An analysis of a conical beam antenna using circular array of monopole on the ground plane is presentd in this paper. This antenna was proposed for applying to the HIPERLAN system. The structure of this antenna type is simple and easy to fabricate. The radiation pattern of the antenna is calculated by combining the total fields radiated from each monopole on the ground plane. The effect of the finite size ground plane is taken into account and found that it affects to the back lobe level. Moreover, it is apparent that nondirectional azimuthal pattem is realized when the circumferential spacing is sufficiently small. The radiation patterns for various parameters such as the array radius and the number of elements are demonstrated. Antenna measurements are set up to verify the proposed principle. The theoretical and experimental results are in good agreement.
INTRODUCTIONThe research and development on the antenna that can complete the applications of mobile and wireless applications are of interest, recently. The conical beam antenna is the suitable candidate because the tracking system is not necessary. There are many researches about the investigations of this antenna in literature El]. The radiation characteristics of this antenna, which can accomplish the specified applications, is that the radiation patterns possess the null in boresight axis (zenith), the elevational beam peak directs toward the subscriber and the azimuthal pattern is nondirectional. The maximum directivity of 7 dBi for mobile satellite communication and 4 dBi for the wireless LAN is required. Several researches concentrate on designing both linear [2]-[4] and circular [5]-[9] polarization to fdfill the requirement of the particular system specifications. The linearly polarized conical beam antenna plays a fundamental role in establishing the communication link between the base station and the peripheral devices for the pan-European standard LAN or High Performance Radio LAN (HIPERLAN). This system has been allocated the frequency band between 5.10 GHz and 5.35 GHz. Historically, the circular patch operating in the higher mode is investigated to radiate the vertical polarization [2]. Alternatively, the array of rectangular patch is designed to achieve the horizontal polarization [3]. Consequently, the dual polarized antenna [4] using diamond patch is proposed to produce both vertical and horizontal polarizations. However, it is evident that these antennas are suffered from the feeder loss. The authors propose the simple structure conical beam antenna using the circular array of monopole on the ground plane. The structure of the antenna is easy to fabricate and the feeding structure'is free from conduction and dielectric loss. The radiation pattem of the antenna is calculated by combining the total fields radiated from each monopole on the ground plane. The effect of the finite size ground plane is taken into account and compared with one considered in case of the ground plane is infinite extent. The radiation patterns for various parameters ...
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