Methods for Automated Evaluation & Change Detection of HFR Antenna Response

The quality of HFR surface current measurements is dependent on the accurate measurement of the receiver's antenna response pattern to assign direction of arrival (DoA) to incoming signals. If electromagnetic (EM) conditions at the site morph or hardware changes are made, the antenna response can be impacted. If not properly factored into the data processing scheme, this leads to the deterioration of the DoA assignment accuracy, regardless of the nature of the receive antenna configuration. Routine manual remeasurement of antenna response patterns for ongoing system QA is generally infrequent, and it is often the case that the measured response patterns remain valid for more than a year without needing to be changed. However, when a change does occur, it is essential to minimize the identification and response time. For a technician with some basic training and a few stations to monitor, this has historically been a straightforward and routine task. As networks grow larger, to dozens of stations in some cases, having automated, quantifiable monitoring and evaluation metrics for the operator reduces costs and minimizes response time to changes. By proactively monitoring the stability and accuracy of an antenna response pattern, the reliability of DoA assignments increases, which can have positive downstream effects on current measurement and other applications of HFR data. Two classes of monitoring metrics for quantifying the reliability of HFR antenna response patterns are discussed. Examples of the effective use of these monitoring methods to identify the need for antenna pattern remeasurement in the field are also presented.