Multistatic radar synchronisation using COTS GPS disciplined oscillators

Abstract

The benefits of multistatic radar have been well understood for decades, though the challenges of implementing such systems have limited their development and subsequent operational use. Multistatic radar's performance enhancements, over standard monostatic radar, result from the cooperation and data-fusion between spatially separated radar nodes, however, to enable cooperation and data-fusion, some degree of node-to-node time and frequency synchronisation is critical. In this work, the use of commercial off-the-shelf (COTS) GPS Disciplined Oscillators (GPSDO) as a source of indirect radar synchronisation is evaluated and the development, and subsequent testing, of a GPSDO based radar synchronisation system is presented.

Global Navigation Satellite Systems disciplined oscillator synchronisation of multistatic radar

“…Surprisingly, the LNRCLOCK‐L6T pairing was found to provide the best relative timing precision, with a 1.65 ns mean offset between devices, though, considerably larger offsets of up to 10 ns have been observed in previous measurements of the LNRCLOCK‐L6T GPSDOs. The THUN‐E pairing provided the best timing accuracy with a two‐sigma of 4.24 ns, equal to a bistatic range error of 1.28 m. The LNRCLOCK‐F9T provided the second best timing accuracy with a two‐sigma of 6.12 ns, equal to a bistatic range error of 1.83 m. It should be noted, these measurements likely provide a best case scenario, the use of separate GNSS antennas over large bistatic baselines in environments with different ambient temperatures will likely deteriorate the relative timing performance to that measured in lab conditions [20, 23].…”

“…This was achieved by comparing the stability of the internal LO to an estimated stability of the GPS receivers 1PPS (an estimate of the GPS receiver's stability had to be used, as there is no way to sample its output). An optimal time constant of $$\left({\tau }_{\mathit{PLL}}=1000s\right.$$ was estimated [23]. The frequency stability of the THUN‐E devices, with the optimised disciplining loop characteristics, is additionally plotted in Figure 7.…”

“…In a previous publication by the authors of this paper, the performance of two different models of commercial‐off‐the‐shelf (COTS) GPSDOs are evaluated [23]. This paper is an extension of that work and provides further analysis of the performance of the constituent parts of the COTS GPSDOs.…”

Guest Editorial: Selected papers from RADAR 2022—International Conference on Radar Systems (Edinburgh, UK)

“…A fundamental challenge in the practical implementation of multistatic radar systems is the requirement for precise time and frequency synchronisation between spatially separated radar nodes and, in Ref. [2], the authors evaluate the performance of different classes of commercially available Global Navigation Satellite Systems (GNSS) timing receivers, Local Oscillators and GNSS Disciplined Oscillators to determine the limitations of using GNSS Time and Frequency Transfer as a solution to provide network synchronisation.…”

Fully digital, urban networked staring radar: Simulation and experimentation

“…It can be seen in the literature, there are various other established radar networks but few truly capable of detection of S‐UAS targets at useful ranges and few operating in urban environments. In addition, synchronisation is typically achieved using a network time protocol (NTP), white rabbit protocol [36] or GPS disciplined oscillators (GPSDOs) [37] which all either require additional infrastructure, are vulnerable to GNSS spoofing or limited in the precision and accuracy. The approach used in this work is a relatively low cost, direct signal synchronisation technique.…”