Results and Analysis of Using the MEDLL Receiver as a Multipath Meter

The Multipath Estimating Delay-Lock-Loop (MEDLL) is a method for mitigating the effects due to multipath within the receiver tracking loops. Recently the MEDLL receiver was modified to output the multipath parameters, hence the name ‘Multipath Meter’. These parameters include the delay, relative amplitude, and phase of the multipath signal along with the residual values for each correlator. The multipath parameters are estimated by the MEDLL and the residuals indicate the quality estimation process. This paper investigates how the Multipath Meter can be used in real-time monitoring of the GPS signal. Using a GPS simulator the MEDLL receiver is tested to determine how accurately the multipath parameters can be measured. Also, data is collected from an antenna location on the roof of the NovAtel facility at Calgary, Alberta, Canada. Two specific situations are focused on: short delay and long delay multipath. Results show that the Multipath Meter is useful for signal quality monitoring and reference site surveys.