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VHDL implementation of Digital IF in WiMAX

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missbirdie

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Hello
I was wondering if i want to implement the Digital up converter DUC & the Digital down converter DDC of WiMAX shown in figure, what's the values of the clock for the nco & FIR filters shall i consider in the VHDL implementation ???
Shall i consider the nyquist rate too ?? if yes what will be the nco output frequency if the intermediate frequency needed is 91.392 MHz ??
 

I basically don't understand your question, cause the diagram is showing Fs values. Fs actually is the sampling clock frequency used at each stage. The signal bandwidth and NCO frequency in constrast isn't shown in the diagram.
 

so if these are the sampling frequencies.. should the output frequency from the NCO be at least half of 91.392 MHz ?? And do u mean that the clock frequency is the sampling frequency ?? what about nyquist rate ??
 

I'm not familiar with Wimax. Generally, the NCO output frequency can be fs/4 at maximum to generate quadrature components. Also Nyquist rate limitation results from Fs = 11.4 MHz for the signal bandwith.
 

I don't read this from the literature. Can you tell where did you see this statement?
Usually digital quadrature modulators are operating at fs/4 or fs/8 carier.
 

I understand from AN421, that the IF carrier frequency is actually 22.85MHz, as I guessed initially.
 

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