Characteristics Mode Analysis: a Review of Its Concepts, Recent Trends, State-of-the-Art Developments and Its Interpretation with a Fractal UWB MIMO Antenna
In this article, we present a compact and efficient diametrically-fed dual port fractal UWB MIMO antenna for portable handheld wireless devices. The electromagnetic behaviour on conducting body is analyzed through classical approach based characteristics mode analysis (CMA). Their intrinsic characteristics are explored on the basis of (a) modal surface current distributions, (b) narrow/broad bandwidth capability and (c) radiation potentials. Concurrent analysis is persuaded on diametrically-fed dual port fed fractal conducting surface, that provides interesting facets on the combinatory effect of electromagnetic performance and physical behaviour on metallic radiator, metallic ground planes (unconnected/connected) and combination of two aforementioned metallic compact geometries. Theoretical insights are investigated for essential/non-essential modes existing in proposed geometry. The investigation through CMA also gives plethoric information on the feed location of antenna on modal surface currents and similar trends to capture its radiation potentials on the current nulls existing in the physical body. A broad classification of modes is explained, covering the CMA modal dynamics such as (a) characteristics angle (CA), (b) eigen values (EV) and (c) modal significance (MS). These additive parameters in general reflect the resemblance of Q-factor≈B.W. for narrowband/wideband traits, electrically/magnetically coupled energy behaviour and radiative potential for far-field propagation. Thus, in a nut-shell, it can be inferred that `CMA provides physically intuitive guidance for the analysis and designing of antenna structures'. To support the findings highlighted in this particular study, a concise review about the theory of characteristic modes and the practical examples that use such concepts are taken into consideration.