RegisterBasic mode, parasitic modesStudying wave propagation, the mode of the lowest critical frequency is called the dominant (basic) mode. Studying wave propagation through periodic structures, the mode of the lowest spatial frequency is called the basic mode. The term mode denotes here a certain direction of the radiated wave, for which waves radiated from all the parts of the antenna reach the observation point with the same phase. In analogy to the antenna array, the basic mode can be understood as a wave propagating in the main lobe direction. Wave propagating in the direction, which is nearly perpendicular to the structure, is of the lowest spatial frequency (for perpendicular direction, spatial frequency equals to zero). In analogy to the antenna array, even the periodic structure can have a side-lobe (an intensive radiation to another direction, significantly declining the normal). This radiation is usually undesired (parasitic mode). Back
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