Jeffrey Chalas

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Fundamental limits on the Q-factor for arbitrary-shaped PEC antennas are presented using the theory of characteristic modes. A formula for computing the Q of an arbitrary-shaped PEC antenna with an impressed current mode is derived, and is used to find minimum-Q bounds. It is shown that minimum bounds on small antenna Q can be determined simply through an(More)
A robust and efficient method is presented for computing the Q limits of arbitrary shape electrically small antennas (ESAs). These limits are based on the theory of characteristic modes (CMs). In contrast to previous techniques, the CM method does not imply assumptions on the antenna shape, its transmit/receive properties and polarization or absorption(More)
Characteristic modes are used to design a multi-antenna NVIS system on-board an electrically small UAV. By analyzing the radiation eigenmodes of the UAV platform, optimal NVIS patterns are constructed, and mounting locations which maximize desirable antenna-platform coupling are identified. The optimal NVIS pattern is then approximated using discrete(More)
The design of in-situ antennas is conducted using the theory of characteristic modes. By performing a characteristic mode analysis of the supporting platform, the optimal spatial regions of antenna-platform coupling can be located, as well as approximate limits on bandwidth. Then, for a given choice of antenna, the proper feed location can be optimized(More)
In this paper, we present an efficient and direct method for computing the lower bound on Q for arbitrary-shaped, perfectly conducting antenna geometries. We begin by deriving a new formula for Q based on the currents induced on the antenna/scatterer and the method of moments (MoM) impedance matrix [Z]. We then use this formula in conjunction with the(More)
Characteristic modes (CMs) are used to design an NVIS antenna system on-board an electrically small UAV. Using the CMs of the UAV platform, near-vertical incident skywave (NVIS) are realized using pre-specified locations for antenna mounting. The appropriate excitation level of each monopole feed can be computed in a systematic manner using the CMs of the(More)
We present a new approach for efficiently computing in-situ performance of platform-mounted antennas. When the antenna-platform system is characterized by the electric field integral equation (EFIE), the moment method (MoM) can be used to analyze the coupled system. To accelerate the solution, the numerical Green's function (NGF) of the antenna is used via(More)
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