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T-junction Mircrostrip Line

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tkhan9

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Hi,
I am designing two button antennas attached on the same substrate using a T-junction microstrip line. The antennas are meant to work at 180 degrees out of phase and using another material of certain di-electric constant, the antennas would operate at 360 in phase. The certain material would thus act as a slider on the microstrip line, and user defined of what phase the antennas would operate.
However, are there any equations that would enable me to design the microstrip line efficiently?
Any help would be greatly appreciated.
Thanks in advance.
 

For the T-junction microstrip line, use a wilkinson power divider. The number of stages in wilkinson depend on the bandwidth that you want to achieve. There are lot of papers on realizing a Wilkinson power divider.

But with the wilkinson power divider, you get in-phase outputs (phase difference of zero between the output ports), so you need to use a quadrature hybrid across the outputs to get a phase difference of 180 degrees.

Hope this helps.
-sv
 
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    tkhan9

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Thanks for the reply sv1437,
The design of the antenna is being done by the software CST Microwave Studion, and to achieve a phase difference of 180 degrees, I am using a difference of lamda/2 in the microstrip line. However, to make it a completely lossless line, I need to design the T junctuin in such a way that no signal gets reflected and both the channels receives the same amount of signal.
To do that, I need an equation to compute the width of the T junction line. If you could help me with that, I would really be very grateful to you.
Thanks.
 

What is the frequency range you are planning to implement ? The lamda/2 line can provide phase difference of 180 only for a narrow range of frequencies, the phase of the lamda/2 line increases with frequency. If you are planning to implement for a broad range of frequencies, lamda/2 line does not work.

Since you want equal power across the two channels (equal power division), you should implement T-junction using wilkinson power divider.

If you can tell me what is the frequency range ( f1 to f2) , dielectric constant of the substrate and dielectric thickness, then I can give you the dimensions that you have to use.

Are you connecting a dipole antenna?

-sv
 
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    tkhan9

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The frequency range i will be using is the bluetooth frequency of 2.45 GHz and if possible, the WLAN frequency of 4.5GHz.

For the di-electric material and the thickness, I can let you know tomorrow as I need to discuss with my lab technician of which catagory material he has and of what thickness substrate he can use. But as far as I know, the substrate thickness is about 1.524 mm. The two button antennas would be two mono pole antennas.

Thanks SV for taking trouble to help me out. Really appreciate it. :)
 

Hi tkhan9,

I found an IEEE paper on the same thing that you are doing. The paper is : N. Kaneda, and et al.,"A Broad-Band Planar Quasi-Yagi Antenna," IEEE Trans. Ant. and Propagation, vol. 50, no. 8, Aug. 2002.

-sv
 

Hello,

Maybe you could try with a MoM simulation, for example using a software like **broken link removed**.
 

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