Groove Gap Waveguide Research Articles

A New Wide Band and Compact H-Plane Horn Antenna Based on Groove Gap Waveguide Technology

In this article, a new H-plane horn antenna is designed using gap waveguide (GW) technology. This antenna consists of a semicircular groove GW (GGW) partially filled by a dielectric to provide uniform field distribution across the antenna aperture in a very compact range. In the proposed structure, the antenna aperture is loaded by an elliptical dielectric which collimates the antenna beam in E-plane resulting in gain enhancement. The designed antenna shows proper radiation performance in both E- and H-planes with low sidelobe levels (SLLs). A sample antenna is designed and simulated for Ku band and a prototype is fabricated. For the designed antenna, 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">$S_{11} &lt; -10$ </tex-math></inline-formula> dB) of 49% covering the whole Ku-band is obtained. Likewise, the obtained SSL and gain are −10 dB and 14–17 dBi, respectively, over the operating bandwidth. In comparison with state-of-the-art designs, the proposed antenna introduces higher gain with lower size.

High Dynamic Range Microwave Displacement and Rotation Sensors Based on the Phase of Transmission in Groove Gap Waveguide Technology

This research is focused on the design and realization of displacement sensors in gap waveguide technology. It is shown that with a small but fundamental change in the structure of a conventional gap waveguide, a linear displacement can be sensed. To this end, a unique feature of gap waveguides, i.e. the fact that no electrical connection between the top and bottom parts of the gap waveguide is required, is used. It is further shown that the concept can be also used for the development of rotation sensors. To validate the proposed concept linear and angular displacement sensors are designed and simulated. A prototype of the proposed linear displacement sensor is fabricated for demonstration. Agreement between the computed and measured results validates the concept.

Design of Millimeter-Wave Circularly Polarized Endfire Antenna and Multibeam Antenna Array for Wireless Applications

A broadband stepped tapered slots’ endfire circularly polarized (CP) antenna and a multibeam antenna array are proposed for millimeter-wave (mmWave) applications. First, a modified tapered slot endfire antenna element is designed. Compared with the normal antipodal linearly tapered slot (ALTSA) endfire antenna, the performance of the stepped tapered slots’ antenna shows remarkable improvement, and the size of the antenna reduces effectively. The simulation and measurement results of the proposed endfire antenna show that an impedance bandwidth of 63.5% (75.1–145 GHz), an AR < 3 dB bandwidth of 50% (75.9–125.3 GHz), and a max gain of 8.8 dBic are realized, respectively. Second, to reduce fabrication and assembly requirements, a groove gap waveguide (GWG) feeding network is designed for multibeam array applications. The broadband 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 GWG network, interconnections, and transitions are designed and applied in the antenna array. Finally, a multibeam array based on the proposed endfire antenna is designed, fabricated, and measured. An impedance bandwidth up to 37.7% and a wide axial ratio bandwidth of 38.7% with a max LHCP gain of 12.8 dBic are achieved by the proposed 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 2 multibeam antenna array. The proposed multibeam endfire CP antenna array would be an attractive candidate for mmWave wireless applications.

Shaped Parallel-Plate Lens for Mechanical Wide-Angle Beam Steering

This article presents a parallel-plate lens beamformer for continuous wide-angle scanning. The design is based on a compact dual-lens system with extended scanning range and is optimized using a previously developed geometrical optics technique. Beam steering is accomplished with a mechanical feed system based on the noncontact characteristic of groove gap waveguides, offering large bandwidth, low profile, and mechanical ruggedness. The proposed concept is validated by an all-metal prototype of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20.5\lambda $ </tex-math></inline-formula> lens operating in the uplink Ka-band allocated to satellite communications (27.5–31 GHz). Good agreement is obtained between the simulated and measured performances. The measured return loss is greater than 12 dB over the entire frequency band and beyond. High scanning performances are achieved over an angular range of ±50° (±14 beamwidths), with maximum scan losses in the order of 3 dB and good pattern stability over the entire band. The proposed solution is particularly suited for next-generation satellite terminals requiring compact broadband antennas with continuous beam-steering capability over a large angular range.

Design of a Compact and Low-Loss E-Band Filter Based on Multilayer Groove Gap Waveguide

This letter presents our study on a compact and low-loss E-band bandpass filter (BPF) based on multilayer groove gap waveguide (GGW). Different from other reported planar GGW filters and vertically stacked substrate integrated waveguide (SIW) filters, the proposed filter realizes a cross-coupled quadruplet topology by introducing a pair of unique circular capacitive holes across layers, innovative ridges (capacitive iris), and conventional inductive irises on the same layer, which reduces the insertion loss (IL) while having a smaller size. By tuning the dimensions of the coupling structures and cavities, the filter is optimized to exhibit a superior performance in simulation. The designed filter is fabricated using CNC machining and verified in experiment. The measured results agree with the simulated ones quite well, showing an average IL of 0.45 dB and an 8% relative 3-dB bandwidth at a center frequency of 73.65 GHz. Therefore, the proposed multilayer GGW structure opens a new avenue in designing high-performance filters in millimeter-wave bands.

Millimeter-Wave Three-Dimensional Substrate-Integrated OMT-Fed Horn Antenna Using Vertical and Planar Groove Gap Waveguides

A three-dimensional (3-D) substrate integration method by using both the planar dimensions and the vertical dimensions in multilayered substrates for millimeter-wave devices and circuits design is presented in this article. The vertical substrate-integrated groove gap waveguide (SIGGW) is studied first, whose multilayered geometry without metal contact between stacked substrates and wide operating band supporting the single quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode with stable propagation features enables it to be a promising vertical waveguide structure with ease of realization. By simultaneously utilizing the vertical and planar SIGGWs, a fully 3-D substrate-integrated orthomode transducer (OMT) consisting of E-plane power dividers, U-shaped connections, and a turnstile junction that are difficult to fulfill in previous works is successfully implemented in the Ka-band. Its compact geometry and significantly performance improvement demonstrate the merits of the proposed method. After that, the OMT is used for feeding a dual-polarized pyramidal horn antenna also with a 3-D substrate-integrated configuration. The overall multilayered antenna module with experimentally confirmed wide bandwidths, high isolations, and stable radiation patterns can still be fabricated conveniently by employing the standard single-layered printed circuit board (PCB) facilities. Taking the advantages of the flexible design freedom and satisfying operating characteristics, the presented design method and devices are valuable to advanced millimeter-wave applications.

Wideband Rotary Joint Based on Gap Waveguide Technology

This article presents a wideband design of a rotary joint based on groove gap waveguide technology. The proposed design includes two coax-to-groove gap waveguide (GGW) transitions, connected together in a back-to-back arrangement. As the gap waveguide structure does not require electrical connections between different parts, the rotor part is placed on top of the stator with an air gap distance while the wave leakage is suppressed. Therefore, the rotating choke, which is a critical and bulky part in the previous designs, is eliminated. By introducing some matching posts in the structure, a wideband design is achieved with 55% bandwidth covering from 11 to 19.5 GHz, where the insertion loss is lower than 0.28 dB. Some parameter sweeps are presented to investigate the effect of the rotor displacement during rotation. A prototype of the proposed rotary joint was fabricated using CNC milling for verification of the design. The measured results agree well with the simulated ones and prove the excellent performance of the proposed rotary joint.

Integrated substrate groove gap waveguide and application for filter design

In this article, an integrated substrate groove gap waveguide (Integrated-SGGW) is proposed, which is composed of gap and groove layer in printed circuit board technology, which is considered a highly integrated circuit design technology. Electromagnetic wave is transmitted via the dielectric groove in transverse electric mode. Firstly, the waveguide is analyzed, including dispersion characteristics, transmission characteristics, characteristic impedance and field distribution. Then, the theory of dispersion and characteristic impedance for the Integrated-SGGW are given, and the waveguide is comprehensively analyzed. An Integrated-SGGW is fabricated, verified, and compared with substrate integrated waveguide and other waveguides. To show Integrated-SGGW applications in the design of millimeter wave circuits, a third-order bandpass filter using the Integrated-SGGW is designed, fabricated, and verified.

Hard–Soft Groove Gap Waveguide Based on Perpendicularly Stacked Corrugated Metal Plates

A new electromagnetic band gap (EBG) structure based on the soft and hard surfaces for gap waveguide (GW) technology is introduced in this article. The proposed EBG structure consists of a soft surface and a hard surface in parallel with a gap between them, where the ridges/corrugations of the two surfaces are perpendicular to each other or with an angle near 90°. Compared with the contactless bed of nails EBG, the most widely used EBG structure in GW technology, the structural strength of the new EBG structure is increased significantly, which makes it very suited for high-frequency applications. Another advantage is that with the varying of the angle between the ridges/corrugations of the two surfaces, the stopband shifts in a wide frequency band, which makes the stopband tunable after the EBG is fabricated. The stopband performance of the proposed EBG is investigated. Straight and bended groove GWs (GGW) employing this new EBG are designed, manufactured and tested. The isolation performance with different columns of ridges/corrugations is also tested. The measured results show the proposed GGWs have excellent transmission performance.

A W-Band High-Efficiency Multibeam Circularly Polarized Antenna Array Fed by GGW Butler Matrix

In this letter, a high-efficiency multibeam circularly polarized (CP) antenna array with the groove gap waveguide (GGW) feeding technology for W-band application is proposed. First, a wideband CP septum antenna element based on GGW structure is proposed. The antenna has a simple structure with high tolerance, and the GGW technology reduces the machine difficulty, making the antenna easier to work in the higher frequency. Next, a 4 × 4 GGW Butler matrix is designed to feed the antenna array. Finally, a high-efficiency W-band four-beam CP endfire antenna array is fabricated and measured. Measured results verify that the antenna has a wider impedance bandwidth of 17.6% from 77.5 to 92.5 GHz for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB. The measured AR values of the main lobe range of four beams are almost less than 3 dB. Also, stable radiation patterns are obtained. The maximum gain and radiation efficiency are 15.29 dBic and 89.6%, respectively.

Ka-band planar slotted waveguide array based on groove gap waveguide technology with a glide-symmetric holey metasurface

The design of a planar slot array in groove gap waveguide technology implemented by glide-symmetric holes as Electromagnetic Band Gap structure is here presented. Despite the advantages of using holes instead of pins in terms of manufacturing simplicity and cost,the larger size of the holes compared to pins needs to be considered when designing slot arrays without grating lobes. A 1 to 4 corporate feed network is designed using this technology as well. Corrugations are included to further reduce the grating lobes. Experimental results support the viability of the proposed concept for designing glide-symmetric planar arrays of any size.

Implementation of tunable resonators in planar groove gap waveguide technology

Abstract We present a tunable planar groove gap waveguide (PGGWG) resonant cavity at Ka-band. The cavity demonstrates varactor loading and biasing without bridging wires or annular rings, as commonly is required in conventional substrate-integrated waveguide (SIW) resonant cavities. A detailed co-simulation strategy is also presented, with indicative parametric tuning data. Measured results indicate a 4.48% continuous frequency tuning range of 32.52–33.98 GHz and a Qu tuning range of 63–85, corresponding to the DC bias voltages of 0–16 V. Discrepancies between simulated and measured results are analyzed, and traced to process variation in the multi-layer printed circuit board stack, as well as unaccounted varactor parasitics and surface roughness.

Mechanical reconfigurable phase shifter based on gap waveguide technology

This paper presents a reconfigurable phase shifter based on gap waveguide technology. The phase shift is achieved by sliding the side wall of a groove gap waveguide (GGW). By changing the width of the GGW, its propagation constant is tuned, and consequently, the phase shift along the GGW will be controlled. The simulation and measurement results indicate about 34.5% impedance bandwidth while the maximum insertion loss is 0.6 dB and the maximum phase shift of 524° is obtained.

Array of stacked leaky-wave antennas in groove gap waveguide technology

The design of an array of stacked leaky-wave antennas in groove gap waveguide technology is presented in this work. The proposed array is formed by simply stacking a number of leaky-wave antennas one on top of the other and feeding all of them with uniform amplitude and phase. The inter-element distance is studied in order to avoid grating lobes and to maximize the directivity. A feeding network based on vertical coupling is designed, where the input port feeds the bottom element, and then the energy is equally coupled to the other elements. To obtain maximum directivity the phase is corrected at each element separately. The central frequency of the proposed design is 28 GHz. With this technique of stacking the elements a pencil beam is achieved, i.e. the radiated energy is focalized in the two main planes. The designed array with four elements achieves an enhancement of + 5 dB, reaching 24.5 dBi of directivity in comparison to 19.6 dBi of directivity of the single leaky-wave antenna made in this technology. A prototype is manufactured and measured and its results are presented and compared with the simulations.

Technology Assessment of Aperture Coupled Slot Antenna Array in Groove Gapwaveguide for 5G Millimeter Wave Applications

A compact triple-layer series fed slot unit array using Groove Gap Waveguide (GGW) technology for 5G millimeter-wave applications is presented in this paper. The design employed a two-step coupling mechanism for the radiating slots. The aperture coupling design when combined with the groove gapWaveguide (GGW) technology allows achieving three different goals: First, a reduction of the array size in the transversal direction, so more unit arrays can be added without grating lobes. Secondly, low insertion losses with high radiation efficiency. And third, a reduction of the manufacturing complexity with good stability against fabrication tolerances of up to 0.1 mm, making the design feasible to be massively deployed. The antenna was fabricated and measured showing good agreement with the numerical simulation results, the antenna provides a peak realized gain of 12.15dB at the central frequency of operation and a fractional bandwidth (FBW) of 9%.

Broadband Transition from Rectangular Waveguide to Groove Gap Waveguide for mm-Wave Contactless Connections

In this paper, the authors present a broadband transition from the standard WR-10 rectangular waveguide (RW) to a groove gap waveguide (GGW) in the W-band. The transition structure is based on electromagnetic band gap (EBG) technology where two EBG units are used, which are responsible for the transition and forming the transmission line. Metal pins in the E-plane together with the back surface of the transmission line create a forbidden band, which prevents power leakage between the connecting parts. Small air gaps will not harm the transition performance according to the simulation, which means it has a better tolerance of manufacturing and assembly errors and, thus, has advantages for mm-wave contactless connections. A back-to-back transition prototype was designed, fabricated and measured. The length of the GGW is 39.6 mm. The measured |S11| is better than −13 dB and the measured |S21| is better than −0.6 dB over 76.4–109.1 GHz, covering a bandwidth of 35.3%.

A Ka-Band Circularly Polarized Fixed-Frequency Beam-Scanning Leaky-Wave Antenna Based on Groove Gap Waveguide With Consistent High Gains

A novel fixed-frequency beam-scanning circularly polarized (CP) leaky-wave antenna based on the groove gap waveguide (GGW) structure is presented, operating in the Ka-band. By adopting the serrated ridge, a slow-wave transmission is achieved and used to excite the 80 CP patches on the top of the GGW. The operation states of the patches can be switched between “ON” and “OFF” states by controlling the biasing of the p-i-n diodes. Thus, a beam-scanning antenna with CP characteristic is developed by manipulating the period length of the antenna. Both the simulated and measured results are given as validations of the antenna performance. A measured peak gain of 17 dBic and a beam-scanning range larger than 83° can be achieved, with good CP performance.

True-Time-Delay Mechanical Phase Shifter in Gap Waveguide Technology for Slotted Waveguide Arrays in Ka-Band

This article proposes a novel all-metal mechanical phase shifter in gap waveguide technology. The phase shifter is aimed at providing beam-scanning capabilities to conventional slot array antennas along the elevation plane. To validate experimentally the beam-steering functionality, a 4×8 slot-array antenna has been designed and fabricated, along with the phase-shifting mechanism. The whole antenna consists of two pieces: a lower rotatable block, which changes the length of concentric groove gap waveguides, and an upper fixed block, where the slot-array antenna is placed. Experimental results validate the proposed concept, having obtained steering angles of up to 25°, with gain levels around 20 dBi with an antenna efficiency close to 90%. A reflection coefficient below -10 dB is achieved for a wide range of rotation angles from 29.5 to 30.5 GHz. The proposed phase shifter is completely scalable to any array size and its true-time-delay nature enables wide steering ranges for closely-spaced slot arrays with wideband radiation performance.

Half-Air-Filled Ball-Grid-Array-Based Substrate-Integrated Groove-Gap Waveguide and its Transition to Microstrip at W-Band

A half-air-filled substrate-integrated groove-gap waveguide is proposed for millimeter-wave and terahertz applications. The waveguide is constructed by a ball grid array using a flip-chip technique without metallic vias with lightweight and low profile. The possible leakage perpendicular to the groove is prevented by solder balls as modeled by an equivalent circuit. Besides, an inline transition between the proposed waveguide and a microstrip line is proposed, fabricated, and measured. The design concept and working mechanism are explained. Good agreement between simulation and measurement is observed. The simulation shows that the proposed waveguide can cover the entire ${W}$ -band (70–118 GHz), and the measurement demonstrates that the proposed transition can operate at 90–98.8 GHz.

A Simple Asymmetric Orthomode Transducer Based on Groove Gap Waveguide

The groove gap waveguide (GGWG) technology is used to design a simple asymmetric orthomode transducer (OMT) at the Ka -band in this letter. The OMT consists of two metal layers which do not need electrical contact due to the property of the gap waveguide technology. The vertical polarization (VP) is directly fed to a standard rectangular waveguide port from the main arm of a square waveguide, while the horizontal polarization (HP) is fed to the side arm by an H-bend. No septum or iris is needed, which contributes to a simple structure. The OMT has been manufactured and measured using a back-to-back setup. A high isolation of over 40 dB is achieved within the working band from 26.1 to 29.3 GHz. The reflection coefficient is below −11.4 and −17.7 dB for the HP and VP, respectively. The higher return loss of the HP is caused mainly by the manufacturing errors. Nevertheless, the insertion loss for both polarizations is below 0.25 dB for a single OMT.