RECONSTRUCTION OF THE SPATIAL SPECTRUM OF TROPOSPHERIC IRREGULARITIES USING THE CORRELATION FUNCTIONS OF THE AMPLITUDE FLUCTUATIONS

This paper proposes underwater acoustic time delay estimation based on the envelope differences of correlation functions (EDCF), which mitigates the delay estimation errors introduced by the amplitude fluctuations of the correlation function envelopes in the traditional correlation methods (CM). The performance of the proposed delay estimation method under different time values was analyzed, and the optimal difference time values are given. To overcome the influences of digital signal sampling intervals on time delay estimation, a digital time delay estimation approach with low complexity and high accuracy is proposed. The performance of the proposed time delay estimation was analyzed in underwater multipath channels. Finally, the accuracy of the delay estimation using this proposed method was demonstrated by experiments.

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Anisotropy of ionospheric irregularities determined from the amplitude of satellite signals at a single receiver

Annales Geophysicae ◽

10.1007/s00585-999-0508-4 ◽

1999 ◽

Vol 17 (4) ◽

pp. 508-518 ◽

Cited By ~ 6

Author(s):

E. D. Tereshchenko ◽

B. Z. Khudukon ◽

M. O. Kozlova ◽

T. Nygrén

Keyword(s):

Large Scale ◽

Ground Level ◽

Spatial Spectrum ◽

Ionospheric Irregularities ◽

Small Scale ◽

Radio Waves ◽

Large Scale Structures ◽

F Region ◽

Amplitude Fluctuations ◽

A Chain

Abstract. A new method of determining the anisotropy parameters of small-scale irregularities in the ionospheric F region is presented and experimental results are shown. The method is based on observations of amplitude fluctuations of radio waves transmitted by satellites flying above the F region. In practice, Russian navigational satellites are used and both the amplitude and the phase of the received signal is measured on the ground level. The method determines both the field-aligned anisotropy and the field-perpendicular anisotropy and orientation of the spatial spectrum of the irregularities, assuming that the contours of constant power have an elliptic shape. A possibility of applying the method to amplitude tomography is also discussed. Using a chain of receivers on the ground level, one could locate the regions of small-scale irregularities as well as determine their relative intensities. Then the large-scale background structures could be mapped simultaneously by means of ordinary ray tomography using the phase observations, and therefore the relations of small-scale and large-scale structures could be investigated.Key words. Ionosphere (auroral ionosphere; ionospheric irregularities; instruments and techniques)

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Diagnostics of Es Layer Scintillation Observations Using FS3/COSMIC Data: Dependence on Sampling Spatial Scale

Remote Sensing ◽

10.3390/rs13183732 ◽

2021 ◽

Vol 13 (18) ◽

pp. 3732

Author(s):

Lung-Chih Tsai ◽

Shin-Yi Su ◽

Chao-Han Liu ◽

Harald Schuh ◽

Jens Wickert ◽

...

Keyword(s):

Spatial Scale ◽

Fresnel Zone ◽

Signal Amplitude ◽

Spatial Spectrum ◽

Density Fluctuations ◽

Wave Number ◽

Scintillation Index ◽

Amplitude Fluctuations ◽

Electron Density Fluctuations ◽

Sporadic E

The basic theory and experimental results of amplitude scintillation from GPS/GNSS radio occultation (RO) observations on sporadic E (Es) layers are reported in this study. Considering an Es layer to be not a “thin” irregularity slab on limb viewing, we characterized the corresponding electron density fluctuations as a power-law function and applied the Ryton approximation to simulate spatial spectrum of amplitude fluctuations. The scintillation index S4 and normalized signal amplitude standard deviation S2 are calculated depending on the sampling spatial scale. The theoretical results show that both S4 and S2 values become saturated when the sampling spatial scale is less than the first Fresnel zone (FFZ), and S4 and S2 values could be underestimated and approximately proportional to the logarithm of sampled spatial wave numbers up to the FFZ wave number. This was verified by experimental analyses using the 50 Hz and de-sampled FormoSat-3/Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) GPS RO data in the cases of weak, moderate, and strong scintillations. The results show that the measured S2 and S4 values have a very high correlation coefficient of >0.97 and a ratio of ~0.5 under both complete and undersampling conditions, and complete S4 and S2 values can be derived by dividing the measured undersampling S4 and S2 values by a factor of 0.8 when using 1-Hz RO data.

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