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Design Procedure for 2D Slotted Waveguide Antenna with Controllable Sidelobe Level

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Abstract

This paper presents an inventive and simple procedure for the design of a 2D slotted waveguide antenna (SWA) having a desired sidelobe level (SLL) and a pencil shape pattern. The 2D array is formed by a defined number of 1D broadwall SWAs, which are fed using an extra broadwall SWA. For specified number of identical longitudinal slots in both dimensions, the desired SLL and the required operating frequency, this procedure finds the slots length, width, locations along the length of the waveguide, and offsets from its centerline. This is done for the radiating SWAs as well as the feed SWA. An example SWA with 8×8 elliptical slots is designed using this procedure for an SLL lower than −20 dB, where the design results are also reported in this paper.
... The larger cross-section allows for a reduction in conductor losses, while the absence of lossy laminate material makes dielectric losses negligible. Passive components suhc as waveguide circuits [5], compact couplers [6], horn antennae [7,8] or slotted waveguide array (SWA) antennae [9,10] can be realized in waveguide technology. ...
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Ceramic materials are chemical- and temperature-resistant and, therefore, enable novel application fields ranging from automotive to aerospace. With this in mind, this contribution focuses on developing an additive manufacturing approach for 3D-printed waveguides made of ceramic materials. In particular, a special design approach for ceramic waveguides, which introduces non-radiating slots into the waveguides sidewalls, and a customized metallization process, are presented. The developed process allows for using conventional stereolithographic desktop-grade 3D-printers. The proposed approach has, therefore, benefits such as low-cost fabrication, moderate handling effort and independence of the concrete waveguide geometry. The performance of a manufactured ceramic WR12 waveguide is compared to a commercial waveguide and a conventionally printed counterpart. For that reason, relevant properties, such as surface roughness and waveguide geometry, are characterized. Parsing the electrical measurements, the ceramic waveguide specimen features an attenuation coefficient of 30–60 dB/m within the E-Band. The measured attenuation coefficient is 200% and 300% higher compared to the epoxy resin and the commercial waveguide and is attributed to the increased surface roughness of the ceramic substrate.
... Although they have promising features, such as low profile, low cost, and fabrication ease, their low-power handling capacity and high losses often make them less suitable for marine radar [18][19][20]. Consequently, the slotted waveguide array (SWA) antennas [21][22][23][24][25], based on the pioneering work published by Elliot [26][27][28], are widely employed in marine radar applications. This is because of their high-power handling capacity, low losses, and good phase stability. ...
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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.
... The proposed method uses simplified closed-form equations to determine the slots nonuniform displacements, without the need to use optimization algorithms. 29,30 A major contribution lies in the use of the same proposed simplified equations to design both the radiating and feeder SWAs. Longitudinal coupling slots are proposed for the feeder SWA, displaced from the waveguide feed centerline according to the desired SLR, rather than the conventional inclined coupling slots. ...
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This article presents a complete design procedure for planar slotted waveguide antennas (SWA). For a desired sidelobe level ratio (SLR), the proposed method provides a pencil shape pattern with a narrow half power beamwidth, which makes the proposed system suitable for high power microwave applications. The proposed planar SWA is composed of only two layers, and uses longitudinal coupling slots rather than the conventional inclined coupling slots. For a desired SLR, the slots excitation in the radiating and feeder SWAs are calculated based on a specified distribution. Simplified closed-form equations are then used to determine the slots nonuniform displacements, for both the radiating and feeder SWAs, without the need to use optimization algorithms. Using simplified equations, the slots lengths, widths, and their distribution along the length of the radiating and feeder SWAs can be found. The feeder dimensions and slots positions are deduced from the dimensions and total number of the radiating SWAs. An 8 × 8 planar SWA has been designed and tested to show the validity of the proposed method. The obtained measured and simulated results are in accordance with the design objectives.
... The proposed method uses simplified closed-form equations to determine the slots nonuniform displacements, without the need to use optimization algorithms. 29,30 A major contribution lies in the use of the same proposed simplified equations to design both the radiating and feeder SWAs. Longitudinal coupling slots are proposed for the feeder SWA, displaced from the waveguide feed centerline according to the desired SLR, rather than the conventional inclined coupling slots. ...
... The design of a resonant SWA is generally based on the procedure described by Stevenson and Elliot [1], [2], and further simplified by the El Misilmani et al. in [3], [4]. In these works, the excitations of the SWA individual slots, which are translated into slots displacements, control the resulting SLR of the SWA array. ...
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Slotted waveguide antennas (SWAs) are widely used in high power microwave applications. In this paper, the slots displacements in broadwall SWAs, previously used to control the SWA sidelobe level ratio (SLR), are further investigated to also adjust the beamwidth of the SWA. A modified Taylor array design method is used to estimate the excitations of the SWA slots leading to independently controllable SLR and first-null beamwidth (FNBW). The slots displacements are then calculated from these excitations. An example is presented where the SWA has 7 slots and the proposed method is employed to find the displacements required for desired SLR and FNBW
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This work proposes a fabrication approach for 3D printed waveguide paths based on a combination of an optimized electroless silver plating process with a waveguide-specific design rule for general metal plating by introducing large scale non-radiating slots into the broad and narrow waveguide walls with a periodicity shorter than quarter of the guided wavelength. Experimental fabrication of straight sections of the proposed slotted waveguide with various gap dimensions yields an optimum gap size as result of a trade-off between silver plating quality and leakage losses through the sidewall gaps Moreover, a successful practical application of the proposed approach is presented in terms of a 3D printed multiple bend waveguide interconnect in three different space dimensions which imposes a complex task for conventional manufacturing techniques due to the need of multiple cutting planes for split block assembly. The proposed approach benefits of low cost, moderate handling effort and independence of the concrete geometry to manufacture making it therefore especially interesting for distribution and feeding networks in the context of rapid prototyping, automotive and space related applications.
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Slotted waveguide antenna (SWA) arrays offer clear advantages in terms of their design, weight, volume, power handling, directivity, and efficiency. For broad-wall SWAs, the slot displacements from the wall centerline determine the antenna's sidelobe level (SLL). This paper presents an inventive procedure for the design of broadwall SWAs with desired SLLs. For a specified number of identical longitudinal slots, this procedure finds the slots length, width, locations along the length of the waveguide, and displacements from the centerline. Illustrative examples, based on Taylor, Chebyshev and the binomial distributions are given. In these examples, elliptical slots are considered, since their rounded corners are more robust for high power applications.
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A planar slotted waveguide array antenna has been designed at 9.37 GHz for X-band radar applications. The antenna consists of multiple branchline waveguides with broadwall radiating shunt slots and a main waveguide to feed the branch waveguides through a series of inclined coupling slots. The antenna feed point is located at the center of the main waveguide. Element weights in the array have been calculated bysampling a continuous circular Taylor aperture distribution at the 25 dB sidelobe level in both the E and Hplanes. A commercially available electromagnetic (EM) simulation tool has been used to characterize the individual isolated slot and that data hassubsequently been used to design the planar array. The array is finally analyzed in a CST Microwave studio and the measured and simulated results have been found to be in good agreement.
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The paper presents an integrated design of slotted waveguide antenna arrays with inclined slots cut in the narrow wall of rectangular waveguide and with radome (hereinafter called conformal radome) tightly stuck on the radiation slots. By use of this design method, an S-band planar array antenna has been developed. The far-field test of the antenna beam pattern shows that the antenna achieves a horizontal sidelobe level of better than 40dB within 12% of its entire frequency band, and an ultralow sidelobe level of 45dB at its typical frequency points, indicating that the design method is very effective.
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A novel untilted edge-slotted waveguide antenna array with very low cross-polarization is presented. Each radiating element is composed of an untilted narrow-wall slot, and a pair of shaped irises flanks the slot in the waveguide. An array with 16 of the proposed elements for X-band application is designed and measured. Experimental results show that the antenna has an excellent cross-polarization level of <-39 dB compared to that of a conventional edge-slotted waveguide array and over 7% bandwidth of VSWR≤1.5.
The Design of Slot Arrays Including Internal Mutual Coupling
  • R S Elliott
  • W R O 'loughlin
Longitudinal Shunt Slot Characteristics
  • R J Stegen