Yoshio Ebine

A vehicular-mounted vertical space diversity antenna for a land mobile radio

A vertical space-diversity antenna has been developed in order to achieve a diversity scheme while maintaining the simple appearance of a trunk-lid antenna. It is shown that small correlation coefficients can be achieved by a separation of approximately 0.5 wavelengths. Differences in the upper and lower antenna radiation patterns are clarified as being caused by mutual coupling of these antennas, and an incoming wave spread of more than 20 degrees is the main reason for reduction of the correlation coefficients. Field tests in the Tokyo metropolitan area have indicated that adequate correlation coefficients and an adequate received signal level can be achieved. Moreover, calculation estimations are confirmed by the experimental results. >

Bi-directional notch antenna with parasitic elements for tunnel booster system

This paper presents a bi-directional pattern antenna consisting of notch antennas excited by probes with parasitic elements. The antenna characteristics are calculated by the moment method and are verified by experiments. The effect of a mounting conductor plate is also presented in terms of input and radiation characteristics, and the gain decrease of a tilted beam by the edge effect of the mounting board is compensated for by adding parasitic directors.

Bi-directional notch and crank-shaped antenna

Bi-directional notch and crank-shaped antennas were proposed to extend the coverage of a relay station in the booster system inside tunnels. To extend the antenna coverage area, we present the crank-shaped antenna with parasitic elements. The crank-shaped antenna with parasitic elements suppresses the cross polarization by 17.6 dB compared with the notch antenna with parasitic elements without changing the principal polarization pattern.

Vehicular-mounted diversity antennas for land mobile radios

Three types of vehicular-mounted diversity antennas for a high-capacity land mobile communication system are described. These diversity antennas use conventional horizontal space diversity as well as the recently developed vertical space diversity and pattern diversity. Correlation coefficients of the diversity branches of these antennas are numerically analyzed and optimum antenna structures are designed. The design effectiveness is verified through field experiments.<<ETX>>

Mutual coupling suppression of two dipole antennas backed by optimized reflector

In a repeater antenna for wireless communications, suppression of mutual coupling between transmitting and receiving antenna is required to reduce the weight and size of the antenna system even if the antenna separation is very small. On the other hand, for a dipole antenna backed by a reflector, it has already been proposed that the enhancement of FB (front-to-back) ratio of a dipole antenna can be achieved by optimizing the reflector shape. Miniaturization of the reflector can be achieved by using an optimum size for the FB ratio (see Rikuta, Y. et al., Asia-Pacific Microwave Conference, vol.3, p.1068-71, 2001). An antenna with high FB ratio has little influence on the backward direction. This paper presents the suppression of mutual coupling with a small distance between antennas by using two antennas with high FB ratio back to back. We investigate a rectangular reflector and a dual boxing reflector. The characteristics of mutual coupling of these antennas are calculated by FDTD analysis.

A multi-frequency base station antenna for complex cell configurations

To meet the complex cell configurations in 3G mobile communication systems, base station antennas are required to achieve multi-frequency operations. The electrical characteristics such as low sidelobe levels and electrical beam tilt capabilities are needed in these antennas. This paper clarifies the method used to achieve the electrical characteristics in the frequency band of 800 MHz to 2000 MHz. A linear array antenna is co-used for all the frequency bands. To design the above electrical characteristics, the radiation pattern synthesis technique is employed. To achieve the wide band low sidelobe characteristics, the adequate design frequency of the radiation pattern synthesis is derived. Moreover, the suitable antenna configuration for electrical beam tilt was clarified. Numerical radiation characteristics for the frequency range of 800 MHz to 2000 MHz and electrical beam tilt angle of 6 to 10 degrees are shown. Satisfactory characteristics are obtained.

Reflector shape optimization for FB ratio of dipole antenna

This paper presents the enhancement of FB ratio by optimizing several types of reflector shape which are placed on the back of a dipole antenna for the sector antenna. By optimizing the size of each reflector shape, the FB ratio of dipole antenna is increased by more than 20dB. Comparing each shape for the same width of reflector, a dual box reflector has the best FB ratio of more than 30dB.

6-sector antenna using proximity coupled taper slot for multi-media mobile system

This paper presents a 6-sector beam antenna for mobile radio using an electromagnetically coupled taper slot antenna. The antenna element characteristics are shown by measurements and a prototype 6-sector antenna is demonstrated.

A two-layered patch and loop antenna with dual frequency

This paper presents a two-layered antenna with dual frequency for indoor micro cellular system. It consists of a upper loop and a bottom center feed patch antenna. FDTD analysis shows that this antenna has two resonant frequencies and the radiation patterns are similar to monopole antenna.

Mutual coupling characteristics of binomial and Chebyshev arrays using 16 element patch antennas with choke for repeater systems

Repeater systems will become practical in the IMT-2000 system in order to provide service in locations where presently radio waves cannot reach. We have examined an antenna structure, in the form of a patch array antenna of 4 elements, for a repeater (Michishita, N. et al., IEE 12th Int. Conf. Antennas and Propagation, 2003). At the edge of the ground plane is a choke structure, and this structures parameters effect the FB (front-to-back) ratio. We investigate a 16 element patch array antenna which references the 4 element design method and present the mutual coupling characteristics of the 16 element patch array antennas with chokes. The repression of the FB ratio by a choke is small in the case of the 16 element array, because its side lobe level is large. We examine the effect of restraining the mutual coupling using a binomial and Chebyshev array by controlling the amplitude of each element. The binomial and Chebyshev arrays effect the restraint of the side lobe level, and the mutual coupling can be made less than -100 dB by choosing suitable parameters.