Method of deriving phase of pseudo-random code signal in global positioning system receiver

Claim 1

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving a cumulative total amount of change of phase (Δτ(n)) of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on an amount of change of frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal.

Claim 2

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving a cumulative total amount of change of phase (Δτ(n)) of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on an amount of change of frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal.

Claim 4

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving a cumulative total amount of change of phase (Δτ(n) of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on an amount of change of frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal; the method further comprising a step of judging when a predetermined number of repetitions of said phase derivation operation has been executed, and when that predetermined number is reached, setting a finally obtained value of phase (t n ) of said received pseudo-random code signal as an initial phase value for a loop filter of a negative feedback type of code tracking loop, and thereafter executing phase tracking of said received pseudo-random code signal by said code tracking loop to thereby obtain successive values of phase of said received pseudo-random code signal.

Claim 5

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving a cumulative total amount of change of phase (Δτ(n) of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on an amount of change of frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal; the method further comprising a step of judging when a predetermined number of repetitions of said phase derivation operation has been executed, and when that predetermined number is reached, setting a finally obtained value of phase (t n ) of said received pseudo-random code signal as an initial phase value for a loop filter of a negative feedback type of code tracking loop, and thereafter executing phase tracking of said received pseudo-random code signal by said code tracking loop to thereby obtain successive values of phase of said received pseudo-random code signal.

Claim 6

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving an amount of change of phase (d(n)) of the received pseudo-random code signal that has occurred since execution of an immediately preceding phase derivation operation, based on an amount of change of frequency of said received carrier, and storing that amount of phase change in a memory, computing a total amount of cumulative change of phase of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on a change in frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal; the method further comprising a step of judging when a predetermined number of repetitions of said phase derivation operation has been executed, and when that predetermined number is reached, using said stored values of amount of phase change (d(n)) in conjunction with a value or received pseudo-random code signal phase that is derived when said predetermined number of repetitions is reached, to derive recalculated values (t' n ) for each of the values of received pseudo-random code signal phase (t n ) previously derived up to said predetermined number, then a step of setting a phase value derived when said predetermined number was reached, as an initial phase value of a negative feedback type of code tracking loop, and thereafter executing phase tracking of said received pseudo-random code signal by said code tracking loop to thereby obtain successive values of phase of said received pseudo-random code signal.

Claim 7

A method of measuring the phase of a received pseudo-random code signal, for use in a global positioning system receiver apparatus adapted for receiving a radio signal including a received carrier which is modulated by a pseudo-random code signal, the receiver apparatus including means for obtaining a value of frequency of said received carrier, means for demodulating the received carrier to obtain a received pseudo-random code signal, means for generating a replica pseudo-random code signal having a code sequence that is identical to a code sequence of said received pseudo-random code signal, and means for indicating when a predetermined condition of phase correlation occurs between said received pseudo-random code signal and replica pseudo-random code signal, the method comprising, when a momentary interruption of reception of said radio signal occurs, a step of successively varying the phase of said replica pseudo-random code signal until said correlation condition is indicated, and setting the phase of said replica pseudo-random code signal at the phase value for which the correlation condition occurs, then repetitively executing at periodic intervals a phase derivation operation to obtain a current value of phase of said received pseudo-random code signal, the phase derivation operation including steps of: deriving an amount of change of phase (d(n)) of the received pseudo-random code signal that has occurred since execution of an immediately preceding phase derivation operation, based on an amount of change of frequency of said received carrier, and storing that amount of phase change in a memory, computing a total amount of cumulative change of phase of said received pseudo-random code signal that has occurred since said correlation condition was indicated, based on a change in frequency of said received carrier, and setting the phase of said replica pseudo-random code signal to a value that is the sum of said initial phase value (t 1 ) and said total amount of phase change (Δτ(n)); measuring an amount of phase difference (D n ) between said received pseudo-random code signal and replica pseudo-random code signal; calculating an average value of a cumulative total of successively derived ones of said amount of phase difference, respectively obtained since said initial value of phase was measured; and calculating the sum of said average value, said initial value of phase (t 1 ) and said total amount of phase change (Δτ(n)), to obtain said current value of phase (t n ) of said received pseudo-random code signal; the method further comprising a step of judging when a predetermined number of repetitions of said phase derivation operation has been executed, and when that predetermined number is reached, using said stored values of amount of phase change (d(n)) in conjunction with a value or received pseudo-random code signal phase that is derived when said predetermined number of repetitions is reached, to derive recalculated values (t' n ) for each of the values of received pseudo-random code signal phase (t n ) previously derived up to said predetermined number, then a step of setting a phase value derived when said predetermined number was reached, as an initial phase value of a negative feedback type of code tracking loop, and thereafter executing phase tracking of said received pseudo-random code signal by said code tracking loop to thereby obtain successive values of phase of said received pseudo-random code signal.