Mike Weaver, Managing Director, Filtronic Broadband
MPD: Millimeter wave frequencies will be used for cellular communications for the first time in 5G. What challenges and opportunities does this present for the microwave industry?
Although this will be the first time that millimeter wave frequencies have been used to connect between handset and base station, this of course is only part of the network. The use of frequencies up to 86 GHz (E-band) is already well established in the backhaul part of the network. In many regions of the world, including Europe, more than half the backhaul links use radio links in preference to fiber. The use of radio, and in particular mmWave radio, is set to increase in 5G networks due to the higher density of base stations, higher capacity, and the need for rapid deployment at minimum cost.
The promises being made for mmWave technology in smart phones are probably being overstated, as the physical limitations of transmitting signals at very high frequencies need to be recognized. Millimeter wave signals—a term that traditionally refers to frequencies between 30 GHz and 300 GHz, but in 5G terminology now used to include bands from 24.5 GHz upwards—require a clear line of sight between the two ends of the link in order to achieve high data rates. In fixed links, the transmission paths can be readily planned and managed, but mobile applications present a very difficult environment, since it will be impossible to predict what obstacles will be present at any time between a smartphone and the base station. A very “smart” phone will be required to find and maintain a clear path to the base station under rapidly changing conditions, and it will still not be possible to achieve this continuously. One of the major challenges will therefore be to develop a low cost, low power consumption technology for beam forming and steering, together with the necessary real-time software and signal processing to manage this.
5G hype is promoting the expectation of multi-Gbps data rates to each phone. I belive that in practice these rates will represent the very peak of the capability, and will rarely if ever be seen by users in the real world.
The first 5G phones on the market will almost certainly operate in the bands below 6 GHz, and will exploit high order modulation and multichannel techniques to push data rates towards the Gbps range.
There is undoubtedly a major opportunity for mmWave technology in 5G also to increase the capacity of the backhaul part of the network. 5G will require a massive increase in both density and data rate to transport data from base stations into the core network. Fiber is often thought to be the dominant transport medium, but the reality in many countries is that microwave links connect the majority of radio sites, and this is not likely to change. This presents a challenge in terms of spectrum allocations. While frequency bands up to 86 GHz are under consideration for use in 5G cellular communications, it must be recognized that sufficient spectrum must be preserved to deploy backhaul networks for both 5G and also the legacy 3G and 4G networks.
It is clear that the bandwidth allocated to fixed wireless links must be increased, and this can only be found at even higher frequencies. Frequencies up to 175 GHz (e.g. W-band and D-band) are now under serious consideration within the various regulatory organizations. Overcoming the challenges of designing and manufacturing cost-effective equipment operating at these higher frequencies presents a great opportunity for the mmWave industry. Filtronic has recently won funding under Innovate UK’s “Accelerating the Commercial Application of Compound Semiconductors” Competition for a project to develop techniques to enable cost effective design and manufacture of radios operating up to 175 GHz for future application in 5G networks.
MPD: What RF and microwave technologies do you feel will have the greatest impact in our industry overall between now and 2020?
High speed SiGe BiCMOS and SOI CMOS are demonstrating encouraging results at mmWave frequencies, although the maximum output power is limited due to the low breakdown voltage of silicon. The noise figure is also worse than that offered by III-V technologies, so these will continue to play a vital role in 5G. In particular, GaN will grow in importance, although the operating frequency needs to be increased beyond what has been achieved by today’s mainstream processes if it is to displace GaAs in true mm-Wave applications.
Aside from semiconductors, ultra-high precision additive manufacturing techniques, and novel passive structures such as metamaterials will be essential to realize low cost mmWave filters, diplexers and antennas.
MPD: After years of hype and little to show for it, IoT networks are actually being deployed in a variety of applications. Do you believe IoT is a major opportunity for the RF and microwave industry? If so, why and if not, why not?
The main RF challenge for massive IoT will be in achieving a satisfactory range with minimal power consumption at a very low cost. I think this will require the use of sub-1 GHz silicon based IC technology. There will be opportunities for shorter range higher data rate applications; these will probably evolve from Bluetooth®/ZigBee technologies.
IoT presents a huge opportunity for the RF semiconductor industry, but there are probably fewer opportunities for the microwave industry.
MPD: We believe that the defense industry will retain its crucial importance to the RF and microwave industry regardless of overall DoD budget constraints. Do you agree with this statement? Either way, please explain your reasoning.
We strongly agree with this statement! In fact, the defense and aerospace side of our business is growing, and we believe it will continue to do so for several years to come. Although UK Ministry of Defence (MoD) spending has been subject to extreme budget cuts over the last few years, there are still a number of European development programs around that require product to be designed and built within in Europe, and we are well-placed to support these requirements. In addition, the defense/aerospace customers are now fully embracing GaN technology, and our considerable experience with “chip & wire,” and with laminate packages and modules, means that we have the skills to truly add value to these programs. We are also seeing increased activity in mmWave requirements for defense applications. Military communications systems are becoming ever more data hungry, and therefore our E-band, 10Gb/s links are an attractive alternative to the traditional microwave links to provide increased capacity.