Improving the Efficiency of Microstrip Patch Antennas
There are many applications where simple, highly efficient printed antennas mounted on high dielectric constant substrates are required. One such case is in a mobile communications base station terminal for a microcellular system. Ideally, the antenna is mounted on the same substrate used for the active microwave components and perhaps photonic devices if an optically distributed network is incorporated. Such substrates have a high dielectric constant (εr > 10) and so, as was discussed in Chapter 2, a conventional microstrip patch antenna would not be a suitable choice as it will be inefficient. As mentioned previously, the source of inefficiency is due to the excitation of surface/leaky waves. Surface wave effects can also manifest themselves in other detrimental ways, including increasing the crosspolarization levels and scalping in the radiation patterns of a printed antenna. These are typically experienced when the surface wave diffracts off the finite edges of the ground-plane, in a similar vain to the field radiated by a slot (refer to Chapter 3).
KeywordsSurface Wave Transverse Magnetic Transverse Electric Patch Antenna Circular Patch
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