Compact circularly polarized asymmetric‐slotted microstrip patch antennas

This paper presents a single-feed circularly polarized (CP) microstrip antenna achieved by defected ground structure. With the proposed DGS, a new resonant mode is added, which is orthogonal to the original resonant mode. These two modes will have the same magnitude and the 90° time-phase difference by adjusting the DGS dimensions, which contributes to achieve the CP radiation. Both the simulated and measured 10-dB impedance bandwidth of the CP microstrip antenna are 30 MHz, while the 3-dB axial-ratio bandwidth is 6 MHz. The CP gain across the 3-dB AR band ranges from 4.6 to 5.0 dBic.

Circularly polarized diagonally symmetric slotted microstrip-patch antennas are proposed with compact size. The compact circularly polarized (CP) diagonally symmetric slotted microstrip-patch (DSSMP) antenna design rules are also summarized. Circularly polarized radiation can be achieved using any arbitrarily shaped slots in diagonal directions on the square microstrip-patch antenna. Different shapes for the slots are studied and compared, based on the fixed overall volume of the antenna for circularly polarized diagonally symmetric slotted microstrip-patch antennas. The cross-shaped-slot diagonally symmetric slotted microstrip-patch antenna is compact when compared with the circular-, square-, and circular-ring-shaped diagonally symmetric slotted microstrip-patch antennas. A measured 3 dB axial-ratio (AR) bandwidth of around 0.7% (6.0 MHz) with 2.0% (18.0 MHz) impedance bandwidth was achieved. The measured boresight gain was more than 3.3 dBic over the operating band, while the overall antenna size was 0.272λ0 × 0.272λ0 × 0.0138λ0 at 0.905 GHz.

A new technique for designing the active microstrip antenna for circular polarization is presented. The circular polarization is achieved by four slits and a pair of truncated corner and the operating frequency is electronically controlled by the bias voltage of varactor diodes. Theoretical modal for an antenna is developed using modal expansion cavity model and circuit theory concept. The results are validated with MoM-based simulator and experimental results. A good agreement between the simulated, calculated, and experimental results is obtained. The tuning range is found to be 40.24% and shows about 71% reduction in antenna size as compare to the conventional circular polarized antenna.

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 simple design of a probe-feed microstrip antenna with circular polarization (CP) radiation is presented. By embedding dual slits in a square microstrip and adjusting the sizes of the slits, an H-shaped microstrip antenna with two near-degenerate orthogonal modes for CP radiation can be achieved. This design provides a wide CP bandwidth and relaxed fabrication tolerances. Details of the antenna design are described, and theoretical and experimental results of the CP performance are presented.

In this paper, a compact dual feed circularly polarized microstrip antenna (CPMSA) is presented using 3-dB 2-branch line coupler as feed network. The antenna size is reduced by 39.9% by cutting slots in circular shaped CPMSA. The antenna characteristics are analyzed using cavity enclosure and radome cover. It increases the antenna bandwidth (BW) and gain. The compact CPMSA provides 26.8% BW for |S 11 | ≤ -10 dB and 3 dB axial ratio (AR) BW of 27% with maximum gain of 6.9 dBi at 2.8 GHz. Cross polarization (X-pol) of lower than -15 dB and front to back ratio (FBR) of more than 12 dB are obtained for the compact CPMSA. The designed antenna is fabricated and experimental results agree well with simulated results. The designed antenna can be used as transmitter and receiver in transponder systems to monitor missile health parameters.

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.

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 .

ABSTRACTNew designs of the circularly polarized micro-strip antennas (CPMSAs) based on tree fractal geometries are proposed, examined experimentally, and compared. The excellent circularly polarized (CP) radiation with minimum axial ratio (AR) of 0.26 dB is achieved by optimization of the key parameters (angle, length, and width) of the fractal trees etched on the ground plane. Parametric study revealed that the fractal tree defected ground structures (FTDGS) are responsible for satisfying the condition of CP operation. The micro-strip antennas with third iterative FTDGS and modified third iterative FTDGS are fabricated on FR4 substrate. The measured 10-dB return loss and 3-dB AR are 99 MHz (2.407–2.506 GHz) and 12 MHz (2.443–2.455 GHz), respectively, with stable gain of 4.52 dBic at 2.45 GHz, for third iterative FTDGS antenna. For modified third iterative FTDGS antenna, measured 10-dB return loss and 3-dB AR are 109 MHz (2.354–2.463 GHz) and 26 MHz (2.386–2.412 GHz), respectively, with gain about 4.62 dBic in the vicinity of center frequency 2.4 GHz. The proposed designs can be good candidates for the unlicensed 2.45 GHz industrial, scientific, and medical (ISM) band applications.

Utilizing evolutionary algorithms to achieve a low axial ratio of a circularly polarized microstrip antenna over a wide bandwidth and optimal impedance matching is the main aim of this study. A circularly polarized cross aperture coupled microstrip antenna using a 50Ω microstrip feed line is designed. A software simulation program (CST microwave studio) is used to design and compare the performance of the antenna in terms of return loss and axial ratio. Two distinct evolutionary algorithms; Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) have been applied to optimize the fitness function to ensure optimal axial ratio and impedance matching. The optimal patch dimensions, the aperture length, and the microstrip feed line length are obtained from both methods and their performances are compared. Moreover, the antenna is fabricated and the return loss is measured using a network analyzer. A comparative analysis is carried out demonstrating a high agreement between measured and simulated return loss.

A new triple proximity-fed circularly polarized microstrip antenna

A new circular‐polarization (CP) design of an annular‐ring microstrip antenna operating at the fundamental TM11 mode is presented. The CP radiation of the proposed design is achieved by connecting an L‐shaped strip to two orthogonal sides of the inner boundary of the annular‐ring patch. A prototype of the proposed antenna fabricated on a foam substrate has been implemented and studied. The results show that good CP‐radiation performances are obtained and the 3‐dB axial ratio is about 2%. Good agreement is also obtained between the measured and simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 156–157, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20237

Hexagonal microstrip antenna with perturbed edges and a single coaxial feed has been proposed for circular polarization. The configuration has been realized by inserting perturbations along two opposite sides of the hexagonal microstrip antenna. Both left-hand and right-hand circular polarization is obtained, simply by displacing the feed location by 90 degree. The measured bandwidth corresponding to VSWR ¿ 2 of 26.2 MHz and the 3 dB axial ratio bandwidth of 6.01 MHz has been achieved for the antenna which is designed at 915 MHz. Theoretical results have been validated with experiments.

This research presents an inverted ‘T’-shaped Defected Ground Structure (DGS)-loaded single feed circularly polarised nearly square microstrip patch antenna for wireless communication applications. The proposed antenna structure uses an inverted ‘T’-shaped DGS and exhibits an overall impedance (S11< −10 dB) of 665 MHz (12%) and an axial ratio bandwidth of 140 MHz (2.61%) with right-hand circular polarisation having a gain of 3.91 dBi. The proposed antenna is designed, simulated and fabricated using the FR4 substrate. The electrical size of the designed microstrip patch antenna is 0.238λ × 0.216λ. Using an inverted ‘T’-shaped DGS, the antenna size has been reduced by 13.8%. The detailed design and analysis of the proposed broadband circularly polarised microstrip patch antenna are discussed and presented. The fabricated antenna is tested, and the measured impedance bandwidth is 557 MHz (10%). The measured results are in good agreement with simulated results, and the proposed antenna can be suitable for WLAN, Wi-MAX and Hyper LAN applications.

A new circular polarization microstrip antenna having a defected ground plane is presented in this paper. A defect on the ground plane is introduced by inserting a square ring slot just below one of the top corners of the patch. The inserted slot on the ground creates a perturbation in the patch as like as conventional perturbed circular polarization antennas. The measured 3-dB axial ratio bandwidth was 1.26% with a gain of around 6.1 dBic.