On 12/12/2010 02:31 AM, jimlux wrote:
Don Latham wrote:
Hi Luis:I, too, am curious. But I haven't opened it yet. I suspect
something like an FPGA feeding a fast a/d somewhere in the 50-70 MHz
range. That is, a decomposition.
There may be a synthesized LO and mixer to get to the 50 MHz.
The info on the website says or used to say something about an sdr
modified to act as a spectrum analyzer.
One of the things I like about the device that played a part in my
purchase is the availability of a 10 MHz reference input. as a good
time-nut that shows some serious engineering attention to accuracy.
Don
I'm going to guess much simpler inside.. Essentially a programmable
receiver like the Icom PCR1000, but with better bandwidth, running into
a pair of 192kHz ADCs, for which easy USB interfacing is available.
The question is really what does the 4GHz LO in the front look like?
It's almost certainly some sort of VCO PLL scheme, probably with
multiple VCOs. But, do they use a DDS? Probably not... They probably
have a fast PLL that settles quickly so they step through in 100 kHz
steps or so.
Two VCOs covering 1-2.2 GHz could through mixing and selecting between
sum and difference output filters (i.e. lowpass and highpass) cover that
without too much difficulty. Except for the highest end, there is a
degree of freedom in setting the oscillators to their individual
frequency which naturally could be used to avoid "bad" frequencies to
leak into the IF for instance.
Cheers,
Magnsu
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