A Novel 5G LTE Antenna Design for Portable Devices

*is paper presents the low profile, planar, and small-size antenna design for WWAN, LTE, and 5G (5th generation wireless systems) for use in portable communication equipment. *e antenna occupies only 65×13× 0.4mm, and the antenna is combined with a 200× 260mm copper plate to simulated system ground plane. In the low band, a direct-fed right-side arm and a coupled-fed arm implemented can excite a 1/4 λ fundamental resonant mode at 0.85 and 0.76GHz to cover 0.698–0.96GHz and upper 3/4 λ and 5/4 λ resonant modes are controlled by L-shaped element at 2.34, 2.69, 3.4, and 4.0GHz to cover 1.71–2.69GHz and 3.2–4.2 GHz. *e direct-fed left-side arm produced 1/4 λ to cover 5.15–5.85GHz. In far-field measured, peak gain and efficiency in low, middle, and high bands are 0.43–5.67 dBi and 55–86%. Finally, experiments demonstrate that the present antenna exhibits a good performance for portable devices.


Introduction
e evolution of wireless system technology has enabled not only the miniaturization but also the multiband applicability of antenna systems of portable communication devices such as smartphones and laptops (notebooks (NBs)) [1][2][3][4][5]. In particular, not only laptops support wireless LAN (WLAN) but also developments have occurred with respect to 4G/5G wireless systems [6][7][8][9]. A system with long-term evolution (LTE) and sub-6G (FR1) applications is thus required. e antennas inside portable devices must cover BW% (bandwidth percentage) � 31.3% for low band; this antenna covered LTE 700 (0.698-0.787 GHz), GSM 850 (0.824-0.894 GHz), and GSM 900 (0.88-0.96 GHz). At the middle band, the bandwidth percentage was 44.5%, and it equalled GSM 1800 (1.71-1.88 GHz)), GSM 1900 (1.85-1.99 GHz), UMTS (1.92-2.17 GHz), and LTE 2500 (2500-2690 MHz). At the high band, BW% was 21% for C band (3.4-4.2 GHz) and BW% � 12.7% for license-assisted access (LAA) (5.15-5.85 GHz) [2][3][4]10]. In current commercial communication equipment of STBR (screen-to-body ratio) is significant for user impression; thus, limited space is reserved for antennas. In particular, NBs and tablets have multiple smalldimension antennas above the screen such as two WIFI and two LTE antennas [6,11]; it is challenged for small-size antenna design. us, the antennas used in wireless equipment are required to be small as well as to exhibit a low profile. Previously executed research [9,12] has proposed an approach for designing small antennas with a meander architecture. In other research studies [3,8,10,13], meander structures with loop-type antennas were used to achieve a small equipment size. In addition, a bent arm was used by other researchers to design an antenna for multiband applications [12,14]. e present study was executed to design an antenna exhibiting low as well as high operating bands achieved by applying direct-fed and coupled-fed mechanisms; the derived bands can encompass the LTE, WWAN, C band (n77 and n78), and LAA application bands. In the proposed antenna, the arms have a small size and planar structure.

Antenna Design
An FR4 substrate constituted the basis for constructing the proposed antenna in Figures 1(a) and 1(b) and optimized dimensions in Table 1. Fabricated prototype antenna is shown in Figure 2      . For antenna testing in this study, one side of a coaxial cable was connected to the direct-fed arm and the other side was connected to the contact system ground plane, which was used to provide the RF signal input.

Experimental Results and Parametric Study
e derived S 11 values from the simulation executed through ANSYS HFSS software, and measurement in this study is displayed in Figure 3, indicating good agreement. e testing frequencies obtained for an S 11 value of −6 dB covered the 2G, 3G, 4G, and 5G systems. us, the 0.76 GHz fundamental mode was 1/4 λ. For the mode at 2.34 GHz, two null values were observed for the couple-fed arm, as shown in Figure 4(c). us, 2.34 GHz is a higher mode of 3/4 λ. For the mode at 3.4 GHz, three null values were observed for the couple-fed arm, as shown in Figure 4(d).
us, 3.4 GHz is a higher mode of 5/4 λ. Figure 5(a) displays the simulated S 11 values derived when different lengths were considered for the right-side direct-fed arm implemented on the right side. is direct-fed arm had a resonant fundamental mode at 0.85 GHz. When this arm was shortened 5 mm and 8 mm, a 0.85 GHz shift and mismatch were caused, and 0.85 GHz higher mode of 2.69 and 4.0 GHz moved to higher frequencies. Figures 5(b)-5(d) illustrate the simulated current distribution of the rightside direct-fed arm at 0.85, 2.69, and 4.0 GHz, respectively. For the mode at 0.85 GHz, one null was observed for the direct-fed arm, as shown in Figure 5 us, 0.76 GHz fundamental mode was 1/4 λ. For the mode at 2.69 GHz, two null values were observed for the direct-fed arm, as shown in Figure 5(c). us, 2.69 GHz is a higher mode of 3/4 λ. For the mode at 4.0 GHz, three null values were observed for the direct-fed arm, as shown in Figure 5(d). us, 4.0 GHz is a higher mode of 5/4 λ. Figure 6(a) displays the simulated S 11 values when the left-side direct-fed arm was adjusted in terms of length. e fundamental mode of this arm was 5.5 GHz. 5.5 GHz fundamental mode moved toward higher frequencies as the arm was shortened. Figure 6(b) displays the simulated current       International Journal of Antennas and Propagation corresponding radiation efficiency exceeding 55%. e gain was noted to be 0.83-5.67 dBi in the middle band (at 1.71-2.69 GHz; Figure 10), with the corresponding efficiency being 55-83.6%. e gain was determined to be above 3 dBi and 0.9 dBi at 3.2-4.2 and 5.15-5.85 GHz, respectively, in Figure 11 with the corresponding efficiency ranging from 60% to 86.4%. Measured resonant, gain, efficiency, and bandwidth are arranged in Table 2. e proposed antenna has suitable and stable radiation efficiency.
Performance was compared between present antennas with reference to some portable device antenna. Table 3 displays dimension, volume, bandwidth, S 11 , and RLC element. In [1,12,14], LC element is used and bent-type structure greatly reduces dimension, while the volume is larger, and cover bandwidth is less than present antenna. In [4,5,9,10], LC element is not used, and antenna occupies a smaller area, but volume and cover bandwidth are less than present antenna. Furthermore, present antenna can cover

Conclusions
In this paper, a low profile, planar, and small-size antenna design is proposed for 5G portable communication equipment. e proposed antenna uses seven resonant modes to cover the frequency ranges of 0.69-0.96, 1.71-2.69, 3.2-4.3, and 5.15-5.85 GHz. e operating range of the antenna covers the LTE 700/2500, GSM, UMTS, C band (n77 and n78), and license-assisted access (LAA). e proposed antenna has small dimensions, two wide bands of operation, omnidirectional radiation in low-frequency bands, and reasonable antenna radiation efficiency and gain. e measured results of the proposed antenna signify its suitability for portable devices.

Data Availability
e data used to support the findings of this study are available from the corresponding author on request.

Conflicts of Interest
e authors declare that they have no conflicts of interest.