Slot-coupled Feed Research Articles

A compact wideband filtering rectangular dielectric resonator antenna with U-shaped metal strips

ABSTRACT In this paper, a compact wideband filtering rectangular dielectric resonator antenna (RDRA) loaded with a pair of U-shaped metal strips is proposed. By using a slot-coupled feeding structure, a rectangular DR with a length–width ratio of 3:1 is selected to combine the resonant frequencies of the TE 111 and TE 121 modes to achieve the passband. Two pairs of transverse branches with different lengths are added to the longitudinal microstrip feeding line, and the TE 111 , TE 11+δ1 , and TE 121 modes are successfully excited to enhance the bandwidth. The short pair of transverse branches can generate a null high-frequency radiation. A pair of U-shaped metal strips is loaded at both ends of the top of rectangular DR, introducing a low-frequency radiation null. Both radiation nulls can be independently adjusted. A pair of rectangular grooves is etched inside rectangular DR to boost the impedance matching level. The proposed filtering RDRA has been fabricated and measured for verification. The measured relative impedance bandwidth is 22.67% (4.34–5.45 GHz). The measured average gain and peak gain are 7.19 dBi and 8.06 dBi, respectively. RDRA filtering has broad application potential in modern communications, such as the N79 band.

Transparent ionic liquid antenna based on multi-modes using multiple feeding structures

With the rapid development of modern wireless communication technology, there is an increasing demand for the functionality of the communication system carried by a single platform. To improve the utilization of the antenna, a multimode liquid antenna is proposed in this paper. The antenna is fabricated using 3D printing technology and mainly consists of a cylindrical dielectric resonator, a coaxial feeding structure, and a slot-coupling feeding structure. By hollowing out the middle of a resin container and filling it with low-loss ionic liquid with stable dielectric properties, a liquid dielectric resonator antenna (DRA) is formed. The various resonant modes (slot mode, HEM11δ, TM11δ, TM21δ, and TM31δ modes) can be excited by introducing different feeding structures. The operating frequencies and radiation patterns can be modulated by mode switching. Simulated and measured results show that the antenna operates in the frequency bands of 2.25–2.76 GHz (20.4 %) and 4.82–5.73 GHz (17.3 %), and the maximum gain can be up to 10.3 dBi. The proposed antenna structure avoids the complex RF control circuit design, which has various applications including 5G/6G communications, transparent electronic devices, and Internet of Things.

An optically semi-transparent liquid antenna with slot-coupled feeding for future wireless communication systems

To meet the needs of optically transparent camouflage and concealment in the military field, as well as to improve the aesthetics and flexibility of wireless electronic devices. In this paper, a rectangular wideband liquid antenna with medium transparency and a hollowed-out center is proposed. The antenna is fabricated by using 3D printing technology and is primarily composed of a hollowed-out rectangular resin container, a transparent ionic liquid, and a non-transaprent slot-coupled feeding structure. By removing the center of the resin container and filling it with air, a resonator is formed that merges a rectangular ring with air. This method decreases the equivalent relative permittivity of the entire resonator and expands the operating bandwidth. Experimental results show that the antenna has an impedance bandwidth of 7 GHz-8.25 GHz, a relative bandwidth of 16.4%, a optical transparency of 84.57% and a maximum gain of 9.5dBi at 8 GHz. The proposed antenna has potential applications in electronic countermeasures, multimode composite guidance, 5G communication, and transparent electronic devices.

A Wideband Circularly Polarized Filtering Antenna Based on Slot-Patch Structure

This letter presents a wideband circularly polarized (CP) antenna with filtering radiation response based on a slot-patch structure. The proposed CP filtering antenna is composed of a top patch, a middle microstrip-to- (“+”-shape) slot structure, and a bottom metallic reflector. The middle layer not only functions as a slot-coupled feeding structure but also operates as a driven slot CP antenna. The top and bottom layers are used to reduce the slot antenna backside radiation and enhance the antenna axial ratio (AR) bandwidth. In addition, a diagonal slot etched on the patch and an additional E-shaped slot on the middle layer can generate the lower- and upper-band radiation zeros, respectively. For verification, the antenna is implemented. The measured results show that the overlapping bandwidth of the impedance and AR bandwidth is 46.9% (3.35-5.40 GHz). The measured average CP gain is about 7.6 dBic. High frequency selectivity and better than 10 dB out-of-band radiation rejection level is obtained. Compared to the conventional filtering CP design method which employs the filter or resonator feeding circuit, the proposed design features a simple structure, higher realized gain and wider AR/impedance overlapping bandwidth.

A High-gain, Low-profile Filtering Antenna Based on a Novel Metasurface

In this paper, a filtering antenna based on a metasurface is designed using slot-coupled feeding, and the metasurface unit is a fractal pattern. Replacing the rectangular patch on the metasurface with a fractal patch can introduce a radiation zero point on the upper sideband of the antenna, thereby enhancing the sideband selectivity. In addition, the current is reversed by loading shorting pin, and a radiation zero point is also introduced in the lower sideband. After measurement, the -10 dB impedance bandwidth of the filtering antenna is 23.6% (3.22-4.08 GHz), and the average antenna gain in the passband is 8.1 dBi. The filtering antenna does not involve an additional filter circuit, has a simple structure, and a small size, and ideally eliminates insertion loss. To verify, the real object was made and tested and found that the reflection coefficient, pattern, gain, etc. were in good agreement with the simulation results, it can be applied to the 5G communication frequency band.

A Low-Profile Broadband Metasurface Antenna With Polarization Conversion Based on Characteristic Mode Analysis

In this paper, a low-profile, broadband metasurface antenna for polarization conversion is proposed based on characteristic mode analysis (CMA). A new type of metasurface unit with a partially chamfered symmetrical triangular structure is designed. The inherent physical characteristics of the antenna are analyzed based on CMA, and the expected characteristic modes are selected for excitation at a suitable position. Slot-coupled feeding via microstrip line realizes the performance of wide impedance bandwidth and axial ratio bandwidth (ARBW). The measured -10 dB impedance bandwidth of 36.3% (4.38–6.32 GHz) and the 3 dB ARBW of 20.1% (5.41–6.62 GHz) are achieved. The left-hand circular polarization (LHCP) is realized, and the measured highest gain in the working frequency band is 6.05 dBic. The overall size of the designed and fabricated metasurface antenna is 0.58 λ0 × 0.58 λ0 × 0.07 λ0at 5 GHz. The proposed metasurface antenna can be well used in C-band satellite communications due to its low profile, broadband, and circular polarization.

High Gain and Wideband Fabry-Perot Resonator Antenna Based on a Compact Single PRS Layer

In this paper, a wideband and high gain Fabry Perot Resonator Antenna (FPRA) is proposed. It is based on a synthesized compact single partially reflective surface (PRS) layer acting as a superstrate to a slot-coupled feed antenna, which acts as a radiating source element for the proposed design. The PRS is based on a 2-D printed unit cell, where the lower part is a simple circular ring Frequency Selective Surface (FSS), incorporated with a synthesized FSS unit cell, using an automated system through a VBA based interface established between CST Microwave studio and Matlab, and optimized using a binary genetic algorithm. This new FSS layer acts as the upper part of the proposed PRS layer and provided a positive phase gradient. It almost perfectly resembles that of the optimum PRS over the desired frequency range, with a relatively high reflection magnitude, which makes it a promising superstrate candidate for wideband and high gain FP resonator antennas. The fabricated prototype achieved an important performance in terms of impedance bandwidth with 42%, ranging from 11.32 to 17.35 GHz. In addition, the 3-dB gain bandwidth is 36 % from 11.68 to 16.78 GHz, with a maximum peak gain of 14.72 dB achieved at 16 GHz. Consistent and almost invariant radiation patterns are achieved over the Ku-band frequency band of interest. The experimental and simulated results are in good agreement, justifying the feasibility of the proposed design as a high gain and wideband FP resonator antenna.

Planar Broadband Higher-Order Mode Millimeter-Wave Microstrip Patch Antenna Array With Low Sidelobe Level

AbstractIn this letter, a planar broadband higher-order mode millimeter wave (MMW) microstrip patch antenna array with low sidelobe level (SLL) is presented. For the antenna element, antiphase-TM30 mode is excited by unequally etching the radiating patch with two transverse slots. Meanwhile an SIW-based pin-loaded slot coupling feeding structure is introduced to achieve merits of broadband, low cross polarization and low backward radiation. Then a one-eight power divider with in-phase unequally tapered amplitude distribution is adopted to excite an eight-element array with SLL. The GCPW-SIW transition structure is also selected to achieve broadband impedance matching. Finally, both element and array antenna are optimized and fabricated for verification. For the antenna array, the measured -10 dB impedance bandwidth is from 25.1 to 31.3 GHz (22%) with a maximum gain of 14.6 dBi at 29.5 GHz and a 3dB gain bandwidth of 27.9%. And the measured SLL at 26, 28 and 30 GHz are all less than 20 dB. Index TermsMillimeter-wave (MMW), broadband, higher-order mode, low sidelobe level (SLL).

Metamaterial‐based linear phased array antenna with improved wide‐angle scanning bandwidth by parasitic metal strips

Two metamaterial-based linear phased array antennas with improved wide-angle scanning bandwidth are designed in this study. Metamaterial antenna element consists of a metamaterial patch, periodic metal strips, distributed metal strips and slot coupling feeding structure. The bandwidth of the metamaterial antenna is improved by loading the periodic metal strips. Wide-angle scanning bandwidth of arrays is attributed to the distributed metal strips. For an E-plane array, the central element has a relative bandwidth of 30.0% (4.33-5.86 GHz) for Voltage standing wave ratio (VSWR) <2 and the main beam can scan up to ±70° with a gain fluctuation less than 3.3 dB. For an H-plane array, the central element has a relative bandwidth of 26.2% (4.41–5.74 GHz) for VSWR <2 and the main beam can scan up to ±70° with a gain fluctuation less than 2.5 dB. Two 7-element linear phased array antennas are fabricated to verify the scanning performance. The measured and simulation results are in good agreement. The proposed antennas can be promising candidates for C-band radar and satellite communication.

Backlobe Radiations Reduction with Patch Antenna Using Multilayered Dielectric Structure

Backlobe radiations are the key stumbling block to using microstrip patch antennas in wireless communication, but they can be minimised by using a slot-coupled feeding technique. This paper proposes a microstrip patch antenna with a multilayer structure. The Ansoft High Frequency Structure Simulation is used to describe and model this slot-fed antenna, which has an improved gain of 5.6dB and directivity of 5.9dB and resonates at a frequency of 2.25GHz.

Wideband via-Loaded Cylindrical Open-Ended SIW Cavity Antenna

A composite cavity-based antenna is proposed and presented in this work. Three kinds of modes of the composite structure are involved to obtain a wide bandwidth: the ${\mathrm {TE}}_{11 {\scriptstyle {}^{\scriptstyle 1}}\hspace {-0.224em}/\hspace {-0.112em}{\scriptstyle 2} }$ cavity mode of a cylindrical open-ended substrate integrated waveguide cavity, the odd TEM mode generated by loading two rectangular via holes inside the cavity, and the higher-order loop modes (L3 and L5) of a circular ring detached from the cavity by a circumferential slot located at the cavity’s side wall. In the implementation of the antenna, slot coupling feeding methodology is applied, which also introduces a resonance for the bandwidth enhancement. A simulated fractional impedance bandwidth of 57.3% with $|{\mathrm{ S}}_{11}| dB from 24.9 GHz to 44.9 GHz is achieved ( $|{\mathrm{ S}}_{11}|= -9.7$ dB at $f=27.7$ GHz is ignored). The antenna has a broadside radiation pattern within the operating frequency band and a maximum simulated broadside gain of 10.6 dBi at ${f}=27$ GHz. Multi-layer technique and metallized via holes processing, which become commercial nowadays, are two critical techniques of the presented antenna. The simple structure is benefit of the fabrication and the integration with other planar front-end circuits. The antenna is fabricated and experimentally verified. A small difference is observed between the measurement and the simulation. A measured fractional bandwidth of 52% from 27 GHz to 46 GHz ( $|{\mathrm{ S}}_{11}|= -9$ dB at ${f}=29$ GHz is ignored) and a measured maximum broadside gain of 9.5 dBi are achieved.

Double‐layer metasurface‐based low profile broadband X‐band microstrip antenna

In this paper, a novel technology based on double-layer metasurfaces is proposed in order to broaden the bandwidth of microstrip antennas, which has been verified in X-band linearly polarised and circularly polarised antennas. Referring to the conventional metasurface antenna that employs slot-coupled feeding, these designs add an extra metasurface between the radiation patch and the ground plane so as to establish dual resonance modes, TM10 and TM20. Following the adoption of the composite right/left-handed transmission lines principle, this technique aims to adjust the propagation constant in the right-hand region by introducing parallel inductors and capacitors to widen the dual resonant frequencies' interval, thereby realising a broadband antenna. In addition, the interlayer metasurface may also be utilised as a director to balance the E-field of the radiation patch. A linearly polarised double-layer metasurface antenna with a size of 0.8 0.8 0.058 (wavelength in free space at the centre frequency) is filled with F4B substrate with a dielectric constant of 2.2. It finally realises an impedance matching bandwidth (VSWR 2) from 8.41 to 11.67 GHz, occupying about 32.47 of the centre frequency. This circularly polarised antenna attains both an impedance matching bandwidth of 32.44 (i.e. 8.29–11.5 GHz) and an axial-ratio bandwidth of 19.72 (i.e. 9.6–11.7 GHz).

High-Isolation, Low Cross-Polarization, Dual- Polarization, Hybrid Feed Microstrip Patch Array Antenna for MPAR Application

This paper presents a high-isolation, low cross-polarization dual-polarized patch antenna for multifunction phased array radar applications. Its hybrid feed design has been implemented, and the vertical and horizontal polarizations are excited by a balanced-probe feed and a slot-coupled feed, respectively. Simulations and measurements have demonstrated an input isolation of 45 and 43 dB between the horizontal and vertical ports, respectively. For further improvement in the cross-polarization level, the image feed method is also implemented, and a $2\times 2$ -element array made up of designed elements with image configuration has been fabricated. The simulated and measured S-parameter and radiation patterns of the horizontal and vertical polarizations of the designed $2\times 2$ -element array are presented and the measured cross-polarization level of less than −37 dB is achieved. To examine the performance of the designed element in an array, a $3\times 3$ -element array of designed $2\times 2$ -element subarray is fabricated and tested. In the $6\times 6$ -element measurements, −35.4 and −36 dB cross-polarization levels for horizontal and vertical polarizations are achieved, respectively. Also, using the measured embedded element patterns, the cross-polarization level lower than −36 dB for scan angles up to 45° is achieved.

Dual-Polarized Filtering Antenna With Printed Jerusalem-Cross Radiator

This paper presents a design of dual-polarized antenna with embedded filtering circuits by using a printed Jerusalem-cross radiator and a ring slot-coupled feed structure. A square ring slot has been adopted to implement the coupling mechanism. It is excited by two orthogonal microstrip feedlines to achieve dual polarizations. Meanwhile, the slot-coupled feed network and printed Jerusalem-cross radiator form a coupled-resonator circuit that realizes a second-order bandpass filtering performance. Consequently, a dual-polarized antenna with a filtering performance is obtained without using extra filtering circuits. To demonstrate the idea, an antenna prototype operating at LTE bands 42 and 43 (3.4–3.8 GHz) is designed, fabricated, and measured. Measured results show that the proposed antenna provides good filtering and dual-polarized radiation performances. Furthermore, a four-element dual-polarized linear array is designed for high-gain applications.

A WiMAX circularly polarized antenna array using slot-coupling feeding technique

In this letter, we present a circular polarization antenna array using the novel slot-coupling feeding technique. This antenna includes eight elements which are installed in line, each array element is fed by means of two microstrip lines with equal amplitude and phase rotation of 90i¾?. The feeding microstrip lines are coupled to a square patch through a square-ring slot realized in the feeding network ground plane. With the presence of the slots, this antenna array is able to cover the range of frequency of 3 GHz to 4 GHz. The size of the proposed antenna array is 7λ × 1.8λ × 0.4λ. The measured gain is 15.2 dBi and the bandwidth of S11< -10 dB is 1 GHz 3-4 GHz, 28%. The antenna array is suited for the WiMAX applications. With the use of slot-coupling feeding technique, the measured bandwidth for axial ratio<3 dB is about 24% in the WiMAX frequency band 3.3-3.8GHz. The measured HPBW of the y-z planes is larger than 62i¾?. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:567-574, 2016.

Effect of Presence of Human Body on Antenna Gain

This paper focuses on the interaction between two types of antenna (Slot Coupled Patch Antenna and Probe Feed Patch Antenna) and human head model at 835MHz. Real experiments on human body and electromagnetic fields is not possible because of it the HFSS software has been used to simulate the head model and antenna as an exposure source. The simulation results (calculated in SAR and E field strength parameters) show that the electromagnetic fields can be absorbed in human tissues. Regular papers have been done in this way. In this paper it is shown that the human tissues can decrease the gain of antenna as an interaction.

A High-Isolation Dual-Polarization Substrate-Integrated Fabry-Pérot Cavity Antenna

A dual-polarization substrate-integrated Fabry-Pérot cavity (SI-FPC) antenna is presented in this paper. The patch embedded in SI-FPC is excited with a near-field coupled feeding structure for V-polarization and with a slot-coupled feeding structure for H-polarization. The feeding structures are separated by a ground plane to improve the isolation between the ports. As a design example, an antenna operating at 10.0 GHz is fabricated and measured. A high degree of port isolation (&lt;−40 dB) over the whole operating bandwidth (9.5–10.2 GHz) and good cross-polarization level (&gt;25 dB) can be achieved.

Design of Novel Wideband Circularly Polarized Antenna Based on Vivaldi Antenna Structure

This letter presents a novel compact wideband circularly polarized antenna by utilizing Vivaldi antenna structure as the design concept. The proposed antenna consists of four exponentially tapered patches, a circular metal wall and a feed network. Four tapered patches are sequentially rotated and vertically located in the circular metal wall which acts as a vertical ground plane. Slot-coupled feed technique is applied to feed the antenna. Feeding by a corporate feed network, wide impedance bandwidth and axial ratio bandwidth are achieved. Parametric studies are made to optimize the antenna. The experimental results show that the antenna exhibits a 3-dB AR bandwidth of 41.4% (3.45-5.25 GHz) and a 10-dB impedance bandwidth of 57.3% (3.06-5.52 GHz).

Microstrip Antenna Arrays Fed by a Series-Parallel Slot-Coupled Feeding Network

A novel concept of a feeding network of a microstrip antenna array composed of series-fed linear subarrays has been shown. The proposed feeding network utilizes a concept of a slot coupler, in which two microstrip lines are coupled through a slot in a common ground plane. As it has been shown, such a slot coupler provides equal-amplitude and out-of-phase output signals and, therefore, can be used for appropriate feeding (at the center) of a single linear antenna subarray that utilizes “through-element” series-feeding technique. The proposed concept of a slot coupler has been used for the design of an 8 × 8 antenna array, in which all 8 × 1 linear subarrays are series-fed, whereas all 8 linear subarrays are fed by a parallel feeding network.

Dual-polarised slot-coupled patch antenna excited by a square ring slot

A novel slot-coupling feeding technique for dual-polarised patch antennas is presented. A square patch is fed through a square ring slot excited by two non-overlapping feed lines printed on the same side of a single-layer substrate. With respect to other slot-coupling feeding techniques for dual-polarised patch antennas, the configuration here proposed exhibits a simple structure and a valuable symmetry property with respect to the two feeding ports, while preserving a satisfactory isolation. To show the working principle and the radiation properties of the proposed slot-coupled patch, a sample antenna operating in the 3.3–3.8 GHz WiMAXTM frequency band has been designed, prototyped and characterised.