Hi all,
I'm building an ambient light rejection circuit which measures the scattered light from a LED pulse which is driven by a 1kHz square wave.
I don't have a strong signals background, but I was wondering if anyone out there wanted to comment (or could point me to some info) on design considerations when dealing with square wave AC signals over sinusoidal signals.
I'm planning to read the output signal into a ADC when the LED pulse is high. Unfortunately, with the various filters I've used in my circuit the final output is far from a square wave.
I was hoping to implement a way to average ADC samples over the duration of the LED pulse (performed by a uprocessor) but given the non-top hat form of the signal I need to think of a different way to do it. I'm probably going to run the output through a precision rectifier to remove any negative voltages (which occur during the OFF state of the LED). Is there any circuit (perhaps a unique kind of rectifier) that can provide a reasonably constant flat signal for the ADC to sample from?
Any suggestions would be hugely appreciated!
Thanks in advance,
Stuart
I'm building an ambient light rejection circuit which measures the scattered light from a LED pulse which is driven by a 1kHz square wave.
I don't have a strong signals background, but I was wondering if anyone out there wanted to comment (or could point me to some info) on design considerations when dealing with square wave AC signals over sinusoidal signals.
I'm planning to read the output signal into a ADC when the LED pulse is high. Unfortunately, with the various filters I've used in my circuit the final output is far from a square wave.
I was hoping to implement a way to average ADC samples over the duration of the LED pulse (performed by a uprocessor) but given the non-top hat form of the signal I need to think of a different way to do it. I'm probably going to run the output through a precision rectifier to remove any negative voltages (which occur during the OFF state of the LED). Is there any circuit (perhaps a unique kind of rectifier) that can provide a reasonably constant flat signal for the ADC to sample from?
Any suggestions would be hugely appreciated!
Thanks in advance,
Stuart