High‐isolation conjoined loop multi‐input multi‐output antennas for the fifth‐generation tablet device

Abstract

Two coupled‐fed loop antennas with a conjoined capacitor‐embedded section to achieve compact size and high isolation for the fifth‐generation (5G) multi‐input multi‐output (MIMO) operation in the tablet device are presented. The two conjoined loop MIMO antennas cover the 5G band of 3300‐4200 MHz, which is considered to be the largest contiguous frequency range potentially available for 5G mobile broadband services below 6000 MHz. The conjoined capacitor‐embedded section not only functions as a part of the resonant path of the two loop antennas but also behaves like a band‐pass resonant structure in the operating band. The latter makes the capacitor‐embedded section to have much lower impedance in the operating band, as compared to that of a simple strip section. This makes it capable of effectively attracting the surface currents on the ground plane excited by one loop antenna to be away from the feed port of the other loop antenna. The two loop antennas can hence exhibit high isolation, even though the two antennas are conjoined to have a simple integrated planar structure of compact size. The envelope correlation coefficient (ECC) of the two conjoined loop antennas is also very small, less than 0.1 in the operating band.

Conjoined ultra‐wideband (2,300‐6,000 MHz) dual antennas for LTE HB/WiFi/5G multi‐input multi‐output operation in the fifth‐generation tablet device

“…That is, much better decoupling of Ant1 and Ant2 is obtained in the experiment, which increases the antenna efficiency. In general, the measured antenna efficiency is all better than 50%, which is acceptable for practical mobile device applications …”

“…Good decoupling between the dual antennas is hence obtained. This kind of conjoined loop MIMO antennas requires no gaps between two antennas and no external decoupling elements are needed as well, different from the traditional MIMO antennas . However, for practical mobile device applications, wider bandwidth to cover different frequency bands is always needed.…”

“…The UWB covers not only the 5G band in 3,300‐5,000 MHz, wider than that in Ref. but also covers the long term evolution (LTE) high band (HB) in 2,300‐2,400/2,500‐2,690 MHz and the Wireless Fidelity (WiFi) band in 2,400‐2,500/5,100‐5,900 MHz . The dual antennas have a new conjoined section of a ring strip for bandwidth enhancement and a band‐pass resonant structure for effective decoupling.…”

“…1 The two coupled-fed loop antennas share a conjoined section grounded to the system ground plane of the mobile tablet device to achieve good decoupling. 1 It is demonstrated that the conjoined section mainly functions as a band-pass structure with same resonant frequency as that of the dual antennas. When the dual antennas are in operation, the conjoined band-pass section will be at resonance as well.…”

One LTE LB and two conjoined LTE M/HB MIMO antennas with a compact symmetric frame structure at the short edge of the metal‐framed smartphone

“…Ant2 and Ant3 are two conjoined antennas operating in the LTE M/HB (1710–2690 MHz) and sharing a band‐pass decoupling strip (strip FF′) shorted to the system ground plane at point G 4 . The band‐pass characteristic is achieved by the lumped capacitor C s (0.9 pF) embedded in strip FF′ and the equivalent distributed inductance of the conjoined section (strip FF′ + strip F′G4) . At the resonant frequency of the band‐pass structure, which is adjusted to be at about 1.7 GHz, the conjoined section will exhibit a zero or very small (close to zero) impedance, thereby effectively attracting the excited surface currents on the system ground plane to achieve good decoupling and low ECC of Ant2 and Ant3.…”