Global positioning system receiver digital processing technique

A system for generating a desired binary signal shifted in phase a controlled amount from a source binary signal formed from a first periodic clock signal having a first period, comprising:

• means for generating from said source binary signal a replica thereof that is delayed an integral number of said first clock signal periods,
• means for generating a second periodic clock signal having a second period that is slightly different from said first period, said first and second clock signals being synchronous with each other,
• means for comparing said first and second clock signals to determine periodically recurring instances of substantial coincidence therebetween and generating a pulse thereat,
• means for resetting by said coincidence pulse a counter being clocked with said second clock signal,
• means receiving said source and delayed signals for generating the desired binary signal in respective alternating first and second durations, said first duration beginning at the coincidence pulse and continuing until said counter reaches a predetermined count and said second duration extending from said counter reaching said predetermined count until the occurrence of another coincidence pulse, and
• means for setting the predetermined count of said counter to obtain the desired signal having a desired phase relative to said source signal.

A system for processing L1 and L2 signals received from at least one satellite of a global positioning system wherein each of said signals includes a unique frequency carrier with a known pseudo-random P-code modulated thereon, comprising:

• means receiving the L1 and L2 signals for generating a single replica of the known P-code contained therein,
• a delay line having a plurality of taps,
• means for applying the single P-code replica to said delay line in a manner that the P-code replica is available at the plurality of delay line taps with different relative phases thereof, and
• means for obtaining the single generated P-code replica from two different taps of the delay line, thereby to make the P-code replica available at two different relative phases.

A system for processing L1 and L2 signals received from a satellite that include a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, comprising:

• means for generating replicas of the known pseudo-random P-code modulated on the received L1 and L2 signals,
• means receiving the L1 and L2 signals for demodulating the L1 and L2 signals with the P-code replicas provided by the P-code replica generating means, thereby producing demodulated L1 and L2 signals,
• means receiving the demodulated L1 and L2 signals for separately integrating them over time periods equal in length to a plurality of P-code cycles, thereby producing integrated demodulated L1 and L2 signals,
• means receiving the integrated demodulated L1 and L2 signals for combining them with each other, thereby generating at least one combined signal, and
• means communicating with said P-code replica generating means for adjusting the phases of the P-code replicas relative to the incoming L1 and L2 signals until a certain characteristic of said at least one combined signal is obtained that corresponds to a condition when the P-code replicas are substantially aligned in phase with the P-code modulated on the respective received L1 and L2 signals,
• whereby useful phases of the P-code replicas are obtained.

A method of processing L1 and L2 signals received from at least one satellite of a global positioning system wherein each of said signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, comprising the steps of:

• demodulating each of the received L1 and L2 signals with a locally generated replica of the known P-code that is contained therein,
• repetitively and separately integrating the demodulated L1 and L2 signals over time periods equal in length to a plurality of P-code cycles,
• combining a result of the integration step from each of the L1 and L2 signal paths with the integrated signal of the other of the L1 and L2 signal paths, and
• adjusting the phases of the locally generated P-code replicas relative to the incoming L1 and L2 signals until a given characteristic of the combined L1 and L2 signals is obtained that indicates the locally generated P-code signals are substantially aligned in phase with the P-code components of the received L1 and L2 signals, whereby the resulting locally generated P-code phases are useable to determine information of the location of the receiving position.

A method of processing L1 and L2 signals received from at least one satellite of a global positioning system wherein each of said signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, comprising the steps of:

• locally generating replicas of the known P-codes included in the L1 and L2 signals,
• demodulating the received L1 signal with the locally generated L1 signal P-code replica, thereby obtaining a demodulated L1 signal,
• combining together the L2 signal, the locally generated L2 signal P-code replica and the demodulated L1 signal, thereby obtaining a combined signal, and
• adjusting the phase of the locally generated L2 and P-code replica relative to the incoming L2 signal until a given characteristic of the combined signal is obtained that indicates the locally generated L2 signal P-code replica is substantially aligned in phase with the P-code component of the received L2 signal, whereby the phase of the L2 signal P-code component is determined from the phase of the locally generated L2 signal P-code replica even though the unknown code is also modulated onto the L2 signal carrier.

A method of processing L1 and L2 signals received from at least one satellite of a global positioning system wherein each of said signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, comprising the steps of:

• locally generating replicas of the known P-codes included in the L1 and L2 signals,
• demodulating the received L2 signal with the locally generated L2 signal P-code replica, thereby obtaining a demodulated L2 signal,
• combining together the L1 signal, the locally generated L1 signal P-code replica and the demodulated L2 signal, thereby obtaining a combined signal, and
• adjusting the phase of the locally generated L2 signal P-code replica relative to the incoming L2 signal until a given characteristic of the combined signal is obtained that indicates the locally generated L2 signal P-code replica is substantially aligned in phase with the P-code component of the received L2 signal, whereby the phase of the L2 signal P-code component is determined from the phase of the locally generated L2 signal P-code replica even though the unknown code is also modulated onto the L2 signal carrier.