Design of a system for cm-range wireless communication

176 Pages·2009·18.91 MB·English

Design of a system for cm-range
wireless communication
Simone Gambini
Jan M. Rabaey
Elad Alon
Electrical Engineering and Computer Sciences
University of California at Berkeley
Technical Report No. UCB/EECS-2009-184
http://www.eecs.berkeley.edu/Pubs/TechRpts/2009/EECS-2009-184.html
December 18, 2009
Copyright © 2009, by the author(s).
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Design of a system for cm-range wireless communications
by
Simone Gambini
A dissertation submitted in partial satisfaction
of the requirements for the degree of
Doctor of Philosophy
in
Electrical Engineeing and Computer Sciences
in the
GRADUATE DIVISION
of the
UNIVERSITY OF CALIFORNIA, BERKELEY
Committee in charge:
Professor Jan Rabey, Chair
Professor Elad Alon
Professor Paul K. Wright
Fall 2009
The dissertation of Simone Gambini is approved.
Chair Date
Date
Date
University of California, Berkeley
Fall 2009
Design of a system for cm-range wireless communications
Copyright (cid:13)c 2009
by
Simone Gambini
Abstract
Design of a system for cm-range wireless communications
by
Simone Gambini
Doctor of Philosophy in Electrical Engineeing and Computer Sciences
University of California, Berkeley
Professor Jan Rabey, Chair
The continuous growth in the number of mobile phone subscribers, which exceeded 3 billions
by 2007 , and of the number of wireless devices and systems, led to visions of a near future
in which wireless technology is so ubiquitous that 1000 Radios per person will exist. In this
context, ad-hoc area networks between several consumer electronic devices located within a
meter of each other will be necessary in order to reduce traffic towards the base station and
reduce power consumption and interference generation. As existing air interfaces still both
radiate and dissipate an order of magnitude higher power than what this future scenario
requires, a new, low-power radio technology must be developed. In this thesis, we develop
a low-power transceiver with range of a few centimeters targeted to mobile-mobile data ex-
change. The same transceiver could also be employed in some implanted applications, as
well as in distributed industrial control environments.
The design of the air-interface for this cm-range communication system at the propagation,
system and circuit levels. First, we describe an optimization methodology that enables the
designer to choose, for any given antenna design, which carrier frequency results in the
maximum receiver Signal-To-Noise-Ratio (SNR). We then show how by using impulse-radio
signaling, the chosen high-SNR channel can be leveraged to simplify the radio receiver archi-
tecture to the simplest possible RF receiver-consisting only of an RF rectifier. To mitigate
the known issues of sensitivity to interference for these rectifier-based receivers, a technique
to improve selectivity that uses only baseband processing and requires no RF prefilter is
introduced.
These techniques are demostrated by a transceiver test chip, implemented in a 65nm
CMOS process . The transceiver dissipates 250µW in receive mode, and 25µW in
transmit mode when operating at 1Mbps , and it integrates a timing-recovery loop
that achieves jitter lower than 2nS while consuming 45µW.This figures correspond to
1
an energy per bit of 300pJ, which compares favorably with current state-of-the art.
Professor Jan Rabey
Dissertation Committee Chair
2
To my mother Silvia, my brother Francesco and my father Diego.
If I have seen a little further it is by standing on the shoulders of Giants
I.Newton
i
Contents
List of Figures vi
List of Tables xii
Acknowledgements xiii
1 1000 Radios per Person And the Case for Ad-Hoc Networking 1
1.1 Short range wireless systems today . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1 Commercially available, low-power short range bi-directional commu-
nication devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.2 Bi-directional,narrowband short range radios resulting from academic
papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.3 Impulse Ultra-wideband radios resulting from academic papers . . . . 6
1.1.4 Other short-range, low energy communication systems . . . . . . . . 7
1.2 Thesis structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Link Margin Modeling for cm-range radios 9
2.1 Improving path loss modeling . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.1 Electromagnetic wave propagation at short range . . . . . . . . . . . 10
2.1.2 Magnetic Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.3 Model Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.4 Comparison with power transfer . . . . . . . . . . . . . . . . . . . . 23
2.1.5 Chosen design point and channel measurements with cm-scale antennas 24
2.1.6 Channel impulse response . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2 Antenna Design for a 3-10GHz wideband system . . . . . . . . . . . . . . . . 25
2.2.1 Slotted Bowtie Antenna Design . . . . . . . . . . . . . . . . . . . . . 27
ii
2.2.2 Monopole antenna design . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3 Low Power RF System Design for a cm-range Transceiver 34
3.1 Radio Dynamic Range-Power Tradeoff . . . . . . . . . . . . . . . . . . . . . 34
3.1.1 Overhead power components . . . . . . . . . . . . . . . . . . . . . . . 36
3.1.2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2 Effect of duty-cycling on power dissipation . . . . . . . . . . . . . . . . . . . 39
3.2.1 Overhead Costs in duty-cycled systems . . . . . . . . . . . . . . . . . 41
3.2.2 Duty cycling optimization . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2.3 Inherent Asymmetry of duty-cycled systems . . . . . . . . . . . . . . 44
3.2.4 Power consumption of VCO and baseband: a more critical look . . . 44
3.3 Radio Architecture Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3.1 Technological Constraints . . . . . . . . . . . . . . . . . . . . . . . . 46
3.3.2 Transmitter section and link budget . . . . . . . . . . . . . . . . . . . 46
3.3.3 Receiver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4 Baseband and Timer Subsystem Design 53
4.1 Baseband architectures for UWB systems . . . . . . . . . . . . . . . . . . . . 53
4.2 Improving Interferer Performance in Self-Mixing Radios . . . . . . . . . . . . 55
4.3 Synchronizer and modulation scheme design . . . . . . . . . . . . . . . . . . 66
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5 Circuit Design 78
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.2 Transmitter Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2.1 Architecture selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.2.2 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.3 Divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.2.4 PSK Modulator and Driver . . . . . . . . . . . . . . . . . . . . . . . 85
5.3 Receiver Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.3.1 Matching network/duplexer . . . . . . . . . . . . . . . . . . . . . . . 88
iii