to accurately determine the satellite signal travel time e g due to weak signal reception or some other condition the receiver can still estimate the pseudo range for the satellite based on an initial receiver position and system time in this case the system and methods described herein provide the necessary initial receiver position and system time with enough accuracy to estimate the pseudo range even under weak signal conditions the receiver can then use the estimated pseudo range to determine a more accurate receiver position application_number US 77184507 A description fig1 illustrates a receiver according to an exemplary embodiment of the invention an rf front end 100 processes the rf signal received at the antenna not shown operations of a conversional rf front end 100 include amplification down conversion and analog to digital conversion the rf front end 100 outputs an intermediate frequency if signal 101 to the baseband section of the receiver the if input is multiplied in if mixer 103 in phase and quad phase with a local frequency signal generated by a direct digital frequency synthesizer ddfs 102 this mixing involves multiplying the if input signal 101 by the local ddfs frequency which generates the in phase and quad phase component 104 the ddfs 102 is driven by a carrier numerically controlled oscillator nco 105 in addition carrier nco 105 receives phase and frequency corrections from a processor 110 because of this correction the ddfs frequency and phase is almost the same as that of the if input signal 101 thus the i and q signals produced by the if mixers 103 are at near zero carrier frequency.