E-T waveguide power divider

This is a 2-way power divider I made, which is used in a broadband feed net of a horn antenna array. Firstly, a E-T junction (figure 1a) can equal to a transmission line model like figure 1b.The junction is inductive.Here we assume that the impedance of L1 is Z0. So the S11 of this structure is not very good. For a perfect power divider, the impedance of L2 and L3 must be 2Z0, at the same time, the junction must not be inductive nor capacitive.

Figure 1 normal E-T junction

For the impedance, we can reduce the height of the waveguide to increase the impedance, while we can add a step in the junction which is capacitive and it can neutralize the inductance. So the final structure of the E-T junction is like figure 2. Figure 3 shows the S11 of this structure, the cutoff frequency of the waveguide is about 10.5GHz.

Figure 2 broadband E-T junction

Figure 3 the S11 of the structure

Now the impedance of L2 and L3 is 2Z0. We can use the impedance conversion method to convert the impedance to Z0. In the figure 4, I use Chebyshev impedance conversion method. The length of each impedance transformation segment is λ/4. The S11 of this structure shown in figure 5.

Figure 4 2-way power divider with Chebyshev impedance conversion

Figure 5 the S11 of power divider with Chebyshev impedance conversion