Slot Array Antenna Research Articles

A Synthesized Dual-Polarized Planar Slotted Antenna Array for SAR Sensors

A Synthesized Dual-Polarized Planar Slotted Antenna Array for SAR Sensors

Antenna Array Diversity Evaluation Under Multipath Environments With Digital Beamforming

This work proposes a methodology for evaluating the antenna array diversity and resultant radiation pattern from digitally-processed-based beamforming systems. Our approach enables to interpret the advanced antenna systems (AAS) coverage and massive multiple-input multiple output (mMIMO) spatial resolution, by the inspection of the array resultant multiple beams. Particularly, the impact on the mMIMO spatial resolution is conducted as a function of the channel correlation, by means of an exclusively radiofrequency (RF) approach, with the advantage of not considering the system-level features, and using a new figure of merit (factor). The new figure of merit enables to evaluate the antenna array diversity from two-and three-dimensional (2D and 3D) beamforming, by computing the number of lobes with gain higher than a unique element. In the 3D case, the figure of merit is based on a differential calculation, which enables performing an infinitesimal counting of lobes per antenna element beamwidth. Such parameter is initially applied to a theoretical dipole-based array, with the purpose of quantifying the created multiple beams by the overlapped radiation patterns from mMIMO systems. Furthermore, the factor is exploited for analyzing the performance of a 64-element and dual-polarized SICL-based slot antenna array and a 64-element dipole-based antenna prototypes, both previously developed by our research group. Finally, it is demonstrated that the factor increases as diversity increases and dipole-based antenna array could be used as an upper limit, attaining 11.46 lobes/rad.

Performance analysis of TSA array with elliptical patch

AbstractA compact microstrip to substrate integrated waveguide transition feed tapered slot antenna array (1 × 4) with the elliptical patch is proposed and analyzed. The new approach is presented, employing a parasitic patch in the flared aperture to generate more radiation in the end-fire direction and improve field coupling between the arms. It boosts gain while maintaining overall size and low-frequency performance without using electrically thin dielectric substrates. To validate the designed approach, the proposed structure is fabricated and measured. The measured results show that the array provides impedance bandwidth of 40%, peak measured gain of 9.14 dBi, and radiation efficiency is 90% over the 8.5–12.5 GHz frequency band. A four-way feed network is also fabricated with the insertion loss of −6 ± 0.9 dB; the reflection coefficient is below −15 dB over the desired frequency range and only ±4° phase imbalance. The overall dimension of antenna array is 50 × 54 × 0.813 mm3 or ~1.6λ × 1.8λ × 0.027λ at 10 GHz.

Millimeter-Wave Beam Steerable Slot Array Antenna Using an Inter-Digitated Capacitor Based Corrugated SIW

A new class of electronically beam-steerable corrugated substrate integrated waveguide (CSIW) slot array antenna operating at 26–29 GHz has been developed. The conventional via-based walls of substrate integrated waveguides (SIWs) or stub-based walls of CSIWs have been replaced with an interdigitated capacitor (IDC) structure to enable reconfigurability. This novel IDC-CSIW is shown to have a lower transmission loss compared with conventional CSIWs in the literature. A new mathematical method has been described to calculate the cutoff frequency of IDC-CSIWs. The surface of the IDC-CSIW is then loaded with longitudinal slots, building a leaky-wave architecture. Radiation from individual slots is controlled by shorting the IDC at specific points using p-i-n diodes. The antenna is fed at either end using a single-pole–double-throw (SPDT) switch to achieve a 2-D reconfigurable beam. A compact switched array of two IDC-CSIWs is demonstrated to produce a continuous full sector coverage of 120° in the azimuth plane and ±15° in the elevation plane, providing a 2-D beam steer with a stable gain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 13.5$ </tex-math></inline-formula> dBi and an efficiency greater than 80%.

A Compact and Simply-Constructed All-Metal Circularly Polarized Ridge-Waveguide Slotted Antenna Array for Vehicle Mounted Satcom on the Move (SOTM) Communication Application

In this paper, a novel circularly polarized (CP) ridge-waveguide slotted antenna array is proposed for vehicle used Satcom on the Move (SOTM) applications. The antenna array is designed closely following the required factors for generating the circular polarization. The proposed antenna array is constructed on a symmetrical single-ridge slotted waveguide. Each antenna element consists of a pair of inclined slots opened on the narrow walls, and longitudinal slots opened on the bottom of the U-shaped wall of the waveguide. The inclined slots and the longitudinal slots are able to radiate orthogonal electric-fields independently with a phase-difference of 90°. After a vector superposition in the far-field by using this design, the circular polarization could be realized with extremely low axial ratio theoretically. Several essential parameters affecting the CP performance are also studied in this paper. To verify the feasibility of the proposed approach, a four-element CP antenna array is simulated, fabricated and measured. Results show that the obtained prototype achieves a measured impedance bandwidth of 14.74% from 9.24 GHz to 10.71 GHz with S11 <−10 dB, and a 3-dB axial ratio bandwidth of 19.1% from 9.0 GHz to 10.9 GHz.

Development of a compact transverse slot array antenna using corrugation in groove gap waveguide technology

SummaryWe present the proof of concept of a compact slot array antenna with proper side lobe level in groove gap waveguide (GGW) technology. Four transverse slots are etched at the GGW broad wall along with the nulls of standing TE10 wave existing inside the shorted GGW. To decrease the sidelobes and antenna size, corrugations are applied through the wave path inside the GGW. Proper use of corrugations can reduce the wavelength inside the GGW leading to reduction of the distance between adjacent transverse slots, which can help to suppress the grating lobe problem and consequently enhance the radiation efficiency, which is a challenge in transvers slot array antennas. The designed antenna is optimized to achieve maximum gain, lowest grating lobe level, and return loss at 15 GHz using HFSS simulator. The achieved gain is about 13 dBi, and the SLL is better than 15 dB. To confirm the simulation results, the designed antenna was fabricated and tested. Both simulation and measurement results confirm that the grating lobes are well suppressed at the antenna operating frequency.

A 2D substrate integrated waveguide monopulse slot antenna array with dual‐mode comparator

A double-layer 2D substrate integrated waveguide monopulse slot antenna array is proposed. By adopting the dual-mode monopulse comparators (DMCs), the isolations between ports are significantly improved. The antenna generates “sum” and “difference” patterns in the orthogonal axis with a pair of DMCs. The DMC for azimuth plane tracking and the radiating 4 × 4 slots are located on the top layer, and another DMC is on the bottom layer for the elevation plane tracking and feeds the slot array through two coupling slots. Based on the proposed antenna, an antenna prototype is fabricated. The measured −10 dB shared impedance bandwidth for four ports is 6.18% (9.4–10 GHz) and the isolations between ports are better than 27 dB. The null depths of the difference patterns are lower than −35 dB. The measured results are in good agreement with the simulated results.

A hemispherical near‐field focusing antenna for non‐metallic delamination detection

This paper proposes a novel hemispherical near-field focusing radial line slot array (RLSA) antenna to detect delamination within non-metallic composites. By adjusting the positions and dimensions of the antenna slots, the near-field focusing antenna produced a radiation pattern with a narrow beamwidth and a low side lobe level of the normal component of the electric field. Since the electromagnetic (EM) field of the near-field focusing antenna can be focused on the material under test (MUT), delamination within it will significantly affect the reflected information of the antenna. Simulation and measurement have shown the good focusing characteristics of the novel RLSA antenna, a low side lobe level (−19 dB) and a narrow beamwidth (6 mm) were attained. Taking glass fiber reinforced polymer (GFRP) sheets as MUTs, delamination with different thicknesses are detected using a set of mechanical scanning experimental devices. The results show that delamination as thin as 30 μm can be detected. The proposed near-field focusing antenna can detect thinner delamination inside non-metallic composites at a lower cost and in a simpler way than other microwave non-destructive testing (NDT) methods.

Design of a Low-Cost, Low-Sidelobe-Level, Differential-Fed SIW Slot Array Antenna with Zero Beam Squint

This paper presents a low-cost, low-sidelobe-level, differential-fed, substrate-integrated waveguide (SIW)-based slot array antenna with zero beam squint. The antenna consists of two identical six-way unequal power dividers (PDs) and a 6 × 16 slot array and is realized on a single-layer substrate. The six-way unequal PD provides tapered amplitude and in-phase excitation for six SIWs, and each of them has 16 radiating slots. The 1 × 16 linear slot array on each SIW is excited using a differential feed to avoid undesired beam squinting across its operating band. A two-way hybrid waveguide (WG)-to-SIW E-plane PD is developed to provide equal amplitude and out-of-phase excitation for two six-way unequal power dividers. Moreover, metallic decoupling walls are implemented between two adjacent linear slot arrays to reduce E-plane external mutual coupling. An antenna prototype is fabricated and experimentally verified. The fabricated antenna shows that the measured −10 dB reflection bandwidth is 7.15% (9.57–10.28 GHz), with the achieved gain ranging from 20.30 to 21.92 dBi. A stable boresight beam is observed over the entire operating band. Furthermore, at the designed frequency of 10 GHz, peak SLLs of −29.1 dB and −29.4 dB are achieved in the E- and H-plane, respectively.

An efficient technique to realize low‐profile dual‐band multi‐polarized shared‐aperture slot antenna array

An efficient technique to realize dual-band multi-polarized shared-aperture slot antenna array is proposed in this paper, featuring in all-metal, low-profile, light-weight and high radiation efficiency. The cavity-backed longitudinal slots are used at L-band for vertical polarization, while horizontal and vertical polarizations are both achieved at C-band, by utilizing interleaved ridged waveguides with two different kinds of slots. A coaxial-feed end-grounded metallic bridge is developed to excite the L-band cavity-backed slots, so the volume and weight of the L-band cavity can be obviously reduced. To further make the whole antenna structure compact and tight, the reduced L-band cavity is embedded into the serration, surrounding by two adjacent C-band ridged waveguides for vertical polarization and one for horizontal polarization. An array prototype, which consists of two L-band single-polarized antennas and four pairs of C-band dual-polarized antennas, is fabricated and measured. Experimental results are well consistent with the simulated ones, showing a satisfying impedance bandwidth of 12% in L-band and 5.5% in C-band, and besides high radiation efficiency above 85% for both bands. The all-metallic structure of this proposed array provides the thermal and mechanical advantages for space-borne synthetic aperture radar (SAR) application.

Dual circular polarization 2 × 2 slot array antenna based on printed ridge gap waveguide technology in Ka band

In this paper a novel multi-layer slot array antenna based on printed ridge gap waveguide (PRGW) technology with dual circular polarization (CP) at Ka band is proposed. This antenna consists of five layers, two dielectric substrates as a transition from PRGW to coax line and a branch line coupler (BLC) as an antenna feeding network, and three metal layers as a coupling slot, 2 × 2-element slot array antenna and ground layer. Feeding network has two individual ports consists of a BLC that based on PRGW implemented. The operating frequency band of the antenna for S11 < −10 dB with the gain more than 11.5 dBi is 27–29 GHz which covers the 27.5–28.35 GHz band proposed by Federal Communications Commission (FCC) and can be a suitable antenna for 5G applications at this frequency band. Total aperture size of the array antenna is less than 1.15 × 1.15 λ2 at 28 GHz and total efficiency of it is better than 80 %. Two individual ports of the proposed antenna provide two isolated left- and right-hand CP with axial ratio (AR) less than 2 dB for each port in aforementioned frequency range, and the measured results indicated that the antenna can provide isolation more than 15 dB between two input ports.

A broadband single-layer substrate integrated waveguide cavity-backed slot array antenna with improved gain

ABSTRACT A single-layer substrate-integrated waveguide (SIW) cavity-backed slot array antenna with broad impedance bandwidth and improved gain is presented in this paper. In the element design, a multi-branch slot and a pair of inclined slots are designed on the top layer of the SIW as radiating structure and the grounded coplanar waveguide feeding structure are used for impedance matching, which ensures that the triple special resonant modes with the odd TE120 mode, the half TE120 mode, and a hybrid mode can be excited successfully to obtain broad impedance bandwidth and high gain, because of its low order and adjacent working frequencies points. Following this, an array antenna consisting of four elements and a four-way microstrip feeding network using only single-layer substrate structure is simulated and fabricated. The measured impedance bandwidth of the four-element array antenna achieves up to 34.4% and the measure peak gain at desired frequency band is 14.4 dBi with an aperture efficiency of 71.1%. The measured results prove that the proposed design has advantages of simple structure, broadband, and high gain, which is expected to be applied in high-speed vehicular communication system.

Wideband and High Cross-Polarization Discrimination 45° Linearly Polarized Slot Array Antenna Without Cavity-Backed Layer

This letter presents a wideband and high cross-polarization discrimination (XPD) 8×8-slot full corporate- feed 45° linearly polarized slot array antenna. A new vertical 1-to-4 power divider consisting of one H-plane T-junction and two E-plane T-junctions is employed to replace the 1-to-4 cavity-backed power divider in the conventional designs, which balances the amplitude and phase distributions among the output ports. By further bending the output ports of the 1-to-4 power dividers upward 90° along the diagonal plane, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode in the signal path is smoothly shifted along the intended E- and H- planes and directly excites the 45° tilted radiation slots. Combined these features, the grating lobe suppression and XPD improvement over a wide frequency band can be achieved without introducing additional metal structures. For demonstration, a prototype covering 24–33 GHz is implemented. The experimental results are in good agreement with the simulation ones, which verifies the design concept.

Wideband Dual-Polarized Hollow-Waveguide Slot Array Antenna

A wideband dual-polarized slot array antenna based on hollow waveguide (HW) is presented in this article. Its wide bandwidth and high performance are enabled by two separate feeding networks, from the side and the bottom, using square coaxial line and ridge waveguide structures, respectively. The full-corporate-feed networks excite the radiation slots in a one-to-one fashion without using backed cavities. Tight element spacing is made possible, suppressing the grating lobe and maintaining high cross-polarization discrimination (XPD) across the wideband. This resolves a usual tradeoff between bandwidth and grating lobe. A double-ridge rectangular waveguide cavity is devised as an orthogonal mode splitter for isolation enhancement. Several design features are used to minimize the signal path length and facilitate routing. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> element prototype in K-band is designed, fabricated, and measured. Experimental results show that the antenna has a wide bandwidth of 23.4% (from 17 to 21.5 GHz) free from grating lobes. More than 25.5 dBi peak gain higher than 51.2 dB isolation and over 43.6 dB XPD are also obtained for the dual polarizations.

Dual‐band shared‐aperture antenna with high aperture reuse ratio and high isolation

This work presents a dual-band (3.5/26 GHz) shared-aperture antenna with high aperture reuse ratio and high isolation. The proposed 26-GHz 4 × 4 substrate integrated waveguide (SIW) cavity-backed slot array antenna consists of four hybrid TE130–TE310-mode SIW cavities, which can simplify the design of feeding network. The radiating slots are unequally offset and inductance windows are added for good impedance matching. The entire structure of the 4 × 4 slot array antenna also functions as an equivalent TM10-mode patch antenna at 3.5 GHz. The resonant frequency of the patch is fine-tuned by inserting an air gap instead of enlarging the patch length, thus ensuring high aperture reuse ratio. To enhance channel isolation, the patch is designed with a bandpass filtering response centered at 3.5 GHz by introducing a stub-loaded resonator feeding structure. For demonstration, a prototype of the proposed dual-band antenna was fabricated and measured. The measured results show that the proposed antenna achieves excellent dual-band performance, and its aperture reuse ratio and channel isolation are as high as 87.5% and 62 dB, respectively.

An UHF to L band dual‐polarized wide‐angle scanning tapered slot phased array with tightly coupled structure

This article presents a novel dual-polarized tightly coupled tapered slot antenna (TC-TLA) array. With increased capacitive coupling effects of U-shaped metallic channels of adjacent flare-arms of TLA elements, the operational bandwidth for broadside scan increases from 4.4:1 to 5.7:1, and the bandwidth at a 50° scan increases from 3.1:1 to 5.7:1, compared with the conventional TLA array. The proposed TC-TLA array delivers over 0.35–2 GHz bandwidth, ±50° scanning coverage in the horizontal plane with an active VSWR < 3.5, and <−20 dB cross-polarization. Prototype for a 4 × 22 dual-polarized TC-TLA array fed by 1 to 4 wide-band power dividers is fabricated and measured. Good agreement is achieved between numerical and measured results.

Electrothermal Design of SIW Slot Antenna Array With Fin-Shaped Heatsink Enclosed

In this article, an electrothermal co-design of substrate integrated waveguide (SIW) slot antenna array combined with fin-shaped heatsink is proposed. The antenna array is constructed by 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times8$ </tex-math></inline-formula> SIW slot elements. The heatsink structure above the antenna array not only improves the radiation performance of the antenna array but also enhances the electromagnetic compatibility (EMC) and the heat dissipation capability of the whole structure. The measured realized gains over the operating frequency range increase from 15.4–18.1 to 16.1–19.7 dBi when the heatsink is mounted on the antenna array. Meanwhile, the enclosed heatsink reduces the hotspot temperature rise of the system by 57%. The measured results are in good agreement with the simulated ones.

W-Band Binary Phase-Controlled Multibeam Antenna Array Based on Gap Waveguide Magic-Tee

In this article, a compact 94 GHz multibeam antenna array based on the binary phase-controlled concept is proposed. The feeding network is composed of four unconnected layers, and the ridge or groove gap waveguides are adopted as the guided wave structures. A key planar gap waveguide Magic-Tee is designed to obtain 0° and 180° phase states and then integrates with an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\,\times \,8$ </tex-math></inline-formula> slot antenna array to achieve multibeam operation for the first time. Compared with the traditional phased array and passive beamforming networks (BFNs), the feeding design is simple in construction, consisting of only Magic-Tees and cascaded power dividers without any phase shifters. Benefiting from the gap waveguide technology, the antenna array does not require electrical contact among the metal layers, so it is simple and low cost to manufacture. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times8$ </tex-math></inline-formula> slot antenna array can easily switch among one-beam and three different dual-beam states that point to ±7°, ±17°, and ±38°. The measurement results of 6.6% bandwidth from 91.7 to 98 GHz for both reflection coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt; -10$ </tex-math></inline-formula> dB and isolations >25 dB are achieved. The proposed multibeam antenna array would be an attractive candidate for millimeter-wave multiuser communication where it requires multiple beams simultaneously.

Planar High-Gain Millimeter-Wave Slotted SIW Cavity Antenna Array with Low Sidelobe and Grating Lobe Levels

In this paper, a planar high-gain millimeter-wave (mmW) slotted substrate integrated waveguide (SIW) cavity antenna array with low sidelobe and grating lobe levels is proposed. The antenna consists of a slotted SIW resonator and an SIW transmission line (TL). To achieve a high gain and simplify the structure of the antenna element, the slotted SIW cavity is resonated in high-order mode. Then, a high-gain antenna array is implemented with only four such elements. By analyzing the pattern multiplication principle of the antenna array and accurately adjusting the element spacing, the high grating lobe level caused by the large spacing of the high-order mode resonator is considerably reduced. In addition, a one-four unequal amplitude power divider is introduced to further reduce the antenna array’s sidelobe levels (SLLs). Finally, the proposed antenna array is fabricated for verification. The measured peak gain is 21.4 dBi at 27.3 GHz. The measured grating lobe level in the E-plane is reduced to −17.9 dB, and the measured SLLs are lower than −19.1 dB.

Slotted Antenna Array with Enhanced Radiation Characteristics for 5G 28 GHz Communications

This paper presents a 1 × 4 linear antenna array working at 28 GHz for 5G communication systems. The proposed array employs four rectangular slotted antenna elements fed by a 1 × 4 T-power divider. An artificial magnetic conductor (AMC) layer is placed below the array for increasing the radiation intensity and improving overall array gain. The measured impedance bandwidth of the proposed array with (|S11| &lt; −10 dB) is extended from 25.36 to 26.03 GHz (with a bandwidth of 0.67 GHz) and from 26.75 to 28.81 GHz (with a bandwidth of 2.06 GHz). The proposed array design exhibits a measured gain value that varies between 11.8 dBi and 13.1 dBi within the operating bands and reaches 13.1 dBi at 28 GHz. The proposed array achieves a radiation efficiency of 83.05%, and a front-to-back ratio ranging between 15 and 20 dB across the operating frequency band. The array is fabricated and tested with good matching between the simulated and tested outcomes. The improved performance of the array makes it a suitable candidate for 5G new radio (NR) communications.