In mobile data devices, antennas are the only component that "touches" the network, and optimizing 4G antenna performance is becoming increasingly important. However, the challenges faced in designing 4G antennas for smartphones and tablets are extremely daunting. Although there are multiple feasible solutions to address these challenges, each one has potential performance trade-offs.

There are many factors that can affect the antenna performance of handheld mobile communication devices. Although these factors are related, they can generally be divided into three categories: antenna size, mutual coupling between multiple antennas, and device usage models.

The antenna size depends on three factors: operating bandwidth, operating frequency, and radiation efficiency. Today's bandwidth requirements are becoming increasingly high, driven by FCC frequency allocation in the United States and operator roaming agreements worldwide; Different regions use different frequency bands. 'Bandwidth and antenna size are directly related' and 'efficiency and antenna size are directly related' - this usually means that larger antennas can provide greater bandwidth and higher efficiency.

In addition to bandwidth, the size of a 4G antenna also depends on the operating frequency. In North America, operators Verizon Wireless and AT&T Mobility have chosen to promote LTE products that operate in the 700MHz frequency band, which was part of the FCC UHF-TV redistribution frequency band a few years ago. These new frequency bands (17704-746MHz and 13746-786MHz) are lower than the traditional cellular frequency bands used in North America (5824-894MHz). This change is significant because the lower the frequency, the longer the wavelength, requiring longer antennas to maintain the same radiation efficiency. In order to ensure radiation efficiency, the antenna size must be enlarged. However, device system designers also need to add larger displays and more features, which greatly limits the available 4G antenna length and overall volume, thereby reducing antenna bandwidth and efficiency.

The high-speed wireless protocol for 4G antenna mutual coupling updates requires the use of MIMO (Multiple Input Multiple Output) antennas. MIMO requires multiple antennas (usually two) to operate simultaneously at the same frequency. Therefore, multiple antennas need to be placed on the phone equipment, and these antennas must work simultaneously without affecting each other. When two or more antennas are placed in close proximity, a phenomenon known as mutual coupling occurs.