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hawsona
Joined: 22 Jan 2002
Posts: 16
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 29 May 2003 4:27 large signal impedance match,help!!! |
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Now I use A(at)gilent A(at)DS to design Gilbert Upconversion Mixer,but because I use the design guide of A(at)ds,but the guide is use small signal to test the input impedance. So the LO port impedance is not accurate.
Can anyone tell me how I can test the impedance under large signal condition accurately?
Or give me some reference.Thanx very much!
My email is : carmine_rene(at)hotmail.com
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arash_ee
Joined: 27 Apr 2003
Posts: 0
Location: Iran
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| 31 May 2003 21:21 |
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hi
if you need any information about matching impedance network at large signal you can download this pdf .
its address is:
http://rfwireless.rell.com/pdfs/AN_721_D.pdf
I find another good article for you:
see this
http://www.sandiego.edu/~ekim/e194rfs01/zmatch.doc
If you need Pi network impedance matching you can compute your network online at this site:
http://www.raltron.com/cust/tools/network_empedance_matching.asp
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nandopg
Joined: 26 Apr 2001
Posts: 248
Helped: 5
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| 31 May 2003 23:06 Large Signal Input Impedance using Spice |
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Find through the link bellow a reference that can solve your problem,
http://www.rfmd.com/databooks/db97/Ta0041.pdf
NandoPG
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BigBoss
Joined: 17 Nov 2001
Posts: 931
Helped: 47
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| 31 May 2003 23:44 |
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Why you need LO port input impedance of Gilbert Cell Mixer ?
Under the high level signal condition , input impedance of a Gilbert cell mixer varies by LO signal amplitude. Regarding to saturation status of bipolar transistors ( varies proportional to tanh ) input impedance will be depended on instantinous signal amplitude therefore finding a simple impedance level is almost impossible. You drive with a certain level to saturate them. That's it..
In fact LO amplitude should be high as possible high to avoid transient noise. For a simple Gilbert cell structure this level must be over 300mVpp.
But if you use more complicated device , I don't know..
In fact to drive Gilbert cell mixer , a buffer amplifier should be used to prevent LO frequency pulling..This is very important. In this case input impedance is not very important.
Regards ,
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alongsh
Joined: 29 May 2003
Posts: 7
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| 02 Jun 2003 3:00 |
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the buffer amplifier can easy match to
50ohm
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