scholarly journals Improving the iGNSS-R Ocean Altimetric Precision Based on the Coherent Integration Time Optimization Model

2021 ◽  
Vol 13 (22) ◽  
pp. 4715
Author(s):  
Xuezhi Sun ◽  
Wei Zheng ◽  
Fan Wu ◽  
Zongqiang Liu
Keyword(s):  
Optimization Model ◽  
Sea Surface ◽  
Integration Time ◽  
Average Deviation ◽  
Noise Interference ◽  
Coherent Integration ◽  
Time Optimization ◽  
Ocean Altimetry ◽  
Coherent Integration Time ◽  
Along Track

Improving the altimetric precision under the requirement of ensuring the along-track resolution is of great significance to the application of iGNSS-R satellite ocean altimetry. The results obtained by using the empirical integration time need to be improved. Optimizing the integration time can suppress the noise interference from different sources to the greatest extent, thereby improving the altimetric precision. The inverse relationship between along-track resolution and signal integration time leads to the latter not being infinite. To obtain the optimal combination of integral parameters, this study first constructs an analytical model whose precision varies with coherent integration time. Second, the model is verified using airborne experimental data. The result shows that the average deviation between the model and the measured precision is about 0.16 m. The two are consistent. Third, we apply the model to obtain the optimal coherent integration time of the airborne experimental scenario. Compared with the empirical coherent integration parameters, the measured precision is improved by about 0.1 m. Fourth, the verified model is extrapolated to different spaceborne scenarios. Then, the optimal coherent integration time and the improvement of measured precision under various conditions are estimated. It was found that the optimal coherent integration time of the spaceborne scene is shorter than that of the airborne scene. Depending on the orbital altitude and the roughness of the sea surface, its value may also vary. Moreover, the model can significantly improve the precision for low signal-to-noise ratios. The coherent integration time optimization model proposed in this paper can enhance the altimetric precision. It would provide theoretical support for the signal optimization processing and sea surface height retrieval of iGNSS-R altimetry satellites with high precision and high along-track resolution in the future.

scholarly journals Joint Acquisition Estimator of Modern GNSS Tiered Signals Using Block Pre-Correlation Processing of Secondary Code

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2965
Author(s):  
Jiří Svatoň ◽  
František Vejražka
Keyword(s):  
Search Algorithm ◽  
Global Navigation Satellite Systems ◽  
Integration Time ◽  
Zero Padding ◽  
Satellite Systems ◽  
Coherent Integration ◽  
Correlation Processing ◽  
Single Block ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

Objective is a joint primary and secondary code (SC) acquisition estimator of tiered Global Navigation Satellite Systems (GNSS) signals. The estimator is based on the Parallel Code Search algorithm (PCS) combined with the Single-Block-Zero-Padding (SBZP) and the Pre-correlation Coherent Accumulation (PCA). The PCA realizes the extension of the coherent integration time in front of the PCS. However, the PCS with the SBZP and the PCA is affected by a navigation/SC bit transition problem due to its cyclic property of a computed Cross-Ambiguity Function (CAF). This CAF is degraded by diverse parasitic fragments and is not directly applicable for an acquisition. A novel analysis of this mechanism and its impact is presented. Then, the proposed modified SBZP (mSBZP) modified PCA (mPCA) PCS estimator is constructed, which does not degrade the CAF. The mSBZP allows the use of the PCS algorithm in the presence of SC bit transition, while the mPCA decreases the number of PCS algorithm calculations by a factor of SC chip count due to SC pre-correlation processing. The algorithm has the same detection performance in comparison with conventional Double-Block-Zero-Padding (DBZP). However, it allows using the PCS of half-length with longer latency up to a factor of SC chip count.

Multiaircraft formation identification for narrowband coherent radar in a long coherent integration time

2015 ◽  
Vol 51 (3) ◽  
pp. 2121-2137 ◽  
Author(s):  
Shi-bao Peng ◽  
Jia Xu ◽  
Xiang-gen Xia ◽  
Feng Liu ◽  
Teng Long ◽  
...  
Keyword(s):  
Integration Time ◽  
Coherent Integration ◽  
Coherent Integration Time ◽  
Coherent Radar

Coherent integration time limit of a mobile receiver for indoor GNSS applications

GPS Solutions ◽  
2011 ◽  
Vol 16 (2) ◽  
pp. 157-167 ◽  
Author(s):  
Ali Broumandan ◽  
John Nielsen ◽  
Gérard Lachapelle
Keyword(s):  
Time Limit ◽  
Integration Time ◽  
Coherent Integration ◽  
Coherent Integration Time ◽  
Mobile Receiver

scholarly journals Signal-to-Noise Ratio Analyses of Spaceborne GNSS-Reflectometry from Galileo and BeiDou Satellites

2021 ◽  
Vol 14 (1) ◽  
pp. 35
Author(s):  
Yang Nan ◽  
Shirong Ye ◽  
Jingnan Liu ◽  
Bofeng Guo ◽  
Shuangcheng Zhang ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
Integration Time ◽  
Navigation Satellite ◽  
Signal To Noise ◽  
Coherent Integration ◽  
Global Navigation ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) technology has made considerable progress with the increasing of GNSS-R satellites in orbit, the improvements of GNSS-R data processing technology, and the expansion of its geophysical applications. Meanwhile, with the modernization and evolution of GNSS systems, more signal sources and signal modulation modes are available. The effective use of the signals at different frequencies or from new GNSS systems can improve the accuracy, reliability, and resolution of the GNSS-R data products. This paper analyses the signal-to-noise ratio (SNR) of the GNSS-R measurements from Galileo and BeiDou-3 (BDS-3) systems, which is one of the important indicators to measure the quality of GNSS-R data. The multi-GNSS (GPS, Galileo and BDS-3) complex waveform products generated from the raw intermediate frequency data from TechDemoSat-1 (TDS-1) satellite and Cyclone Global Navigation Satellite System (CYGNSS) constellation are used for such analyses. The SNR and normalized SNR (NSNR) of the reflected signals from Galileo and BDS-3 satellites are compared to these from GPS. Preliminary results show that the GNSS-R SNRs from Galileo and BDS-3 are ∼1–2 dB lower than the GNSS-R measurements from GPS, which could be due to the power of the transmitted power and the bandwidth of the receiver. In addition, the effect of coherent integration time on GNSS-R SNR is also assessed for different GNSS signals. It is shown that the SNR of the reflected signals can be improved by using longer coherent integration time (∼0.4–0.8 dB with 2 ms coherent integration and ∼0.6–1.2 dB with 4 ms coherent integration). In addition, it is also shown that the SNR can be improved more efficiently (∼0.2–0.4 dB) for reflected BDS-3 and Galileo signals than for GPS. These results can provide useful references for the design of future spaceborne GNSS-R instrument compatible with reflections from multi-GNSS constellations.

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