Modern WiFi technology is almost exclusively dual-band, that is to say operates concurrently over the 2.4 and 5 GHz frequency bands. This technology has come about in recent years through advancements in multi-radio access points, SDR, and the introduction of 802.11ax “Wi-Fi 6”.
Consequently antenna technology has had to adapt quickly. The first access points had separate ports for 2.4 and 5 GHz, meaning antennas could remain as single-band dipoles, however these days internal diplexers are used to operate both bands over all ports – a necessary move with the advancement to 4×4 and 8×8 MIMO. This means that just about all WiFi antennas are now dual band.
Good quality dual band WiFi antennas have been carefully developed to produce high efficiency at the two disjoint frequency bands. Ultra-wideband antennas are capable of covering both bands but do so by sacrificing radiated efficiency, but can be a convenient solution for non-critical applications.
When designing high performance wireless networks attention should be paid to the azimuth and elevation patterns of dual-band antennas to make sure the antenna will produce the required coverage pattern on each band.