Design method of low-profile and small antenna for mobile communication.

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A low-profile and small antenna consisting of microstrip patch (MSA) or other printed antenna are widely used as an efficient radiator in mobile communication systems.This report presents the designing techniques of low-profile and small antenna for mobile system.The test antennas were made of a copper-clad 0.6 mm-thick low-loss Teflon fiber-glass substrate with a dielectric constant of 2.55 and loss tangent of 0.0018. The important items of this investigation are mentioned briefly as follows.1. In miniaturization of an antenna, it is important to estimate unloaded Q(Q_0), radiation efficiency eta and frequency bandwidth BW.The values of eta and BW for shorted-MSA are calculated for a typical substrate ( Teflon fiber-glass substrate ) as a function of substrate thickness ( h/lambda_0 : lambda_0 : free space wave-length ). On measuring the values of eta and BW, all the measured values agreed well with the calculated ones within desirable ranges for designing.The measured patterns of the antenna agreed also well with the computed results.2. In order to estimate the performance of this low-profile and small antenna, some test samples were constructed and tested at the microwave-region. As expected, the experimental pattern and ellipticity of the antenna agreed well with the theoretical ones.These results indicate that the low-profile and small antenna is applicable as an element antenna for mobile telecommunication system.3. Finally, the low-profile planar array was made by integrating large numbers of these small antennas. The experimental pattern of the test planar array agreed well with the theoretical one. The antenna presented here is, therefore, considered to be effectively applicable as a low-profile and small antennas for mobile system.