Antenna matching is an important aspect of any RF system. A properly designed and matched antenna increases the operating distance of the wireless product. Well matched antennas can transmit more power from the radio – therefore transmit over longer distances. Likewise, a well matched antenna allows the maximum transfer of energy from the receiving antenna to the receiver front end. Thus, allowing better receive characteristics for the system.
But the use of a capacitor can also have a big impact upon the physical size of an antenna. If the goal is a compact, integrated antenna, the use of a capacitance ‘top hat’ on a Planar Inverted F antenna can reduce the antenna size by 30% or more. Radiation patterns and efficiencies can be optimized by this matching. Further, the use of a capacitance ‘top hat’ can match an antenna that’s even smaller than an ideal inverted F size for the band of interest. In this case, the capacitor can allow both reduced antenna size and system optimization.
There is a class of high Q, small size, thin film capacitors that allow the selection of infinite capacitance values and exacting lot to lot performance. These performance features, combine to provide designers an attractive option in antenna optimization and matching.