# converting inductors and capacitors to microstrip - RF Cafe Forums

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Post subject: converting inductors and capacitors to microstrip

Unread postPosted: Thu Jan 06, 2005 6:03 am

Hello.I need help about microwave office simulation program.I need to draw layout of my circuit and i dont know how to realize the inductors and capacitors with microstrips.For example i used a 10 nH inductor but i could not find which substrate or W, L to use.Any link or formula about this will help me a lot.Thanks....

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Guest

Post subject: Inductor Layout

Unread postPosted: Fri Jan 07, 2005 12:10 pm

Most of the closed form equations for spiral inductor are for inductances with no ground plane influence. The influence of a ground plane will lower the inductance due to field restriction. The equation for a square inductor with no ground plane is:

L=0.85*sqrt(A)*N^(5/3)

A=area of the inductor mm^2

N=number of turns

The total lenght of the line in mm is calculated:

Le=N*[8*Ri+d*(4*N-3)]

N=number of turns

Ri=inner radius of inductor in mm

You can use the equation to get a starting point but since microwave office has a layou toll it may be easier to play around with simulator by adjusting the lenght and width and determining the inductance. The inductance is calculated by:

L=1/(2*PI*F*Xc), where Xc is the reactance of the spiral inductor when terminated to ground. You put this equation in microwave office and optimize for the required inductance while placing limits on how wide and spacing between each turn. If you have an EM simulator ( or you can go online and download the free Sonnet Lite em simulator) you should verify the the design since the linear simulator may not be as accurate.

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Guest

Post subject:

Unread postPosted: Tue Mar 08, 2005 4:16 pm

can we use ADS for reliazation of inductor into microstips?

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Kirt Blattenberger

Post subject:

Unread postPosted: Tue Mar 08, 2005 5:24 pm

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Joined: Sun Aug 03, 2003 2:02 pm

Posts: 308

Location: Erie, PA

Greetings:

I'm a little late to the game, but take a look at this page and see if it helps.

https://www.rfcafe.com/references/electr ... onents.htm

- Kirt Blattenberger :smt024

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T

Post subject:

Unread postPosted: Tue Mar 08, 2005 5:33 pm

Hello,

What is the meaning of the angels (Theta) when calculating the distributed elemenets(Capacitors, inductors)? How does it combines with the implementation of the inductor/capacitor?

Thanks,

-T

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Kirt Blattenberger

Post subject:

Unread postPosted: Tue Mar 08, 2005 11:39 pm

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Joined: Sun Aug 03, 2003 2:02 pm

Posts: 308

Location: Erie, PA

Greetings T:

Theta is the electrical length (360 degrees = one wavelength) of the transmission line at the frequency of interest.

- Kirt Blattenberger :smt024

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Guest

Post subject:

Unread postPosted: Wed Mar 09, 2005 11:20 am

Just one additional comment. Because the value of inductance and capacitance is dependent on the electrical length of the line then the effectiveness of using this type of distributive inductance and capacitance will be band limited. Typically, these types of distributed components are only good for 10 to 15% band.

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T

Post subject:

Unread postPosted: Wed Mar 09, 2005 3:05 pm

What I really don't undersatnd is why these inductors and capacitors are dependent on the wavelength of the transmission line?

- T

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Rod

Post subject:

Unread postPosted: Wed Mar 09, 2005 5:06 pm

If you study the Smith Chart it will make sense to you.

90 degree short = open

91-179 degree short = capacitve

180 degree short = short

_____________________________

90 degree open = short

91-179 degree short = inductive

180 degree short = open

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MICRO

Post subject: MICROSTRIP

Unread postPosted: Thu Apr 21, 2005 3:12 am

I AM A NEW USER ..CAN U TELL ME HOW REPRESENT CAPACITOR/INDUCTOR VIA MICROSTRIP?WHAT SHOULD B ETEH DESIRED LEGTH /WIDTH IN OR TO GET THE DESIRED CAPACITOR/INDUCTOR?

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Guest

Post subject:

Unread postPosted: Thu Apr 21, 2005 9:08 am