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Digital Radio (GC Products) Forum
NCO in GC5016
I'd like to know the highest freqency of NCO if GC5016 works at 160MPs. Whether the frequency of NCO can get up to one half of the input clock of GC5016?
The GC5016 is a full complex NCO for each channel. The tuning range is +/- Fck/2. The cmd5016 tool, can be used for real inputs to tune to the 2nd nyquist zone image, instead of a folded first nyquist zone frequency. The GC5016 usable tuning range is Fck/2 - 1/2 signal Bandwidth - system transition bandwidth.
So for a 1Mhz band signal, with a .25Mhz system transition bandwidth, the range at 160Msps is 80 - .5 - .25 = +/- 79.25Mhz.
There is a mode in the GC5016, to use a double rate (both splitIQ pairs) with an odd and even signal. In this case the apparent NCO rate is 2x the range. So in this case,a 320Msps ADC, is split into 160Mhz even, and odd busses. Each Mixer A-B (splitIQ pair), and Mixer C-D(splitIQ pair) is processing the pair of samples.
The GC5016 SEK - with GC Studio software can be used to digitally test these configurations.
The TSW4100 - digital repeater can be used with the 14bit ADC, and 16bit DAC to do IF frequency translation, to test the analog IF to digital to digital to analog IF repeater.
The GC6016 can support higher sample rate ADCs than the GC5016.
In my application, I have four real signals from ADC, bandwidth is 40MHz, center frequency is 65MHz, I'd like to tune them to baseband in each GC5016 channels. The undersampling clock of ADC is 65*4/3=87MHz, I want to use the images in first Nyquist zone and tune them to baseband, the clock of GC5016 is 87MHz. So I set the NCO frequency as follows:
NCO frequency=87/2-20-3(transition bandwidth)=-20.5MHz. I wonder is that OK?
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