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From: | David Bengtson |
Subject: | Re: [Discuss-gnuradio] Suggestions regarding a frequency reference |
Date: | Tue, 14 Jun 2005 23:10:18 -0400 |
User-agent: | Mozilla Thunderbird 1.0.2 (Windows/20050317) |
Matt Ettus wrote:
Sounds like a nice summer project :-) 40 MHz seems to be a standard TCXO frequency, based on a quick perusal of the Digikey catalog. It would be a single part to add to the board. If this is used as a reference oscillator for a PLL, then you might be better off from a performance point of view by adding the part and getting a clean reference. Your spurious emission's specification's will thank you.David P. Reed wrote:In interfacing a new 5 GHz up/downconverter to the USRP (my summer project), I find that I need a 40 MHz frequency reference to drive a PLL in the chip. My first prototype will interface using the Basic Rx/Tx daughterboards, and it occurs to me that I can probably use one of the DAC clocks for that. Should this work? Any other suggestions (at this stage I'd prefer to use an existing, programmable source on the USRP, rather than another chip and crystal)?Does it need to be 40 MHz? 40 is going to be hard to produce cleanly on the board. 128 divided by any integer is much easier. Matt _______________________________________________ Discuss-gnuradio mailing list address@hidden http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Digitally, you could multiply the 128 by 5 to get 640 MHz, and then divide by 16 to get 40 MHz, but I don't think you could do this in the FPGA.
Dave
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