Two self‐decoupled, closely‐spaced, metal‐frame LTE MIMO antennas with compact frame lengths to fit in the short edge of the metal‐framed smartphone are presented. The 2 MIMO antennas include a first antenna covering the LTE low band (LB) in 824–960 MHz and LTE middle/high band (M/HB) in 1710–2690 MHz and a second antenna covering the LTE M/HB in 1710–2690 MHz. With a small ground clearance of 5 mm, the first antenna uses a radiating metal frame (frame 1) of length 47 mm to cover the LTE L/M/HB, while the second antenna uses a radiating metal frame (frame 2) of 23.4 mm for the LTE M/HB coverage. In addition, frames 1 and 2 are closely spaced with a gap of 2 mm only. Wideband decoupling between the 2 antennas for the 2 × 2 MIMO operation in the LTE M/HB is obtained with frame 2 serving as an inherent decoupling structure. That is, frame 2 not only functions as a radiator of the second antenna but also serves as a decoupling structure to attract the surface currents on the system ground plane which causes the coupling of the 2 antennas. Applications of applying another 2 MIMO antennas at the opposite short edge of the smartphone for the 4 × 4 LTE M/HB and 2 × 2 LTE LB MIMO operations are also addressed.

A combined‐type dual‐wideband antenna with its lower wideband and higher widebands, respectively, contributed by two separate radiating portions thereof is presented. The two separate radiating portions (one low‐band antenna and one high‐band antenna) are easily combined into a compact structure for the 2G/3G/4G operation in the 698–960 and 1710–2690 MHz bands. In addition, for applications in the typical tablet device such as a tablet computer, the proposed antenna requires a very small ground clearance of 10 × 30 mm2 for the 2G/3G/4G operation. The low‐band antenna for the 698–960 MHz band is an inverted‐F antenna, with its radiating arm coupled to the antenna's feeding strip through a first chip inductor and its shorting strip embedded with a second chip inductor. The high‐band antenna for the 1710–2690 MHz band is a monopole antenna formed by connecting a simple strip to the feeding strip and enclosed by the low‐band antenna so as to achieve a compact antenna structure. A simple matching circuit disposed on the device ground plane can, respectively, widen the bandwidth of the antenna's lower and higher bands. The proposed combined‐type antenna can easily achieve dual‐wideband operation with a small antenna volume, and a promising antenna design for the 2G/3G/4G tablet device is presented. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2799–2805, 2014