Can I filter noise, given a specific filter algorithm?

[AlanKnowler]

I have an array of waveform data captured at 120MHz. I want to apply a specific filter to it remove noise (weighted to perception of eye to noise). Can I implement this in LabVIEW? Any clues how please!

Filter circuit this looks like;

Response of filter looks like this;

Thanks,

Alan

[AlanKnowler]

OK, so with a bit of reading and a bit of playing I have managed to;

1. Perform FFT of my input signal
2. For each element of the frequency domain signal;
• Converted complex to polar
• Applied filter to modify (attenuate) the 'r' part
• Converted polar to complex
3. Real inverse FFT

This seems to work fine, however, I notice that in the final stage if I do a Complex inverse FFT then the resulting signal is about half the amplitude of what I'm expecting. Why is that?

I have set up a test signal of 10000 samples of a 100MHz Sinewave, however I see this happen at all test frequencies and number of samples.

[ToeCutter]

A complex FFT is two sided- and real frequency component at frequency f0 appears as two peaks on your FFT- one at +f0 and one at -f0. Each component is half the amplitude of the sinusoid. This is probably what you are seeing.

Filtering is usually performed by creating a filter (IIR or FIR) to your required specifications. Your method is a bit unusual in that a given output sample can be affected by a sample that comes after it.

[AlanKnowler]

Thanks ToeCutter, looking at IIR and FIR, I would need Forward and Reverse co-efficients if I used IIR, and FIR co-effiecients if I used FIR. I am at a loss when trying to understand how these parameters can be defined.

Can you/anyone give me direction in where I can find how to arrive at values for these for the equation given in the first post?

Thanks