This letter presents an antenna system for mobile devices with an unbroken metal rim. By utilizing the characteristic mode analysis for the unbroken metal rim, efficient multiple-inputmultiple-output operation can be achieved. The design is based on an antenna cluster technique that uses several coupled elements that are used to efficiently excite the modes of the rim. Nonresonant antenna elements and matching networks are used to couple to the metal rim. The design has small ground clearance of 5 mm and height of only 4 mm, and can operate in wide bandwidths both in 700-960 MHz low band and 1.56-4 GHz high band. Measurement results confirm that competent performance is achieved.

Modern antenna design is facing increasing issues with the radiation efficiency, since the space available for antennas is scarce and antennas are fitted into lossy environments. This letter presents a multiport antenna design method with a computationally efficient way to realize the port currents providing the highest radiation efficiency. In this method, an antenna is described with multiple excitation ports in electromagnetic simulations. The measurement results of an example design demonstrate the achieved benefit compared to traditional antenna design.

In this paper, we present a novel method to tailor the radiation pattern of an antenna element, such as a single element of an array, by maximing its partial radiation efficiency in the desired angular space. The tailored pattern of the single element is achieved by current distribution synthesis using multiple feed points in the antenna. A method to determine and realize the currents at the feeds is presented. The method is demonstrated by designing and manufacturing a four-element linear array consisting of tailored antenna elements and comparing its performance to the reference case. The element consists of four closely-spaced metallic patches placed on a substrate backed with a ground plane, and each patch is separately fed. The initial four-port feed is reduced to a single feed with a feeding network based on the determined currents. A conventional patch antenna is chosen as the reference. The simulated and measured results show improvement in the realized gain in the desired angular space.

This paper presents the first realization of a lumped-element decoupling and matching network (DMN) for more than two-element mobile MIMO arrays. The realization of the DMN is based on an existing method, which is improved in terms of bandwidth and the number of network elements. The array is designed to operate in the 2.6–2.7 GHz LTE band. The DMN is applied to a four-element MIMO antenna array located on one side of the mobile phone chassis. The array initially has a strong coupling of −3 dB, which is improved to −7 dB with the DMN. In other words, this denotes a reduction of 30 percentage points in coupled power. The DMN also improves the total efficiency by 21 percentage points at best.

This paper studies the benefits of the antenna cluster technique in exciting the orthogonal modes of a metal rim for MIMO operation in the low-band frequencies. The user effect with antenna clusters is studied with measurements of antenna prototype held by a hand phantom. On average, better than 20% total efficiency is achieved over the low-band frequencies and almost 30% average efficiency over the higher frequencies which suggests that the antenna cluster technique can be used to design user effective mobile device antennas.