SPEAR-BF: Wideband Multi-Channel D-Band Beamformer based on the RFSoC Platform
The sub-THz spectrum, including the D-band (110- 170 GHz), has emerged as a promising frontier for future wireless systems, offering unprecedented contiguous bandwidths for high-capacity links as well as new opportunities for dynamic spectrum sharing and access. However, experimental research in this band remains limited by the lack of flexible, real-time, wideband platforms that can support both agile waveform generation and multi-channel beamforming under realistic over-the-air (OTA) conditions. This paper presents the design, implementation, and experimentation of SPEAR-BF, a wideband, multi-channel software-defined radio (SDR) platform operating in the D-band, integrating the Xilinx RFSoC ZCU216 and the D-band CHARM front end modules. To address the challenges of real-time wideband streaming, we introduce a memory-based architecture featuring hardware-assisted direct memory access (DMA), enabling the processing of long-duration waveforms beyond on-chip memory limits. The system also incorporates a flexible FPGA-based beamforming IP and a Python-centric software framework (PYNQ) for rapid prototyping. The platform supports fully digital beamforming with up to eight transmit channels and an aggregated bandwidth of up to 1.2 GHz. We evaluate SPEAR-BF through extensive OTA experiments at 135 GHz, demonstrating scalable and robust single- and multi-antenna beamforming configurations, phase-coherent beamforming, and support for various high-order modulation orders (e.g., 64-QAM over 600 MHz of instantaneous bandwidth). By combining wide-band real-time streaming, reconfigurable digital beamforming, and a Python-centric control framework, SPEAR-BF provides a practical experimental foundation for sub-THz spectrum sensing, dynamic spectrum access, and measurement-driven spectrum sharing research.
