modeling of passive elements with asitic

8/22/2019 Modeling of Passive Elements with ASITIC

1/20

Modeling of Passive

Elements with ASITICProf. Ali M. Niknejad

Berkeley Wireless Research Center

University of California, Berkeley


2/20

Outline of Presentation

ASITIC Overview

Electromagnetic Solution Approach

Partial Inductance Matrix

Eddy Current Losses

Capacitance Matrix

Experimental Validation

Broadband Modeling

Limitations and Future of ASITIC


3/20

Applications of Passives for RFICs

Narrow-band impedance matching

Tuned loads (resonant tank)

Low noise degeneration and feedback Natural/artificial transmission lines

Linear filters (high dynamic range)

Fully differential circuits Low voltage/low power design


4/20

The Goal of ASITIC

0

Solve the analysis, design, and modelingproblems

Achieve accuracyover a wide frequency range

Perform analysis of structures quicklyfor optimization Retain flexibilityto work with arbitrary structures

Create a design environment

Generate simple compact models

Technology File Layout Electrical Specs Model


5/20

ASITIC Block Diagram

Graphical

Interface

ComLine

Interface

TechFile

Processing

Parser DRCCalc EngineGeom Engine

Meshing Engine

Numerical Back-End

BLAS FFTWLAPACK QUADPACK

OpenGL

DisplayHardware

Green FunctionTable Lookup

Tech FileInput

Log Files


6/20

Planar Inductor/Transformer Layout

circular spiral inductor symmetric center-tapped

transformer

balun


7/20

3D Inductor/Transformer/Capacitors

3D structures allow more flexibility

Shunting several spirals lowers series loss

Series interconnection of spirals can enhance magneticfield and provide nearly n2 increase in inductance due totight magnetic coupling

New transformer topologies are also possible Multi-layer finger capacitor structures offer high density


8/20

High Freq. Effects Over Si Substratesegments couple magnetically

and electrically through oxide/airproximity effects

due to presence of

nearby segment

substrate injection

substrate current

by ohmic, eddy, and

displacement current

substrate tap

nearby causes

lateral currents

radiation

current crowding at edge

due to skin effect


9/20

Efficient/Accurate Method of Analysis

Electrically Short Segment

Model short metal segment as lumped RLC Circuit

Metal segments are linked capacitively and inductively

Set up node equations for complete system and solve

Method equivalent to solving Maxwells equations

Distributed Inductance

and Resistance

Substrate Loss

Reference: A. Ruehli, H. Heeb, MTT, July 92Partial Element Equivalent Circuits (PEEC)


10/20

Substrate Currents

32143421321321

conductiondisp.currentseddyradiation

)('

2

2

=

=+=

jAjA

AjjJEjA

From Maxwells equations (Coulomb Gauge):

Neglect radiation as long as

Displacement and conduction current are curl-free

Losses due to conduction currents accounted for by solving:

j+== '

'

2

Losses due to eddy currents accounted for by solving:

AjA =2


11/20

Current Constriction in Spiral Center

1 GHz 5 GHz

L=200 W=10

S = 10 N = 5

L=200 W=10 S = 1 N = 5

C

urrentDensity


12/20

Partial Inductance Matrix Calculation

Current constriction occurs at HF Current concentrates along the outerskin of a conductor

Proximityof other conductors also influence the distribution

Inner turns in a spiral have most current constriction

Example: Use S=1 spacing on and S=10 .

Normalized Inductance

0.95

0.96

0.97

0.98

0.99

1

0 1 2 3 4 5(GHz)

Lac/

Ldc

S = 10um

S = 1um

Normalized Resistance

1

1.2

1.4

1.6

1.8

0 1 2 3 4 5(GHz)

Rac/

Rdc

S = 10um

S = 1um

Ldc = 5.2 nH and 2.6 nH


13/20

Bulk Eddy Current Losses

Reference: A. M. Niknejad and R. G. Meyer, MTT, January 01

substratespacefree AAzyxA += ),,(

( )

=0

0

,

, )(cos),()(

2

~ 0dmxxmwmKm

m

ejZ

yym

SM

ji

)tanh()()(

)tanh()()()(

23

2

232

23

2

2322 0

tmm

tmmem

my

+++

=

modeling of passive elements with asitic

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