimentally. Measurements showed that the efficiency of the antenna is -0.42 dB, and the directivity coefficient (DC) reaches 2.26 dB. Comparison of the data obtained as a result of modeling and experiment demonstrated their high degree of coincidence, which confirms the accuracy of the calculations and measurements. The obtained results indicate that the proposed antenna design has stable characteristics and can be successfully used in practical applications. The work emphasizes the importance of an integrated approach, including both numerical modeling and experimental studies, for the development and optimization of modern antenna systems

Experimental results have been obtained on a planar multioctave bandwidth flared microstrip slot. When crossed, the element is capable of horizontal, vertical, or circular polarization. A design was fabricated and measurements were taken to define the performance. The input impedance and radiation characteristics are shown to have a broadband response when configured as a cavity-backed element.