The system ensures coherent chirps to remote radar units and imec’s PoC is seen as helping to pave the way for multi-node radar systems with superior angular resolution compared to single-node setups. Looking ahead, this technology could help to revolutionise next-generation driver assistance solutions and other high-precision sensing applications.
The automotive industry, in alignment with initiatives such as Vision Zero, is pushing for ever more advanced safety features, enabled by technologies like high-precision radar. Achieving higher radar accuracy – through enhanced angular resolution – requires multiple radar nodes working together. However, a major challenge has been coherently distributing the shared local oscillator (LO) signal across these nodes over long distances without interference or attenuation.
At the upcoming Optical Fiber Communications (OFC) conference will be unveiling this breakthrough solution. Commenting Ilja Ocket, who manages imec’s automotive sensing portfolio, said, “We are the first to build and test a functional proof of concept for a photonics-enabled, two-node 144GHz Hadamard CDM distributed FMCW radar. By combining analogue radio-over-fibre technology with an efficient multiplexing scheme, we ensure that radar units can seamlessly work together.”
At the heart of this development is a phase encoder leveraging code-division multiplexing. Each node is assigned a unique code sequence for slow-time binary phase modulation, which – in combination with phase-encoded Hadamard code-division waveforms – allows multiple radar nodes to transmit signals over the same bandwidth simultaneously. This CDM-based approach is particularly novel for distributed radar systems, offering a straightforward implementation and superior scalability.
Equally transformative is imec’s optical signal distribution method. By integrating the phase encoder directly into the optical distribution network and utilising analogue radio-over-fibre technology, the system enables low-loss transmission of the LO signal over long distances. On top, this greatly reduces electromagnetic interference – a common limitation of conventional RF-based signal distribution – while maintaining the signal integrity necessary for coherent multi-node radar operation.
According to Ocket, “Our proof of concept demonstrated successful range measurements and the ability to separate monostatic and bistatic responses, validating both our setup’s potential and the viability of CDM for coherent photonic distributed radar systems. As part of this long-term research effort, we now plan to expand the system from two to four radar nodes to further evaluate improvements in angular resolution and scalability.”
One future application of this technology is in the automotive sector, where it could enable high-resolution, 360° radar sensing for advanced driver-assistance systems (ADAS). Other potential use cases benefitting from its high range and angular resolution include indoor sensing, biomedical imaging, and vital sign monitoring.
