The Basic Principles of Signal Integrity.ppt

The Basic principles of Signal Integrity
Elie Michael Issa
Signal Integrity Engineer
Hewlett Packard
Houston,Texas
03/11/2003
What is Signal Integrity?
It is the field that came to existence after the signal edges became shorter and faster; making
the effects of the interconnect more important on the system behavior. Simulation tools and testing instruments have been designed and tuned to answer
to the market demand for better understanding of
signals behavior and transmission line effects.
Transmission Lines
Transmission line is the medium where the ic energy flow from one end to another.
It exists in various forms depending on the applications. What interest us mostly in our applications for digital munication designs are:
1- Microstrip
2- Stripline
3-Coaxial
4-Twisted pair
Microstrip
Since it lays on the surface layer of the PCB; it has a faster velocity of propagation than the stripline. This is due to a lower effective dielectric.
Also, its lower effective dielectric, allows it to have
Microstrip
a smaller cross section area than the stripline for
the same Impedance.
Disadvantages:
-Higher skin Effect than stripline since current flow on
one surface (>StriplineRs)
-Higher Crosstalk than stripline due to Far End Crosstalk
-EMI radiation
-More exposed to hazards
Stripline
It lays sandwiched between two planes.
The advantages of Stripline are:
-Very Low Far End CrossTalk
-Low skin effect(current flow on
both surfaces of conductor)
-No EMI
-Better protection from hazards
Coax
Coax cables are widely used in the industry.
Among its advantages
are:
1-Low Loss
2-Low Radiation if properly
shielded
3-Low Crosstalk
Twisted pair
Twisted pairs are usually
Used in differentially driven systems.
Advantages:
1-Low Crosstalk
2-Mid radiation and
susceptibility
Transmission Line
Lossy line:
The impedance of lossy
Line is :
Z = ((R+jwL)/(G+jwC))1/2
Where R and G are the
Frequency dependent
Transmission Line
Parameters.
R is the re