Monolithic Wireless Transceiver Design Filip Maksimovic Kristofer Pister, Ed. Ali Niknejad, Ed. Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB/EECS-2020-33 http://www2.eecs.berkeley.edu/Pubs/TechRpts/2020/EECS-2020-33.html May 1, 2020 Copyright © 2020, by the author(s). All rights reserved. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. Monolithic Wireless Transceiver Design by Filip Maksimovic A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Engineering - Electrical Engineering and Computer Science in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Kristofer S.J. Pister, Chair Professor Ali M. Niknejad Professor Stephen D. Glaser Fall 2018 The dissertation of Filip Maksimovic, titled Monolithic Wireless Transceiver Design, is ap- proved: Chair Date Date Date University of California, Berkeley Monolithic Wireless Transceiver Design Copyright 2018 by Filip Maksimovic 1 Abstract Monolithic Wireless Transceiver Design by Filip Maksimovic Doctor of Philosophy in Engineering - Electrical Engineering and Computer Science University of California, Berkeley Professor Kristofer S.J. Pister, Chair Recently, there has been an increasing push to make everything wireless. In contrast to high-performance cellular communication, where the demand for enormous quantities of data is skyrocketing, these small wireless sensor and actuator nodes require low power, low cost, and a high degree of system integration. A typical CMOS system-on-chip requires a number of off-chip components for proper operation, namely, a crystal oscillator to act as an accurate frequency reference, and an antenna. The primary goal of this thesis is to address the hurdles associated with operating without these components at as low a power level as possible. This is a step towards the ubiquitous presence of wireless communication. In this work, an evaluation of transceiver performance is performed with power, perfor- mance, and physical size in mind. Operation of a low-power standards compatible 2.4 GHz transmitter (TX) is demonstrated without the use of an off-chip frequency reference. These 2.4 GHz transceivers (TRX), called the single chip motes, operate at low power levels with- out an off-chip frequency reference. The first single chip mote demonstrated RF chip-to-chip communication in the presence of local oscillator drift caused by temperature variation. It used a free-running LC tank oscillator that was calibrated against drift with periodic net- work traffic. The next single chip mote was a 2.4 GHz, 802.15.4 TRX, BLE advertising TX system-on-chip with integrated digital baseband and a Cortex M0. Once again, the chip uses no off-chip frequency reference. Finally, a design of high frequency transceiver with integrated antenna is presented, paving the way for a fully on-chip solution. i To no one in particular ii Contents Contents ii List of Figures v List of Tables x 1 Introduction 1 1.1 Wireless Communication in the 21st Century . 1 1.2 Radio Miniaturization . 2 1.3 Wireless Standards . 3 Bluetooth Low Energy . 4 802.15.4, OpenWSN . 5 WiFi........................................ 6 1.4 A Typical Mote . 6 Timing and Frequency Specificity . 7 Power ....................................... 8 Antenna . 8 1.5 Thesis Organization . 9 2 On-chip Frequency Synthesis 11 2.1 Receiver and Transmitter Architectures . 11 Resonant Oscillator Basics . 11 Phase Noise . 13 2.2 Passive Design . 14 Inductors . 14 Capacitive Tuning . 16 2.3 LC Tank Oscillator Topologies . 16 Topology Overview . 18 Tuning Resolution . 21 Phase Noise . 23 Supply Noise . 26 Implications for LDO design . 29 iii 2.4 IQ Synthesis . 31 Integer Dividers . 33 A Brief Comment on PLLs and FLLs . 34 3 Transmitters 36 3.1 Matching Networks . 37 3.2 Power Amplifier Topologies . 38 Class A, B, and C . 38 Class D and E . 39 3.3 Switching Transients . 41 4 The Single Chip Mote v1 44 4.1 Chip Overview . 44 Local Oscillator Design and Measurements . 46 Temperature Compensation . 48 Test Setup . 51 4.2 The Single Chip Mote v2 . 51 5 The Single Chip Mote v3 56 5.1 Chip Overview . 56 5.2 Supply Conditioning and Bias Generation . 58 Bias generation . 59 LDO design . 64 5.3 Local Oscillator . 65 Tuning and Modulation Tone Spacing . 68 Polyphase Filter . 70 Phase Noise . 71 5.4 Power Amplifier and RF Modulation . 72 Matching Network . 72 Power Amplifier . 74 Efficiency . 74 5.5 Divider . 77 Tunable Dynamic Pre-Scaler . 80 5.6 Local Oscillator Calibration . 82 Tuning . 82 Monotonic Tuning Characteristic . 83 Process, Voltage, and Temperature . 85 Two-point Calibration . 85 Temperature Calibration . 86 Calibration in an 802.15.4 Network . 87 5.7 System Demonstrations . 91 Bluetooth Low Energy . 91 iv Antenna considerations . 92 6 Monolithic Transceiver Integration 96 6.1 Selection of Carrier Frequency . 96 6.2 Antenna Design . 101 6.3 Transceiver Design . 102 System Architecture . 102 Transmitter . 103 Receiver . 104 RX-TX co-integration . 105 6.4 Measured Results . 106 7 Conclusions and Future Work 109 7.1 Conclusions . 109 7.2 Future Work . 109 Switching Supply Regulation . 109 Low-Latency Wireless . 110 Duty-cycled PLL . 110 7.3 Parting Words . 111 Bibliography 113 A SCM v3 Documentation 122 A.1 Chip diagrams . 122 A.2 Programming Procedure . 124 A.3 Scan Chain . 125 A.4 Cortex Code . 127 A.5 Common Configurations . 128 Receive Mode (RF only) . 128 Transmit Mode - 802.15.4 . 129 Transmit Mode - BLE . 129 v List of Figures 1.1 An illustration demonstrating various communication modalities for wireless sen- sor deployments . 2 1.2 The OpenWSN stack [15]. As long as the wireless transceiver adheres to the requirements set by the 802.15.4e standard, and as long as on-chip digital hard- ware is capable of running the MAC and protocol layer packet assembly (TX) and disassembly (RX) and the scheduling, the device can operate in an internet- connected wireless sensor network . 4 1.3 Board-level implementations of wireless communication nodes. Left is [22] a typ- ical commercial wireless node. Right is [23] the smallest wireless node in research 7 2.1 Block diagram of Armstrong's super-heterodyne receiver (a) a direct modulation and upconversion transmitter (b) . 12 2.2 Simple circuit of a LC tank oscillator. The R represents the total series loss of the magnetic component. Capacitive losses are not shown because capacitor loss is significantly lower than inductor loss with on-chip components at frequencies below 10~ GHz (this number is anecdotal and process dependent).