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

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

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)

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.

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

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

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

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)

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

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

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

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

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)