An automated measurement system has been developed for measuring a magnetic-field strength inside and outside a motor vehicle exposed to an electromagnetic-field (EM-field). This measurement system consists of an EM-field generator unit, a magnetic-field probe, a data transmission unit with a fiber optic link, a graphic computer and its peripherals. The system is capable of measuring an EM-field strength of 4085 dBµA/m within a frequency range of 20200 MHz, with a certainty of 0.5 dB. The time required for the measurement is approximately three minutes per axis of X, Y or Z at one measuring point when the measurement is repeated five times per specific frequency at 2 MHz intervals for a frequency range of 20200 MHz. This measuring time is one-twentieth as long as that required by conventional unautomated measurement sets.

A novel algorithm for an adaptive array that is suitable for a multi-carrier transmission will be proposed in this paper. In an adaptive array, signals received by antenna elements are weighted and combined together. In the proposed algorithm, distortion of a spectrum of the combined signal is detected and weight coefficients for each antenna element are controlled so that the spectrum of the combined signal becomes flat. Concept of the proposed algorithm can be interpreted as the CMA which is applied to signals sampled in the frequency domain. Furthermore, a configuration of the adaptive array will be shown. Signals separated in a receiver of the multi-carrier transmission are utilized to detect the distortion of the signal spectrum. By adopting the proposed configuration, the spectrum of the multi-carrier signal can be easily detected. In order to investigate the performance of the proposed adaptive array, computer simulation has been carried out. Numerical results show that; 1) A desired wave is captured well even if an interference wave is narrow band signal and is stronger than the desired wave. 2) Suppression performance for a co-channel interference wave depends on both a symbol timing and SIR of arrival waves. If the symbol timing of the interference wave greatly differs from the timing of FFT window of the receiver, the desired wave can be captured even if the co-channel interference wave is stronger more than 10 dB compared with the desired wave. The conventional CMA adaptive array has a serious problem that the narrow band interference wave is captured when it is stronger than the desired wave. On the other hand, it is extremely rare that the proposed adaptive array captures the narrow band interference wave. Therefore, it can be said that the proposed adaptive array is a robust system compared with the conventional system.

The radiation patterns of wire antennas on an automobile are studied at FM radio frequencies in the presence of the earth. The computational technique is besed on the wire-grid method and the reflection coefficient method. The antennas considered are a vertical monopole and a horizontal dipole mounted on the roof side and the rear window of the body, respectively. It is verified from experimental studies that the computation of the radiation pattern is reasonably accurate. Because of the effect of the body and the earth, in the case of the vertical monopole, a large component of the cross-polarized field and the lobes are generated; and in the case of the horizontal dipole, the direction of the maximum radiation faces nearly to the zenith and the radiation field becomes very weak. The computational technique and the results obtained are useful in the design of the automobile antenna system for an FM radio.

Theoretical and experimental studies are made in the UHF band on a quarter wavelength monopole and a half wavelength dipole located on a trunk-hood of a car. To calculate vertical radiation patterns, the theoretical model of the car body and the GTD approach are adopted. It is confirmed from a comparison between calculated and measured results that the theoretical model is very useful to analyze the trunk mount antenna performance and the effect of the body can be well examined with it. The results of pattern calculation for two type of antennas show that vertical radiation patterns, especially the pattern in the front direction of the car, depend largely on the car body. That is, many sharp lobes appear in the vertical pattern, and further, the shape of the lobe and the gain vary largely with the change of the antenna height and location. An approach of this kind can be effectively utilized as a design tool to estimate the radiation performance of mobile antennas.

This paper presents a method for simply estimating characteristics of signals received by a millimeter wave car radar. In this method, the substitution of a radar target with a set of scattering points is introduced to take account of the phenomenon that only a part of the target is irradiated with the radio wave from the radar antenna with a sharp beam; the phenomenon is peculiar to the car radar which operates in a compact range. The positions of these scattering points and the RCS values for the scattering points are appropriately determined on the basis of a measured RCS image for the target. The RCS image means a spatial distribution of RCS values on the surface of the target. In addition, influence of the ground, which is a dominant clutter in car radar environments, and characteristics of the car radar hardware can be included in the estimation method. The estimated characteristics of the signal received by the car radar are compared with the measured ones under typical cases in the car radar environments. The comparison verifies not only that the received signal characteristics are well estimated even when the range is rather short but also that the substitution of the target with scattering points is valid. The proposed method can realize the estimation of the received signal characteristics. Furthermore, the method can be developed into a computer simulation for evaluating the target detection performance of the car radar.

We propose a new type of microstrip line to waveguide transition fabricated on a single layer dielectric substrate. Impedance matching of the transition is achieved by controlling the size of a matching element and the length of an inserted microstrip line across a waveguide. As a result of experiments, low transmission loss of 0.4 dB is realized at the design frequency of 76.5 GHz. Bandwidth of the transition is numerically investigated by the finite element method. It is clarified that the bandwidth of the transition becomes wider as the cross section of the waveguide becomes smaller and twice as wide as that of a conventional microstrip patch antenna element fabricated on a dielectric substrate with the same parameters. In addition, the effect of errors in relative position between the dielectric substrate and the waveguide is also investigated. It becomes clear that degradation of transmission characteristics is caused by the shift of resonant frequency and keeps less than 0.1 dB for a manufacturing accuracy within 0.1 mm.

We propose a method for accomplishing accurate RCS (Radar Cross Section ) images of a car in a compact range. It is an improved method based on an ISAR (Inverse Synthetic Aperture Radar) technique. To obtain accurate RCS values, an idea of an image correction function for the Fourier transform used in the ISAR processing is introduced. The role of the image correction function is to compensate the difference of the propagation loss as to the different scattering points on a target. As a result, `sensitivity' of imaging in the compact range is kept uniform. Hamming window is suitable for the Fourier transform to accomplish RCS images because of its low sidelobe level and the sharpness of a mainlobe. When hamming window is adopted, the spatial resolution is approximately twice the size of granularity which is determined by the ISAR parameters. To verify the improvement of the RCS images obtained by means of our method, several numerical target models are employed. The results of the investigation show that uniformity of `sensitivity' for obtained RCS images is achieved in the compact range and accurate images with the resolution of twice the size of granularity are accomplished without blurs or distortions in the unambiguous area. RCS images for rear aspects of a passenger car are investigated with the spatial resolution of 50 mm in the 60 GHz band. The RCS image varies with the aspect angle of the car and the specular reflection occurs for the millimeter wave. When the curvature on the car edge is small, a blurred RCS image is observed. The reason is that a scattering center of the specular reflection moves so widely that it can't be regarded as a fixed point. This causes elongation of the RCS image. A peak value in the dominant area for each aspect angle is less the 0 dBsm and no remarkable areas where the RCS value exceeds-20 dBsm is found any more on the car except such the dominant area.

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 novel millimeter-wave slotted waveguide array antenna is developed for automotive radar systems. An antenna structure suitable for mass-production is proposed in this paper. The waveguide is composed of two parts; an upper plate and a bottom plate. It is not necessary to contact each other closely because they are divided at the center of the broad wall of the waveguide where the electric current is small. In addition, grating lobes are suppressed by using a cylindrical cavity around each slot and by controlling the slot arrangement without using dielectric material in the waveguide. We have fabricated the proposed antenna by metal injection molding. The measured antenna efficiency results in 55%, which is quite high in comparison with any other conventional low cost millimeter-wave antenna. This efficiency is almost the same as that of the antenna fabricated by precision metal machining. In this paper, it is confirmed that the proposed antenna could be manufactured with low cost.

Information services for drivers and passengers in land vehicles have been drastically increasing in recent years. Frequency spectra used in vehicle communications cover an extremely wide band ranging from the LF band to the millimeter-wave band. Today, a variety of properties are required of antennas depending on the types of radio systems; more than ten kinds of antennas are installed in land vehicles. Advances in such land vehicle antennas developed in Japan are reviewed in reference to antennas for broadcasting reception and mobile communication systems. Typical antennas are introduced for each system, and the technology and performance are described.

A microstrip array antenna with 45-degree inclined linear polarization is proposed for automotive radars. The proposed antenna has the advantages of high aperture efficiency, low profile and ease of manufacture. The rectangular radiating elements inclined at 45 degrees to the straight microstrip line are directly connected to it at their corners in the proposed array antenna. The radiating element has a feature that radiation conductance for co-polarization is controlled widely enough to set desired amplitude distribution keeping excited mode for cross-polarization negligibly small. The feed line loss of the linear array antenna having 15 wavelengths is estimated 0.9 dB in the design taking the loss of the microstrip line into account. The performance of two types of developed antennas, for electrical and mechanical scanning radars, is presented. The fan beam subarray antenna for electrical scanning radars has an aperture efficiency of 53% with gain of 22.5 dBi at 76.5 GHz. For mechanical scanning radars, the two-stage series feeding circuit is also proposed for lower feed line loss and setting desired amplitude distribution. The pencil beam array antenna has an aperture efficiency of 39% with gain of 32.2 dBi at 76.5 GHz.