Extraction of Alpha transmitter signals from single-station observations using the direction-finding method

Gu, Xudong; Chen, Huan; Wang, Shiwei; Lu, Zilong; Ni, Binbin; Li, GuangJian; Cheng, Wen

doi:10.1007/s11431-021-2057-2

Cited by 6 publications

(5 citation statements)

References 30 publications

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“…The stations are distinguished based on the transmission order of the three signals. Table 1 lists the transmission frequency and sequence of signals at each station in the system [5,9]. The time taken for each station to broadcast a signal frame was 3.6 s, and each frame consisted of six time periods with a length of 600 ms [7,17].…”

Section: Signal Format For Alpha Navigation Systemmentioning

confidence: 99%

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Research on an Alpha Navigation Signal Detection Method Based on Multichannel Orthogonal Correlation

Yan,

Li,

et al. 2024

Applied Sciences

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The Alpha navigation system is the only operating radio system based on very-low-frequency (VLF) signals that can be used to research VLF navigation, timing, and ionospheric characteristics. The detection of the Alpha navigation signal is the key step in the Alpha receiver; however, the received Alpha navigation signal is susceptible to noise and mutual interference, which deteriorates signal detection performance. This paper presents a multichannel orthogonal correlation method for Alpha navigation signal detection. Once the three frequency signals of the Alpha navigation system are obtained using a notch filter, station identification is realized using a multichannel orthogonal correlation method and signal format. The selection of key parameters and the detection performance under noise and mutual interference are analyzed. This method’s detection probability exceeds 90% when the signal-to-noise ratio (SNR) is greater than −10 dB. The influence of mutual interference on the signal correlation peak is less than 1% when the signal-to-interference ratio (SIR) of the mutual interference is greater than −28 dB. The proposed method is verified using an actual signal collected using an Alpha receiver. The results show that an Alpha signal can be detected at an extremely low SNR. This method has strong practicability and satisfies the application requirements of an Alpha receiver.

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Section: Signal Format For Alpha Navigation Systemmentioning

confidence: 99%

“…The Alpha navigation system is an Omega-like ultra-long-range navigation system that was developed by the Soviet Union and put into operation in 1970. Alpha is the only VLF-based navigation system still in operation internationally, and it uses five stations to provide navigation services to its coverage area [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Research on an Alpha Navigation Signal Detection Method Based on Multichannel Orthogonal Correlation

Yan,

Li,

et al. 2024

Applied Sciences

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“…We use the VLF data collected between March and May in the year of 2022 at the Great Wall Station (GWS, 62.22 • S, 58.96 • W) in Antarctica. These data were obtained using a receiver developed by Wuhan University (WHU) and recently deployed in Antarctica [45,46]. Composed of two orthogonal magnetic loop antennae with the shape of a regular triangle [45], this system can pick up broadband electromagnetic signals with frequencies of 1-50 kHz and a sampling frequency of 250 kHz [47][48][49][50][51], which covers the frequency range of VLF transmitters that are principally used to support naval operations.…”

Section: Vlf Measurements Of Solar Flares At Gwsmentioning

confidence: 99%

Examining the Capability of the VLF Technique for Nowcasting Solar Flares Based on Ground Measurements in Antarctica

Wang,

Zhou,

et al. 2024

Remote Sensing

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Measurements of Very-Low-Frequency (VLF) transmitter signals have been widely used to investigate the effects of various space weather events on the D-region ionosphere, including nowcasting solar flares. Previous studies have established a method to nowcast solar flares using VLF measurements, but only using measurements from dayside propagation paths, and there remains limited focus on day–night mixed paths, which are important for method applicability. Between March and May of 2022, the Sun erupted a total of 56 M-class and 6 X-class solar flares, all of which were well captured by our VLF receiver in Antarctica. Using these VLF measurements, we reexamine the capability of the VLF technique to nowcast solar flares by including day–night mixed propagation paths and expanding the path coverage in longitude compared to that in previous studies. The amplitude and phase maximum changes are generally positively correlated with X-ray fluxes, whereas the time delay is negatively correlated. The curve-fitting parameters that we obtain for the X-ray fluxes and VLF signal maximum changes are consistent with those in previous studies for dayside paths, even though different instruments are used, supporting the flare-nowcasting method. Moreover, the present results show that, for day–night mixed paths, the amplitude and phase maximum changes also scale linearly with the logarithm of the flare X-ray fluxes, but the level of change is notably different from that for dayside paths. The coefficients used in the flare-nowcasting method need to be updated for mixed propagation paths.

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“…In this paper, we use the data collected using the VLF detection system developed by Wuhan University [39][40][41]. The receiver consists of two orthogonal magnetic loop antennas, set up in both East-West (EW) and North-South (NS) directions.…”

Section: Vlf Measurements and Data Processingmentioning

confidence: 99%

Automatic Detection of VLF Tweek Signals Based on the YOLO Model

Xu,

Ma,

Wang

et al. 2023

Remote Sensing

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Tweek signals are a special type of VLF (very low frequency) pulse, originally produced by lightning discharge, which becomes dispersive after repetitive bounces within the waveguide between the Earth’s surface and lower ionosphere. As such, tweek signals carry critical information about the region near the reflection height of the VLF waves, namely the D-region ionosphere. Although tweek measurements have been widely utilized in studies of the D-region ionosphere and lightning discharge, few statistical studies have been conducted, mainly due to the difficulty of manually identifying tweek signals from the enormous amount of VLF data with heavy noise. Considering the importance of tweek signals and the lack of a high-precision detection model, in this study, we propose a method to automatically and accurately pick out tweek signals from VLF measurements. This method is explicitly developed based on the you only look once (YOLO) model and a post-tracing process. Using a total of 2495 randomly selected VLF spectrogram images as the testing set, we evaluated the performance of this method. The precision and recall are found to be 92.0% and 89.2% for the first-order mode, and 97.5% and 86.7% for the first-two-order mode tweek, respectively. The time needed to process 10-s VLF measurements with a cadence of 4 μs is only 6.5 s, allowing for identifying the tweek signals from continuous VLF measurements in real time. Therefore, this method represents a reliable means to automatically detect tweek signals and enables the opportunity to statistically investigate the D-region ionosphere and lightning discharge via these signals.

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Extraction of Alpha transmitter signals from single-station observations using the direction-finding method

Cited by 6 publications

References 30 publications

Research on an Alpha Navigation Signal Detection Method Based on Multichannel Orthogonal Correlation

Research on an Alpha Navigation Signal Detection Method Based on Multichannel Orthogonal Correlation

Examining the Capability of the VLF Technique for Nowcasting Solar Flares Based on Ground Measurements in Antarctica

Automatic Detection of VLF Tweek Signals Based on the YOLO Model

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