Does the PCGU1000 have a Diode for creating the noise up to 25MHz or how does it create the signal?
Marcus
The PCGU1000 does not create “noise”, but rather a well defined output waveform according to the available selections and if desired user defined wave library files…
It is a DDS ([color=#0040BF]Direct Digital Synthesis[/color]) function generator. [color=#0040BF]This thread contains good information as to how it works[/color]…
Does this mean that the noise function just plays a recorded noise signal or does it create the noise up to 25MHz by own hardware means?
How does the noise modus of the PCGU work?
Marcus
[quote]Does this mean that the noise function just plays a recorded noise signal or does it create the noise up to 25MHz by own hardware means?[/quote]The noise is generated by the hardware means.
[quote]How does the noise modus of the PCGU work?[/quote]First the PC software calculates 8192 samples of Gaussian noise. These samples are uploaded to the function generator’s waveform RAM.
The content of the RAM is then output in random order.
For normal waveform output:
The look-up table for one cycle of the waveform is stored to the RAM of 8192 bytes
A constant value, the phase increment, is added to the address counter with each 50MHz clock cycle.
For the noise output:
The RAM of 8192 bytes is filled with Gaussian distributed values.
A random value, the phase increment, is added to the address counter with each 50MHz clock cycle.
How is the random number generate which chooses the increment?
Is it a Pseudo or physical random generator? Thats the main point of interst for me in this discussion.
Marcus
[quote]Is it a Pseudo or physical random generator?[/quote]It is Pseudo.
In the PCGU1000 there is used a 38-bit linear feedback shift register (LFSR) for the random number generation.
There are four feedback tabs used.
The length of the repetition loop is 2^38-1 clock pulses.
Running at 50 MHz, such a counter repeats after 1.5 hours.
Here you’ll find two documents as reference:
pdfserv.maxim-ic.com/en/an/AN1743.pdf
xilinx.com/support/documenta … app052.pdf