In any radio navigation and radio communication system, receivers can be equipped with multiple antennas. By properly weighting and combining the different antenna signals after A/D conversion the wanted signals can be amplified and interfering signals suppressed (digital beamforming). But through the process of beamforming the information about the relative signal delays between the antenna elements is lost. In a multiantenna receiver the signals form multiple antennas are weighted and combined only after the phase discriminators (i.e. error detectors). This allows an estimation of the receiver platform attitude in parallel with the usual signal tracking. Due to the nonlinear relationship between the measurements and the attitude parametrization the problem of attitude estimation in the multiantenna tracking is non convex. A global convergence is achieved by combining a divergence detection together with a reinitialization scheme. Although the multiantenna tracking combines the measurements of multiple antennas in digital domain, it is inherently different from traditional digtial beamforming. The price the receiver has to pay for the attitude estimation is a reduced capability of amplifying and suppressing directive signals. But still a suppression of interfering signals is achieved. Simulation results indicate a fast convergence of the loop in parallel with a robust tracking lock. It can be concluded that multiantenna tracking is a valuable tool for jointly estimating the receiver platform and tracking the satellite signals without the need for several receivers.
