A good write-up, thanks Sulvain.
I forgot all about how they functioned. I worked on an SDR project a million years ago (before SDR was a thing) that did this. I just used it and didn't realize that it was a super-het, and then I forgot all about it once I started using USRPs. Thanks. ________________________________ From: Sylvain Munaut <246...@gmail.com> Sent: Wednesday, June 5, 2019 11:31 AM To: Jason Matusiak Cc: Robin Coxe; Ettus Mail List Subject: Re: [USRP-users] offset tuning on the TwinRX On Wed, Jun 5, 2019 at 4:41 PM Jason Matusiak via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: OK, thanks everyone. I guess I have some superhet reading up to do 🙂. In a nutshell, it's _always_ using LO offset :) The RF path always brings the signal to some IF (150 MHz IIRC), then the DDC blocks do the shift to baseband DC digitally. So it's pretty much like if you had set the lo_offset = 150 MHz. The finer points are : - It's not doing I/Q sampling, it uses one ADC for one channel and the other for the second one. - It's actually using band-pass sampling since the IF is higer than fs / 2. But of course that means the hardware DDC blocks in the fpga are used already and that's why you can't (and there would be no point anyway) to apply some second level of lo_offset. Cheers, Sylvain
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