LOCFIELD® Antenna Dimensions
For planning an installation it is important to select the right type of antenna with regard to specific dimensions and performance. All variants are characterised by three parameters: active length, total length and cable diameter. Athough the PCB as the termination of the active cable segment at the remote end of the cable is also contributing to the concentric electromagnetic field around the antenna, it is not included in the active length. The most interesting part is the active cable segment with the possibility to form the field freely depending on the application's demands.
It is measured from the end of the damping unit to the beginning of the PCB.
This is the interesting segment of the cable where high-frequency currents flow along the outer side of the cable shield. These currents generate an EM field around the cable. The currents show little or no tendency to leave the cable or radiate into free air. Therefore the LOCFIELD® antenna can be more precisely described as an HF current conducting wire than a classical antenna. When approaching metal sufaces the antenna can be viewed as a wire-over-groung causing no reflections in contrast to a typical radiating antenna.
It is the distance from the connector to the beginning of the damping unit.
Despite the fact that the LOCFIELD® antenna is produced from a single cable, this part can be viewed as just an ordinary connection cable. Since cable losses have to be taken into account, the connecting length is kept relatively short in the variants listed below. In case a longer coaxial cable is necessary to reach the RFID reader, a low loss type with a max. signal damping of 0.3 dB/m is highly recommended.
Connecting Length + Damping Unit + Active Length = Total Length
The physical overall length would be: Total Length + PCB. The hole in the PCB is used during the assembly process or can be helpful when the antenna is hanging with moderate tension in free air. The PCB must not be tightly fixed, e.g. with screws, to an underlying surface.