High Performance Portable Telephone Antenna Employing a Flat-Type Open Sleeve


IEICE TRANSACTIONS on Electronics   Vol.E79-C   No.5   pp.693-698
Publication Date: 1996/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microwave Devices for Mobile Communications)
Category: Passive Devices
portable telephone antenna,  linear antenna,  high gain,  moment method,  finite element method,  

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A flat stick-shaped whip antenna was developed for Japanese commercial portable telephones. It provides a high gain even though it is short and retractable. It is an open-sleeve type antenna. i.e., the inductance-loaded dipoleantenna element parallels a twin-lead type feeder. It suppresses the currents on the radio housing even at short antenna lengths. Moreover, it is easy to achieve two resonant characteristies and able to construct retractable type. A relatively high gain is gotten even when the antenna is in a retracted state. This antenna has a suitable configuration for commercial portable telephones. This paper first calculates, the current suppression of the housing on a principal model of this antenna, i.e., without a twin-lead feeder. The second analysis determines the effects of the twin-lead feeder and the dielectric coat on the antenna. Next,the two resonant technique and the configuration for the retractable-type antenna describes. In addition, the return loss and radiation pattern for the trial model were measured. The return loss shows that the two resonant characteristics and the bandwidths of the high and low resonant frequencies are 2.2% and 1.5%(VSWR2), respectively. For when the antenna is extended, radiation patterns are nearly the same as for the case of the 1/2 wavelength dipole antenna, and the antenna efficiencies are -1.6 dB at 820 MHz and -1.1 dB at 950 MHz. Other hand, for the retracted state, they are destroyed by the housing currents, but the efficiency is relatively high of -1.8 dB at 950 MHz. In these experiments, it is clear that the antenna achieves high performances.