초록 ▼

A method for compensating for multipath components in a received CDMA signal comprising a repetitive PRN code uses delay times in addition to the early, late and prompt delay times for determining if a multipath component is present in the received signal, and if so, making an adjustment to the dela

A method for compensating for multipath components in a received CDMA signal comprising a repetitive PRN code uses delay times in addition to the early, late and prompt delay times for determining if a multipath component is present in the received signal, and if so, making an adjustment to the delay time of the replica code generated by a receiver so as to minimize the difference between the correlation values for a delay time equal to-1 chip and a delay time more negative than-1 chip. In this manner, adjustments to the estimation time for the start of the PRN code can be made in a manner which minimizes the effects of multipath components. A system using additional delays and correlators in association with the code phase detector, a code numerical control oscillator and replica code generator is described for performing the above methodology. The methodology is particularly suitable for GPS receivers and may further be used in receivers that receive any type of digital sequence spread spectrum, code division multiple access signals. Compensation for multipath components with 180 degree phase shifts is also made as well as compensation due to smoothing of the triangular correlation function due to RF characteristics and non-ideal PRN codes.

대표청구항 ▼

Having described the invention, what is claimed is: 1. A method for reducing the effects of multipath signal components associated with a received direct path signal comprising a carrier frequency that is modulated by a repetitive pseudo-random noise (PRN) code, comprising the steps of: generating

Having described the invention, what is claimed is: 1. A method for reducing the effects of multipath signal components associated with a received direct path signal comprising a carrier frequency that is modulated by a repetitive pseudo-random noise (PRN) code, comprising the steps of: generating a replica code corresponding to the pseudo-random noise (PRN) code of the received signal; correlating the received signal with the replica code to generate a first correlation result with a first, delay time, where the first delay time is set outside of the assumed correlation function area; correlating the received signal with the replica code to generate a second correlation result with a second delay time, where the second delay time is set between the first delay time and assumed correct delay time of the correlation function determining if the correlation results of the first and second delay times are substantially equal to each other and, if the first and second correlation results are not substantially equal to each other, adjusting the correlation timing so as to cause the first and second correlation results to be substantially equal to each other. 2. A method for reducing the effects of multipath signal components as defined in claim 1, wherein the pseudo-random noise (PRN) code has a plurality of chips of code length, and wherein the first delay time is a delay of approximately-0.5 chip from the second delay time. 3. A method for reducing the effects of multipath signal components as defined in claim 2, wherein the second delay time is approximately one chip from the correct correlation timing when the first and second correlation results are substantially equal to each other. 4. A system for reducing the effects of multipath signal components associated with a received direct path signal comprising a carrier signal that is modulated by a repetitive pseudo-random noise (PRN) code comprising: A) a replica code generator for generating a replica code corresponding to the pseudo-random noise (PRN) code of the received signal; B) means for correlating the received signal with the replica code to generate a first correlation result with a first delay time, where the first delay time is set outside of the assumed correlation function area; C) means for correlating the received signal with the replica code to generate a second correlation result with a second delay time, where the second delay time is set between the first delay time and assumed correct delay time of the correlation function; and D) means for determining if the correlation results of the first and second delay times are substantially equal to each other and if the first and second correlation results are not substantially equal to each other, for adjusting the correlation timing so as to cause the first and second correlation results to be substantially equal to each other. 5. A system for reducing the effects of multipath signal components as defined in claim 4, wherein the pseudo-random noise (PRN) code has a plurality of chips of code length, and wherein the first delay time is a delay of approximately-0.5 chip from the second delay time. 6. A system for reducing the effects of multipath signal components as defined in claim 5, wherein the second delay time is approximately one chip from the correct correlation timing when the first and second correlation results are substantially equal to each other. 7. A device for reducing the effects of multipath signal components associated with a received direct path signal forming an overall received signal, wherein each component and direct path signal is modulated by a repetitive pseudo-random noise (PRN) code comprising: A) a replica code generator for generating a replica code corresponding to the pseudo-random noise (PRN) code of the received signal; B) means for correlating the received signal with the replica code to generate a first correlation result with a first delay time, where the first delay time is set outside of the assumed correlation function area; C) means for correlating the received signal with the replica code to generate a second correlation result with a second delay time, where the second delay time is set between the first delay time and assumed correct delay time of the correlation function; and D) a code phase detector receiving the outputs of the two correlating means for generating an adjustment signal for adjusting the timing of the replica code generator; wherein the adjustment signal generated by the code phase detector causes an adjustment in the timing of the replica code generator until the correlation results of the first and second delay times are substantially equal to each other and, if the first and second correlation results are not substantially equal to each other, for adjusting the correlation timing so as to cause the first and second correlation results to be substantially equal to each other. 8. A device for reducing the effects of multipath signal components as defined in claim 7, wherein the pseudo-random noise (PRN) code has a plurality of chips of code length, and wherein the first delay time is a delay of approximately-0.5 chip from the second delay time. 9. A device for reducing the effects of multipath signal components as defined in claim 8, wherein the second delay time is approximately one chip from the correct correlation timing when the first and second correlation results are substantially equal to each other. 10. A device for reducing the effects of multipath signal components as defined in claim 7, wherein the adjustment of the timing of the replica code generator uses a numerically controlled oscillator (NCO).