Analysis of the Applicable Minimum Filter Gain Roll-Off of DFMC SBAS Receiver for BDS Signals

摘要

The minimum filter gain roll-off is an important content of receiver design constraints in Dual Frequency and Multi Constellation (DFMC) Satellite-Based Augmentation System (SBAS) service standard. BDS B1C and B2a signals plan to join this service standard, and this paper studies the minimum applicable filter gain roll-off for the two signals. SBAS implementation cost by using signal quality monitoring (SQM) method to provide users sufficient protection are evaluated under two typical filter gain roll-off values of 30 dB/octave and 24 dB/octave. The results show that: for B2a signal, under both the parameter values, the user can be sufficiently protected by using only one monitoring station SQM data; for B1C signal, under 30 dB/octave and 24 dB/octave, the user can be sufficiently protected by using at least 2 and 3 monitoring station SQM data in coherent way, respectively. Considering that the SBAS service itself requires at least three monitoring stations to be visible to satellites at the same time to carry out the differential information calculation, so when filter gain roll-off parameter is not less than 24 dB/octave, the system can meet the protection of users without increasing the number of visible monitoring stations. Thus, 24 dB/octave can be used as the minimum filter gain roll-off for B1C and B2a signals. The conclusion of this paper can provide a reference for the development of DFMC SBAS receiver design constraints for B1C and B2a signals.