ACS‐fed UWB‐MIMO antenna with shared radiator

Abstract

A novel asymmetric coplanar strip (ACS)-fed multiple-input-multipleoutput (MIMO) antenna working in the ultra-wideband (UWB) frequency band with a shared radiator is discussed. The proposed antenna is composed of a radiator which is shared by two antenna elements in order to achieve a very compact size of 26 × 26 mm 2 . By etching an I-shaped slot in the radiator and attaching a rectangular patch on the back, the operating bandwidth is broadened and a high isolation between the two antenna elements is realised. The stub from the ground also has a great effect on the return loss and isolation. The measured results show that the working frequency band of the MIMO antenna covers 3.1-10.6 GHz with an isolation of more than 15 dB. Furthermore, the simple feeding structure and compact size could enable the proposed antenna to be used in portable devices.Introduction: Ultra-wideband (UWB) technology possesses great merits including high data rate, low cost and easy fabrication [1], but this excessively researched technology suffers from multipath fading. To solve this problem, a multiple-input-multiple-output (MIMO) antenna was introduced [2]. However, when two antenna elements work closely to each other, the mutual coupling between the two antenna elements becomes strong and the MIMO antenna cannot reach high isolation and a wide operating band without further steps being taken [3]. Li and Feresidis [4] introduced a double-layer EBG structure where three slit-patch structures are inserted in the ground plane between two closely placed UWB monopoles, and the isolation of the whole working frequency band is larger than 15 dB. Gao and He [5] presented a 5.5 GHz band-notched UWB-MIMO antenna using a coplanar waveguide (CPW)-fed to achieve a small size of 48 × 48 mm 2 and a stub from the ground, which could enhance the isolation to more than 15 dB in its operating frequency band. Liu and Wang [6] demonstrated a MIMO antenna using an asymmetric coplanar strip (ACS)-fed structure to reach a compact size of 28.5 × 28.5 mm 2 ; in order to raise the isolation between the two antenna elements, a stub stretched from the ground is introduced, the impedance bandwidth of the antenna covers the UWB frequency band with an isolation of more than 15 dB.

A UWB MIMO slot antenna using defected ground structures for high isolation

“…In Reference , to obtain low mutual coupling, inverted L‐stubs and a complementary split‐ring resonator were added to the ground. A metal reflector was printed on the back of the substrate to decrease the mutual coupling for an asymmetric coplanar strip‐fed antenna, reported in Reference . Moreover, the neutralization line is also an efficient method to enhance the isolation between the close elements .…”

Design of a compact protrudent‐shaped ultra‐wideband multiple‐input‐multiple‐output/diversity antenna with band‐rejection capability

“…Two planar radiators with microstrip‐fed over half‐sized ground plane are orthogonally placed to achieve a less mutual coupling among the two radiators . In Reference , the compactness, UWB operation, and isolation are achieved by cutting an I‐shaped slit in the radiator and affixing a rectangular stub on the other side. A small meandering monopoles UWB diversity antenna is presented by linking inverted L‐shaped parasitic strips and two smaller L‐shaped stubs, whereas isolation is achieved by cutting a slot at the center of the ground in Reference .…”

A Penta-Band Reject Inside Cut Koch Fractal Hexagonal Monopole Uwb Mimo Antenna for Portable Devices

“…To improve the isolation, an L-shaped stub is introduced between the antenna elements, but the isolation between the antenna elements decreases due to the introduction of a defected ground structure. In [10], an I-shaped slot acting as a defected ground structure is introduced where the size of the antenna is 26×26 mm 2 . The isolation between the antenna elements is greater than 15 dB, and the peak gain of the antenna is 4.5 dBi.…”

“…The gain of the antenna is 4 dBi. Compared to the antenna structures in [10][11][12], the introduction of Koch fractal geometry improves the gain of the antenna, and the isolation between the antenna elements is also improved due to the presence of a defected ground structure in the ground plane.…”