An Investigation of the Use of Ergs Loop Antennas for Vehicle Detection and Counting

摘要

Three methods of adding vehicle detection capability to the ERGS-II Route Guidance System were evaluated. The first of these, which is based on detection of a change in the VSWR of the trigger loop feedline as a vehicle passes over the trigger loop, was found to be marginal in sensitivity due to inadequate coupling between the trigger loop and the vehicle. The second method utilizes the presence of a vehicle over the antenna assembly to couple an increased amount of 230 KHz energy from the trigger loop to the communication loop which encloses it. The results of experimental measurements indicate that results are not adequately predictable and also suggest that exceptionally precise relative alignment between trigger and communication loops would have to be held if this method of detection were used. The third method, in which the ERGS-II trigger loop is replaced by a sensing loop, requires extensive modifications to the ERGS-II logic concept and might degrade its triggering accuracy. However, this method is rather effective in detecting vehicles, and in addition, offers the potential for overall system hardware simplification. (BPR abstract)