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A novel wideband polarization rotating element based on a metasurface antenna is proposed. To achieve high polarization isolation and low cross polarization, a wideband differential-driven dual-polarized metasurface antenna is designed accordingly. By connecting the two differential ports of the dual-polarized metasurface antenna, a wideband polarization rotating metasurface element (PRMSE) is realized, while a large polarization rotating bandwidth of 27.6% can be achieved. In addition, combining the true-time delay (TTD) microstrip lines, the PRMSE can achieve linear phase response and can be applied to the folded reflectarray design. Based on the PRMSE, a 140-element center-fed folded reflectarray (FRA) is designed and fabricated. The measured radiation patterns of the FRA are stable within the frequency range from 26 to 32 GHz. The measured −10 dB impedance bandwidth is 25.4% from 25.4 to 32.8 GHz. Furthermore, the measured 1 dB gain drop and 3 dB gain drop are 20.7% and 34.5%, respectively. The measured sidelobe levels are below −13 dB and the cross-polarization levels are below −30 dB at the broadside direction within the entire operating band.

A novel frequency-selective rasorber with one highly selective passband between two absorption bands is presented. Based on the equivalent circuit analysis, the approach of using a second-order band-pass response in the lossless layer is adopted to improve the selectivity of the passband. A two-layered structure consisting of one lossy and one lossless layer is then used for implementation. The lossy layer is constructed using stub resonators, while an aperture-coupled resonator is used to realize lossless layer and achieve the highly selective passband. Under normal incidence, the operating bandwidth of the proposed rasorber is 110.6%. One passband with sharp roll-off edge and small insertion loss (0.08 dB) is achieved at 4.3 GHz. For demonstration, one prototype was fabricated and measured, and a good agreement is observed accordingly.

This communication proposes a dual-band antenna hybridizing a folded reflectarray antenna (FRA) and a folded transmitarray antenna (FTA). First, a polarization-rotation transmitarray is designed based on a new Fabry-Perot (FP)-liked phasing element. Unlike its counterparts, this new FP-liked phasing element twists the polarization of electromagnetic (EM) wave and provides sufficient phase tuning range only in the operating band of FTA. In the meantime, in the band of FRA, the transmitarray acts as the polarizing grid, which reflects one polarization while allows the orthogonally polarized one to pass without affecting its polarization and phase. Second, a polarization-rotation-ground-integrated (PRGI) reflectarray is designed. The reflectarray collimates the EM wave in the band of FRA and twists its polarization by 90°, forming the folded reflectarray. Meanwhile, it also twists the polarization of the EM wave in the band of FTA. By hybridizing the FTA and FRA sharing the same aperture, the proposed design achieves dual-band high gain radiation. To the best of our knowledge, this is the first time that the FRA and FTA are combined to form a shared aperture antenna, which inherits the advantages of both FRA and FTA, such as high gain, low profile, and reduced blockage effect of the feed. An antenna prototype is fabricated and measured to verify the idea.

In this article, various types of six-port balanced rat-race couplers with wideband common-mode suppression characteristics are presented. In these couplers, the input and output ports can functionalize either as single-ended or differential terminals to realize different operational modes. The power-splitting ratio for these balanced couplers can be flexibly adjusted by means of the values of the characteristic-impedance parameters of their constituent transmission-line segments. Furthermore, the employment of double-sided-parallel-strip-line-(DSPSL)-based 180° phase inverters instead of half-wavelength transmission-line-based ones allows for the considerable enlargement of their operation bandwidth in more-compact circuits with lower in-band insertion-loss levels. For experimental-validation purposes, two microstrip prototypes at $f_{0}=0.9$ GHz with equal and unequal power division are fabricated and characterized. They exhibit common-mode rejection levels higher than 15 dB from 0 to 1.8 GHz (i.e., 0– $2f_{0}$ ) and differential-to-common- mode-conversion suppression levels above 15 dB within the spectral range 0–1.49 GHz (i.e., 0– $1.65f_{0}$ ).

In this article, the design and implementation of two 28-GHz millimeter-wave on-chip high selectivity bandpass filters with coupled dual-behavior resonators are proposed. The proposed bandpass filters consist of coupled dual-behavior resonators with open/shorted stubs. Two and three out-of-band transmission zeros can be realized for the two bandpass filters. Two on-chip millimeter-wave bandpass filters are designed and fabricated for verification. The measurement results show that the insertion losses are both less than 2.2 dB at the center frequency. The sizes of the designed filters are $2.556\,\,\text {mm}\times 1.23$ mm and $3.155\,\,\text {mm}\times 1.47$ mm, respectively, including the pad.

A novel compact differential-fed dual-polarized filtering patch antenna is proposed. Specific filtering response with radiation nulls is firstly realized for the dual-polarized antenna element by symmetrically loading defected ground structures (DGSs), a cross slot, and eight shorting pins without extra circuits. The DGS with pins can generate a lower edge radiation null for a sharp roll-off rate and simultaneously introduce extra in-band resonance for wide passband. Meanwhile, the cross slot with pins can offer an upper edge null and an in-band resonance. Combining with inherent higher order-mode null of the patch itself, the skirt selectivity and stopband suppression at upper band can be significantly improved. Meanwhile, the $\vert $ Sdd $11\vert $ at the upper and lower stopbands is close to 0 dB to achieve high stopband suppressions. As a result, a compact high-gain dual-polarized filtering patch antenna is readily constructed. Thanks for complete symmetry of above structures, the proposed method is very suitable for dual-polarized antennas, where all the performance for both polarizations are identical. For demonstration, a prototype of the proposed antenna is fabricated and measured. Good agreements between the measured and simulated results are observed, indicating good performance with a large bandwidth of about 23% and a peak gain of up to 8.9 dBi within the passband, as well as out-of-band suppression levels of more than 20 dB. Compared with other reported filtering antennas, the proposed filtering patch antenna not only exhibits good wideband dual-polarization radiation but also features high gain in a compact structure for very high aperture efficiency and ultralow cross-polarization level due to the differential feeding and complete symmetry.

This article presents an aperture-shared dual-band large frequency-ratio high gain antenna for sub-6 GHz and millimeter-wave (mm-wave) bands applications. Initially, the partially reflective surface (PRS) of the Fabry-Pérot cavity (FPC) antenna operating at the sub-6 GHz band is realized by using single-layered periodic grid patches while the opaque region of the mm-wave bandwaveband Fresnel zone plate (FZP) lens antenna is implemented by using periodic double-screen dipoles. Then, the PRS and the FZP lens are hybridized together and upgraded into a kind of composite metasurface, which simultaneously functions as the PRS of the sub-6 GHz FPC antenna and the mm-wave bandwaveband FZP lens with little dual-band mutual interference. Thus, the FPC antenna and the FZP lens can share the same aperture with high aperture reuse efficiency. Because the principles are based on the FPC resonance and the collimating FZP lens, high gains are achieved at both bands without a feeding network. Meanwhile, a dual-band large frequency-ratio antenna is designed as the feed. A prototype working at 3 and 28 GHz bands is designed, fabricated, and measured to verify the idea.

A planar ultra-wideband modular antenna array with an ultra-low profile based on a tight coupling effect is proposed. The antenna array is composed of multi-layer printed circuit boards. Since its frequency operation can extend up to the grading lobe frequency, the number of T/R components for the antenna aperture is reduced to the greatest extent. Specifically, a horizontal “fin” structure is added on the parallel feeding lines, which assists in improving the impedance matching of the array. In order to break the bandwidth limitation of the low-frequency loop mode, a capacitive short-circuit probe is introduced to push the common-mode resonance point into the low-frequency band. Finally, subject to Active VSWR < 3, the array can realize E-plane, H-plane, and D-plane ± 45° beam scan coverage across the 6:1 frequency band (3.48–20.97 GHz). A 128-element prototype was processed and tested to validate the design. This array not only has the advantages of low profile, modularity, easy assembly, and maintenance but also minimizes the number of T/R components and reduces the cost of phased array antennas.

A high gain oversized annular lens antenna for 28-GHz band channel measurement system is presented. The proposed antenna is composed of an omnidirectional feeding source and an oversized annular lens. The feeding source is a compact multi-stepped biconical antenna with a wide impedance bandwidth. By rotating a horizontally placed two-dimensional extended hemispherical lens around the vertical axis, the oversized annular lens is realized, which effectively increases the vertical radiation aperture and maintains high aperture efficiency to enhance the omnidirectional gain. Under the same envelope, the proposed antenna features a higher gain than the biconical antenna and the ordinary annular lens antenna. A prototype is fabricated and measured. The measured results demonstrate that the -10-dB impedance bandwidth is 20.7% (24-29.6 GHz), with stable vertically polarized (VP) omnidirectional radiation patterns and gain over 10.3 dBi within the entire band of interest.

This paper presents a circularly polarized millimeter-wave antenna for 5G applications based on magnetic dipole radiation. The radiation part is mounted on the ground directly, which is based on the magnetic dipole structure. This arrangement contributes to the robustness of the antenna. Surrounding cavity is utilized to improve the radiation performance. Sequentially fed scheme is applied to generate circularly polarized waves. The simulation results show that the designed antenna works well from 26 to 30 GHz. The radiation patters show low cross-polarization of below −45 dB in boresight with the peak gain of about 8 dBic. The axial-ratio is better than 3.15 dB within the beamwidth of 120°. Besides, good consistence of the radiation patterns on orthogonal planes is also observed.

In this article, we review the terahertz (THz) dielectric transmission lines in recent decade. Moreover, the developed special measurement technologies for measuring the THz dielectric transmission lines are introduced. Final, the various application scenarios of the THz dielectric transmission lines are presented.

A novel high gain planar aperture antenna array, which is applied to 5G millimeter-wave systems, is proposed in this paper. The antenna element is fed by a slot on a substrate integrated waveguide (SIW). The element radiation structure consists of an opening cavity with multiple cross-shaped patches on the top, which extend the aperture field to realize an uniform aperture electric field distribution and thus a high element gain. Simulated results show that its operation band is from 26.2 to 29.6 GHz (12.2%), covering the n257 band (26.5-29.5GHz) with a peak gain of 19.65dBi. Based on the element, a 4 × 2-element antenna array is designed, whose -10-dB impedance bandwidth covers from 25.9 to 29.6 GHz (13.3%). The gain reaches about 24.5-26.7dBi within the operating band. The proposed array is suitable for packaging integration and can be potentially used for 5G point-to-point communication applications.

A novel millimeter-wave (mmW) $4 \times 4-$ element wide-angle scanning phased array based on metasurface for 5G applications is proposed. The elements adopt non-periodic metasurface to control the aperture field distribution, which broadens the element beamwidth and thus helps improve the scanning performance. The 10-dB impedance bandwidth of the $1 \times 4-$ element subarray can cover the frequency band of 24.2529.5 GHz (20%), corresponding to the 5G mmW band. Based on the subarray, a $4 \times 4$-element planar phased array with 1-D scanning capability is designed. Furthermore, a II-shaped structure is introduced between the subarrays to achieve a non-uniform aperture field on the array surface, further improving the element beamwidth along the scanning direction and leading to a wide scanning range. The simulated results show that, within the 5G mmW band, the proposed array produces a minimal gain of 15 dBi at the broadside direction and the antenna efficiency is over 75%. The proposed phased array can cover the scanning range from ± 55° with a gain fluctuation less than 3 dB, and the maximum scanning angle of ± 60°.

This paper presents a dual-band co-aperture monopolar antenna with a very low profile. A novel cross-layer folded structure is first constructed to radiate in the lower band. Meanwhile, it provides enough space for another higher-band section. Then, a via-loaded circular patch is added to the reserved space, and the dual-band co-aperture antenna with independent band performance is obtained. By employing two pairs of similar modes in the two bands, the proposed antenna achieves a relatively large bandwidth of 10.9% in the lower band and 14.6% in the upper band with a thickness of 3.14 mm. Stable conical beam are achieved within both bands and the gains in the lower and upper bands are 5.2-5.8 and 3.7-5 dBi, respectively.

A drug delivery system of forsythoside A-loaded exosomes(FTA-Exos) with high biocompatibility and low immunogenicity was established to investigate its impact on the migration of human lung epithelial adenocarcinoma A549 cells. The exosomes from A549 cells were extracted and purified by ultra-high speed centrifugation and ultrafiltration. FTA-Exos were prepared by ultrasonic incubation, and characterized by particle size analysis, transmission electron microscopy, and Western blot assay. The uptake of FTA-Exos by A549 cells was observed under the laser confocal microscope, and the impact of FTA-Exos on the migration of A549 cells was investigated by cell scratch assay. The results showed that the average particle size of the prepared FTA-Exos was(138.90±2.37) nm, which increased slightly after drug loading. The PDI was 0.291±0.013, and the average potential was(-10.1±0.66) mV. The FTA-Exos were spheroidal in appearance as observed by transmission electron microscope, with an obvious saucer-like double-layer membrane. Western blot assay indicated that the specific proteins CD63 and Alix were both expressed in exosomes. The laser confocal microscopy suggested that FTA-Exos were taken up by A549 cells and stably maintained in the cell for 4-8 h, and the fluorescence was significantly enhanced at 4 h. The scratch assay showed that the inhibitory effect of FTA-Exos on the migration of A549 cells was significantly stronger than that of forsythoside A(Plt; 0.05). In conclusion, the drug delivery system of FTA-Exos established in this study had good stability, reliable preparation process, and potent inhibitory effect on the migration of A549 cells in vitro, which can provide an important reference for subsequent in-depth research and application.

Polarizing beam splitters (PBSs) are essential components for polarization-multiplexed communication system. However, conventional PBS, such as Rochon prism and Wollaston prism, must be sufficiently thick to generate enough walk-off distance between two orthogonal polarizations due to the low birefringence of natural material. To reduce this requirement, we propose and demonstrate a three-dimensional printed low-cost low-profile Fresnel-Rochon prism. By adjusting the dimensions of the artificially engineered gratings that comprise the prism, the refractive index tensor along the x - and y -direction can differ, enabling the independent manipulation of the deflection angles of the orthogonal polarized components. Applying the Fresnel principle to this Rochon prism, the thickness can be greatly reduced while the polarization splitting and deflection angles remain unaltered. Meanwhile, the transmission efficiency of the prism is also improved as less energy is dissipated in the lossy printing material. In addition, in contrast to conventional Rochon prisms formed by two right triangle prisms, the proposed Rochon prism enjoys the benefit of simple fabrication without any further assembly procedure. Prototypes operating at 0.14-THz frequency were printed and measured to verify the idea.

Rational designing and synthesizing highly efficient oxygen evolution reaction (OER) electrocatalyst plays a key role in energy conversion. However, due to the numerous factors affecting the activity of electrocatalysis, the understanding of their catalytic mechanism is insufficient, and challenges still exist. Herein, the organic group of the metal-organic nanosheets electrocatalyst was replaced by NH2 to CH3 to controllable regulate the catalytic performance of OER, corresponding to the overpotential of OER reducing from 385 mV to 318 mV at 10 mA cm−2, superior to the commercial precious metal based catalyst RuO2. Furthermore, combining the density functional theory (DFT) and electron localization function (ELF) indicates that the type of ligands group can indirectly modulate the electronic structure of metal catalytic center and the degree of electronic localization of the metal-organic nanosheets catalysts, resulting in the change in electrocatalytic activity. This simple catalytic model is more favorable to investigate the catalytic mechanism, providing a new strategy for the development of efficient electrocatalyst.

A compact wideband dual-polarized omnidirectional antenna array for base-station applications is proposed. It consists of ten antenna units. To generate ±45° dual-polarized ominidirectional radiation with low gain variation for each unit, three close-in crossed-dipole elements are uniformly arranged in a regular triangle shape and excited by two 1-to-3 power dividers with equal magnitude and phase, acting as a dual-polarized loop antenna. To obtain wide impedance bandwidth for each unit, the dipole element and power divider are designed to operate in a wide and well-matched band. Moreover, the unit features steady structure, easy fabrication, and high scalability, which makes it convenient to form an antenna array. To achieve a high gain for base-station applications, a ten-unit antenna array is designed, fabricated, and measured. A wide impedance bandwidth of 52.3% (1.62–2.77 GHz) for standing-wave ratio (SWR) < 1.5 and a high port-to-port isolation of 26 dB are realized. It also features a high gain of 10.3 ± 0.9 dBi and a small gain variation of less than 2.5 dB in the horizontal plane. Additionally, the sidelobe suppression of 18 dB and null filling below the main vertical beam are obtained by the designed feeding networks. These results make the proposed design attractive in base-station applications.

This paper presents a filtering power amplifier (PA) with wide bandwidth. A bandpass filter (BPF) using discriminating coupling is first proposed to be utilized as the output matching network (OMN) of PA. Discriminating coupling means that the fundamental and the harmonics of the proposed structure have different coupling coefficients. Thus, the input impedances of the fundamental, second and third harmonics could meet the requirements of the extended continuous mode theory, respectively. Also, good frequency selectivity is obtained. The working principle of discriminating coupling, the filter synthesis theory and the equivalent circuit are utilized to guide the design of the filtering PA. To demonstrate the proposed structure, a compact filtering PA operating at 1.8 GHz is designed. The measured results exhibit good frequency selectivity and high power added efficiency (PAE). More importantly, comparing to the previous filtering power amplifiers (PAs) with good frequency selectivity, the proposed design possesses wide bandwidth of 31.1% with PAE higher than 60%.

In this paper, a rectangular dielectric rod antenna fed by an air-substrate parallel strip line is proposed. The dielectric rod has a compact and regular structure, which is easy to fabricate. The matching of the antenna is mainly determined by the parallel strip line, which simplifies the design process. Fed by an air-substrate parallel strip line, the antenna obtains a relatively uniform magnitude distribution on the surface and a moderate phase constant. With the length of 6 wavelengths at the center frequency of 6 GHz, the antenna generates a high measured gain of 16.7 dBi. The measured 1 dB gain bandwidth is about 18.3%. Over the entire operating band from 5.4 to 6.6 GHz, a stable endfire radiation pattern and a good matching are achieved by the antenna.

A simple, compact filtering patch antenna with wide out-of-band suppression is presented, where the filtering mechanism is first analyzed and implemented based on mode analysis of a conventional patch antenna. According to the mode analysis, undesired higher-order modes can be effectively suppressed by selecting a proper length ratio of two sides of the patch and the feeding position, thus realizing a wide upper stopband. To further enhance the filtering response, another two simple filtering structures loaded on the patch antenna are also proposed. First, a split-ring-shaped slot is etched on the patch to generate a radiation null at the lower-band edge for improving skirt selectivity. Second, a U-shaped strip is etched underneath the patch and connected with the feeding probe, which can introduce another null at the upper band edge. As a result, a high suppression level of 23 dB in lower and upper stopbands can be realized, respectively, for the proposed filtering antenna, while the upper stopband can extend up to $2.3 f_{0}(f_{0}$ is the center frequency of the antenna). Furthermore, wide passband response can also be achieved by the extra in-band resonances existing in the slot and the strip. A filtering antenna prototype is fabricated and measured for demonstration. Good agreements between the simulated and the measured results are observed, indicating a large impedance bandwidth of 22.6%, high antenna efficiency of 95.6%, and an average gain of about 7.4 dBi. Compared with the reported filtering antennas, the proposed filtering antenna can achieve better wideband filtering response but with a simpler configuration.