Amane Miura

60-GHz Wideband Substrate-Integrated-Waveguide Slot Array Using Closely Spaced Elements for Planar Multisector Antenna

A new wideband waveguide slot array is proposed for covering a wide elevation-angle range with a planar sector antenna of a multigigabit wireless LAN in the 60-GHz band. The requirement of millimeter-wave sector antennas is to realize both wide bandwidth of 11.2% and wide elevation-angle coverage with a required gain of over 10 dBi. To satisfy both the required gain and bandwidth, the important structural features of the proposed antenna are that multiple slot elements are successively arranged at an interval of the length less than one quarter guide wavelengths and that the slot length increases from the shorted waveguide end to the feed end. The operational principle of the slot array is based on multisection quarter-wavelength reflection cancellation, so the slot array can achieve the required bandwidth. Furthermore, this antenna produces a unidirectional radiation pattern by using the radiators and the reflectors, resulting in the required gain over a wide elevation-angle range. In the design, the structural parameters of the slot array are selected to meet the requirements for 60-GHz-band sector antenna. The developed substrate-integrated-waveguide (SIW) slot array achieves both the 10 dB return-loss bandwidth of 15% and the specified gain in 88-96% of the one-sector coverage range of 59-66 GHz. The effectiveness of the proposed slot array for a sector antenna is verified by the good agreement between the simulated and measured results.

Spaceborne Mesh Reflector Antennas With Complex Weaves: Extended PO/Periodic-MoM Analysis

Reflector antennas with complex mesh weave patterns are numerically analyzed by using extended physical optics (PO) combined with the periodic method of moments (MoM). The method applies the periodic MoM with Rao-Wilton-Glisson (RWG) basis and testing functions. It calculates the transmission coefficient matrix (T-matrix) of the realistic, complex weave pattern of the planar mesh, in order to calculate the modified PO current on the mesh reflector. When analyzed, the planar grid mesh is found to be compatible with the commonly used wire-grid model. The modified PO current on the locally planar mesh is implemented on the curved reflector surface for the diffraction analysis of the mesh reflector antennas. The far-field pattern of the offset parabolic antenna with grid mesh, modelled using periodic MoM, agreed well with those obtained from the wire-grid model. T-matrix calculated from the tabulated T-matrix data using the interpolation method is sufficiently accurate and compares well with the one calculated using the direct method, allowing users to choose one of the T-matrix calculation methods depending on the problem. The analysis of the mesh reflectors with two different complex weave patterns (single Satin and single Atlas at Ka band) is performed to exemplify the application of the extended PO/periodic MoM algorithm. It is shown that differences were observed in cross-polarization discrimination (XPD) for circular polarization operations depending on the weave patterns. This result demonstrates the usefulness of the proposed technique in accurate performance prediction of mesh reflector antennas with complex weave patterns

Equivalent Strip Width for Cylindrical Wire for Mesh Reflector Antennas: Experiments, Waveguide, and Plane-Wave Simulations

This paper presents the verification of the equivalent strip width for a cylindrical wire for mesh reflector antennas with experimental and numerical analysis and compares waveguide and plane-wave simulations. For experimental purposes, the transmission and reflection characteristics of copper strips and copper wires were measured. For numerical analysis, a model of the experimental setup was designed and simulated in High-Frequency Structure Simulator (HFSS). Comparing the measurement and HFSS simulated results confirmed that the numerical model was accurate. Using HFSS, it was verified that the equivalent strip width for a cylindrical wire is almost twice (~1.89) the wire diameter (for an infinitely thin strip) for typical mesh reflector structures. A periodic strip model was simulated both in HFSS and periodic Method of Moments (MoM) using the plane-wave incidence at different angles and the transmission and reflection characteristics were determined. The effects of the thickness of the strip, angle of incidence, and the spacing between the adjacent strips on the equivalence between the strip width and wire diameter were also studied. As the center to center strip spacing increases beyond 1.5lambda, the equivalent factor beta (strip width /wire diameter) approaches the classical factor of 2

Feasibility study on millimetre wave multi-gigabit wireless LAN system

We are aiming at creating a millimetre wave wireless LAN system with a speed of multi-gigabits per second. This paper describes the preliminary system design, focusing on practical implementation, and its enabling technologies together with the selection of methods and parameters.

Demonstration experiment of millimeter wave multi-gigabit wireless LAN system

We have developed a new 60-GHz band millimeter wave multi-gigabit wireless local area network (WLAN) system that achieves a throughput of more than 1 Gbps. The developed system consists of high-gain eight-sector antenna, physical layer (PHY) for orthogonal frequency multiple access (OFDM) modulation/demodulation, and media access control (MAC) for time and space resource control on point to multi-point (P-MP) communication. The performance of the developed system was evaluated in a room environment. As a result, we confirmed that developed system achieves a high throughput, which exceeds considerably that of current microwave-band WLAN systems based on IEEE802.11.

RF characteristics of spaceborne antenna mesh reflecting surfaces: application of periodic method of moments

We analyzed the mesh reflecting surfaces by using MoM with RWG basis and testing functions, which solve integral equations with periodic Greens function. Computed transmission losses approximately matched with the measured ones, even though our surface-patch models had single strip width. Detailed analysis on the difference between computed and measured transmission loss is under study The analysis of transmission loss for various polarization and incident angles indicated that the electrical characteristics of single satin mesh were better than those of single atlas mesh.

Efficient Gain Optimization Techniques for Azimuth Beam/Null Steering of Inverted-F Multiport Parasitic Array Radiator (MuPAR) Antenna

The multiport parasitic array radiator (MuPAR) antenna is a compact low-profile beam-steering antenna, which is composed of two excited inverted-F elements and two parasitic elements with variable reactors. Although the MuPAR antenna seems to have a good potentiality to achieve full azimuthal beam/null steering performance, the detailed controllability of the beam and null has not been clarified yet. This is because the two different types of variables, which are excitation coefficients and reactance values, make the gain optimization problem complex and difficult. Thus, in this paper, we have first developed a generalized model of the inverted-F MuPAR antenna. For the accurate modeling, structural features of inverted-F antennas are taken into account, and also the closed-form gain definition for the MuPAR antenna is derived. The formulation enables us to efficiently obtain both excitation coefficients and reactance values with optimization techniques. Applying the model to both a gradient-based optimization and a particle swarm optimization successfully, the beam/null forming performances of the four-element MuPAR antenna is made clear. Through experiments including numerical calculations and measurements at 2.45 GHz, the validity of our model and precise formulation is confirmed.

Varactor-loaded inverted-F multiport parasitic array radiator antenna

In order to realize a compact low-profile antenna that can steer beam/null continuously in full azimuthal directions, this paper proposes a new configuration of beam-steering antenna with mutual coupling between inverted-F antenna (IFA) elements. The antenna array consists of two active and two passive IFA elements loading variable reactors, thereby realizing a low-profile antenna array within a small space. It is expected that the antenna possesses a high ability to form beam and/or null, since it behaves as both Yagi-Uda array and phased array. Furthermore, we derive here a general expression of equivalent weight [1] for multiport parasitic IFA arrays. Finally, the beam steering of the proposed antenna is demonstrated by the numerical simulation.

Bandwidth enhancement of coaxial line to post-wall waveguide transition using short-ended straight post in 60-GHz band

We have applied the bandwidth-enhancement technique to a transition between coaxial line and post-wall waveguide with a short-ended straight post. The straight post connected to the coaxial line works for not only impedance matching for input coaxial port but also impedance inverter between two cavities. The dual resonance behavior of the transition was confirmed by numerical studies. Using our bandwidth-enhancement technique, a transition with straight short-ended post was successfully designed for the waveguide slot-array antenna at 60 GHz. It can be concluded from our designed transition that the effectiveness of our bandwidth enhancement technique is verified.

Tapered Radial Fed Circuit and Varactor-Mounted Waveguide Switch for Millimeter-Wave Switched Sector-Beam Antenna

This paper describes the simulated designs of an improved radial fed circuit and a varactor-mounted waveguide switch, which are expected to play important roles in the realization of a millimeter-wave switched sector-beam antenna. The aim of this antennas development is to realize an ultra-high-speed gigabit-rate wireless LAN. In this paper, an eight-sector beam antenna is described. The radial structure is designed so that the input power from a unique RF port at the structures center can be sent to any one of the selected sectors with maximum power under the required bandwidth. The simulation results of the proposed tapered radial structure show that the bandwidth of S21, with an insertion loss of -1.0 dB in the frequency range of 59-66 GHz, is 5.4 GHz, which is the three times that achieved in our previous work. Basic study is also carried out on factors such as choke structure, switch position, and the losses caused by the dielectric and metallic materials as well as the parasitic components of the varactor of the proposed waveguide switch