Jun-ichi Takada

A reflection cancelling slot set in a linearly polarized radial line slot antenna

A radial line slot antenna (RLSA) is a high-gain and high-efficiency planar antenna. A linearly polarized RLSA (LP-RLSA) is attractive for applications of various subscriber radio systems. However, the slot arrangement for linear polarization gives rise to serious reflection from slots, which disturbs the normal antenna operation. A new LP-RLSA slot design is presented where reflection canceling slots are added to the conventional ones; four slots form one slot set as a unit radiator of linear polarization. The experiments confirm the design: the antenna return-loss is improved from -2 to -10 dB. Antenna efficiencies of 48 and 54% are measured for 400 and 600-mm phi antennas, respectively. This is the first report of the normal operation of LP-RLSAs. >

Cluster Properties Investigated From a Series of Ultrawideband Double Directional Propagation Measurements in Home Environments

Results from double directional ultrawideband (UWB) channel sounding in a wooden house are described. The double directional channel sounder estimates directional information at both ends of the link, so that we can separate antenna directivity from the channel sounding results. We investigated the dominant propagation mechanisms by introducing cluster analyses. The detected propagation paths from the channel sounding were first classified into clusters in the angular-delay domain, and then properties of the clusters such as standard deviation of path positions, dynamic range of path power, and power distribution of clusters were derived. From the results, we discussed the similarities and differences between the measurement environment and the physical propagation phenomena. Finally, different types of scattering losses of the propagation paths were derived and modeled. The results from sounding and analysis contribute in the development of UWB propagation models and can be used in UWB propagation simulations

Double Directional Ultra Wideband Channel Characterization in a Line-of-Sight Home Environment

This paper introduces the concept of measuring double directional channels in ultra wideband (UWB) systems. Antenna-independent channel data were derived by doing the measurements in a wooden Japanese house. The data were useful for investigating the impact of UWB antennas and analyzing waveform distortion. Up to 100 ray paths were extracted using the SAGE algorithm and they were regarded as being dominant. The paths were then identified in a real environment, in which clusterization analyses were done using the directional information on both sides of the radio link. Propagating power was found to be concentrated around the specular directions of reflection and diffraction. This led to the observation that the spatio-temporal characteristics of extracted paths greatly reflected the structure and size of the environment. The power in the clusters indicated that the estimated 100 paths contained 73% of the total received power, while the rest existed as diffuse scattering, i.e., the accumulation of weaker paths. The practical limits of path extraction with SAGE were also discussed. Finally, we derived the scattering loss and intra-cluster properties for each reflection order, which were crucial for channel reconstrucion based on the deterministic approach.

Channel capacity of a handset MIMO antenna influenced by the effects of 3D angular spectrum, polarization, and operator

The purpose of this study is to evaluate a handset MIMO antenna under practical use conditions, involving multipath radio wave propagation and the influence of the body of the user. To this end, a Monte Carlo computer simulation has been carried out to investigate the distribution of eigenvalues and channel capacity

Measurement Techniques of Emissions from Ultra Wideband Devices

This paper describes the measurement techniques of emissions from UWB devices discussed in ITU-R task group (TG) 1/8 to study the compatibility between ultra-wideband (UWB) devices and radiocommunication services. This paper also provides the background idea behind the measurement methods, as the final output of the discussion, i.e. ITU-R Recommendation, will not contain any citations to the references, nor any educational description of the theoretical background.

Measurement of Time-Varying MIMO Channel for Performance Analysis of Closed-Loop Transmission

A real-time multiple-input multiple-output (MIMO) channel measurement system was implemented by using a 4times4 MIMO software defined radio (SDR) testbed. A target application of this system is to evaluate realistic performance of closed-loop MIMO transmission in time-varying channels at 5 GHz band. The results of indoor measurements showed that feedback delay of the closed-loop transmission causes severe degradation of channel capacity, and an interference canceller in eigenbeamspace is indispensable in achieving the benefits of channel state information (CSI) feedback

Wideband Directional Radio Propagation Channel Analysis Inside an Arched Tunnel

To analyze the radio propagation channel inside a tunnel, a wideband directional measurement campaign was managed inside an arched tunnel which was constructed to be used for a highway. Using a wideband channel sounder equipped with a cylindrical dual polarized array at the receiver (Rx), the spatio-temporal characteristics of the received propagation paths could be estimated by means of a super-resolution estimation algorithm. The dominant scatterers are classified into 5 classes based on the structure of the tunnel as follows: ceiling, light-frames, walls, sidewalk or ground. The power contribution and cross polarization ratio for different Rx positions along the tunnel are compared

Ultrawideband spatio-temporal area propagation measurements and modeling

Ultrawideband (UWB) spatio-temporal area propagation measurement and modeling was performed for accurate characterization of spatial UWB channels. The area propagation measurement acquires as much channel data as possible in one specific environment, e.g., in an office room, to characterize the variation of the dominant scattering process against antenna position displacement. The spatio-temporal channel modeling includes propagation path detection, parameter estimation, and path tracking. A simple spatio-temporal beamforming was considered for path detection and parameter estimation. The path tracking is capable of distinguishing meaningful propagation paths from insignificant ones, and also of clustering propagation paths. The modeling results agreed very well with physical scattering processes, and therefore, the method was proven to be reliable.

BER Measurement on a Handset Adaptive Antenna Array in a Rayleigh-Fading Channel by a Variable-XPR Spatial Fading Emulator

This paper presents an empirical study of the bit-error-rate (BER) performance of a handset adaptive antenna array in a Rayleigh-fading channel with a cross-polarized signal generated using a variable cross-polarization power ratio (XPR) spatial fading emulator. We have investigated the BER characteristics of a handset adaptive antenna consisting of a 1/4-wavelength monopole antenna and a planar inversed-F antenna (PIFA) as a function of XPR. It can be concluded that the measured average BER of an adaptive antenna array with both theta and phi components has an excellent BER performance in a multipath propagation environment with a cross-polarized component

Overview of Research, Development, Standardization, and Regulation Activities in NICT UWB Project

This paper presents an overview of research, development, standardization and regulation activities on ultra wideband (UWB) technologies in National Institute of Information and Communications Technology (NICT). NICT started a project on UWB technologies since 2002, and organized UWB consortium in cooperation with more than 20 companies and 7 universities in Japan. Up to now, we have been conducting numerous UWB R&D including the following main works: i) key technology development such as MMIC chips, antennas and other devices, ii) measurement and channel modeling for UWB signal propagation, iii) standardization in international activities of IEEE 802.15, ITU-R TG1/8 as well as in a national regulatory committee of Ministry of Internal Affair and Communications (MIC). The UWB systems we have studied occupy frequency bands range from microwave band (3--5 GHz) to quasi-millimeter wave band (24--29 GHz). Various prototype UWB systems including multi-functional terminals have been developed. The output of NICT has been succeeded by industrial parties with with national and international standardization and regulation.