The ULTRAWAVE concept is based on combining, for the first time, a Point-to-multiPoint (PtP) layer at the D-band (141 – 148.5 GHz) fed by high capacity Point-to-Point (PtP) links at the G-band (275 – 305 GHz). This combination allows the efficient provision of a high throughput backhaul enabling high density cell deployment for 5G and future generations of mobile networks (100 Gbps/km2). The concept is shown in Figure 1. Further information on ULTRAWAVE concept and the challenging requirements for its newly developed components can be found here.
Fig. 1.- ULTRAWAVE layer concept based on a D-band PtmP plus a G-Band PtP high capacity link.
To build this unique wireless system which will enable full exploitation of the upper millimetre-wave spectrum new vacuum electronics devices in combination with solid state and photonic subsystems. A full set of devices based on these three technologies with performance beyond the state of the art, will be designed, fabricated and assembled. In particular, the main technological advancements and challenges of the project are:
Traveling wave tubes amplifiers (TWT)
Traveling Wave Tubes are the only devices able to provide power at Watt level in a multi-GHz band at millimetre waves. Two novel TWTs will be designed and realized at the D- and G-bands, respectively, to enable the ULTRAWAVE ultra capacity layer. Technologies and process at the state of the art will be adopted. The TWTs will be designed and fabricated at Lancaster University, UK, in collaboration with Goethe University of Frankfurt, Germany and HF Systems Engineering GmbH, Germany.
The development of TWT operating at such high frequencies is a considerable challenge that requieres high precision alignment and fabrication of the electromagnetic structures, new cathodes enabling high current density, novel circuit designs having strong beam-wave interaction, high vacuum levels and nanoscale surface roughness of the metal walls to provide low loss.
Fig. 2.- Traveling Wave Tube concept.
New MMIC chipsets
The D-Band (141 – 148.5 GHz) chipset will be build and designed by the new D004IH 40 nm process developed at OMMIC, France. The chipset includes the Low Noise Amplifier (LNA), the up-converter and the down-converter. The MMICs will be designed at University of Roma Tor Vergata, Italy. The power amplifier to drive the TWT and for the terminal will be designed and fabricated by Ferdinand Braun Institute (FBH), Germany using 0.8μm InP DHBT (double heterojunction bipolar transistor).
                              
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Fig. 3.- a) 2×25μm mHEMT . b) Double mushroom gate structure developed with OMMIC D004IH process with 40 nm gate to be used for the LNA.
The G-band chipset will include a power amplifier as driver for the TWT and a down converter both to be designed and fabricated by FBH with an advanced process with a maximum frequency ~ 500 GHz. A LNA utilizing the OMMIC 40nm process will be designed by University of Rome Tor Vergata and realized at prototype level by OMMIC as first trial of an industrial process for G-band LNAs.
G-band photonic transmitter
A G-band photonic transmitter for the Transmission Hub has been designed and fabricated by Universidad Politécnica de Valencia, Spain. Fiber optic technology for wireless systems offers extremely wide bandwidth which allows to transmit several channels in parallel while tuning the central frequency. The G-band transmitter will be based on the heterodyne beat between two spectral lines in a unitravelling photodiodes (UTC-PD). Additional information about the photonic transmitter can be found in ULTRAWAVE Deliverable 5.2.
