Due to limited antenna space, high communication requirements, and strict regulatory constraints, the design of antennas for modern mobile phones has become an exceedingly challenging task. In recent years, numerous studies have been conducted in this area, leading to significant advancements. This review paper comprehensively summarizes recent progress made in antenna design for modern mobile phones. Firstly, the challenges faced in antenna design for modern mobile phones are described, including bandwidth enhancement, integration and decoupling techniques, mm-wave array antennas, satellite communication antennas, as well as interactions between mobile antennas and the human body. Secondly, the basic antenna types (such as inverted-F, slot, loop, and planar inverted-F antennas) commonly used in modern metal-bezel mobile phones along with their key characteristics are briefly summarized. Thirdly, the commonly exployed methods used in practical applications for designing wideband antennas within compact sizes and achieving decoupling among multiple antennas with wide bandwidths are collected. Fourthly, recent advances in the design of compact, wideband, and wide-angle scanning mm-wave arrays for modern mobile phones are summarized. Fifthly, recent progress made in satellite communication antenna designs for modern mobile phones, including broadside and end-fire radiation patterns, is presented. Sixthly, recent studies on the interaction between mobile antennas and the human body are briefly concluded. Finally, the future challenge of antenna design for mobile phones is briefly discussed. It is our hope that this comprehensive review will provide readers with a systematic understanding of antenna design principles applicable to modern mobile phones.

Programmable metasurface (PM) exhibits powerful capabilities to manipulate electromagnetic (EM) waves with controlled active components loaded on the sub wavelength elements. However, for electrically large metasurface with complex structures, it is difficult to implement the fast mapping from the codes, i.e., states of the active components, to radiation patterns and vice versa. In this article, artificial neural networks are employed to realize code-to-pattern (C-P) and pattern-to-code (P-C) mapping accurately and efficiently. As for the C-P mapping, a novel physics-inspired neural network (PINN), which is primarily inspired by the discrete dipole approximation (DDA) method, is proposed. The PINN is physically interpretable and shows a strong few-shot learning ability. The average error between the patterns predicted by the PINN and measured patterns is as low as 2.31 dB. For the P-C mapping, a deep neural network (DNN) is proposed with PINN as its teacher network, i.e., PINN is used to generate more radiation patterns to train the DNN. The average accuracy of codes prediction is higher than 98.4%. Finally, an intelligent beamforming scheme is implemented by combining the PINN and DNN. For the desired patterns, the required codes could be accurately calculated by the DNN in real time. Then, the synthesized patterns of the required codes could be achieved by the PINN to compare with the desired patterns. The proposed scheme is a first step toward practical applications of PM in the fields of sensing and communication.

This letter presents a wideband/multi-band quad-antenna system for 4G/5G/GPS metal frame mobile phones. The quad-antenna system has two kinds of antenna elements and four antenna elements. The merit of the proposed antenna system is that a quad-antenna system is achieved under the condition of metal frame and without using any decoupling structure, the desired bands for 4G/5G/GPS are covered. A prototype was fabricated and measured. For the first kind of antenna elements (including two antenna elements), the bands of 698-960MHz, 1710-2690MHz and 3400-3600MHz are covered, the LTE700/GSM850/GSM900/GSM1800/GSM1900/LTE2300/LTE2500/3.5GHz bands all are covered. For the second kind of antenna elements (including two antenna elements), the bands of 1400-2690MHz, and 3400-3600MHz are covered, the GPS, GSM1800/GSM1900/LTE2300/LTE2500/3.5GHz bands are covered. The measured isolations are bigger than 10dB. The measured efficiencies are bigger than 40% at all the working bands. The measured envelope correlation coefficients are very suitable for MIMO communication systems.

This paper presents an eight-band antenna for full-screen metal frame LTE mobile phones with the size of 142mm×79mm×7.5mm. The proposed antenna mainly consists of two monopole branches, a match circuit and two ground branches. The two monopole branches and the match circuit are used to cover the lower band (698-960MHz) and part of the higher band (1710-2690MHz). One of the two ground branches is used to cover the other part of the higher band, and the other is mainly used to make the lower band matched. The merit of the proposed antenna is that eight bands can be realized under the conditions of an only 2mm ground clearance and a metal frame, it is very suitable for full-screen metal frame mobile phones. A prototype is manufactured and measured. The measured -6dB impedance bandwidths are 300MHz (665-965MHz) at the lower band and 1190MHz (1610-2800MHz) at the higher band. The LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, and LTE2500 bands are covered. The measured efficiency is bigger than 42%, so it is practical for mobile phone applications.

A reconfigurable 1 bit millimeter-wave array antenna for mobile terminals is investigated. The reconfigurable array antenna consists of four reconfigurable 1 bit microstrip patch antenna elements. Each patch antenna element is fed by a slot on the ground. The 1 bit patch antenna element with phase values of $-\pi $ and 0 is achieved by selecting the feeding direction of microstrip line. After analyzing the performance of the 1 bit four-element array, a fixed phase is applied to mitigate the negative effects of the 1 bit phase quantized error. The 1 bit four-element arrays with and without the fixed phases are compared in detail. The overlapped −10 dB impedance bandwidth of a prototype array at different beam directions reaches 3 GHz (25–28 GHz). Within the frequency range of 26–28 GHz, the array with the fixed phases can steer the main beam from −34° to 35° without grating lobes. Within these steering beams, the performances of good array gain, moderate sidelobe level, and low cross-polarization level are achieved.

In this paper, a shared-aperture design of the cellular antenna and satellite communication antenna with circular polarization (CP) in S-band for metal-bezel smartphones is proposed and studied. The proposed antenna consists of a lower-frequency band and CP (LB&CP) antenna and two middle- and high-frequency band and N78 (MHB&N78) antennas. By applying a pair of low-stop high-pass filters, a CP satellite communication antenna working in S-band is designed in the same aperture of the cellular antenna working in the LB band, which is the LB&CP antenna. Furthermore, the two MHB&N78 antennas, labeled as MHB&N78 antennas 1 and 2, are integrated to the LB&CP antenna which cover more cellular frequency bands. The cellular antenna working in the LB, MHB, and N78 bands and the CP satellite communication antenna working in the S-band are integrated into a compact space. For the LB&CP antenna, the measured -6 dB impedance bandwidths are 289 MHz (676-965 MHz), and 185 MHz (1960-2145 MHz) with the average efficiencies of 42% and 35.8%, respectively. The measured 3 dB AR bandwidth is 75 MHz (2.03-2.105 GHz). For the MHB&N78 antenna 1, the measured -6 dB impedance bandwidths are 1610 MHz (1540-3150 MHz) and 400 MHz (3.32-3.72 GHz) with the average efficiencies of 54.6% and 57.4%, respectively. The measured -6 dB impedance bandwidths of the MHB&N78 antenna 2 are 1270 MHz (1710-2980 MHz) and 230 MHz (3.37-3.6 GHz) with the average efficiencies of 58% and 48.1%. The proposed antenna with the characteristic of shared-aperture of the cellular antenna and satellite communication antenna, CP in S-band, and multiple bands coverage is a promising candidate for future 6G smartphones.