Yasuhiro Tsunemitsu

Center feed single layer slotted waveguide array

A center feed configuration is newly introduced to enhance the bandwidth as well as to suppress the frequency dependent beam squinting in single layer slotted waveguide arrays. A multiple-way power divider consisting of cross-junctions is installed at the center of the aperture in an alternating-phase fed waveguide slot array to reduce the long line effect in the radiating waveguide. Each radiating slot is equipped with an inductive wall for reflection canceling, which dispenses with the beam tilting technique for suppressing cumulative reflection and assures the boresight beam. All these are equipped in single layer and are potential for low cost mass-production as is usual the case with alternating phase-fed arrays. The test antenna is fabricated at 26GHz band for FWA system. A 30.5 dBi gain with 46% efficiency with the main beam staying in the boresight is obtained. The sidelobes of -9.5 dB associated with the aperture blockage for the center feed is suppressed to below -14.7 dB at the design frequency, by applying a genetic algorithm for controlling the slot excitation

Reduction of Long Line Effects in Single-Layer Slotted Waveguide Arrays With an Embedded Partially Corporate Feed

Single-layer slotted waveguide arrays have various advantages such as low cost and mass productivity for fabrication, high gain and efficiency especially in millimeter wave band. They have traveling wave operation and the bandwidth becomes inherently narrower due to the long line effect as the antenna gain increases. This paper proposes the partially corporate feed in the single-layer structure, which inherits the advantage of low cost in fabrication. The bandwidth enhancement as well as the degradation due to the non radiating area in the aperture is assessed. The feasibility/potential of the embedded partially corporate feed is demonstrated by the experiments using the E- to H-plane power divider with very small blockage.

Reflection Characteristics of Center-Feed Single-Layer Waveguide Arrays

The reflection characteristics of large alternating-phase fed single-layer waveguide arrays with center-feeds are investigated to identify the mechanism for bandwidth narrowing effects. Firstly, the overall reflection for the whole array is analyzed by FEM and fine agreement with measurements is demonstrated. It is deviating from the conventional prediction based upon a simple sum of reflections from components in the array, such as the multiple-way power divider, the slot waveguides and the aperture at the antenna input. Careful diagnosis reveals that the mutual coupling between the alternating phase waveguides via external half-space is the key factor in reflection accumulation. Amongst all, the slot with strong excitation whose position depends upon the aperture illumination design produces the dominant contribution in the mutual coupling.

Polarization isolation between two center-feed single-layer waveguide arrays arranged side-by-side

We have proposed a FWA system for short range high speed communication with full reuse of frequency based upon high polarization isolation inherent to planar slotted waveguide arrays. Two center feed single layer slotted waveguide arrays with orthogonal linear polarization are used for transmitting and receiving, respectively. Cross polarization of less than -30 dB of a single antenna and a good isolation of about -80 dB between two antennas arranged side-by-side is observed. Propagation data should be accumulated in future.

Center-feed comprised of E to H-plane cross-junctions in an alternating-phase fed single-layer slotted waveguide array

This paper demonstrates the reflection suppression over a wideband of the feed waveguide which uses E-to-H-plane cross-junctions in the alternating-phase fed single-layer waveguide array. The FEM analysis is conducted using HFSS for each component as well as the full structure of the array, which has more than 30dBi gain.

Grating lobe suppression by a parasitic dipole layer over a waveguide transverse slot array with reflection-canceling posts

A unit element consisting of a transverse slot, a post and a pair of parasitic dipoles is proposed for an application in the bore-sight beam antenna array to suppress grating lobes with minimum unit reflection at the waveguide input. The unit is designed with suitable dipole position and dimensions to suppress radiation in the directions of grating lobes in a transverse slot array and with suitable diameter and position of the post to minimize input reflection. The reflection and radiation characteristics of the unit are analyzed by the method of moments (MoM). It is found that larger reflection of a transverse slot can be reduced below -20 dB while its uniform pattern can be suppressed by more than 20 dB in the direction of the grating lobes.

A ridged cross-junction power divider for small blockage and symmetrical slot arrangement in the center-feed single-layer slotted waveguide array

We have proposed a ridged cross-junction power divider for the feed waveguide in a center-feed single-layer waveguide slot array antenna. This feed waveguide is advantageous in terms of reducing blocking area and forming a symmetrical slot array to obtain high isolation. Furthermore, reflection is less than -20dB at the design frequency. The calculated sidelobe level of a ridged cross-junction model is almost -13 dB in the H-plane at 25.3GHz.

Single-layer slotted waveguide array with reflection canceling stairs

In this paper, a new slotted waveguide array for solving the low efficiency problems of single-layer slotted waveguide arrays is proposed. A novel reflection canceling unit consisting of a slot and a stair beneath on the broad wall of the waveguide is proposed. It brings about the transmission phase delay resulting in dense slot arrangement while the increase of slot coupling toward the waveguide end dispenses with the increasing slot offset. The improvement of the array characteristics are predicted

Design of a 39 GHz band alternating-phase fed double-layer waveguide slot antenna with the underneath partially-corporate feeding circuit

The fabrication technique called “pressure bonding” by applying a pressing at ambient temperature which has very high mass-productivity is supposed to realize a 20×20 elements double-layer waveguide slot array. Since the electric contact can not be realized at all locations, an alternating-phase fed array is adopted in this study. A partially-corporate feeding circuit installed in the bottom layer below the radiating waveguides is introduced to decompose the whole antenna into 2×2 sub-arrays, and so as to achieve relatively wideband characteristics. The five-element sub-arrays in both feeding and radiating parts as well as T-junctions and input aperture are designed at 38.75 GHz. As the design results, a directivity of 33.7 dBi and the corresponding aperture efficiency of 70.0% are realized at the design frequency.

The Ridged Cross-Junction Multiple-Way Power Divider for Small Blockage and Symmetrical Slot Arrangement in the Center Feed Single-Layer Slotted Waveguide Array

The center-feed in a single-layer slotted waveguide array [1]-[3] is one of the key components in polarization division duplex (PDD) wireless systems. Two center-feed arrays with orthogonal polarization and boresight beams are orthogonally arranged side-by-side for transmission and reception, simultaneously. Each antenna has extremely high XPD (almost 50dB in measurement) and a very high isolation (over 80dB in measurement) between two arrays is observed provided the symmetry of slot arrangement is preserved [4]. Unfortunately, the area blocked by the center feed causes high sidelobe levels. This paper proposes the ridged cross-junction multiple-way power divider for realizing blockage reduction and symmetrical slot arrangement at the same time.