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

Many antennas are used while mounted on a small structure. Mobile phones are taken as the most widespread example. With few exceptions it is the support structure which is radiating rather than the antenna element. To get an unified approach the concept of the support structure defined antenna (SDA) is defined and quantities for describing the function of the SDA are discussed. The most important parameter is a new coupling factor telling how the antenna functions of the support structure will interact to give the total antenna function. Using this tool it is 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 the mobile phones are HF antennas on aircrafts, AM-antennas on cars and most types of hand portable radio sets. It follows from the definition that the antenna element is small compared to the wavelength and thus 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.