1. Pulse Processing and Shaping
Amin Bagheri

2. I. DEVICE IMPEDANCES II. COAXIAL CABLES: A. Cable Construction
B. Cable Properties
C. Noise Pickup and Component Grounding
D. Characteristic Impedance and Cable Reflections
E. Useful Coaxial Cable Accessories:
1. TERMINATORS
2. PULSE ATTENUATOR
3. PULSE SPLITTER
4. INVERTING TRANSFORMER

3. III. PULSE SHAPING A. CR and RC Shaping: B. Pole-Zero Cancellation
1. CR DIFFERENTIATOR OR HIGH-PASS FILTER
2. RC INTEGRATOR OR LOW-PASS FILTER
3. CR-RC SHAPING
4. GAUSSIAN OR CR-(RC)" SHAPING
5. ACTIVE FILTER PULSE SHAPING
6. TRIANGULAR SHAPING
7. TRAPEZOIDAL SHAPING
B. Pole-Zero Cancellation
C. Baseline Shift:
1. THE ORIGIN OF THE PROBLEM
2. BASELINE RESTORATION
D. Other Pulse Shaping Methods:
1. DOUBLE DIFFERENTIATION, OR CR-RC-CR SHAPING
2. SINGLE DELAY LINE (SDL) SHAPING
3. DOUBLE DELAY LINE (DDL) SHAPING

4. I. Device Impedances

5. II. Coaxial Cables
A. Cable Construction

6. B. Cable Properties
The velocity of propagation for pulses through a coaxial cable is a function only of the dielectric materials separating the central conductor and the outer shield and is inversely proportional to the square root of the dielectric constant
In signal cables, the important specifications are usually the characteristic impedance and the capacitance per unit length
In cables intended to carry bias voltage to detectors, the maximum voltage rating is also important.
For transmission of fast rise time pulses, some attention should be paid to the high-frequency attenuation specifications of the cable.

7. C. Noise Pickup and Component Grounding
When components are physically separated, however, the shield will tend to establish a common ground potential for all components
Computers are a potential source of high frequency noise pickup and may need to be kept at a distance from detectors and preamplifiers where signal levels are low
A technique known as common mode rejection is sometimes helpful in reducing the effects of noise pickup on interconnecting cables.

8. D. Characteristic Impedance and Cable Reflections
pulse transmission through coaxial cables:
low-frequency or slow pulses
high-frequency or fast pulses
Pulses having rise times that are large compared with the transit time are slow pulses, whereas those having a rise time comparable to or shorter than the transit time are fast pulses.
For slow pulses, the important properties are its series resistance and capacitance to ground.
the most significant parameter usually is the cable capacitance.
For fast pulses, the important propertie is characteristic impedance of the cable

9. Characteristic Impedance

10. Characteristic Impedance

11. E. Useful Coaxial Cable Accessories:
1. Terminators

12. 2. Pulse Attenuator

13. 3. Pulse Splitter

14. 4. Inverting Transformer

15. III. PULSE SHAPING

16. A. CR and RC Shaping:
1. CR DIFFERENTIATOR OR HIGH-PASS FILTER
--->

17. 1. CR DIFFERENTIATOR OR HIGH-PASS FILTER

18. 2. RC INTEGRATOR OR LOW-PASS FILTER
--->

20. 3. CR-RC SHAPING

21. 4. GAUSSIAN OR CR-(RC)" SHAPING
5. ACTIVE FILTER PULSE SHAPING
Alternative methods are available to the circuit designer to carry out similar operations using active circuits that incorporate elements such as transistors and diodes.
6. TRIANGULAR SHAPING
It is practically impossible to achieve a triangular shape using passive circuit elements alone 21

22. 22

23. B. Pole-Zero Cancellation23

24. C. Baseline Shift: 1. THE ORIGIN OF THE PROBLEM:
for pulses from radiation detectors, both the amplitude and spacing are variable and the degree of baseline shift is not constant and no adequate compensation can be carried out.
baseline shifts can be eliminated if the pulse shape is made to be bipolar rather than monopolar.
Effects of baseline shifts could also be avoided if all elements were dc coupled 24

25. 2. BASELINE RESTORATION
One method to avoid baseline shift is to use shaping networks that produce bipolar pulses.
The switch is open only during the duration of each pulse
the role of the switch is carried out by diodes1l or by more complex nonlinear circuitry
use of these circuits introduces some degree of additional noise into the system
To be effective, baseline restoration must take place near the end of the signal chain 25

26. D. Other Pulse Shaping Methods:
DOUBLE DIFFERENTIATION, OR CR-RC-CR SHAPING:
to achieve
a bipolar pulse shape 26

27. D. Other Pulse Shaping Methods:
2. SINGLE DELAY LINE (SDL) SHAPING: 27

28. D. Other Pulse Shaping Methods:
3. DOUBLE DELAY LINE (DDL) SHAPING: 28

29. Thank you