International Symposium on Antennas and Propagation
Bandwidth Enhancement and Size Reduction for Conformal Antenna by Coupling with Platform
Johnson J. H. Wang, D. J. Triplett,
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It is well known that a fundamental gain bandwidth limitation exists for an antenna of a given electrical size, which is generally referred to as the Chu limitation . As a consequence and corollary, an antenna must be sufficiently large in terms of the operating wavelength in order to be efficient. For obvious practical reasons, bandwidth enhancement and size reduction are both highly desirable for antennas, and are two facets of the same fundamental issue. Since the advent of the Chu theory six decades ago, this has been a prominent subject in antenna design. Although an enormous amount of research has been conducted, success has been marginal. However, there are major shortcomings and ambiguities in the Chu theory when applied to real-world problems, as pointed out recently by the senior author [2, 3]. One problem is that, when mounted on a platform, the size of the antenna becomes ambiguous. This observation has led to a technique which extends the bandwidth of antennas beyond the apparent Chu limitation, and simultaneously resolves the practical problem of conformal mounting of antenna on platform. In ISAP2007, the senior author addressed the general design issues for conformal broadband multifunction antennas when mounted on an automobile . Although exploiting the mounting platform to enhance antenna bandwidth is not new, the magnitude of the bandwidth enhancement in the present approach is much larger.