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Second order sigma delta modulator

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shanmathi

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Hi all,
I have developed a second order sigma delta modulator. however, the output doesn't look as expected. For positive input cycle I get a series of short pulses and for negative input cycle the positive pulse is modulated. what might be the mistake? I have attached the output and schematic colour_op1.jpgcolour_sch.png
any help is much appreciated
 

Does it operate with lower clock frequency?
I would check the last dff's input signal, then the previous stage's input (what is tiq?) and so on. If the input signal is not held for enough time at the DFF's input it can't store the data. It needs a minimal impulse length.
 

shanmathi said:
however, the output doesn't look as expected.
Click to expand...
Your simulation is Shooting-Newton-PSS.
If your delta sigma modulator works correctly, a fundamental period is nerver equal to a period of input signal.

Show me netlist fragments regarding analysis and signal source.
Show me simulation logfile.
 

frankrose said:
Does it operate with lower clock frequency?
I would check the last dff's input signal, then the previous stage's input (what is tiq?) and so on. If the input signal is not held for enough time at the DFF's input it can't store the data. It needs a minimal impulse length.
Click to expand...

It does operate with lower clock frequency. TIQ stands for Threshold Inverter Quantizer. It is a 1-bit comparator.

what is SCE to AUX? I'm new to cadence. pls explain.
 

Sorry, it is not a cadence thing, it is just a motto. By a NASA engineer, from the launch of Apollo 12. Google for it.
Did you check this comparator's output at higher clock frequency?
 


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