Kunitoshi Nishikawa

Proposal of millimeter-wave holographic radar with antenna switching

This paper proposes a millimeter-wave holographic radar with a simple structure for automotive applications. The simplicity can be realized by switching both transmitting antennas and receiving antennas. Also, a super resolution technique is introduced for the detection of angular positions in the proposed radar. The radar developed experimentally has accomplished an azimuthal angular resolution of less than 2 degrees and an azimuthal field of view (FoV) of more than 20 degrees simultaneously.

Modified H-shaped antenna for automotive digital terrestrial reception

A modified H-shaped antenna is proposed for automotive digital terrestrial reception. The antenna is analyzed by the method of moments. The antenna has the feature that a figure-8 radiation pattern is rotated with increasing frequency. Four symmetrically mounted antennas at the top of the front and rear windows of a car have gain to the sides of the car as well as to the front and rear directions. The VSWR is less than 3 from 470 to 710 MHz since the antenna has three resonant modes. Measurement results for a single prototype antenna agree with the calculation results. The reception system adopts an adaptive array based on the maximal ratio combining (MRC) method. A near omnidirectional pattern was obtained in a plotted pattern of steered beam in the horizontal plane with the mounted prototype antennas.

Radar cross section for pedestrian in 76GHz band

This paper describes the results of our evaluation of a pedestrians radio wave reflection characteristics. The reflection characteristics of radio waves from a pedestrian were measured as part of the effort to improve the pedestrian detection performance of the radar sensor. A pedestrians radio wave reflection intensity is low, at about 15-20dB less than that of the rear of a vehicle, and can vary by as much as 20dB. Evaluating these characteristics in detail is a prerequisite to the development of a radar sensor that is capable of detecting pedestrians reliably.

Development and field experiments of phased array antenna for land vehicle satellite communications

A planar phased array antenna and a new beam tracking system have been developed for land vehicle satellite communications. Field experiments have been conducted with the ETS-V satellite to confirm that the beam tracking system functions very well. As a result, it was found that the beam was maintained toward the satellite with a pointing error of 15 degrees , and the variation of received signal level due to tracking error was less than 2 dB.<<ETX>>

Maximum likelihood decoding for wavelet packet modulation

The multi-carrier modulation (MCM) technique is an attractive approach for high-speed digital radio communication systems in order to achieve a high spectral efficiency and to combat the frequency selectivity of the channel. Orthogonal frequency division multiplexing (OFDM) is a kind of MCM technique. Wavelet packet modulation (WPM) is another kind of MCM technique using the wavelet transformation instead of the Fourier transformation to multiplex information symbol sequences. In this paper we propose a maximum likelihood decoding method for WPM without coding before transmitting the signal. The proposed method performs maximum likelihood sequence estimation by utilizing a signal obtained in an intermediate stage of the demultiplexing process. Then, bit error performance under a flat fading channel and frequency-selective fading channel is evaluated by computer simulation. According to the results, the proposed method can improve the bit error performance in the region of high Doppler frequency.

Mobile antenna system for direct broadcasting satellite

A television broadcasting service via a direct broadcasting satellite (DBS) is already operational in Japan with many residential subscribers. In addition, many people want to watch the DBS broadcasting even in cars, because DBS broadcasting has advantages over terrestrial television broadcasting such as high quality, simultaneity, and wide coverage. Several mobile antenna systems for the DBS have been developed previously. These systems have a high performance for receiving, but there is a problem that these systems are still too tall to be installed on a car. Therefore, we have reduced the height of the antenna system, and have realized a small and extremely low-profile mobile antenna system that is mountable on a car. This paper presents an outline and features of the antenna system developed.

Study of on-glass mobile antennas for digital terrestrial television

Digital Terrestrial Television (DTV) services began in Japan in December 2003. This paper proposes a novel on-glass antenna for mobile reception of terrestrial television. The gain of the proposed antenna is 4.7 dB higher than commercial monopole antennas when installed on a vehicle. Other merits of this antenna are a broad input impedance bandwidth across the UHF band (470-710 MHz), and the fact that it does not spoil vehicle appearance. Field experiments have confirmed that a diversity system using four of the proposed antennas is capable of mobile DTV reception.

A study of adaptive array antenna system for land mobile communications

Performances of an adaptive array antenna system for land mobile communications have been investigated through computer simulation and experiments. The adaptive array antenna system can automatically form nulls in the direction of undesired wave on receiving directional pattern. First, it is verified by computer simulation that only desired wave is received without interference by the system controlled on the basis of CMA, when the desired and undesired waves arrive at the receiving point together. Next, it is experimentally indicated that the undesired wave is suppressible by approximately 20 dB, even if the antenna element of the system has not an omni-directional pattern. From these studies, it is confirmed that the adaptive array antenna system is very useful for high quality land mobile communications.

Radiation characteristics of on-glass mobile antennas for digital terrestrial television

Digital terrestrial television (DTV) services began in Japan in December 2003. At present, monopole antennas are used for mobile reception of TV signals, despite suffering some severe problems. Monopole antennas protruding from a car body are easily broken and spoil the appearance of a car. The main lobe of a monopole installed on a car is above the horizontal plane, but the angle of incidence of the TV signal is almost horizontal, so poor reception quality results. Thus, monopole antennas do not meet the stringent requirements of mobile DTV reception. We have developed a novel horizontally polarized on-glass antenna which is suitable for DTV reception, because its elevation pattern peak is horizontal when installed on a car. Other merits are broad input impedance bandwidth across the UHF band (470-770 MHz), and not spoiling the appearance of a car.

Vertical radiation patterns of mobile antenna in UHF band

Theoretical and experimental studies are made on radiation patterns of mobile antennas within the frequency range from 300 to 900 MHz. In order to calculate vertical plane patterns of quarter wavelength monopole and a half-wavelength dipole located on an automobiles roof, a theoretical model of an automobile body is developed, in conjunction with the geometrical theory of diffraction (GTD). The theoretical model consists of three-perfectly conducting plates. It is ascertained from a comparison between calculated and measured results for the feed point impedance and the radiation pattern that the effect of the body and the earth can be well examined with the theoretical model. The results of pattern calculation for the above two antennas show that the radiation patterns depend largely on the configuration of the automobile body and the earth condition. The technique described in this paper can be used as a design tool to estimate radiation performance of mobile antennas.