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balanced front-end (Read 2491 times)

aaron_do

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balanced front-end
Jun 16^th, 2008, 2:04am

Hi all,

just wondering, how necessary is it to have a fully differential front-end? I'm designing for the 802.15.4 standard where interference requirements are pretty relaxed. I'm not using direct-conversion either, so DC-offset is not a major concern. I was thinking i could save a lot of power by have a single-balanced front-end (up to the output of the mixer). Any thoughts? What parameter should I look at? IIP2?

thanks,
Aaron

there is no energy in matter other than that received from the environment - Nikola Tesla

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Stefan

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Re: balanced front-end
Reply #1 - Jun 16^th, 2008, 3:08am

Yes, IIP2 will be a major concern.
You should also check for any self-mixing issues like LO feedthrough (LO Port to RF Port) or isolation requirements from the duplexer (I don't have the standard at hand...). If you're using a low IF or heterodyn structure those might only be critical if you're also closefisted with your filters ...

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aaron_do Senior Fellow Offline Posts: 1398	Re: balanced front-end Reply #2 - Jun 16^th, 2008, 6:35am I was thinking that a single-balanced mixer would be able to attenuate LO feedthrough just as well as a double balanced. i.e. balance the LO but not the RF. Also by balancing the LO i can get my IF+ and IF-... cheers, Aaron
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