NTT Corporation and Keysight Technologies have announced a groundbreaking achievement in sub-THz communication at the 2025 IEEE MTT-S International Microwave Symposium (IMS2025) in San Francisco. The generation of a high-power, high-speed modulated signal in the 300 GHz band at a world-record data rate of 280 Gbps, marking a significant leap forward in 6G development.
This breakthrough stems from a jointly developed wideband amplifier module that covers the full J-band (220–325 GHz) and a measurement system incorporating Keysight’s digital pre-distortion (DPD) technology to precisely compensate for signal distortion. The resulting signal achieved an output power of 0 dBm, approximately eight times higher than previous systems. In a technical presentation at IMS2025, NTT and Keysight detailed how their system overcomes longstanding challenges in J-band amplification and linearity. These innovations pave the way for next-generation wireless systems operating at sub-terahertz frequencies, enabling ultra-high data rates, extensive device connectivity, and advanced radar sensing capabilities.
In 6G, the sub-terahertz waves (radio waves in the 100 GHz to 300 GHz frequency band) offer access to wide bandwidths, are expected to enable ultra-high-speed wireless communication, and high-precision radar sensing. For the research, development, and practical implementation of systems using sub-terahertz waves, system validation and evaluation using modulation signals are essential.
In the 300 GHz band—anticipated for use in ultra-high-speed wireless communications exceeding 100 Gbps— WR3.4 waveguide in the J-band (220 GHz to 325 GHz) is commonly used as input/output interfaces for measurement equipment. Therefore, in the development of wireless communications and radar systems using the J-band, it is crucial to have a signal generation system that supports the J-band and can generate high-power, high-speed modulated signals.
However, amplifying signals in the J-band is technically demanding, and as the signal speed and power increase, the adverse effects of signal distortion become more significant. These challenges have made it difficult for conventional signal generation systems to achieve both high output power and high modulation speed simultaneously.
Research Achievement
To realize an evaluation signal generation system capable of producing high-speed, high-power modulated signals in the J-band, NTT, NTT Innovative Devices, and Keysight collaborated on the research and development efforts.
NTT designed and developed a new amplifier integrated circuit (IC) equipped with a wideband impedance matching circuit and a low-loss combiner circuit (Figure 1(a)). This amplifier IC was designed using a high-speed InP-based compound semiconductor, originally developed by NTT. Thanks to this circuit configuration, low-loss signal combining across the full J-band—previously a major technical challenge—was achieved, enabling high output power across the entire J-band frequency range.
Furthermore, by applying the distortion compensation technology developed by Keysight to the amplifier module jointly developed by NTT and NTT Innovative Devices, a signal generation system was constructed that successfully combines wide bandwidth with high linearity (Figure 2). As a result, high-speed, high-power signal generation was achieved.
NTT Innovative Devices manufactured the amplifier IC designed by NTT using the aforementioned InP-based compound semiconductor. The IC was mounted in a low-loss J-band waveguide package also designed by NTT, resulting in the development of an amplifier module that was provided for this experiment (Figure 1(b)). This amplifier module covers the entire J-band and achieves a maximum output power of +9.1 dBm.
Keysight's Vector Component Analyzer
Keysight contributed its proprietary system for measuring signal distortion characteristics (Vector Component Analyzer) and its high-precision distortion compensation signal processing technology, known as Digital Pre-Distortion (DPD) (Figure 2). This technology measures the distortion generated in the system and pre-corrects the input signal to reduce distortion in the output. In this study, DPD was successfully applied in the 300 GHz band, achieving the world’s highest data rate to date in this frequency range.
Through these efforts, the team succeeded in generating a modulated signal at 280 Gbps (35 GBaud 256-QAM)—the highest reported data rate in the 300 GHz band (Figure 3). The output power reached 0 dBm, approximately 8 times higher than that of previous records (−9 dBm), marking a major step forward in generating practical high-power signals (Figure 4).
In this recent development, signal processing was used to feed back test signals from the output side to the input side in order to compensate for signal distortion. Looking ahead, it is planned to explore the application of feedforward distortion compensation using distortion models, which would enable simpler and more flexible signal generation without the need for test signal feedback.
NTT will also continue to develop and commercialize devices, equipment, and signal processing methods aimed at achieving even higher-speed and higher-power signal generation. Through these efforts, NTT & Keysight aim to accelerate research and development of systems utilizing sub-terahertz waves. Notably, the amplifier module used in this experiment is already being commercialized by NTT Innovative Devices.
This innovation is expected to accelerate the industrial deployment of sub-terahertz systems, not just for wireless backhaul and fronthaul, but also for advanced radar, imaging, and high-capacity short-range communications in future 6G infrastructure. As 6G research intensifies globally, this world-record demonstration by NTT and its partners signals a crucial step toward commercially viable, high-performance sub-terahertz communications.
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