1. Differential Signals
-Definition, Characteristics, Impedance and Matching,
S-parameter
2013.03.07
EMC 연구실
김종현

2. 목차
1. Definition
2. Pros and Cons
3. Characteristic(Impedance)
4. Matching Method
5. S-Parameter

3. Definition

4. Pros and Cons
 Immunity to
Crosstalk/EMI
 Immunity from
 Hard to design
Ground Noise
Merits Demerits  Time Difference
 Power Saving by use
Problems (Skew)
of small voltage
 High Data Speed
Possible

5. Characteristics of Differential Signals
V V V V
C increases. C decreases.
I  I I I
L decreases. L increases.
Odd- and even-mode electric and magnetic field patterns for a simple two-conductor system.
L11 L12 L11 L12
Z odd Z even
C11 C12 C11 C12

6. Differential Characteristic Impedance
Z diff = 2* Zo (1 - 0.48 e-0.96D/H)
Z diff = 2* Zo (1 - 0.347 e-2.9D/B)

7. How to Mach terminals
R1 R1
R3
R3
R2 R2
R1 R2 Z even R1 R2 Z odd
2Z even Z odd 1
R3 R3 Z even Z odd
Z even Z odd 2

8. Mixed-Mode S-parameters
Port1 Port2 Port1 Port2
2Port DUT
4Port DUT
differential line
Port3 Port4
Sd 1d 1 Sd 1d 2 Sd 1c1 Sd 1c 2
Sd 2 d 1 Sd 2 d 2 Sc 2 d 1 Sd 2c 2
S mm
Sc1d 1 Sc1d 2 Sc1c1 Sc1c 2
Sc 2 d 1 Sc 2 d 2 Sc 2 c1 Sc 2 c 2
S11 S13 S31 S33 S12 S14 S32 S34 S11 S13 S31 S33 S12 S14 S32 S34
1 S 21 S 23 S41 S43 S22 S24 S42 S44 S 21 S 23 S41 S43 S22 S24 S42 S44
2 S11 S13 S31 S33 S12 S14 S32 S34 S11 S13 S31 S33 S12 S14 S32 S34
S 21 S 23 S 41 S 43 S 22 S 24 S 42 S 44 S 21 S 23 S 41 S 43 S 22 S24 S42 S44

9. 5.1 표 9 / 14
Reference
번호 제목 저자
1 Mixed-Mode S-Parameter Characterisation of Differential Structures W.Fan
Combined Differential and Common-Mode Scattering Parameters: Theory and
2 David E. Bockelman
SImulation
3 Asymmetric Coupled Transmission Lines in an Inhomogeneous Medium VIJAI K. TRIPATHI

10. 감사합니다