Imec pioneers photonic code-division multiplexing FMCW 144GHz distributed radar

LEUVEN (Belgium), MARCH 31, 2025 — In a world-first, imec – a world-leading research and innovation hub in nanoelectronics and digital technologies – has successfully built and tested a proof-of-concept photonics-enabled code-division multiplexing (CDM) frequency-modulated continuous wave (FMCW) 144GHz distributed radar system that ensures coherent chirps to remote radar units. Demonstrating successful range measurements, imec’s PoC paves the way for multi-node radar systems with superior angular resolution compared to single-node setups. Looking ahead, this technology could revolutionize 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. Yet, a major challenge has been coherently distributing the shared local oscillator (LO) signal across these nodes over long distances without interference or attenuation.

“At this week’s Optical Fiber Communications (OFC) conference, we are unveiling a breakthrough solution to this challenge,” said Ilja Ocket, who manages imec’s automotive sensing portfolio. “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 analog radio-over-fiber technology with an efficient multiplexing scheme, we ensure that radar units can seamlessly work together.”

Next-generation radar powered by two key innovations

At the heart of imec’s breakthrough lies 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 utilizing analog radio-over-fiber 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.

Future applications: automotive and other high-precision sensing use cases

Ilja 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.

These research findings were presented by imec’s Chang-Shao Shen at OFC ’25 during the session on LiDAR, Ranging, and Urban Demonstrations, held on Monday, March 31, from 10:30 AM to 12:30 PM (Pacific Time).