Compact Circularly Polarized Microstrip Antenna Research Articles

A novel sequential‐phase quad‐feed circularly polarized microstrip antenna for INMARSAT and GPS applications

In this letter, a compact circularly polarized microstrip antenna has been developed with a new type of feed structure. The key feature of the antenna is the integrated design of the quad-feed network coplanar with the driven patch, which makes the antenna simple in structure and has good circular polarization performance. A parasitic patch is used to expand the impedance bandwidth, while a round hole in the center of the driven patch is used to improve impedance matching. In addition, a cavity is utilized to reduce the transverse size of the antenna and improve the front-to-back ratio. The simulation and experimental results show that the VSWR of the antenna is lower than 1.5 and the average gain is higher than 8dBic in the L-band for International Maritime Satellite applications. Due to the centrosymmetric feed configuration, the antenna can also be used as a global positioning system antenna, which requires high stability of the phase center.

Compact circularly polarized GNSS antenna with broad beam and stable phase center based on fragment‐type crossed dipoles

AbstractThis study is dedicated to the comprehensive design of a compact circularly polarized microstrip antenna and the integration of essential properties of stable phase center, broad bandwidth, and wide beamwidth into that antenna. Such a compact antenna in electronically low size was firstly achieved by technically using paired fragment‐type crossed dipoles and applying multi‐objective evolutionary algorithm with enhanced genetic operators. The design method has proved a triumphant one in simulations and experimental tests that it guarantees the proposed antenna to hold the capability of operating in broad band covering the popular GNSS, such as the GPS, BeiDou, Galileo, and GLONASS. The verified antenna has also demonstrated a great flexibility to design requirement that it allows the stable phase center beneath 3.5° over the whole GNSS bands, relatively wide beamwidth more than 130°, and much compact structure.

Compact Circularly Polarized Microstrip Ring Antenna Using Capacitive Coupling Structure for RFID Readers

This paper presents a compact circularly polarized microstrip antenna for radio frequency identification (RFID) readers. The dimensions of the proposed antenna are reduced by etching a cross slot in the radiation patch and loading four grounded coupling patches on the four corners of the radiation patch. An inverted Z-shaped coupling feedline is used to realize circularly polarized operation. The measured -10 dB |S11| bandwidth, 3-dB axial ratio bandwidth and maximum gain are 872-1095 MHz, 888-933 MHz, and 5.52 dBi, respectively, at 922 MHz frequency. The overall dimension of the proposed antenna is 0.36 λ g X 0.36 λ g X 0.05 λ g (λ g is the guide wavelength at the center frequency of 915 MHz). The proposed antenna has small size with good overall performance and is suitable for compact RFID devices.

Compact microstrip antennas with very wide ARBW and triple circularly polarized bands

This article presents two compact circularly polarized microstrip antennas with a very wide 3 dB axial ratio bandwidth and triple circularly polarized bands. A hexagonal stub (circular polarization element) along with tuning element in the ground plane is used for achieving wide 3 dB ARBW in antenna-1, while a novel approach of using a parasitic strip around the circular polarization element is used in antenna-2 for introducing band elimination notches in the circularly polarized band of antenna-1. The antenna-1 has a −10 dB impedance bandwidth of 12.34% (3.8-4.3 GHz), 84.02% (4.9-12 GHz), and 3 dB ARBW of 79.94% (4.9-10.9 GHz). The antenna-2 displays circularly polarized band elimination notch characteristics with −10 dB impedance bandwidth of 24.80% (3.85-4.94 GHz), 31.72% (6.1-8.4 GHz), 25.35% (9.3-12 GHz), and 3 dB ARBW of 4.84% (4.63-4.86 GHz), 19.08% (6.02-7.29 GHz), and 5.7% (9.54-10.1 GHz). Both the antennas are designed and fabricated on FR4 substrate of dimension (0.52 × 0.52 × 0.04)λ0 at a frequency of 7.9 GHz.

Compact circularly polarized inset-fed circular microstrip antenna for 5 GHz band

This paper proposes a compact circularly polarized microstrip antenna with Left-Hand Circular Polarization (LHCP) property for wireless communication system at 5.7GHz (U-NII 5GHz band). In this design, a tapered-slot is included and it can act as the second signal source of the antenna to generate circular polarization property and this can remove the need of the external second signal source. The axial ratio of ∼2 and the radiation pattern results prove that the designed antenna meets the LHCP criteria. Moreover, the inset feeder is selected and it demonstrates the improvement on bandwidth and input impedance of the antenna.

Compact Circularly Polarized Microstrip Antenna With Cross-Polarization Suppression at Low-Elevation Angle

This letter presents a method of cross-polarization suppression at low-elevation angle for a compact circularly polarized (CP) microstrip antenna. The compact CP antenna adopts a circular radiation patch with a crossed slot to reduce the dimensions, and a four-feeding-point technique is utilized to excite the patch for CP operation. The height and the diameter of the compact CP antenna are $0.064\, \lambda $ and $0.264\, \lambda $ ( $\lambda $ is the free-space wavelength at 1.2 GHz). At the outside of the CP antenna, a compact meander-line ring cavity (MLRC) structure is introduced, which can reduce the cross polarization from –14.2 to –26.1 dB in horizontal direction and increase 3-dB-axial-ratio (AR) ( ${\text{axial}\; \text{ratio}} \leq {\text{3 dB}}$ ) beamwidth from 128° to 192°. The height and diameter of the cavity are just $0.064\, \lambda $ and $0.448\, \lambda.$ Through the experimental validation, the impedance bandwidth of the proposed antenna for VSWR ≤ 2 is 20.8%, and the CP bandwidth for axial ratio ≤ 3 dB is 8.5%. Because of the MLRC, the cross polarization at low-elevation angle is clearly suppressed and the level at $\theta = \pm 90^\circ $ is not more than –23.2 dB. The 3-dB AR beamwidth reaches 190°. In the operating band, the peak gain of 5.3 dBic is also obtained.

A COMPACT CIRCULARLY POLARIZED MICROSTRIP ANTENNA WITH BANDWIDTH ENHANCEMENT

A novel compact circularly polarized microstrip antenna (CPMA) with bandwidth enhancement is proposed and studied. By employing capacitive loading and inductive loading, the size miniaturization is achieved. The cross-shaped aperture in the ground plane is able to excite two orthogonal modes. The near-equal amplitudes and 90 ◦ phase difference between these two modes are realized by properly designing the feed network, i.e., a 0 ◦ -90 ◦ hybrid comprising a 3-dB Wilkinson power divider cascaded with a 90 ◦ phase shifter. The proposed antenna exhibits a global bandwidth of 11.5% ranging from 1.88 GHz to 2.11 GHz with an overall size 50 mm × 50 mm × 6. 8m m (0.33λ0 × 0.33λ0 × 0.045λ0). The global bandwidth is defined where return loss is larger than 10 dB, broadside axial ratio (AR) smaller than 3 dB, and gain above 0 dBic.

High-Efficiency Compact Circularly Polarized Microstrip Antenna With Wide Beamwidth for Airborne Communication

The letter presents a compact circularly polarized (CP) microstrip antenna for airborne communications. The antenna adopts a square radiation patch with a cross slot to reduce the antenna dimensions and improve the impedance matching. For the high radiation efficiency of the proposed antenna, the no-resistor series feeding network is utilized to construct the antenna. In addition, the proposed structure also brings a super-wide beamwidth in axial ratio (AR) radiation patterns. To confirm the performances of the novel structure, an L-band prototype of the antenna is manufactured and tested. The thickness and the side length of the antenna are $0.073{\lambda _0}$ and $0.275{\lambda _0}$ , respectively ( ${\lambda _0}$ is the wavelength in free space). The impedance bandwidth for ${\rm VSWR} \leq 2 $ reaches 22.4%, and the AR bandwidth for ${\rm AR}\leq3 \hbox{dB}$ reaches 6.8%. In the overlap band, the radiation efficiency of more than 97% and the gains of more than 5.2 dBic are obtained. Especially, the beamwidth for ${\rm AR} \leq 3 \hbox{dB} $ can cover more than 180°.

Design and testing of a compact circularly polarised microstrip antenna with fractal defected ground structure for L‐band applications

A compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492-1.518 GHz) is presented. Two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation. To improve the performance parameters of patch antenna such as axial ratio (AR) bandwidth, return loss bandwidth, radiation efficiency and so on a new technique of combination of fractal theory and defected ground structure (DGS) is proposed for the first time in design of CP antennas. 44.74% size reduction in patch size, enhancements of 62.73% in AR bandwidth, 70.74% in return loss bandwidth and 4.03% in radiation efficiency is achieved as compared with conventional patch antenna, after incorporation of Koch curve fractal DGS in the ground plane. The performance of the developed antenna has been compared with other available L-band planar antennas in the literature, and it is found that the developed structure is better one in many aspects. Laboratory prototype of the antenna is fabricated and experimentally measured for cross verifying the simulated results.

Compact circularly polarized microstrip antenna for GPS applications

ABSTRACTA compact design of circularly polarized microstrip antennas is described. The antenna has a square‐ring radiating patch, and it is excited by a feeding network consisting of a quadrature coupler with dual lumped capacitors and an impedance‐matching circuit. The feeding network has a considerably smaller size than a traditional 90° hybrid, and therefore, it is placed at the inner slot of the square‐ring patch. By tuning the capacitance value of the lumped capacitors, the antenna can generate good circular polarization radiation. An antenna prototype designed for global positioning system applications is implemented. From the measured results, the 10 dB‐return‐loss bandwidth and 3 dB‐axial‐ratio bandwidth of the prototype are 3% and 1%, respectively. Simulation results obtained by HFSS are also provided to validate the experiment. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1293–1296, 2014

Single‐feed cross‐slot loaded compact circularly polarized microstrip antenna for indoor WLAN applications

ABSTRACTA novel single‐feed circularly polarized microstrip antenna with compact size is proposed for indoor wireless local area network (WLAN) applications. The antenna structure consists of eight slits which are introduced at the boundary and the corners in the radiating square patch with a cross‐slot at the center. The proposed antenna shows a compactness of 42% compared with the conventional circularly polarized antenna design at indoor WLAN frequency band. It is found that the resonance frequency of the proposed structure is highly depending on length and width of cross‐slot and corner slit for entire band of circular polarization. The 3 dB axial ratio bandwidth of the proposed antenna is 1.9%. Proposed structure is fabricated on the FR‐4 epoxy substrate and fed by a single coaxial probe. Measured results show a good agreement with the simulated results. Antenna shows stable radiation characteristics for the entire operating band. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1313–1317, 2014

RIS-Based Compact Circularly Polarized Microstrip Antennas

Compact, asymmetric\symmetric-slotted\slit-microstrip patch antennas on reactive impedance surface (RIS) are proposed and studied for circularly polarized (CP) radiation. The antennas consist of a slotted-slit-microstrip patch on a RIS substrate. The CP radiation with compact size is achieved by asymmetric\symmetric-slot-slit cut along the orthogonal\diagonal directions of the patch radiator. The asymmetric\symmetric-slotted\slit microstrip patches on the RIS structure are used for further miniaturization of the antenna with improvement in CP radiation. The measured results of the compact asymmetric-cross slotted square patch antenna are 1.6% (2.51-2.55 GHz) for 3-dB axial ratio bandwidth, 5.2% (2.47-2.60 GHz) for 10-dB return loss bandwidth, and 3.41 dBic for gain over 3-dB axial ratio bandwidth. The overall antenna volume is 0.292λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> × 0.292λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> × 0.0308λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> on a low cost FR4 substrate at 2.5 GHz.

A Compact Single-Feed Circularly Polarized Microstrip Antenna with Symmetric and Wide-Beamwidth Radiation Pattern

A compact single-feed circularly polarized microstrip antenna is proposed to achieve symmetric radiation pattern over a wide range of observation angles. In order to reduce the radiation aperture and consequently broaden the circular polarization (CP) and the half power beamwidth (HPBW) of the antenna, a partially etched superstrate and a conducting cavity are employed in the design. Further, reasonable axial ratio (AR) and impedance bandwidths are realized within the compact structure by using a simple series crossed-slot aperture coupled feeding. As a consequence, the overall dimension of the fabricated prototype is 0.32λ0× 0.32λ0× 0.12λ0at the center operating frequency of 1.56 GHz, and a 3.0% overlapped bandwidth of 10 dB return loss (RL) and 3 dB AR is obtained. Within the bandwidth, symmetric CP radiation pattern over almost the entire upper hemisphere is observed and the HPBW is also increased from 60° to 106°.

Erratum for ‘Compact circularly-polarised microstrip antenna with symmetric-slit’

Erratum for ‘Compact circularly-polarised microstrip antenna with symmetric-slit’

Compact circularly-polarised microstrip antenna with symmetric-slit

A single-fed compact circularly-polarised (CP) microstrip antenna is designed and experimentally demonstrated. By embedding the symmetric-slit in the radiation patch and protruding a pair of perturbation elements at the boundary of the centre square slot, the proposed antenna can obtain good CP performance with effective size reduction at a fixed frequency operation. Meanwhile, an impedance transformer is utilised for impedance matching.

Asymmetric-Circular Shaped Slotted Microstrip Antennas for Circular Polarization and RFID Applications

Novel asymmetric-circular shaped slotted microstrip patch antennas with slits are proposed for circularly polarized (CP) radiation and radio frequency identification (RFID) reader applications. A single-feed configuration based asymmetric-circular shaped slotted square microstrip patches are adopted to realize the compact circularly polarized microstrip antennas. The asymmetric-circular shaped slot(s) along the diagonal directions are embedded symmetrically onto a square microstrip patch for CP radiation and small antenna size. The CP radiation can be achieved by slightly asymmetric (unbalanced) patch along the diagonal directions by slot areas. Four symmetric-slits are also embedded symmetrically along the orthogonal directions of the asymmetric-circular shaped slotted patch to further reduce antenna size. The operating frequency of the antenna can be tuned by varying the slit length while keeping the CP radiation unchanged. The measured 3-dB axial-ratio (AR) bandwidth of around 6.0 MHz with 17.0 MHz impedance bandwidth is achieved for the antenna on a RO4003C substrate. The overall antenna size is 0.27λo × 0.27λo × 0.0137λo at 900 MHz.

Slits‐loaded microstrip antennas for circular polarization

AbstractNovel diagonally slits‐loaded compact microstrip antennas are proposed for circular polarization (CP). A group of four slits is loaded on the square patch radiator for compact antenna size with CP radiation. The slit with unequal sizes loaded on square patch in diagonal directions is used to achieve CP radiation. The combined V‐shaped and square slits, diagonally loaded, microstrip antenna is compact when compared with V‐shaped slits loaded microstrip antenna. The measured 10‐dB return loss and 3‐dB axial‐ratio bandwidths are 3.55% and 0.82%, respectively, for a combined V‐shaped and square slits loaded microstrip patch antenna. The overall size of the antenna is 0.256λ0×0.256λ0×0.0136λ0 at 2.55 GHz. The proposed slits‐loaded patch radiator is useful for compact circularly polarized microstrip antenna and array designs. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2043–2049, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25417

Compact Circularly Polarized Microstrip Antennas Using EM Coupled Loop Resonators

In this letter, compact loop resonator type circular polarization (CP) antennas with a square ring and an X-shaped meander loop are presented. Both antennas are fed to a microstrip line with electromagnetic coupling. By adjusting the gap and length of a coupled microstrip line, the magnitude and phase conditions of two orthogonal modes for CP can be determined. The proposed antennas show good axial ratios and also good agreements between experimented and simulated results.

Novel Compact Circularly Polarized Microstrip Antenna using Left-Handed Transmission Lines

A novel compact circularly polarized microstrip antenna using left-handed transmission lines is proposed in this paper. The antenna consists of a microstrip patch unit and two left-handed transmission line (LHTL) units. The microstrip patch unit is a square patch with a small square slot embedded in the center. The left-handed transmission line units located in the center of the square patch is composed of lumped elements, which work as 3 dB power dividers and 90 degrees phase shifters. The microstrip antenna is fed by a single probe, and the two inner adjacent sides of the square patch are connected to the LHTL units for orthogonal excitation. The measured results agree with simulated results, which show that the impedance bandwidth defined by VSWR less than 2.0 is 61 MHz (2481–2542 MHz). The front-to-back ratio on the pattern is larger than 15 dB and the axial ratio in the up hemisphere less than 2 dB. The proposed antenna has the attractive features such as compact size, low axial ratio, and simple structure.

Compact circularly polarised microstrip antenna design for dual-band applications

The design of a novel single-fed circularly polarised antenna dedicated for dual-band operations is presented. It is realised by integrating a dual-band dual-fed patch antenna with a dual-band branch-line coupler in a compact multi-layer structure. Measured impedance bandwidths of 20.1% (895 MHz) and 8.9% (2.397 GHz) are achieved.