Near Weak field coupling for large bus connections

Electric vehicles typically have a large array of storage cells and for efficient operation each cell should be monitored individually. In other areas industrial processes need to be monitored often in harsh conditions. A conventional approach is to physically connect sensor and actuators to long buses. High data rates demand a high frequency buses but direct connection means that loading and attenuation can be severe and impractical if a large number of devices need connection. The alternative is free space radiation. The latter was investigated for track to train communication at 2.4GHz [7] In the limited space of battery compartments rectangular wave guides are impractical, however micro strip lines can made compact enough to fit in these locations. By weakly coupling a sub-wavelength antenna to a micro-strip transmission line Simulations and experimental data over frequencies between 600 and 1 GHz show it is possible to couple up to 100k devices without unduly loading the line. The line is not limited in length and radiation is so low that is little interference between adjacent devices and the surrounding medium. It has the added advantage that each node is electrically isolated from each other and the transmission line.