# Review of Recent Phased Arrays for Millimeter-Wave Wireless Communication
## 2 Millimeter-Wave Antenna Array for 5G Communication
### Millimeter-Wave Antenna Arrays for 5G Mobile Terminals
#### 2.1.3 Single-Layer Phased-Array Antennas for 5G Mobile Terminals
The angular scanning range of subarrays A, B, and C point in the \(\varphi\) directions of \(\pm\)73\({}^{\circ}\), \(\pm\)128\({}^{\circ}\), and \(\pm\)20\({}^{\circ}\), respectively. The efficiency of subarrays A, B, and C are 74.3%, 68%, and 72.2%, respectively. Figure 11: (**a**) Printed switchable array antenna configuration of subarrays. (**b**) S-parameter plots of proposed array antenna for elements 4, 12, and 20 in subarrays A, B, and C, respectively, using discrete ports. (**c**) Gain patterns with beam-steering in the \(\varphi\) direction of each subarray with all elements. (**d**) Radiation gain patterns with 70\({}^{\circ}\) beam-scanning: at \(\varphi\) = 73\({}^{\circ}\) for subarray A, at \(\varphi\) = 128\({}^{\circ}\) for subarray B, at \(\varphi\) = 20\({}^{\circ}\) for subarray C. (**e**) Illustration of proposed phased-array antenna with coaxial feed cables. (**f**) Prototype of proposed phased-array antenna with coaxial feed cables. (Redrawn from [50])  
[PERSON] et al. also reported a study of user effects on the proposed switchable array in user mode, i.e., talking mode and data mode, at 28 GHz. Figure 12a illustrates different setups in user mode, where \"top\" and \"bottom\" indicate the switchable array position at the top of the chassis near to the index finger and at the bottom of the chassis close to the hand palm, respectively. The electrical properties of skin and different tissues were taken from [50]. Parametric results for the switchable array on the top and bottom of the chassis in talking mode and data usage mode are shown in Figure 12b,c, respectively. Based on the parametric analysis and results, it is proposed that the switchable array has a better performance in terms of beam-switching, body loss, and realized gain on the chassis top position when compared with the bottom of the chassis. It is also proposed to design an additional array on the bottom side of the chassis, which results in a decreased shadowing effect in talking mode. Figure 12: (**a**) User effect setup for: talk mode (**left**) and data mode (**right**). (**b**) Gain plots of each subarray for top and bottom sides of chassis in talking mode. (**c**) Gain plots of each subarray for top and bottom sides of chassis in data usage mode. (**d**) Measurement setup for free space (**left**) and for talking mode with real person (**right**). (Redrawn from [50])  
[PERSON] et al. presented a study and design of a novel phased-array antenna operating at 28 GHz with beam-steering applications for a 5G mobile terminal with metallic casing in [41]. The proposed beam-steering array comprises two subarrays, each having eight identical elements on both sides of a mobile device with a metallic casing, as shown in Figure 13a. A slot element with a cavity-backed structure is proposed, which is easy to fabricate on the metallic casing of the mobile terminal. An important factor is to determine the optimum position of the proposed phased subarrays inside the mobile terminal before finalizing the actual design in practice. The length of the slot is kept at the half-guided wavelength \(\lambda_{\mathrm{g}}/2\), i.e., 5.8 mm at an operating frequency of 28 GHz, and the corresponding slot width is 1.5 mm with a cavity height of 4 mm. The high-gain directional radiation pattern of the slot element is achieved. Figure 13c illustrates the design of one of the proposed eight-element phased arrays. It is proposed to use small stepped pins soldered on the microstrip feed line feeding each element of the subarray. The microstrip feeding line is printed on a 0.254-mm-thick Rogers 5880 substrate having a dielectric constant of 2.2 and a loss tangent/of 0.0009. Each element has been provided by the phase variation using 6-bit phase shifters within a 28-GHz front-end RF integrated circuit (RFIC) chip to accomplish beam-steering, as illustrated in Figure 13e. Figure 13d shows the block diagram of the eight-element beam-steering phased array. Figure 13: _Cont._  
Figure 13f shows the simulated and experimented S\({}_{11}\) and S\({}_{21}\) plots.