# A Novel Wideband Splitter for a Four-Element Antenna Array
## 4 Achieved Results and Discussion
The measurements were carried out on a calibrated measuring system using a vector network analyzer R&S ZVL6 (VNA) and a personal computer with a general purpose interface bus (GPIB) interface, and the measurement setup is shown in Figure 4. The plot in Figure 5 shows the frequency dependence of the transmission coefficient of segment A, i.e., the transmission line for port 1 and port 2. From this dependence, it can be concluded that the insertion loss within the working frequency band ranges from 0.97 dB to 2.37 dB, while the insertion loss at the center frequency reaches the value of 1.1 dB. Figure 6 shows the frequency dependence of the transmission coefficient of segment B, i.e., the transmission line for port 3 and port 4. From this dependence, it is clear that the insertion loss within the working frequency band ranges from 0.57 dB to 1.47 dB. The insertion loss at the center frequency reaches the value of 0.6 dB. From the presented results it can be concluded that the proposed splitter has an extremely flat transmission response of \(\pm\)0.8 dB within the working frequency band. In Figure 7, the frequency dependence of the reflection coefficients of both segments is presented. Segment A represents the transmission line for port 1 and port 2, and segment B stands for the transmission line for port 3 and port 4. From this dependence, it can be concluded that the impedance difference of port 1 and port 2 from the reference value of \(Z_{0}\) within the working frequency band is between 9% and 20%. The impedance difference at the center frequency for these ports reaches the value of 16%. Moreover, the impedance difference between port 3 and port 4 from the reference value of \(Z_{0}\) within the working frequency band ranges between 14% and 20%. The impedance difference at the center frequency for these ports reaches a value of 17%. Therefore, it can be concluded that the proposed splitter has very good impedance properties within the working frequency band. Figure 4: Measurement setup with power splitter connected to the vector network analyzer. Figure 5: Impact of frequency on the transmission coefficient achieved from the simulation and measurements of the proposed antenna array splitter prototype on segment A (the transmission line for ports 1 and 2). The fractional bandwidth of the prototype can be calculated from the reflection coefficient, which has to be \(\leq\)\(-\)20 dB for both segments of the transmission line. Based on the data presented in the figure, the cut-off frequencies are \(f_{min}\) = 375 MHz and \(f_{max}\) = 923 MHz. Thus, the fractional bandwidth for the center frequency \(f_{c}\) = 650 MHz can be calculated as follows:  
\[B_{frac}\ =\ 100\times\frac{f_{max}-f_{min}}{f_{c}}\ =\ 100\times\frac{923-375}{650}\ =\ 84.3\%. \tag{7}\]  
Figure 8 shows the frequency dependence of the phase error between the segments of the proposed antenna splitter from the simulation as well as the measurements. From this dependence, it follows that the phase error within the working frequency band ranges from 0.14% to 0.64%. The phase error at the center frequency reaches the value of 0.32%. Therefore, based on the achieved results, it can be concluded that the proposed splitter has excellent phase accuracy within the working frequency band. \[V_{f2A}=\frac{V_{f1}\times A}{2\times(Z_{Ca}+0.5\times Z_{f1}+A)}, \tag{2}\]0 Impact of frequency on the transmission coefficient achieved from the simulation and measurements of the proposed antenna array splitter prototype on segment B (the transmission line for ports 3 and 4). \[V_{f2A}=\frac{V_{f1}\times A}{2\times(Z_{Ca}+0.5\times Z_{f1}+A)}, \tag{2}\]1 Impact of frequency on the reflection coefficients of both segments of the proposed antenna array splitter prototype based on experimental measurements. The properties of the proposed splitter were also verified in practical conditions for signals in the 5G NR band n14. Four identical LP UHF FRACARRO LP45 FMINII antennas were connected to the prototype of the splitter to perform the measurements.