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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] Testing crystal accuracy |
Date: | Wed, 13 Jan 2016 07:12:13 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |
Hi Jason, I shouldn't have hit the send button yesterday and went to bed right after. Had a night of bad sleep; I realized my formulas only applied to the case of real valued signals. Your dongles won't be giving you cosines in complex baseband for a signal they see at ; they will give you complex sinusoids and , respectively. To be complete, there'd also be a phase offset, so it'd be , and . Now, multiplication of these really just is addition of the exponents, so which means you'll only see the "sum frequency". That's why you'd use the "multiply conjugate" block instead: Regarding your splitter: Usually, splitters don't introduce nonlinearities, so you should be fine. Best regards, Marcus On 12.01.2016 19:47, Jason Matusiak
wrote:
Thanks Marcus, that helps a lot. Since I have to multiply the resulting offsets against each other, that means I will need to run a splitter from my sig-gen to the two dongles. Is there any concern that non-linearities in the two legs of the splitter would effect the results? Also, what should I do about the transition width on the LPF? Thanks for the thorough math explanation, that was a good lesson in what is going on. |
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