Performance Analysis of Doppler Aided Tracking Loops in Modernized GPS Receivers
The GPS modernization program deploys new generations of satellites designated Block IIR-M, Block IIF and Block III-A, equipped to transmit multiple civil signals. The coexistence of multiple civilian signals in a GPS receiver has been a focus in recent research activities. In the literature to date, correlator outputs of individual channels are combined in ways either to increase the power available for processing or to reduce the error in tracking measurements. These combinations are typically made at the discriminator level, after the discriminator or after the loop filter. The combinations have been considered both for channels operating on the same carrier frequency (e.g. data and pilot channels of L5) as well as channels across different carrier frequencies. In a modernized GPS receiver, tracking multiple civil signals, the relationship between Doppler frequencies (proportional to the corresponding carrier frequencies) of all signals is known and therefore Doppler estimates of one PLL can be utilized by another PLL tracking a different frequency. While such benefits are conventionally achieved through ultra-tight GPS/INS coupling, this paper presents performance analysis of a Doppler-aided tracking loop architecture, where the Doppler assistance is obtained from another loop in the same receiver. L1 C/A and L2C are the two civil signals selected for the analysis, because this pair of signals will be available long before any other combination. The analysis, however, is relevant to any pair of signals from a single satellite. The L2C carrier, having the pilot channel and relatively slower dynamics, is used as aiding source in the considered arrangement. The L2C PLL, operated with a wide loop bandwidth, absorbs the dynamic stress and provides Doppler estimates to the L1 PLL (affected by wide-band interference) operating at narrow-band. The tracking error associated with such collaboration between two tracking loops is analyzed. It is shown that a 7 dB-Hz RFI margin (equivalent to that achieved with a moderate quality inertial sensor), can be achieved through the local Doppler-assistance.
Performance of INS-aided tracking loop for GPS high dynamic receiver
The dominant sources of phase error in a GPS INS-aided PLL consist of the statistical part and the deterministic part, it is same to a GPS INS-aided FLL. The effects of two type sources are quantified and error models are built to evaluate tracking performance. The results of this research show that the INS-aided FLL performs better than the INS-aided PLL. The minimum C/N0 is 27.7dB-Hz for the third order PLL, 25dB-Hz for the INS-aided second order PLL and 17.1B-Hz for the INS-aided second order FLL(IFLL2) when the maximum value of line-of-sight jerk is 10g/s, so IFLL2 is more suitable for high dynamic receiver.
Reflection coefficient of inhomogeneous anisotropic impedance plane
Solved the problem of constructive synthesis of an inhomogeneous anisotropic impedance plane reflecting a homogeneous plane wave in two different preset directions on a matched and cross polarization. Obtained the reflection coefficients and expressions for the scattering diagrams. The impedance is implemented by the frequent array of orthogonal strips. The law of distribution of the reactance was obtained in an explicit form. It is shown that for arbitrarily given (unequal) directions of reflections on matched and cross polarizations, the orientation of the reactance strips turns out to be variable along the plane. Formulated restrictions on class of implemented scattering diagrams. Shown the results of numerical studies.