X-PARAMETERS

What is it?

Agilent Technologies

Eesof Korea

Kim, Kyoung-Won

Today many problems exist with non-linear designs

Examples:

• You apply a clean signal to the input of your device but your output (B2) is distorted. Why? How do

you fix it?

• You get good performance from a device but when you cascade it with other devices the composite

output does not perform to expectations. Is the design unstable? What is going on?

• There is high 2nd harmonic (or third harmonic) content in the output of a design and a matching

circuit is needed to remove that, but the phase of that spectral component needs to be known. S-

parameters are valid only for small signal linear systems. They do not accurately represent nonlinear

behavior. At large drive, the whole non-linear characteristics changes.

November 18, 20102

The Solution:Agilent Technologies Announces Breakthrough in X-Parameter Nonlinear Model Generation for Components Used in

Wireless, Aerospace Defense Industries.

X-Parameters Enable Accurate Non-Linear Model Generation from Simulation or Measurement, for Fast Development

Agilent Restricted

Beyond Large-Signal S-ParametersApplications of X-Parameters models in ADS

November 18, 20103

NowA new breakthrough approachCharacterize your devices using X-parameters

X-Parameter model is a real rigorous, scientifically

proven, and unprecedented approach that captures all

non-linearties, amplitude, phase at all harmonics and

with mismatches; and uses these data directly in ADS

for design, simulation, and characterization.

BeforeDesigners Struggle in the design of large

signal non-linear circuitsTraditional non-Linear device models do not

accurately represent actual non-linear device

behavior under all real conditions including large

input signals, mismatches, and higher order

harmonics.

Device model; Max Power;

Linearize; stabilize; etc.

Agilent Restricted

Power amp related customer products flow (food chain)

Power amp chips

Foundry

(Compound)

Cell phones

WiMAX

Power amp moduleBase station

Front end modules

(w/PA)

Chip set/

Reference designFoundry

(Silicon)

GaAs

GaN

CMOS

Semicon

Process

Circuit

Design

System

Design

CMOS

LDMOS

SiGe

Players in semicon & wireless communication

Samsung

Qualcom

m

PA

foundries

system HTC Nokia RIM Haier Samsung Motorola Sony-Ericsson Apple

Silicon (+LDMOS, SiGe)GaAs (+other compound)

TSMC UMC Chartered WIN UMS Cree

RFMD

Skyworks

module

Infineon

Renesas

Avago

Broadcom

Eudyn

a

Jazz

ST-

EricssonMediaTek

Toshiba TriQuint

Mitsubish

iFreescale

Fujitsu

RichWave Anadigics

chip set/

ref design

Murata EPCO

S

FMD

design

houses

IDMNEC Elec

Hittite

TaiyoYud

enZTE Huawe

iFingu

RFHIC

X-ParametersBridge Between Our Customers

November 18, 20106

Agilent Restricted

ESL

Electronic System Level

Design (ESL)

X-pars

IC Design Houses /

Component Vendor

System Integrators

New Designs

Share IP Protected

X-Parameters file

Existing PartsX-parameters

measurement

NVNA

X-Parameters

Component for ADS

Bottom-up Sim-based verification

Bottom-up meas-based verification

Top-Down Design Specs

Non-Linear

X-Parameters Ideal

Specs

1. an extension of S-parameters to non-linear devices

2. a data library with non-linear information

3. three dimensional CAD file

4. behavioral model

5. a tool for non-linear simulation

Five effective ways to describe X-parameters

linear: S-parameters

1. X-parameters are the mathematical extension of

S-parameters for non-linear devices

InOut

S

non-linear: X-parameters

In

In

OutXIn

In

Out

OutX

S

In

In

In

Real X-parameters are a little more complex, but you

can survive with this knowledge in 90% of the cases!

This fundamental drive

tone is driving the

device to non-linear

21

21

Reflection is measured the same way with the drive tone always provided

at the input

In

OutS

In

In

Out

X

In

Drive tone

Out

OutX

S

In

In

In

In

22

22

This fundamental drive tone is

driving the device to non-linear

linear: S-parameters

non-linear: X-parameters

X-parameters converges to S-parameters when the driving tone

is small

In

Out

In

In

Out

OutX

In

In

Ina1 0 0

0 a2 0

0 0 a3

There are only diagonal elements in this matrix.

These diagonal elements are equivalent to S-param.

Small enough

2. X-parameter file is like a library

-- everything is in it --

Vg, Vd, Freq,

GammaLoad,

one page

Frequency

Vg

Load impedance

Vd

Power

X-param

one sector

one book

one series

one bookshelf

one library

Measurement takes from tens of minutes

to a few hours depending on the size of the “library”

3. X-parameter is like a 3-D CAD

-- in a datasheet of an amplifier, “linear” and “non-linear” are mixed --

Non-linear parameters Linear parameters

IMD

Pout vs Pin

P1dB

PAE

S=parameters

Datasheet of an amplifier is like 2-D drawings of a 3-D object

P1dB

S-parameters

IMD

PAE

X-parameter file is like a 3-D CAD file

-- You can get IMD, S-param, P1dB and anything out of this file --

X-param file3-D file

( ) ( ) ( ) *

11 , 11 , 11( ) ( ) ( )F k S k l T k l

ik ik ik jl jl ik jl jlB X A P X A P a X A P a

4. X-parameter is a behavioral model

＝[X]

an FET is described by many elements

(>100 elements @HBT)

an FET is described by [X]

＝[X]an amplifier is described by [X]

＝

＝

an amplifier is described by providing

the internal circuits

＝

an amplifier is described by huge amount

of linear & nonlinear measurement data

before [X]

after [X]

before [X]

after [X]

before [X]

Designer

S-param file

X-param file

ADS simulator

NVNA

Compact model

5. X-parameter is a simple, easy and accurate simulation tool

drag-and-dropping the X-parameter

file to your ADS circuits and you

can immediately enjoy the accurate

non-linear simulation

THE VALUE OF

X-PARAMETERS

18

The Values of Non-Linear X-Parameters

1. IP Protection / Sharing Designs

2. Device Characterization

3. Hierarchical Designs

4. Cascade-able Components & Packaged Parts

5. Load Pull Modeling

The Value of X-ParametersIP Protection / Sharing Designs

• Integrate the real design into an early-on system design

• Decide early on whether or not it is the design they will buy or not

• Avoid un-necessary added wafer spins that cost money and delay product sales

System integrators need to

evaluate designs early for many

reasons, three of which are:Sharing IP protected designs

between design houses / component

vendors and system integrators

Problem:

Design houses are reluctant to share their real designs due to IP issues. As a result, loss of business

opportunities might occur especially if their competitors were able to share their designs with the system

integrators earlier.

Therefore, Design houses have a dilemma and the system houses are not able to design their system

effectively and on timely fashion.

Solution

X-parameters models protect the IP.

If you wish to send a design to the system integrator, then encapsulating the composite design and

modeling it in an X-parameter representation completely protects the design information, better than

encrypting.

The Value of X-ParametersIP Protection / Sharing Designs

ExamplePut something together fast using Lumped Elements; Create IP protected X-

Parameters model; Send it to System Integrator

Create an X-Parameters model and share it

immediately with the System Integrator

X-ParametersDesign IP Protection

I M N

FET 1

FET 2

Int MN

OMN

Extract X-Parameters model from Simulation

Real PA Circuit Simulation

1 Design Circuit

2 Extract model

3 IP Protected

X-Parameters

File

(see next page)

Extract X-Parameters model from SimulationX-Parameters representation of the PA

Extract X-Parameters model from SimulationResults Comparison of real circuit Vs model

Pin / Pout

Phase

X-ParametersDesign IP Protection

X Parameters in ADS

1. Insert X Parameter template which is

already setup for the extraction.

2. Connect your DUT.

3. Modify Power levels and frequencies as

needed.

4. Simulate.XP_Source

XPTerm1Num=1

XP_Loa

d

XPTerm

2Num=2

XP_Bias

XPTerm3Num=3

Amp

Amp1

X-Parameters

X_Param

XP1Freq[1]=1 GHz

Z0=50 Ohm

In ADS 2009 U1, you are able to create simulation based X-Parameters models for your circuits.

You can then share this IP-Protected model with other system integrators who can use the model in ADS

and do higher level system verification on the real virtual design.

Value of X-Parameters models in ADSDevice Characterization

Problem

Circuit-level device models

• Designers often complain about the models

they get from foundries. Many are really not

that accurate.

• It takes an expert, often a Ph.D. working full time to do an excellent job extracting a

compact device model. It also takes time.

Example: New Device level models may take years and many revisions for designers to

adopt and trust them. Even then, foundry models may have limitations that in the past have

forced designers to extract their own customized device models…

Value of X-Parameters models in ADSDevice Characterization

Problem:

Designers are not able to achieve optimum

Power and Power Added Efficiency from their

MMIC designs

due to inaccurate non-linear device models.

They end up excluding the OMN from the

design and build it off-chip, on the board

Chip without the Output Matching Network

Power / Freq Source

Probe

Station

Measure S22

1

2

3

4Design off-chip

Output Matching

Network on Board

Using S22*

Applications of X-Parameters models in ADSDevice Characterization

SolutionUse the new breakthrough approach to characterize your devices using X-parameters

• A non-Ph.D. can extract an X-Parameters model from NVNA X-parameter measurements (including

load-dependent) and get a reliable model quickly.

• New technologies, such as GaN, do not have a well-accepted reliable device model to use. It can

take many years to develop such a model. An X-Parameters model can be generated very easily just

by measuring the device with the NVNA.

“Literally in five minutes, you can generate a nonlinear X-

parameter model from an off-the-shelf amplifier by

measuring it with Agilent’s Non-Linear Vector Network

Analyzer (NVNA), and you can start doing non-linear

designs with it in ADS immediately,” said Jason Horn,

R&D engineer with Agilent’s High-Frequency Technology

Center, and one of the inventors of X-parameter

technology.

Script generates X-

parameters model

component for Design

and Simulation in

ADSNVNA Measures

X-Parameters

LTE Driver Amp using Measured X-Parameters FETDevice Characterization

X-Parameters Measurement of an

on-wafer FET device using the NVNA and

Maury Load Pull system

Specs

Gain >20 dB

S11 and S22 < -15 dB

Example

The Value of X-ParametersHierarchical Designs

Problem

System Engineers finds it cumbersome and

slow to use circuit level designs and circuit level

models in hierarchical RF-System simulation –

not practical and very slow

Also, Behavioral models do not accurately

represent the circuits non-linear behavioral in

phase and magnitude at all harmonics

The Value of X-ParametersHierarchical Designs

Solution

Much of the value for X-parameters is in hierarchical design.

One can measure OR simulate a two-stage amplifier and get a X-Parameters

model for that composite structure.

Speeds-up Simulation and trade-off analysis for system design and verification

X-Par

X-Par

X-Par

Replace the whole structure by its X-Parameters model

The Value of X-ParametersCascade able components and Packaged Parts

Problem

You are designing with packaged parts. All you have is a compact model of the circuit at some freq and

some power. You either have to get a model for the package, or use what the foundry gives you for the

part. There are uncertainty in the model.

When cascaded, the effects of the interaction between modules with higher order harmonics and

mismatch is not predictable nor understood

As a results, many problems are encountered in accuracy, delays in integration & test, and time to

market.

The Value of X-ParametersCascade able components and Packaged Parts

Solution

X-Parameters models work directly for packaged parts, including the effects of all the parasitic

and they are cascade able.

If you are designing with packaged parts, X-Parameters models generated from

measurement or simulation is the optimum solution

Simulation Vs Measurement of two cascaded

packaged amps, each of which was separately

modeled by its own measured X-Parameters.

“

”

Literally in five minutes, you can generate a nonlinear

X-parameter model from an off-the-shelf amplifier by

measuring it with Agilent’s Non-Linear Vector Network

Analyzer (NVNA), and you can start doing non-linear

designs with it in ADS immediately,” said Jason Horn,

R&D engineer with Agilent’s High-Frequency Technology

Center, and one of the inventors of X-parameter

technology.

X-Parameter models with Maury Load Pull in ADSInstant accurate Large signal X-Parameter model

Before

• Extract a load pull measurement at a specified input signal drive, bias, and frequency

• The linear simulator is then used to match to this single load pull measurement for optimum power and PAE.

• Unable to adjust and correct this extracted load impedance with mismatch cascaded effects and different drive levels and frequencies

• Phase information on the harmonics are not captured causing large in-accuracy in results

Now

• Maury Load Pull with Agilent NVNA now produces an instant accurate large signal X-Parameter model, which can be loaded easily (drag and drop) into ADS for design, simulation, and optimization.

• The model can be used in simulation for power amplifier design, including multi-stage, Doherty, or other complex circuits.

The Non-Linear

Design Puzzle is now

completedNonlinear Modeling

Nonlinear Measurements

Customer

Applications

Nonlinear

Simulation

Non-Linear X-ParametersA Breakthrough Technology for Non-Linear Design

Agilent NVNA with Maury Load Pull produces an instant large signal

model, which can be loaded easily (drag and drop) into Agilent ADS for

circuit design and simulation. This process is a breakthrough for the

industry.

Script generates

X-parameters

model component

for Design and

Simulation in ADS

Tuners that covers all regions on the Smith Chart (all Impedances)

Cable /

connectors

Load Pull TunerSource Pull Tuner

ADS

NVNA

Measures X-Parameters

The NVNA with Automated Load Pull MeasurementUsing the Maury Load Pull System

Automated Load pull has become a standard tool for characterizing devices operating in other than ideal 50 ohm environments

What is Load Pull?

– Load Pull is “Measurement Vs Impedance”

– Impedances that are located all over the Smith Chart

– Not only 50 ohms

TUNERTUNER

source Load

Stimulus and

Measurement

DUT

Tuners used to vary the

impedance seen by the Device

Under Test (DUT)

Extract X-parameters model from Simulation

“Project View” of the demo

Extract X-parameters model from SimulationDemo # 1- Second stage of two Cascaded MMIC PA’s

Extract model with Pin=

-10 dBm to 5 dBm

Gain

27 dB

Pin

0 dBmPin

-27 dBm

Pout = 26 dBm

1 dB compressed

Gain

26 dB

Operational power setting for LTE Application

Demo #1

Demo 1: Extract X-par model Set-up

Demo 1: X-par model overlaid on PA Results

Conclusions from the demos

• Demo 1 shows the creation of mdf file X-par model with:

Swept Pin, freq, and DC power

Load and source pull – not in this demo but will be available in ADS2009 U1

Extract X-parameters model from SimulationDemo # 2- Compare X-par model, P2D model, and PA

Extract X-par model and P2D model

with Pin= -40 dBm to 10 dBm

Pin

-40 to 10 dBm

Pout = 26 dBm

1 dB compressed

Gain

26 dB

Demo 2: Results

Conclusions from the demos

• Demo 1 shows the creation of mdf file X-par model with:

Swept Pin, freq, and DC power

Load and source pull – not in this demo but will be available in ADS2009 U1

• Demo 2 compares X-par, P2D, and PA with 50 ohm loads:

Only at the fundamental freq and 50 ohm load, the P2D model matches very well with the X-

parameters model and with the PA.

o This confirms our past statement on the accuracy and usefulness of the P2D model.

X-parameters model contains magnitude and phase info on all of the harmonics, where P2D

is good only at the fundamental freq.

Extract X-parameters model from SimulationDemo # 3- Cascaded PA’s and models with mismatch

Gre

at S

11

Gre

at S

11

Gre

at S

22

Po

or

S22

Small signal Large signal

Demo 3: Results

Conclusions from the demos

• Demo 3

Unlike P2D model which is good only at 50 ohm impedances, X-par model works at all

source and load impedances (available in ADS2009U1 version)

P2D models will have accuracy problems when cascading modules with source and load

mismatch

Demo # 4: Cascaded PA’s and models with Isolator in between to

eliminate mismatch

Demo 4: Results