Proximity-coupled Feed Research Articles

Analysis of Wideband Circularly Polarized Ferrite-Loaded Antenna Based on Unidirectional Resonant Modes

We propose a wideband circularly polarized antenna that consists of a metallic patch and some parasitically coupled elements mounted on a grounded dielectric-ferrite substrate. The metallic patch is fed by a proximity-coupled feed line placed between the ferrite and the dielectric layers. The parasitically coupled elements are included to improve the impedance bandwidth of antenna and are excited through the metallic patch. The antenna utilizes the resonant modes of the structure, which rotate only in the clockwise or counter-clockwise direction. A semi-analytical solution based on the magnetic wall approximation shows that the resonance frequencies of the clock- and counter-clockwise resonant modes differ significantly when operating in the frequency range where the effective permeability of the ferrite layer is negative. Moreover, there is a good agreement between the model presented and full-wave numerical simulations. For the proposed antenna, the results show that the radiation bandwidth is more than 15.5% and the 3 dB axial ratio bandwidth is more than 50%. The proposed antenna is easy to design and fabricate, does not require a complicated feeding network, and has a wideband and wide-angle circular polarization.

Efficient Proximity Coupled Feed Rectangular Microstrip Patch Antenna with Reduced Harmonic Radiation

<p>This paper presents an efficient proximity coupled feed rectangular microstrip patch antenna with reduced harmonic radiation. The proposed antenna resonates in S-band at frequency of 2.45 GHz with bandwidth of 88.5 MHz. A very good return loss of -47.0546 dB is obtained for the Microstrip patch antenna. The antenna matching can be achieved with an appropriate line-patch overlap, but with a careful design consideration. Not only the good matching of the fundamental mode, but also the effect on the harmonic radiation from the other patch modes has been considered. Varying the length & location of the microstrip feed line and introducing a defect in the ground plane- the harmonic radiation from the other patch mode is reduced to minimum.</p>

Coplanar UHF RFID tag antenna with U-shaped inductively coupled feed for metallic applications.

In this paper, we present a novel compact, coplanar, tag antenna design for metallic objects. Electrically small antenna has designed for a UHF RFID (860–960 MHz) based on a proximity-coupled feed through. Furthermore, two symmetrical Via-loaded coplanar grounds fed by a U-shaped inductively coupled feed through an embedded transmission line. This configuration results in an antenna with dimensions of 31 × 19.5 × 3.065 mm3 at 915 MHz, and the total gain for the antenna is 0.12 dBi. The Via-loaded coplanar and U-shaped inductively coupled feeds allow the antenna to provide flexible tuning in terms of antenna impedance. In addition, a figure of merit is applied for the proposed tag antenna, and the results are presented. The read range is measured to be 4.2 m, which is very close to simulated values. This antenna measurement shows very good agreement with simulations.

Dual-Band Proximity Coupled Feed Microstrip Patch Antenna with ‘T’ Slot on the Radiating Patch and ‘Dumbbell’ Shaped Defected Ground Structure

<p>This paper presents Dual-Band proximity coupled feed rectangular Microstrip patch antenna with slots on the radiating patch and Defected Ground Structure. Initially a simple proximity coupled feed rectangular Microstrip patch antenna resonating at 2.4 GHz is designed. Etching out a ‘Dumbbell’ shaped defect from the ground plane and ‘T’ shaped slot from the radiating patch of the proximity coupled feed rectangular Microstrip patch antenna, results in a Dual-Band operation, i.e., resonating at 2.4 GHz and 4.5 GHz; with 30.3 % and 18.8% reduction in the overall area of the patch and the ground plane of the reference antenna respectively. The proposed antenna resonates in S-band at frequency of 2.4 GHz with bandwidth of 123.6 MHz and C-band at frequency of 4.5 GHz with bandwidth of 200 MHz, and a very good return loss of -22.1818 dB and -19.0839 dB at resonant frequency of 2.4 GHz and 4.5 GHz respectively is obtained. The proposed antenna is useful for different wireless applications in the S-band and C-band.</p>

Bandwidth Enhancement of Rectangular Microstrip Patch Antenna using Defected Ground Structure

<p>This paper presents the bandwidth enhancement of a Proximity Coupled Feed Rectangular Microstrip Patch Antenna using a new Defected Ground Structure - an ‘inverted SHA’ shaped slot on the ground plane of the proximity coupled feed rectangular Microstrip patch antenna. The parameters such as Bandwidth, Return loss, VSWR and Radiation efficiency are improved in the proposed antenna than simple proximity coupled feed rectangular Microstrip patch antenna without Defected Ground Structure. A comparison is also shown for the proposed Microstrip patch antenna with the antenna structure without Defected Ground Structure. The proposed antenna resonates in S-band at frequency of 2.4 GHz with bandwidth of 180 MHz. A very good return loss of -47.9223 dB is obtained for the Microstrip patch antenna with an ’inverted SHA’ shaped Defected Ground Structure. Implementing an ‘inverted SHA’ shaped defect in the ground plane of the proximity coupled feed rectangular Microstrip patch antenna results in 5.3% improvement in bandwidth with 16.01% reduction in the overall area of the ground plane as compared to the Microstrip patch antenna without Defected Ground Structure.</p>

Wearable textile patch antenna fed by proximity coupling with increased bandwidth

ABSTRACTThis letter presents the design methodology of a textile rectangular patch antenna with increased bandwidth. The broadening of the antenna operating band is obtained by using a proximity coupling feed line cascaded to a quarter‐wave impedance transformer. The design parameters used to enhance the antenna bandwidth are the widths of the feed line and impedance transformer. The proposed design procedure has been applied to the design of four antennas centered at 2.45 GHz using denim substrate and conductive fabric. All antennas have the same patch dimensions, but they were designed using different values for the widths of the feed line and impedance transformer. The measured 10‐dB return loss bandwidth of the antenna prototypes are 11.2%, 13.4%, 17.0%, and 24.0%, in good agreement with simulated results. The effect of human body proximity and antenna curvature on the performance of the designed antennas has also been analyzed. The antenna configuration investigated has demonstrated to be able to increase the antenna operating band. The proposed design procedure is flexible, allowing the design of antennas with a variety of bandwidth values. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1906–1912, 2016

A PROXIMITY-FED ANTENNA FOR DUAL-BAND GPS RECEIVER

A new design of dual-band L1/L2 GPS antenna is proposed. The antenna generates dual- band circularly polarized radiation by exciting a cross-slot and ring-slot of a concentric circular aperture using a proximity-coupled feed. Parametric studies show that the matching and axial ratio bandwidth of L1 (1.575 GHz) and L2 (1.227 GHz) bands can be independently tuned by alternating the ring radius and slot length. The range of frequency ratio and 3 dB center frequency can be highly adjusted by slot's parameters. The size of the antenna is 73 mm × 73 mm × 6.4 mm including the ground, corresponding to 0.29λ × 0.29λ × 0.026λ at 1.227 GHz.

Triple-Band MIMO Antenna for Mobile Wireless Applications

This letter presents a planar triple-band multiple- input-multiple-output (MIMO) antenna that meets GSM900/1800 and LTE2600 bands protocols. The antenna element contains three individual meander-line-type inverted-L radiators; the highest frequency band radiator is fed by a transmission line, while the other two utilize the proximity-coupling feeding mechanism driven by the highest band radiator. The MIMO antenna is incorporated with two symmetric triple-band antenna elements and two physical decoupling devices. The two antenna elements are closely spaced with 1/15 wavelength of the lowest band. The two decoupling devices, a T-shaped slot and a meandering microstrip-line resonator, are built for the highest and the lowest frequency bands, respectively. Meanwhile, a negligible mutual coupling effect in middle band is achieved by using a collinear-placed transverse meander-line pair in the MIMO antenna. The antenna prototype measurement results show good impedance matching with low mutual coupling effect. The calculated envelope correlation coefficient verifies the suitability of the proposed antenna for mobile wireless access applications.

A Comparative study of Proximity-Coupled Multiband Microstrip Antenna and Multimode Reduced Surface Wave Antenna

paper shows the comparative study of proximity-coupled feed, used for a multiband microstrip antenna (MMA) and multimode reduced surface-wave antenna based on the shorted-annular-ring reduced-surface-wave (SAR-RSW) element and the inverted-SAR-RSW ((ISAR-RSW) element. Microstrip antenna operates in four bands - WiMAX (3.3-3.7 GHz), LTE2300 (2300-2400 MHz), Bluetooth (2400-2485 MHz), and WLAN (5.15-5.35 GHz, 5.725-5.825 GHz). Microstrip antenna has excellent radiation features along with a steady gain over the operating bands. Multimode reduced- surface-wave antenna has a reduced return-loss bandwidth of less than 10-dB. Its range of operation is 1.164-1.255 and 1.552-1.610 GHz, a 3-dB axial-ratio bandwidth from 1.16 to 1.26 GHz and from 1.54 to 1.61 GHz. It produces a larger than 7-dBi gain in the entire operating band. To increase the impedance bandwidth, the multimode reduced-surface-wave antenna implements the proximity-coupled probe feeds. In order to restrain the mutual coupling between the SAR-RSW and ISAR-RSW elements, the defected ground structure band- rejection filters are implemented. Keywordsantenna, multiband, proximity feed, Microstrip antenna, Reduced surface wave element.

Proximity-Coupled Multiband Microstrip Antenna for Wireless Applications

This letter presents a new design of a multiband microstrip antenna with a proximity-coupled feed for operating in the LTE2300 (2300–2400 MHz), Bluetooth (2400–2485 MHz), WiMAX (3.3–3.7 GHz), and WLAN (5.15–5.35 GHz, 5.725–5.825 GHz) bands. In addition, it also covers 6-dB impedance bandwidth across the UMTS (1920–2170 MHz) band. The proposed antenna consists of a corner-truncated rectangular patch with a rectangular slot, meandered microstrip feed, and defected ground plane. The antenna is fabricated using 0.8-mm-thick FR4 substrate with a dielectric constant of 4.4 and has a small size of only <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$27\times 24~\hbox{mm}^{2}$</tex> </formula> . The antenna shows a stable gain over the operating bands and good radiation characteristics. The simulated and measured results are shown to have good agreements.

A Compact Dual-Band RFID Tag Antenna Mountable on Metallic Objects

A compact (50 × 50 × 4 mm3) dual-band radio frequency identification (RFID) tag antenna mountable on metallic objects is proposed for the ultra-high frequency (UHF) band (917∼923.5 MHz) and the microwave (MW) band (2.4∼2.45 GHz). With the proximity-coupled feed loop, the proposed antenna consists of two symmetric planar inverted-F antenna (PIFA) elements for the UHF band passive tag and a meander microstrip patch antenna for the MW band active tag. The performance of the proposed antenna is verified by mounting it on the different sizes of the metallic object. Furthermore, the passive tag antenna in the UHF band furthermore may be used for energy harvesting techniques to improve the lifetime of the active tag in the MW band. The measured maximum read range is 5.50 m in the UHF band and 14.15 m in the MW band when the proposed tag antenna is mounted on the metallic objects. The total efficiency for all operating frequency bands is higher than 50%. High isolation (&gt;12 dB) between tag antennas in the UHF band and the MW band is achieved.

A Novel Metal-Mountable Electrically Small Antenna for RFID Tag Applications With Practical Guidelines for the Antenna Design

A novel dual-layer electrically small radio-frequency-identification (RFID) tag antenna is proposed for metallic object applications. With a proximity-coupled feed method, two rotationally symmetric loaded via-patches are fed through an embedded dual-element planar inverted-F antenna (PIFA) array. With this configuration, the antenna volume is reduced to 0.08 λ×0.04 λ×0.007 λ while the measured antenna gain is 0.08 dBi at the frequency of 923 MHz. Studies demonstrate that the proposed antenna is a good candidate for ultra-high-frequency RFID tags to be mounted on metallic surfaces, especially in size-constrained scenarios. Meanwhile, a figure of merit, namely, NBG, is presented, with which a comparison among electrically small tag antennas is carried out. Finally, several guidelines are given out to facilitate the miniaturization of RFID tag antennas for metallic object applications.

A Compact Frequency-Reconfigurable Multiband LTE MIMO Antenna for Laptop Applications

A compact frequency-reconfigurable multipleinput-multiple-output (MIMO) antenna on a laptop is proposed for multiband LTE services. Each MIMO antenna consists of two planar inverted-F antenna (PIFA) elements, using a T-shaped dc line and two p-i-n diodes (D1 and D2), in conjunction with the proximity-coupled feed structure. By effectively minimizing its dimension and its interference with antenna performance, the proposed T-shaped dc line is designed to fit within the proximity-coupled feed structure. The proposed MIMO antenna covers the LTE 17/13 bands (704-787 MHz, VSWR <; 3) at State 1 (D1 and D2: ON state), and the LTE 20/7 bands (791-862 MHz, 2500-2690 MHz, VSWR <; 3) at State 2 (D1 and D2: OFF state). The proposed antenna obtains high isolation (> 20 dB), low envelope correlation coefficient (ECC <; 0.0161), and total efficiency of greater than 51%, for all operating frequency bands.

OPTIMIZATION OF A DUAL RING ANTENNA BY MEANS OF ARTIFICIAL NEURAL NETWORK

In literature, heuristic algorithms have been successfully applied to a number of electromagnetic problems. The associated cost functions are commonly linked to full-wave analysis, leading to complexity and high computational expense. Artiflcial Neural Network is one of the most efiective biological inspired techniques. In this article, an e-cient surrogate model is trained to replace the full-wave analysis in optimizing the bandwidth of microstrip antenna. The numerical comparison between ANN substitution model and full-wave characterization shows signiflcant improvements in time convergence and computational cost. To verify the robustness of this approach, all these concepts are integrated into a case study represented by a rectangular ring antenna with proximity-coupled feed antenna.

Microfluidic Based Ka-Band Beam-Scanning Focal Plane Array

An eight-element 1-D Ka-band focal plane array (FPA) capable of beam scanning based on microfluidic principles is presented. The FPA is placed at the back surface of an 8-cm-diameter extended hemispherical Rexolite ( $\varepsilon_{\rm r}=2.56$ , $\tan\delta=0.0026$ ) lens and consists of interconnected microfluidic reservoirs and channels constructed by bonding polydimethylsiloxane (PDMS) ( $\varepsilon_{\rm r}=2.8$ , $\tan\delta=0.02$ ) and liquid crystal polymer (LCP) ( $\varepsilon_{\rm r}=2.9$ , $\tan\delta=0.0025$ ) substrates. The antenna element of the array is a small volume (2.5 $\mu$ L) of liquid metal residing inside a low-loss Fluorinert FC-77 ( $\varepsilon_{\rm r}=1.9$ , $\tan\delta=0.0005$ ) solution. The array beam is scanned by moving the liquid-metal antenna among the reservoirs using an external pump. The proximity-coupled feed network of the array is passive and designed strategically to accommodate the position variation of the liquid-metal antenna element. The array operates with measured $7^{\circ}$ half-power beamwidth (HPBW), $>$ 21 dB realized gain, and 3.3% $\vert{ S}_{11}\vert dB bandwidth and provides $\pm 30^{\circ}$ beam-scanning range. The presented microfluidic-based beam-scanning technique operates without resorting to RF switches. Consequently, it is promising for high-power handling and low-cost realization of millimeter-wave high-gain beam-scanning antenna arrays.

A Wideband Reconfigurable Transmitarray Element

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. Two reconfigurable transmitarray elements, using single and stacked patches, based on proximity-coupled feeding and two balanced reconfigurable bridged-T phase shifters are presented. Both designs achieve over 400 of phase range and achieve average insertion losses of 3.6 dB. Compared to existing proposed transmitarray elements, the stacked-patch element has a much smaller physical profile, with a lens thickness of only 0.17 λ in free-space, while achieving a large bandwidth of 500 MHz at 5 GHz (10%). Other considerations such as the mutual coupling and beam squint of an array using the stacked-patch element are also discussed.

Single-Feed Dual-Band Dual-Linearly-Polarized Proximity-Coupled Patch Antenna

In this paper, two novel single-feed dual-band dual-polarized microstrip antennas, fed by proximity coupling, are presented. The first approach begins with a new patch antenna that provides dual-band dual-polarized operation by means of an open-circuit stub, added at the open end of the feed line. By adding a stub to the end of the feed line, one can make an antenna with two resonant frequencies. The first resonant frequency is approximately the same as that in the initial design, but the second frequency depends on the stub's length, the stub's location, and the location of the feed point across the patch's width. Moreover, the variation of the feed-line location with respect to the patch's length has no significant effect on the first resonance frequency, while the second frequency changes. The second approach that is studied to realize a dual-band dual-polarized design utilizes a microstrip-gap proximity-coupled feed mechanism. Further insight is sought through the investigation of the surface-current densities on the proposed patch antennas at their resonant frequencies. The radiation performance - including radiation pattern, cross polarization, and gain - is satisfactory within two bands. The CST simulation results and measurement results showed good agreement with each other.

Reconfigurable Beam Steering Using a Microstrip Patch Antenna With a U-Slot for Wearable Fabric Applications

Reconfigurable beam steering using a microstrip patch antenna with a U-slot is proposed for wearable fabric applications. The proposed antenna was manufactured on a fabric substrate and designed to steer the beam directions at the operation frequency of 6.0 GHz. The U-shaped slot and a proximity-coupled feeding technique are applied to design the proposed antenna. By configuring two artificial switches between the proximity-coupled feed and the antenna patch, the antenna is given three beam directions (S0, S1, and S2). The maximum beam directions are steerable in the yz -plane (θ = 0° , 30° , and 331° , respectively), and the overall HPBW is 115°. The measured peak gains are 6.11-6.69 dBi.

Wideband RFID Tag Antenna for Metallic Surfaces Using Proximity-Coupled Feed

A low-cost, wideband patch antenna for radio frequency identification tags mountable on metallic surfaces is presented. A novel proximity-coupled feed structure, in which the direction of the microstrip feed line is parallel to that of the resonant length of the radiating patch and one end of the feed line is shorted to the ground, is proposed to perform simple and wideband impedance matching between the antenna and tag chip without any additional matching networks. The proposed design is verified by simulation and measurement. The measured 3-dB return-loss bandwidth is about 49 MHz, which totally covers the 26-MHz bandwidth requirement in North America. The measured read range is about 8.9 m when the tag antenna is mounted on a metal plate with a size of 200 × 200 mm2.

Application of Novel Cavity-Backed Proximity-Coupled Microstrip Patch Antenna to Design Broadband Conformal Phased Array

A broadband conformal phased array consisting of 48 linear arrays with four microstrip antennas is presented in this letter. The element is designed by a novel proximity-coupling feeding mechanism with a cavity-backed configuration. A dielectric layer, which is integrated on the surface of the antenna, is designed and fabricated to shield the patches. It plays a role similar to the conformal radome. In addition, the vertical connection between the element and the coax probe is designed, which is a benefit for increasing the space usage. The measured results indicate the bandwidth of the center embedded element is 27.6% with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | below -10 dB. Due to its simple single-patch structure, the fabrication errors can be easily controlled.