Substrate Integrated Waveguide Leaky-wave Antenna Research Articles

Slotted Substrate-Integrated Waveguide Leaky-Wave Antenna with Improved Backward Scanning Bandwidth and Constant Gain in X-band

An H-shaped slotted leaky-wave antenna (LWA) is proposed based on balanced composite right/left-handed (CRLH) transmission lines (TLs) to improve the backward scanning bandwidth and achieve constant gain. The proposed antenna consists of a substrate-integrated waveguide (SIW) unit cell array configured by an H-shaped slot cut in the top layer of the SIW and a patch embedded beneath the H-shaped slot. The proposed design improves the backward scanning bandwidth compared to planar SIW LWAs. The measured beam radiation is in the range from −79° to 80° over the frequency range of 7.6–12.5 GHz. Moreover, a constant gain of greater than 10 dB is achieved over the entire X-band frequency range.

High Gain and Wide-Angle Continuous Beam Scanning SIW Leaky-Wave Antenna

A novel substrate integrated waveguide (SIW) adopting a leaky-wave antenna (LWA) for continuous beam scanning for tri bands is presented. For continuous beam scanning (CBS), optimization of different parameters associated with the unit cell has been carried out. Apart from this, optimal impedance matching is also obtained with the help of the characteristic impedance of the waveguide. The proposed SIW LWA scans from −58° to + 59° along with 14.50 dBi gain when the frequency changes from 10 GHz to 18.22 GHz and provides a scanning rate of 14.23. The beauty of the suggested antenna is its smaller size and high gain, along with a wider scanning range (117°) capability. This antenna’s final prototype has been fabricated, and the measurement results are matched with the simulation results.

Circularly Polarized High Gain Leaky-Wave Antenna for CubeSat Communication

In this work, a novel planar leaky-wave antenna (LWA) and its array are proposed and presented for CubeSat communication applications. Using the substrate-integrated waveguide (SIW) technology, the proposed LWA is implemented by etching periodic fan-shaped slots on top of an SIW. These novel fan-shaped slots exhibit extraordinary circular polarization (CP) radiation in high efficiency over a wide frequency band. Moreover, by switching the excitation ports, both left-handed (LH) and right-handed (RH) CPs are achieved in a wide beam steering range backward or forward. An SIW LWA prototype has been designed and tested with validate LHCP/RHCP steering beams ranging from –51° to 0° or from 51° to 0° in the elevation when the frequency varies from 27.4 to 37.3 GHz. In the 30% frequency band, the axial ratios (ARs) on the main beams are all less than 3 dB demonstrating the broadband CP characteristic. In this 1-D LWA, the realized gain varies from 12.4 to 17.9 dBi. However, it requires higher gain and a fixed beam but narrow bandwidth (BW) in some applications like CubeSats. Hence, a conformal LWA array is further introduced by combining the CP radiation of two LWAs deployed in two perpendicular surfaces of a one cubic unit (1U) CubeSat. Fed by an elaborated vertical transition, the conformal array is designed at 28 GHz with a high directive sum beam along the diagonal direction, requiring each LWA to radiate at ± 45°. As a result, the total gain is enhanced from 14.4 to 16.6 dBi with an AR of 1.8 dB and a sidelobe level (SLL) of −17.1 dB. The proposed compact planar LWA and its array provide promising CP radiation in terms of ARs, BW, polarization flexibility, impedance matching, efficiency, and gain, which reveals great potential for applications in satellite communication systems that demanding low profile, lightweight, dual CPs, and high directivity.

Multibeam SIW Leaky-Wave Antenna with Beam Scanning Capability in Two Dimensions

This paper presents a 2D multibeam antenna (2D-MBA) for two-dimensional scanning of space with fully passive elements using the substrate integrated waveguide (SIW) leaky-wave antenna (LWA) and Rotman lens for telecommunication applications. An LWA structure with 19 slot elements based on SIW in the frequency range of 14.5–22.5 GHz was designed to scan theta angles from −60 to +35 degrees, and a wideband Rotman lens was designed with five inputs, five outputs, and eight dummy ports to scan phi angles from −30 to +30 degrees. Finally, for two-dimensional space scanning, a five-element SIW LWA array was combined with a Rotman lens, and the whole structure was simulated and implemented in full-wave CST software. By optimizing the structure, the return losses of the input ports were below −10 dB, and the maximum measured gain was 20.3 dBi.

A beam‐formed leaky‐wave antenna array with power‐recycling feeding network

A substrate integrated waveguide leaky-wave antenna array using power-recycling feeding network to achieve beamforming radiation pattern is investigated in this article. The antenna array consists of three elements represented by An1, An2, and An3 on two kinds of radiation mechanism. An1 and An2 are working on the -1th spatial harmonic mode with broadside and backward radiation directions, respectively, and An3 is working on the fundamental wave mode with forward radiation direction. The open-stopband due to broadside radiation design in An1 is suppressed by arranging two similar slots in one radiation unit. By using power-recycling feeding network, the traveling wave directions in An2 and An3 are opposite, which partially compensates the opposite radiation directions of these two elements. Therefore, by adjusting the sizes of radiation slots appropriately, the proposed antenna array can achieve a cosecant–distribution radiation pattern within the range from 0° to 50°.

A Novel SIW Leaky-Wave Antenna for Continuous Beam Scanning from Backward to Forward

A novel, periodic, leaky-wave array antenna using substrate-integrated waveguide (SIW) technology is proposed for continuous beam scanning applications. For this purpose, a periodic structure with the ability to radiate from backward to forward is proposed. The unit cell of this periodic structure includes a longitudinal slot and an H-plane discontinuity. The H-plane step discontinuity is suggested to suppress the open stopband (OSB) and enable continuous beam scanning from backward to forward through the broadside. The impedance matching technique is used to suppress the open stopband. In contrast to phased array antennas, this form of antenna is distinguished by its ability to scan without requiring a complex feeding network. These antennas are used for different factors such as scanning the beam, determining the direction of arrival, avoiding collisions, indoor communications, etc. A prototype of the proposed antenna was fabricated for experimental characterization. The overall physical dimensions of the fabricated antenna are 7.9 mm × 128 mm. The results demonstrate that an adequate level of agreement between measurement and simulation is satisfactory. The results indicate that the suggested antenna can scan continuously in the frequency range of 14.5 to 22.5 GHz between −60 and +57.5 degrees through broadside with a maximum gain of 16 dBi and radiation efficiency of 71%.

Circularly Polarized Leaky-Wave Antenna With Natural Curl Property

This letter proposes a novel leaky-wave antenna (LWA) based on low profile substrate integrated waveguide (SIW), which can operate in either left-handed circular-polarization (LHCP) or right-handed circular-polarization (RHCP) mode. Different from other kinds of literature, the proposed SIW LWA is capable of CP state switching without introducing multiple LWA elements, phase-correct couplers or polarization converter, which is a single LWA element with a simple coaxial feeding/matching structure. Specially, the periodic slots on its radiation aperture are Archimedean spiral slots which are curved slots with curl property. These curled slots can excite vortex fields in the waveguide channel of SIW, and the generated vortex field is capable of changing vortex direction by selectively exciting the port of LWA, making the CP features flexible. The final Archimedean spiral slotted SIW LWA realizes LHCP or RHCP (AR < 3 dB) in the wide CP band of 27.7–34.6 GHz (BW = 22%), and the LHCP scanning range is from −51° to −10° while the RHCP beam scans from 10° to 50°.

A dual-beam steering one dimensional periodic leaky-wave antenna for large coverage

This paper proposes a dual-beam leaky-wave antenna (LWA) based on substrate integrated waveguide (SIW) technology. The unit cell of the proposed SIW LWA consists pair of transverse and longitudinal slots etched on the top and bottom surface of the SIW. The unit cell characteristics of LAW have been investigated using dispersion analysis. As a result, the open stopband (OSB) problem is suppressed in the broadside direction. As a result, the dual radiating beam of LWA scans the entire space of the elevation plane (XZ plane) without any severe gain degradation at the broadside and endfire. The proposed SIW LWA antenna works in the band of 11.5 to 15.5 GHz with a peak gain of 13 dBi. The measured results are in accord with simulation results.

Substrate Integrated Waveguide Based Leaky Wave Antenna for High Frequency Applications and IoT

Background &amp; Objective: Internet of things devices managed by wireless networks so that higher data rates can be achieved. With increase in demand of usage of Internet microwave signals are capable for delivering the demand. However these high frequency waves needs a waveguide to propagate otherwise they get affected due to atmospheric attenuation and rain fade. A modified structure of rectangular waveguide is used named as Substrate Integrated Waveguide (SIW). Methods: In this paper, the work has been carried out taking SIW and Leaky Wave Antenna. The dielectric substrate was taken as carbon. Modeling of SIW Leaky wave Antenna is done by making C shaped Slots. Design steps for modeling LWA were orderly pursued also optimized with various equations followed by Finite Element Method based modeling. A range of frequency as input is taken from 7 GHz to 11 GHz to take the analysis of design modeled. Results: The result shows the electric field intensity and radiation pattern is directly proportional with frequency while the return loss is acceptable for applied frequency range. Conclusion: The proposed antenna can radiate in omni directional radiation pattern hence can be used to connect devices with IoT.

Synthesis of cosecant-squared pattern in substrate integrated waveguide leaky-wave antennas

A synthesis procedure for realizing a cosecant-squared pattern in leaky-wave antennas (LWAs) is presented. In this method, the antenna is divided into a number of sections, each with an appropriate phase constant, length and leakage rate. The phase constant of the radiating sections is obtained such that their beam pointing angles would arrange on an appropriate layout in the shaped region. The two latter parameters are determined such that the radiation intensity of each section would decay with a cosecant-squared profile. Finally, using an optimization algorithm, i.e., a genetic algorithm (GA) optimization, the initial values of the leakage rate are adjusted to achieve the desired shaped region. The synthesis procedure is applied to a slotted substrate integrated waveguide (SIW) LWA, and a prototype of the antenna is designed to achieve the cosecant-squared pattern within the range of 10° to 30°. The results show that the antenna has low ripples (≤2 dB) in the shaped region with a low level of sidelobes (≤-18 dB) outside the region. The antenna is fabricated and measured. Measurements show a good agreement with the simulation results. The obtained results reveal that the proposed synthesis procedure can be utilized in designing cosecant-squared pattern LWAs to use in air-surveillance radar systems.

Gain Enhancement of Transversely Slotted Substrate Integrated Waveguide Leaky-Wave Antennas Based on Higher Modes

A technique for gain enhancement of transversely slotted substrate integrated waveguide (SIW) leaky-wave antennas is proposed based on higher modes. Two SIW leaky-wave antennas based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m0</sub> ( m = 3, 5) higher modes are investigated. The antennas possess the advantage of simplicity, in which the feeding structures are compact and simple. Compared with published transversely slotted SIW leaky-wave antenna based on the fundamental mode (TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode), the proposed antennas exhibit higher and more consistent gains. Besides, the antennas maintain the scanning capability from near broadside to endfire. The working principles of the antennas are explained. The propagation characteristics are investigated with a magnetic field integral method. The aperture efficiencies are analyzed. Two leaky-wave antenna designs based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> higher modes are demonstrated and compared with a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode antenna design (with almost the same dispersion characteristics). Prototypes of the three designs are fabricated and measured for comparisons. Compared with the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode antenna, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> - and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> -mode antennas have the transverse beamwidths markedly narrowed and have the gains improved by about 5.5 and 8 dB, respectively.

Multifunctional Leaky-Wave Antenna With Tailored Radiation and Filtering Characteristics Based on Flexible Mode-Control Principle

In this paper, a class of single-layered multifunctional leaky-wave antennas (LWAs) with flexibly engineered radiation and filtering characteristics are proposed and demonstrated for microwave and millimeter-wave applications. Radiating discontinuities (RDs) exhibiting multiple resonances while particularly possessing flexible model-control capability are exploited to accomplish such design freedoms and multifunctionalities of LWAs. By properly engineering the resonance characteristics of RDs under the mode-control principle, the attenuation constant of relevant LWAs can not only be freely tailored for diverse beamwidth/directivity requirements, but also simultaneously maintain a flat frequency response for radiation stability. Meanwhile, controllable filtering behaviors can be obtained as well by the LWAs thanks to the transmission zeros introduced by resonances. Consequently, both the radiation and filtering performances of LWAs can be adequately tailored by taking advantage of the mode-control capability of RDs. Under this design concept, two types of LWAs based on substrate-integrated waveguide and microstrip techniques are respectively developed for different system integration platforms. The substrate-integrated waveguide LWA whose unit cells consist of different longitudinal slots is firstly examined. Additionally, the microstrip LWA, which depends on stub-loaded resonators, is further investigated. The proposed two LWAs are all with flexible engineered electrical behaviors, single-layer, low-cost, and easy integration; they may be a potential candidate for various system applications such as 5G communication and Internet of Vehicles.

Partially Filled Half-Mode Substrate Integrated Waveguide Leaky-Wave Antenna for 24 GHz Automotive Radar

A novel highly efficient leaky-wave antenna (LWA), based on a periodic set of holes created in a half-mode substrate integrated waveguide (SIW), is conceived for automotive radar. The computer-aided design of this partially filled SIW (PFSIW) LWA is carried out using a full-wave electromagnetic simulator. As a proof-of-concept, an LWA prototype having a plate size of 15 × 126 mm $^2$ is fabricated through a standard low-cost printed circuit board (PCB) manufacturing process. Our manufactured prototype yields more than 25% impedance bandwidth, targeting the 24 GHz automotive short-range-radar band. Moreover, the measured peak gain and total antenna efficiency reach up to 15.5 dBi and 85% at 24 GHz. Furthermore, the main radiating direction steers continuously from 38 $^\circ$ to 58 $^\circ$ with an average half-power beamwidth of 12 $^\circ$ when the operating frequency changes from 22 to 26 GHz. In comparison, a 160 mm long dielectric-filled SIW (DFSIW) LWA yields a measured scanning range of 49 $^\circ$ and a total antenna efficiency of 43.8%, whereas an 80.3 mm long air-filled SIW (AFSIW) LWA exhibits a measured scanning range of 9 $^\circ$ and a total antenna efficiency of 80%. Therefore, PFSIW technology provides an optimal tradeoff between DFSIW and AFSIW for the envisaged short-range automotive radar application.

Air-Filled Substrate Integrated Waveguide Leaky-Wave Antenna With Wideband and Fixed-Beam Characteristics

In this communication, a novel wideband fixed-beam leaky-wave antenna (LWA) is proposed. The antenna is designed based on air-filled substrate integrated waveguide (SIW), which is composed of one layer of printed circuit board (PCB) in the middle and two layers of thin copper plates on the top and bottom. The different layers are aligned and fixed by screws. A long slot is etched on the top surface of air-filled SIW as a radiator. Due to the dispersive characteristic of the air-filled SIW, the antenna can radiate at a fixed direction over a wideband. To the best of our knowledge, this is the first time that the air-filled SIW is adopted for LWA design. The proposed antenna is designed, fabricated, and tested. The measured results show that its wide operating bandwidth reaches up to 37.0%, ranging from 11 to 16 GHz. The excellent fixed-beam radiation performance is obtained over the operating bandwidth. The radiation direction is fixed at 59° with only ±3° variation, and the peak gain is within 14.0-15.3 dBi. Although the beam angle can only be fixed nearly the endfire, this method offers a simple way to realize wideband fixed-beam feature.

Scanning rate enhancement in substrate integrated waveguide periodic leaky wave antenna with continuous beam scanning using delay lines

Abstract In this paper, the scanning rate (SR) is enhanced for substrate integrated waveguide (SIW) based periodic leaky wave antenna (LWA) with continuous beam scanning. Delay line is inserted in the SIW based periodic LWA to modify the group delay profile which in turn increase the SR of the SIW based periodic LWA. Addition of the delay line enhances the SR of the SIW LWA to approximately three times from 15.6° to 47° per GHz. The prototype of the proposed LWA is fabricated and experimentally measured. The simulated and measured results show that the proposed LWA scans the angular range from −30° to +27° within a frequency span of only 1.2 GHz from 14.8 to 16 GHz (relative bandwidth of 7.7 %).

Improved Design of Uniform SIW Leaky Wave Antenna by Considering the Unwanted Mode

An improved design for the uniform substrate integrated waveguide (SIW) long slot leaky wave antenna (LWA) is presented in this communication. To achieve the desired sidelobe level (SLL), beamwidth and beam direction, proper distributions for leakage constant and phase constant should be created along the slot. An accurate calculation of leakage and phase constants is performed by considering an unwanted mode, in addition to the leaky mode, along the uniform LWA structure. Considering this unwanted mode in the design procedure results in good consistency between the desired and designed radiation patterns. The presented LWA realizes a Taylor distribution with predefined SLL of -25 dB at 17 GHz. The radiation pattern, amplitude distribution, and phase distribution of the designed antenna are compared with the desired ones. This comparison shows the high accuracy of the proposed design procedure. Measurement results are also presented at 16.5, 17, and 17.5 GHz for validation of the design procedure.

Circular-Polarized Substrate-Integrated-Waveguide Leaky-Wave Antenna With Wide-Angle and Consistent-Gain Continuous Beam Scanning

Circularly polarized (CP) antennas are in high demand for use in future wireless communications. To advance the development of CP substrate-integrated-waveguide (SIW) leaky-wave antennas (LWAs) with the intent to meet this demand, a novel benzene-ring-shaped slot-loaded LWA with partially reflecting wall (PRW) vias is investigated and verified to realize wide-angle continuous beam scanning with consistent gain. The dispersion features of slot-loaded SIW LWAs with PRW vias are theoretically explored using an equivalent circuit model. The CP radiation feature is investigated numerically utilizing the E- and H-field distributions of an initial design and its equivalent magnetic currents. The results of these studies are used to demonstrate that improved CP performance over a wide-angle scan range can be attained with a change from a standard slot shape to a benzene-ring-shaped slot. The resulting benzene-ring-shaped slot-loaded CP SIW LWA was optimized, fabricated, and measured. The measured results verify that a CP beam was continuously scanned through a wide angle from backward to forward directions with a consistent gain. The prototype exhibits a continuous 97.1° CP beam scan with a gain variation between 8 and 11.3 dBic when the source frequency is swept from 9.35 to 11.75 GHz.

Two-Dimensional Near-Field Focusing Folded Reversely Fed Leaky-Wave Antenna Array With High Radiation Efficiency

This paper presents a 2-D near-field focusing (NFF) substrate-integrated-waveguide (SIW) leaky-wave antenna (LWA) array with high radiation efficiency. In most of the existing 2-D NFF antenna arrays, the required quadratic phase and balanced amplitude distribution are achieved by the use of the transverse topology with a complex feeding network or the simple radial topology with high polarization loss. Here, a folded reversely fed LWA with transverse polarization is proposed to achieve natural balanced radiation with a sample series-fed network. Meanwhile, the width of the single linear LWA is complementary with the reversely fed topology. In this case, the SIW with a stepped width is applied to achieve a quasi-uniform slot distribution and to avoid the spurious radiation. Then, all reversely fed linear LWAs are connected by the meander-line structure, which can simplify the feeding network and enhance the radiation efficiency. The limitation of the NFF LWA in radiation efficiency is broken. The 2-D focusing principle and the design process of the proposed antenna are presented in this paper. As an example, a 2-D focusing SIW LWA array operated at 35 GHz with an 80% radiation efficiency is fabricated and measured.

Planar SIW Leaky Wave Antenna With Electronically Reconfigurable E- and H-Plane Scanning

This paper reports on a novel technique of switching radiation characteristics electronically between E- and H-planes of planar Substrate Integrated Waveguide Leaky Wave Antennas (SIW-LWAs). The leaky wave mode is achieved through increasing the pitch of bounding metallic via posts on one side of SIW transmission section. The radiation switching is achieved by extending the top and bottom metallic planes to a distance of 1 mm along the leakage side. The extended section acts as a parallel plate section which is conveniently connected or disconnected from the leaking side of SIW through PIN diodes. The `ON' state of PIN diodes extends the metal guides and results in the H-plane leakage whereas `OFF' state of PIN diodes truncates the extended metal earlier and alter the leakage line boundary condition towards E-plane. The whole concept is validated by series of simulations followed by the realization and testing of the SIW-LWA. The measured radiation pattern scans about 54° in the E-plane between 10.0 GHz to 11.7 GHz, and 58° in the H-plane from 9 GHz to 10.6 GHz. The proposed topology is a suitable candidate for remote sensing and airborne applications.

Corrections to “Substrate Integrated Waveguide Leaky-Wave Antenna With Wide Bandwidth via Prism Coupling” [Jun 18 3110-3118

In the above paper [1] , there is a description on page 1, column 2 in the introduction section: “However, no practical demonstration of this has been reported yet, probably due to the complexity of integrating this Huygens metasurface with a practical LWA.”