SDA - a new family of small antennas used since long time

摘要

Many antennas are used while mounted on a small structure taking mobile phones as the most wide spread example. With few exceptions it is the support structure which is radiating rather than the antenna clement. To get an unified approach the concept Support Structure Defined Antenna (or SDA for short) is defined below and quantities for describing the function of a SDA are discussed. The most important parameter it a new coupling factor telling how the antenna functions of the support structure will interact to give the total antenna function. By this tool it will be more easy to compare the function of different alternatives for antenna element mounted on the same support structure. The method gives additional information to the EM-simulations which for mobile phones are the common method of analysis. Other examples beside of mobile phones are HF-antennas on aircrafts, AM-antennas on cars and most kinds of hand portable radio sets. It follows from the definition that the antenna element is small as compared to the wavelength and thus that the radiation is more or less omnidirectional or rather dipole-like. Antenna radiation tests of SDAs is a related item where the connection cable modifies the support structure during the measurement.