Slotted Waveguide Antenna Research Articles

Characteristics of 6 × 26 Slotted Waveguide Array Antenna for Wave Monitoring Radar System

This paper presents the characteristics of a 6 × 26 slotted waveguide array antenna for a wave monitoring radar system. The proposed antenna was designed as a double-layer structure that operated in the Ku-band and combined the radiating antenna and feeding antenna structures to secure a broad bandwidth. To realize the high-gain properties of the antenna and the beamwidth control, parameters such as the resonance slot length, width, offset, and angle of the feeding slot placed on the broad wall were precisely calculated using the iteration. The measured results for the voltage standing wave ratio, radiation patterns, half-power beamwidth, and peak gains of the 6 × 26 slotted waveguide array antenna agreed well with the simulated results.

Antenna array with switching scanning in elevation plane

It is known that the most reliable communication in hard-to-reach places such as the Arctic, Tundra, Taiga is satellite communication [1-5]. Therefore, for satellite communications, it is necessary to develop your own antenna arrays. This article discusses a waveguide-slot antenna array with a Luneburg lens for a mobile satellite communications terminal, which provides a continuous and stable signal. This antenna operates in the 10.9 to 14.5 GHz frequency range. Possesses vertical polarization. The overall dimensions of the antenna array are: diameter of the diagram-forming lens 256 mm (thickness 5 mm, material FLAN 2.8 (epsilon 2.8, tangent delta 0.0015)); waveguide length 600 mm (internal section 10.5 mm by 5 mm, filling FLAN 2.8). Slotted waveguide antennas and lens are made of standard FLAN 2.8 material (epsilon 2.8, tangent delta 0.0015) 5mm thick, foiled on both sides. There are 17 coaxial cables to the HF switch (equal lengths are not required), the scanning step in elevation is 5 degrees. When using 54 waveguide-slot antennas and 18 switch inputs, a scanning sector in elevation of 90 degrees is provided. All the nodes were pre-modeled separately a cylindrical Luneburg lens with suitable waveguides, excited by slits; slotted waveguide antennas; coaxial-waveguide transitions.

Magnetically scannable slotted waveguide antenna based on the ferrite with gain enhancement

In this paper, a ferrite-filled rectangular waveguide as a balanced composite right/left-handed (CRLH) transmission line is considered. Based on the surface current density of dominant mode, a centerline longitudinal slot on the broad wall of this ferrite-filled rectangular waveguide can be radiate to the free space as a leaky-wave antenna (LWA). This proposed LWA has the both capability of the fixed-bias frequency scanning and fixed-frequency bias scanning from negative to positive angles. However, the gain of the centerline slotted ferrite-filled rectangular waveguide antenna is not acceptable. By adding another slot and changing the position of slots on the broad wall, the gain is improved to more than 9 dB in frequency range of 6.59–6.69 GHz.

Efficient SIW-Feed Network Suppressing Mutual Coupling of Slot Antenna Array

In this communication, an effective method to suppress mutual coupling between two substrate-integrated waveguide (SIW) slot antenna arrays is presented. To achieve that, a decoupling feed network is used. The feed network is composed of a two-layer directional coupler that is connected to two SIW-slot antenna arrays directly to establish an indirect coupling with controlled magnitude and phase, which can effectively reduce the direct coupling generated by surface waves between the array elements. A 2 ×4 array of slot antenna as well as the proposed decoupling network is designed, fabricated, and measured to illustrate the effectiveness of the proposed technique. The measured and simulated results verified the good decoupling performance. The measured mutual coupling is about -35 dB at the center frequency without negatively affecting the return loss and radiation patterns. The proposed mechanism of the decoupling network is simple and successfully used in SIW slot antenna arrays.

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.

STUDY OF PHASED ARRAYS OF SLOTTED WAVEGUIDE ANTENNAS WITH DIELECTRIC FILLING

The article describes the computer simulation of phased antenna arrays consisting of slotted waveguide antennas with air and dielectric filling. It is shown that inser-tion of a thin dielectric layer shifts the operating frequency range of phased anten-na arrays by 1 GHz or more down in frequency while maintaining directional char-acteristics.

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.

A Dual-Layer Filtering SIW Slot Antenna Utilizing Double Slot Coupling Scheme

This letter presents a filtering substrate integrated waveguide slot antenna design with multiple radiation nulls based on a double slot coupling scheme. It consists of a dual-layer cavity resonator, a slot in the first layer, and two coupling slots inserted in the middle layer. The slot in the first layer functions as the antenna radiator. This radiator is etched in the first cavity instead of the last stage of the network, resulting in two radiation nulls. A double slot coupling scheme is employed in the middle layer to not only couple the two-layer cavity resonators but also generate two more radiation nulls. Owing to these radiation nulls, the antenna features high-frequency selectivity as well as out-of-band radiation suppression level. For demonstration, the proposed filtering antenna is implemented and tested. The antenna operates at the center frequency 4.5 GHz with 15.4% (4.2-4.9 GHz) measured bandwidth. The maximum gain within the operating band is 7.5 dBi and four radiation nulls are generated. Better than 21 dB out-of-band radiation rejection level is obtained.

Wideband Antennas Using Coaxial Waveguide

Waveguide arrays comprise slot radiators cut into hollow, single-mode, standing wave structures. Their impedance bandwidth and compactness are limited by the waveguide cutoff. By using the TEM mode of a coaxial waveguide, a more compact structure with a larger bandwidth is possible at the expense of increased ohmic loss in the waveguide. Using this basis, a new type of slotted coaxial waveguide antenna is presented. A compact waveguide array means that the element and array aspects are not independent, and with no accurate transmission line models for the structure, the design is from a parametric study by simulation. Two basic designs are demonstrated: the first with no constraint on the azimuthal extent of the slots, and the second where some mechanical strength of the waveguide is maintained by constraining the azimuthal extent of the slots to be 90° or less. The parametric studies provide insight for realizing the high bandwidth, and measurements of prototypes confirm the performance. These antennas are useful for integration with cylindrical structures such as masts or bicycle and drone frames.

A Compact Wideband Planar Magic Tee for Monopulse Antenna Array Applications

This letter presents a compact, wideband, planar, E-arm folded magic tee at $Ku$ -band for monopulse slotted waveguide antenna array applications. A novel impedance matching structure, an L-shaped septum, is implemented at the magic tee junction, which results in wide impedance bandwidth at all ports. The height of this septum is the same as that of the waveguide height, which allows the design to be very compact. An impedance bandwidth of 22% is achieved for a return loss of 20 dB. The magic tee is manufactured using a high-precision electric discharge machining (EDM) process and followed by the integration of subparts using silver epoxy bonding. Simulation and measured results are compared. Measured amplitude balance of < 0.1 dB, phase balance of <2°, and isolation of better than −35 dB have been achieved. The proposed design is a good technique for the design of broadband, miniaturized monopulse comparators for monopulse antenna array applications.

Simulation Modeling of the Distribution of Microwave Field Strength in the Grain Layer

To ensure quick prototyping and reduce the possibility of losses caused by errors at various stages of development and implementation of equipment for microwave heating of dielectric materials, the development and simulation of models is of particular importance. The aim of this work is simulation of a slotted waveguide grating for grain drying. The main task of the simulation was to ensure an even distribution of power through each slot. Simulation modeling was carried out using a specialized software package FEKO. To describe the model, an exact calculation method was used - the method of moments; the results were verified. The dependences of the antenna SWR on the width of the slots and the angle of rotation of the slots were investigated and optimal arrangement of slots was chosen. Simulation modeling of field distribution showed that placing the waveguides farther from the container leads to the alignment of the field inhomogeneity, but some part of the radiated power is lost in this case. As the calculation results showed, an increase in the distance between the waveguide and the container with grain did not affect the SWR of the waveguides. It should be noted that in a real situation, the wave character of the field is smoothed out due to heat transfer, which cannot be taken into account in the process of electromagnetic modeling. In addition, the entire spectrum of possible changes in the dielectric parameters of the grain should be investigated in order to analyze the process of wave propagation at high grain moisture. It is also advisable to consider other modifications of the slotted waveguide antennas, which can provide more uniform heating inside the container with grain.

Design and Analysis of Slotted Waveguide Antenna Radiating in a “Plasma-Shaped” Cavity of an ECR Ion Source

The design of a microwave antenna sustaining a high-energy-content plasma in Electron Cyclotron Resonance Ion Sources (ECRISs) is, under many aspects, similar to the design of a conventional antenna but presenting also peculiarities because of the antenna lying in a cavity filled by an anisotropic plasma. The plasma chamber and microwave injection system design plays a critical role in the development of future ECRISs. In this paper, we present the numerical study of an unconventionally shaped plasma cavity, in which its geometry is inspired by the typical star-shaped ECR plasma, determined by the electrons trajectories as they move under the influence of the plasma-confining magnetic field. The cavity has been designed by using CST Studio Suite with the aim to maximize the on-axis electric field, thus increasing the wave-to-plasma absorption. As a second step, an innovative microwave injection system based on side-coupled slotted waveguides is presented. This new launching scheme allows an uniform power distribution inside the plasma cavity which could lead to an increase of ion source performances in terms of charge states and extracted currents when compared to the conventional axial microwave launch scheme. Finally, the use of both the “plasma-shaped” cavity and the microwave side coupled scheme could make the overall setup more compact.

Design and research of single‐sided slotted waveguide antenna with a large beam declination

Design and research of single‐sided slotted waveguide antenna with a large beam declination

Slotted ridged waveguide antennas with partial dielectric filling

Slotted single-ridge waveguide antenna with dielectric filling has been simulated. Dielectric material has been used to fill the slots, and to form a thin layer directly under the slotted broad wall. The specific pairs of ridge dimensions have been found that provide the same cut-off frequency for an air-filled ridged waveguide as it is for a broader air-filled rectangular waveguide. It has been shown that waveguide ridging followed by insertion of a thin dielectric layer under the slotted wall shift consecutively the antenna operating band down to lower frequencies. The specific values of thickness and permittivity of the dielectric layer suitable for frequency shifting have been found. The simulated characteristics of a 20-element dielectrically filled slotted single-ridge waveguide antenna have been presented. Resultantly, the efficient method of shifting the operating interval of a slotted-waveguide antenna down to lower frequencies has been proposed. The method does not require a broader waveguide, and therefore is effective with respect to low frequency – mass/dimension trade-off.

Planar slotted ridged waveguide antenna arrays with dielectric layer

The paper simulates the options available to move operating range of slotted waveguide antennas downward in frequency without changing the waveguide cross-section, and suggests the ways for designing linear waveguide-slotted elements based on rectangular and ridge waveguides with air and partial dielectric filling. The critical frequency of the fundamental mode of a 16x8 mm rectangular waveguide moves by ridging from 9.5 to 6.5 GHz. Partial dielectric filling of the cavity of the ridge waveguide makes it possible to additionally shift the operating range downward in frequency by 6-10% without making changes to antenna design. The antenna characteristics of linear arrays based on a dielectric-filled ridge slotted waveguide have been compared in terms of gain and voltage standing wave ratio to similar designs of arrays on rectangular and air-filled analogues. Based on the obtained structures of linear elements, simulation models of planar arrays have been constructed so that they have the similar area of total surface. Simulated frequency dependence of the realized gain for planar arrays has demonstrated a shift of the operating range downward in frequency. The analysis of the directivity characteristics of planar arrays for various phase shifts between the linear elements has been carried out. The simulation results have shown that the use of a dielectric-filled ridge waveguide gives an advantage in phase scan angle of the main beam of the radiation pattern. With the same phase shift, in planar arrays of dielectric-filled ridge waveguides, the main beam scans for a larger angle while keeping side lobes at low level. Thus, the use of a ridge slotted waveguide with a dielectric layer inside makes it possible to expand the phase scan angle.

A Reciprocity Method of Analysis for Gap Waveguide Slot Antennas

This paper introduces analytical solutions to gap waveguide slot antenna structures. The reciprocity method is used for the analysis by exploiting Green’s function of a bed of nails structure employing a homogenized plane-wave spectral-domain approach. Green’s function is found using parallel plate waveguide and surface admittance concepts. The spectral surface admittance of the pin structure is calculated using asymptotic boundary condition (ABC), and the unknown antenna slot currents are solved using moment methods. The structure is designed to have a cutoff frequency of 10–15 GHz, and the central operating frequency of the slot is 12.5 GHz. This approach is applied to the specific geometry of a propagating ridge gap waveguide single transverse broad wall slot antenna structure. The equivalent series impedance and far zone fields and patterns are calculated, and the results are compared with a full-wave commercial software, and they are proved to be accurate.

Radiation characteristics of sharply directed conical waveguide-slot antenna arrays

Currently, much attention is paid to antenna arrays, the emitters of which can be located in the bow of unmanned aerial vehicles (UAVs). Emitters can be longitudinal, transverse or oblique slots located along the generatrix of the cone on the conducting surface. A number of specific requirements are imposed on such ARs used in on-board radar systems (radars) of UAVs, among which we can note the need to form a highly directional total-difference directional pattern (DP) with a maximum of the total DP and a minimum of a difference DP in the direction of the UAV flight axis, as well as high gain and slope of the difference characteristic. The aim of this work was to study the radiation of a waveguide-slot antenna array (WASAA) installed on a conical surface and providing linear polarization of the emitted field in the direction of the cone axis. For this, electrodynamic modeling of various configurations of WASAA, located both in free space and on a conical surface, was carried out. For the developed models of antennas, the directivity characteristics and their dependence on the geometry and dimensions of the WASAA are determined. The results of an experimental study of the characteristics of a model of a conical antenna emitting a field of linear polarization in the direction of the cone axis are presented. The experimental results are compared with the results of electrodynamic modeling. The results obtained are of practical interest for the development of airborne antenna UAVs.

5G NR FR2 Femtocell Coverage Map Using an Omnidirectional Twisted SWAA

This article reports the implementation and coverage map of a mm-waves femtocell, using a high-gain omnidirectional twisted slotted-waveguide antenna array (SWAA). The twisted SWAA provides 14.7 dBi gain and 1.1-GHz bandwidth in the frequency range 2 (FR2) from the 5G new radio (5G NR) standard. A 91-m2 indoor coverage is demonstrated and its coverage map is estimated by measurements of the root mean square error vector magnitude (EVMRMS) parameter at 36-spatially distributed reception points throughout the laboratory. The 5G NR femtocell operates with 50-MHz bandwidth and 30 kHz-spaced subcarriers, giving rise to 104.8 Mbit/s throughput, whose signal quality is analyzed accordingly to the 3GPP Release 15 recommendations. Line-of-sight (LOS) and NLOS (non-LOS) propagation scenarios are evaluated, implying in EVMRMS variation from 3.13% to 19.4%. Coverage of 94% and 89% are achieved for QPSK (Quadrature Phase Shift Keying) and 16-QAM (Quadrature Amplitude Modulation) systems, respectively, demonstrating its applicability to the deployment of 5G NR femtocell operating in mm-waves.

해양 사고 방지를 위한 레이다 시스템용 고이득 슬롯 배열 도파관 안테나 설계

This paper proposes a design of a high-gain slotted array waveguide antenna of a radar system to prevent accidents at sea. The proposed antenna has a reduced size, 2−3, of the broad wall length and the narrow wall length of the WR-51 standard waveguide. To realize a low profile and high gain in comparison with the WR-51 standard waveguide slotted array antenna, the parameters, such as the slot length, width, offset, and distance between slots, were precisely calculated using the iterated simulations. The reflection coefficients and radiation patterns of the proposed antenna corresponded with the characteristics of the WR-51 standard waveguide antenna. The measured reflection coefficients and radiation patterns of the fabricated prototype antenna conformed with that of the simulated ones. The peak gains measured at the targeting frequency band were observed at 28 dBi, which were less than approximately 1 dBi of the simulated gains.

Low sidelobe level circularly polarised monopulse slot waveguide antenna array for Ka‐band application

A circularly polarised (CP) monopulse waveguide antenna array for Ka-band wireless communication is proposed. The antenna structure can be divided into six layers from top to bottom, including radiating layer, aperture layer, cavity layer, aperture layer, feeding layer and monopulse comparator. The upper radiating layer allows two transmission modes of the transverse electric (TE) wave and the transverse magnetic (TM) wave to pass through. The 90° phase difference can be obtained by adjusting the horizontal and vertical angles of the horn radiator, which realises the CP radiation pattern. Besides, the 0° or180° phase difference produced by the monopulse comparator enables the antenna to obtain a monopulse radiation mode. In order to obtain the low sidelobe characteristics, the coupling parameters of the coupling layer are weighted by the Taylor distribution. The overall size of the antenna is 194 × 25 × 31 mm3. The slot waveguide antenna is fabricated and measured to validate the proposed design. The measured results show that the monopulse system can achieve an impedance bandwidth of 3.7% (34.5–35.8 GHz) in the Ka-band at the centre frequency of 35 GHz. The sum-pattern maximum gain and radiation efficiency are 23.3 dBic and 75% at 35 GHz, and the gain of the whole bandwidth is >20 dBic. The axial ratio and the sidelobe level is less than 1.2 and −28 dB, respectively. The difference-pattern amplitude imbalance is <0.2 dB and the null-depth lower than −30 dB. Also, the isolation is better than 30 dB. Besides, the pure metal structure of waveguide has incomparable advantages in a harsh environment.