RESEARCHERS in Japan have achieved the world’s fastest wireless transmission speeds thanks to a new CMOS wireless transceiver chip which operates across a broad range of frequencies.
The researchers from the Tokyo Institute of Technology and Fujitsu were able to achieve wireless transmission speeds of 56Gbps, thanks to the CMOS wireless transceiver chip that can process signals at high speeds with little loss across a broad range of frequencies, from 72 to 100GHz. The researchers also developed the technology to modularise the chip.
Optical fibre has been the go-to technology for networks that link base stations, in order to deal with the large increase in data traffic from the widespread use of smartphones and related mobile devices.
However, it is not always feasible to install a network of optical fibre cables, thanks to environmental restrictions such as urban areas or areas surrounded by rivers and mountains.
High-speed wireless transceiver technologies that utilise the millimeter-waveband (30-300GHz) have been developed to provide alternative connectivity for large-capacity communications.
This technology makes it possible to have high-capacity wireless communications equipment that can be installed outdoors in applications where fiber-optic networks would be difficult to lay.
High-capacity wireless transmissions work well with broad frequency ranges, particularly in the millimeter-waveband, where there are few competing wireless applications. However, the high frequencies at these wavebands means designing CMOS integrated circuits for that purpose has been a challenge, as the circuits need to be designed to operate near their limits.
It has also been difficult to develop low-loss transceiver circuits that modulate and demodulate broadband signals into and out of the millimeter-waveband with high quality, and low-loss interface circuits, which connect the circuit board to the antenna.
The newly developed CMOS wireless transceiver chip and the wireless module that includes it are comprised of two key technologies.
The first is a low-loss, high-bandwidth transceiver circuit, developed by the Tokyo Institute of Technology. The data signals are split in two, with each converted to different frequency ranges, and then recombined.
Each signal is modulated into 10-GHz wide bands, with the low-band occupying the 72-82GHz range, and the high-band occupying the 89-99GHz range.
This technology enables modulation on an ultra-wideband signal of 20 GHz, with low noise and a similar range in the ratio between input and output power as existing 10 GHz band methods, which results in high-quality signal transmissions.
Alongside the circuit, Tokyo Institute of Technology also developed an amplifier to send and receive as radio waves signals converted to the millimeter-waveband. The ultra-wideband amplifier for 72 to 100GHz was designed with circuit technologies that stabilise the amplification ratio by feeding the amplitude of the output signal back to the input side for signal components whose amplification ratio decreases based on frequency.
The second part is modularisation technology for the circuit.
The signal converted to the millimeter-waveband by the semiconductor chip is transported over the circuit board's signal path and supplied to the antenna. Because the antenna is made out of a waveguide (a metallic cylinder), there needs to be an ultra-wideband, low-loss connection between the printed circuit board and the waveguide.
Fujitsu Laboratories and Tokyo Institute of Technology developed an interface between the circuit board and waveguide that uses a specially designed pattern of interconnects on the printed circuit board to adjust the impedance for the ultra-wideband range, effectively reducing the loss in the desired frequency range.
In this development project, Tokyo Institute of Technology was primarily responsible for reducing transceiver-circuit losses and developing broadband technologies, while Fujitsu Laboratories mainly handled modularization technologies.
Indoor data-transfer tests were conducted, with two modules facing each other separated by a distance of 10 cm. These tests achieved data-transfer rates of 56 Gbps, the fastest wireless transmission speeds in the world, with a maximum loss of 10 percent between the waveguide and circuit board.
Fujitsu Laboratories aims to have a commercial implementation of wireless trunk lines for cellular base stations around 2020.