Multi-Gbit/s Data Transmission in Sub-Terahertz Range

Two multi-Gbit/s wireless communication experiments based on Schottky technology in sub-terahertz frequency range are presented. 120GHz on-off keying (OOK) transmission is achieved within lab distance with data rate up to 12.5Gbit/s. This proof-of-concept demonstration shows the capacity and potential of terahertz communication. 220GHz data transmission is further achieved in outdoor environment by the use of quadrature phase shift keying (QPSK) modulation. INTRODUCTION It is becoming highly attractive to exploit terahertz (THz) and sub-THz frequency band (100 GHz~10 THz) for high speed wireless communication since THz communication has a number of important benefits including better environment flexibility compared with the optical communication, the availability of large absolute bandwidth and small antenna aperture size. Such benefits provide increasing attractiveness in satellite cross-link in terms of space application and short-range wireless personal area networks and secure communication for ground use [1]. Although THz communication shows attractive application advantages, yet at the current stage, the enabling physical devices remain a main technical bottleneck. In order to make effort to fulfill practical cost-effective all-electronic THz communication systems, we investigated multi-Gbit/s data transmission in two frequency bands (120GHz and 220GHz) based on Schottky electronic devices, which can be readily available at a sensible price point. Firstly, we built a simple system set-up to carry out the proofof-concept data transmission experiment at 120GHz in short range. After this demonstration, a more complex 220GHz setup was proposed to achieve outdoor real-time wireless transmission, which enabled operation over practical distance range. 120GHZ DATA TRANSMISSION Fig.1 shows the 120GHz transmission experiment set-up. In the experiment, on-off keying (OOK) data signals generated by a pulse pattern generator (PPG) were fed into a self-developed 120 GHz Schottky subharmonic mixer (SHM) to transmit, and the frequency down-converted data stream was analyzed using a high sampling-rate oscilloscope and bit error detector. The transmission experiment was carried out in lab environment with a distance of 0.2m (shown in Fig. 2) and the data rate could reach up to 12.5Gbit/s with eye diagrams presenting sufficient eye opening. The eye diagram at 12.5 Gbit/s is shown in Fig. 3. Good eye diagrams and bit error rate (BER) that exceeds the threshold for forward error correction (FEC) [2] were achieved, which means further digital correction can be applied to produce much lower BER which is acceptable for practical application. Fig. 1 120GHz transmission schematic set-up. Fig. 2 Picture of 120GHz transmission experiment. 27TH INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY, NANJING, CHINA, APRIL 13-15, 2016 Fig. 3 Eye diagram at 12.5Gbit/s. 220GHZ DATA TRANSMISSION After the successful transmission at 120GHz, we pushed the frequency further up to 220GHz, which is an atmospheric window. Due to this merit, an outdoor transmission set-up which could enable operation over practical distance range was proposed (shown in Fig. 4). Albeit the lack of solid-state amplifiers, this drawback could be overcome by using high gain Cassegrain antennas and adopting self-developed low-noise 220GHz Schottky subharmonic mixers that could provide sufficient receiver sensitivity.