Yohei Miura

Double-Layer Full-Corporate-Feed Hollow-Waveguide Slot Array Antenna in the 60-GHz Band

In order to achieve a wide bandwidth characteristic of high gain and high efficiency antennas, a double-layer hollow-waveguide slot array is proposed, where a full-corporate-feed waveguide is arranged in the lower layer. This antenna can be built up easily by the process of diffusion bonding of laminated thin metal etching plates, which has high precision and is possibly a low cost technique. The radiating elements and the feed waveguide are designed to suppress the reflection over a wideband. The predicted bandwidth of the reflection less than -14 dB is 8.3% for a 16 × 16-element array antenna. A test antenna is fabricated in the 60-GHz band, and about 80% antenna efficiency with more than 32 dBi is achieved over 4.8 GHz.

A low-cost and very compact wireless terminal integrated on the back of a waveguide planar array for 26 GHz band fixed wireless access (FWA) systems

A compact wireless terminal (WT) with a high-gain planar array has been developed for the Wireless IP Access System (WIPAS), which is a point-to-multipoint Fixed Wireless Access (FWA) system in the 26 GHz band. For the point-to-multipoint FWA services in rural areas, the drastic cost and size reduction of WT with the high-gain antennas and RF module is indispensable. In this paper, remarkable cost reduction of 1/10 and downsizing of 1/5 are realized by using an alternating phase fed single layer waveguide array antenna and Microwave Monolithic IC (MMIC) technologies. This terminal is 190/spl times/190/spl times/55 mm/sup 3/ in volume and less than 2.0 kg in weight which accommodates over 31 dBi very high efficiency antenna with a radome, RF module, IF modules, application specific IC (ASIC) for modem, time division multiple access (TDMA) equipment control, and medium access control (MAC). Only an Ethernet cable with 24 V dc power supply is attached on the terminal.

A 45

A 45° linearly polarized hollow-waveguide slot array antenna has been proposed to achieve low sidelobes in the E- and H-planes by a diamond-shaped array arrangement. A layer for radiating slots was added into the conventional plate-laminated antenna. The 2 × 2-element sub-array was designed to suppress grating lobes and low cross-polarization. The 16 × 16-element array in the 60-GHz band was fabricated by diffusion bonding of the laminated thin metal plates. The first sidelobe levels in the E- and H-planes were -25.5 and -26.1 dB, respectively, and the cross-polarization was - 31.5 dB in the boresight. High antenna efficiency of 70% with greater than 32 dBi gain over 5 GHz was maintained by the corporate-feed hollow waveguide structure. Quantitative amount of fabrication error due to etching and alignment was revealed by simulations.

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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.

Linearly Polarized Hollow-Waveguide Corporate-Feed Slot Array Antenna in the 60-GHz Band

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.

Reflection Characteristics of Center-Feed Single-Layer Waveguide Arrays

The authors proposed a circular-polarized array antenna by using hexagonal radiating apertures in the 60 GHz-band. The hexagonal radiating aperture is designed, and the good axial ratio characteristics are achieved in the boresight. We analyze the full structure of the 16×16-element array that combines the 2×2-element subarrays and a 64-way divider. The reflection is less than −14dB over 4.9% bandwidth where the axial ratio is less than 2.5dB. High antenna efficiency of 88.7% is obtained at 61.5GHz with the antenna gain of 33.3dBi including losses. The 1dB-down gain bandwidth is 6.8%.

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

Hollow-waveguide slot array antennas [1] [2] are suitable for millimeter-waveband since they have neither dielectric loss nor radiation loss. The authors have proposed a double-layer corporate-feed waveguide slot array antenna [3] that the feeding part in the bottom layer divides from the radiating part in the upper to realized a higher efficiency and a wider bandwidth. The element spacing can be reduced to less than a free space wavelength compared with a single-layer corporate-feed antenna where dielectric materials are installed for each element to suppress the grating-lobes in [4]. The double-layer structure cannot be fabricated easily by machining or die-casting. However, the diffusion bonding of laminated thin metal plates can fabricate at low cost similarly to the single-layer structure, because the thin metal plates are etched with high precision in the millimeter-waveband. The single-layer slotted waveguide array have fabricated at 94 GHz by the diffusion bonding using copper plates, high antenna efficiency of 60 % have been realized with an antenna gain of 31.4 dBi [5]. This paper presents a high gain of 32 dBi with a wide bandwidth of 8 % for high efficiency of 80 % in a 60 GHz double-layer corporate-feed hollow-waveguide slot array produced with copper.

A circularly-polarized aperture array antenna with a corporate-feed hollow-waveguide circuit in the 60 GHz-band

The four-aperture element for the double-layer corporate-feed hollow waveguide slot array has reflection below −15dB over 9.5% bandwidth assuming the mutual couplings by the periodic boundary walls.

A 60GHz double-layer waveguide slot array with more than 32dBi and 80% efficiency over 5GHz bandwidth fabricated by diffusion bonding of laminated thin metal plates

This paper presents conversion to circular or tilted linear polarization by adding a layer of apertures over the plate-laminated-waveguide corporate-feed slot array antenna. A circularly polarized 16×16-element array antenna achieves high antenna efficiency of 91.6% including losses at 61.5GHz by diffusion bonding of laminated metal thin plates. In a tilted linearly polarized 16×16-element array antenna, the measured cross polarization is −31.5dB in the boresite at the designed frequency of 61.5GHz.

Bandwidth of a four-aperture element for a double-layer corporate-feed hollow-waveguide slot array

Alternating phase fed single-layer waveguide slot arrays are high gain, high efficiency and very low cost antennas. They consist of two components, a slot plate and a base plate, manufactured by punching and die casting respectively. As the size of the array and the gain becomes high, the bandwidth of the overall antenna becomes narrower. In order to cover the 1.71 GHz range allocated for 26 GHz FWA in Japan with 31.5 dBi gain, 10 types of arrays, each with 180 MHz bandwidth must be prepared. This paper proposes the band switching arrays in which only the slot plate is switched for each channel while the base plate is common for all channels. The degradation of the arrays with the base plate designed at the offset frequency is compensated by the slot deign. A 1 GHz band is covered with a gain reduction of only 0.3 dB which should be compared with 5 dB if not using interchangeable slot plates.