Re: [linrad] Mixer design - comments please

[Alex Crow <acrow@xxxxxxxxxxxxxxxx>]

On Tuesday 08 July 2003 3:13 pm, Edson Pereira wrote:
> Hi Bob,
>
> I understand the need for square levels for the multiplexer. For some
> reason I thought that the AD9852 already had a digital I/Q output. I
> reread the datasheet and found that the chip only provides a comparator.
>
> -- Edson
>

Why they didn't put in two comparators I'm not sure - it seems silly to have 
only one. I guess it's pretty easy to do IQ in DDS though since all you have 
to do is shift your address forward in the sine lookup table a bit.

Well, I'm nearly finalised on the mixer design, and I think I'm going to reuse 
most of someone else's board for the DDS. I've also ordered one of those 
hugely expensive oscillators... I just have to wait 3 months for that so for 
now it's:

a) 50MHz Xtal osc and use the internal PLL to get the 200MHz ref
or b) 50MHz Xtal osc and some conventional transistor doublers.

Cheers

Alex


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