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 low-profile, decoupled two-monopole system with its two parasitic grounded strips conjoined, forming a very compact structure is demonstrated. Each of the two identical antennas comprises a driven coupling strip and a parasitic grounded strip, operating respectively in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands. The two parasitic strips are further joined together, becoming a central, grounded T monopole. By loading a capacitor between the T monopole and the antenna ground, the mutual coupling in the 2.4 GHz band can be reduced by about 12 dB. The capacitor in this design is used to control Ant2 monopole mode to cancel out opposite-phased currents of the dipole mode on the T monopole when Ant1 is excited, such that isolation enhancement can be attained. The proposed two-monopole system occupies a compact size of 5 mm × 40 mm (about 0.04λ × 0.32λ at 2.4 GHz) and is favorable for applications in the narrowbezel notebook computers owing to its low profile of 5 mm.

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A simple and compact, self-isolated printed antenna able to operate in the 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands in notebook computers is introduced. The design is built on a low-cost substrate with the dimensions 6 mm × 30 mm (about 0.05λ×0.24λ at 2.4 GHz) and comprises a symmetrical coupled-fed loop and two parasitic shorted strips. For size reduction, the 2.4 GHz loop is loaded with a pair of L-shaped stubs above the feeding and coupling T strip. The parasitic strips shorted on both sides of the coupling T strip are further added to generate the 5 GHz band resonance. The results show that good radiation characteristics can be obtained in the bands of interest. In addition, when grouping three proposed designs with a gap of 4 mm between them, the results for each antenna impedance bandwidth, the isolation between any two of the three designs, and the envelope correlation coefficient (ECC) are also satisfactory.