Compensation Effect of Quasi-Inverse Filter (QIF) on Frequency Characteristic Distortion in Wideband Systems

Mitoshi FUJIMOTO  Haiyan ZHAO  Toshikazu HORI  

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.6    pp.1783-1790
Publication Date: 2008/06/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.6.1783
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on 2007 International Symposium on Antennas and Propagation)
Category: Antennas
compensation,  frequency distortion,  propagation characteristics,  approximate inverse filter,  

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High-speed wireless communication systems have attracted much attention in recent years. To achieve a high-speed wireless communication system that utilizes an ultra-wide-frequency band, a broadband antenna is required. However, it is difficult to obtain an antenna that has uniform characteristics in a broad frequency band. Moreover, propagation characteristics are distorted in a multi-path environment. Thus, the communication quality tends to degrade due to the distortion in the frequency characteristics of the wideband communication system. This paper proposes a quasi-inverse filter (QIF) to improve the compensation effect for the transmitter antenna. Furthermore, we propose a method that employs the newly developed QIF that compensates for frequency characteristic distortion. We evaluate different configurations for the compensation system employing a pre-filter and post-filter in the wideband communication system. The effectiveness of the QIF in the case of severe distortion is verified by computer simulation. The proposed method is applied to a disc monopole antenna as a concrete example of a broadband antenna, and the compensation effect for the antenna is indicated.