Propagation measurements and analysis on MF and HF bands in urban areas in The Netherlands

Using a new propagation measurement set-up, which produces a high number of data, enabling a proper statistical analysis, and resulting in very concise results, propagation measurements were performed and analized at 16 residential locations in The Netherlands in the frequency range from 1.8 to 28 MHz. In the whole frequency range the propagation loss appear to be higher than according the International Telecommunication Union ground-wave propagation model might be expected. Also typical characteristics of that model are not present, but instead the propagation shows a constant roll-off in dBs per decade, which slope is increasing with frequency. A regression curve could be established, and constants filled in. This statistical information may be used for building an accumulation model to lay a causality between source powers, source densities, and local Man-Made Noise levels.<br><br>

Propagation measurements and analysis on MF and HF bands in urban areas in The Netherlands

Using a new propagation measurement set-up, which produces a high number of data, enabling a proper statistical analysis, and resulting in very concise results, propagation measurements were performed and analized at 16 residential locations in The Netherlands in the frequency range from 1.8 to 28 MHz. In the whole frequency range the propagation loss appear to be higher than according the International Telecommunication Union ground-wave propagation model might be expected. Also typical characteristics of that model are not present, but instead the propagation shows a constant roll-off in dBs per decade, which slope is increasing with frequency. A regression curve could be established, and constants filled in. This statistical information may be used for building an accumulation model to lay a causality between source powers, source densities, and local Man-Made Noise levels.<br><br>

Optimal Transceiver Distance of Controlled-source Audio-frequency Magnetotelluric Sounding Method

Currently, the use of Cagniard apparent resistivity and phase is still the main method and means to process and interpret controlled-source audio-frequency magnetotelluric (CSAMT) sounding data. The CSAMT data must meet the conditions in the far zone to use the magnetotelluric (MT) sounding inversion interpretation method. The conditions in the far zone are directly related to transceiver distance; Hence, the distance measured by the CSAMT method is directly related to the reliability and credibility of the data. In this study, based on the formation wave and ground wave of the analytical expression for the electric field in a uniform half-space condition, the response laws of the formation wave and the ground wave are analyzed. After rigorous mathematical derivation, the formula for determining the optimal transceiver distance of the CSAMT is obtained, and the steps for using this formula in practical application are given. The actual field application verifies the rationality of the derived formula. This study provides a reference for the design of a CSAMT field source, and effectively guides the determination of CSAMT transceiver distance in the field.

Multi-Channel Data Acquisition Card under New Acquisition and Transmission Architecture of High Frequency Ground Wave Radar

It is known that the data acquisition and processing system plays an important role in radar target detection system. In order to meet the requirements of real-time processing and accurate transmission of echo signals in high-frequency ground-wave radar (HFGWR) systems, a new acquisition and transmission framework utilizing the designed acquisition card based on the PCIe (peripheral component interconnect express) has been designed and is presented in this paper. The Xilinx FPGA (Field-Programmable Gate Array) chip Kintex7-XC7K325T is adopted as a hardware carrier in acquisition card. The hardware’s composition, analog front-end circuit, the DMA (Direct Memory Access) transmission, FPGA structure, ADC (Analog-to-Digital Converter) chip, and performance test of this card are showed and discussed. Currently, the acquisition card has been accomplished and applied in the practical system of HFGWR.