Allowing direction finding vehicles to navigate the urban obstacle course
Even the most finely calibrated Direction Finding (DF) systems can often seem to fail when used in the urban environment. This problem can be attributed to multipath propagation. In an urban environment, many buildings reflect, shadow, diffract or block RF signals entirely. This can lead to uncertainty in the bearing as the signal of interest appears to arrive from many different directions.
In some cases, the true signal path may be blocked entirely with the strongest received signal being a reflection. As the operator of a direction finding vehicle homes in on the target signal source according to its apparent direction, they may find they are actually getting farther from the source. As this happens, the direction finding performance may then further degrade.
Multipath propagation is not entirely avoidable – put simply, physics can be inconvenient sometimes. However, there are ways to mitigate the problem and maximize direction finding capabilities even in the most complex environments.
Filtering out the urban noise
Our Cumulative Tracking software is designed for mobile direction finding applications. A location is gradually built up over time using the multiple Lines of Bearing (LOB) obtained as a single vehicle-mounted DF antenna array moves. Our algorithm can also filter out erroneous bearings resulting from multipath effects to leave only the high-quality bearings. This minimizes the degradation of accuracy even in environments where direction finding would usually seem like an insurmountable task.
While direction finding in urban environments would usually be a stressful task as operators are forced to use their best judgement to determine which bearings to ignore, our software requires minimal intervention from the user. Cumulative Tracking can be used to home in on a single target or to locate multiple targets simultaneously.
Additional benefits of the solution
As well as being used for direction finding applications, the system can be used for all spectrum monitoring and management tasks either in isolation or as part of a larger network. Cumulative AOA can also be used for nationwide spectrum survey applications. For example, it can be used to verify the position of multiple transmitters while driving across wide areas by comparing locations to license database information.