The traditional coherent acquisition techniques used for GPS L1 C/A signal acquisition cannot directly be applied to acquire BeiDou D1 signal transmitted from IGSO and MEO satellites due to the presence of NH code modulation. The presence of NH code modulation on top of navigation data bits increases the final data bit rate from 50 bps to 1 kHz. Therefore, the sign changes for BeiDou D1 signal occur more frequently than that of a GPS L1 C/A signal due to the presence of NH code. This eventually means that an acquisition scheme for BeiDou D1 signal with more than 1 ms coherent integration period may appear dangerous, if sign information is not consistently preserved. In view of this sign transition problem, a novel acquisition technique is implemented for BeiDou D1 signal that preserves the total useful signal energy in the presence of a sign transition, and hence, makes a correct acquisition decision on the presence of the satellite, and its carrier Doppler and the corresponding code phase. The working principle of the novel BeiDou D1 acquisition technique, first introduced in [ 9], is also depicted in the following. Step 1:

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Conflicts of Interest

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