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Slot antenna based on microstrip line and waveguide is a popular design for future 5G antennas. To improve performance of slot antenna, a high‐gain wideband slot antenna based on integrated substrate gap waveguide (ISGW) is presented, in which a stepped impedance feeding line is adopted to broaden bandwidth, and ISGW is used to increase gain. First, the transmission characteristics and the effective relative permittivity of ISGW is discussed and calculated, with operation band from 25 to 45 GHz. The antenna has a passband of 24.9–38.1 GHz, that is, almost Ka band, and an average gain of ~9 dB. Further, bandstop filtering (BSF) characteristic is introduced in the above wideband antenna to achieve filtering antennas for 5G millimeter‐wave (mm‐wave) bands of 24.75–27.5 GHz for China, and 26.5–29.5, 27.5–28.5, and 37–40 GHz for n257, n258, and n260 of 5G new‐radio (NR). The BSF is obtained by etching U‐shaped CSRR on feeding patch of the antenna. First‐ and second‐order BSF are achieved by etching first and second U‐shaped CSRR on the antenna feeding patch, respectively, thus correspondingly one bandstop resonance at 34.6 GHz, and two bandstop resonances at both 32.5 and 34 GHz are obtained. It is found that the passband performance is unchanged, but the stopband radiation drops sharply at the boresight direction. The three antennas (wideband, and first‐ and second‐order BSF antennas) proposed are all fabricated and verified. [ABSTRACT FROM AUTHOR]

Very low-frequency (VLF) communication signals of 15–25 kHz contaminate the transient electromagnetic (TEM) data. The notch filter or Butterworth filter is commonly used to suppress VLF noise in addition to synchronous detection of TEM data such as gating and stacking, while also introducing the TEM signal distortion around the VLF band. We propose a B-spline gating, which suppresses the VLF noise while integrating TEM data in the gate interval without any extra filter. B-spline gating is designed to ensure that the zeros of its amplitude frequency response (AFR) are located around VLF frequencies by optimizing the knot vector of the B-spline. It is available for various VLF frequencies. We apply B-spline gating to synthetic TEM data compared with rectangular gating and full-tapered gating, the AFRs of B-spline and full-tapered gating are 25 dB lower at high frequencies than rectangular gating, and the amplitude of B-spline is more reduced at VLF frequency than full-tapered gating; the standard error of the B-spline gates is reduced by >15% compared to the full-tapered gates. The field example from a TEM survey in the Inner Mongolia Autonomous Region of China shows that the amplitude of B-spline gating frequency response in late gates is reduced by about 20 dB at 24.1 kHz VLF than that of full-tapered gating, and the standard error is lower. It is concluded that B-spline gating can suppress VLF noise while following the normal decay of TEM signal without distortion. [ABSTRACT FROM AUTHOR]

This article presents the design and performance of a terahertz on-chip coupled-grounded coplanar waveguide (GCPW) power combiner using a 50ÎĽm-thick InP process. The proposed topology uses two coupled-GCPW lines at the end of the input port to substitute two quarter-wavelength GCPW lines,which is different from the conventional Wilkinson power combiner and canavailably minimize the coverage area. According to the results obtained, forthe frequency range of 210â€"250z, the insertion losses for each two-waycombiner and four-way combiner were lower than 1.05 dB and 1.35 dB,respectively, and the in-band return losses were better than 11 dB. Moreover,the proposed on-chip GCPW-based combiners achieved a compromise in low-loss, broadband, and small-size, which can find wide applications in terahertz bands, such as power amplifiers and signal distribution networks. [ABSTRACT FROM AUTHOR]

In the coalbed methane (CBM) exploration and development, microwave treatment technology can be used to improve the reservoir permeability and enhance coalbed methane recovery. In this paper, the mechanism of microwave heating on micro-cracks in coal and rock is studied. And to research the interactions between microwave and coal, a mathematical model of electromagnetic field and heat transfer in solid coupling is established. Combined with numerical simulation and experimental research, the electromagnetic field distribution and the temperature changing law in coal samples collected from Ordos basin of China during microwave heating process are analyzed. Through the comparisons of appearance identification and internal CT scanning before and after microwave treatment, there are a large number of obvious cracks generated by microwave heating on the surface and inside of coal samples. Three main generation mechanisms of micro-cracks in coal and rock are obtained by SEM analysis. Finally, a new microwave heating technology for CBM recovery is proposed and the structure of waveguide antennas (coaxial) for heating is designed. The simulation results show that the reservoir temperature has been greatly improved and the temperature change rates in the top half of the reservoir are larger which can easily cause the generation of micro-cracks. • Microwave has more significant effect on lower rank coals than higher rank coals. • Cracks and permeability increase with the increase of microwave heating time. • The mechanism of micro-cracks generated by microwave heating is studied by SEM. • A microwave heating technology for CBM recovery is designed and simulated. [ABSTRACT FROM AUTHOR]