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Compact and low-profile VHF antennas with enhanced bandwidth have a wide spectrum of applications in both commercial and military communication systems. Having both of these criteria in a single antenna, however, is very challenging. In this paper, we demonstrate a method for bandwidth enhancement of vehicle-mounted electrically-small antennas operating in the VHF band. In this method, the vehicle...
This work is a preliminary investigation of the possibility to excite a set of characteristic modes on a three dimensional object. The aim of this study is to provide guidelines for the excitation of characteristic modes on a complex platform in order to obtain a pattern reconfigurable.
In this paper, a 3-port bug-like multiple-input-multiple-output (MIMO) antenna design based on the theory of characteristic modes is proposed. This antenna has a compact size of 50 × 61.5 × 10 mm3, and it operates in the 2.4-GHz ISM band. We present a novel design approach for the proposed antenna. First, as the antenna has a bilaterally symmetric structure, the characteristic currents can be decomposed...
Various modal decompositions are performed on an array of dipoles backed by electric ground plane. The theory is based on analytically prescribed current on dipoles so the decomposition returns directly excitation coefficients of an array with respect to given quantity.
The limited eigenvalue dynamic range calculated from a characteristic mode solution is studied. Two methods of handling singular terms in the electric field integral equation matrix filling process are reviewed. Characteristic mode solutions using each singular treatment are compared with modal solutions obtained from a commercial solver. Results show that small alterations to the handling of singular...
In this paper, the directivity limit of end-fire arrays based on Huygens source elements has been numerically investigated. Firstly, the elementary infinitesimal Huygens source behavior is introduced and studied through Spherical Wave Expansion (SWE). Then, the maximum theoretical directivity of two-, three- and four-element arrays is calculated as a function of the inter-elements spacing. The optimization...
Most antenna theories treat an antenna is reciprocal, though non-reciprocal passive antennas are possible with gyrators and circulators. We describe basic properties of transmitting and receiving antennas which can be non-reciprocal, then related them considering thermodynamic equilibrium. An extension of the fundamental equation is derived, which is valid for any passive antennas. Based on the extended...
We present a methodology to design cavity-excited omega-bianisotropic metasurface (O-BMS) antennas capable of producing arbitrary radiation patterns, prescribed by antenna array theory. The method relies on previous work, in which we proved that utilizing the three O-BMS degrees of freedom, namely, electric and magnetic polarizabilities, and magnetoelectric coupling, any field transformation that...
Practical Antenna Design for handheld devices is demonstrated through the utilization of the modal/Eigenmode theory of antennas. Here, a review of the underlying design fundamentals is outlined. Next, a design example featuring the antenna design of a modern smartphone is presented. The design cycle is simplified through finding an antenna with appropriate complex resonance frequency to cover a required...
In this paper, by using the Theory of characteristic modes (TCM), we analyze the effect of Inductive Coupled Elements (ICE's) used for the excitation of Characteristic Modes (CM) on antenna chassis. ICE's are used in sets to excite chassis modes and are placed at current maximas of the desired modes. Using TCM analysis, it was found that the introduction of such ICEs significantly affect the CM of...
The paper discusses the application of the Characteristic Mode Analysis (CMA) to a number of problems arising in practical antenna applications, and identifies some challenging issues that have been encountered by in the process of applying the CMA to some real-world problems. These include, among others, excitation of the Characteristic modes on complex platforms; antenna placement on these platforms...
We provide a complete and exact space-time system model for arbitrary antennas valid for generic field excitations. The method is based on introducing a time-dependent extension of the antenna current Green's function (ACGF). It is shown that this approach is more general than the conventional impulse response model by proving that for generic antennas an impulse response may not exist. A complete...
A leaky-wave antenna (LWA) designed in substrate integrated waveguide (SIW) technology and showing high directivity in its transverse plane is presented. In addition, the proposed SIW LWA allows for the flexible control of its complex propagation constant, and thus of its radiation properties. For this purpose, the width of the SIW is used for the control of the phase constant and the separation between...
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