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How Carrier and Code NCO generates new frequency and phase?

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Pinks2092

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Hello,

I have a question that how the output coming out of PLL or DLL loop filter is utilised by the NCO to generate new frequency using the look-up table.
I have read it in books that NCO has a phase accumulator which coverts the output from the loop filter to some bits, and based on these bits we see the look-up table and find the corresponding frequency and phase value for these bits. And based on this frequency and phase the NCO would generate Sinusoid.
I fail to understand here that how does the phase accumulator converts the output of the loop filter to bits(1s and 0s). I need to know this because I have to use this NCO in a MATLAB program.

Thanks,
Priyanka
 

In a typical NCO design, the phase increment is a multi bit frequency control word rather than a single bit stream. See https://en.wikipedia.org/wiki/Numerically_controlled_oscillator

Seems like you are asking about a special NCO design with fractional (< 1) single bit phase increment.

The relation Fout = Fclock*ΔF/2^n is valid for it as well, ΔF being the bit density.
 
Thanks a lot for your answer.

What is frequency control word? I am implementing Galileo Software receiver and in its tracking part we have an error signal coming out of PLL/DLL loop filters. This error signal which is in its decimal representation, is used as the input to the carrier/code NCO. Then how this error signal can be a multi bit Frequency control word?
 

Decimal representation means it’s just a mathematical value.. it’s range goes from let’s say -0.5 to 1.5.
 

This error signal which is in its decimal representation, is used as the input to the carrier/code NCO.
Click to expand...
What do you mean with decimal representation in this regard? What's the range of the loop filter output?

- - - Updated - - -

The "mathematical value" is just an abstraction of a real signal.

What is the real signal? The context suggests a digital signal (otherwise you need an ADC to convert it), but what's the number format?
 

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