By Claus Hetting, WiFi NOW CEO & Chairman
Tri-band Wi-Fi 7 promises huge performance increases over dual-band Wi-Fi 6 and 7 but the close proximity of the 5 GHz and 6 GHz bands presents a formidable engineering challenge, in particular for wide channels, higher order modulation, and Wi-Fi 7’s marquee feature MLO. FEM and RF filter components leader Qorvo says Wi-Fi 7’s best features may hardly work at all without the right ‘high Q’ filters. Here’s the explanation.
The Wi-Fi industry is – of course – focused on using all available unlicensed spectrum in 5 GHz and 6 GHz to deliver the best possible performance but as it turns out, the two bands and associated Wi-Fi channels are laid out in such a way as to conjure up a significant RF engineering challenge: Only 110 MHz separates the top of typically used 5 GHz channels and the bottom of the typically used 6 GHz (UNII-5) band. The potential for the AP to interfere with itself is real and significant, Qorvo says.
“Self-generated interference arises in 5 GHz and 6 GHz APs because transmitters and highly sensitive receivers for both bands are incorporated into the same device. In some cases receivers are desensitised as 6 GHz signals bleed into the 5 GHz band, and vice versa, raising the noise power and resulting in dropped packets. In the worst case, a radio may back off because it will interpret the received signal as coming from a different device,” says Jeremy Foland, Senior Marketing Manager at Qorvo.
That means the requirements for isolating the bands are much, much more severe than ever before. “Basically, designers need to introduce 40-60 dB of additional isolation in the Wi-Fi front end to ensure excellent Wi-Fi 7 performance. And of course filters play a critical role in this,” Jeremy Foland says. Bulk Acoustic Wave (BAW) filters offer the right quality (Q) factor to deliver exactly this, he says.
Qorvo says its BAW filters incorporate all the right RF characteristics: Low insertion loss, steep skirts, high rejection levels, and small size. That means they are ideal for any tri-band Wi-Fi infrastructure product including home gateways and mesh units, as well as enterprise-grade APs. All of the key characteristics of BAW filters are needed to make sure the highest Wi-Fi 7 tri-band performance is achieved by the corresponding AP products, Qorvo says.
“Ironically, it’s all the most important Wi-Fi 7 features that need BAW filtering in order to be workable. These include 320 MHz channels, higher order modulation, and not least MLO, which will often use 5 GHz and 6 GHz channels at the same time. Add to this that BAW filtering is an effective solution for complying with regulatory requirements in the 2.4 GHz band, such as limits on out-of-band emissions, as specified for example by the FCC,” Jeremy Foland says.
BAW filters operate by converting electrical energy into acoustic or mechanical energy on a piezoelectric material. Qorvo has shipped more than 24 billion BAW filters worldwide.
/Claus.
