1. Design of Digital Filter Bank and General Purpose Digital Shaper
Attiq ur Rehman

2. Digital Filtering Baseline Correction and Subtraction I
Digital Shaper (Signal Conditioning & Baseline II)

3. Proposed Architecture for Signal shaping
BCS I
Removal of DC offset value and slow variations in the baseline.
Dynamic update of threshold with valid peak detection
Digital Shaper
Signal conditioning and baseline restoration
4 Cascaded IIR filters
Adaptive Algorithm for coefficients (optional – based on Analysis and enough motivation)
Baseline correction II
Moving average Filter (8 Stage)

4. The Baseline Correction and Subtraction
Objectives
Removal of DC offset
Relatively Stable baseline for Processing (signal conditioning)
Operational Modes
Subtraction Mode
Fixed subtraction
Time Dependent Subtraction
Self-calibration circuit (AUTOCAL)
Conversion Mode
Conversion of the input signal independent of Time
Output values are stored in the LUT addressed by the input values.
Test Mode
LUT to store the test vectors to inject into processing chain for test purpose.

5. Systematic perturbation Systematic perturbation
Baseline Correction 1
Systematic perturbation
Baseline drift
fpd = 0
Fixed pedestal
Slow drifts
Systematic perturbation
Combination
H(z) = (1-z-1) / (1-0.5)z-1

6. The Baseline Correction and Subtraction I
Low frequency perturbation
Fixed Pedestal
Systematic interference
After BCS I

7. Baseline Correction 1 Evaluation of AUTOCAL Proposed AUTOCAL
Truncation/ Rounding Improvement
Shifts in Baseline
Proposed AUTOCAL
Configurable depth
Rounding off data at the result
18 bit Arithmetic

8. Digital Signal Shaper (Tail cancellation and Base Line Restoration)
Objective
Removal of Tail and Pileup Effects
Efficiency of Zero Suppression
Structure
Four cascaded first order IIR Filters
Offline / Online calculation of coefficients and configured in first phase of operation 1 - L z K 2 3
Adaptive Coefficient
Determination (
Learning Algorithm )
From BCS
Configuration 8 –
TAP
MAF
BCS II
Tail cancellation Filter
BCS II
Motivation for this structure (with an idea of general Purpose charge readout chip)

9. Digital Signal Shaper (Tail cancellation and Base Line Restoration)
If zero-suppression (straight horizontal line) is directly applied, several clusters would be lost due to pileup

10. Digital Signal Shaper (Tail cancellation and Base Line Restoration)
Functions
signal (ion) tail suppression
pulse narrowing  improves cluster separation
gain equalization
Filter
compensates undershoot
Architecture
3rd order IIR filter
18-bit fixed point 2’sC arithmetic
single channel configuration  6 coefficients / channel
Filter
Narrows the pulse
11 bits
2’sC
18 bits
18 bits
2’sC
11 bits
2’sC
word
extension
3rd order
IIR filter
word
rounding
input
output
11 bit
18-bit fixed point arithmetic
Z-1 L1 K1 L2 K2 L3 K3

11. Digital Signal Shaper (Tail cancellation and Base Line Restoration)
Filter Bank
Structure
4 Cascaded first order IIR Filters
Programmable / Adaptive coefficients
Adaptive Processing Block
Objective
To calculate the coefficients for filter bank
Functional Description
Configuration
Initial parameters of the pulse based on detector type / experimental setup
Run Time
Learning Algorithm
Initial setup during Configuration
Selection of good pulses based on minimum height and width.
Weights/ coefficients determination based on intermediate shape of the signal

12. The Baseline Correction II
Evaluation of Fixed (Double) threshold
Change in Average Height of Signal Peak
Peaks of lower height
Shift of Baseline
Effects of Undershoots
Above stated factors may cause the fixed (double) threshold scheme to be in efficient.
Proposed Solution
Continuous update of baseline
8 stage calculation of baseline with availability of intermediate value

13. The Baseline Correction and Subtraction II
Objectives
Removal of non systematic effects on signal.
Functional blocks
Acceptance Window
Dynamic Threshold Scheme
8 Samples window
8 – Tap MAF
F(z) = z-1[1-1/8*(1+ z-1+z-2+….. z-7)