# Quasi-Yagi Slotted Array Antenna with Fan-Beam Characteristics for 28 GHz 5G Mobile Terminals
## 3 Experimental Results  
Figure 17 shows the fabricated prototypes of the proposed \(1\times 8\) array antenna. Figure 17a shows a fabricated array antenna with a \(0^{\circ}\) beam steering angle. Figure 17b shows a fabricated antenna with a fixed beam steering angle. Fixed microstrip line delays in the feeding network are employed to achieve a beam steering angle of \(-30^{\circ}\). The bottom sides of each case are the same as shown in Figure 17c. Figure 16: Performance comparison for different excitation types: (**a**) modified structure with a lumped port, (**b**) modified structure with a connector, (**c**) simulated reflection coefficients, and (**d**) simulated radiation patterns at 28 GHz. Figure 17: Photographs of fabricated antennas: (**a**) top side of the \(1\times 8\) array antenna with a \(0^{\circ}\) beam steering angle, (**b**) top side of the \(1\times 8\) array antenna with a fixed beam steering angle, and (**c**) bottom side of the \(1\times 8\) array antenna. The measurement setup in an anechoic chamber is shown in Figure 18a. The proposed antenna is located on the jig and it is rotating during the measurement. The measurement result is inaccurate between 90\({}^{\circ}\) and 270\({}^{\circ}\) due to the influence of the jig and other structures. Therefore, we measured the radiation patterns in the \(yz\) plane only between +90\({}^{\circ}\) and \(-90^{\circ}\) as shown in Figure 18b. However, the radiation pattern in the \(xz\) plane was measured between +150\({}^{\circ}\) and \(-150^{\circ}\) to verify the fan-beam performance as shown in Figure 18c. Figure 19a shows the measured and simulated S\({}_{11}\) with a connector and feeding networks, and there exists a reasonable agreement between the results. Discrepancies between the simulated and measurement results may be caused by fabrication errors. Figure 19c shows the measured and simulated radiation patterns at 28 GHz for a 0\({}^{\circ}\) beam steering angle with a connector and feeding network. The simulated and measured gains at 0\({}^{\circ}\) are 10.7 and 9.7 dBi, respectively. The simulated FBR is 15.5 dB and there is no measured FBR result due to the limitations in the rotating angle of measurement facility. The simulated HPBW with a connector and feeding network is 162.3\({}^{\circ}\) as shown in Figure 19c. However, the measured radiation pattern in the \(xz\) plane between 60\({}^{\circ}\) and 120\({}^{\circ}\) is drastically deteriorated due to the influence of the RF cable and metal structures. As shown in Figure 19c, in the case of measuring radiation patterns between 60\({}^{\circ}\) and 120\({}^{\circ}\), the jig is rotating toward the +150\({}^{\circ}\) direction and the electromagnetic wave radiated from the fixed reference antenna is affected by the RF cable and metal structures which are electrically large at the 28 GHz band. However, the rest of the measured radiation pattern in the \(xz\) plane is similar to the simulated one. Figure 19d shows the simulated and  
Figure 18: Measurement setup: (**a**) measurement setup in an anechoic chamber, (**b**) measurement setup for the \(yz\) plane radiation pattern, and (**c**) measurement setup for the \(xz\) plane radiation pattern. measured beam steering performance at 28 GHz. In the simulation, the peak gain of 10.52 dBi is located at \(-30^{\circ}\) in the \(yz\) plane with a SLL of \(-10.9\) dB. However, the measured peak gain of 9.33 dBi is located at \(-19^{\circ}\) in the \(yz\) plane with a SLL of \(-10.5\) dB. Discrepancies between the simulated and measurement results may be caused by bending of the substrate as shown in Figure 19b. The 0.2 mm thick substrate is so thin that it is easily bent and this affects the beam steering performance significantly. However, the measured and simulated results are in good agreement except for the beam peak location.