Marine controlled-source electromagnetics (MCSEM) is an effective method to map the spatial distribution of gas hydrate and calculate gas hydrate saturation. An MCSEM survey is conducted in the Lingnan low uplift (LNLU), Qiongdongnan Basin (QDNB), South China Sea (SCS), and then the measured data are processed to obtain the geoelectric structure. The estimated gas hydrate stability zone (GHSZ) ranges from 0 to 320 mbsf, and shallow high-conductive sediments serving as gas hydrate caps are at depths ranging from 0 to 100 mbsf (meters below the seafloor). The 2D resistivity model reveals multiple high-resistivity bodies at depths ranging from 100 to 320 mbsf, and BSRs are at depths of 240 mbsf to 280 mbsf, indicating a transversely uneven gas hydrate reservoir in the study area. Moreover, two high-resistivity bodies are detected beneath the GHSZ, implying the presence of potential gas transport pathways. The gas hydrate saturation with a variation of 0–68.4% is calculated using the MCSEM resistivity and Archie’s law. According to the resistivity model and geological data, the transversely uneven gas hydrate reservoir may be associated with multiple gas sources, including shallow biogenic gas and deep pyrolytic gas. The shallow biogenic gas is transported to the GHSZ via short-distance migration and free diffusion, and the deep pyrolytic gas is transported to the GHSZ via two microcracks. In addition, this case emphasizes that the dynamic accumulation of gas hydrate is an important factor causing reservoir heterogeneity.

Time-domain induced polarization (TDIP) measurement is seriously affected by power line interference and other field noise. Moreover, existing TDIP instruments generally output only the apparent chargeability, without providing complete secondary field information. To increase the robustness of TDIP method against interference and obtain more detailed secondary field information, an improved dataprocessing algorithm is proposed here. This method includes an efficient digital notch filter which can effectively eliminate all the main components of the power line interference. Hardware model of this filter was constructed and Vhsic Hardware Description Language code for it was generated using Digital Signal Processor Builder. In addition, a time-location method was proposed to extract secondary field information in case of unexpected data loss or failure of the synchronous technologies. Finally, the validity and accuracy of the method and the notch filter were verified by using the Cole-Cole model implemented by SIMULINK software. Moreover, indoor and field tests confirmed the application effect of the algorithm in the fieldwork.

This paper presents a novel design of compact orthogonally polarized on-chip antenna to realize 300 GHz full-duplex communication system with high isolation. It consists of a dipole antenna for horizontal polarization and a disk-loaded monopole antenna for vertical polarization. They are in good cross-polarization state with more than 90 dB of self-interference suppression and then can be used to achieve good isolation between transmitting and receiving antennas. In addition, two dual-polarized antennas have been adopted in two separated transceivers to study their isolation performance. Furthermore, this compact antenna only occupies an active area of 390 μm × 300 μm × 78 μm and can be used for multiple-input multiple-output application as well.

A fluxgate is a device that has important applications in weak magnetic field measurements. Compared with the second harmonic mode, the orthogonal fundamental mode fluxgate exhibits a better performance in terms of lower noise and wider bandwidth, making it popular among researchers in this field. An amorphous wire is a vital part of any orthogonal fundamental mode fluxgate, and its excitation parameters determine the performance of the sensor (especially the noise level). For different structures and sizes of amorphous wires as probes, the optimal excitation parameters of orthogonal fundamental mode fluxgate are different. The conventional excitation module development scheme suffers from problems such as a complicated structure and low flexibility. To overcome these problems, a simple, compact, and effective excitation module is proposed, which is composed of a waveform generator, signal conditioning circuit, and voltage-controlled current source. Owing to the high flexibility, the frequency of the direct digital frequency synthesis is fully programmable. We tested the design performance indexes of key parameters, such as excitation signal waveform, amplitude, noise level, and bandwidth. The excitation current noise level is as low as 12.42 nA/sqrt (Hz) @ 20 kHz without I_ac and 17.35 nA/sqrt (Hz) @ 20 kHz with I_ac. The effective bandwidth of the alternating current output is 10–200 kHz. Moreover, a system test platform was developed, and this module was used to analyze the variation trend of the noise level of the fluxgate sensor under different excitation parameters (such as I_ac, I_dc, and excitation current frequency). It has been proved that the excitation module helps in effectively and quickly selecting the best excitation parameters to improve the performance of orthogonal fundamental mode fluxgates and shorten their development cycle.