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This study analyzed the channel capacity of multiple-input multiple-output (MIMO) reception by large-scale arrays at both ends in spatially correlated fading environments. The environments considered were Rayleigh fading for representing the non-line-of-sight condition and Nakagami-Rice fading for the line-of-sight condition. The transmission characteristics of massive MIMO were evaluated using the asymptotic eigenvalue distribution of a Wishart matrix composed of the channel matrix. The transmission scheme adopted here was eigen-mode multi-stream transmission that selected L from N streams of N-by-M (M ≥ N) massive MIMO. From the analysis, we determined that the effect of spatial correlation for the case of L/N being less than approximately 20% enhances the channel capacity, unlike spatial diversity operation. In this way, we clarified the effect of spatial correlation on channel capacity of massive MIMO quantitatively through asymptotic eigenvalue analysis. [ABSTRACT FROM AUTHOR]

Enhancement of service to closed spaces (independent spaces) via a repeater with several transmission lines is attracting attention as a means of expanding the service area of information transmission by MIMO. The propagation path in such environments becomes a multi-keyhole environment in the equivalent sense. The existence of a keyhole causes a reduction of communication capacity. However, in a multi-keyhole environment, the impact is reduced because multi-stream transmission becomes possible. In this paper, we propose a MIMO repeater system and a multi-keyhole model that realize repeater functions to a closed space while high-speed and high-reliability communication characteristic to MIMO are maintained. The eigenvalue distribution, average communication capacity, and average BER characteristics of the MIMO repeater channel are ascertained by computer simulations. The number of repeater antennas needed for relaying with the MIMO function maintained is determined. ©2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(10): 40–48, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20384 [ABSTRACT FROM AUTHOR]

In this paper, we propose a simple method for accurately calculating the probability distribution of the largest eigenvalue of the correlation matrix of a MIMO propagation channel in a Nakagami–Rice fading environment including direct signals. The results determined by the proposed approximation method were compared to the results of a computer simulation and exhibited accurate matches. We discuss the channel capacity in a Nakagami–Rice fading environment. In this environment, the largest eigenvalue clearly dominates, and maximum ratio combining transfers are clearly useful. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(11): 68–77, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20210 [ABSTRACT FROM AUTHOR]

By establishing a guard interval, the OFDM method shows excellent characteristics in a multipath environment. However, if the delay spreading exceeds that guard interval, intersymbol interference occurs. In this paper, we propose a method of extending the “equivalent transmission path model” to analyze the OFDM transmission characteristics in this kind of multipath environment in which the delay spreading exceeds the guard interval and show that the results obtained by using this method match the exact simulation results to a sufficient approximation precision. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(1): 1–10, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10131 [ABSTRACT FROM AUTHOR]

An environment is assumed in which a strong interference wave is suddenly incident. To produce an antenna robust to such an environment, a method is proposed in which an eigenvector beamspace adaptive array (EBAA) is formed by using the weight of the eigenvector for the first eigenvalue in the case of weak interference, but the weight of the eigenvector for the second eigenvalue in the case of strong interference. The performance of the interference suppression in the latter case (desired wave power ≪ interference wave power) is analyzed by numerical calculations and simulations. Also, this EBAA is superior in terms of configuration and performance to the well-known power inversion adaptive array (PIAA). Based on the results, a software antenna configuration method for real-time understanding of the propagation environment and adaptive switching of the algorithm is discussed. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(8): 20–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10099 [ABSTRACT FROM AUTHOR]

The advantages of subband signal processing adaptive array (SBAA) are the ability to perform parallel signal processing in each subband division and the substantial reduction in the total computational load. However, the price is not preventing a drop in performance, for example, the incorporation of delayed waves, and a countermeasure must be found. Therefore, in this paper, we propose introducing a scheme that inserts a guard interval (cyclic prefix), which is commonly adopted in Orthogonal Frequency Division Multiplexing (OFDM), into ordinary data transmission, and extracts the best possible performance of SBAA. We also evaluate the performance by a computer simulation. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(3): 1–8, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10055 [ABSTRACT FROM AUTHOR]

It has been known that an adaptive array antenna is effective for reducing frequency-depending selective fading, which is a problem in wide-band land-mobile communication systems. In an environment in which many delayed signals arrive, it is desirable to improve their SN ratio by using co-phase synthesis. There have been two types of adaptive array antenna for this purpose: an antenna based on time-domain signal processing using a TDL (tapped delay line), and an antenna based on frequency-domain signal processing using a fully reconfigurable filter. The latter has variations in its configuration, and is useful for making practical apparatus. However, its convergence process and behavior in a fading environment have not been clearly understood. In this paper, the performance and the advantages and disadvantages of adaptive array antennas based on various configurations with time- and frequency-domain signal processing are compared. It is found that combinations of some configurations improve their performance. The improvement in performance is also described. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(9): 35–42, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1117 Copyright © 2002 Scripta Technica [ABSTRACT FROM AUTHOR]

In the ITS (Intelligent Transport System), vehicle-to-vehicle communication to exchange information between vehicles and vehicle-to-road communication connecting vehicles and fixed network systems are important. The use of millimeter waves for vehicle-to-vehicle communication is being discussed. In this paper, in connection with vehicle-to-vehicle communication using millimeter waves, fundamental studies of fading due to road surface reflection, which is considered the most severe cause of degradation of radio wave propagation, are carried out. In addition, a quantitative evaluation of the effect of space diversity as a countermeasure for degradation of propagation is performed. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 85(1): 35–42, 2002 [ABSTRACT FROM AUTHOR]

For mobile communication antennas, it is important to form nulls in the radiation pattern so that the antenna does not interfere with other communication systems in transmission. In cases where the frequencies for transmission and reception are different, as in FDD (Frequency Division Duplex) systems, if the weighting in the reception mode is used directly for transmission when forming the radiation pattern adaptively during transmission, the null directions are deviated so that the transmission characteristics are degraded. In this paper, a receiving and transmitting adaptive null beamforming algorithm is proposed in which a digital multibeam forming network for propagating signals with wide fractional bandwidths, having radiation patterns not dependent on the frequency, is used for weight calculation. Since the radiation patterns of multibeams are almost identical at the transmission and reception frequencies, almost identical null depth can be obtained for both transmission and reception after convergence. By means of computer simulation, it is confirmed that the nulls are formed in the incident directions of the interference signals in both transmission and reception and that the null depths are almost identical. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(11): 26–34, 2001 [ABSTRACT FROM AUTHOR]

Discusses a study which pursued the improvement of usability of the equivalent radio transmission-path model to assess bit error rate due to intersymbol interference in a Nakagami-Rice fading environment. Overview of the equivalent transmission-path model; Similarity and scaling of bit error rate maps; Frame error rate.

Describes a study which proposed a wideband beamspace adaptive array that uses far-infrared radiation (FIR) fan filters to construct a multibeam forming network. Details on the proposed spectral transformations; Design procedure for fan filters; Conclusions.

Presents information on a study which derived a formula for spatial correlation characteristics of wideband signal transmission in a Nakagami-Rice fading environment. Difference in spatial correlation characteristics between Rayleigh fading and Nakagami-Rice fading; Spatial correlation characteristics for narrow-band signal; Conclusions.

A fiber-type optical phased array antenna is proposed as a new configuration of phased array antennas operating in the optical frequency domain. The proposed antenna consists of fibers that connect an optical beamforming network consisting of integrated optical waveguides to an array antenna consisting of microlenses as the element antenna. High-speed two-dimensional optical beam steering can be achieved by reducing the relative phase fluctuation between element antennas and the generation of the grating lobe. In an experiment on the three-element fiber-type optical phased array antenna, three 1 × 2 variable power dividers and four variable phase shifters are integrated on a LiNbO3 substrate as the optical beamforming network, and graded-index-fiber (GIF) lenses are used as the antenna elements. These components are connected through polarization-maintaining fibers (PMF). The 3-dB bandwidth of the integrated variable phase shifter is from dc to 924 MHz, and the optical beam steering range of the three-element array is 0.2°; they are arranged in a triangle. The parameters of the GIF lens are optimized and it is estimated that at the maximum gain coefficient a grating lobe level of –14.5 dB and a gain coefficient of 0.815 can be obtained. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(8): 42–51, 1999 [ABSTRACT FROM AUTHOR]

Presents a land mobile-satellite services (LMSS) propagation channel model for assessment of the effect of a satellite diversity scheme. Number of states the general fading environments for LMSS are classified into; Developmemt of a fading channel model; Validation of the model; Calculation of the satellite diversity effect based on the model.

Presents a equivalent transmission-path model for calculating irreducible bit error rate (BER) due to intersymbol interference in frequency-selective Nakagami-rice fading environments generally applicable to phase-shift keying systems. Concept of key parameters; Equivalent transmission-path model; Floor predictions on BER.

It is expected that mobile-radio systems will play an important role in realizing general personal communication networks through ISDN. In the near future, the so-called mobile ISDN era, it is necessary to have come mon performance objectives between mobile radio links and fixed (or fiber) links and have a common assessment method for data transmission quality. In this paper, based on the ITU-T definition, unavailability statistics are examined in mobile-satellite systems which are characterized by low margin systems. The characteristics of signal degradation due to propagation impairments in maritime, aeronautical, and land mobile sateffite services are examined. Through this analysis, the importance of differentiation between unavailability and 'signal degradation in available time' is emphasized when the digital signal transmission quality is evaluated. [ABSTRACT FROM AUTHOR]

Onboard resource sharing (ORS) is a method wherein, for increasing effective isotropically radiated power, surplus satellite resources (radiated power or time slots in TDMA) are used to maintain communications quality in areas affected by rain attenuation. This paper analyzes simultaneous occurrence rates of rain over a wide area using Automated Meteorological Data Acquisition System (AMeDAS) data (1 hr rain rate data at approximately 1300 locations in Japan provided by the Japan Meteorological Agency). An ORS system is proposed using AMeDAS data as dynamic information for controlling satellite transmission power. Then a control simulation is performed by using actual reception intensities of satellite signals and rain rate information derived from AMeDAS data at corresponding times. The effect of the proposed ORS system is demonstrated in compensating for rain attenuation. From these results it was confirmed that the forementioned compensation provides a saving of about one-third compared to the case where unavailable time is not compensated. [ABSTRACT FROM AUTHOR]

The unavailable time percentage and the SES (severely errored seconds) occurrence rate within available time was investigated according to CCITT definition using Ku band low elevation angles satellite system data obtained mainly at the Yamaguchi station. As a result, the CCITT unavailable time percentage was found to agree with the cumulative signal attenuation time percentage as determined by the traditional statistical treatment. This agreement held even in the case of low elevation angles. Further, the ratio of SES occurrence rate within CCITT available time to the conventional cumulative signal attenuation time percentage was found to be much larger than in the case of high elevation angles, and to have a high correlation with tropospheric scintillation. An experimental formula was developed for this ratio as an index of the degree to which tropospheric scintillation affects overall signal deterioration. Using this formula a formula was developed to predict the SES occurrence rate within CCITT available time from the index and the traditional cumulative signal attenuation time percentage. Also, it was confirmed that there was good agreement between the predicted value and the experimental value. [ABSTRACT FROM AUTHOR]

In future maritime mobile-satellite systems with low-G/T ship-Earth stations, qualitative understanding of multipath fading due to sea surface reflection is very important, particularly when operating at low elevation angles. In this paper, multipath fading in very rough seas (wave height of more than 3 m),which has not been treated so far, is investigated by taking into account the effect of smaller-scale waves superimposed onto the significant wave. Based on this model, we clarify theoretically the wave height dependence of 1.5 GHz multipath fading caused by reflected waves from the sea surface, and compare it to the results of experimental observations. Finally, we refer to the frequency dependence of fading based on the model. [ABSTRACT FROM AUTHOR]

Development of small marine antennas has a very important role in the maritime satellite communications with small ships, especially for Japan which has a relatively large number of small fisherboats. As the satellites become larger in size in the future, the shipborne antennas will tend to become smaller. We propose a control method for the antenna mount against ship motions to assure pointing the communication satellite. The two-axis EL/AZ mount has is near the control limit for avoiding twisting the cables. We have developed an algorithm to reduce the pointing errors within the pitching amplitudes of the ship. The principle and the experimental results of this system are described. [ABSTRACT FROM AUTHOR]

When maritime satellite communication is conducted at low elevation angles, fading due to sea surface reflection becomes a problem. For suppression of the fading, space diversity and frequency diversity may be employed. This paper studies the correlation characteristics of multipath fading due to sea reflection in the spatial and frequency domains in L-band operation. This is important in investigating the diversity effect. First, from the theoretical model of sea surface reflection, the correlation scattering cross sections of the coherent and incoherent components of the reflected wave are obtained. Next, from numerical calculations, the correlation characteristics are obtained with the antenna elevation angle and the height over the sea as the parameters. It is found that in space diversity good diversity effects can be expected from two antennas separated in the vertical direction by about 40 cm. It is also seen that fading reduction cannot be expected with frequency diversity in the case of narrowband communications such as in maritime satellite communications. The effects of various fading reduction measures in the up and down links are considered. [ABSTRACT FROM AUTHOR]

Discussed here are real-valued signal analysis and wireless baseband transmission, a system for transmitting baseband signals directly from an antenna, and transmission characteristics under a multipath environment. The field of wireless transmission generally handles band signals in which information rides on a carrier wave, and therefore signal analysis is not the direct analysis of real high-frequency signals (real-valued signals) and is performed with a system expressed using complex numbers, called an equivalent baseband system. However, wireless baseband transmission is based on a transmission system which does not use carrier waves and cannot be handled with an equivalent baseband system. Consequently, it is necessary to have a system of real-valued signal analysis for handling baseband signals, which are real-valued signals, without additional processing. The BER (bit error rate) was used as the standard for evaluating transmission characteristics under a multipath environment of wireless baseband transmission using measured channel characteristics with that algorithm. With a computer, the BER characteristics were found by varying the reflection coefficient, number of delay symbols, the ratio of direct wave power and reflected wave power, and the number of reflected waves. As a result, it was clear that the dominant factor in a multipath environment is the ratio of direct wave power and reflected wave power. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(10): 9–22, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20347 [ABSTRACT FROM AUTHOR]

Orthogonal frequency division multiplex (OFDM) modulation systems can completely prevent intersymbol interference due to multipath propagation by providing a guard interval which is longer than the maximum delay hereafter we call “delay spreading.” In an environment in which the delay spreading exceeds the guard interval, on the other hand, intersymbol interference occurs. This study considers a MIMO-OFDM system in which a MIMO configuration with high diversity gain is introduced into the OFDM modulation scheme, and discusses the transmission characteristics of maximal ratio combining transmission (single-stream transmission). It is shown that the MIMO-OFDM system is less affected by intersymbol interference due to the delay, even if the delay spread exceeds the guard interval, and that good performance is achieved. It is also shown that the channel response which is required in real-time control can be estimated with sufficient accuracy. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(12): 29–39, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20209 [ABSTRACT FROM AUTHOR]

In this paper, a typical mobile communication environment is assumed and the eigenvalue distributions of the correlation matrix of a MIMO channel with the spatial correlation of the multipath taken into account are studied by simulation. Based on this study, a simple method is proposed for accurately deriving the probability distribu- tion of the largest eigenvalue of the correlation matrix. The proposed approximation equation is compared with simu- lation results and good agreement is obtained. In order to understand the information transmission capability of MIMO in a multipath fading environment with spatial correlation, the proposed equation is used for studying the effect of the spatial correlation on channel capacity. Finally, the digital transmission characteristics (relationship be- tween the BER and the CNR) with correlation taken into account are obtained. [ABSTRACT FROM AUTHOR]

Examines the use of spatial optical signal to propose an array antenna for multibeam reception with a beam-forming network. Conversion of the microwave signals to optical signals; Application of optical spatial Fourier transformation; Employment of optical integrated circuit.

CMA (Constant Modulus Algorithm) adaptive arrays are considered a promising method in mobile communications to mitigate multipath fading and to suppress co-channel interference signals. However, since a CMA adaptive array assumes no a priori information of the desired signal, it is difficult to separate and combine the multipath rays of the desired signal. Therefore, when CMA is applied, the input signal power of the multipath rays cannot be efficiently utilized. Moreover, since suppressing the multipath rays requires many degrees of freedom (DOFs) of the array, the array system becomes complicated. In this paper we propose the subband CMA adaptive array which enhances the signal correlation between the multipath rays in each subband, as such the multipath fading effect can be greatly mitigated. By using this method, the multipath rays of the desired signal are equalized and combined, whereas an interference signal with multipath rays can be suppressed by using a single DOF. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(11): 43–54, 2000 [ABSTRACT FROM AUTHOR]

In this paper, we propose a beamspace adaptive array antenna for broadband signals with a wide fractional bandwidth. The proposed beamspace adaptive array antenna has a multiple digital beamforming network that preserves spectral components of input broadband signals by using tapped-delay-line circuits. Coefficients of the tapped-delay-line circuits are determined such that each broadband digital beamforming network has the same phase characteristics, and the beam pattern including sidelobe and null characteristics is virtually frequency independent. A few adaptive weights, which are linear combination coefficients of the selected broadband beams, follow a beam selector. The number of adaptive weights for the proposed adaptive array is considerably less than that of an element space structure with tapped-delay-line circuits. We demonstrate by computer simulation that interference suppression by the proposed beamspace adaptive array is as good as that of an element space adaptive array and that it has much faster convergence. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(10): 38–48, 1997 [ABSTRACT FROM AUTHOR]

This paper presents a new estimation technique with $K$ -order expressions for evaluating the maximum electric fields radiated from multiple-antenna transmitters such as those in mobile phones, WiFi access points, and cellphone base stations. The need for $K$ -order estimation to provide precisely estimated electric fields, then develop useful expressions for the estimation and validate the estimation model numerically and experimentally is explained. Fundamental concepts of estimation and detailed electric field formulas, applied to various measurement systems using vector or scalar E-field probes, are presented. Several validations are also illustrated. As a result, it is verified that $K$ -order estimations significantly reduce the differences between the estimated and simulated/measured E-fields [or specific absorption rates (SARs)]. Investigations on the maximum electric fields of two antennas operating at 2.5 GHz in an ordinary room show that the maximum difference between the electric fields obtained by conventional estimations and calculations can be 8.5%, which is suppressed to below 0.24% and 0.02% by 2- and 3-order estimations, respectively. Similarly, in evaluations of the SAR of a three-antenna configuration, the maximum difference between the estimated and calculated SARs of about 5% obtained by conventional estimations is reduced to 0.1% or 0.01% by 2- and 3-order estimations, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates an intervehicle communication method as a safe driving support system for intersection collision avoidance warnings. In this kind of system, realization of highly reliable communications in the physical layer is an absolute requirement. As a result, we propose a new MIMO-STBC (Space-Time Block Coding) method based on intersection propagation channel characteristics. MIMO transmission characteristics are determined by the propagation channel characteristics. First, we use a ray-tracing method simulation to clarify the propagation channel conditions, and then model the intersection propagation channel. We use the characteristics of this propagation channel to propose a MIMO-STBC method that utilizes decision feedback channel estimation, and verify the effectiveness of the proposed method in computer simulations. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 1–15, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20400 [ABSTRACT FROM AUTHOR]

Adaptive arrays for spatiotemporal signal processing are expected to be effective multipath measures in future high-speed mobile communications systems. However, a problem is the tremendous computational load in a hardware implementation because the number of weights that are adaptively controlled becomes extremely large. Therefore, the key to its practical use is to reduce the computational load. In this paper, an adaptive array for processing subband signals that can substantially reduce the computational load was implemented in hardware by using a commercially available digital signal processor (DSP). First, we illustrated the scale of the hardware by the number of DSPs needed in each unit that performed the required signal processing. Next, we built a simple multipath environment of two waves in an anechoic chamber and performed experiments to demonstrate the basic performance and verified that performance nearly equal to the theoretical values was obtained. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(10): 19–30, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1122 [ABSTRACT FROM AUTHOR]

This paper discusses a land-mobile satellite experiment and its results, on a self-beam steering array antenna implemented by using a digital beam forming (DBF) technique with a compact digital signal processing circuit using ASICs. This antenna allows automatic and open-loop beam steering toward an unknown signal arrival direction by simple spatial signal processing. Beam-space maximal-ratio combining was employed as the steering algorithm. The antenna was mounted on a test van and the basic performance was demonstrated by receiving a signal in the 1.5-GHz band in a land-mobile satellite channel with the Japanese ETS-V satellite. The experiment showed stable beam steering and automatic tracking under real mobile conditions. Reacquisition of the signal arrival after shadowing was also fast enough. Moreover, steering for the direct signal arrival was not affected even with the arrival of a strong, reflected multipath signal. The possibility for optimal combination of multipath signals was demonstrated by multidirectional steering patterns. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(7): 1–13, 1998 [ABSTRACT FROM AUTHOR]

With a view to application to array antennas for mobile stations in a mobile satellite communication system, a method is proposed for configuration of a receiving diversity array antenna acquiring a communication beam quickly and tracking with stability by means of the digital beam forming (DBF). In this method, an active array is assumed. The receiving phase difference between the antenna elements is detected by digital complex operation for the received baseband signal. Based on this phase difference, the phases of the antenna elements are made in phase in a relative sense so that equal gain or maximal ratio combining is accomplished. As a result, the main beam can be formed in the direction of the arriving wave. In addition, in the case of maximal ratio combining the radiation pattern is oriented toward the multipath arriving waves so that communication quality is improved as the beams are further combined in phase. In this paper, the effectiveness of the present method is demonstrated by the numerical simulation assuming a mobile communication environment with band-limited QPSK signals. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(10): 88–100, 1997 [ABSTRACT FROM AUTHOR]

A digital beam-forming antenna (DBF antenna) used for mobile wireless communications has drawn considerable attention in conjunction with device technology advances. Effective use of the frequency spectrum by means of multibeam antennas and adaptive antennas for mobile communications has also been discussed. With regard to DBF antennas, an offline trial process by means of a workstation and trial fabrication of a general-purpose DSP have been reported. However, to satisfy the high functionality and high-speed operation required for a DBF antenna, an application specific integrated circuit (ASIC) for the digital signal processing section must be realized. The ASIC described here is configured from a digital signal processor that uses a gate array called an FPGA, which can be developed by the user. The gate size necessary for circuit configuration obtained by a trial fabrication is explained and performance for a one-chip ASIC realized with a similar design is discussed. Experimental results are shown for real-time multibeam forming in a large anechoic chamber using the trial system. Confirmation of automatic tracking by means of maximum received beam selection is also shown. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80 (2):100–111, 1997 [ABSTRACT FROM AUTHOR]

Presents a study which described Japan's wide-band millimeter wave (MMW)/optical-network application. Indepth look at Advanced Telecommunications Research Institute's projects; Methodology used to conduct the study; Results of the study.

In digital beamforming (DBF) antennas, received propagation signals are first converted down into baseband inphase and quadrature signals, then DBF signal processing is done. We propose a method for designing two-dimensional (2D) digital filters utilized in such DBF networks to handle the signals with wide fractional bandwidths up to 40%. First, we consider the relationship between DBF and its 2D normalized frequency description. Here, we show that 2D complex coefficient digital filters with nonsymmetric characteristics are necessary to form broadband beams. Next, based on this consideration, we describe the proposed method, which combines spectral transformation and a window method. Note that approximation is achieved such that the beam pattern, including its sidelobe characteristics, from the resulting broadband DBF network is virtually frequency-independent. As a result, it has become possible to design DBF networks suitable for a multibeamforming network for use in the broadband beamspace adaptive array antenna proposed in Sekiguchi, Miura, and Karasawa [9]. © 1998 Scripta Technica. Electron Comm Jpn Pt 3, 81(3): 22–34, 1998 [ABSTRACT FROM AUTHOR]