**3.2 Phase shifter**

technique is often used, and the scattering matrix calculation is represented in [22].

We can see that the power from input port is split into two output ports without power loss on transmission line, there is no reflection wave from output ports and output ports are completely isolated. With advantages of WPD over T-junction dividers, the WPD is utilized as the power divider for feed network of antenna array. In [22], professor Pozar introduced the N-way WPD (**Figure 7**) in which the transmission line has impedance depending on the number of output ports. This circuit can be matched at all ports, with isolation between all ports. The drawback of this structure is to use crossovers for the resistors for *N* ≥3, which makes fabrication difficult in planar form. The WPD is arranged in cascade structure for low loss and better isolation, shown in **Figure 8**. Two-way WPD is connected together by 50 Ω transmission

2 6 4

*Advanced Radio Frequency Antennas for Modern Communication and Medical Systems*

0 *j j j* 0 0 *j* 0 0 3 7

<sup>5</sup> (4)

*<sup>S</sup>* <sup>¼</sup> �<sup>1</sup> ffiffi 2 p

Finally, the scattering matrix of WPD is:

**Figure 7.**

**Figure 8.**

**104**

*An N-way, equal-split Wilkinson power divider [22].*

*The eight-way equal-split Wilkinson power divider [23].*
