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GaN: The high frequency substrate suitable for 5G applications, Part 9

The trend for communications infrastructures is to have an extremely high data rate and a latency near as much as possible to zero, the 5G protocol in particular requires a substrate able to work at high frequencies to ensure to reach this goal. The answer to this question could be the GaN material, utilized as substrate to realize electronic integrated components for high speed base-station in Europe network of communications:

“Another trend was the growing availability of GaN devices to replace LDMOS in 4G base stations, as the demands for wider bandwidth, better efficiency, and higher linearity propel the adoption of this technology, especially where LTE-Advanced carrier aggregation is being deployed. The ambitious energy savings targets that form part of 5G proposals will also obviously compel the adoption of GaN, and this was being anticipated by new transistors for the 3.4 – 3.8GHz range considered to be the primary sub-6GHz band suitable for the early introduction of 5G -based services in Europe. mmWave developments: Although the 5G mmWave frequency bands have still to be formally defined, the picture of what they are likely to be is becoming clearer. The EU’s Radio Spectrum Policy Group (RSPG) has recommended the band around 26GHz as the ‘Pioneer Band’ for mmWave 5G in its Strategic Roadmap towards Europe (November 2016), and this was naturally the focus for some European vendors’ offerings. The other candidate bands where development work is taking place include the FCC licensed bands at 28GHz (27.5 – 28.35GHz), 37GHz (37 – 38.6GHz) and 39GHz (38.6 – 40GHz)” (Source: Innovate UK)

These considerations are well explained in the “RSPG18-005 FINAL” by the RSPG (see Table 1):

    • In some countries introduction of 5G in sub 1GHz is likely to be a gradual evolution of LTE rather than in newly released spectrum. As such, there may be limited opportunities to introduce a new, 5G specific coverage obligation in these bands to accelerate or extend 5G coverage. Consideration should be given as to whether competition between operators will drive a timely migration to 5G or whether regulatory intervention should be considered.
    • Coverage obligations placed on mobile network operators have generally benefitted all users of those networks. However, 5G is expected to be designed to serve different industry verticals, with network slices providing virtual private networks, potentially offering different levels of service to different customer segments based on minimum performance for characteristics such as bit rate, latency, availability, reliability, velocity.
    • Industry will define such service performance and availability requirement and Member states will have to consider the consequences in terms of coverage obligation. In the case of cross-border services, it would be helpful if common service performance and availability requirements are used across EU.
    • There has been a large focus in the definition and development of 5G on developing technology components suitable for facilitating a huge increase in data rate and capacity for urban and suburban areas; this is especially true for the development related to enhanced mobile broadband which has focused on frequency bands above 1 GHz.

(Source: RSPG18-005 FINAL)

Table 1

'The various bands under consideration for 5G above 24 GHz' (Source: RSPG Second Opinion on 5G networks)

 

“The various bands under consideration for 5G above 24 GHz” (Source: RSPG Second Opinion on 5G networks)

 

The utilization of GaN in the semiconductor field is opening the road to new unprecedented results:

“Researchers from Sweden, France, and Russia teamed on the design and fabrication of a waveguide-balanced, phonon-cooled NbN hot-electron-bolometer (HEB) mixer on a GaN buffer layer. The mixer was used in a double-sideband (DSB) receiver operating at a local-oscillator (LO) frequency of 1.3 THz with extremely low noise temperatures for analysis of signals across wide bandwidths at terahertz frequencies. While such NbN-on-GaN mixers have been developed previously for THz applications, compared to mixers on silicon (Si) substrates, little has been documented on the noise performance of such THz mixers. These researchers used the Y-factor technique to characterize mixer integrated circuits (ICs), which were fabricated by photolithography and mounted within a THz waveguide receiver assembly, and subsequently measure the receiver noise temperature.” (Source: MICROWAVES&RF) (See also Figure 1).

Figure 1

'Resistance versus temperature curve of the HEB bridges made of NbN, which was grown onto Si substrate (Tc=10.5 K) and GaN buffer-layer (Tc=12.5 K).' (Source: Study of IF bandwidth of NbN hot electron bolometers on GaN buffer layer using a direct measurement method)

 

“Resistance versus temperature curve of the HEB bridges made of NbN, which was grown onto Si substrate (Tc=10.5 K) and GaN buffer-layer (Tc=12.5 K).” (Source: Study of IF bandwidth of NbN hot electron bolometers on GaN buffer layer using a direct measurement method)

 

Do you think that the utilization of GaN in electronics could represent a great new design opportunity in terms of effectiveness and performance? Please share your thoughts and experiences with our audience.

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