Summary of basic knowledge points of ultra-wideband technology

The 132-year-old ultra-wideband (UWB) communications technology is now enjoying a renaissance for connecting devices wirelessly over short distances. Many industry observers claim that UWB could prove more successful than Bluetooth because it is faster, cheaper, uses less power, is more secure, and offers superior location discovery and device ranging.

Companies such as Intel, Time Domain, Apple, Huawei, Samsung, Xiaomi, NXP, Sony, Bosch and Xtreme Spectrum are all researching and investing in UWB technology. In fact, Apple already offers a UWB chip in its iPhone 11, which enables superior positioning accuracy and ranging through "time of flight" measurements.

In this article, we’ll cover the basics of UWB technology, including its origins, benefits, and a high-level look at the transmission method.

What is Ultra Wideband?

Ultra-wideband (UWB) is a short-range wireless communication protocol (like Wi-Fi or Bluetooth) that uses short pulses of radio waves in the frequency range of 3.1 to 10.5 GHz in unlicensed applications.

The term UWB is used for bandwidths (BW) greater than or equal to 500 MHz or fractional bandwidths (FBW) greater than 20%, where FBW = BW/fc, where fc is the center frequency.

The history of ultra-wideband

The history of UWB technology dates back to the days of the first man-made radio, when Marconi used spark gap (short electrical pulses) transmitters for wireless communications.

In 1920, UWB signals were banned for commercial use. UWB technology was limited to defense applications under highly classified secure communication procedures. It was not until 1992 that UWB began to receive widespread attention from the scientific community.

The development of high-speed microprocessors and fast switching technology made UWB commercially available for short-range, low-cost communications. Early applications included radar systems, communications, consumer electronics, wireless personal area networks, positioning, and medical electronics. Since then, detailed knowledge of UWB electromagnetics, components, and system engineering has been developed.

The US Federal Communications Commission (FCC) was the first organization in the world to issue UWB regulations allowing unlicensed use of allocated spectrum in 2002. However, the allowed power limit was set very low to avoid interference with other technologies operating in the band, such as WiFi, Bluetooth, etc.

The low spectral density of UWB signals is attractive, which makes UWB less susceptible to in-band interference from other narrowband signals and very secure because they are difficult to detect due to their low power density.

Advantages of Ultra-Wideband Technology

The ultra-wide bandwidth of UWB signals enables better indoor performance than traditional narrowband systems.

Some of the capabilities of this bandwidth are highlighted below:

The wide bandwidth resists channel effects in dense environments and enables very fine spatiotemporal resolution for high-precision indoor positioning of UWB nodes, such as the new iPhone 11.

The low spectral density below the ambient noise ensures a low probability of signal detection and improves the security of communications.

Using UWB, high data rates can be transmitted over short distances.

UWB systems can coexist with already deployed narrowband systems.

Ultra-wideband transmission

Data transfer uses two different methods:

Ultrashort pulses in the picosecond range, covering all frequencies simultaneously (also called pulsed radio)

Subdividing the total UWB bandwidth into a set of wideband orthogonal frequency division multiplexing (OFDM) channels

The first approach is cost-effective but reduces the signal-to-noise ratio. In general, pulse radio transmission does not require the use of a carrier, which means reduced complexity compared to traditional narrowband transceivers (i.e., simpler transceiver architecture) because the signal is radiated directly through the UWB antenna. A Gaussian monocycle or one of its derivatives is an example of an easily generated UWB pulse.

The second approach uses spectrum more efficiently and provides better performance and data throughput, but at the expense of increased complexity (i.e., the need for signal processing) and power consumption.

The choice between the two methods depends on the application.