tecniche avanzate di co-simulazione nonlinearenonlineare
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Tecniche avanzate di Tecniche avanzate di coco simulazionesimulazioneTecniche avanzate di Tecniche avanzate di coco--simulazionesimulazionenonlinearenonlineare--elettromagneticaelettromagnetica di sistemi di sistemi MIMO e sistemi per il riuso di energia MIMO e sistemi per il riuso di energia MIMO e sistemi per il riuso di energia MIMO e sistemi per il riuso di energia
a radiofrequenza.a radiofrequenza.
Dottorando Francesco DonzelliDottorando Francesco Donzelli
Tutor: Chiar.mo Prof. Ing. Vittorio RizzoliTutor: Chiar.mo Prof. Ing. Vittorio RizzoliProf. Ing. Alessandra CostanzoProf. Ing. Alessandra Costanzo
DEIS
U i i à di B lU i i à di B lUniversità di BolognaUniversità di Bologna
MOTIVATION
Even the most simple link Even the most simple link should be characterized more should be characterized more
The world of The world of Telecommunications is Telecommunications is should be characterized more should be characterized more
and more accurately!and more accurately!growing in complexity growing in complexity as well as sizeas well as size
Electromagnetic couplings among components on an IC or between often not taken
into account!antenna array elements, impedance mismatches, port reflections…
into account!
Nonlinear/EM co-simulation: generalitiesA general view – N Tx – N Rx case
The aim is to include all these features into a system-level approach, by means f d h l l l d f l l l d
Multiple Transmitters Multiple Receivers
of a in-depth circuit-level simulation and a final results validation
I1
NLO
TX
TX
1RX
RX
1
2
Ir
NLOS or
TX
TXTX
2
34
RX
RX
3
2
INR
LOS channelTX 5
4 RX
RX
4
5RX5
Realistic channel description
Nonlinear circuit techniques
descr pt on +
Broadband EM analysis of the antenna array
Nonlinear circuit techniques
I. Nonlinear simulation
Device portsDevice ports••The whole frontThe whole front--end can be divided end can be divided into a linea and a nonlinear into a linea and a nonlinear Device portsDevice portssubnetworks, internally connected by a subnetworks, internally connected by a discrete number of device portsdiscrete number of device ports
••External ports are responsible for External ports are responsible for
Nonlinear Nonlinear subnetworksubnetwork
External ports are responsible for External ports are responsible for external excitations, device external excitations, device polarizations and loadspolarizations and loads••The entire system can be solved by The entire system can be solved by subnetworksubnetwork
vD1ID1 IDN vDN
The entire system can be solved by The entire system can be solved by applying the kirchoff current law (in applying the kirchoff current law (in ωω--domain) domain) at each common device at each common device port The dependent variables can be port The dependent variables can be Linear Linear
subnetworksubnetwork
port. The dependent variables can be port. The dependent variables can be found into a discrete number of state found into a discrete number of state variables.variables.
vE1IE1
IEN vE2External portsExternal portsE(X) = 0E(X) = 0E(X) = 0E(X) = 0F l l F l l F l l F l l Final solving systemFinal solving systemFinal solving systemFinal solving system
Time saving techniquesE(X) E(Xn) + J(Xn) (X – Xn)E(X) E(Xn) + J(Xn) (X – Xn)
X X X X
XXi nn--th approximation of X,th approximation of X,ssnn solution updatesolution update
Xn+1 = Xn + snXn+1 = Xn + snJ(XJ(Xn) jacobian matrix for E(X) jacobian matrix for E(Xi)
Exact NewtonExact Newton--Raphson iteration (HB)Raphson iteration (HB)
sn = - [J(Xn)]-1 E(Xn) sn = - [J(Xn)]-1 E(Xn)
r = E(X ) + J(X ) s ≤ f E(X )r = E(X ) + J(X ) s ≤ f E(X )rrn = n= n--th residual th residual ff f in t m f in t m
Inexact NewtonInexact Newton--Raphson iteration (INHB)Raphson iteration (INHB)
Final solution found by means of Krylov subspaces Final solution found by means of Krylov subspaces remarkable improvement in terms of overall timeremarkable improvement in terms of overall time
rn= E(Xn) + J(Xn) sn ≤ fn E(Xn)rn= E(Xn) + J(Xn) sn ≤ fn E(Xn) ffn = forcing term= forcing term(0 ≤ f(0 ≤ fn < 1)< 1)
Modulated HB Modulated HB –– stationary states periodic seriesstationary states periodic series
t)(jΩt)(Vv(t) kk
k exp~ VVkk(t) = complex time(t) = complex time--varying envelope varying envelope ΩΩkk = k= k--th IM productth IM product
The “embedded” radiation pattern of the pt-th array element
With the assumption of free space propagation With the assumption of free-space propagation, the total radiated field associated with the t-th array
element in the presence of the other ones at ωRF is:
(t)sT,RF
(t)TφRF
(t)TθRF
(t)T );(Aφ);(Aθ
r)jβexp();(E Vωωrω ,,,r, ˆˆ
r
Due to linearity )(Aθ RFωφ;θ,
The radiated field is a linear functional of the complex phasors
of the voltages excitations (t)sTV(1 x NT) complex
)(Aφ RFωφ;θ,
of the voltages excitations sT,Vprow matrices
the j-th entries of the A’s matrices (1 ≤ t ≤ NT) are found by f i EM l i ith ll t t h t performing an EM analysis with all antenna ports short
circuited except for the t-th one that is excited by a unit voltage source.
Channel description by a t i hray tracing approach
NARROWBAND ARRAY: unique multipath pattern for a given q p p genvironment and TX-RX phase center positions
RFDDDt)(q,
T ω;φ,θ,rE RFAAAr ω;φ,θ,rE ),( tq
h θD
RFDDDT ;φ,,
θA
RXTX
q-th ray
Nq scattering
φD φ
RXTX Points
r
qdj
RFDDDt)(q,
TqN
ql
11
t)(q,RFAA
t)(q,r eω;φ,θ,rEAs,..,s,..,sΓ)ω;φ,θ(r,E
φD φA
N
Effects of ray interactionsSpreading factor, s =length of the -th of the q-th path
Phase shift at the r-th receiving element
q p
Excitation of the receiving array associated with the q-th raywith the q th ray
q-th ray incident I. Antenna in receiving modeScattering q th ray nc nt
from the t-th transmitter
receiving modeθA
Scattering Point
)( ω;φθrt)(q,E
R di i f h R di i f h φA
)( RFAA ω;φ,θr,rE
θA’
II. Antenna in transmitting mode
Radiation pattern of the r-th receiving element
ω;'φ'θrE
Radiation pattern of the r-th receiving element
ω;'φ'θrE
By the Reciprocity
A RFAA ω;φ,θRNE RFAA ω;φ,θRNE
2
y p yTheorem:
r-th
φA’
RRFAARF'
A'
At)(q,
sr, Nr1ω;φ,θr,ω;φ,θJ )()(2 t)(q,r
rRNrr EEY
jelement
excitation
Computation of the Channel transfer t imatrix
RXNR NRSuperposition of the
RX1
RXI1
NRAD NNORADray contributions
RXrNonlinear
subnetworkIr
Y ( )AR T
tRAYN
1t
N
1q
t)(q,sr,sr, JJ
RXr subnetwork
IN
1t 1q
• r-th connection port• Nt
RAY : n° of raysN ° f t itt
sR,sR,RFARsR, JVYI ωRXNR
INR• NT : n° of transmitters
sTRFsR VωHJ computation of the
(NR x NT) sT,RFsR, VωHJ(NR x NT) channel transfer matrix
T-domain simulation: a validation procedure
SolutionSolution: : piecewise linear piecewise linear
•Problem:HB and MHB techniques only deal with circuits and systems in piecewise linear piecewise linear
approximationapproximationcircuits and systems in stationary regime condition
NO INFORMATION
I1(t)V (t)
Y(ω) (EM simulation)•Need for a transient analysis
ABOUT TRANSITORY STATES!
V1(t) (EM simulation)Need for a transient analysis validationExtremely challenging for
highly dispersive linear
Unit ramp responses generated by n-port
highly dispersive linear microwave components (filters,
antennas, etc,)
0N N n
ttRtVtVtVYtI
networkRegime state
,01 1 2
11 pnijj j p
pjpjjijni ttRtVtVtVYtI
Convolution process implemented by a module described in SpectreHdl or Verilog-A language (Cadence Systems)
Y(ω) (EM simulation) Behavioural cellview(EM simulation)
A HB l i b lid t d d mpl t d!Any HB analysis can be validated and completed!
E.g. Rectenna transient response -i id l it ti t 2 45GHsinusoidal excitation at 2.45GHz
300
Cadence AWR
-100
0
100
200
Cur
rent
(μA
)
-300
-200
0 0.2 0.4 0.6 0.8 1
Time (ns)
C
Time (ns)
I. 2x2 MIMO link: Near-field couplings…
d 2x2 MIMO link fRF = 2.437 GHz (WLAN band) dfRF 2.437 GHz (WLAN band) Half-wave dipoles Variable d for transmitting
Remarkable pattern deformation due to
antennas
6
8 [V/m]60
90120
deformation due to mutual couplings
5 0
single dipole d=λ/8 d=λ/2d=λ d=4λ
2
4
6
30150
-10-50
(dB
)
-30-20-10
(dB
)
single dipoleand d 4
180 0
25-20-1510
S11
70-60-50-40
S21
d /8d /2d
210
240270
300
330-252.2 2.3 2.4 2.5
Frequency (GHz)
-70
…and influence on transmitter performancesInteractions between transmitting antenna array and nonlinear front end
Strong influence on the gain compression curveg p
single dipole and d=4λ d=λ/8 d=λ/2 d=λ
1 2
1.6
ensi
ty
g p
2
*TT EE MIMO front ends
0.8
1.2po
wer
de
mW
/m2 )
2must always be analysed under the
mpti n f
0.0
0.4
Far-
field
(massumption of
realistic EM behavior
-30 -25 -20 -15 -10
IF power (dBm)
Fbehavior
Optimal antenna spacing: I
NLOS channel (60m) AWGN link analysis with enhanced number of symbols by AWGN link analysis with enhanced number of symbols by
ANN model 1.600000 total samples PIN = -27dBm
1.E-01
1.E+00750,000 bit Optimal
distance:
1 E 04
1.E-03
1.E-02
BE
R
distance: λ/4
1.E-06
1.E-05
1.E-04
0 0.5 1 1.5 2Distanza fra le antenne (in frazioni di λ)
Optimal antenna spacing: IIChannel transfer matrix
Distance between receiving Variable dipole spacing
gantennas = λ /2 (fixed)
Scenario: NLOS (more than 3000 rays)
d=λ/4 d=λOptimal
4.E-06 |H | |H | |H | |H |11 21 12 22 4.E-06 |H | |H | |H | |H |11 21 12 22
2.E-06
3.E-06
2.E-06
3.E-06
0 E+00
1.E-06
0 E+00
1.E-06
0.E+00-1.28 -0.64 0.00 0.64 1.28
Frequency offset (MHz)
0.E+00-1.28 -0.64 0.00 0.64 1.28
Frequency offset (MHz)
Optimal antenna spacing: III
NLOS i i SISO
Input vs Output Power Spectrum Modulation format: 16-QAM
NLOS scenario in SISO case – starting point
Q Signal bit rate = 1.25Mb/sec Envelope oriented Harmonic
Balance TechniqueBalance Technique Equal Gain Combining Technique
-20
0
pect
rum
Input
Output
Remarkable Asimmetrical
-60
-40
d po
wer
sp(d
B) Spectral
Regrowth
-100
-80
Nor
mal
ized
g
-2.5 -1.5 -0.5 0.5 1.5 2.5Frequency offset (MHz)
N
SISO-20
0
ectr
um
Input
OutputBy varying the
-60
-40
zed
pow
er sp
(dB
)
pBy varying the antenna spacing d: MIMO
Worst case…
d=λ -100
-80
-2.5 -1.5 -0.5 0.5 1.5 2.5F ff t (MH )
Nor
mal
iz
-20
0
er sp
ectr
um
Input
Output
Frequency offset (MHz)
-80
-60
-40
mal
ized
pow
e(d
B)
0m
d=λ/4
-100-2.5 -1.5 -0.5 0.5 1.5 2.5
Frequency offset (MHz)
Nor
m
-40
-20
0
wer
spec
trum
B)
Input
Output
100
-80
-60
rmal
ized
pow
(dB
MIMOoptimal case
-100-2.5 -1.5 -0.5 0.5 1.5 2.5
Frequency offset (MHz)
Nor
p
II. RF ENERGY HARVESTING
Growing integration of electronics into human lives and environmentsand environments Paradigm of pervasivity
Micro-/Nano-electronics Micro /Nano electronicsallow for ultra-low powerdesignsdesigns
Sustainability andenergy autonomyenergy autonomy Longer-lifes Avoid bulky batteries Avoid bulky batteries Unprecedented applications
RF harvesting from ambient source has great RF harvesting from ambient source has great potential to inpact on portable device as a whole.
Energy scavenging from common RF SourcesM l d d Many common wireless standards to
be exploited (GSM-900, GSM-1800, UMTS, 802.11,…)
How to proceed?
Rectenna conceptual scheme
CLow-barrier
2. Charge pump circuit1. Patch antenna
Cp
CpSchottky diode SMS7630-001
• full-wave mechanism• easy to realize and integrate full wave mechan sm• best trade off between
complexity and performances
easy to realize and integrate• many different project
strategies!
I prototype: 2x2 patch arrayExtremely performing antenna
Matching section
Extremely performing antenna array (Gain ~ 12 dB) designed for
UMTS uplink band (1.92÷1.98 GHz)
RectifierS11
A common watch has
BUT:• Strictly linearly polarized
radiated farfield, not suitable been switched on by a simple
phone call!
for unpredictable sources• Too large to be converted into
a wearable implementation
II prototype: coplanar rectenna arrayPout1Pout1
Pout ≈ N*Pouti1
2
NPoutN
• Designed for GSM-1800 uplink band• Individually less performing (Gain≈5dB)• Modularity principle exploitedy p p p• Good axial ratio and band• More flexible project!
Main advantage: circular polarizationcircular polarization
Tag antennaEinc RF source
zψ
EINC
ΘΦg
θz
yr
ΦEREIRR
O
xφ
y
Measurements: Pout-DC vs Pinc-RFI prototype II prototype
MEASUREMENTS (3 ELEMENTS)
160180200
ched
1.35 GHz1.36 GHz
MEASUREMENTS (2x2 PATCH ARRAY)
250300 1.73 GHz
1.74 GHz
I prototype II prototype
B t li t
6080
100120140160
out_
DC
on
mat
cL
oad
(uW
) 1.37 GHz1.38 GHz1.39 GHz1.4 GHz
100150200250
out_
DC
(uW
) 1.74 GHz1.75 GHz1.76 GHz1.77 GHz1.78 GHz
Best alignmentbetween source
and tag…
02040
0 1 2 3 4 5 6Pinc (uW/cm^2)
Po
050
10 20 30 40Pinc (uW/cm^2)
P
MEASUREMENTS (3 ELEMENTS)
160180200
ed L
oad
1.35 GHz1.36 GHz1 37 GHz
MEASUREMENTS (2x2 PATCH ARRAY)
250
300
W)
1.73 GHz1.74 GHz1 75 GH
406080
100120140160
ut_D
C o
n m
atch
e(u
W)
1.37 GHz1.38 GHz1.39 GHz1.4 GHz
50
100
150
200
Pout
_DC
(uW 1.75 GHz
1.76 GHz1.77 GHz1.78 GHz
…and worst one
02040
0 1 2 3 4 5 6Pinc (uW/cm^2)
Pou
0
50
10 20 30 40Pinc (uW/cm^2)
The second prototype shows much more versatility towards unknown sources! The second prototype shows much more versatility towards unknown sources!
III prototype: multiresonator aperture coupled antenna
A multiresonator approach is exploited:H1 = 4 mm
0 635 mm
III.
II.
I. Feed lineII. Resonant apertures
0.635 mm I.
III.Patches
• Possibility to scavenge energy from most common wireless standards (GSM900 GSM common wireless standards (GSM900, GSM 1800, 802.11)
• Circular polarization obtained along a huge bandwidthbandwidth
• Compact layout, suitable for wearable implementations
0.9 GHz
1.75 GHz
2.4 GHz
Working principle Isolated antenna
R di i Radiating antenna
Gap-coupled multiband resonator
Performances are up to the most advanced research studies, all
over the bandwidth!400
600
Vdc
[mV
] 0.9GHz
VDC vs RF over the bandwidth!
0
200
-35 -30 -25 -20 -15 -10 -5 0Pav [dBm]
VVDC vs RF Input power
single-frequency
[ ]
600
200
400
Vdc
[mV
]
2.45GHz
R. Vullers,“Energy harvesting for Autonomous Sensor systems”,
Holst center 2009
0-35 -30 -25 -20 -15 -10 -5 0
Pav [dBm]
Rectifier layer
Antenna layer
-50
dB)
numerical modelling measurements
-20-15-10
-5
urn
Loss
(d
14 cm
-30-25
0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3
Ret
u
Frequency (GHz)
600V)
200
400
600
tpu
t (m
V
Measured900-MHz i id t
0
200
0 0 4 0 8 1 2 1 6 2
DC
out Measured
Predictedincident wave
@ 1 t0 0.4 0.8 1.2 1.6 2
Incident power density (uW/cm^2)@ 1-meter
TEXTILE IMPLEMENTATION
A challenging technology conversion, which implies:
II A detailed
I. An overview of
II.A detailed investigation about
antenna performances when bent on curved I. An overview of
suitable electrotextile materials
when bent on curved surfaces with human body characteristics
Electro-textiles: generally created by incorporating created by incorporating
conductive threads into fabrics by means of weaving and knitting
FUTURE DEVELOPMENTS
• A complete t-domain MIMO link characterization pis under progress as we speak
bl T f RF i i • A wearable Tag for RF energy scavenging is about to be fabricated and tested
• The collaboration with VTT Technical Research Centre of Finland will hopefully result in an all-p yembracing integration of our CAD techniques into an MMID sensor project by the next six months.
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