Trust-region optimization of all-pass filter for compensation of ionospheric dispersion effects on wideband GNSS signals

Ionospheric dispersion causes severe distortions and ranging performance degradations of wideband global navigation satellite system (GNSS) signals. To compensate the non-linear and asymmetrical group delay of the dispersive ionosphere, an all-pass filter in the form of cascaded biquad sections was proposed in our previous study. On this basis, this paper develops an optimal delay-equalization all-pass filter by using the trust-region algorithm to construct the desired group delay and improve the fitting accuracy. The simulation results of the AltBOC(15,10) signal performance demonstrate that the proposed design is more accurate for distortion compensation and thus more effective for ranging bias mitigation than the previous approach.