Ultra-wideband transceiver combines precision with low power consumption

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Imec has used this year’s VLSI Technology Symposium to present an IEEE 802.15.4z compliant impulse radio (IR) ultra-wideband (UWB) transceiver for high-precision ranging.

The transceiver chip, building on a cost-efficient silicon implementation, can accomplish 1.4mm ranging precision and comes with record low power consumption. According to imec, it paves the way for a variety of innovative (automotive) applications. One use case includes the creation of UWB radar-on-chip systems for in-cabin (child) presence detection, and driver monitoring.

IR-UWB technology is an enabler of multiple automotive, smart industry, smart home, and IoT use cases and comes with the ability to locate assets in warehouses, hospitals, and factories with cm precision – and can help people navigate large spaces, like airports and shopping malls.

One of IR-UWB’s main differentiators is that it largely outperforms narrowband technologies (such as Bluetooth) in terms of ranging precision. However, on the downside, it uses more complex and expensive circuits and typically exhibits higher power dissipation.

Imec’s UWB transceiver chip looks to combine best-ranging precision with low power consumption.

“With the presentation of our UWB transceiver chip, imec overcomes yet another hurdle to UWB’s widespread adoption. Building on a cost-efficient silicon layout, the transceiver achieves the best-ranging precision with the lowest power consumption among state-of-the-art IEEE 802.15.4z radios,” said Christian Bachmann, programme director of wireless sensing at imec.

Fabricated in 28nm CMOS technology and occupying a silicon area of 1.33mm², imec’s 6 to 9GHz IEEE 802.15.4z compliant IR-UWB 3Rx-1Tx transceiver comes with a ranging precision down to 1.4mm. It does this, but not at the expense of a larger power budget – as the transceiver chip merely consumes 8.7mW/21mW in continuous Tx/Rx mode. It also meets UWB’s tight international spectral emission regulations with sufficient margin.

The chip’s record low power consumption results from a highly optimised, low-power and interference-resilient Rx architecture, coupled with a new digital polar transmitter architecture.

A distributed, two-stage all-digital PLL allows for further reduction of the chip’s power consumption and contributes to a reduced measurement time for localisation. To improve its ranging performance (while complying with spectrum regulations), the system makes use of an analogue finite impulse response (FIR)-based Tx pre-emphasis approach for more advanced, flexible pulse shaping.

Commenting Bachmann said, “Imec’s recent achievements include the development of the world's first sub-5mW UWB transmitter chip for the IEEE 802.15.4z standard in 2021 and the unveiling of a UWB radio capable of supporting data rates of up to 1.66Gb/s (for high data rate, low-power applications) in 2022.

“We believe this chip could ultimately support a whole new generation of UWB use cases, combining UWB ranging, communications and radar functionality. It is a technology that could find its way into automotive applications such as in-cabin presence detection, and driver monitoring – both of which stand or fall with the measurement accuracy and energy efficiency of the underlying technology,” he added.