1. 전자파 연구실 1. Fundamentals

2. 전자파 연구실 1.1 Frequency and time Passive circuit elements is emphasized in high speed digital design : Wires, PCB, IC- package High speed design studies how passive circuit elements affect performance : Signal propagation (ringing, reflections), crosstalk, EMI Short ground wire 0.01Ω (at 1kHz) 1.0 + j 50 Ω (at 1GHz)

3. 전자파 연구실 Signal spectrum Pulse rising time The most of the energy of a pulse signal is contained within the frequency of f knee. Any circuit which has a flat frequency response up to f knee will pass a digital signal practically undistorted.

4. 전자파 연구실 Spectrum of trapezoidal pulses

5. 전자파 연구실 f = 10MHz, t r = t f = 15ns f = 10MHz, t r = t f = 5ns Signal spectrum of pulses which have the same oscillating frequency but with different rising times. Rising time 에 따른 spectrum 변화 With long rising/falling times, high frequency components of a signal spectrum decrease. But with wider rising edge, uncertainty in decision as to logic states increases jitter noises (phase noise). f knee = 100MHz f knee = 33MHz

6. 전자파 연구실 Lumped vs. distributed circuit concept If the propagation distance during t r is smaller than the length of a line trace, the circuit is regarded as a distributed one.

7. 전자파 연구실 Four kinds of reactance In high speed circuits, passive circuit elements become important Capacitance, Inductance, Mutual inductance, Mutual capacitance. Capacitance

8. 전자파 연구실 Capacitance measurement Example 1.1

9. 전자파 연구실 Pulse generator 2.6V 63mV

10. 전자파 연구실 Equivalent circuit 21:1 probe DUT

11. 전자파 연구실

12. Inductance measurement

13. 전자파 연구실 Example 1.2 Shorted to GND Dielectric thickness=8 mil Copper thickness=2.1mil Line width = 10mil Length = 1000 mil Diameter = 35mil PCB copper thickness : The copper in a PCB is rated in ounces, and represents the thickness of 1 ounce of copper rolled out to an area of 1 square foot. For example a PCB that uses 1 oz. copper has a thickness of 1.4mils. π-equivalent circuit

14. 전자파 연구실

15. Measurement setup

16. 전자파 연구실 Measurement setup in Example 1.1 Due to short time constant L/R, measurement is difficult. (R=503Ω)

17. 전자파 연구실 Revised measurement setup The time constant L/R becomes larger due to a smaller resistance. (R=7.6Ω)

18. 전자파 연구실 With 800ps rising time pulse, frequency component up to 625MHz (knee freq.) should be considered.

19. 전자파 연구실 1.8 More accurate method Measure total area under a response curve to obtain accurate result.

20. 전자파 연구실 1.9 Mutual capacitance Interactions solely due to electric field which is proportional to voltages. 1.The coupled current flowing in C M is much smaller than the primary signal current in circuit A, so C M does not load circuit A. 2.The coupled signal voltage in circuit B is smaller than the signal on A. We assume the voltage difference between A and B simply equals V A. 3.Assume the capacitor has a large impedance compared with the impedance to ground of circuit B. We calculate the coupled noise voltage as I M times the impedance of circuit B to ground. Simplifying approximation

21. 전자파 연구실 Example 1.3

22. 전자파 연구실 Mutual capacitance of terminated resistors To simplify the coupling mechanism occurred in a distributed circuit, a resistor is represented by a series of two resistor with half the original resistance.

23. 전자파 연구실 1.10 Mutual inductance

24. 전자파 연구실 Crosstalk due to mutual inductance Crosstalk = 1.In case of multiple interfering sources, estimate the mutual inductances between each pair of elements separately and then sum together the fractional crosstalk from each sources to each receiving circuit. 2.An interference level as low as 2%, summed over five nearby sources will contribute 500mV of interference in a TTL system, which is larger than typical noise margins and a serious problem.

25. 전자파 연구실 Measurement of mutual inductance

26. 전자파 연구실 Example 1.4 800 ps rising time

27. 전자파 연구실 Original circuit Lumped element equivalent circuit

28. 전자파 연구실 Crosstalk due to two mechanisms Inductive Capacitive Measured value 4.6div 2.7div

29. 전자파 연구실 Skin effect

30. 전자파 연구실