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Design >> RF Design >> Design of a Bias Tee using conical inductor
https://designers-guide.org/forum/YaBB.pl?num=1292575445

Message started by shopitham on Dec 17^th, 2010, 12:44am

Title: Design of a Bias Tee using conical inductor
Post by shopitham on Dec 17^th, 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. :) :)

Title: Re: Design of a Bias Tee using conical inductor
Post by rfcooltools.com on Dec 30^th, 2010, 11:09am

Shopitham,

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

http://rfcooltools.com

Title: Re: Design of a Bias Tee using conical inductor
Post by shopitham on Dec 31^st, 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. :)

Title: Re: Design of a Bias Tee using conical inductor
Post by rfcooltools.com on Jan 1^st, 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.

http://rfcooltools.com