Receiver Differential Code Biases of GLONASS FDMA Signals with the Same Frequency Slot

At present, many researchers have discovered the effect of different receiver bias in GPS signals for different receivers. These differences cannot be explained by the group delay time in the receiver circuitry. It can be explained by the influence of the navigation signal shape distortion on the bias. The effect does not appear in case of an ideal signal, but if there are some distortions - then additional differential code biases may appear, which depends on the receiver circuitry and signal processing algorithm. Thus, this additional component may change even if only the receiver firmware is changed. The article shows a similar phenomenon for GLONASS signals. The research of differential code biases for the set of different receiver models based on real GLONASS, GPS, GALILEO signals was carried out. In the case of GLONASS, pairs of navigation satellites with the same frequency slot were studied to exclude the influence of the group delay frequency dependence in the receiver circuitry. An experiment with a synthesized signal has been carried out. It was shown that signals of different navigation satellites from one simulator are identical in terms of their shape distortion, and therefore there are no significant additional differential code biases. But comparing two different simulators, the difference due to additional differential code biases when working with signals from different simulators with different distortions can be seen. It was confirmed that receiver biases depend not only on navigation signal frequency but also on its other parameters, including distortions of modulating sequence.