A novel method for a beam pattern reconfigurable circularly polarized (CP) transmitarray antenna based on passive metasurface is proposed by a rearrangement of source antennas. Two source antennas ...among eight source antennas are selected for the fine beam steering. The beam steering angle can be finely controlled by the positions and phase difference of the source. Moreover, this kind of transmitarray antenna can be utilized to generate multibeam by the combination of the source antennas for radiation to different directions. To verify its feasibility, the planar CP source antenna is designed to operate at 5.8 GHz. Also, the metasurface consists of four layer separated by four substrates to cover full transmission phase variation of 2π, and the metallic layers are designed to circular patches. As a result, the steering angle is experimentally observed at each 0, +20, and +40°, and dual beam radiating to −30 and +30° also is measured.
A low-profile high-efficiency transmitarray antenna (TA) for beamforming applications is proposed and investigated in this paper. The partial H-plane waveguide slot array antenna is employed as the ...compact low-profile feeding structure of the beamforming TA. The designed TA can achieve a high taper efficiency due to the multi-array sources and the compactness of the partial H-plane waveguide. Moreover, the proposed TA can inherently have a high spillover efficiency because the frequency selective surface (FSS) for beamforming is located just above the radiating slot. The FSS with a transmission phase variation of 2π is designed by a square patch array and used to manipulate the wave-front of the transmitted electromagnetic wave instead of a complicated feed network and phase shifters. To verify its beamforming characteristic, three types of FSSs to operate a forming angle of −40°, −20°, 0°, +20°, and +40° are designed at 12 GHz. The distance between the FSS and the slot array antenna is 0.1λ0, and the aperture efficiency is measured to be about 69%. The measured results, such as the reflection coefficient and the far-field radiation pattern, are in good agreement with the simulated results. From the measured results, the proposed TA is confirmed to have good beamforming characteristics and high aperture efficiency.
Adherent-invasive Escherichia coli (AIEC) has been reported as associated with the pathogenesis of inflammatory bowel disease (IBD). We aimed to investigate the characteristics of mucosa-associated ...E. coli and the clinical significance of AIEC in Korean IBD patients. E. coli strains were isolated from the mucosal tissues of 18 Crohn's disease (CD) patients, 24 ulcerative colitis (UC) patients, and 9 healthy controls (HC). Adhesion, invasion, and survival assays were performed to evaluate phenotypic features of E. coli isolates and to identify AIEC. The presence of virulence genes and cytokine expression were examined using PCR. In addition, data on IBD-related hospitalization were collected. A total of 59 E. coli strains were isolated (25 from CD, 27 from UC, and 7 from HC). The average levels of adhesion, invasion, and survival were higher in E. coli strains from IBD patients than those from HC (adhesion: 1.65 vs. 0.71, p = 0.046; invasion: 1.68 vs. 0.52, p = 0.039; survival: 519.55 vs. 47.55, p = 0.363). Prevalence of AIEC in HC, CD and UC patients was 22.2%, 38.9% and 37.5%, respectively. E. coli isolates from IBD patients had various virulence genes and were associated with increased expression of TNF-α and IL-17. IBD-related hospitalization within 3 years was 18.8% in patients with AIEC and 11.5% in patients without AIEC. E. coli strains from IBD patients showed high levels of adhesion, invasion, and survival. AIEC strains were identified in both CD and UC patients at a similar rate. AIEC may be associated with sustaining inflammation in the pre-existing inflammatory mucosa.
Machine vision-based intelligent applications that analyze video data collected by machines are rapidly increasing. Therefore, it is essential to efficiently compress a large volume of video data for ...machine consumption. Accordingly, the Moving Picture Experts Group (MPEG) has been developing a new video coding standard called Video Coding for Machines (VCM), aimed at video consumed by machines rather than humans. Recently, studies have demonstrated that multi-scale feature compression (MSFC)-based feature compression methods significantly improve the performance of MPEG-VCM. This paper proposes an efficient MSFC (eMSFC) method with quantization parameter (QP)-adaptive feature channel truncation. The proposed eMSFC incorporates an MSFC network with a selective learning strategy (SLS) and Versatile Video Coding (VVC)-based compression. The SLS extracts a single-scale feature from the input image, arranged in order of channel-wise importance. The size of the single-scale feature is adaptively adjusted by truncating the feature channels according to the QP. The truncated feature is efficiently compressed using VVC. Compared to the VCM feature anchor, the experimental results reveal that the proposed method provides a 98.72%, 98.34%, and 98.04% Bjontegaard delta rate gain for machine vision tasks of instance segmentation, object detection, and object tracking, respectively. The proposed method performed best among the "Call for Evidence" response technologies in MPEG-VCM.
A symmetrical metal‐rimmed mobile antenna, which is designed to be separated into two antennas covering different bands, is proposed for penta‐band in this letter. The proposed antenna consists of a ...gap‐coupled quarter wavelength loop antenna to reduce the length of an antenna and a decoupling network of 90° delay line to improve an isolation in the low band. Its resonant frequencies in low and high band can be controlled by the length of a feed line and a lumped series inductor, respectively. Since the slit of the metal rim is located at the center of the phone, the designed metal‐rimmed antenna could be less affected by the hand compared to the case where the slit is located on the side of the phone. To verify the performance, we have simulated and measured the characteristics of the proposed antenna without and with the decoupling network such as reflection coefficients, far‐field radiation patterns, and total efficiencies. Good agreement between the simulated and measured results is obtained.
A vertical monopole antenna having a directional radiation pattern is proposed in this paper. The proposed monopole antenna is located vertically on the half‐and‐half finite ground plane of perfect ...magnetic conductor (PMC) and perfect electric conductor (PEC). The ground dimension is set to be 1λ0. In case of the conventional monopole antenna, the surface currents on a ground plane are cancelled out because of the symmetrical ground with respect to the monopole. However, the surface currents of the presented monopole antenna are not cancelled out due to an asymmetrical ground and flows in one direction, so that the electromagnetic (EM) wave of an antenna does not radiate omni‐directionally but directionally. In this paper, a corrugated soft surface is employed to realize the PMC ground. The measured peak gain and the 10 dB bandwidth are measured to be 4.5 dBi and about 20% at the resonant frequency of 2.4 GHz, respectively.
A dual band omnidirectional circularly polarized (CP) antenna is presented based upon new concept of combining two orthogonal modes of epsilon‐zero resonance (EZR) and mu‐zero resonance (MZR) in this ...article. The antenna has the CP characteristic by two circularly ring‐structured double negative (DNG) transmission lines. One DNG transmission line has higher frequencies of EZR and lower frequency of MZR while the other DNG transmission line has higher frequencies of MZR and lower frequency of EZR. The EZR and MZR modes at the same frequency have a vertical and a horizontal polarization with 90° phase difference, respectively. In the EZR mode, a vertical polarization is generated like an electric monopole so that the EZR antenna radiates omnidirectionally. The MZR antenna makes a horizontal polarization by the circular ring current like a magnetic dipole loop which also radiates omnidirectionally. The analysis and design of the antenna are performed according to theory and simulation based on a dispersion diagram and E‐field distribution. Finally, the reasonable performances of the antenna such as a reflection coefficient, a CP gain, an axial ratio, and a far‐field radiation pattern are obtained in dual band.
A novel design method of simultaneous beam forming and focusing using a checkerboard anisotropic surface is proposed and verified in this paper. The proposed multibeam control regardless of far and ...near regions can easily be achieved through a rearrangement of the checkerboard structure. The unit cell of the utilized anisotropic surface consists of two identical metallic structures divided by a dielectric material. When the EM wave with a circular polarization (CP) is incident on the unit cell, the maximum transmission phase variation of the unit cell is 360 degrees by half rotation of the unit cell. A microstrip patch antenna with trimmed corners is used to launch the CP wave and the distance between the microstrip patch antenna and anisotropic surface is about 2 wavelengths considering the optimized spillover and taper efficiencies. After designing each anisotropic surface for beam forming and focusing, the unit cells of the surface are rearranged in the form of a checkerboard. The feasibility of the proposed method is confirmed by full-wave simulation and measurement for anisotropic surface with a beam forming angle of 30 degrees and beam focusing point 60 mm away from center at 5.8 GHz. The forming angle and focal length are simulated and measured to be 28 degrees and about 65 mm, respectively.
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