Multilayer and parasitic configurations
Microstrip antennas composed of multiple conducting patches or feed lines electromagnetically coupled to the resonant, radiating patch offer several ad vantages over the traditional single patch connected to a feed line or feed probe. These advantages include increased bandwidth or multiple frequency operation, dual polarisation, and control of input impedance. However, the antennas are often more complicated to fabricate or they may require more surface area, so that the designer may be required to sacrifice one desirable feature in order to obtain another one. Most of the structures in this chapter have been modelled by using either the cavity model or moment methods, and the segmentation method has also been applied to some of the configurations. In general, the analysis techniques provide a good qualitative model for the antennas, thus providing the designer with the insights needed to develop a functional antenna. Many of the existing analyses also have shown good quantitative agreement for the cases appearing in the literature, but the ranges of validity are not generally known, and the computed results may not be sufficiently accurate for many practical values of substrate permittivity and thickness or for variations in patch geometry. Nonetheless, multiple-layer microstrip antennas and antennas utilising parasitic coupling to the feed or to other resonant patches offer distinct advantages for many systems applications, and are likely to be used in antenna systems that require the specialised features available from these antennas.
Multilayer and parasitic configurations, Page 1 of 2
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