## 3 Results
Within this frequency region, the isolation level between the output ports is better than 19.96 dB, the return loss is better than 17.71 dB, and the insertion loss is better than 3 + 0.5 dB. Figure 22c shows the magnitude differences, which are better than 4.4 dB. The phase responses corresponding to the S-parameters are also illustrated in Figure 22d. The multilayer three-way WPD was implemented as shown in Figure 23a,b. It is obvious that the implemented circuit is different from the previous one, since two WPDs are located at both sides of the structure with a common ground plane. Comparisons of the simulated and measured results in terms of the return loss, insertion loss, and isolation level are depicted in Figure 23c. Within the frequency band of 1.5-2 GHz, the return loss was observed as better than 15 dB with an insertion loss of better than 3 + 0.5 dB at each output port. Furthermore, the isolation levels between all output ports were better than 19 dB. Figure 23d,e show the measured magnitude differences and phase responses, respectively. Unwanted differences for the measured results result from the fabrication errors which especially appeared during the combination of two layers. Two layers were combined by using copper tape to transfer the ground plane into the upper/down plane. Because of the small circuit size and the laboratory conditions, two circuit boards could not be combined by using screws. Figure 21: (**a**) Comparison of the measured and simulated results of the WPDs having meandered transmission lines for an 8-way WPD; (**b**) magnitude differences of S-parameters; and (**c**) phase responses. Figure 23: Meandered-transmission-line-based multilayer WPDs having a common ground plane: (**a**) front view, (**b**) back view. (**c**) Measured and simulated results. (**d**) Magnitude differences of S-parameters, and (**e**) phase responses. Figure 22: (**a**) Photograph of the meandered transmission lines based on two three-way WPDs. (**b**) Measured and simulated S-parameters, (**c**) magnitude differences of S-parameters, and (**d**) phase responses. A meandered-transmission-line-based multilayer five-way WPD was manufactured and successfully tested. Photographs of the front and back views of the fabricated circuits are shown in Figure 24a,b, respectively. The measured and simulated return and insertion losses of the proposed five-way power divider are compared in Figure 24c, with an acceptable agreement. The measured and simulated isolation levels between the output ports are also depicted in Figure 24d. It is clear that the proposed multilayer 5-way WPD can be used for different communication systems. Within the frequency band of 1.5-2 GHz, the return loss, insertion loss, and isolation levels are better than 16.52, 3 + 0.5, and 14.47 dB, respectively. The differences between the measured and simulated responses resulted from the fabrication errors and especially from the layer-combining process. Magnitude differences between the insertion losses and the phase responses are shown in Figure 24e,f, respectively. Table 2 summarizes and compares the measurements of the proposed designs with the work published in the literature. The proposed configurations in this work introduce WPDs with new input/output configurations that may be used in front of antenna arrays to  
Figure 24: Meandered-transmission-line-based multilayer 5-way WPD: (**a**) front view and (**b**) back view. (**c**) Measured and simulated return and insertion losses and (**d**) isolation levels. (**e**) Magnitude differences of S-parameters and (**f**) phase responses. be used for different personal and mobile communication systems. For this purpose, WPDs based on single- and dual-layer slow-wave structures providing equal power division have been introduced for the first time in this paper. The proposed circuits in this work also have promising circuit sizes.