Receiver and signal processing method

Abstract

A receiver includes radio frequency circuitry, a correlator, and a signal delay estimator. The radio frequency circuitry is configured to receive a first satellite signal and a second satellite signal to generate a first baseband signal and a second baseband signal, respectively. The correlator is configured to perform a correlation operation based on a first local signal and the first baseband signal to generate a first correlation result. The correlator is also configured to perform a correlation operation based on a second local signal and the second baseband signal to generate a second correlation result. The signal delay estimator is coupled to the correlator and configured to compensate the first correlation result using the second correlation result to generate a compensated first correlation result, and determine a signal delay of the first satellite signal based on the compensated first correlation result.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to satellite positioning technology, and more particularly, to a receiver and signal processing method. BACKGROUND

[0002] Satellite-based positioning receivers need to estimate the time of arrival (ToA) of satellite signals, especially the ToA via the direct path (i.e., line-of-sight, LoS) from the satellite to the receiver, which can be used to measure the distance between the receiver and the satellite. In the prior art, the receiver uses a correlator to perform correlation between the received satellite signal and a local signal replica. Usually the local signal replica has the same signal format as the satellite transmitted signal, e.g., using the same pseudorandom noise code (PRN code), and the resulting correlation result depends on the auto-correlation function (ACF) of the satellite signal, i.e., the correlation result depends on the satellite signal format and the time delay between the local signal replica and the received signal. Using different local signal replicas (each replica has a different time delay), the receiver can search for or estimate the ToA of the direct path signal. However, if the receiver receives multiple path signals simultaneously (e.g., one direct path signal and one or more reflected path signals), the correlation result calculated by the correlator is no longer the ACF of the single satellite signal and the local signal replica, but a mixture of the ACFs of the multiple signals. That is, the result calculated by the correlator is distorted, which in turn leads to an error in the estimation of the ToA of the direct path signal. Since the ToA of the signal is used to calculate the receiver position, the error in its estimation will lead to an error in the calculation of the user position. SUMMARY

[0003] The following summary is illustrative only and is not intended to be limiting in any way. That is, the following summary is provided to introduce some concepts, highlights, benefits and advantages of the novel and non-obvious technology described herein. Selected implementations are described in further detail in the detailed description that follows. Thus, the following summary is neither intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

[0004] The present invention can reduce or eliminate the estimation error of the direct path by using the received satellite signal to calibrate the ACF distortion of another received satellite signal.

[0005] In a first aspect, the present disclosure provides a receiver comprising a radio frequency (RF) circuit, a correlator, and a signal delay estimator. The radio frequency (RF) circuit is configured to receive a first satellite signal and a second satellite signal to generate a first baseband signal and a second baseband signal, respectively. The correlator is configured to perform a correlation operation based on a first local signal replica and the first baseband signal to generate a first correlation result, and perform a correlation operation based on a second local signal replica and the second baseband signal to generate a second correlation result. The signal delay estimator is coupled to the correlator and configured to compensate the first correlation result using the second correlation result to generate a compensated first correlation result, and determine a signal delay of the first satellite signal based on the compensated first correlation result.

[0006] In some embodiments, an auto-correlation function (ACF) of the first satellite signal is different from an auto-correlation function (ACF) of the second satellite signal.

[0007] In some embodiments, a base of the ACF of the first satellite signal is wider than a base of the ACF of the second satellite signal.

[0008] In some embodiments, the first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a global positioning system (GPS), a quasi-zenith satellite system (QZSS), a Galileo satellite navigation system, a Beidou satellite navigation system, a GLONASS system, an Indian Regional Navigational Satellite System (NavIC), and a satellite based augmentation system (SBAS).

[0009] In some embodiments, the first correlation result is mixed from a first sub-correlation result corresponding to a direct path of the first satellite signal and a second sub-correlation result corresponding to a reflected path of the first satellite signal, and the second correlation result is mixed from a third sub-correlation result corresponding to a direct path of the second satellite signal and a fourth sub-correlation result corresponding to a reflected path of the second satellite signal. The signal delay estimator predicts the second sub-correlation result based on the second correlation result, and compensates the first correlation result using the predicted second sub-correlation result to obtain a compensated first correlation result.

[0010] In some embodiments, the first local signal replica and the second local signal replica used by the correlator are in formats based on a format of the first satellite signal and a format of the second satellite signal, respectively. The first correlation result is determined by an auto-correlation function (ACF) of the first satellite signal, and the second correlation result is determined by an auto-correlation function (ACF) of the second satellite signal.

[0011] In some embodiments, the first correlation result includes m sample points, the second correlation result includes n sample points, and the signal delay estimator compensates values of the m sample points of the first correlation result using a relationship between the m sample points of the first correlation result and the n sample points of the second correlation result.

[0012] In some embodiments, m equals 2 and n equals 1.

[0013] In some embodiments, the first correlation result includes two sample points corresponding to a leading local signal replica and a lagging local signal replica of the first satellite signal.

[0014] In some embodiments, the first correlation result includes one sample point corresponding to an on-time local signal replica of the first satellite signal.

[0015] In some embodiments, the second correlation result includes one sample point corresponding to an arbitrary time-delayed local signal replica of the second satellite signal for searching possible reflected path signals of the second satellite signal.

[0016] In some embodiments, the first correlation result includes one sample point corresponding to an on-time local signal replica of the first satellite signal, and the second correlation result includes two sample points corresponding to on-time local signal replicas of direct path and reflected path of the second satellite signal.

[0017] In some embodiments, the first correlation result is mixed from a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, the second correlation result is mixed from a third ACF corresponding to a direct path of the second satellite signal and a fourth ACF corresponding to a reflected path of the second satellite signal, and the signal delay estimator predicts the second ACF from leading and lagging code correlation values of the third ACF and leading and lagging code correlation values of the fourth ACF and compensates the first ACF using the predicted second ACF.

[0018] In some embodiments, the signal delay estimator compensates at least one of leading and lagging code correlation values of the first ACF using the predicted second ACF.

[0019] In a second aspect, the present application provides a signal processing method, wherein the method comprises: receiving a first satellite signal and a second satellite signal to generate a first baseband signal and a second baseband signal, respectively; performing a correlation operation between a first local signal and the first baseband signal to generate a first correlation result; performing a correlation operation between a second local signal and the second baseband signal to generate a second correlation result; compensating the first correlation result by using the second correlation result to compensate the first correlation result, and determining a signal delay of the first satellite signal according to the compensated first correlation result.

[0020] In some embodiments, an autocorrelation function (ACF) of the first satellite signal is different from an autocorrelation function (ACF) of the second satellite signal.

[0021] In some embodiments, a base of the ACF of the first satellite signal is wider than a base of the ACF of the second satellite signal.

[0022] In some embodiments, the first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a global positioning system (GPS), a quasi-zenith satellite system (QZSS), a Galileo satellite navigation system, a Beidou satellite navigation system, a GLONASS system, an Indian regional navigation satellite system (NavIC), and a satellite based augmentation system (SBAS).

[0023] In some embodiments, the first correlation result is mixed from a first sub-correlation result corresponding to a direct path of the first satellite signal and a second sub-correlation result corresponding to a reflected path of the first satellite signal, and the second correlation result is mixed from a third sub-correlation result corresponding to a direct path of the second satellite signal and a fourth sub-correlation result corresponding to a reflected path of the second satellite signal; and the step of compensating the first correlation result by using the second correlation result comprises predicting the second sub-correlation result according to the second correlation result, and compensating the first correlation result by using the predicted second sub-correlation result to obtain the compensated first correlation result.

[0024] In some embodiments, formats of the first local signal and the second local signal are based on a format of the first satellite signal and a format of the second satellite signal, respectively, the generated first correlation result is determined by an autocorrelation function (ACF) of the first satellite signal, and the generated second correlation result is determined by an autocorrelation function (ACF) of the second satellite signal.

[0025] In some embodiments, the first correlation result includes m sample points, the second correlation result includes n sample points, and the signal processing method further includes compensating values of the m sample points of the first correlation result using a relationship between the m sample points of the first correlation result and the n sample points of the second correlation result.

[0026] In some embodiments, m equals 2 and n equals 1.

[0027] In some embodiments, the first correlation result includes two sample points corresponding to a leading local signal replica, a lagging local signal replica of the first satellite signal.

[0028] In some embodiments, the first correlation result includes one sample point corresponding to an on-time local signal replica of the first satellite signal.

[0029] In some embodiments, the second correlation result includes one sample point corresponding to an arbitrary time-delayed local signal replica of the second satellite signal for searching a possible reflected path signal of the second satellite signal.

[0030] In some embodiments, the first correlation result includes one sample point corresponding to an on-time local signal replica of the first satellite signal, and the second correlation result includes two sample points corresponding to on-time local signal replicas of direct and reflected paths of the second satellite signal.

[0031] In some embodiments, the first correlation result is mixed from a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, the second correlation result is mixed from a third ACF corresponding to a direct path of the second satellite signal and a fourth ACF corresponding to a reflected path of the second satellite signal, and compensating the first correlation result using the second correlation result to generate a compensated first correlation result includes predicting the second ACF according to leading and lagging code correlation values of the third ACF and leading and lagging code correlation values of the fourth ACF, and compensating the first correlation result using the predicted second ACF.

[0032] In some embodiments, compensating the first correlation result using the predicted second ACF includes compensating at least one of leading and lagging code correlation values of the first ACF using the predicted second ACF.

[0033] After reading the preferred embodiments illustrated in the various figures and the following detailed description, these and other objects of the invention will undoubtedly become apparent to those skilled in the art. The invention is provided by way of example and is not intended to be limiting. Other embodiments and advantages are described in detail in the following description.

[0034] These and other objects of the invention will be readily understood by those skilled in the art upon reading the following detailed description of the preferred embodiments illustrated in the accompanying drawings. A detailed description will be given in the following embodiments with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings (in which the same numerals denote the same components) illustrate embodiments of the present invention. The included drawings are used to provide a further understanding of embodiments of the present disclosure, and are incorporated in and constitute a part of the present disclosure. The drawings illustrate implementations of embodiments of the present disclosure and, together with the description, serve to explain the principles of the embodiments of the present disclosure. It is understood that the drawings are not necessarily drawn to scale, as some components may be shown out of proportion to actual dimensions in order to clearly illustrate the concepts of the embodiments of the present disclosure.

[0036] Figure 1 This is a schematic diagram illustrating a satellite system that transmits multiple signals.

[0037] Figure 2 This is a schematic diagram of a receiver according to an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of ACF_L1 and ACF_L5 according to an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of compensation ACF_L1 according to an embodiment of the present invention.

[0040] Figure 5 This is a schematic diagram of a signal delay estimator according to an embodiment of the present invention.

[0041] In the following detailed description, numerous specific details are set forth for illustrative purposes so that those skilled in the art can more thoroughly understand the embodiments of the invention. However, it will be apparent that one or more embodiments may be practiced without these specific details, and different embodiments may be combined as needed, and should not be limited to the embodiments illustrated in the accompanying drawings. Detailed Implementation

[0042] The following description is of the best implementing mode of the present application which is merely used to illustrate the technical features of the present application and is not used to limit the scope of the present application. In the whole description and claims, some words are used to refer to specific elements, and those skilled in the art should understand that the manufacturers can use different names to refer to the same elements. Therefore, the description and claims of the present application are not based on the difference of names to distinguish the elements, but based on the difference of functions of the elements. The terms "element", "system" and "device" used in the present application can be computer-related entities, which can be hardware, software, or a combination of hardware and software. In the following description and claims, the terms "comprise" and "include" are open terms, which should be interpreted as "comprising, but not limited to". In addition, the term "coupled" means indirect or direct electrical connection. Therefore, if a device is described as coupled to another device in the text, it means that the device can be directly electrically connected to the other device, or indirectly electrically connected to the other device through other devices or connection means.

[0043] In the drawings, like reference numerals refer to like parts throughout the various views. The drawings illustrate generally, by way of example, but not of limitation, embodiments in which the principles of the present application can be employed.

[0044] The term "substantially" or "approximately" used herein means that within an acceptable range, those skilled in the art can solve the technical problems to be solved and substantially achieve the technical effects to be achieved. For example, "substantially equal" means that within an acceptable range, the skilled person can accept a certain error from "exactly equal" without affecting the correctness of the results.

[0045] The present application can reduce the estimation error of the time of arrival (ToA) of the direct path by using the received first satellite signal to disassemble and compensate another received second satellite signal (wherein the first satellite signal and the second satellite signal are both satellite mixed signals, which are mixed by a direct path signal and one or more multipath / reflected signals, i.e. the satellite signal received by the receiver is a mixed signal of the direct path signal affected by one or more multipath / reflected signals and reaching the receiver). It can be understood that in the embodiments of the present application, the direct path signal generally refers to the signal with the shortest delay in the satellite mixed signal received by the receiver. Figure 1is a schematic diagram illustrating a satellite system transmitting multiple signals. The satellite system includes Global Navigation Satellite Systems (GNSS) such as GPS (Global Positioning System), Galileo, GLONASS, BeiDou, NavIC (Indian Regional Navigation Satellite System), QZSS (Quasi-Zenith Satellite System), SBAS (Satellite-Based Augmentation System), etc. Satellites in these systems transmit multiple signals simultaneously at different Radio-Frequency (RF) frequencies and modulation formats. As shown in Figure 1

[0046] Figure 2 is a schematic diagram illustrating a receiver 200 according to an embodiment of the present application. As shown in Figure 2 ​The receiver 200 includes a radio frequency (RF) circuit 210, a correlator 220, a signal delay estimator 230, and a signal processing circuit 240. In this embodiment, the receiver 200 is located in an electronic device, such as a cell phone, a tablet, or a watch. The receiver 200 is configured to receive L1 signals (e.g., GPS L1 CA signals) and L5 signals (e.g., GPS L5 signals) to determine the location of the electronic device. The received multiple satellite signals can include multiple signals from the same satellite / other satellites in a satellite system or other satellites in other satellite systems. For example, a GPS satellite can transmit L1 CA, L1 C (including data and pilot component signals), L2C (including CL and CM component signals), and L5 (including I5 and Q5 component signals). A Galileo satellite can transmit E1 (including E1 B and E1 C component signals), E5a (including data and pilot component signals), E5b (including data and pilot component signals), and E6 signals. Multiple signals can also be transmitted from the same satellite in other satellite systems (e.g., Beidou, GLONASS, NavIC, SBAS, etc.). In the receiver 200, the present disclosure provides how to use the second signal from the same satellite to compensate for the multipath error of the first signal in the same satellite. The same method can be applied to receive multiple signals and compensate for the multipath error of the first signal. The correlator 220, the signal delay estimator 230, and the signal processing circuit 240 can be implemented in hardware circuits or software programs.

[0047] In operation of the receiver 200, the radio frequency (RF) circuit 210 receives a plurality of satellite signals (e.g., a first satellite signal and a second satellite signal) and converts the plurality of satellite signals into a plurality of baseband signals (e.g., a first baseband signal and a second baseband signal). For example, the first satellite signal comprises an L1 signal, the second satellite signal comprises an L5 signal, the first baseband signal comprises an L1 baseband signal (e.g., a baseband signal obtained by frequency shifting the L1 signal), and the second baseband signal comprises an L5 baseband signal (e.g., a baseband signal obtained by frequency shifting the L5 signal). For ease of illustration and understanding, in the embodiments of the present application, the first satellite signal and the second satellite signal are exemplified by L1 signal and L5 signal, respectively, but the present application is not limited to this example. The correlator 220 generates local signal replicas based on the satellite signal format and performs correlation operations based on the local signal replicas and the received baseband signals to generate correlation values. For example, the correlator 220 is configured to perform correlation operations based on a first local signal replica and the first baseband signal to generate a first correlation result, and perform correlation operations based on a second local signal replica and the second baseband signal to generate a second correlation result. One embodiment of a local signal replica is that different local signal replicas have the same format as the satellite signal format but have different time delays, and the correlation result value depends on the autocorrelation function ACF(T) of the satellite signal. The value of the autocorrelation function ACF is determined by the satellite signal format, the received satellite signal strength, and the relative time delay (T) of the received satellite signal and the local signal replica. That is, different local signal replicas have different ACF(T) values after correlation operations with the satellite signal. More specifically, the correlator can perform the following operations on the baseband signal: Doppler frequency removal, satellite pseudo-random noise code erasure, and correlation operations (such as multiplication integration) using one or more local signal replicas and the baseband signal to obtain one or more corresponding correlation result values ACF(T). Since the detailed operation of the correlator is well known to those skilled in the art, the details are not described here. In addition, the local signal replica in the present application includes but should not be limited to a replica that is exactly the same as the satellite signal format, as long as the replica is derived from the satellite signal format. For ease of illustration, the present embodiment exemplifies that the correlator 220 comprises two correlators corresponding to two different satellite signals, but the present application is not limited to this example. In the example comprising two correlators, the first correlator is configured to generate a first correlation result for the L1 signal, and the second correlator is configured to generate a second correlation result for the L5 signal. For example, the correlation value generated by the first correlator is ACF_L1(T), and the correlation value generated by the second correlator is ACF_L5(T). In an example embodiment, each correlator uses a local signal replica that is the same as the corresponding satellite signal format.It should be noted that the present application should not be limited to the embodiment comprising two correlators. That is, the same correlator can use different signals (e.g., Ll and L5 signals) to perform correlation operation with the received signal, or multiple correlators can be used to process different signals and different copies of the signals. In particular, the embodiments of the present application are not limited. In an example embodiment, the correlator 220 can comprise a first correlator and a second correlator, wherein the first correlator is configured to perform correlation operation based on a first local signal copy and the Ll signal (first baseband signal) received by the correlator 220 to generate a first correlation result, e.g., an autocorrelation function ACF_Ll; the second correlator is configured to perform correlation operation based on a second local signal copy and the L5 signal (second baseband signal) to generate a second correlation result, e.g., an autocorrelation function ACF_L5. For example, the first correlator can perform the following operations: Doppler frequency removal, satellite pseudo-random noise code wipe-off, correlation operation (e.g., multiplication integration) between the Ll baseband signal and the local Ll signal (also referred to as the first local signal copy), etc. Similarly, the second correlator can perform the following operations: Doppler frequency removal, satellite PRN code wipe-off, correlation operation (e.g., multiplication integration) between the L5 baseband signal and the local L5 signal (second local signal copy), etc. Since the detailed operations of the correlator are well known to those skilled in the art, the details thereof will not be described herein. The focus of the present application is to use the correlation result of the L5 signal to compensate the correlation result of the Ll signal to obtain the accurate delay corresponding to the direct path of the Ll signal, i.e., to reduce the interference of the reflected path of the Ll signal.

[0048] Please refer to Figure 3 , Figure 3Fig. 1 shows a schematic diagram of the autocorrelation functions ACF_L1 and ACF_L5 according to an embodiment of the present application. In the embodiment of the present application, the receiver receives both L1 and L5 signals, and under multipath interference, the received L1 / L5 signals are composite path signals, which include direct path signals and multipath (e.g., reflected path) signals. For ease of illustration and understanding, a reflected path signal is taken as an example. The first correlator performs correlation operation on the received L1 signal, and the correlation result value can be referred to as ACF_L1_Composite(T), where T is the time delay between the received signal and the local signal copy. If only the direct path signal is received, the result value calculated by the first correlator can be represented as ACF_L1_Direct(T); similarly, if only the reflected path signal is received, the result value calculated by the first correlator can be represented as ACF_L1_Reflect(T). ACF_L1_Composite(T) is a mixture of ACF_L1_Direct(T) and ACF_L1_Reflect(T). Similarly, the second correlator performs correlation operation on the received L5 signal, and the correlation result value ACF_L5_Composite(T) is a mixture of the correlation result of the L5 direct path signal ACF_L5_Direct(T) and the correlation result of the L5 reflected path signal ACF_L5_Reflect(T). It can be understood that the first correlation result (e.g., ACF_L1_Composite(T), ACF_L1) is a mixture of the first sub-correlation result (e.g., ACF_L1_Direct(T)) corresponding to the direct path of the first satellite signal (e.g., L1 signal) and the second sub-correlation result (e.g., ACF_L1_Reflect(T)) corresponding to the reflected path of the first satellite signal, and the second correlation result (e.g., ACF_L5_Composite(T), ACF_L5) is a mixture of the third sub-correlation result (e.g., ACF_L5_Direct(T)) corresponding to the direct path of the second satellite signal (e.g., L5 signal) and the fourth sub-correlation result (e.g., ACF_L5_Reflect(T)) corresponding to the reflected path of the second satellite signal. In Figure 3In the upper example, the correlation curve shown by the leftmost triangle can be considered as the first sub-correlation result ACF_L1_Direct(T) or the first ACF corresponding to the direct path signal, while the correlation curve shown by the rightmost triangle with the dashed line can be considered as the second sub-correlation result ACF_L1_Reflect(T) or the second ACF corresponding to the reflected path. The base width of these two triangles depends on the chip rate of the pseudo-random noise code in the L1 signal format. The two triangles are superimposed to form the first correlation result ACF_L1_Composite(T) corresponding to the mixed path, the shape of which depends on the delay and signal strength of the reflected path signal. It should be noted that the ACF shown in this embodiment is a triangle, but the ACF of satellite signals is not limited to triangles. For example, due to BOC (binary offset carrier) modulation in GPS L1C signals, its ACF is formed by the superposition of three triangles. When the delay of the reflected path signal is too small, ACF_L1_Direct(T) and ACF_L1_Reflect(T) partially overlap. In other words, the correlation result of the correlator calculating the L1 signal is no longer ACF_L1_Direct(T), but also includes the contribution of ACF_L1_Reflect(T), i.e., it is affected by the reflection path. In this embodiment, since the L1 signal has a lower PRN (pseudo-random noise number) chip rate, the ACF corresponding to its direct path signal and the ACF corresponding to the reflection path signal overlap, resulting in an asymmetrical shape of the ACF_L1 corresponding to the mixed path. In addition, although the reflection paths of the L1 signal and the L5 signal have the same delay, the PRN chip rate of the L5 signal is higher than that of the L1 signal, that is, the triangular base of ACF_L5 is narrower than that of ACF_L1, so the influence of the reflection path signal is smaller. This embodiment of the invention is illustrated by the example that ACF_L5_Direct(T) and ACF_L5_Reflect(T) do not overlap. Figure 3 The lower part is shown.

[0049] To locate and / or demodulate data transmitted by the satellite, the receiver estimates the satellite direct path signal delay to track the direct path signal. The correlator then selects the necessary local signal replica delay (T) to calculate the corresponding correlation value ACF_L1_Direct(T), which is used for subsequent signal processing. Figure 3 For example, to track and estimate the direct path signal delay, two relevant result values ​​can be calculated: such as ACF_L1_E1 and ACF_L1_L1, which correspond to the delays T of the two local signal replicas, respectively. L1,E1 and T L1,L1If the characteristics of the ACF (e.g., the shape of the ACF of the Ll signal) are known, then the ACF_L1_E1, ACF_L1_L1, T L1,E1 and T L1,L1 can be calculated. The ACF_L1_E1 is the ACF of the Ll signal with respect to the direct path signal delay, i.e., the time delay corresponding to the peak of the left triangle in the ACF_L1_E1. The ACF_L1_L1 is the ACF of the Ll signal with respect to the reflected path signal delay, i.e., the time delay corresponding to the peak of the right triangle in the ACF_L1_L1. The ACF_L1_E1 and ACF_L1_L1 are shown in FIG. 2. Figure 3 The ACF_L1_E1 and ACF_L1_L1 are shown in FIG. 2. Figure 3 As shown in FIG. 2, the receiver receives both the direct path and reflected path signals. The reflected path signal needs to be detected and its relationship with the direct path signal needs to be estimated so that the effect of the reflected path on the direct path signal can be removed. As shown in FIG. 3, the correlation value ACF_L1_L1 that is affected by the reflected path is modified to ACF_L1_L1'. Figure 4

[0050] In one embodiment, the correlation result of the L5 signal is used to reduce or remove the multipath interference in the correlation result of the Ll signal. For ease of description and understanding, the time delays corresponding to the peaks of ACF_L1_Direct(T), ACF_L1_Reflect(T), ACF_L5_Direct(T) and ACF_L5_Reflect(T) are defined as T L1,DP , T L1,RP , T L5,DP and T L5,RP , respectively. Since the Ll reflected path signal and the L5 reflected path signal have the same (or approximately the same) delay, the signal delay estimator 230 uses the correlation result of the L5 signal to obtain the time difference between T L5,DP and T L5,RP , which is equal to (or approximately equal to) the time difference between T L1,DP and T L1,RP , and can be used to estimate ACF_L1_Reflect(T). After the correlator calculates the correlation value ACF_L1_Composite(T) of the Ll signal, the estimated ACF_L1_Reflect(T) is subtracted from the ACF_L1_Composite(T) to obtain the compensated ACF_L1_Composite(T), which can be considered as the ACF_L1_Direct(T) of the Ll direct path signal. Figure 4 For example, after the effect of the reflected path signal ACF is removed, ACF_L1_L1 becomes ACF_L1_L1', which reduces or eliminates the effect of the reflected path signal. If a more accurate estimation is needed, the signal delay estimator 230 can further compensate for the incremental delay between the L5 signal and the Ll signal (i.e., further compensate for T L1,DP and T L5,DP ​to more accurately estimate the peak position of the ACF corresponding to the reflected path of the Ll signal, and thus more accurately estimate the signal delay of the Ll signal. For example, the incremental delay between the L5 signal and the Ll signal can be obtained by estimating the delay difference of the two signals through the ionosphere (e.g., by using a known ionospheric model). Then, the signal delay estimator 230 subtracts the ACF estimate corresponding to the reflected path of the Ll signal from the ACF_Ll to obtain a compensated ACF, which is similar to the ACF corresponding to the direct path of the Ll signal. It will be readily understood by one skilled in the art that, given the known format of the Ll and L5 signals (e.g., the corresponding ACF shapes), the time delay between the Ll and L5 signals (including the direct path and reflected path signals, T L1,DP , T L1,RP , T L5,DP , T L5,RP ) can be known, measured, or estimated, and thus ACF_Ll_Direct(T) and ACF_Ll_Reflect(T) can be determined based on how ACF_Ll_Direct(T) and ACF_Ll_Reflect(T) mix to form ACF_Ll_Composite(T). Thus, by compensating ACF_Ll_Composite(T), the effect of ACF_Ll_Reflect(T) on ACF_Ll_Direct(T) can be greatly reduced or eliminated, and thus the signal delay of the Ll signal can be accurately determined based on the compensated ACF_Ll_Composite(T).

[0051] In another embodiment, the correlator 220 provides multiple ACF taps / samples (which correspond to local signal replicas with different time delays) such as early code correlation value ACF_L1_E1 and late code correlation value ACF_L1_L1 to the signal delay estimator 230 to estimate and track the signal delay (i.e. the ACF peak position). The correlator uses local signal replicas with different time delays to correlate with the received signal, and the resulting correlation values are different taps of the ACF. Assuming that the correlation value ACF_L1_P1 corresponds to the prompt local signal replica (which can also be referred to as the prompt code, e.g. the time delay of the local signal replica is aligned to the received signal), the early code correlation value ACF_L1_E1 uses a local signal replica that is ahead of the prompt code, e.g. ahead by 0.5 chip interval. The late code correlation value ACF_L1_L1 uses a local signal replica that is behind the prompt code, e.g. behind by 0.5 chip interval. Depending on the shape of the ACF, the early code correlation value ACF_L1_E1 and the late code correlation value ACF_L1_L1 can be used to estimate the time delay of the local signal replica relative to the received signal, and hence to track the time of arrival (ToA) of the received signal. As shown in Figure 3 , due to the effect of the reflected path, the ACF_L1 is no longer the ACF corresponding to the original direct path. The distorted ACF_L1 leads to an incorrect late code correlation value ACF_L1_L1 (and possibly an incorrect ACF_L1_E1 as well), and hence an incorrect ToA calculation. Therefore, in the example of Figure 3 , the signal delay estimator 230 subtracts the estimated contribution of the L1 signal reflected path (e.g. the estimated / predicted correlation value corresponding to the L1 signal reflected path) from the correlation value ACF_L1_L1 to obtain a new early code correlation value ACF_L1_E1 and / or a new late code correlation value ACF_L1_L1, which are used to calculate the ToA and hence to exclude the effect of the reflected path signal. For example, in Figure 4 , the original late code correlation value ACF_L1_L1 is adjusted to a new late code correlation value ACF_L1_L1’ for the signal delay estimator 230 to calculate the path delay of the L1 signal.

[0052] As is well known to those skilled in the art, different ACF correlation value points can be generated by performing correlation operations between the received satellite signal and different local signal replicas. Each point uses a different local signal replica time delay, such as instant code, lead code, and lag code. In one embodiment, correlator 220 calculates m ACF_L1 correlation value points (sample points) and n ACF_L5 correlation value points, where m is an integer greater than or equal to 1 and n is an integer greater than or equal to 1. For example, if m equals 2 and n equals 1, then correlator 220 generates three correlation values: ACF_L1[0], ACF_L1[1], and ACF_L5[0]. The signal delay estimator 230 can calculate the delay of the direct path based on the relationship characteristics between ACF_L1[0], ACF_L1[1] and ACF_L5[0] (including the time delay relationship of the local signal replicas used by ACF_L1[0], ACF_L1[1], and ACF_L5[0], as well as the shape characteristics of ACF_L1 and ACF_L5).

[0053] Figure 5 This is a schematic diagram of a signal delay estimator 230 according to an embodiment of the present invention. Figure 5 As shown, the signal delay estimator 230 includes an L1 delay discriminator 510 and two L5 delay discriminators 520 and 530. In this embodiment, correlator 220 provides the lead code correlation value ACF_L1_E1 and the lag code correlation value ACF_L1_L1 of the L1 direct path signal to the L1 delay discriminator 510. Correlator 220 also provides the lead code correlation value ACF_L5_E1 and the lag code correlation value ACF_L5_L1 of the L5 direct path signal to the L5 delay discriminator 520, and provides the lead code correlation value ACF_L5_E2 and the lag code correlation value ACF_L5_L2 of the L5 reflected path signal to the L5 delay discriminator 530. Then, the L1 delay discriminator 510 uses the lead code correlation value ACF_L1_E1 and the lag code correlation value ACF_L1_L1 to calculate the signal delay of the direct path of the L1 signal. The L5 delay discriminator 520 uses the lead code correlation value ACF_L5_E1 and the lag code correlation value ACF_L5_L1 to estimate the signal delay of the L5 direct path signal. Furthermore, the L5 delay discriminator 520 uses the lead code correlation value ACF_L5_E2 and the lag code correlation value ACF_L5_L2 to estimate the signal delay of the L5 reflection path signal. After determining the signal delays of the L1 direct path signal, the L5 direct path signal, and the L5 reflection path signal, the L1 delay discriminator 510 can predict the signal delay of the L1 reflection path signal using the following equation:

[0054] T L1,RP = T L1,DP + (T L5,RP - T L5,DP )…(1);

[0055] where T L1,RP is the signal delay of the reflected path of the L1 signal (also described as "L1 reflected path signal"), T L1,DP is the signal delay of the direct path of the L1 signal (also described as "L1 direct path signal"), T L5,RP is the signal delay of the reflected path of the L5 signal (also described as "L5 reflected path signal"), and T L5,DP is the signal delay of the direct path of the L5 signal (also described as "L5 direct path signal"). In addition, the L1 delay discriminator 510 can predict the magnitude of the L1 reflected path signal as follows: M L1,RP = M L1,DP × (M L5,RP / M L5,DP )…(2);

[0056] where M L1,RP is the magnitude of the L1 reflected path signal, M L1,DP is the magnitude of the L1 direct path signal, M L5,RP is the magnitude of the L5 reflected path signal, and M L5,DP is the magnitude of the L5 direct path signal. Then, given the delay and magnitude of the L1 reflected signal and the shape of the ACF of the L1 reflected signal (which can be known according to the format of the local signal copy used), the L1 delay discriminator 510 can subtract the ACF-related result value of the L1 reflected signal from ACF_L1_L1 and / or ACF_L1_E1 to obtain a new / compensated early code correlation value ACF_L1_E1 and / or a new late code correlation value ACF_L1_L1 for determining the time delay of the direct path signal. For example, in Figure 4 , the original late code correlation value ACF_L1_L1 is adjusted to a new late code correlation value ACF_L1_L1' for the signal delay estimator 230 to calculate a new signal delay of the L1 signal.

[0057] In summary, by utilizing the information (correlation result) of the L5 signal, the ACF_L1 can be properly compensated to remove the effect of the L1 reflected path signal, so that the signal delay of the L1 signal can be more accurately determined (e.g., decomposed into ACF_L1_Direct and ACF_L1_Reflect) for subsequent signal processing by the signal processing circuit 240, such as determining the position of the electronic device and decoding the L1 signal.

[0058] It is noted that the GPS system is just an example, and the present application is not limited thereto. In other embodiments, the receiver 200 can support the Galileo satellite navigation system, and the receiver 200 can use E5a / E5b signals to estimate the reflected paths of E1 signals to compensate for the ACFs corresponding to the E1 signals. In some embodiments, the receiver 200 can support the BeiDou satellite navigation system, and the receiver 200 can use B2a / B2b signals to estimate the reflected paths of B1I / B1C signals to compensate for the ACFs corresponding to the B1I / B1C signals.

[0059] The use of ordinal terms such as "first", "second", "third", etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or to the temporal order in which acts are executed by the method actions, but are used merely as labels to identify elements having the same name (together with the ordinal term) in different claims.

[0060] While the present application has been described by way of example and in terms of preferred embodiments, it is to be understood that the application is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and equivalent structures (and functions) as would be apparent to one skilled in the art upon reading this description. Therefore, the scope of the claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures.

Claims

1. A receiver, characterized by The receiver comprises: a radio frequency (RF) circuit configured to receive a first satellite signal and a second satellite signal to generate a first baseband signal and a second baseband signal, respectively; a correlator configured to perform a correlation operation based on a first local signal replica and the first baseband signal to generate a first correlation result, and perform a correlation operation based on a second local signal replica and the second baseband signal to generate a second correlation result; a signal delay estimator coupled to the correlator and configured to compensate the first correlation result with the second correlation result to generate a compensated first correlation result, and determine a signal delay of the first satellite signal according to the compensated first correlation result.

2. The receiver of claim 1, wherein, An autocorrelation function (ACF) of the first satellite signal is different from an ACF of the second satellite signal.

3. The receiver of claim 2, wherein, A base of the ACF of the first satellite signal is wider than a base of the ACF of the second satellite signal.

4. The receiver of claim 1, wherein, The first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a global positioning system (GPS), a quasi-zenith satellite system (QZSS), a Galileo satellite navigation system, a Beidou satellite navigation system, a GLONASS system, an Indian regional navigation satellite system (NavIC), and a satellite-based augmentation system (SBAS).

5. The receiver of claim 1, wherein, The first correlation result is mixed from a first sub-correlation result corresponding to a direct path of the first satellite signal and a second sub-correlation result corresponding to a reflected path of the first satellite signal, and the second correlation result is mixed from a third sub-correlation result corresponding to a direct path of the second satellite signal and a fourth sub-correlation result corresponding to a reflected path of the second satellite signal; and the signal delay estimator predicts the second sub-correlation result according to the second correlation result, and compensates the first correlation result with the predicted second sub-correlation result to obtain a compensated first correlation result.

6. The receiver of claim 5, wherein, The first local signal replica and the second local signal replica used by the correlator are in formats based on a format of the first satellite signal and a format of the second satellite signal, respectively, the first correlation result is determined by an autocorrelation function (ACF) of the first satellite signal, and the second correlation result is determined by an ACF of the second satellite signal.

7. The receiver of claim 1, wherein, The first correlation result comprises m sample points, the second correlation result comprises n sample points, and the signal delay estimator compensates values of the m sample points of the first correlation result using a relationship between the m sample points of the first correlation result and the n sample points of the second correlation result.

8. The receiver of claim 7, wherein, m is equal to 2, and n is equal to 1.

9. The receiver of claim 7, wherein, The first correlation result comprises two sample points corresponding to a leading local signal replica and a lagging local signal replica of the first satellite signal.

10. The receiver of claim 7, wherein, The first correlation result comprises one sample point corresponding to an instant local signal replica of the first satellite signal.

11. The receiver of claim 7, wherein, The second correlation result comprises one sample point corresponding to an arbitrary time-delayed local signal replica of the second satellite signal, which is used to search for a possible reflected path signal of the second satellite signal.

12. The receiver of claim 7, wherein, The first correlation result includes one sample point of an immediate local signal replica corresponding to the first satellite signal, and the second correlation result includes two sample points of the immediate local signal replica corresponding to the direct path and the reflected path of the second satellite signal.

13. The receiver of claim 2, wherein, The first correlation result is mixed from a first ACF corresponding to a direct path of the first satellite signal and a second ACF corresponding to a reflected path of the first satellite signal, the second correlation result is mixed from a third ACF corresponding to a direct path of the second satellite signal and a fourth ACF corresponding to a reflected path of the second satellite signal, and the signal delay estimator predicts the second ACF according to early and late code correlation values of the third ACF and early and late code correlation values of the fourth ACF, and compensates the first ACF using the predicted second ACF.

14. The receiver of claim 13, wherein, The signal delay estimator compensates at least one of early and late code correlation values of the first ACF using the predicted second ACF.

15. A signal processing method, characterized by, The method comprises: receiving a first satellite signal and a second satellite signal to generate a first baseband signal and a second baseband signal, respectively; correlating a first local signal replica with the first baseband signal to generate a first correlation result; correlating a second local signal replica with the second baseband signal to generate a second correlation result; compensating the first correlation result using the second correlation result to compensate the first correlation result, and determining a signal delay of the first satellite signal according to the compensated first correlation result.

16. The signal processing method of claim 15, wherein, An autocorrelation function (ACF) of the first satellite signal is different from an ACF of the second satellite signal.

17. The signal processing method of claim 16, wherein, A base of the ACF of the first satellite signal is wider than a base of the ACF of the second satellite signal.

18. The signal processing method of claim 15, wherein, The first satellite signal and the second satellite signal are from a same satellite of a satellite system, and the satellite system comprises one of a global positioning system (GPS), a quasi-zenith satellite system (QZSS), a Galileo satellite navigation system, a Beidou satellite navigation system, a GLONASS system, an Indian regional navigation satellite system (NavIC), and a satellite-based augmentation system (SBAS).

19. The signal processing method of claim 15, wherein, The first correlation result is mixed from a first sub-correlation result corresponding to a direct path of the first satellite signal and a second sub-correlation result corresponding to a reflected path of the first satellite signal, and the second correlation result is mixed from a third sub-correlation result corresponding to a direct path of the second satellite signal and a fourth sub-correlation result corresponding to a reflected path of the second satellite signal; and the step of compensating the first correlation result using the second correlation result to generate a compensated first correlation result comprises: predicting the second sub-correlation result according to the second correlation result, and compensating the first correlation result using the predicted second sub-correlation result to obtain the compensated first correlation result.

20. The signal processing method of claim 19, wherein, The first and second local signal copies are formatted based on the format of the first and second satellite signals, respectively, the first correlation result is generated from an autocorrelation function (ACF) of the first satellite signal, and the second correlation result is generated from an ACF of the second satellite signal.

21. The signal processing method of claim 15, wherein, The first correlation result includes m sample points, the second correlation result includes n sample points, and the signal processing method further includes: Compensating values of the m sample points of the first correlation result using a relationship between the m sample points of the first correlation result and the n sample points of the second correlation result.

22. The signal processing method of claim 21, wherein, m equals 2 and n equals 1.

23. The signal processing method of claim 21, wherein, The first correlation result includes two sample points corresponding to early and late local signal copies of the first satellite signal.

24. The signal processing method of claim 21, wherein, The first correlation result includes one sample point corresponding to a prompt local signal copy of the first satellite signal.

25. The signal processing method of claim 21, wherein, The second correlation result includes one sample point corresponding to an arbitrary time-delayed local signal copy of the second satellite signal, which is used to search for a possible reflected path signal of the second satellite signal.

26. The signal processing method of claim 21, wherein, The first correlation result includes one sample point corresponding to a prompt local signal copy of the first satellite signal, and the second correlation result includes two sample points corresponding to prompt local signal copies of direct and reflected paths of the second satellite signal.

27. The signal processing method of claim 15, wherein, The first correlation result is a mixture of a first ACF and a second ACF, the first ACF corresponding to a direct path of the first satellite signal, and the second ACF corresponding to a reflected path of the first satellite signal; the second correlation result is a mixture of a third ACF and a fourth ACF, the third ACF corresponding to a direct path of the second satellite signal, and the fourth ACF corresponding to a reflected path of the second satellite signal; And Compensating the first correlation result using the second correlation result to generate a compensated first correlation result includes: predicting the second ACF from early and late code correlation values of the third ACF and early and late code correlation values of the fourth ACF, and compensating the first correlation result using the predicted second ACF.

28. The signal processing method of claim 27, wherein, Compensating the first correlation result using the predicted second ACF includes: compensating at least one of early and late code correlation values of the first ACF using the predicted second ACF. compensating at least one of early and late code correlation values of the first ACF using the predicted second ACF.

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