The spectrum of the DW3000

Hi, We tested the spectrum of the DW3000, and we see that there’s a spike at the central frequency. Does anyone know what causes it?
In addition, the board of DW3000 is designed by ourselves without using DWM3000 module.

Hi , Could you reduce the sweeptime? eg 1ms?

We use Continues Frame mode in (decaranging) to measure the TX power. We have also CF example code you could use to test the power.

Leo

Hi Leo,

We have already use Continues Frame mode and set the sweeptime to 1ms. As in the example, we set the CONT_FRAME_PERIOD to 249600.
But We don’t know why there’s a spike in marker2, and it’s up to 10dB.

Thanks for your reply.

I think Leo is referencing the sweep time of your spectrum analyzer. It appears to be set for a sweep time of 20ms.

Hi, We configured it to be 1ms. but there is still no improvement.

Hi
What spectrum analyser do you have?
Could you set spectrum analyser to: -
Center frequency Ch9=8Ghz or CH5=6.4896 Ghz
BW=500Mhz
Span = 1 GHz,
Sweep time* = 1 s,
VBW = RBW = 1 MHz,
Detector = RMS

Regards
Leo

Hi Leo,
We configured the spectrometer as you said, and the spike has disappeared and the waveform is smooth. But we found a strange phenomenon in the real time spectrum, there will always be a narrowband signal at the center frequency. Is this a normal situation? Why does this narrowband signal exist?

Thanks for your reply.



DW3000-Real-time spectrum_20210430153753

We haven’t seen this in conducted or over the air measurements.
Maybe you’re configuring the device incorrectly in your firmwar or it might be your layout as you might be getting radiation from somewhere on the board other than the antenna.

/L

Hi Leo,
We also tested DWM3000 module and then the result is the same. We tested the conducte signal by removing the antenna on the DWM3000. And then we still find the narrowband signal at the center frequency.
So we think it probably has nothing to do with the hardware. But we couldn’t find a problem in the firmware. The firmware is the reference ex_04b_cont_frame example.
Do you know what firmware configuration will cause this problem?

Thanks for your reply.