What is the NCO and how to realize it ?

[springf2000]

what is the NCO

dear sir:
what is the NCO and how to realize it,any more i want to know how to realize the digital upconverter!

 

[Renjith]

what is the NCO

NCO is a basic block which is used in digital communication where u want to upconvert or downconvert ur signal for Receptin and transmission.
they r basically a sine,cosine wave generators.
the output frequencies of this block can be used to mix with ur incoming signal for frequency translation.
The NCO's output frequency is controlled byan input count/integer value. The architecture inside an NCO basically contains an Adder(Accumulator) and a LUT ROM (which stores the values of Sine and Cos). Depending on the input count that u send to this block, they will pick values from the ROM, which inturn is ur Sine/Cosine wave.
For Upconverting ur input signal, u can Mix(multiply) , ur incoming signal with this NCO freq.
If ur Signal freq is Fs and ur NCO freq is Fx, then the output frequency of ur mixer will have 2 values,(Fs + Fx) and (Fs - Fx), u can use a filter to generate ur upconverted signal at the ouput