Abstract-This letter presents a new concept for frequency reconfigurable antennas. The concept involves a multiport antenna, whose elements are mutually coupled. By properly weighting the excitation signals in each port, the total reflected power can be minimized and radiation efficiency maximized. Different frequency components of the transmitter can be weighted differently to obtain broad instantaneous band. The concept is studied by simulations.

Abstract-The upcoming standards of wireless communications result in additional and more stringent requirements for antennas in mobile phones. In this paper, we present a frequencyreconfigurable antenna that could potentially be suited for future mobile devices. Frequency reconfigurability is achieved through a cluster of mutually coupled antenna elements that are excited with frequency-dependent weights using a multichannel transceiver. We report a mobile handset antenna cluster measuring 15 x 15 x 1.6 mm 3 that covers the frequency bands of 1.7-2.7, 3.3-4.5, and 5.475-6.425 GHz with an antenna efficiency better than 90 %. The operation of the antenna cluster is experimentally verified by feeding all the antenna elements with proper weights using tailor-made power splitters that represent a multi-channel transceiver with adjustable amplitude and phase in each branch. The results obtained with the feed networks suggest the feasibility of the reconfigurability concept, and pave way for co-design of the antenna and the transceiver.

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Realizing capacity demands of future wireless communications requires improved spectral efficiency in the sub-6-GHz frequency bands. This paper proposes a novel eightelement multiple-input multiple-output (MIMO) antenna that can be tuned from 1.7 to 6 GHz. The design is based on the antenna cluster concept, where weighted feeding of multiple antenna elements is used to modify the operating frequency. This paper extends the theory of the concept to account for multiple separate clusters, thus enabling it to be used for MIMO. The proposed antenna achieves over 60% efficiency at frequencies above 3 GHz, and the system exceeds the ergodic capacity of the ideal 7×7 MIMO in that band.Index Terms-Mobile antennas, multifrequency antennas, multiple-input multiple-output (MIMO) antennas

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.