1. Resistance per Unit Length Inductance per Unit Length Capacitance per Unit Length Conductance per Unit Length Lossless case: R = 0, G = 0 Transmission Line

2. Physical description thickness width length crossection Electrical characteristics Z0 (impedance) Tpd (delay) loss

3. Transmission Line Characteristics

4. Voltage and Current Waves V(x,t) = Vi + Vr I(x,t) = Ii + Ir 1) For the first waveform, the transmission line shows its line impedance 2) The incident wave travels down the line. After Tpd time, the waveform hits the load, and a portion of the wave is reflected. 3) The reflected wave travels down the line. After Tpd time, the waveform hits the source, and a portion of the wave is reflected.

5. Definition: Special cases: when Z = Z0 (matched impedance) when Z = infinite (open circuit) when Z = 0 (short circuit ) Reflection Coefficient

6. normalembedded Conductor dielectric reference plane Disadvantages: nonhomogeneous medium (far- end crosstalk) Potential EMC problems Advantages: Faster than strip-lines Good for higher impedance Propagation speed is reduced of Microstrips (normal and embedded)

7. normal Disadvantages: Slower than microstrip Advantages: Homogeneous medium (no far- end crosstalk) Reduced EMC problems Good for lower impedance Good for balanced signals (dual offset) dual offset Propagation speed is reduced of Striplines

8. Crosstalk is coupling of unwanted energy (signal) onto a victim line Coupling among TL (coupled lines in PCBs/leadframes/cables) Impedance of common current returns paths (Ground bounce) Coupling in connectors Indirect electromagnetic coupling (EMC) In this document crosstalk will refer to the direct coupling mechanism only (coupled lines in PCB/leadframe/cables and connectors) For each signal there is a “noise budged” allowed. All previous phenomena contribute to this budged What-is Crosstalk

9. Clock signals Long address / data buses Analog signals in digital circuits Asynchronous Signals (reset, etc) The configurations could be very complex where more signals can contribute to total crosstalk noise. For example: Ground signal Analog signal (victim) Clock signal (aggressor) Reset signal (victim) Read/Write signal (aggressor) Data signal(aggressor) Sensitive Signal Lines

10. A single line presents a very simple electromagnetic field configuration In general: a multi-conductor system of n conductors (excluding the reference conductor) shows n propagation modes. Two coupled lines show a more complex electromagnetic field configuration. There are two propagation modes and two propagation speeds. Electrical (green) and magnetic (blue) fields Electrical fields for even (left) and odd (right) for conductor A (magnetic field is omitted for simplicity) A B Parallel Trace Crosstalk

11. I c - I l RtRt cmcm lmlm RtRt RtRt RtRt x I c + I l Far-end crosstalk Near-end crosstalk ToTo 2T o T r +2 T TrTr T r + T reflection Case study: two-line symmetrical: two propagation MODEs (odd and even) homogeneous material -> Far-end crosstalk = 0 R t = termination resistor T r = rise time of the incident wave T o = propagation delay of the odd mode T e = propagation delay of the even mode T = difference between even and odd propagation delays Note: R t is calculated in order to match the impedance of the coupled structure to reduce reflections B A CD A B C D

12. Far-End Crosstalk RtRt cmcm lmlm RtRt RtRt RtRt x B A CD Far-end crosstalk ToTo TrTr T r + T A B C D The amplitude is a function of the coupling coefficient, but could be is “clamped” if the rise time is larger than the difference between the propagation delays of the two modes. At least, the amplitude can be 0 if the two modes propagates at same speed (case homogeneous material) Far-end crosstalk between two lines with an input signal of 200ps versus  T  T=0p Rise time=200p  T=50p  T=100p  T=150p  T=200p  T=250p  T=300p

13. RtRt cmcm lmlm RtRt RtRt RtRt x B A CD Near-end crosstalk 2T o T r +2 T TrTr A B C D Amplitude is only a function of the coupling coefficient. Near-end crosstalk between two lines with an input signal of 200ps versus  T (50ps step) TT 0 300ps Near-End Crosstalk

14. Incident and Transmitted Pulses RtRt cmcm lmlm RtRt RtRt RtRt x B A CD TrTr A B C D The transmitted pulse shows first an amplitude reduction due to loss of energy coupled to line CD. The incident waveform shows some reflections of the far-end crosstalk due to the different velocity of the propagation modes Reflection