Ports and De-Embedding in Sonnet and Deembed… · 29 Device Under Test TRL R C Transmission Line...

Ports and De-Embedding in

Sonnet

SRC040610

Sonnet Ports Introduction

©2010 Sonnet Software, Inc.

www.sonnetsoftware.com

3

“Ports allow us to excite a circuit or

antenna and measure the results.”

Daniel G. Swanson, Jr. and Wolfgang J.R. Hoefer

“Microwave Circuit Modeling Using Electromagnetic

Field Simulation” copyright 2003 Artech House, ISBN

1-58053-308-6, pp. 173.

Port types, port numbering, and adding and

removing ports are covered in the Sonnet

User’s Guide.

Adding ports to a Sonnet circuit structure is

one of the standard setup steps in the Sonnet

Quick Start Guide.

SRC040610

Basic Definitions

• Standard Box Wall Ports

• Standard Internal Ports

• Via Ports

• Auto-Grounded Internal (AGI) Ports

• Co-Calibrated (CC) PortsTM



4

1+-

• Each Port has Two Terminals

• Port type is determined by where the terminals are connected

SRC040610

The Port Model

• The port model is shown above with its internal impedance model

• The model is an ideal generator with a user-selectable internal impedance; we choose R=50 and leave all other elements at zero by convention

• This model affects S-parameters only; Y- and Z-parameters are termination independent

• Sonnet Netlist Projects or network simulators can provide more general normalizations and/or terminations if desired

©2010 Sonnet Software, Inc. www.sonnetsoftware.com5

V

R + jX L

C

+

-

+

-

SRC040610

Standard Box-wall Port (Edge Port)



6

Box wall provides perfect ground reference

PEC Bottom and sidewalls provide return current paths

1+-

PEC Top

PEC Bottom

SRC040610

Special Port Numbering

• Ports are numbered by default as they are created in xgeom

• Port numbers may be changed in xgeom

• The polarity of the port may be changed by using a negative port number

• Ports with identical port numbers are electrically connected

• Port numbering can provide odd-mode (push-pull) and even-mode (push-push) ports



7

SRC040610

Even Mode Ports



8

+

-

Common-mode Excitation

SRC040610

Odd Mode Ports



9

+-

Odd-mode (Differential) Excitation

Negative number ports explicitly define the return current path

for the corresponding positive number (i.e. -1 is defined to be

the return current path for port 1)

Sonnet box wall is NOT in the return current path for this CPW

circuit

SRC040610

Arbitrary Port Assignment

• Combine multiple ports for phase balance analysis



11

Multiple gate fingers fed ―common mode‖ for each separate active device

SRC040610

Sonnet De-embedding Definition



12

“De-embedding is the process by which the port

discontinuity and transmission line effects are

removed from the analysis results”

-- Sonnet User’s Guide (Chapter 7, ―De-embedding‖)

SRC040610

De-embedding Ports in em

• Calculate port discontinuities

• Remove the effects of the port discontinuities from the analysis results

• Shift reference planes (removes effects of transmission lines from analysis results) if reference planes are defined

• Calculate transmission line parameters (Zo and eeff)


Port

Metal Box Walls

Device

Under

Test

(DUT)

Transmission Line

Transmission Line

Port

SRC040610

Invoking De-embedding

• De-embedding is usually required, and is on by default in the solver

• Adding reference planes to a circuit in the Project Editor is not required; reference plane is the substrate edge unless otherwise defined

• Using a Calibration Reference Plane setting can provide time savings for analysis of the de-embedding standards

– Assumes reference plane at substrate edge

– Microstrip: Use ~4-5x substrate thicknesses

– CPW: Use ~4-5x center conductor width



15

SRC040610

De-embedding Ports in Sonnet



17

Frequency: 4 GHz

Circuit requires 1312 subsections and 16 MB of memory.

Waveguide mode time: 0.270 seconds.

Fourier transform time: 1 second.

Coupling time: 7 seconds.

Loss time: 0 seconds.

Matrix fill time: 9 seconds.

Matrix solve time: 7 seconds.

De-embed left box wall:

First de-embedding standard, left box wall: 5031 microns length, 87 subsections.

Time: 1 second.

Second de-embedding standard, left box wall: 10062 microns length, 160 subsections.

Time: 2 seconds.

De-embed right box wall:

De-embedded 50-Ohm S-Params. Mag/Ang. Touchstone Format. (S11 S21 S12 S22).

4.00000000 1.000000 150.90 6.434e-4 69.458 6.434e-4 69.458 1.000000 168.01

!< P1 F=4.0 Eeff=(6.63198943 0.0) Z0=(49.5334801 0.0) R=0.0 C=0.15935493

!< P2 F=4.0 Eeff=(6.63198943 0.0) Z0=(49.5334801 0.0) R=0.0 C=0.15935493

Total time per frequency: 23 seconds.

Analyzing entire circuit

(DUT and transmission

lines)

De-embedding

Port 1

Results

SRC040610




18

W

em uses the cross-section

at the box wall to compute

Zo and eeff

W

- Transmission Line Parameters -

SRC040610




19

Box Wall

R

C

DeviceUnderTest

S-parameters

from em without

de-embedding

Box-wall port

discontinuity

Shunt Cap for Portdiscontinuity; R usedif the line has loss

- The Port Discontinuity -

SRC040610

Double-Delay Calibration



20

CAL Standard #1

CAL Standard #2

Convert both results to chainMatrices; pre and post-multiplystandard 1 by – standard 2 to get:

Port Discontinuity

Objective: Obtain the port discontinuity represented by the capacitor for the port

SRC040610

Double-Delay Calibration Example



21

Take the cross-sectionOf what touches the boxWall and extend as thruOf length L and 2L

OriginalCircuit

L

2L

CalStd. #1

CalStd. #2

SRC040610


• Analyze a one cell long open stub

• Use symmetry if possible

• Ignore the S-parameters and use the Zo and eff data given by em


1

- The Quickest way to get Zo and eeff -

SRC040610



24 11/9/2009


-R

-C

R

C

Device

Under

Test

S-parameters from em

without de-embedding


with de-embedding

Block cascaded to negate

box-wall port discontinuity Box-wall port discontinuity

- Canceling the Port Discontinuity -

SRC040610




29

Device

Under TestTRL

R

CTransmission Line

Box-wall port discontinuity



- Extra Feed Transmission Lines -

SRC040610




30

Device

Under TestTRL

R

CTransmission Line

Box-wall port discontinuity



-TRL

-R

-C


with de-embedding

Block cascaded to

negate port

discontinuity

Block cascaded to

negate

transmission line

- Shifting Reference Planes -

SRC040610




31

2

1

N

.

.

.

Ports

Box Wall

N-coupledtransmission lines

- Coupled Transmission Lines -

SRC040610


• All coupling between lines is considered

• All coupled lines must be either horizontal or vertical

• The width of each coupled line must be constant

• The spacing between coupled lines must be constant

• Zo and eeff are not printed because of multiple modes which exist



32

SRC040610

Multiple Coupled Transmission Lines

• Zero-Length Coupled Standard

– Use any planar transmission line(s)

• Perfect Calibration: |S11|=|S31|=|S41|= 0 (-infdB)

• Anything other is ERROR

• Checks both the software cal noise floor and the ability to de-embed cross-coupling of feed lines


Test: How good is the calibration in your software?

SRC040610

Zero-Length Coupled Line



34

Sonnet Results

A well-knowncompetitor’s results

SRC040610

Avoid Non-physical De-embedding



38

Discontinuity

begins here

L1

W1

SRC040610

Non-Physical De-embedding



39

W2

W1

W1

L1

W1

SRC040610

Ungrounded Internal Ports



40

- +

• Differential port• No common ground• Port can be de-embedded, but remember

that reference is the metal on the (-) terminal• Current into (+) is equal to current out of (-)• Local ground reference for port!

1

SRC040610

Via Ports

• Access to ground only if the via goes to ground

• Ground Reference is the bottom of the via

• Versatile: Can be placed between any two layers; doesn’t have to be on the end of a polygon or transmission line

• Cannot be de-embedded (but see Auto-Grounded Internal ports)


Top Layer Bottom Layer

1

+

-

SRC040610

Auto-Grounded Internal (AGI) Ports

• AGI Ports may be connected on the end of any X- or Y-directed polygon edge inside your circuit

• Fully Calibrated to remove port discontinuity!

– Only Sonnet brings you perfectly calibrated internal ports

• Dynamic range for isolated AGI ports is reasonable (~60 dB or so) but not as good as Co-Calibrated Ports (~200 dB)

• Reference planes may be moved up the connecting line if desired


SRC040610

AGI Ports – Special Considerations

• At runtime, the software builds a via to the bottom of the Sonnet box for ground access

• Requires unobstructed downward access in your circuit (under the port) for via access to bottom of analysis box

• Via and coupling to the connected transmission line are de-embedded; reference plane on top layer

• Warning: Via may cross-couple to non-adjacent metal in the primary structure

• Multiple AGI ports that are closely spaced may exhibit coupling that cannot be de-embedded (See Co-Calibrated Ports)



43

The model actually

simulated in the software

includes a via accessing

ground for the port; this via

is calibrated out

SRC040610

Auto-Ground Port Coupling



45

Sonnet can completely de-embed the effects of each auto-grounded port extension to ground.

Sonnet is NOT able to de-embed the effects of coupling between two nearby auto-grounded ports.

SRC040610

Co-calibrated™ Internal Ports

• All ports introduce discontinuities

• De-embedding removes port discontinuities from our simulation models (and measurements!)

• Internal ports have traditionally been difficult to de-embed with high dynamic range

• New Co-Calibrated Internal Port technology introduces >100 dB of dynamic range for internal ports—an industry first

• Multiple Co-Calibrated Ports may be placed very close together and port cross-coupling is removed

• Theory is fully published



46

Co-Cal Internal Ports for

Transistor or other

component Connections

SRC040610

Co-calibrated Internal Ports



47

Multiple Perfectly Calibrated

Internal Ports make it possible

to simulate everything but the

transistor, capturing all passive

circuit cross-coupling and other

physical effects

SRC040610

Co-Calibrated Internal Ports



48De-embedding error in |S11| and cross-terms for each line lower than < -200 dB

2 4 6 8 10 12 14 16 180 20

-270

-240

-210

-180

-150

-120

-90

-60

-30

-300

0

freq, GHz

dB

(S(1

,1))

dB

(S(3

,1))

dB

(S(4

,1))

2 4 6 8 10 12 14 16 180 20

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

-1.0

1.0

freq, GHz

phase(S

(2,1

))phase(S

(4,3

))

Co-Calibrated Internal Ports

Feed lines de-embedded from result

SRC040610

Co-calibrated Ports De-embed



49

Sonnet can completely and accurately de-embed the coupling between two nearby co-calibrated ports!

Sonnet can accurately simulate the coupling between two metal traces on both sides of an embedded component by using co-calibrated ports for the component!

SRC040610

Co-Calibrated Port Groups



50

Sonnet can accurately de-embed the coupling among a group of ports situated on a rectangle.

1A

Group label

SRC040610

Nearby CC Port Groups



51

Sonnet cannot de-embed the coupling among different co-calibrated port de-embedding groups close to one another.

Group A

Group B

Ports and De-Embedding in Sonnet and Deembed… · 29 Device Under Test TRL R C Transmission Line...

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