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mydreamhouse Junior Member Offline Posts: 23	abot superheterodyne receiver Mar 15^th, 2009, 8:19am i am designing a superheterodyne receiver, but i wonder my IF VGA. (first IF :180MHZ), i found if IF VGA has third order intermodulation, and it will mix with third order distortion of LO, which will locate in bands,is this a serious problem?, who can give me some advice or refernces?
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mydreamhouse Junior Member Offline Posts: 23	Re: abot superheterodyne receiver Reply #1 - Mar 16^th, 2009, 10:05am who can give me some advice
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pancho_hideboo

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Re: about superheterodyne receiver
Reply #2 - Mar 16^th, 2009, 10:11am

mydreamhouse wrote on Mar 15^th, 2009, 8:19am:

i found if IF VGA has third order intermodulation, and it will mix with third order distortion of LO, which will locate in bands,is this a serious problem?

???????????????
Maybe there is no one who can understand a meaning of your sentences.

mydreamhouse wrote on Mar 16^th, 2009, 10:05am:

who can give me some advice

Again If you want someone to answer your post,
you have to describe your questions regarding situation and condition in detail and correctly using industrial standard terminologies.

This is very very true for all your posts too.
http://www.designers-guide.org/Forum/YaBB.pl?num=1235494642/0#0
http://www.designers-guide.org/Forum/YaBB.pl?num=1229879167/0#0
http://www.designers-guide.org/Forum/YaBB.pl?num=1235493325/0#0
http://www.designers-guide.org/Forum/YaBB.pl?num=1236016393/0#0

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« Last Edit: Mar 17^th, 2009, 6:28am by pancho_hideboo »

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http://www7.plala.or.jp/ungeromeppa/flash/kita.html
http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related

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mydreamhouse

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Re: abot superheterodyne receiver
Reply #3 - Mar 18^th, 2009, 11:01am

thanks.
what i worry about is the third order distortion of IF signal mixes that of the second LO. for instance, the IF is 200MHZ, after external LC BPF or SAW filter, an on chip IF VGA is following. due to the third order intermodulation of IF VGA, third order distortion will be appears before the second mixer. so 3IF-3LO will be in band(dual conversion superheterodyne receiver),which will degrade the sensitivity.

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pancho_hideboo

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Re: about superheterodyne receiver
Reply #4 - Mar 18^th, 2009, 5:24pm

mydreamhouse wrote on Mar 18^th, 2009, 11:01am:

what i worry about is the third order distortion of �IF signal mixes that of the second LO.
for instance, the IF is 200MHZ, after external LC BPF or SAW filter, an on chip IF VGA is following. �
due to the third order intermodulation of IF VGA, �third order distortion will be appears before the second mixer.
so 3IF-3LO will be in band(dual conversion superheterodyne receiver),which will degrade the sensitivity.

Still there is no one who can understand a meaning of your sentences.

I can't know your system is double super heterodyne until now.

And third order harmonic distortion is different from distortion due to third order intermodulation.
Do you understand third order intermodulation correctly �?

Again If you want someone to answer your post,
you have to describe your questions regarding situation and condition in detail and correctly using industrial standard terminologies.

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Kita━━━━━━(ﾟ∀ﾟ)━━━━━━ !!!!!
http://www7.plala.or.jp/ungeromeppa/flash/kita.html
http://www.youtube.com/watch?v=mjIxGh55bMM&feature=related

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: abot superheterodyne receiver Reply #5 - Mar 18^th, 2009, 10:25pm Suggest: Post a block diagram of your system and some details of the frequencies, and other numeric specifics of what you are doing.
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