Abstract: An observation lock detector receives I and Q correlations and measurement residuals and transforms the I and Q quadrature correlation outputs based upon computed code phase and carrier phase into transformed I and Q quadrature signals communicated to conventional output lock detectors to provide validity and confidence indicator signals for indicating that the residual estimates are valid for dynamic propagation of the residuals in a navigation receiver for improved performance especially in low signal-to-noise environments such as for use in an ultratight GPS navigation system.

Abstract: A multitarget tracking antispoofing receiver utilizes multitarget tracking algorithms and multiple correlators for tracking signals of interest in a field of view about a nominal trajectory of a desired true signal for tracking targets within the code phase and carrier frequency signal space so as to predict when true and spoof signals will cross paths in the signal space without spoofing with loss of tracking of the desired signal so that true tracking of a desired target is maintained in the presence of a spoofing signal moving along a spoofing signal track and crossing a true path of the true signal.

Abstract: An M code envelope detector receives an incoming binary offset carrier (BOC) signal, such as the M code signal, and generates inphase BOC and quadraphase BOC signals, separated by an offset, that have respective ambiguous correlation envelopes, that when combined, provide a near unimodal correlation function with respect to code phase error of the BOC signal having an inherent multimodal autocorrelation function, with the near unimodal correlation envelope being tracked by early and late code replicas at broad one chip phases for providing unambiguous but nonlinear code phase error tracking, which detector is then further improved with the use of code replicas having narrow partial chip phases, such as ? chip phases, for providing near linear code phase error tracking for unambiguous and accurate code tracking of the BOC signal.