A Summary of Attenuation Measurements from Borehole Recordings of Earthquakes: The 10 Hz Transition Problem

1998 ◽  
pp. 475-487 ◽  
Author(s):  
Rachel E. Abercrombie
Keyword(s):  
Transition Problem

scholarly journals A BeiDou Signal Acquisition Approach Using Variable Length Data Accumulation Based on Signal Delay and Multiplication

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1309 ◽  
Author(s):  
Menghuan Yang ◽  
Hong Wu ◽  
Qiqi Wang ◽  
Yingxin Zhao ◽  
Zhiyang Liu
Keyword(s):  
Doppler Frequency ◽  
Variable Length ◽  
Signal Acquisition ◽  
Noise Power ◽  
Signal Delay ◽  
Coherent Integration ◽  
Transition Problem ◽  
Data Accumulation ◽  
Length Data

The secondary modulation with the Neumann-Hoffman code increases the possibility of bit sign transition. Unlike other GNSS signals, there is no pilot component for synchronization in BeiDou B1/B3 signals, which increases the complexity in acquisition. A previous study has shown that the delay and multiplication (DAM) method is able to eliminate the bit sign transition problem, but it only applies to pretty strong signals. In this paper, a DAM-based BeiDou signal acquisition approach, called variable length data accumulation (VLDA), is proposed to acquire weak satellite signals. Firstly, the performance of DAM method versus the different delays is analyzed. The DAM operation not only eliminates bit sign transition, but it also increases noise power. Secondly, long-term signal is periodically accumulated to improve signal intensity in order to acquire weak signals. While considering the Doppler frequency shift of ranging codes, the signal length must be compensated before accumulating long-term signal. Finally, the fast-Fourier-transform based parallel code phase algorithm are used for acquisition. The simulation results indicate that the proposed VLDA method has better acquisition sensitivity than traditional non-coherent integration method under the same calculation amount. The VLDA method only requires approximately 27.5% of calculations to achieve the same acquisition sensitivity (35 dBHz). What is more, the actual experimental results verify the feasibility of the VLDA method. It can be concluded that the proposed approach is an effective and feasible method for solving the bit sign transition problem.

scholarly journals Analysis of GNSS Signal Acquisition Methods for the Bit-Transition Problem for a Single Code Period

2013 ◽  
Vol 56 (1) ◽  
pp. 31-41 ◽  
Author(s):  
Sanghoon JEON ◽  
Hyoungmin SO ◽  
Ghangho KIM ◽  
Changdon KEE ◽  
Kiho KWON ◽  
...  
Keyword(s):  
Signal Acquisition ◽  
Transition Problem
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