Am i right in thinking that the output amplitutde from the NCO is not constant over different frequencies?

Amplitude depends on how you want it to be and is not related to frequency. Check your nco IP mif files for maximum/minimum.

When i sweep the frequency the amplitude is changing though, could it be to do with the dac?

Hard to say. you better give more details about your design from NCO to DAC to the way you see amplitude. Do you use any fft? You can exclude NCO by looking at max/min mif values per each sweep point.

My project is attached. I am not using any FFT. I have checked my amplitude on an osciliscope and also through NIOS to the pc.

I am sorry I can't run any projects at the time being. I suggest the easiest way is to use nios or signaltap(or simulation) after adding this simple piece of code on your sine data: -- get max data process(clear,clk) begin if clear = '1' then temp <= (others => '0'); elsif rising_edge(clk) then if temp < data then temp <= data; end if; end if; end process; you can use nios to clear temp or read its value per each frequency. Remember to make temp and data signed type

Output amplitute from an NCO | Altera Community

25 Replies

Altera_Forum
Honored Contributor
16 years ago
I am going to correct my final data on my pc as a lot easier then trying to correct for it on the FPGA.

Thanks alot for your help in this.
Altera_Forum
Honored Contributor
16 years ago
I think that outputs of DAC have amplitude diffirent with frequences diffirent. Because ouput of DAC forma sin(x)/x.
Altera_Forum
Honored Contributor
16 years ago
Hi,
I have the same problem with stratix2 dsp evaluation board. I built a simple fsk modulator on NCO. The output is 10 kHz for '0' and 15khz for '1'. I use all 14 bits of DAC. The amplitudes differs about 50-100 mVolts. In the simulations everything looks ok. I also try to understand what the problem is.
Altera_Forum
Honored Contributor
16 years ago
In this case you can easily overcome the difference by prescaling both to become equal after DAC(simplest case of equaliser)
Altera_Forum
Honored Contributor
14 years ago
--- Quote Start ---
Hi,
I have the same problem with stratix2 dsp evaluation board. I built a simple fsk modulator on NCO. The output is 10 kHz for '0' and 15khz for '1'. I use all 14 bits of DAC. The amplitudes differs about 50-100 mVolts. In the simulations everything looks ok. I also try to understand what the problem is.
--- Quote End ---

Do You Have the project to share?

Forum Discussion

Output amplitute from an NCO

25 Replies

Recent Discussions

Will serialization factor of 6 in LVDS serdes IP be supported in the future on Agilex5?

System PLL of Agliex5 PCIE example design cannot be locked after configuration

JTAG Chain Broken on Agilex 7-I Dev Kit

Request for Cyclone V Pinout File Information

Cyclone 10 LP's Extended Industrial parts