Meanwhile, NXP sees SiGe surge for mobile WLAN and 5G

While business in automotive is experiencing an unanticipated slowdown, NXP fi nds its RF front-ends in high demand.

Nieke Roos

In the shadow of its disappointing Q1 results, NXP also released two positive notes. In April, the company made public a collaboration with Murata to deliver the industry’s  rst RF front-end modules designed with the latest Wi-Fi 6 standards. Followed in May by an announcement that these very modules have been designed into the Xiaomi Mi 10 5G smartphone.

NXP’s RF front-end solutions are based on silicon-germanium (SiGe).  is technology has the advantage over CMOS that it enables a higher output power at radio frequencies, at the same cost base. Compared to silicon-on-insulator, another alternative, it allows for a higher output power level, combined with better power e ciency.

While NXP’s automotive activities are struggling as the corona pandemic forced car manufacturers and their suppliers to halt operations, its SiGe business is booming.  e ICN8 fab in Nijmegen and the jointly owned SSMC factory in Singapore are producing silicon-germanium chips at full throttle. “Our customers are pulling them out of our hands,” says Rob Hoeben, Senior Director of Marketing for the product line Smart Antenna Solutions (SAS) within NXP’s business line Radio Power.

SAS delivers integrated RF front-ends for mobile and wireless infrastructures. “We’re NXP’s Qubic center for product creations – Qubic being our SiGe process technology,” states Hoeben. “We’re focusing on mobile WLAN and 5G – both sub-6 GHz and mm-wave.  ere lies SiGe’s sweet spot: everything RF or mm-wave below 1 or 2 W output power.”

Number one

In a mobile handset application, NXP’s front-end IC links the antenna to the WLAN system-on-chip. “It contains a low

Credit: NXP

noise ampli er for the receive path, to minimize the noise and optimize the sensitivity in the rest of the chain,” explains Hoeben. “In the transmit path, it delivers that extra output power you can’t get with CMOS. We can put the ICs in a small discrete QFN housing, for use very close to the antenna, in a complete front-end module, or customers can buy them as chip-scale packages and integrate them with a third-party SOC into a system-in-package.”

According to Hoeben, NXP is the world’s number one front-end supplier for Wi-Fi 6 and 6E. “Wi-Fi 6 connects more users and employs an upgraded modulation technique, which means a huge increase in data rate per user and better battery performance with the same data rate. 6E adds to that 1.2 GHz of extra spectrum at the top end of the 5 GHz band, ie from 6-7.2 GHz.  at’s good news for Wi-Fi and perfect for SiGe since this technology allows for making a broadband front-end that performs equally well across the entire range from 5-7 GHz. Customers can take a Wi-Fi chip and set it to 5 or 6 GHz, put our IC in front of it and it will work independently of the selected frequency. With a technology like GaAs, which is much more narrow banded, you need multiple power ampli ers – obviously, a much more expensive solution.”

Without giving exact numbers, Hoeben can divulge that NXP is selling hundreds of millions of RF front-end ICs in the mobile space. “ e big companies make 100 million handsets of each of their models, all having three of our chips inside. So one such customer alone represents 300 million units.”

Deploying rapidly

In 5G, the  rst bands deployed are sub-6 GHz.  ese basically cover the same frequencies as 4G but with a better modulation technique, resulting in higher data rates. “With SiGe, we have a play in base stations for sub-6 GHz,” Hoeben points out. “Such base stations not only contain GaN or LDMOS power ampli ers, but also pre- drivers, LNAs and gain blocks – typical products made in SiGe, in Qubic. For mmwave – 26, 28 and 39 GHz – we’re developing beam-forming ICs, which are the frontends of those antennas.”

Although the numbers aren’t comparable to the mobile space, 5G is an equally important target area for NXP’s SiGe e orts. “Sub-6 GHz is currently deploying very rapidly in China, and in Europe, it’s taking o as well,” Hoeben notes. “In North America, where sub-6 GHz spectrum is scarce, we’re seeing the  rst mm-wave deployments, with  xed wireless access in regions without cable or  berglass as a  rst real commercial use case.”

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Optimizing for Wi-Fi 6

Wi-Fi 6, also known as 802.11ax, is the nextgeneration standard in Wi-Fi technology. What’s exciting about it is that it expands on 802.11n (Wi-Fi 4) and 802.11ac (Wi-Fi 5) by improving data capacity, the number of connected user devices per node and throughput over the full RF range. Wi-Fi 6 offers theoretical speeds of up to 10 Gb/s. The new standard also implements orthogonal frequency division multiple access (OFDMA), which runs in full-duplex (up and downstream), multi-user, multiple-input-multipleoutput (MU-MIMO). It supports twelve streams, allowing each stream to service multiple devices.

Under the Wi-Fi Alliance’s certification program, designs can be submitted for certification. This is driving both indoor and outdoor Wi-Fi 6 manufacturers to certify and deploy infrastructure with certified units. These manufacturers, then, need a vendor with both an indoor and outdoor Wi-Fi 6 portfolio covering front-end solutions plus filtering – preferably in the context of a large portfolio that also includes multi-protocol solutions focusing on Wi-Fi/IoT coexistence. To benefit from the improved capabilities, there’s also a need for devices with higher levels of linearity, interference mitigation and lower power consumption – all in a smaller form factor. Wi-Fi 6 manufacturers require the RF front-end devices to achieve these parameters in order to meet certification program demands.

With the rise in data throughput (four times greater than Wi-Fi 5) and the larger number of users per node (four times the Wi-Fi 5 capacity), the RF design portion of a Wi-Fi end-product has increased in complexity. Not only has the modulation scheme increased to 1024 QAM, quadrupling wireless speeds compared to Wi-Fi 5, but receiver sensitivity and power amplifier linearity have become more challenging.

The increase in QAM means more challenging RF linearity requirements – as high as -47 dBm error vector magnitude (EVM) for some manufacturers. To address this, optimized RF front-end (RFFE) devices can be used having EVM margin to

The RF design portion of a Wi-Fi 6 end-product has increased in complexity

ensure end-product certification. The increased sensitivity specifications mean a lower noise figure (NF) in the receive path is a must-have. With both 5G and Wi-Fi 6 standards demanding lower power consumption targets, the added challenge is to meet the above specs while keeping end-product power consumption at a minimum. Furthermore, new coexistence challenges in 2.4 and 5 GHz bands increase the need for specialized filtering.

EVM and noise are key parameters to focus on in a Wi-Fi 6 product or application. EVM is a measure used to quantify the performance of a digital radio transmitter or receiver. Noise (including phase noise), distortion and spurious signals can degrade EVM. Because real-world Wi-Fi applications are pulsed (the PA pulses on each time it transmits data, then pulses off to save power), design engineers should focus their attention on dynamic EVM values on product datasheets, as these values accurately reflect how a PA in a Wi-Fi system operates. Thus, choosing components with dynamic EVM levels measured in pulse modes are the best choice.

Another recommendation is to choose a product that covers 2.4 and 5 GHz. These products include embedded filter solutions to address band edge and coexistence. The overall benefit of band edge filters is RF range and quality of service without interference from Bluetooth, microwave ovens, cellular phones and such. There are also products that address the emerging expansion of Wi-Fi 6 in the 6 GHz space (also called Wi-Fi 6E).

Lastly, it’s important to note the trend to integrate Wi-Fi and IoT (ie Zigbee, Thread and BLE). The smart home space is seeing this merger into one package design or home network – bringing together the smart home, the internet, lighting control, voice activation control, home automation and security. Products that offer these two technologies in one solution, reducing customer complexity and design, represent an advantage in getting to market faster and with confidence.

Wi-Fi 6 is up and running, offering distinct advantages over its predecessors. Designers who are savvy enough to optimize their application designs for Wi-Fi 6 will have the competitive edge by unlocking the full potential of this new standard.

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