Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4 epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36-6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context

Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4_epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36–6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context

Gain and Frequency-Selectivity Enhancement of Dual-Polarized Filtering IBFD Antenna Using PRS

A dual-polarized filtering Fabry–Perot antenna (FPA) with high selectivity and high isolation is proposed for in-band full-duplex (IBFD) applications. The proposed antenna utilizes a square patch as the feeding element, which is fed by a double differential-fed scheme for dual-polarized radiation with high isolation. The patch is loaded with a symmetrical cross-slot and four shorting pins for a broad passband filtering feature. To enhance broadside gain across a wide frequency range, the patch is incorporated with a partially reflecting surface (PRS), which is composed of two complementary cross-slot and patch arrays. Moreover, the frequency selectivity of PRS is exploited to improve the filtering characteristic. The double differential feeds are realized based on out-of-phase power dividers, which are combined with simple low-pass filters to further improve the out-of-band suppression. The final design was fabricated and measured. The measurement results show excellent results with a 10-dB return loss bandwidth of 21.5% (4.91–6.09 GHz), isolation of greater than 40 dB, peak gain of 13.7 dBi, out-of-band suppression level of better than 27 dB, and a cross-polarization level of less than −27 dB

Bisbenzylisoquinoline alkaloids from Mahonia nepalensis

From the wood of Mahonia nepalensis DC. 1821, two bisbenzylisoquinolines homoaromoline (1) and isotetrandrine (2) were isolated by using various chromatoghraphies. Their structures were characterized on the basis of the spectroscopic data (1D-NMR, HSQC, HMBC, ESI-MS) in comparison with the literature. This is the first report of 1 - 2 from Mahonia nepalensis. Keywords: Mahonia nepalensis, Isotetrandrine, Homoaromoline, Bisbenzylisoquinoline

Iridoid glycosides from Morinda tomentosa and their endoplasmic reticulum stress modulation activity

Three iridoids 1 - 3, asperulosidic acid, daphylloside, and asperuloside, were isolated from the methanol extract of the leaves of Morinda tomentosa. Their chemical structures were elucidated by 1D- and 2D-NMR spectra and in comparison with those reported in the literature. The effects of these compounds on the endoplasmic reticulum stress in XBP1-eGFP-transfected the 293 T cells were measured. Compound 3 significantly reduced the ER-stress both in DMSO-treated and thapsigargin-treated cells. Unlike this compound, compound 3 selectively reduced thapsigargin-induced ER-stress without any effect on the level of XBP1 splicing in DMSO-treated cells. These results suggested that compounds 2 and 3 can be suggested as new ER stress regulators

A Compact Dual-Band Tripolarized Patch Antenna With Simple Structure and Very High Isolation

A compact dual-band tripolarized antenna with simple structure and high isolation operating at 2.45 GHz and 3.5 GHz bands is presented. The design is composed of a slotted patch and a monopolar patch connected together by four vias. The antenna uses a double differential-fed scheme for x- and y-horizontally polarized broadside radiations and a single-ended port at the center for vertically-polarized omnidirectional radiation. The combination of slotted patch, monopolar patch, and vias yields several interesting features, which are exploited in the design to achieve dual-band tripolarized operation. Thank to the differential feed scheme and structural symmetry, the proposed antenna achieves a very high isolation among all ports. For verification, the final design is fabricated and measured. The double differential-fed scheme are realized by using two wideband out-of-phase power dividers, whose operational bandwidth covers both 2.45 and 3.5 GHz bands. The antenna with profile of $0.09\lambda _{2.45-{\mathrm { GHz}}}$ yields a measured 10-dB return loss bandwidth of $2.43-2$ .49 GHz and $3.23-3$ .66 GHz and isolation of $\ge$ 35 dB among all ports. Tripolarized radiation is verified with far-field measurement, showing highly symmetrical pattern and low cross-polarization in all three operational modes. The proposed design is a good candidate for dual-band communication systems which require polarization and pattern diversity antennas

A Novel Metamaterial MIMO Antenna with High Isolation for WLAN Applications

A compact 2×2 metamaterial-MIMO antenna for WLAN applications is presented in this paper. The MIMO antenna is designed by placing side by side two single metamaterial antennas which are constructed based on the modified composite right/left-handed (CRLH) model. By adding another left-handed inductor, the total left-handed inductor of the modified CRLH model is increased remarkably in comparison with that of conventional CRLH model. As a result, the proposed metamaterial antenna achieves 60% size reduction in comparison with the unloaded antenna. The MIMO antenna is electrically small (30 mm × 44 mm) with an edge-to-edge separation between two antennas of 0.06λ0 at 2.4 GHz. In order to reduce the mutual coupling of the antenna, a defected ground structure (DGS) is inserted to suppress the effect of surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.38 GHz to 2.5 GHz, which entirely covers WLAN frequency band allocated from 2.4 GHz to 2.48 GHz. The antenna also shows a high isolation coefficient which is less than −35 dB over the operating frequency band. A good agreement between simulation and measurement is shown in this context

Bandwidth-enhancement of circularly-polarized fabry-perot antenna using single-layer partially reflective surface

In this article, we investigate bandwidth-enhancement of a circularly-polarized (CP) Fabry-Perot antenna (FPA) using single-layer partially reflective surface (PRS). The FPA is composed of a single-feed truncated-corner square patch antenna, which is covered by the PRS formed by a square aperture array. We revealed that the finite-sized PRS produces extra resonances and CP radiations for the antenna system, which broadened the impedance matching and axial ratio (AR) bandwidths significantly. For verification, a broadband CP FPA prototype operating near 5.8 GHz was realized and tested. The fabricated antenna with overall size of 125 mm x 125 mm x 23.5 mm achieves a |S-11| < -10 dB bandwidth of 31.7% (5.23-7.2 GHz), an AR < 3-dB bandwidth of 13.7% (5.45-6.25 GHz), the peak gain of 13.3 dBic, a 3-dB gain bandwidth of 22.38% (5.0-6.26 GHz), and a radiation efficiency of >91%