A study of NEO (Non-linear Energy Operator) and it's popular application in spike detection for neural signals, ECG signals, etc. And hardware realisation of the same.
The implementation can be looked at in these major stages:
|_ Block design of NEO with operators involved
|_ Building subcircuits for operators
|_ Building the complete circuit using these subcircuits
|_ Verification and testing: providing different input signals and analysing the outputs
The final implementation would look something like this:
- The differentiator gives inverted output, being corrected by cascading an active inverter.
- made by cascading two differentiators.
- using AD633 IC.
| input (square wave) | output |
|---|---|
 |
 |
inputs: red and blue
outputs: green
Input is a triangular wave superimposed with thermal noise
So far I'm done with implementing the differentiator and double differentiator blocks on breadboard using UA741 op-amp.
| differentiator | double differentiator |
|---|---|
 |
 |
This is the schematic that is being used for testing in simulation.
Differentiator block cascaded with inverter works
sine becomes cosine
The multiplier works too. sine gets squared (notice how the freq is doubled).
... work in progress