UPSAMPLING BLOCK Problem

Question

Hi guys,

has anyone experiences with the DSP Builder "UPSAMPLING BLOCK" ??? I want to use it but there is one big Problem: The Up Sampling block increases the output sample rate from the input sample rate. The output data is sampled every N cycles where N is equal to the up sampling rate. The output holds this value for 1 cycle, then for the next n-1 cycles the output is zero.

Compared to the DOWNSAMPLING BLOCK: The Down Sampling block decreases the output sample rate from the input sample rate. The output data is sampled at every N-th cycle where N is the down sampling rate. The output data is then held constant for the next n input cycles.

In my design I have to use this Up Sampling block but with the option to hold the output data constant.

Does anyone know how to solve this problem or how to built a selfmade Up Sampling block, please help.

T-4444

altera_forum · Answer

This is just what "upsampling" does. It pads zeros to increase the sampling rate. If you want to reconstruct the samples, a lowpass filter or bandpass filter is needed.

altera_forum · Answer

No, for my design I need an Up Sampling block with the feature I wrote. I know other tools where you have the option to say "Copy Samples". If I use for example a 5x Up Sampling block, the first cycle is high and the following four are zero, but I need the follwowing cycles as high as the first.

Got anyone an idea how to get this work?

altera_forum · Answer

What you want then is not upsampling but "sample and hold". You don't need dsp builder to do that for you. All you need is an output sampling rate 5 times the input sampling rate. Then for every input sample produce 5 output samples that equal current input using basic logic.

True upsampling is to interpolate the input. One method is to insert zeros then low pass filter to remove freq copies introduced by zero insertion.

altera_forum · Answer

Yes you got it KAZ. but how to do this? I'm still beginner and need some extra help.

altera_forum · Answer

try this:

The important thing is to keep data coming in at reduced rate

signal count :integer range 0 to 4:= 0;

in a clked process

if(count = 4) then

count <= 0;

enable <= '1';

else

count <= count + 1;

enable <= '0';

endif;

if(enable = '1') then

data_out <= data_in;

endif;

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UPSAMPLING BLOCK Problem

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