GPS World, August 2015
RECEIVER TECNOLOGY Signal Quality and Authentication FIGURE 8 Multipath error envelopes for various rising edge based coherent early late code discriminator functions FIGURE 6 illustrates the rising edge discriminator functions after bias compensation FIGURE 7 shows the fully calibrated Early Late rising edge tracking code discriminators FIGURE 8 illustrates the multipath error envelopes for the rising edge based coherent code discriminators The performance of these discriminators is similar to the traditional Early Late discriminators for the same correlator spacings This result is consistent with the theoretical FIGURE 9 Rising edge coherent double delta code discriminator function Inner correlator spacing is 0017 C A chips FIGURE 10 Rising edge coherent double delta code discriminator function Markers illustrate non linearity bounds for code multipath As shown in Figure 4 the edge tracking discriminators described in Equations 2 and 3 that are based on Early Late bin spacings can be combined to obtain edge tracking double delta discriminators Double delta discriminators provide significantly improved multipath performance In general the edge tracking double delta discriminator for inner correlator spacing d is formed by the linear combination of two early late edge tracking discriminators as follows 4 Scale factor γ is estimated such that overall multipath error is minimized according to a given design criteria FIGURE 9 illustrates the double delta rising edge discriminator with inner spacing of 0017 chips This discriminator has a pull in range of approximately 001 C A chips FIGURE 10 illustrates the non linearity of this double delta discriminator September SAVE 16 EARLY com REGISTER increase expouav Prices www Surveying Mapping Civil Infrastructure Mining Construction Law Enforcement Emergency Response Search and Rescue SAR Process Power Utilities Precision Agriculture GPS World August 2015 www gpsworld com 42
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