The paper describes the experimental results of a three beam antenna with a paraboloidal reflector for application to a wind profiler radar. In order to determine the position of the primary radiators, the ray trace method is introduced. The radiation characteristics of the antenna with a paraboloidal reflector are compared with the radiation characteristics of the antenna with the reflector-lens, as proposed before. The result shows that the antenna with a conventional paraboloidal reflector yields the same gains and a little bit higher level of side-lobes compared with the antenna having the reflector-lens.
Remote sensing technology using artificial satellites has become an important part of meteorology, oceanography, the fishing industry, agriculture, etc. In order to get remote sensing data directly, a ground receiving system for meteorological satellites is going to be built on our campus. This paper describes the system configuration and the experimental results of the radiation pattern of the antenna obtained by using the radio wave from the satellite NOAAs.
In this report, a method and experimented data of active integrated antennas using a quasi-optical technique is demonstrated which plays a significant role for a near-future personal communication system. In order to investigate interaction between adjacent planar antennas two active integrated antenna arrays were fabricated and to predict characteristics of the array under the steady state operation the large signal analysis was carried out in the way of establishment of a large signal FET model from measured small signal FET S-parameters. In addition, mode stabilization of the way was realized by setting dielectric resonators of periodic boundary of the linear away. From the consideration, it is believed that fundamental data for a monolithic active integrated antenna array were obtained.
Recently, with popularizing car TV, it is required to develop a car TV antenna, which is small in size and high in efficiency and joins an FM radio antenna. This paper describes a basic study of a mobile car antenna for receiving television and FM radio.
When we watch TV program, interference appears on the screen due to unwanted radiowave propagation through receiving antennas and sometimes causes unacceptable degradation of receiver performance. The authors proposed an LMS adaptive Yagi-Uda array antenna for TV reception to surpress such an interference. Its characteristics were investigated for narrow band signals. In this paper, we study this antenna system in consideration of TV signal bandwidth. The method of moment is used to take mutual coupling effects into account and to obtain received signal at the antenna output. As a result, the proposed antenna was influenced by the bandwidth of the interference signal, as the arrival direction of an interference signal "ψ" became larger, but it was obtained that the proposed antenna could improve the output DUR more than 10[dB] in comparison with the conventional eight element Yagi-Uda antenna for VHF all-band reception.
OFDM (Orthogonal Frequency Division Multiplexing) is a useful digital modulation method for DTTB (Digital Terrestrial Television Broadcasting) systems and superior to the multi-path environment. SFN (Single Frequncy Network) using OFDM has been studied for DTTB network in order to improve frequency utilization efficiency. In this paper, service area is estimated when SFN is applied to real broadcasting environment in Japan.
Recently, in the system that is used to observe multiole points with video transmission, the system is hoped that observe a point by arranging portable terminal on flexible term. Because the conventional system is used to arrange fixed terminal. Therefore, we developed information free access system thatis enable to change the observation point where the portable terminal connects with optioal tap arranged along transmission link. Number of optioal taps which is possible to transmit is dominated by transmission loss. Acoording to caloulated results, it is feasible to arrange 30 optical tap along 30km optical transmission link.
Fabrication method of electromagnetic shield and radio absorption in (γ-Fe_2O_3/T_1O_2) composite materials for low frequencies are studied. Electromagnetic permittivities and permeabilities in (γ-Fe_2O_3/T_1O_2) composites are discussed for optimum trial design of electromagnetic shield and radio absorption sample that are indispensable for protection of electronic equipment from external noise.
The absorbing condition of single layered lossy dielectric type radio absorptive materials are considered in a UHF band. The material is used acrylonitrile-butadiene rubber which is called as nitrile rubber and graphitized carbon. The material is made after 10 hours dispersion. The characteristics of the absorptive materials are measured and optimum condition to apply for the UHF band which is including the frequency applying personal handy phone system (PHS) is considered. Furthermore, the developed lossy material can be used as dry phantom models to simulated human tissues. The dry phantom material developed here is very stable which can repeatedly used without changing its characteristics. The most suitable weight ratio of graphitized carbon dispersed in the nitrile rubber is also shown in this paper to realize phantom models of low water content medium as human fat and bone, and those of high water content medium as human muscle and skin.
This paper proposes a new narrow band interference canceler for a wide-band CDMA system which shares a frequency band with a narrow-band TDMA system. The proposed canceler, which is based on the complex multi-rate filter bank technique, can not only eliminate known narrow-band interference, but also estimate the number and the frequency of unknown interference. The proposed canceler performs as an adaptive notched filter after the identification of the positions and the number of the narrow band interference based on a tree search algorithm. Computer simulation results show the proposed scheme can estimate and eliminate the interference effectively.
This paper proposes a new multi-rate filter bank based group demodulator for multi-channel TDMA micro-cellular systems. The proposed demodulator first searches occupied channels by comparing two output signal powers at each stage of the multi-rate filter bank, and then demodulate the signals. This paper discusses the search error probabilty and shows an optimum detection threshold to minimize the error probability.
The advanced satellite broadcasting system in the 21GHz band is expected to realize the future multimedia service. To establish this system, the rain attenuation mitigation technologies are very important. As one of the mitigation technologies, the time-diversity technology has been proposed. This paper shows the effect of the time-diversity by using the AMeDAS data, and this paper also proposes an estimation method of the time-diversity gain as a function of rain attenuation, the cumulative time percentages and time delay of the broadcasts.
The electric field distributions inside of some building structures consisting flat plates in AM radio wave are experimentally studied using scale models of 1/300. The models have simple shapes such as a flat plate, inverted L, chanels etc. From the results of experiments, it is noticed that the field strength inside of the buildings is greatly reduced because of the effects of conducting plates. Especially, the building like a garage shows a high shielding effectiveness over 20dB. The results obtained here give us some knowledge for estimating the shielding effectiveness of the building structures using a theoretical analysis.
The VHF television broadcasting waves from Tokyo tower was received in two different region of Gunma prefecture. The reciving signals level variation of fading was mostly that of about several dB in winter, but summer there was also large one reaching 30dB. This report describe resulting from our investigation of the received signals level over a long period of time.
For non-parallel two transmission lines of finite length, crosstalke coupling is caused by external electromagnetic fields due to the line sections and the line terminals. The external electric and magnetic fileds can be estimated as the current and voltage sources respectively on the transmission lines from the Maxwell's equations, where those equivalent sources are expressed in terms of vector potential. A four-port network model is proposed by using a circuit concept. The crosstalk analysis may be done by applying the network model to the line system in various configurations.
In this paper, measurement results of an illuminated MESFET characteristics, demonstration of the illuminated MESFET model and an investigation of physical phenomena in an illuminated MESFET are reported. From the investigation of the experimental data, a novel illuminated MESFET model was proposed and its output conductance of an illuminated MESFET was modified with a series capacitance. From this consideration, fundamental data for a design of an illuminated MMIC oscillator were obtained and it is believed to be possible to design a light-weight low-cost, high-efficient and high-speed optical-millimeter wave transducer.
A design method to realize the large modal birefringence and the wide single-polarization bandwidth is investigated for the optical fiber with hollow pits outside an eliptical core. When the relateve index difference of cladding was 0.5%, the modal birefringence of 5.63×10^<-4> and the sigle-polarization bandwidth of 77.8nm were obtaind from numerical analyses.
An optical SCM cable TV system is one of the most promising means for accommodating various kinds of new digital broadband services in addition to conventional cable TV services. The SCM scheme involves, however, the serious drawback of clipping-induced impulsive distortion, which spreads over the wide frequency range and may degrade the BER performance of digital channels. This report presents some experimental results, where the accuracy of the sub-carrier frequencies varies. We found that the frequency accuracy is one of the main factors that characterize the clipping-induced impulsive distortion infecting the digital channel performances. This factor was not considered in previous approaches.