The digital interfaces connecting radar subsystems must handle data rates that strain the limits of electronic signaling technology. Between the ADC and the FPGA, between FPGAs in a distributed beamforming architecture, and between the digital backend and the platform mission computer, raw data flows at tens to hundreds of gigabits per second. Selecting and implementing the right interface standards is a critical architectural decision that affects system performance, latency, power consumption, and cost. This article surveys the key high-speed interface technologies deployed in modern defense radar.

JESD204B/C: The ADC-to-FPGA Backbone

The JESD204 serial interface standard has become the de facto interconnect between high-speed data converters and logic devices. JESD204B supports lane rates up to 12.5 Gbps, while JESD204C extends this to 32 Gbps per lane using PAM4 or NRZ signaling. Multiple lanes are bonded together to form a logical link carrying samples from one or more converters. Deterministic latency — the guarantee that the end-to-end delay through the link is known and repeatable across power cycles — is achieved through the SYSREF timing signal and elastic buffer management.

For a radar system with 64 ADCs each producing 16-bit samples at 2 GSPS, 32 lanes of JESD204C at 32 Gbps can carry the full 2 Tbps aggregate data rate. Subclass 1 operation, which uses SYSREF for deterministic latency, is essential for maintaining phase coherence across the array for beamforming applications.

FPGA-to-FPGA and Backplane Interconnects

In large radar signal processors, multiple FPGAs collaborate to handle the computational load. Xilinx Aurora and Intel SerialLite protocols provide lightweight, low-latency streaming links over multi-gigabit transceivers, typically operating at 10–25 Gbps per lane. These protocols implement framing, flow control, and error detection with minimal overhead, making them well-suited for the streaming data paths between beamforming, pulse compression, and Doppler processing stages.

For backplane applications, where signals must traverse connectors and several inches of PCB trace, signal integrity becomes the limiting factor. Advanced equalization techniques — continuous-time linear equalization (CTLE), decision feedback equalization (DFE), and transmit pre-emphasis — compensate for frequency-dependent losses, enabling 25–56 Gbps PAM4 signaling across legacy backplane materials.

System-Level Interfaces

Moving processed radar data to the platform’s mission computer or to other sensors for fusion requires standard networking interfaces. 100 Gigabit Ethernet (100GbE) using QSFP28 optical or direct-attach copper interfaces provides the bandwidth for raw radar video or detection-level tracks. For tightly coupled heterogeneous computing, PCI Express Gen 5 offers 32 GT/s per lane in x16 configurations for 64 GB/s of bidirectional bandwidth, enabling low-latency communication between FPGAs, GPUs, and host processors.

For future systems, the Compute Express Link (CXL) protocol built on PCIe physical layers adds cache-coherent memory sharing, allowing GPUs and FPGAs to directly access each other’s memory without explicit DMA transfers — a capability that dramatically simplifies the programming model for heterogeneous radar processing.