Meet IEEE 802.11ad: The 60 GHz Microwave WiFi Standard

WiFi is among the most successful wireless standards alongside Bluetooth, and it is now integrated into a huge range of devices we use every day. Most WiFi users are familiar with the two standard bands: the 2.4 GHz, and the much faster 5-6 GHz band. WiFi products and specifications have undergone several iterations since the IEEE 802.11 family of standards was first introduced. Some of the newest semiconductor products available on the market are following the 7th generation of the WiFi standard and are providing among the fastest speeds for commercial products in the 6 GHz band.

There is another WiFi standard that supercharges data transfer rates at much higher frequencies. This is the IEEE 802.11ad standard, also known as WiGig, operates at 60 GHz with multiple data streams to end users with gigabit data transfer rates. Think of this as an extension of 5G into WLANs, bringing with it all the same design challenges in terms of PCB design, packaging, and physical layout. In this article, we’ll examine the technical specifications in the standard and some methods used to design PCBs operating at these frequencies.

What’s in the IEEE 802.11ad Standard

The WiGig standard was the first foray of WiFi into mmWave operating frequencies and was intended to operate alongside lower frequency WiFi generations. The tri-band nature of these devices provides the well-known long-range wireless connections that are familiar in earlier WiFi implementations, as well as a much faster short-range protocol operating in the 60 GHz band. The operating specifications for the 60 GHz band can be found in the table below.

The low range of WiGig-capable products at 60 GHz makes them most useful in a home or office environment to provide high data transfer rates directly to users. WiGig products are intended to be interoperable with products that only support earlier generations of WiFi to provide maximum flexibility for end users. The tri-band nature of these systems creates several PCB design challenges for WiGig-enabled products.

PCB Design for WiGig

Today, there are chipsets available that will support operation at the tri-band WiGig standard. These chipsets are operating at three disparate bands with huge spacing (2.4 GHz, 5-6 GHz, and 60 GHz), making interconnect design a major challenge. Layout and routing combines the major guidelines for high-speed interfaces operating at multiple Gbps (Ethernet or PCIe) and high-frequency interconnects for RF systems:

• Route the 60 GHz signal over low-loss laminates without layer changes as a grounded coplanar waveguide. This structure will need to have small width in order to have high enough bandwidth for a 60 GHz signal.
• Try to orient digital interfaces away from the RF interfaces so that there is no crosstalk into the broadcast signals. Consider routing digital sections as striplines or on the back layer.
• Place antennas near the edge of the board away from the main digital interfaces.
• Consider a hybrid RF stackup with standard FR4 and low-loss PTFE materials to reduce manufacturing costs.

Use this style of coplanar waveguide to route the 60 GHz signal in WiGig designs.

Tri-band antenna design and layout is not for the faint of heart and requires simulations to validate performance over a broad frequency range. An easier route is to operate with two possible antennas, a dual-band antenna at 2.4/5-6 GHz and a single-band antenna operating at 60 GHz. This option makes feedline design for these antennas much easier as the lower GHz section can be much wider

IEEE 802.11ay: An Improvement on WiGig

The next level up on 802.11ad is the 802.11ay standard, which is an extension of WiGig into higher bandwidth and stream count. 802.11ay quadruples the bandwidth provided in 802.11ad, specifies range of up to 500 m, and provides MU-MIMO (up to 8 streams) with spatial multiplexing. It preserves similar features as found in the 802.11ad standard but with much higher possible data rates through the multiple spatial streams and higher bandwidth/frequency. The IEEE 802.11ay standard was originally published on July 28, 2021.

Recent demonstrations of the standard have shown its potential for use in data-intensive applications like virtual reality, which was examined in an NIST study. Beamforming is another important part of the 802.11ay standard as this is required for MU-MIMO at high data rates and high frequencies. These studies can be viewed at the following links:

• Kim, M., et al. "Efficient MU-MIMO beamforming protocol for IEEE 802.11 ay WLANs." IEEE Communications Letters 23, no. 1 (2018): 144-147.
• Zhang, J., et al. "Multi-user MIMO enabled virtual reality in IEEE 802.11 ay WLAN." In 2022 IEEE Wireless Communications and Networking Conference (WCNC), pp. 2595-2600. IEEE, 2022.

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