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Chasing Sub-Nanosecond Coherence: White Rabbit vs. GPS in Multistatic Radar

What does particle physics at CERN have in common with tracking ships off the coast of Cape Town? The answer lies in ultra-precise timing—specifically, how we clock distributed sensor networks.

In a doctoral thesis completed at the University of Cape Town (UCT) under the Radar Remote Sensing Group, Dr. Simon Alexander Cole Lewis put two clocking mechanisms head-to-head in a coherent multistatic radar system: GPS-Disciplined Oscillators (GPSDOs) vs. CERN’s White Rabbit Network.

Here is a look at why this comparison matters, how the test was conducted in the field, and what it means for the future of radar sensing.

The Core Challenge: Keeping Multistatic Nodes Coherent

Single-station monostatic radars rely on an internal clock to send out a radio frequency pulse and measure its return time. In contrast, multistatic radar systems use multiple spatially separated transmitters and receivers.

Working cooperatively allows multistatic systems to detect stealth targets, defeat electronic counter-measures, and achieve high-resolution spatial tracking. However, combining signals from nodes located kilometers apart requires strict spatial, temporal, and phase synchronization. If the individual clocks drift by even a few nanoseconds or introduce phase jitter, the combined radar image degrades into spatial ambiguity and noise.

Comparing the Contenders

The UCT doctoral research evaluated two Time and Frequency Transfer (TFT) protocols:

1. GPS-Disciplined Oscillators (GPSDOs): Wireless synchronization using multi-channel GPS timing receivers operating under common-view time transfer. While cost-effective and easy to deploy without physical cabling between radar nodes, satellite timing remains vulnerable to weather, signal degradation, line-of-sight blockage, and RF interference/jamming.
2. White Rabbit (WR) Network: A fiber-optic timing technology initially designed at CERN for particle accelerators. Combining Synchronous Ethernet (SyncE) with IEEE 1588 Precision Time Protocol (PTP), White Rabbit delivers sub-nanosecond precision and picosecond-level phase jitter over dedicated optical links.

Lecture 19 from the Radar System Engineering course by Dr. Robert O'Donnell.

This document contains slides from a lecture on electronic countermeasures (ECM) against radar systems. It discusses how ECM techniques like chaff, noise jamming and random pulses can be used to mask targets from radar detection by increasing clutter. It provides details on how chaff works, including its reflectivity properties and how it is dispensed. Examples are given of chaff masking an aircraft and deceiving trackers. The presentation also introduces how electronic counter-countermeasures (ECCM) can be used to counter ECM techniques.

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Lecture 18 from the Radar System Engineering course by Dr. Robert O'Donnell.

 This document provides an overview of a lecture on synthetic aperture radar (SAR). It begins with an introduction to SAR, including why it was developed due to limitations of conventional radar for imaging. It then discusses the basics of SAR and how it forms images using signal processing to synthesize a large antenna aperture. The document outlines the rest of the lecture topics which will cover SAR image formation techniques, examples, applications, and a history of the evolution of SAR from its origins in the 1950s to current systems.

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Lecture 17 from the Radar System Engineering course by Dr. Robert O'Donnell.

This document provides an overview of radar transmitter and receiver systems. It begins with an introduction and block diagram of radar transmitters and receivers. The bulk of the document then focuses on different types of high power tube amplifiers used in radar transmitters, including klystrons, traveling wave tubes, crossed field amplifiers, and magnetrons. It also briefly discusses solid state RF power amplifiers. The document concludes with an outline of topics to be covered, including receivers and waveform generators, other transmitter and receiver subsystems, and radar receiver-transmitter architectures.

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