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An Analog Wavelet Transform CMOS Imager Chip

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Presentation on theme: "An Analog Wavelet Transform CMOS Imager Chip"— Presentation transcript:

1 An Analog Wavelet Transform CMOS Imager Chip
Adeel Abbas, Saurav Panda, Vikram Shirgur Graduate Advisor: Shantanu Chakrabartty Analog and Digital VLSI Systems

2 Motivations Hardware Implementation of Image Compression Small size Reconfigurable to compute user-defined functions (e.g. Walsh Transform, Hadamard Transform) Edge detection, pattern matching

3 Wavelet Transform Theory
Multi-resolution feature extraction Many basis functions available, Haar Wavelet implemented Haar transform is a combination of summing and difference operations

4 Hardware Implementation
Haar Transform can be realized as a Matrix Vector Multiplication problem W (i,j) = ( ΣA(i)×P(i,j) ) × B(j) Multiply with either +1, 0 or -1 Inputs are presented in bit-serial fashion

5 System Architecture 16 x 24 pixel array
2 CDS stages for inner and outer products Product coefficients input through shift registers

6 The APS Cell Charge mode implementation
Product Coefficient provided in two phases Output of all cells is dumped to a common line Charge is either dumped or extracted from output line

7 The APS Cell (Layout) Uses photodiode type design
Susceptible to mismatches in transistor sizing Fill Factor: 60 % Dimensions: 89λ x 89λ

8 CDS Circuit Cascoded inverter used for high gain
Phase of B(i) determines whether we connect output capacitor to CDS or Vref CDS stage 1 adds charge across columns, Stage 2 adds output of CDS circuits in stage 1

9 Complete Schematic

10 Simulation of APS And Inner Product
Operating Frequency of 11KHz Photocurrent of 60pA Sequencing of 1st and 2nd stage clocks is very important Here we are multiplying by -1

11 Simulation Results for Outer Product (4×4)
Here again we are multiplying by -1 Output valid during Hold phase of stage 2 Voltage range of 1.76V to 4.23V, with reference at nearly 3 V

12 Complete Layout with Pad-frame

13 Future work Parallel readout (currently can be used as a random-access imager) Extend for a 3 x 3 pad-frame. Would allow a resolution of around 72x72 More test pins. Currently the chip utilizes 29 pins

14 Questions?


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