Signal Integrity Asif

Signal Integrity

By Asif

Outline

Overview of SI

Transmission Line Theory

Time Domain Analysis

Frequency Domain Analysis

Equalization Techniques

High Speed interfaces

3D Modeling

Overview

Signal integrity is an important activity at all levels of

electronics packaging and assembly, from internal

connections of an integrated circuit (IC),through

the package, the printed circuit board (PCB),

the backplane.

SI is a set of measures of the quality of an electrical

signal.

That ensures all signals transmitted are received

correctly.

That ensures signals don’t interfere with one another.

That ensures signal don’t damage any device.

Transmission line Theory

Introduction

Lossy Transmission Line

Lossless Transmission Line

Single Ended Signaling

Differential Signaling

Tightly Coupled & Loosely Coupled

Introduction

The transfer of energy from one point to another takes

through either wave guides or transmission lines.

In an electronic system, the delivery of power

requires the connection of two wires between the

source and the load. At low frequencies, power is

considered to be delivered to the load through the

wire.

In the microwave frequency region, power is

considered to be in electric and magnetic fields that

are guided from lace to place by some physical

structure. Any physical structure that will guide an

electromagnetic wave place to place is called a

Transmission Line.

Lossy Transmission Line

Impedance of lossy Transmission line is,

Where R-series resistor of the conductor

L-due to the magnetic fields self inductance

C-shunt capacitor between two conductor

G-shunt resistor between signal wire and the return wire

Z0-charecteristic impedance

Lossless Transmission Line

Impedance of lossless Transmission line is,

When the R and G are negligibly small the

transmission line,the model depends only on the L

and C elements

Single Ended Signaling

A single-ended measurement is taken as the voltage

difference between a wire and ground.

The noise is only on the positive wire, and as a

result, it is still measured along with the output

voltage from the sensor

Single-ended signaling is the simplest and most

commonly used method of transmitting electrical

signals over wires.

One wire carries a varying volt that represents the

signal, while the other wire is connected to a

reference voltage, usually gnd.

Differential Signaling

Differential signal is a method of transmitting

electrically with two complementary signal sent on

two pared wires called differential pair

It is Suitability for use with low-voltage electronic

signals.

It will resist the EM interferences.

The main benefit of a differential measurement is

noise rejection

Tight coupling &Loosely coupled

Tight coupling is usually reduces flexibility and re-usability A Tightly

Coupled Object is an object that needs to know quite a bit about

other objects and are usually highly dependent on each other's

interfaces.

Loosely coupled to reduce the inter-dependencies between

components of a system Loose coupling is a much more generic

concept intended to increase the flexibility of a system

Difference between Time& Frequency

Domain Analysis

Time domain analysis examines the amplitude vstime characteristics of a measuring signal

Time domain analysis gives the behavior of the signal over time

Frequency domain analysis replaces the measured signal with a group of sinusoids which, when added together, produce the waveform equivalent to original

The relative amplitudes, frequency, phases of the sine waves are examined

Frequency domain analysis is much easier, some equations are can’t be solved while time domain they can be solve easily in frequency domain

Difference between Time& Frequency Domain

Analysis

Time Domain Analysis

Introduction

Eye pattern

Jitter

Setup/Hold Time

Rise Time/Fall Time

Introduction

A graphical representation of the change of some

value with respect to time

In the time domain, the signal or function's value is

known for all real numbers, for the case

of continuous time, or at various separate instants in

the case of discrete time

A time-domain graph shows how a signal changes

with time, whereas a frequency-domain graph shows

how much of the signal lies within each given

frequency band over a range of frequencies.

Eye Pattern Evoluation of combined effect of channel noise and Intersymbol

interference(ISI).

Open eye pattern corresponds to minimum signal distortion.

Jitter

• Jitter is the deviation from true periodicity of a presumed

periodic signal in electronics.

• Jitter period is the interval between two times of

maximum effect (or Minimum effect) of a signal that

varies with time.

1.Ranfom Jitter(gaussian Jitter)

• Is unpredictable electronic noise

• Random jitter typically follows a gaussian distribution or

normal distribution

• Caused by thermal noise and another reason for jitter to

have a distribution or normal distribition

Jitter(Cont…)

2.Deterministric Jitter

It is a type of clock timing jitter or data signal jitter is

predictable and reproducible

The peak to peak value of this jitter is bounded and

the bounds can easily be observed and predicted

Total jitter

Total jitter (T) is the combination of random jitter (R)

and

deterministic jitter (D)

T = Dpeak-to-peak + 2× n×Rrms,

in which the value of n is based on the bit error rate

(BER) required of the link

Setup Time Setup time is the minimum amount of time the data signal should be

held steady before the clock event , so that the data are reliably

sampled by the clock.This applies to synchronous circuit such as flip

flop.

The time when input is available and stable before the clock pulse is

applied is called setup time.

Hold Time Hold time is the minimum amount of time the data signal should be

held steady after the clock event, so that the data are rapidly

sampled.

The time after clock pulse where data input is held stable is called

hold time.

Rise Time/Fall Time

Rise Time(TR)

Amount of time it takes the output voltage to go from 10%

of the Logic "1" level to 90% of the Logic "1" level..

Measured in nS.

Fall Time(TF)

The time required for the output voltage to go from 90%

of the Logic "1" level to 10% of the Logic "1" level..

Measured in nS.

Frequency Domain Analysis

Introduction

S-Parameter

Insertion Loss

Return Loss

Cross Talk

Nyquist Frequency

Knee Frequency

Skew

Introduction

The frequency response of a system is defined

steady state response of the system

A graphical representation of the amount of energy

present in a signal at each of many frequencies

The frequency response of a system is defined

steady state response of the system

The frequency domain values are really just a series

of sinusoidal equivalents, so amplitudes are usually

represented the same as in the time domain.

The frequency domain is usually derived by

computing a Fast Fourier Transform (FFT) of a time

domain signal.

S-Parameter

S-Scattering parameters which describe electrical behavior of

transmission line signals.

The following information must be defined when specifying a set of

S-parameters:

• The Frequency(f)

• Characteristic impedance (Z0)

• Number of Ports

Use it as a simplified passive interconnect model that

– simulates faster,

– is easier to correlate with actual hardware, and

– can be offered to the industry while protecting IP

S-Parameter(cont…)

A behavioral representation (model) of passive

interconnect

Insertion Loss

The loss of signal power resulting from the insertion

of a device in a transmission line

Is usually expressed in db

PT is power transmitted

PR is power received

Return Loss

The loss of power in the signal returned/ reflected by

a transmission line

This discontinuity can be terminating load or with a

device Inserted in the line

Pi incident power

Pr reflected power

Cross Talk(XT)

crosstalk (XT) is any phenomenon by which

a signal transmitted on one circuit or channel of

a transmission system creates an undesired

effect in another circuit or channel.

Crosstalk (cont….)

Cross Talk occurs on PCB and twisted wire cable


Near end crosstalk(NEXT)

NEXT is a measure of the ability of the cabling to reject crosstalk

The signals traveling through adjacent pairs of wire in twisted pair

cabling interfere with each other

Interference between two pairs in a cable is measured at the same

as the interfering transmitter

Power Sum Near end Crosstalk(PSNEXT)

A NEXT measurement which includes the sum of crosstalk

contribution of all adjacent pairs

Far end Crosstalk(FEXT)

Interference between two pairs of a cable measured at the other end

of the cable with respect to Interfering transmitter


Equal Level Far end Crosstalk(ELEFEXT)

An FEXT measured with attenuation compensation.

Power Sum Far end Crosstalk(PSFEXT)

It is the sum of all interference signals, which are

coupled in a pair of conductors.

Nyquist Rate

Minimum sampling rate required to prevent alaiasing

Defines the maximum sampling rate given a fixed

maximum frequency

The maximum frequency that won’t be alaised, is “half”

the given sampling rate.

fs≥2fc

Fs- Sampling Frequency fc- Highest Frequency

Nyquist Rate(cont…)

Alaiasing

The sampling points are correct but produce a

completely different wave

Knee Frequency

Knee frequency is an estimate of the highest frequency content of the signal

If the Rise Time is smaller the highest frequency content will have higher frequency

If ‘t’ denotes the 10% to 90% rise time of a signal,then an estimate for the highest frequency content of the signal(or)Knee Frequency given by

fmax Highest Frequency content

Skew

Skew is the time delta between the actual and expected arrival time

of a clock signal.

The time delay difference between two or more signal path is called

skew

It can be intrinsic or Extrinsic

Intrinsic: Propagation delay between the device outputs.

Extrinsic:Due to unbalanced trace lenghts (or) output loading.

High Speed Interfaces

DDR(Double Data Rate)

SAS(Serial Attached SCSI)

SATA(Serial Advanced Technology Attachment)

USB(Universal Serial Bus)

PCIE(Peripheral Component Interconnect Express)

DDR(Double Data Rate)

DDR SDRAM is a class of memory integrated circuits used in computers.

DDR SDRAM, also called DDR1 SDRAM, has been superseded by DDR2 SDRAM and DDR3 SDRAM.

Compared to single data rate (SDR) SDRAM, the DDR SDRAM interface makes higher transfer rates possible by more strict control of the timing of the electrical data and clock signals.

DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a SDR SDRAM running at the same clock frequency.

DDR SDRAM gives a transfer rate of (memory bus clock rate) × 2 (for dual rate) × 64 (number of bits transferred) / 8 (number of bits/byte). Thus, with a bus frequency of 100 MHz, DDR SDRAM gives a maximum transfer rate of 1600 MB/s.

DDR(cont…) VERSIONS

• SDRAM-66 MHz,100 MHz,133 MHz

• DDR1-266,333,400 MHz

• DDR2-400,533,677,800 MHz

• DDR3-460,533,677,800,933,1066 MHz

• DDR4-1600 to 3200 MHz

LRDIMM

DIMM-Dual Inline Memory Module, comprises a series of

dynamic random-access memory integrated circuits

LRDIMM-Load Reduced DIMM,this technology uses

distributed buffer approach to accomplish memory

bandwidth efficiency

Improve LRDIMM architecture for better SI or data

signals

That support higher densities than RDIMM and contain

memory buffer

LRDIMM uses in memory intensive application in data

centers ,could computing and high performance

computing(HPC) environments

RDIMM

RDIMM-Registered Dual In line Memory Module

This is in constrast to the unbuffered data approach used

with DDR4

DDR4 LRDIMM’s shorter trace length and quicker

buffering scheme make the overall latency and bus

read/write turnaround time compared to DDR4 RDIMM

UDIMM

UDIMM-Unbuffered/Unregistered DIMM

When compared to registered

memory(RDIMM),conventional memory is usually

referred as UDIMM

Most commonly in PC and Laptops

It’s faster than the RDIMM and low cost. But are not

stable as RDIMM

SAS(Serial Attached SCSI)

SCSI-Small Computer System Interface

When it was introduce the speed of SAS is 3Gbps,Then In 2009 the

speed of SAS is 6Gbps,In 2013 speed is increased to 12Gbps

It is point to point serial protocol that moves data to and from

computer storage devices

Types of component,

• Initiator-Request for processing by a target devices

• Target-Contains logical units and target ports

• Service Delivery Subsystem-I/O system transmit initiator to

target and vice versa

• Expanders-Communicate between multiple SAS devices to

initiator port

SATA(Serial Advanced Technology

Attachment)

SATA is the next generation storage interface for

PCs and low-end Servers.

SATA is highly viable for servers and storage

networks

One SATA controller can aggregate multiple ports

Multiple SATA drives can be linked using backplanes

and external enclosures

SATA was designed to provide excellent speed and

storage at a low cost

Cost and scalability provides potential for greater

storage capacity at a lower cost than networked or

server storage

SATA(cont…)

SATA revision 1.0 - 1.5 Gbit/s - 150 MB/s

SATA revision 2.0 - 3 Gbit/s - 300 MB/s


SATA revision 3.1


PCIe(Peripheral Component Interconnect

Express)

PCIe is a high speed serial computer expansion bus.

A computer bus is used to transfer data from one location

or device on the motherboard to the central processing

unit where all calculations take place.

PCIe has been a versatile ,function way to sonnect

sound,video and network card to a mother board.

Two different parts of a Bus

Address bus-transfers information about where the

data should go

Data bus-transfers the actual data

PCIe(cont…)

Plug&Play(PnP)

Automatically recognized and configured to work on

the system.

PCIe(cont…)

Every device has its own dedicated connection,so

devices no longer share bandwidth like they do on a

normal bus.

PCI Express link performance

USB

USB-Universal Serial Bus

Nowadays most of the electronic devices are connected by the USB

USB needs to operate at maximum voltage of 5.00 V and maximum

current of 500-900 mA

USB has can connect maximum number of devices around 127

It is a 4 pin connector

• Pin 1-Vcc(+5V)

• Pin 2-(D-)

• Pin 3-(D+)

• Pin 4-Gnd

USB(Cont…)

VERSIONS,• USB 0.7 – released in November 1994

• USB 0.8 – released in December 1994

• USB 0.9 – released in April 1995

• USB 0.99 – released in August 1995

• USB 1.0 - Release Candidate – released in November 1995

• USB 1.x -12 Mbps

• USB 2.0 -480 Mbps

• USB 3.0 -3.2 Gbps

• USB 3.1 -10 Gbps

Equalization Techniques

Emphasis

FFT

IFFT

FFE

DFE

CTLE

FIR

FFE

Emphasis

Emphasis is the intentional alteration of the amplitude-vs

-frequency characteristics of the signal to reduce the

effects of noise in a communication

Pre-emphasis:

Pre-emphasis refers to boosting the relative amplitudes

of the modulating voltage for higher audio frequencies

from 2 to approximately 15 KHz.

Which boosting the relative amplitudes for high frequency

to improve the overall signal to noise ratio and the mirror

operation is called de-emphasis

pre-emphasis is done at the transmitter

Emphasis(cont…)

De-emphasis:

De-emphasis is the complement of pre-emphasis.

De-emphasis means attenuating those frequencies by the amount by

which they are boosted.

de-emphasis is done in the receiver.

The whole system of pre-emphasis and de-emphasis is called

emphasis

FFT

Fast Fourier Transform (FFT) is to compute

the discrete Fourier transform (DFT) and its

inverse. Fourier analysis converts time (or space) to

frequency and vice versa

The DFT is most important in the area of frequency

(spectrum) analysis because it takes a discrete signal in

the time domain and transforms that signal into its

discrete frequency domain representation

The most important difference is that an FFT is much

faster than DFT

FFT algorithms are also much more accurate than

evaluating the DFT

IFFT

The Fourier transform is used to convert the signals from time domain to frequency domain and the Inverse Fourier transform(IFFT) is used to convert the signal back from the frequency domain to the time domain

FFT which is a technique to analyse signal in frequency domain. If signal is in time domain and are not able to find problem then we can take FFT of this signal and find out how many frequency components are present and analyse it better

if we convert it back to time domain then all frequency will be available but it will be difficult as which frequency was present at what time, so one can replace IFFT and FFT

FFE

Feed-Forward Equalization (FFE) is an equalization

technique that corrects the received waveform with

information about the waveform itself and not information

about the logical decisions made on the waveform

FFE basically acts like a FIR (finite impulse response)

filter and uses the voltage levels of the received

waveform associated with previous and current bits to

correct the voltage level of the current bit

FFE is only concerned with correcting voltage levels in

the waveform

The mathematical expression of FFE is,

e(t) = c0r(t - (0TD)) + c1r(t - (1TD)) + c2r(t - (2TD))

DFE

Decision Feedback Equalization (DFE), DFE

calculates a correction value that is added to the

logical decision threshold

The mathematical expression of FFE is,

V(k) = c1s(k - 1) + c2(k - 2)

DFE and FFE are different equalization techniques,

it is not uncommon to use both at the receiver

DFE and FFE are both useful equalization

techniques that can be used to open closed eyes at

the receiver

CTLE

CTLE- Continous Time Linear Equalization

In the transmitter, equalization using a CTLE is

implemented to provide pre-emphasis of the high

frequency leading edge of bit transitions

This can be done in two techniques are,

1) CTLE using high pass filter (HPF) with poles and

zeros

• A HPF CTLE can provide emphasis in its high

frequency response and can be created using a

single pole and zero, H(s) = K*(s-z)/(s-p)

2)CTLE using a feed-forward equalizer (FFE)

• A FFE CTLE can provide emphasis in its high

frequency response and be created using

delays,gains and summer

FIR

Finite impulse response (FIR) filter is

a filter whose impulse response (or response to any

finite length input) is of finite duration, because it

settles to zero in finite time

This is in contrast to infinite impulse response (IIR)

filters, which may have internal feedback and may

continue to respond indefinitely

For a discrete-time FIR filter of order N,

3D Modeling

Introduction

MOM-Method Of Moments(2D)

Quasi Static Modeling(2.5D)

FEM-Finite Element Modeling(3D)

FDTD-Finite Difference Time Domain(3D)

Introduction

Advantages of Simulation Modeling are,

• Optimize the geometry for strength and weight

• Select materials that meet weight, strength, and budget

requirements

• Simulate part failure and identify the loading conditions

that cause them

MOM

MOM-Method Of Moments

Analyzing PCB with respect to radiated emission and

radiated susceptibility in the frequency domain

Can be used for analyzing any planar structure

EMC applications-Electro magnetic

compatability,shall not generate EM disturbance

Quasi Static Modeling(2.5D)

FDTD-Finite Difference Time Domain Method

Numerical Analysis technique

FDTD can cover wide range frequency with a signal

simulation

It will used in a non linear material property

FDTD uses the E and H fields directly. Since most

EMI/EMC modelling applications are interested in

the E and H fields

FEM

FEM-Finite Element Modelling

It is a numerical technique for finding approximate

solutions to boundary value problems for partial

differential equations

It uses subdivision of a whole problem domain into

simpler parts, called finite elements

from the calculations of variations to solve the

problem by minimizing an associated error function

It will solve electro magnetic field(TE,TM,TEM)

FDTD

FDTD-Finite Difference Time Domain Method

Numerical Analysis technique

FDTD can cover wide range frequency with a signal

simulation

It will used in a non linear material property

FDTD uses the E and H fields directly. Since most

EMI/EMC modelling applications are interested in

the E and H fields

DESIGN OF EXPERIMENTS

It is a design of any information gathering exercise

where variation is present

These statics used for controlled experiments

Advantages of DOE,• Reliability is increased

• Shorter development time

• Process performing normal

• Cost is less

• Reduction of process variation

GENETIC ALGORITHM

Genetic algorithm(GA) is a heuristic that mimics the

process of natural selection

Heuristic is designed for solving problem more

quickly

GA which generates solution to optimization problem

using techniques inspired by natural evolution

ARTIFICIAL NEURAL NETWORK(ANN)

An Artificial Neural Network (ANN), usually called neural

network (NN), is a mathematical model or computational

model that is inspired by the structure and/or functional

aspects of biological neural networks

A neural network consists of an interconnected group

of artificial neurons, and it processes information using

a connectionist approach to computation

HFSS-High Frequency Structural Simulator

Solution Types:

Driven Modal: Use this type of solution for passive high frequency

structures such as microstrips, waveguides, and transmission lines.

Driven Terminal: Use this type for simulations that deal with

signal integrity for models that have multi-conductor transmission lines.

Eigenmode: Use this type to calculate resonances of a given

structure(e.g. filters).

Transient: Use this type to employ time-domain solutions for

simulations with pulsed excitations such as ultra-wide band antennas.

Signal Integrity Asif

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