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Design of a Bias Tee using conical inductor (Read 4718 times)
shopitham
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india
Design of a Bias Tee using conical inductor
Dec 17th, 2010, 12:44am  
Hai,

 I am designing an bias tee for measuring the capacitance of a varactor diode using VNA.
I have planned to use "conical inductor" for designing the bias tee .
Do we have any special type of capacitor for using in bias tee?
or should i be using only a microstripline?

Pls help me i would be really useful.

Thanks in advance,

Shobi. Smiley Smiley
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rfcooltools.com
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Re: Design of a Bias Tee using conical inductor
Reply #1 - Dec 30th, 2010, 11:09am  
Shopitham,

I have to ask why you would not just use a large resistor to bias the varactor ?

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shopitham
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india
Re: Design of a Bias Tee using conical inductor
Reply #2 - Dec 31st, 2010, 8:54pm  
I am using VNA for  measuring the impedence of varactor diode.
my VNA doesnt have an inbuilt bias tee.  
so i am in need of designing a bias tee.  :)
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Re: Design of a Bias Tee using conical inductor
Reply #3 - Jan 1st, 2011, 11:19am  
Shopitham,

The reason I ask is that the conical inductor or any inductor will give a complex impedance that could obscure the measurement of the capacitance you seek to obtain.  but if you want to go this route remember that a discrete capacitor has leads inside the package which will ultimately give a series capacitance of around 0.5nH.  Without knowing the specifics of frequency and capacitance range your expect to measure little more can be offered as far as guidance.

If I where to do this measurement here is how I would proceed.
Bias the dc of the varactor with a large value resistor and a voltage source, measure the dc voltage at the varactor with a voltage meter AC couple the varactor to the VNA and measure.  Change the voltage and repeat.  

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