Slot Array Antenna Research Articles

Ridge gap waveguide antenna array with improved mutual isolation for millimeter wave applications

Fifth-generation millimeter-wave devices with multiple antennas require minimal mutual interference for better overall performance. This article presents a simple but novel technique to improve the isolation between closely packed slot antenna arrays. A printed ridge gap waveguide (PRGW) structure is used to realize a low loss millimeter-wave array's feeding mechanism. By optimally introducing a defective upper plate within the PRGW structure, the measured port isolation of the antenna elements is improved by 17 dB at 61.3 GHz. The antenna array is impedance matched to the feeding PRGW structure over a wide frequency range of 54–67 GHz. Moreover, the radiation patterns are consistent showing broadside radiation before and after introducing the defect in the PRGW structure. The fabricated prototype of the PRGW fed slot antenna array validated the predicted isolation and return-loss bandwidths of the proposed radiating system.

Circularly‐polarized cavity‐backed slot antenna array with simplified feeding structure

A class of circularly-polarized cavity-backed slot antenna arrays with simplified feeding structure are proposed. Power dividing network is an essential feeding structure for the design of conventional antenna arrays, which results in complicated antenna structure. A novel feeding technique based on the electric field of cavity modes is introduced to feed the array elements. The slots on the top wall are directly fed by the electric field without additional feeding structure. Crossed slots with different lengths are introduced to achieve the self-phased CP radiation as they produce different perturbation on the two degenerate cavity modes. Therefore, high efficiency and simple antenna structure of the CP slot antenna array are achieved. Then, two CP slot arrays with 3 × 3 and 8 × 8 elements are presented to show the designed feasibility. Finally, the 3 × 3 CP antenna array is fabricated and measured to validate the design concept, which can achieve 12.6 dBic gain, 94% total efficiency, 80% aperture efficiency, and −25 dB cross polarization.

Development of a wideband hexagonal SIW cavity-backed slot antenna array

In this paper a novel wideband hexagonal cavity-backed slot antenna array using two sots including Resonant Narrow Slot (RNS) and Non-Resonant Wide Slots (NRWS) based on Substrate Integrated Waveguide (SIW) is proposed. First, a single element low profile wideband linearly polarized cavity-backed antenna using two slots is designed and analyzed. The antenna bandwidth is increased by NRWS, which makes both hybrid modes of TM110 and TM210 close to each other to be excited. Then, to improve antenna gain, an array of two elements cavity-backed slot including is designed and investigated. Moreover, in order to match the input impedance over the operating bandwidth, a special power divider using tapered line is introduced. The proposed single element and antenna array is made and successfully tested. The simulation and measurement results are in a good agreement for both single and antenna array. The measured gain and impedance bandwidth are 12 dBi and 14% respectively for the designed array.

Monopulse Radial Line Slot Array Antenna Fed by a 3-D-Printed Cavity-Ended Modified Butler Matrix Based on Gap Waveguide at 94 GHz

This article presents the design and fabrication of a monopulse radial line slot array (RLSA) antenna excited with a circular cavity connected to a modified Butler matrix at 94 GHz. The antenna consists of two pieces: the RLSA antenna implemented over a low loss dielectric substrate and a 3-D-printed Butler matrix based on gap waveguide. The interface between both parts is a circular cavity that couples two different modes into the RLSA through a coupling slot in the dielectric substrate. The coupled mode depends on the input excitation of the Butler matrix for the generation of simultaneous sum and difference radiation patterns. This interface is deeply detailed in this article, together with the design of the RLSA antenna and the integration of the full monopulse antenna. The measured S-parameters fit very well with simulations. The operation is inherently narrowband with a realized gain of 27.8 dBi at 94 GHz, a radiation efficiency of 70%, 0.3 dB axial ratio, and a maximum null relation between sum and difference patterns higher than 50 dB.

Guard lines conformal slotted antenna array for multiband application

<span>This work investigated a miniaturized slotted conformal antenna array for multiband application. Three guard lines are incorporated to the side of main patch and top of main patch to reduce surface current for planner surface and observe the effect of guard line due to which it resonate at three frequencies in X band and Ku band to be useful for multiband. A rectangular slot is etched at center of patches to increase the current path for wide band application. A quarter wavelength feeding network is used with good agreement of impedance matching. The main lobe width and direction shows through the radiation pattern which remains stable even it is significantly curved. This structure is wrapped around a cylinder with a diameter of 41.4 mm in the circumferential direction. It is observed that the planner antenna array operating at 8.4 GHz, 11.2 GHz &18.2 GHz with a return loss of -20 dB to -45 dB with fractional BW of 25% at 3rd frequency range and the directivity from 3.4 dBi-6.8 dBi. By doing some alteration in dimensions for the conformal antenna producing fractional BW of 20% and the directivity 5.5 to 9.1 dBi at resonating frequencies of 8.4 GHz, 11.4 GHz, and 17.5 GHz. This proposed array is simulated on CST software.</span>

28 GHz dual‐layer substrate integrated waveguide slot array antenna combined with quad‐polarization

This article presents a compact slot array antenna combined with quad-polarization for mm-wave applications. A novel modified short-circuit termination with inclined slot is proposed in this paper and a dual-layer structure has been adopted to achieve miniaturization and also to design a circular polarization feeding network. Two linear polarization feeding networks are designed independently so that four polarization states can be realized. Four polarization states, namely vertical linear polarization, horizontal linear polarization, left hand circular polarization (LHCP), and right hand circular polarization (RHCP) can be switched by feeding corresponding ports. Judging from impedance matching and axial ratio (AR), the antenna exhibits wide bandwidth. The −10 dB impedance bandwidth and 3 dB AR bandwidth are better than 14.2% (26-30 GHz) with gain about 5-8 dBic for both LHCP and RHCP. The linear polarization states have |S11| < −10 dB and a gain of 5-7 dBi over 26.5-29.5 GHz (10.7%). The size of the slot array antenna is 65 × 65 × 1.156 mm and measured results are consistent with simulations.

Wideband cavity‐backed slot array with high gain and high aperture efficiency

In this article, a wideband cavity-backed slot array antenna with high gain and high aperture efficiency is presented. A novel cavity-backed subarray is designed with compact size and applied to construct a 4 × 8 array. The array antenna is composed of two feeding layers and a radiating layer. The subarrays are placed on the top layer and SIW structure feeding network on the two layers below is used to feed them. The presented antenna is designed, fabricated and measured. The measured results reveal that the working bandwidth reaches up to 17.6%, ranging from 18.7 to 22.3 GHz with the peak gain of 19.5 dBi. Besides, the maximum aperture efficiency of 77.6% is calculated by employing measured gain and aperture size at 21.9 GHz. The presented array can be utilized as a receiving antenna in satellite communication systems.

Wideband Slot Array Antenna Fed by Gap Waveguide with Right-Handed Circular Polarization and High Gain

A wideband and high-gain circularly polarized (CP) 16 × 16 array antenna based on gap waveguide technology is presented for millimeter-wave applications at 28 GHz frequency range. Four cavity-backed slots with linear polarized (LP) radiation are used as the subarray. CP is obtained by a 4 × 4 sequential feeding network which is also expanded to achieve high gain. The feeding network of the final array antenna consists of two layers based on the ridge gap waveguide (RGW), and it has four unconnected metal layers. It is shown by simulation that the proposed antenna has 20.5% impedance bandwidth over 25.8–31.7 GHz and 3 dB axial ratio bandwidth near 10% over 27.2–30 GHz. In addition, the maximum gain value for this antenna is 31.6 dBi at a frequency of 29 GHz, which shows good performance compared to other structures.

Compact Slotted Waveguide Antenna Array Using Staircase Model of Tapered Dielectric-Inset Guide for Shipboard Marine Radar.

This paper presents a new configuration of a slotted waveguide antenna (SWA) array aimed at the X-band within the desired band of 9.38~9.44 GHz for shipboard marine radars. The SWA array, which typically consists of a slotted waveguide, a polarizing filter, and a metal reflector, is widely employed in marine radar applications. Nonetheless, conventional slot array designs are weighty, mechanically complex, and geometrically large to obtain high performances, such as gain. These features of the conventional SWA are undesirable for the shipboard marine radar, where the antenna rotates at high angular speed for the beam scanning mechanism. The proposed SWA array herein reduces the conventional design’s size by 62% using a tapered dielectric-inset guide structure. It shows high gain performance (up to 30 dB) and obtains improvements in radiation efficiency (up to 80% in the numerical simulations) and weight due to the use of loss and low-density dielectric material.

Quad Sector HMSIW Tapered Slot Antenna Array for Millimeter-Wave Applications

In this paper, a slot antenna array based on a half-mode substrate integrated waveguide (HMSIW) is presented, integrating a series of linearly tapered slots for wireless broadband applications in millimeter-wave frequencies. The slots are etched on the upper layer of HMSIW, which radiates the energy from the open side of HMSIW, exhibiting a near broadside radiation pattern. Two identical sets of back-to-back printed antenna arrays are cross-lap joined to form a quad sector antenna providing 360° coverage. The proposed antenna occupies a volume of 20 × 20 × 70 mm3. The measured bandwidth is 1.81 GHz (6.53%) for Voltage to Standing Wave Ratio (VSWR) 3:1 from 26.8 to 28.6 GHz, while the peak measured gain and efficiency of single antenna array were 14.2 dB and 71.3%, respectively, at 27.5 GHz. Furthermore, the sidelobe level in the azimuth plane was observed to be 17.75 dB. The performance of the proposed antenna is measured, and a good agreement between simulation and measured results is observed over the frequency range of 27.5–28.35 GHz for millimeter-wave 5G applications.

A 5 × 8 Butler Matrix Based on Substrate Integrated Waveguide Technology for Millimeter-Wave Multibeam Application

A 5 × 8 Butler matrix (BM) operating in the millimeter-wave band is presented in this letter. The matrix is extended from two 3 × 4 Butler matrices by adding two couplers and one power divider, providing an equal amplitude signal distribution with five phase differences between the adjacent output port (0°, ±45°, ±135°). In order to reduce the number of crossover and complexity of the matrix structure, a dual-layer and symmetrical substrate integrated waveguide (SIW) structure is used to design the proposed BM. To verify the concept, an experimental BM is designed and fabricated as the feeding network of a slot antenna array, achieving five beams in the frequency range of 27.8-30.8 GHz.

A Survey: Slot Antenna and Antenna Array.

Slots are generally introduced in the antenna or antenna to improve the impedance matching, improve the bandwidth, and gain. Sometimes slots are introduced in the ground planes, or between antenna elements to reduce the mutual coupling between elements. The antenna being an important element in wireless communication technology, the design of the same with different requirements is important. This paper gives the survey of the slot antenna and antenna array constructed through waveguide and microstrip lines, to meet different antenna parameters as required in various wireless communication technology.

3D-Printed frequency-scanned slot array in grating waveguide

In this work, a linearly-polarized frequency-scanned slot-antenna linear array fed by a travelling wave in grating waveguide is designed at 17 GHz. Additionally, the insertion of periodic gratings in the bottom broad-wall of the feeding waveguide reduces the guided wavelength of the fundamental propagating mode. Therefore, steering angles around broadside can be attained in the radiation pattern, contrary to conventional travelling-wave designs where grating lobes would inevitably appear. Furthermore, tuning posts are included in the radiating element design to mitigate the mismatch provoked by uniform phase feeding. A 16-element array is fabricated to validate the design, which experimentally shows a continuous angular scanning range of ±10°around broadside in the band from 16 to 18 GHz, with a peak gain of 18 dBi and a maximum gain drop of 4 dB.

Donut-Shaped mmWave Printed Antenna Array for 5G Technology

This article presents compact and novel shape ring slotted antenna array operating at mmWave band on central frequency of 28 GHz. The proposed structure designed at 0.256 mm thin Roggers 5880 is composed of a ring shape patch with a square slot etched at the top mid-section of partial ground plane. Through optimizing the ring and square slot parameters high bandwidth of 8 GHz is achieved ranging from 26 to 32 GHz with simulated gain of 3.95 dBi and total efficiency of 96% for single element. The proposed structure is further transformed in a 4 element linear array manner. With compact dimensions of 20 mm × 22 mm for array, the proposed antenna delivers high simulated gain of 10.7 dBi and is designed in such a way that it exhibits dual beam response over the entire band of interest and simulated results well agree with fabricated prototype measurements.

Optically controlled THz power tuning based on interference at transmission line.

We have proposed an optically controlled THz power tuning method based on THz wave interference. Through interfered THz waves at the T-junction transmission line, adjustment of the THz power is achieved, and tuning control is attained by varying the optical time delay of the beat-note lightwaves. To demonstrate and verify THz power tuning with an optical delay line, we have also fabricated a monolithic chip on an InP substrate, which integrates arrayed uni-traveling-carrier photodiodes and a planar slot antenna array for 300GHz wave generation. The experimental results reveal that the power transmission of this THz power tuner can be continuously adjusted with a wider tuning range than 7 dB at 300 GHz band. It should be a promising solution for the integration of compact THz wave planar photonic circuits.

Design of Compact Transverse Slot Array Antenna Using Corrugated H plane Horn

Design of Compact Transverse Slot Array Antenna Using Corrugated H plane Horn

High-Order Modes Analysis and Its Applications to Dual-Band Dual-Polarized Filtering Cavity Slot Arrays

In this article, a series of filtering cavity slot arrays using high-order modes are investigated. It is found that each unit of the cavity slot arrays in the proposed high-order mode resonator is in phase with the same amplitude, which helps enhance the antenna gain and reduce the sidelobe level. Meanwhile, the filtering function is integrated into the design for frequency selectivity and harmonic mode suppression. The higher order response can be achieved by cascading more high-order mode resonators with required external quality factor ( Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> ) and coupling coefficient ( K). The fractional bandwidth (FBW) and out-of-band suppression of proposed designs are also discussed. For proof-of-concept, a single-band third-order 4×5 filtering cavity slot array using a TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">450</sub> mode resonator and a dual-band dual-polarized third-order 4×3 filtering cavity slot array, using TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">430</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">340</sub> mode resonators, are fabricated and tested. The good agreement between the simulated and measured results verifies that the proposed design methodology is feasible for designing high-order mode filtering cavity slot array antennas.

A DESIGN SOLUTION FOR COMPACT SLOTTED WAVEGUIDE ARRAY ANTENNAS BASED ON SIW TECHNOLOGY

Slotted waveguide array antenna is a crucial structure in microwave frequency antennas with many applications in radar and communications systems. Previously, slotted waveguide array antenna systems mainly used metal materials. The study of slotted array antenna based on the waveguided with SIW (Substrate Integrated Waveguide) technology is a novel approach. The paper presents the results of researching, designing, and manufacturing waveguide slot array antenna with low SLL using SIW technology in X-band. The results will be an essential basis for selecting a design solution for slotted waveguide array antenna by SIW technology to replace traditional metal slot array antennas in practical applications in X band radar antenna systems.

Wideband Dual-Layer Huygens’ Metasurface for High-Gain Multibeam Array Antennas

A wideband dual-layer Huygens’ unit cell based on offset electric dipole pair (OEDP) is proposed. Different from traditional designs with a combination of electric and magnetic polarizabilities, the proposed Huygens’ unit cell exclusively employs electric polarizabilities. By doing so, it practically avoids the unbalanced resonant frequencies between the two polarizabilities, thereby achieving wideband transmission. Based on the proposed unit cell, a wideband and high-gain multibeam array antenna is developed. First, a Rotman lens is designed by using a substrate-integrated waveguide (SIW) technology. Then a parallel-fed slot antenna array is connected to the Rotman lens to generate multiple beams. Without using a series-fed slot antenna array, the multibeam array antenna based on Rotman lens can operate within a relatively wide bandwidth (28–32 GHz). Second, a wideband dual-layer Huygens’ metasurface is developed that serves as a superstrate of the multibeam array antenna for increasing the antenna gain further. A wideband and high-gain multibeam array antenna is finally realized, which is comprised of a Rotman lens, a parallel-fed slot antenna array, and a Huygens’ metasurface. To verify the performance of this design, a prototype is fabricated and its measured results are compared to the simulated counterparts.

Ultra-Wideband, Compact, and High-Gain Two-Port Antenna System for Full-Duplex Applications

A broadband, dual-polarized, and common-aperture <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> cavity-backed slot antenna (CBSA) array for enabling full-duplex wireless communication is presented. The antenna consists of a thin rectangular cavity appropriately loaded with metallic septa to excite multiple resonances of similar desired field distribution to achieve consistent radiation characteristics over a wide bandwidth. Four pairs of concentric orthogonal radiating slots are cut out on one of the broad walls of the cavity all of which are fed by two concentric orthogonal slots on the opposite broad wall of the cavity. The cavity is fed by an end-launch coaxial-to-waveguide transition to excite one of the channels. The other channel is excited by a two-pronged microstrip line symmetrically crossing over the other cavity feeding slot. Due to the out-of-phase coupling from the two prongs of the microstrip line to the other port, this type of excitation is shown to provide an unprecedented level of isolation between the two channels over a wide bandwidth. To achieve a high-efficiency and fabrication accuracy of this complex architecture, the antenna is 3-D printed out of HP PA12 Nylon and is then metalized by the silver spraying technology. The fabricated antenna provides a minimum of 55 dB of isolation and 8 dB of return loss over 44% fractional bandwidth from 4.8 to 7.5 GHz. Keeping its size smaller than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.3 \lambda _{L} \times 1.3\lambda _{L} \times 0.27\lambda L$ </tex-math></inline-formula> (where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{L}$ </tex-math></inline-formula> is the free space wavelength at the lowest frequency), and its weight less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$70g$ </tex-math></inline-formula> , the antenna provides a minimum gain of 10 dB for both polarizations and exhibits more than 20 dB polarization discrimination within the main beam over the entire band.