Experimental Demonstration of a Real Time Wideband OFDM Generation in Sub-THz

Sub-terahertz (Sub-THz) wireless communications and their potential applications continue to attract significant attention and foster debate on the usage of their unused frequency bands to relieve existing spectrum congestion. However, for these next-generation networks, experimental research is limited by the lack of flexible, real-time testbeds. This study presents a real-time, multi-radio-frequency(RF) channel, cascaded software-defined radio (SDR)-based Orthogonal Frequency-Division Multiplexing (OFDM) transmission platform achieving an aggregate sampling rate of 2 x 3.84 GSPS and approximately 1.1 GHz of instantaneous bandwidth, targeting sub-THz and THz SDR testbeds. The digital transmitter architecture, including the OFDM signal processing chain and instrumentation workflow, is described in detail. A comparative case study between a conventional sub-6 GHz implementation and a 180 GHz configuration is conducted, evaluating phase noise, spectral occupancy, received average and peak power. The direct impact of sub-THz bandpass filtering, necessitated by harmonic-mixer-based upconversion, is also experimentally analyzed. Measurement results show conversion and filtering losses of up to 24.1 dB, while the system exhibits stationary phase noise levels on the order of -60 dBc/Hz, demonstrating the feasibility and limitations of real-time wideband OFDM transmission at 180 GHz. Beyond immediate current capabilities, the platform builds a foundation for the scalable integration of multiple transmitters and receivers, which is essential for the implementation, conformance, and testing of emerging sub-THz communication systems.