GaN, mmWave and space to the fore at European Microwave Week
Your detailed, technical report following this year’s European Microwave Week, held in Nuremberg.
It has been evident over the past year that 5G is moving rapidly from technology concept development towards actual hardware. This was very much confirmed by the exhibits at this year’s European Microwave Week in Nuremberg, where a number of new products necessary to enable 5G – particularly at millimetre-wave frequencies – were on show on several of the stands. From semiconductor devices through new laminate materials to prototype subsystems, it seemed that almost everyone was offering some high-frequency technology to enable the prototypes that will be needed for the next generation of mobile technology to fulfil its promise of ubiquitous coverage, near infinite data rates, and very low latency, as the new 5G use cases demand.
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), as summarised in Figure 1.
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Rogers was showing new substrate materials suitable for mmWave frequencies, aimed at meeting the demand for economical circuit fabrication in these bands.
Rogers CLTE-MW laminates are ceramic filled, woven glass reinforced PTFE composites, developed to provide a cost effective, high performance material for mmWave designs including 5G. They are particularly suited for applications that have limitations in thickness due to either physical or electrical constraints. With seven available thickness options from 0.003” to 0.010” they can provide the ideal signal to ground spacing exists for mmWave frequencies. The laminates are reinforced with spread glass, which – combined with a high filler loading – helps to minimise the effects of high frequency glass weave on electromagnetic wave propagation and provides good dimensional stability. Z-axis coefficient of thermal expansion (CTE) is 30ppm/°C and loss tangent is 0.0015 at 10 GHz to enable low loss designs.
GaN devices
OMMIC stole the limelight in the compound semiconductor arena by announcing the commissioning of a new 6-inch GaN-on-Si production line at its Limeil-Brévannes facility in France, which it is promoting with a new video. Targeting telecommunications and space applications, the new capability gives OMMIC a four-fold increase in production capacity, making it the only European company able to produce both GaN and GaAs on 6-inch wafers.
OMMIC is aiming to become the third largest GaN manufacturer by 2020, forecasting sales of over €100 million. This goal is supported by a number of key partnerships, including a deal on 5G base station capability with Huawei. More than 35 technical staff have also reportedly been recruited, with further new openings to follow.
Mitsubishi Electric was showing a range of GaN devices for base stations in the 3.5GHz 5G band, and also launched at the show a Ka-band (27.5–31.0GHz) 8W GaN HEMT MMIC amplifier for satellite earth stations. The MGFG5H3001 boasts a small footprint that Mitsubishi says will help to downsize power transmitters, and to meet growing market demands for deployments in Ka-band that are capable of high output power and efficiency. The single chip integrates transistor amplifier, matching circuits and lineariser for lower distortion, and offers a linear gain of 15dB. Despite the similarity in frequency band, there was no mention of 5G applications for this device.
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Ampleon’s stand was highlighting its ‘next generation high power broadband GaN’, as well as some new Doherty amplifiers for UHF DTV broadcast and a host of RF energy products. It also presented at two relevant sessions in the conferences: Dr Sergio Pires, advanced concepts and systems group leader, presented a workshop titled “Challenges and Innovations in Transmitters of 5G MIMO Systems” on the Sunday, and innovation engineer Dr Osman Ceylan gave a paper on “A Highly Efficient GaN RF Power Amplifier MMIC Using Low-Voltage Driver” in the EuMIC conference on the Monday.
Filtronic Broadband has already been designing and manufacturing transceivers for backhaul applications in E-band (71 – 76GHz and 81 – 86GHz), and has presented papers describing the suitability of GaN for use in this frequency band in the future. Currently their GaN subsystems are aimed at the traditional 6GHz to 11GHz long-haul radio bands, but development is planned to extend this up to mmWave frequencies. In collaboration with Plextek RFI they have recently developed a demonstration 26GHz GaAs MMIC front-end module for 5G demonstration purposes. The module comprises a GaAs low-noise amplifier (LNA), power amplifier (PA) and transmit/receive switch, with low-loss RF filtering also integrated into the surface-mount package structure, which measures 10mm x 10mm. The receive path gain is 20dB across the full band, with a noise figure of 3.5dB. Transmit path gain is 19dB, and the output referred third order intermodulation (IP3) is +36dBm.
mmWave test for 5G, backhaul, and automotive
Frequently test equipment blazes the trail for new technology – after all, the new products need to be measured and evaluated before they can be released to market. It was therefore no surprise that there was significantly more mmWave test equipment on display at EuMW than ever before.
Anritsu’s Spectrum Master MS2760A series of mmWave spectrum analysers provides spectrum analysis capability up to 110GHz with an instrument that fits in the palm of the hand. Anritsu’s patented Nonlinear Transmission Line technology allows it to challenge the cost, size and performance barriers associated with traditional spectrum analysers, targeted at applications such as E-Band radio, 802.11ad/WiGig, satellite communications, electronic warfare and automotive radar as well as 5G.
For extending the range of existing handheld spectrum analysers to mmWave frequencies, the MxxH6DC Series from OML utilises the tracking generator of the spectrum analyser as an LO source and the built-in DC supply to power the harmonic mixer, providing mmWave measurement capability in waveguide bands from 50GHz to 110GHz – E-band, extended E-band, V-band and W-band.
To support the development of 5G and general wideband communications, Rohde & Schwarz presented a test solution, shown in Figure 4, which combined the SMW200A vector signal generator and FSW43 signal and spectrum analyser. The test setup was demonstrating Verizon 5GTF signals and 5G candidate waveforms such as FBMC, UFMC, GFDM or f-OFDM at frequencies up to 40GHz, with a 2GHz internal analysis bandwidth. Also the R&S NRPM over-the-air (OTA) power measurement solution is designed to calibrate the transmit output power and test the beamforming function of antennas and phased arrays. These OTA verification tests can be performed over a frequency range of 27.5 – 75 GHz, and are suitable for testing both 5G signals and standard-compliant WLAN IEEE 802.11ad and 802.11ay signals.
Further interesting demonstrations from R&S included an exclusive live preview of its production test systems for automotive radar testing, in the foyer of the exhibition. One of these was an echo generator for end-of-line production testing of automotive radar sensors. The new R&S AREG100A automotive radar echo generator supports all the automotive radar bands – 24GHz, 76GHz and 79GHz, and tests up to three customer-definable fixed radar distances plus an optional Doppler offset for simulation of radial velocity. It can be used in combination with the ATS1000 shielded chamber and associated QuickStep test execution software, to ensure fail-safe testing and continuous quality control of automotive radar sensors.
A quality automotive radome scanner (QAR) formed another part of this demonstration, specifically developed to characterize the performance of automotive radar covers such as emblem radomes and car bumpers. The new QAR uses a new imaging technique that allows very fast measurement of the reflectivity of the DUT, enabling car manufacturers to precisely locate and identify any material errors or inhomogeneous material that might impact the sensor’s performance. A frequency sweep across 75 – 82 GHz is used to measure material attenuation in the 77GHz and 79GHz automotive radar ranges.
Although not showing any new 5G capability at EuMW, Keysight Technologies recorded an important milestone towards 5G NR the following week when, in collaboration with Qualcomm Technologies, it successfully achieved a 5G data connection in a single-chip 5G modem using its Protocol R&D Toolset in combination with the Qualcomm Snapdragon X50 5G modem chipset. The 5G Protocol R&D Toolset and 5G RF DVT Toolset are two recently-announced components of Keysight’s 5G network emulation solution (NES) portfolio.
Space applications in focus
A growing interest in space applications was also in evidence at the Show. Custom MMIC was emphasising its range of space-qualified GaAs MMICs, while pointing out that in addition to its pre-qualified devices, almost all of its product range is ‘space-ready’.
Rohde and Schwarz was showcasing satellite payload, link and terminal testing for OneWeb, DVB-S2 and DVB-S2X. The R&S SMW200A vector signal generator is claimed to be the first single-device solution on the market to generate OneWeb and DVB-S2/DVB-S2X signals both at the IF and at transmission frequencies up to40 GHz, for testing components, devices and satellites in the physical layer. Another system, the R&S BTC broadcast test centre, performs testing of components, satellite systems and receivers for DVB-S2/DVB-S2X by simulating live video and data links in real time, as well as simulating IMUX/OMUX and interference scenarios. The complementary R&S SLG satellite load generator can generate up to 32 transponder signals or a single 500 MHz wideband transponder.
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