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Innovative ultra-BROadband ubiquitous Wireless communications through terahertz transceivers

Periodic Reporting for period 3 - iBROW (Innovative ultra-BROadband ubiquitous Wireless communications through terahertz transceivers)

Reporting period: 2017-01-01 to 2018-06-30

The demand for broadband content and services has been growing at tremendous rates, and predictions indicate that wireless data-rates of multiple tens of Gbps will be required by the year 2020, essentially for short-range connectivity. Currently available wireless technology cannot support these future demands, and so there is an urgent need to develop new technology platforms that are cost and energy efficient to enable ubiquitous ultra-broadband wireless communications seamlessly integrated with high-speed fibre-optic networks, paving the way for 100 Gbps datarates in the long term. The frequency spectrum currently in use is not expected to be suitable to accommodate the predicted future data-rate requirements, and therefore there is a need to embrace higher frequency bands, above 60 GHz and up to 1 THz.

iBROW aims at developing a novel, low cost, energy-efficient and compact ultra-broadband short-range wireless communication transceiver technology, capable of addressing predicted future network usage requirements. This will be pursued through the exploitation of Resonant Tunnelling Diode (RTD) devices which represent the fastest pure solid-state electronic devices operating at room temperature with reported working frequencies exceeding 1 THz. Through the development of a unified technology that can be integrated into both ends of the wireless link, namely consumer portable devices and fibre-optic supported base-stations, the project aims at increasing the RTD output power, optical detection efficiency and energy efficiency at target frequencies, developing a methodology for low cost RTD manufacturing on a silicon platform, photonic integration and packaging, as well as identifying appropriate communication methods and architectures to enable its deployment in 10 Gbps short-range wireless communication devices in short term and paving the way for 100 Gbps in long term for both the mm-wave and THz frequency bands, seamlessly integrated with optical fibre networks
iBROW is a collaborative research project supported by the European Commission through Horizon 2020. The project will address the growing requirement for high bit rate short range wireless communication. It is expected that data traffic from wireless devices will soon exceed that from wired devices. Most of this traffic is video, with the fraction of high resolution video steadily increasing. Forecasts suggest that wireless data rates of multiple tens of Gbps will be required with a few years and this demand cannot be met with current technology.
The iBROW consortium believes that resonant tunnelling diode (RTD) transceiver technology could provide the solution. This low cost simple wireless transceiver architecture can achieve 10 Gbps by exploiting the mm-wave and THz frequency spectrum, and up to 100 Gbps is feasible in the longer term.
More information is available on the project website (www.ibrow-project.eu).

A summary of public results is given below:

High power RTDs
Several world record power devices have been demonstrated, exceeding the project targets. UGLA has achieved a 312 GHz RTD oscillator with 1.1 mW output power. World record high power 9 GHz opto-RTD oscillators (35 mW) have also been demonstrated, which are important steps on the route to higher powers and efficiencies and for demonstrations of longer transmission distances.

RTD simulation software
RTD/RTD-LD circuit simulation package has been considerably extended and improved at UALG/Lisbon, and usable versions of the RTD I-V fitting application and the RTD/RTD-LD circuit simulation package completed.

RTDs on silicon
iBROW has achieved its objectives on this topic and delivered the first RTD devices on silicon using both direct growth silicon substrates and bonded wafers with inverted RTD structures. The consortium believes that this is the first time that such structures have been reported.

10 Gbps RTD-LDs
Electronic RTDs were packaged as a wireless transmitter with integrated antennas both as a hybrid circuit demonstrator and as a full package.

RTD-PDs as transmitters
For the first time an RTD-PD oscillator has been evaluated when transmitting modulated signals using advanced modulation formats (QPSK, 16-QAM etc.).

Demonstration
RTDs were used in transmission systems in a series of ground-breaking experimental demonstrations. The new state-of-the-art was achieved for both W-band (84 GHz) and J-band (300 GHz) transmission, allowing 1.5 Gbps HD video transmission over 20 m. In addition iBROW has shown the first ever video transmission using RTD-PDs.

Dissemination
During this period the dissemination activity has been increased further, with several newsletters, a seventeen conference papers and two journal papers (with several more currently under review). iBROW also had a very strong presence at European Microwave Week 2017, including a booth where among others 300 GHz oscillators were show-cased. The iBROW workshop (23-24 Apr-2018; Glasgow, UK) was an undoubted highlight of the project which attracted 85 researchers from across the world including some of the biggest names in the field.

Standards
As a result of intense efforts and multiple presentations to the appropriate standards groups, the new IEEE Std. 802.15.3d-2017 – the world-wide first standard for wireless communication at 300 GHz was strongly based on iBROW-based proposals.
The project has achieved success right across its broad and ambitious work programme, including the following highlights, world firsts and new state-of-the-art breakthroughs:

• Improved RTD devices
o New state-of-the-art in RTD power and efficiency for e-RTDs and RTD-PDs
o RTDs successfully demonstrated from direct epitaxial growth on silicon substrate
o First ever RTDs from direct silicon wafer bonding and improved bonding process developed
• New developments in the application of RTDs in wireless networks
o RTDs used to drive LDs and RTD-PDs used as photo-detectors at GHz frequencies
o Improved understanding of electronic/photonic interfaces and clear suggestions f or improved future designs
• Practical implementation of RTDs for commercial systems
o 10 Gbps RTD-LDs packaged and designs completed for RTD-PD packaged devices
o Ground-breaking simulation and experimental channel modelling to improve understanding of the application of THz communications
o Important steps towards application of massive MIMO
• Direct application of RTDs in wireless communications systems
o First ever transmission using RTD-PDs with advanced modulation formats (QPSK, 16-QAM and OFDM)
o Demonstration of RTD synchronisation using injection locking mode
• New state-of-the-art achieved for W-band (84 GHz) and J-band (300 GHz) transmission
o 15 Gbps over 50 cm with correctable BER using e-RTDs (84 GHz)
o 1.5 Gbps over 20 m HD video transmission using e-RTDs (300 GHz)
o 16 Gbps over 30 cm with correctable BER using e-RTDs (300 GHz)
o First ever DVB-T audio/video transmission using RTD-PDs (10 GHz).

These results allow the conclusion that the RTD oscillator proposed in iBROW is a promising technology for the implementation of future high data-rate wireless communication systems, in short range applications, using the significant spectral availability in sub-THz frequencies.