Scientists at Tokyo Institute of Technology have built a 28GHz transceiver that can be used for stable high-speed 5G communications with a new type of beam steering.
Most state-of-the-art transceivers designed for 5G use RF phase shifters. Accurate phase shifting is important because it allows the transceiver to guide the main lobe of the radiation pattern of the antenna array and so "point" the antenna array in a specific direction to maximise the link budget.
Instead, the team from the Tokyo Institute of Technology, led by Associate Professor Kenichi Okada, developed a 28GHz transceiver employing a local oscillator (LO) phase shifting approach. Rather than using multiple RF phase shifters, the transceiver shifts the phase of a local oscillator in steps of 0.04° with minimal error. This allows for a beam-steering resolution of 0.1°, which is up to ten times btter than previous designs, allowing a higher throughput.
This LO phase shifting approach solves another problem of using multiple RF phase shifters: calibration complexity. RF phase shifters require precise and complex calibration so that their gain remains invariant during phase tuning, which is a very important requirement for the correct operation of the device. The situation becomes worse as the array increases in size. On the other hand, the proposed phase shifting approach results in a gain variation that is very close to zero over the entire 360° range.
The transceiver was implemented in a circuit board measuring only 4 mm × 3 mm using minimal components and provided a data rate they achieved was approximately 10 Gb/s higher than that achieved with other methods, while maintaining a phase error and gain variations an order of magnitude lower.
The results of this study are being presented at the 2018 IEEE Radio Frequency Integrated Circuits Symposium in the RMo2A session. The proposed LO phase shifting approach will hopefully help to bring forth the much-anticipated deployment of 5G mobile networks and the development of more reliable and speedy wireless communications.
Tokyo Institute of Technology - 東京工業大学