Performance Analysis of a Software-Defined Radio BDS B2a Receiver in the Presence of DME Interference

The BeiDou Navigation Satellite System (BDS) B2a signal is broadcast within the Aeronautical Radio Navigation Services (ARNS) frequency band, which has already been occupied by various aviation systems such as Distance Measuring Equipment (DME). DME is a pulse-ranging system widely used in civil aviation. The high-power reply signals transmitted from DME ground stations are within the BDS B2a bandwidth, thus potentially affecting the airborne B2a receivers. This study evaluates the effects of DME pulse interference on the performance of the BDS B2a receiver. A testbed is first developed which includes a GNSS signal simulator, a DME signal generator and a Software-Defined Radio (SDR) based BDS B2a receiver. Then, the B2a signals under different DME interference scenarios are collected and processed to investigate the acquisition and tracking performance of the receiver. Results show that the correlation peak to the next peak ratio (CPPR) and the correlation peak to the mean peak ratio (CPPM) decrease obviously under DME interferences, indicating the degradation of the acquisition performance. When the DME interference power is as high as -60 dBm, the receiver fails to acquire B2a signals. Furthermore, it is observed that the carrier-to-noise ratio (C/N₀) decreases by 1.03 and 5.12 dB-Hz when the DME interference power is -80 and -70 dBm, respectively, indicating the degradation of the tracking performance. In particular, the Root Mean Square (RMS) values of the code tracking errors in the delay-locked loop (DLL) and the carrier tracking errors in the phase-locked loop (PLL) increase significantly, which can seriously affect the ranging performance of the receiver. The analysis in this paper shows that the DME interference can degrade the performance of the airborne BDS B2a receiver, which provides a reference for the aviation applications of BDS B2a signals.