Coupling Slot Research Articles

Multi-polarized Fabry-Pérot resonator cavity using multilayer partially reflective metasurface in X-Band

In this paper, we propose a multi-polarized Fabry-Pérot resonator cavity (MPFPRC) by integrating the multilayer partially reflective metasurface (MPRM), the feed of multi-polarized slot coupling patch antenna and the reflective ground in X-Band. The MPRM consists of first-layer square metal patches, second-layer metal ground with square slots, third-layer square metal patches and fourth-layer partially reflective patches. Based on the MPRM, the proposed MPFPRC is capable of transforming 0°, 45° and −45° linearly polarized (LP) waves emitted by the feed into LP beam, left-handed circularly polarized (LHCP) beam and right-handed circularly polarized (RHCP) beam, respectively. Finally, the designed MPFPRC is simulated, processed and measured. The experimental results verify that the −3 dB gain bandwidth of LP is 9.1–10.2 GHz, the −3 dB gain bandwidth and 3 dB axial ratio bandwidth of the LHCP are 9.0–10.0 GHz and 9.2–10.0 GHz, and the −3 dB gain bandwidth and 3 dB axial ratio bandwidth of the RHCP are 9.0–10.0 GHz and 9.3–10.0 GHz.

High‐gain high‐selectivity TE20‐mode SIW‐fed metasurface filtenna array for 5G millimeter‐wave applications

AbstractA high‐gain high‐selectivity 4 × 4 metasurface (MS) filtenna array is presented in this paper for 5G millimeter‐wave (mmW) applications. The TE20‐mode substrate integrated waveguide (SIW) with two parallel coupling slots is applied as the differential feeding structure, which can produce a wide impedance bandwidth and good radiation performances, simultaneously. Additionally, the TE20‐mode SIW feeding line is well designed to operate as a λ/2 short‐circuited line at the upper edge frequency to gain a radiation null. Meanwhile, a folded U‐shaped slot is etched on each MS unit to generate a radiation null at the lower edge. As a result, a passband which covers our 5G mmW band (24.25–29.5 GHz) of interest can be realized. To validate the design, a 4 × 4 MS filtenna array was manufactured and measured. The simulated and measured results are in good agreement, demonstrating a −10 dB impedance bandwidth of 19.8%, a flat gain variation with a maximum value of 19.82 dBi, symmetrical radiation patterns, low cross‐polarization levels of –30 dB, and high out‐of‐band rejection levels of 25 dB.

Ultra-Wideband Six-Port Network Miniaturization—Matching

AbstractIn this paper, a new design approach for the six-port (SP) junction is introduced. The proposed design includes a generalized broadband matching and smooth miniaturization scheme and is extendable for any passive multiport structure. A multilayer technology and a microstrip to slot coupling operation are employed for the designed SP, which comprises power divider and three hybrid couplers. The conducted measurements of the constructed SP junctions validates the design approach. Optimal performance of the SP network in terms of miniaturization, bandwidth, and response accuracy were obtained for the 5G low band.

Ultrawideband Strip-Loaded Slotted Circular Patch Antenna Array for Millimeter-Wave Applications

A novel ultra-wideband millimeter wave (mmWave) slotted circular patch antenna and array are proposed in this paper, where each circular patch antenna element is loaded with three pairs of folded strips for enhancing the bandwidth and fed by a substrate integrated waveguide (SIW) through a coupling slot. As a result, a multimode antenna element with the ultra-wideband characteristic can be realized and the impedance fractional bandwidth (FBW) with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |< -10 dB is up to 66.9%. Furthermore, an 8×8 antenna array prototype is designed and fabricated. Measured impedance FBW with | <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |< -10 dB of 56% and measured average radiation efficiency of 73.8% are achieved. With the wideband and low-profile features, this antenna can be a promising candidate for mmWave communications.

An Analytical Approach for Resonant Frequency Prediction of Complex Single-Channel Irregular Coupling Slot

An Analytical Approach for Resonant Frequency Prediction of Complex Single-Channel Irregular Coupling Slot

Broadband metasurface antenna with size‐varying square patches

AbstractThis paper proposes a broadband metasurface antenna with size‐varying patches. The metasurface radiator is fed by a microstrip line through a coupling slot on the ground. By varying two parameters of the square patches, great mode controllability can be achieved, resulting in wideband and stable gain. Furthermore, the added slotted metal square ring can effectively improve radiation gain. We designed and tested a C‐band wideband antenna consisting of 4 4 novel radiator units. The measured impedance bandwidth and 2‐dB gain bandwidth are 59% (4.3–7.9 GHz) and 44.1% (4.6–7.2 GHz), respectively. The designed antenna has a low profile of 0.09 .

Design of Filtering Coupler Based on Patch Resonator with High Selectivity

In this paper, a new approach for designing a planar high frequency selectivity filtering coupler based on a circular patch resonator is proposed. In order to explain the operating principle, the resonant property of the circular patch resonator has been investigated firstly. Two circular patch resonators connected by two microstrip lines are used in this design. A filtering coupler is achieved by adjusting the feeder position and the length and width of the microstrip line used to connect the two resonators. Without additional circuits, the desired 0° and 180° phase differences are realized by the inherent in-phase and out-of-phase characteristics of E-fields at the TM11 mode. To improve the passband selectivity, transmission zeros are created by introducing a coupling between the source and load through the coupling slots etched on the ground. Finally, a prototype of the filtering coupler centered at 2.12 GHz is designed, implemented, and tested, while the measured results coincide well with simulated ones, verifying the proposed design concept.

A Parallel Folded Dipole Antenna With an Enhanced Bandwidth for 5G Millimeter-Wave Applications

In this communication, a planar folded dipole antenna array with wide operating bandwidth and compact size is proposed for 5G millimeter-wave (mmWave) applications. The basic antenna element is a pair of parallel folded dipoles (PFDs) connected at the terminals. Compared with a single half-wavelength dipole, the PFD can achieve a flatter impedance curve in the working frequency band, and it is easier to achieve broadband impedance matching with 50Ω feeding line. Moreover, a coupling slot feeding method is adopted to feed the proposed antenna element. The capacitance provided by the coupling slot can counteract the inductance caused by the PFD, thus improving the impedance matching at the low frequency band. Benefiting from the innovative design, the proposed antenna element can achieve an ultra-wide impedance bandwidth of 64% and a compact size of 0.26λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.28λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Furthermore, a wide scanning angle with ±50° over wide bandwidth is testified by a 1×8 array using active simulation. For verification, a 4×4 full corporate-fed array is designed based on the proposed element. The measured results prove that the proposed 4×4 array has a -10 dB impedance bandwidth of 65% covering 17 to 33.75 GHz and a peak gain of 17.5 dBi. The measured total efficiency is from 69% to 82% over the working frequency band. With the merits of compact size, wide working bandwidth, and wide beam scanning angle, the proposed antenna is a good candidate for mmWave wireless communications.

A high-gain dual-band shared-aperture array integrating zero-order-resonance patch and higher-order metasurface antenna

This letter proposes a high-gain shared-aperture array for vehicular communications which integrates the hybrid zeroth-order-resonance (ZOR) patch and the higher-order metasurface antenna (MA). In terms of each array element, four hybrid ZOR patches with shorting pins form a metasurface which is fed by slot coupling. Different from some reported designs which have more high-frequency elements than low-frequency ones, the whole array is composed of 4 times 4 hybrid ZOR patches operating in C band (4.74–5.12 GHz) and 2 times 2 MAs working in Ku band (13.0–14.0 GHz). Such a layout brings that the designed array has the benefit to reduce Ku-band loss. Measure results validate the dual-band operation and show that the antenna has its peak gains of 12.7 dBi and 17.2 dBi in these two bands, respectively, which can support vehicle-to-base station and vehicle-to-satellite communications.

A continuous transverse stub array with parabolic reflector for [formula omitted]-band multibeam application

This paper proposes a compact continuous transverse stub (CTS) array that utilizes substrate integrated waveguide (SIW) technology. The CTS array includes six radiation slots and is powered by a novel linear source generator (LSG) with a parabolic reflector located on the bottom layer. The LSG converts the input wave into a planar wave that is subsequently coupled to the parallel-plate waveguide (PPW) of the CTS array through a coupling slot. By utilizing different input ports, the CTS array can produce planar waves in various directions, allowing for the production of beams with different pointing. The CTS array comprises four-layer substrates with a total thickness of only 0.24λ0. The measurement results show that the reflection coefficient of the array is below -10.9 dB in the operating range of 33-37 GHz. The array scanning angle theta can be up to about ±38°at the center frequency of 35 GHz, with a maximum gain of 20.9 dBi. When using the middle port feed, the measurement gain is superior to 20.1dBi and the radiation efficiency is above 87.1% in the 33-37 GHz range. Simulation and measurement results are in agreement, demonstrating that the proposed CTS array is suitable for multibeam applications in the Ka-band.

A Feeding Network With Collinearly Centered Longitudinal Coupling Slots for a Rectangular Parallel-Plate Slot Array Antenna

This paper proposes a novel feeding network with collinearly centered longitudinal coupling slots for uniform excitation of rectangular parallel-plate slot array antennas. Compared to conventional coupling slots arrangement solutions, longitudinal slots along the centerline of the waveguide on the broad wall are employed for minimizing the vibration of field distribution in the parallel plates. Coupling walls are inserted in the waveguide to produce asymmetry for an appropriate excitation of each slot. The arrayed coupling slots are designed by HFSS, manufactured, and tested experimentally. The measured results show a directivity of 37.1dBi and 87.2% aperture efficiency at 9.65GHz with a reflection level less than -16dB. The novel feeding waveguide realizes a significantly 1.2-dB directivity and 21% aperture efficiency enhancement compared to the traditional feed with inclined coupling slots.

Design of Filtering Antenna for 5G FR2 Applications Using Characteristic Mode Analysis

In this paper, a design for filtering antenna based on characteristic mode analysis is proposed, and the proposed antenna works in the 5G FR2 band (n257/n258). The design would adjust the working modes of the radiation structure to realize the filtering response by loading the filtering structures. Meanwhile, the characteristic modes of the feeding structure are analyzed. The feeding structure can introduce a radiation null. The coupling slot and the radiation structure realize two resonant modes to expand the bandwidth but also introduce high-frequency interference mode. The defective ground structure could suppress the interference mode and provide the third resonant mode to further extend bandwidth. To verify the design, the proposed antenna is fabricated and measured. The measured results show that the impedance bandwidth ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$S_{11}$</tex-math></inline-formula> -10 dB) is 19.3% with the peak gain of 8.58 dBi, and the efficiency can reach 87%. The antenna has multiple radiation nulls, and the stop-band suppression level exceeds 28 dB compared to the maximum realized gain. Besides, no additional filtering circuit is introduced in this design.

Simulation study for efficiency optimization of multi-beam klystron output cavity

Increasing klystron tubes’ efficiency is essential in developing new-generation colliders and free-electron lasers. Different factors can affect the efficiency of a multi-beam klystron. One of the significant factors is the electric field symmetry inside cavities, especially in the output section. In this research, two different types of couplers are investigated in the extraction cavity of a 40-beam klystron. The first approach is a single slot coupler, which is frequently utilized and easier to fabricate but disturbs the electric field symmetry inside the extraction cavity. The second method has a more complex structure with symmetric electric fields. In this design, the coupler consists of 28 mini slots on the inner wall of the coaxial extraction cavity. Both designs are evaluated via particle in cell simulations, and the results exhibit around 30% more power extracted from the structure with a symmetric field distribution. The symmetric structures can also decrease the number of back-streamed particles by up to 70%.

Tunable dielectric resonator antenna with circular polarization and wide bandwidth for terahertz applications

In this paper, a tunable wideband circularly polarization (CP) dielectric resonator antenna (DRA) is designed and simulated. The antenna is fed by slot coupling and circular polarization is achieved by the design of the slot configuration and by the excitation of different modes. The tunable response is provided by coating graphene on the top of the radiating dielectric resonator. The proposed antenna provides a wide 10 dB impedance bandwidth of 49% (2.7–4.46 THz) and an overlapped axial ratio bandwidth of 17.34% (2.87–3.43 THz).

A novel wideband dielectric resonator antenna with compact size

ABSTRACT In this paper, a wideband dielectric resonator antenna with compact size is presented. The proposed antenna is formed by four dielectrics. Non-adjacent dielectrics have same permittivity constant. A 50-ohm micro strip feed line is used to exciting the antenna through the coupling slot. By optimizing the dimensions and structure of the antenna, impedance bandwidth of 3.25 to 4.4 GHz is obtained. Impedance bandwidth of the proposed antenna is a very wide bandwidth compared to the previous dielectric antennas. The antenna gain is about 9.6 dB.

Gain-Improved Wideband Circularly Polarized Magnetoelectric Dipole Antenna With Parasitic Helix

This communication presents a magnetoelectric (ME) dipole antenna with wideband circularly polarized (CP) and gain-improved performance. Two pairs of perpendicular sub-ME dipoles which are realized by horizontal and vertical patches constitute the original ME dipole. By connecting one pair of sub-ME dipole with metallic strip, CP operation is achieved at lower band firstly. Then, we change the coupling slot from rectangle to cross which leads to the enhancement of impedance and axial-ratio (AR) bandwidth. Furthermore, a helix with different turn radii and uniform turn spacing is introduced to improve the gain in the whole band. Performance of the proposed design is verified by measured results. The fabricated antenna exhibits an -10-dB impedance bandwidth of 3.33-6.75 GHz, corresponding to 67.9%. Besides, the measured 3-dB AR bandwidth and 3-dB gain bandwidth are 3.6-6.25 GHz (53.8%) and 3.4-5.8 GHz (52.2%), respectively. The proposed design could provide promising application values for wideband wireless communication systems.

Wideband Series-Fed Microstrip Patch Antenna Array With Flat Gain Based on Magnetic Current Feeding Technology

A series-fed microstrip patch antenna array with broad bandwidth and flat gain based on magnetic current feeding structure is presented in this letter. By appropriately blocking the microstrip line, a radiation mode of the microstrip structure is generated, which is equivalent to the magnetic current array. Also, the magnetic current is used to excite the sides-shorted microstrip patch antennas via coupling slots. The broad operation bandwidth of the series-fed array is achieved by merging the fundamental mode generated from the sides-shorted microstrip patch antenna element and the additional radiation mode from the microstrip feeding structure. Moreover, dual radiators are employed in the design to ensure that the gain remains flat. Based on the proposed idea, a 6-element linear array with a center feed is implemented and tested. The results indicate that a wide impedance bandwidth of 9.11–11.84 GHz (26.1%) and a 1 dB gain bandwidth of 9.1–11.5 GHz (23.3%) is achieved, with a maximum gain of 13.95 dBi.

High-Gain Dual-Circularly Polarized Leaky-Wave Antenna for Point-to-Point Communications

In this letter, a high-gain low-profile dual-circularly polarized (CP) leaky-wave antenna (LWA) with fixed beam is presented. The proposed LWA comprises only two-layered substrates, in which the top layer constructs the annular LWA array while the bottom layer realizes the feeding network. To obtain the fixed beam, the differential excitation generated by the proposed coupler is employed. Furthermore, the dual-CP feeding network provides two sequentially rotated phase excitations for the slot coupler, then the dual-CP radiation with fixed beam is realized. The profile height of the proposal is only 0.15 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 28 GHz, while the measured peak gain is up to 27.2 dBic; this could be attractive for point-to-point communications.

W-Band Low-Sidelobe Series-Fed Slot Array Antenna Based on Groove Gap Waveguide

In this letter, a low-sidelobe, high-efficiency, series-fed 2 × 24 slot array antenna at 93 GHz is proposed. The antenna can be divided into three separated layers and there is no need of electric contact between layers according to gap waveguide (GW) theory. To control the magnitude of the coupling energy and achieve −30 dB sidelobe quasi-Taylor weighing in radiation slots, transverse coupling slots in the middle layer are placed in a certain distance relative to the bottom gap waveguide center. Measure results agree well with simulation result, which demonstrates that the reflection coefficient of the antenna is lower than −10 dB from 91.6 to 94.4 GHz, with over 23 dB gain in the operating band. The 3 dB beamwidth of the E-plane pattern is lower than 4°, while the sidelobe level is lower than −20 dB. The whole antenna's efficiency is higher than 85%.

All-metal cavity antenna with light weight, high efficiency and circular polarization for satellite platform applications

In this paper, a lightweight high-efficiency circularly polarized (CP) all-metal antenna design method is presented for satellite industry applications. The proposed antenna is composed of a rectangular waveguide feeder, a high-order mode cavity and a metasurface circular polarizer (MCP). The cavity high-order mode TE440 is directly excited by four coupling slots in the waveguide. The MCP is placed on the cavity to generate the CP radiation. Due to the introduction of high-order mode technology and MCP, all metal walls inside the antenna can be removed, which are necessary in conventional waveguide structures, and weight is thereby significantly reduced. To reflect the weight advantage, a conventional metal wall-loaded waveguide antenna of the same size is designed. The measured results show that the proposed antenna has wider impedance and axial ratio bandwidths, and higher radiation efficiency. In particular, the proposed antenna is 40% lighter than the comparative one, indicating that it is more applicable to satellite platforms with limited loading capacities.