adaptive filter FPGA

thanks for looking and please help me.

I have a 16 bit ADC sampling at 50Mhz. I take only 10 MSB and display i in my video 1024 x 768 as an output to check the signal. I see continuous line displayed in my monitor which still toggle within 1 or pixels. My question is, do I need a adaptive filter to really smooth th line in only 1 pixel wide? To make my question clear, for exampl whenever it's supposed to be a horizontal line, it has noise random pixel wide in y. Is this situation, how can I smooth the dat efficiently? I used moving average to smooth the data but every pixel i important, my moving average will give me a small wave along a straigh line plus curving the edge.

The input from ADC is dc coupled which accept level of dc voltag continuously. I'm really doubt about FIR filter and adaptive filter an can somebody tell me is this should be done in adaptive filter? I trie the DA fir from xilinx spartan 3 but it distort the signal, is that mea my cut off frequency is too low? And i use 10bit as input of adaptiv filter, should I should all 16 bit as input?

Reply to
cutemonster
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Nobody will tell you what you need unless you explain what you are trying to do. What is your application? If you are measuring DC why are you sampling at 50 MHz?

/Mikhail

Reply to
MM

to

sampling

Hi, thanks for the reply. I'm converting a stroke signal to raster signal There are actually 2 adc. one for x channel and the other one for channel. Imagine like a xy graph, depends on the voltage level of eac channel, it tells where to draw the pixels. So, for 10 bit, it can displa

1024 x 768 resolution. The signal runs at around 10mhz. I don't know if make my question clear enough, please let me know. I really appreciat it.
Reply to
cutemonster

So you want to display a stroke signal on monitor? Why you need to sample the X? Is it time dimension? Is it a constant ramping, or ramping with retrace, or random?

Reply to
Marlboro

I have to sample x and y because it doesn't work like raster signal. It' voltage varies in time. There is another signal input called Unblank(TTL). It turn on and off of XY signal.

Reply to
cutemonster

Thanks for the info, Lakkos. There are similar projects. However, the transfer the logics into fpga instead of digitizing the analog x and inputs. Dealing with analog signal really give me a headache.

thanks again.

Reply to
cutemonster

Have you tried to lock the sampling clocks to the unblank?

Reply to
Marlboro

It's

Unblank(TTL).

No, I don't understand how to lock it with sampling clock. Can you pleas explain?

thanks

Reply to
cutemonster

Locking the clock to the unblank meaning that their phase relation is fixed. For some reason I can't escape from the time dimension :) If you just sample for 1 frame then probably you don't need to do locking. Do you sample just 1 image then display it continuously on the raster?

If you capture it as live video or multiple frames, then how can you tell which pixels belong to frame n, which belong to frames n+1, n

+2,...

Regards,

Reply to
Marlboro

constant

signal.

please

Yes, I tried synchronous and asynchronously to Unblank signal. There ar two problems. The first one is the noise itself with the stroke signa and the second one is the stroke signal being drawn at the second tim doesn't being drawn at the exact position. It's like one pixel togglin between frames.

Do you know which kind of filter fit the best in this situation?

thanks for you suggestion

Reply to
cutemonster

Sounds like you capture it as live video or multiple frames. In such case you would need to synchronize or lock the clock to a reference, the unblank may be? Having no idea what the unblank looks like so I can't tell how to do it, how often does the unblank recycling?

Having a good synchronized clock with low jitter is, IMHO, much easier than doing the filter to minimize the artifact of pixels toggling positions between frames

For the spatial noise, If I was you I would try a high order analog filter infront of the A2D first, before doing any digital filtering

Regards,

Reply to
Marlboro

are

signal

toggling

thanks for the suggestion. For analog filtering, all I can do now i putting a circuit in breadboard. The problem is that it's a couple inche away from ADC. For digital filtering, are they all very similar? I mean there are many type of digital filtering and I'm confused which one should use. Are they specifically work for certain application?

thanks,

Reply to
cutemonster

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