Hi
I would like to know what are the expected frequency components of a power signal ?
Following the book PAA, the device clock frequency should be present in the frequency spectrum of the signal.
I ask, because during measurments in the SAKURA-G board at the amplifier output, the signals has a component at 48 MHz, that is expected, but have another component, even stronger that the leader of about 4-5 MHz.
I verified it with two different algorithms running on the FPGA and the result was the same.
What is the reason of the existence of this frequency component ?
Why is stronger that the device clock frequency ?
Sorry on the slow response here! Apparently my attempt to allow posts without moderation failed, and as a result I wasn’t notified about pending posts… oops…
The strong signal component can come from many sources. It may be because of the algorithm itself - i.e. if the system was doing something every 10 clock cycles with a large current draw, you might get such a signal. It’s also possible the signal comes from other sources due to noise - the USB cable, etc. If you hold the FPGA in reset does the signal disappear?
ask, because during measurments in the SAKURA-G board at the amplifier output, the signals has a component at 48 MHz, that is expected, but have another component, even stronger that the leader of about 4-5 MHz.
I verified it with two different algorithms running on the FPGA and the result was the same.
What is the reason of the existence of this frequency component ?
Not sure off-hand. If the input clock is divided by 10 somewhere that could explain that signal, or if another oscillator (such as inside the USB interface chip) is coupling into your measurements it’s also possible. You’ll have to do some experiments by ‘eliminating’ sources, which might not be possible without using an external scope/spectrum analyzer. If I get some time I’ll try to see if I see such an spike on my SAKURA-G here!
I ask, because during measurments in the SAKURA-G board at the amplifier output, the signals has a component at 48 MHz, that is expected, but have another component, even stronger that the leader of about 4-5 MHz.