This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE JOURNAL OF SOLID-STATE CIRCUITS 1 An IR-UWB IEEE 802.15.4z Compatible Coherent Asynchronous Polar Transmitter in 28-nm CMOS Gaurav Singh , Erwin Allebes , Yuming He , Evgenii Tiurin , Paul Mateman, Johan F. Dijkhuis, Member, IEEE, Gert-Jan van Schaik, Elbert Bechthum, Johan van den Heuvel, Mohieddine El Soussi, Member, IEEE, Arjan Breeschoten, Hannu Korpela, Gert-Jan Gordebeke , Member, IEEE, Sam Lemey , Member, IEEE, Christian Bachmann, Member, IEEE, and Yao-Hong Liu , Senior Member, IEEE Abstract—A low-power IEEE 802.15.4z high-rate PHY (HRP) compatible coherent transmitter is described. The proposed transmitter uses a digital polar architecture with fixed amplitude steps in the power amplifier and asynchronous time-discrete pulse shaping. The pulse-shaping unit consists of a finite-impulse response (FIR) filter using current-starved inverter-based delay taps that can be calibrated on-chip. An injection-locked ring oscillator (ILRO)-based frequency synthesis enables wideband operation from 3- to 10-GHz frequency bands. The ILRO also allows for duty-cycled coherent mode operation with 2–4-ns phase locking time and binary phase modulation is applied directly on the oscillator. The on-chip digital front end enables duty cycling (DC) of analog front-end modules with a granularity of 2 ns. Implemented in 28-nm CMOS process, this chip is measured to consume 4.9-mW power in nominal mode with IEEE 802.15.4z high pulse repetition frequency (HPRF) compatible data rate of 6.81 Mb/s compliant with major spectrum mask regulations for channels 5 and 9. With DC of the oscillator enabled in the energy-efficient mode, a power consumption of 430 μW is achieved for packets compatible with legacy pulse- position-modulated IEEE 802.15.4a standard with a data rate of 27.2 Mb/s. Index Terms— Digital transmitter, IEEE 802154a, IEEE 802154z, impulse radio, localization, polar transmitter, transver- sal filter, ultra-wideband (UWB). I. I NTRODUCTION U LTRA-WIDEBAND impulse radios have seen resurgence in popularity due to increased demand for applications requiring spatial awareness, such as secure access, indoor Manuscript received April 19, 2021; revised August 9, 2021 and September 22, 2021; accepted September 26, 2021. This article was approved by Associate Editor Nagendra Krishnapura. (Corresponding author: Gaurav Singh.) Gaurav Singh, Erwin Allebes, Yuming He, Evgenii Tiurin, Paul Mateman, Johan F. Dijkhuis, Gert-Jan van Schaik, Elbert Bechthum, Johan van den Heuvel, Mohieddine El Soussi, Arjan Breeschoten, Hannu Korpela, and Yao-Hong Liu are with IMEC Netherlands, 5656 AE Eindhoven, The Netherlands (e-mail: gaurav.singh@imec.nl). Gert-Jan Gordebeke and Sam Lemey are with the IDLab Electromagnetics Group, Department of Information Technology, Ghent University–IMEC, 9052 Ghent, Belgium (e-mail: sam.lemey@ugent.be). Christian Bachmann is with the Wireless Sensing Department, IMEC Netherlands, 5656 AE Eindhoven, The Netherlands. Color versions of one or more figures in this article are available at https://doi.org/10.1109/JSSC.2021.3116895. Digital Object Identifier 10.1109/JSSC.2021.3116895 Fig. 1. Channels defined in 802.15.4z standard with bandwidths of 500, 1100, and 1310 MHz. localization, asset tracking, augmented reality (AR)/virtual reality (VR), and gaming. Impulse-radio ultra-wideband (IR- UWB) employing time-of-flight-based ranging is a promising solution for accurate localization [1]. The recently released IR-UWB IEEE 802.15.4z standard mandates coherent mode operation for high-rate PHY (HRP) and enhances the secure ranging operation with a dedicated scrambled timestamp sequence (STS) field in the packet [2]. The use of coherent transceiver improves the link bud- get of the IR-UWB radio at the cost of additional power dissipation as low-power non-coherent architectures cannot be employed [9]. Furthermore, other low-power IR-UWB transmitter architectures presented in the literature cannot support the coherent modulation requirements of 802.15.4z standard [10], [11]. The IEEE 802.15.4z standard also pro- poses two new high pulse repetition frequency (HPRF) modes of 124.8 and 249.6 MHz with higher pulse density compared to the legacy standard. The IEEE 802.15.4a/z standards spec- ify channels from 3.5 to 10 GHz (Fig. 1). Transmission in these frequency channels is subject to regional spectral masks regulations [3]. Conventional IR-UWB transmitters use a baseband pulse- shaping filter whose output is upconverted to RF with an IQ mixer and transmitted using a linear power amplifier (PA), as shown in Fig. 2(a). The power dissipation in such transmit- ters to meet the spectrum mask requirements is high [4], [5]. This limits battery lifetime and, consequently, the applications 0018-9200 © 2021 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See https://www.ieee.org/publications/rights/index.html for more information.