dipole mutual impedance
My method is below: while dipole_1 is excited, dipole_2 is loaded by a resistance of ZL which value is as large as 1e8_omega to guarantee the open-circuit of dipole_2. So Z21=ZL*I_2/I_1, where I_2 and I_1 is the terminal current obtained by method of moments. Is this method right?
but the result from the above method is differ from that calculated by EMF, though it is similiar to the result by IE3D.
I belive the method from EMF is right ,so why has the difference between these two methods?
thank you very much.
Hi, Wusen: On IE3D, we do not care about the termination at port 2. We just need to calculate the 2-port structure with 2 linearly-independent excitation. We find out the S(i,j) for the 2-port system. The 2-port s-parameters represent all the possible cases you may have. For example, if you want to define the termination at port 2 to be open circuit, you can connect an OPEN object or an R with large vaue at port 2 on MODUA (bundled circuit simulator on IE3D) to simulate what you will have. Anyway, the 2-port s-parameters in IE3D cover all the possible cases for a linear system. It is not only for dipole antennas, but for all the cases. It should be correct because it has been used and checked by some many users in more than 10 years. Regards.
I agree with Jian, that is The two port S-parameters represent all the possible cases. But I do not know clearly how to use the two port S-parameters, for example , how to match the active impedance of one antenna located in a array.
Hi, Antboy: In some sense, an antenna designer needs to design a matching circuit to make the active antenna matched. On the MODUA of IE3D, there is one feature may be of interest to you. Basically, given some 2-port s-parameters over a frequency range, you can find the termination at port 2 to make port 1 matched. Then, the question is how you can find a strucutre with the found 1-port s-parameters for the port 2 to make the port 1 matched. If you are able to realize the 1-port s-parameters for the port 2 termination, you are able to make port 1 matched over a wide frequency range. This is normally very difficult to achieve because the 1-port s-parameters for the port 2 termination will be very strange. Its phase normally increases with frequency. Certainly, you can use resonance to achieve phase increasing with frequency over a frequency range. However, when you can design a 1-port structure with increasing phase over a wide frequency range, you may be able to design a good matching network for the active element already. Regards.
Dear Jian: Thank you for reply.
can you kindly to tell me how to calculate the s-parameter in a two dipoles? In my mom codes, s-parameter is derived from the impedance matrix and i do have no idea how to calculte the s-parameter first?
Hi, Wusen:
If you assume Zc = 50 or you have some individual Zc for each port (Zc1, Zc2), you can do the following:
V1=Z(1,1)*I1+Z(1,2)*I2
V2=Z(2,1)*I1+Z(2,2)*I2
1. If you terminate port 2 with Zc2, you have
Zc2*I2 = V2
From it, you can represent V1, V2 and I2 in terms of I1 or V1, V2, I1 in terms of I2. You can find the ratio values as:
V1/SQRT(Zc1)-I1*SQRT(Zc1)
S(1,1)= -----------------------------------
V1/SQRT(Zc1)+I1*SQRT(Zc1)
V2/SQRT(Zc2)-I2*SQRT(Zc2)
S(2,1)= -----------------------------------
V1/SQRT(Zc1)+I1*SQRT(Zc1)
Similarly, you can get S(1,2) and S(2,2). Certainly, in IE3D, it is a general implementation for N-port structure.
Regards.