CN108008422B - Pseudo-satellite time-hopping signal acquisition device and method - Google Patents
Pseudo-satellite time-hopping signal acquisition device and method Download PDFInfo
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Abstract
The application discloses a pseudo-satellite time hopping signal capturing device and a pseudo-satellite time hopping signal capturing method. The pseudo-satellite time hopping signal acquisition method comprises the following steps: the time-hopping pulse position estimation of the pseudo satellite signal to be captured is obtained first, and then the Doppler estimation of the pseudo satellite signal to be captured is obtained. According to the pseudo-satellite time hopping signal capturing device and method, through separation and capture, the search dimensionality is reduced, and the calculation complexity is reduced.
Description
Technical Field
The present application relates to the field of navigation technologies, and in particular, to a pseudolite time hopping signal acquisition apparatus and method.
Background
In conventional satellite navigation systems, navigation satellites use Direct Sequence Spread Spectrum (DSSS) signals, and all satellites transmit signals simultaneously on the same carrier frequency in a Code Division Multiple Access (CDMA) format by using different spreading codes. In the capturing process, the receiver generally traverses all possible spread spectrum code phases and carrier doppler values in a two-dimensional grid search mode to generate a series of local recurrent signals, then performs correlation operation on the recurrent signals and the received signals, and obtains estimated values of the spread spectrum code phases and the carrier doppler values through the maximum correlation value.
Pseudolite systems largely use direct sequence spread spectrum signals of traditional GNSS systems, but because the distances between pseudolite system users and each pseudolite may be greatly different, a serious near-far effect problem is generated, and weak signals cannot be distinguished only by means of code division multiple access. In order to solve the problem, a time-hopping pulse transmitting mechanism is introduced on the basis of the traditional GNSS signals in the pseudolite system, namely a direct sequence spread spectrum-time hopping signal (TH-DSSS) system is adopted.
The direct sequence spread spectrum-time hopping signal system of a pseudolite system refers to dividing a pseudolite signal into successive time durations of TpA signal frame is divided into a plurality of pulse time slots TsEach pseudolite in a pseudolite system transmits a direct sequence spread spectrum pulse signal only at a certain pulse time slot within a complete signal frame. Thus, during a transmit cycle, different pseudolites will occupy different pulsesAnd (4) clearance. Meanwhile, in order to prevent the problem that the receiver is locked by mistake due to the influence of the period of the pulse signal of a certain pseudolite on the frequency spectrum of the positioning signal, a pseudolite designer presets a pseudorandom time hopping sequence for each pseudolite so as to mark the time slot of the satellite for transmitting the pulse signal. Figure 1 shows a direct sequence spread spectrum pulse signal transmitted by a certain pseudolite. Under the time hopping signal system, each pseudolite transmits the direct sequence spread spectrum pulse signal at an approximately random interval according to the time slot indicated by the time hopping sequence.
Although the TH-DSSS type signal system adopted by the pseudolite system inherits the characteristics of GNSS signals to a great extent, due to the unique time-hopping pulse characteristics, the commonly used acquisition algorithm in the GNSS system cannot be directly used for pseudolite signal acquisition. Therefore, it is necessary to design a stable and efficient pulse pseudolite signal acquisition scheme.
Disclosure of Invention
The application aims to provide a pseudo-satellite time hopping signal acquisition device and a pseudo-satellite time hopping signal acquisition method.
According to an aspect of the present application, there is provided a pseudolite time hopping signal acquisition method including: the time-hopping pulse position estimation of the pseudo satellite signal to be captured is obtained first, and then the Doppler estimation of the pseudo satellite signal to be captured is obtained.
According to an aspect of the present application, there is provided a pseudolite time hopping signal acquisition apparatus comprising: the time-hopping pulse position estimation unit is used for obtaining the time-hopping pulse position estimation of the pseudo satellite signal to be captured; and a Doppler estimation unit for obtaining Doppler estimation of the pseudo satellite signal to be captured.
According to the pseudo-satellite time hopping signal acquisition device and method, the computational complexity is reduced through separation acquisition.
Drawings
Fig. 1 shows a direct sequence spread spectrum pulse signal transmitted by a certain pseudolite under a pseudolite time hopping signal system.
Figure 2 shows the correlation of a single pulse signal in a pseudolite time hopping signal as a function of frequency error and spread spectrum code phase error.
FIG. 3 shows a block schematic diagram of a pseudolite time hopping signal acquisition device according to an embodiment of the present application.
Fig. 4 shows a schematic flow diagram of a pseudolite time hopping signal acquisition method according to an embodiment of the present application.
Figure 5 shows a block schematic diagram of a pseudolite time hopping signal acquisition device according to another embodiment of the present application.
Figure 6 shows an illustrative time hopping pattern in a pseudolite system represented in the form of a time hopping code table.
Fig. 7 shows a case where an envelope of an oscillation function corresponding to a time-hopping pulse signal including different numbers of pulses varies with a doppler estimation error according to an embodiment of the present application.
Fig. 8 shows the correlation result of the doppler estimation using multiple pulse signals according to an embodiment of the present application as a function of the doppler estimation error.
Detailed Description
The pseudo satellite time hopping signal acquisition apparatus and method disclosed in the present application will be described in detail with reference to the accompanying drawings. For the sake of simplicity, the same or similar reference numerals are used for the same or similar devices in the description of the embodiments of the present application.
In a pseudolite system, a signal s transmitted by a pseudolites(t) (taking BPSK modulation as an example) can be expressed as:
wherein, PsRepresenting the transmission power of the pseudolite signal, d (t) is the navigation message, c (t) is the spreading code of the pseudolite, fRFRepresenting the carrier frequency, phi, of the pseudolite signal0For the initial carrier phase, h (t) is the time hopping gating sequence. The time hopping gating sequence h (t) is a binary sequence with the value of 0,1,corresponding to the time hopping pattern of this satellite, the pulse transmission time slot specified in the time hopping pattern takes 1, and the other times take 0.
For a pseudolite system including Z pseudolites, the receiver receives a pseudolite time hopping signal sr(t) can be expressed as:
where i represents the pseudolite signal (or pseudolite base station) number, Z represents the number of base stations included in the current pseudolite system, and n (t) represents noise interference, typically white gaussian noise.
Indicating the signal received by the receiver from the ith pseudolite base station, PiRepresenting the received power of the signal, fIFRepresenting the nominal down-converted signal intermediate frequency of the receiver,
indicating the carrier doppler shift, phi, produced by the doppler effectiIndicating the initial received carrier phase of the time-hopped pulse signal.
In general, the text in the received signal is a slowly varying quantity, the presence or absence of which does not affect the capture of the signal, and the received signal power PiGenerally, the value is constant, and the method has no essential influence on the analysis. For convenience of subsequent description, text items, signal receiving power items, time-hopping pulse signals
Expressed as:
it can be understood that, since the receiver usually performs the down-conversion processing on the received signal and then performs the acquisition processing, the received signal mentioned in this application refers to the signal after the down-conversion processing by the receiver.
When a receiver receives the time hopping signal of the pseudo satellite and needs to capture a pseudo satellite signal, the method for capturing the satellite signal in the reference GNSS system comprises the following steps: and locally generating a reproduced signal with different spreading codes and carrier Doppler shift and a time slot length, and carrying out correlation operation on the reproduced signal and the received signal to obtain a time-hopping pulse position and carrier Doppler estimation. However, since this method requires a two-dimensional search for the pulse position and doppler shift, the computational complexity is high. In addition, because the method carries out pulse position and Doppler estimation based on a recurrent signal with a time slot length, and the pulse time slot of a pseudo-satellite time hopping signal is short, the relevant result changes slowly along with the change of a carrier Doppler estimation error when the time slot length is processed, and thus the acquisition mode is difficult to obtain correct estimation. In addition, if the time-hopping signal is modulated by QPSK, the peak of the correlation operation deviates from the true estimation value of the carrier doppler, and this acquisition method cannot obtain a correct doppler estimation. Moreover, the duty ratio of the pseudolite signal is low, and the method often needs to carry out multiple times of useless detection at the position where no pulse exists before a pulse is successfully detected, so that the algorithm efficiency is low.
For this reason, in the present application, the characteristics of the pseudolite time hopping signal are studied. Typically, the pseudolites (pseudolites base stations) in a pseudolites system are stationary, and thus the doppler shift in the pseudolites system is mainly caused by the motion of the user and the drift of the receiver clock. For example, for an L-band pseudolite signal, a relative motion of 150m/s causes a Doppler shift of no more than 998Hz, and a frequency offset of 1ppm of the receiver clock corresponds to a frequency offset of about 2000 Hz. Combining the above two factors, it can be considered that the maximum doppler shift amount is ± 3kHz when the receiver in the general pseudolite system receives the pseudolite signal. Figure 2 shows the correlation of a single pulse signal in a pseudolite time hopping signal as a function of frequency error and spread spectrum code phase error. As shown, the correlation values are attenuated by only less than 15% at most even at the maximum doppler shift. In addition, a significant correlation peak occurs at the appropriate spreading code phase throughout the range of doppler shifts.
Therefore, in the method, when the time hopping signal of the pseudolite is captured, even if the influence of carrier Doppler is ignored in the processing process, the pulse position can be accurately estimated through the spread spectrum code, and the Doppler shift can be further estimated after the pulse position is obtained. By utilizing the characteristic, the separated acquisition of the time hopping signal can be realized. FIG. 3 shows a block schematic diagram of a pseudolite time hopping signal acquisition device according to an embodiment of the present application. As shown in fig. 3, the time hopping signal acquisition apparatus 10 according to one embodiment of the present application includes a time hopping pulse position estimation unit 100 and a doppler estimation unit 200. The time-hopping pulse position estimation unit 100 obtains a time-hopping pulse position estimate of a pseudolite signal to be acquired. The doppler estimation unit 200 obtains a doppler estimate of the pseudolite signal to be acquired. Fig. 4 shows a schematic flow diagram of a pseudolite time hopping signal acquisition method according to an embodiment of the present application. As shown in fig. 4, in step 301, a time-hopping pulse position estimate of a pseudolite signal to be acquired is obtained. Then, in step 302, a Doppler estimate of the pseudolite signal to be acquired is obtained. According to one embodiment, for example, a time-hopping pulse position estimate of the pseudolite signal to be acquired may be obtained in step 301 from a spreading code signal of the pseudolite signal to be acquired. From the obtained time-hopping pulse position estimates, a plurality of pulse positions in the received signal corresponding to the pseudolite signal to be acquired can be determined, so that in step 302, a doppler estimate of the pseudolite signal to be acquired is obtained by multi-pulse joint estimation.
Therefore, through separation and capture, the search dimension is reduced, and the calculation complexity is reduced.
Figure 5 shows a block schematic diagram of a pseudolite time hopping signal acquisition device according to another embodiment of the present application. As shown in fig. 5, the time-hopping pulse position estimation unit 100 further includes a spreading code signal generator 110 and a processor 120. The doppler estimation unit 200 further comprises a time hopping pulse signal generator 210 and a processor 220. The spreading code signal generator 110 locally reproduces the spreading code signal of the pseudolite to be acquired for one slot length. The processor 120 performs correlation operation on the reproduced spread spectrum code signal and the received signal to obtain a time-hopping pulse position estimate of the pseudo satellite signal to be captured. The time-hopping pulse signal generator 210 locally reproduces the time-hopping pulse signal of the pseudolite to be acquired containing doppler information, based on the obtained time-hopping pulse position estimate. The processor 220 determines a signal corresponding to the position of the reproduced time-hopping pulse signal in the received signal according to the obtained time-hopping pulse position estimation, and performs correlation operation on the reproduced time-hopping pulse signal and the received signal corresponding to the position to obtain the doppler estimation of the pseudo satellite signal to be captured. According to the method and the device, the pulse position estimation is obtained firstly, so that the high-precision Doppler estimation can be realized by combining time-hopping pulse signals of a plurality of positions subsequently. Moreover, signals corresponding to the position of the reproduced time-hopping pulse signal in the received signals can be selected to carry out correlation operation, useless operation is eliminated, and algorithm efficiency is improved.
According to an embodiment of the present application, in the separation acquisition, the spreading code signal c (t) of the pseudolite to be acquired, which is one time slot in length, is first locally reproduced, and c (t) generally includes two orthogonal spreading code signals of the pseudolite to be acquired
Wherein W represents the number of the signal to be captured, and cW(t) then represents the spreading code used by the pseudolite to be acquired, fIFWhich represents the nominal down-converted signal intermediate frequency of the receiver. It can be seen that the reproduced spreading code signal does not contain doppler information. The reproduced spread spectrum code signal is processed with the received signalAnd performing correlation operation to obtain the time-hopping pulse position estimation of the pseudo satellite signal to be captured.
According to one embodiment, a repeated spreading code signal with a time slot length is subjected to sliding correlation with a received signal with more than one signal frame length, and a start pulse position is obtained. For example, the maximum correlation value v may be searchedindexThe corresponding position is used as the starting pulse position. In the sliding correlation operation, an overlap-and-hold method can be adopted to accelerate the calculation and reduce the operation complexity.
After the starting pulse position is obtained, the subsequent pulse position can be obtained by continuing with the sliding correlation. However, since the computation complexity of the sliding correlation is relatively high, according to an embodiment of the present application, a subsequent time slot position can be determined according to the obtained start pulse position, and a reproduced spreading code signal with a time slot length and a received signal corresponding to each subsequent time slot position are subjected to correlation computation to obtain a plurality of subsequent pulse positions. Because the pulse time slot length is fixed, after the initial pulse position is obtained, each subsequent time slot position can be determined, and therefore the repeated spread spectrum code signal with one time slot length and the received signal corresponding to each subsequent time slot position can be subjected to correlation operation to obtain a correlation value. If the correlation value corresponds to the correlation value v corresponding to the start pulse positionindexAnd if the comparison exceeds the judgment threshold, the time slot position corresponding to the correlation value is considered to detect the pulse signal, so that the subsequent pulse position is obtained. In this way, correlation operation can be performed only for the received signal corresponding to each slot position, and the complexity of the correlation operation is reduced. In order to prevent a correlation loss due to an estimated deviation of the start position, a correlation operation may be performed near the start position of each slot. For example, the maximum correlation value v can be found by correlating the locally recurring spreading code within one or more spreading code chips before and after the beginning of each subsequent time slot as the centertemp. If v istemp/vindexAbove a certain threshold, the pulse signal is considered to be found here and the pulse position is recorded.
Each pseudolite in a pseudolite systemThe time hopping patterns (time hopping patterns) of the satellites themselves are fixed, and the time hopping patterns of pseudolites can be generally represented in the form of a time hopping code table. Figure 6 shows an illustrative time hopping pattern in a pseudolite system represented in the form of a time hopping code table. Each column PL _1, …, PL _ N in the table corresponds to a pseudolite, and each row 1, …, NhCorresponding to a signal frame, each cell represents the transmission time slot position occupied by the pseudolite corresponding to the column number in the signal frame corresponding to the row number. In addition, it can be seen that all pseudolites in the system select different time slots to transmit signals within the same signal frame, thereby avoiding mutual interference. For a pseudolite, it is at NhIn each signal frame, a time slot is selected to transmit signals in a pseudo-random mode all the time. A column vector in the time hopping code table that specifies the time hopping pattern of a pseudolite is commonly referred to as the time hopping sequence for that pseudolite. In addition to such standard time hopping patterns, the time hopping pattern of a pseudolite is typically given in the form of a differential code table in which each cell thereof represents a pulse interval. After obtaining a plurality of pulse positions, the pulse positions that have been obtained can be matched to the pulse positions indicated in the time hopping code table, the number of the current signal frame can be obtained, and the positions of all subsequent pulses can be found to obtain a time hopping pulse position estimate. During matching, the number of pulse positions to be obtained in advance can be determined according to the rule of the time hopping code table.
After the time-hopped pulse position estimate is obtained, a doppler estimate may be further obtained from the obtained time-hopped pulse position estimate. According to an embodiment of the present application, a multi-pulse joint estimation may be employed to obtain a more accurate doppler estimate based on the obtained time-hopping pulse position estimate. Since the time-hopping pulse position estimate is obtained first, a pulse signal containing doppler information at a plurality of pulse positions, i.e., a time-hopping pulse signal, can be reproduced locally. Signal positions corresponding to a plurality of pulse positions of the reproduced time-hopping pulse signal are determined in the received signal. And performing correlation operation on the reproduced time hopping pulse signal containing the Doppler information and the pulse signal at the corresponding position in the received signal, and determining the Doppler estimation of the pseudo satellite signal to be captured according to the correlation operation result.
Locally reproducing a time-hopping pulse signal s containing Doppler informationn,k(t)，sn,k(t) may generally comprise two orthogonal time-hopped pulse signals
Which can be expressed as:
where n · Δ f represents doppler information included in the reproduced signal, Δ f represents a search step of doppler shift, n represents a search number,
representing the initial carrier phase of the reproduced signal,
indicating the position of the kth pulse, R, obtained in the estimation of the position of the previous time-hopped pulsesRepresents the sampling rate of the signal employed by the receiver, then
It is indicated at the start of the pulse,
the end time of the pulse is corresponded.
By adjusting the search number n, the doppler information of the time-hopping pulse signal will include a series of doppler shifts. In this way, by performing correlation operation on the time-hopping pulse signal containing each doppler shift and the pulse signal at the corresponding position in the received signal, the doppler shift value of the time-hopping pulse signal corresponding to the maximum correlation value is searched to be the doppler estimation of the pseudolite signal to be acquired.
Wherein, the correlation operation can be expressed by the following formula:
wherein,
indicating the obtained I-way correlation result,
representing the obtained Q-way correlation result, A representing the signal amplitude, M representing the number of pulses contained in the reproduced time-hopping pulse signal, nI,nQBoth represent noise terms. The integral envelope after the correlation operation can be further deduced to be represented as:
where n is a noise-induced interference term, OM(. is an oscillatory function generated by the non-uniformity of selected pulse intervals, which takes on values dependent on the interval Δ and frequency difference n · Δ f-f of the pulses contained in the time-hopped pulse signali dAnd (4) determining. The following exemplary specific expression of the oscillational function when M takes 3 is given:
due to the non-uniformity of the pulse intervals, the oscillation function can fluctuate rapidly in the estimation interval so as to accelerate the change of the integration result along with the Doppler estimation error, and therefore, the change of the integration envelope after the correlation operation along with the Doppler estimation error is accelerated. In this way, the doppler estimate is determined based on the correlation operation, and a highly accurate doppler estimate value can be obtained.
Fig. 7 shows the variation of the envelope of the oscillation function corresponding to the time-hopping pulse signal containing different numbers of pulses with the doppler estimation error. It can be seen that increasing the number of pulses M used in the time-hopping integration can accelerate the fluctuation of the oscillation function and further narrow the width of the correlation peak; however, as M increases, the gain obtained by continuing to increase the number of pulses decreases, but the amount of computation required for processing continues to increase. In practical applications, the two conditions can be balanced, and the number of the reproduced pulses of the time-hopping pulse signal can be selected.
By the multi-pulse combined Doppler estimation mode, time hopping pulse signals can be reproduced, and only correlation operation is carried out in an effective time slot (corresponding pulse signals) in the received signals, so that useless calculation can be reduced, and strong interference at other positions can be effectively avoided. Furthermore, the above method can increase the effective integration time of the correlation operation, and on the other hand, the sensitivity of the correlation result to the frequency error is significantly improved due to the longer interval between two adjacent pulses, so as to obtain an accurate doppler estimation result.
In addition, since the oscillation function has a certain periodicity, a secondary peak exists in the correlation operation result, and the secondary peak may cause doppler misestimation in the case of strong noise or strong interference. As can be seen from the specific expression of the oscillation function, the oscillation function OM(Δ,fe) Will vary with the pulse interval a. Therefore, as long as Δ changes, the specific expression of the oscillation function changes, and the frequency of the occurrence of the secondary peak in the time-hopping integration result changes, while the position of the primary peak does not change but is at the correct doppler frequency position. Fig. 8 shows the trend of the correlation result with the variation of the doppler estimation error when the doppler estimation is performed using a plurality of sets of pulse signals. As shown, the positions of all the main peaks (1, 2, 3 marked by circles in the figure) appear at the frequency estimation error of 0, and the positions of the sub-peaks (1, 2, 3 marked by boxes in the figure) appear as a function of the pulse interval. The time-hopping signals used by pseudolites are characterized by pulse intervals with a certain uncertainty, so that by utilizing the characteristics, selected pulse positions can be adjusted, multiple groups of signals can be locally reproduced, each group of signals comprises pulse signals positioned at multiple pulse positions, and each group of signals containing Doppler informationAnd performing incoherent accumulation on the correlation operation result corresponding to the signal, and determining the Doppler estimation of the pseudo-satellite signal to be captured according to the incoherent accumulation result, so that the influence caused by a secondary peak can be weakened, and the accuracy of the Doppler estimation is further improved.
In addition, in the pseudolite system, since time synchronization is required between pseudolite base stations in the system, time adjustment information needs to be transmitted. Pseudolite systems sometimes require very high message rates, such as up to 500bps, to facilitate information transfer. Such high rate messages may cause frequent message bit reversals. According to an embodiment of the present application, a capture method capable of solving the text bit inversion problem is further provided.
According to the capturing method, when the time-hopping pulse position is estimated, a mode based on single pulse processing is adopted, and the pulse estimation result cannot be influenced by text bit inversion. In Doppler estimation, multi-pulse joint estimation is adopted, and the problem of text bit inversion needs to be considered.
If the existence of the text is considered, when the kth pulse signal is integrated in the multi-pulse joint estimation, the integration result of a single time slot is as follows:
it will be appreciated that in the case of joint multi-slot estimation, due to dkThe value of (b) may be positive or negative, and if the effect of text bit inversion cannot be correctly eliminated, very serious correlation loss may be caused, thereby causing an error in the doppler estimation result. However, due to the text d carried by the pulsekE {1, -1}, if the integration result I can be integratedn,kAnd Qn,kAre respectively multiplied by
The effect of text bit inversion can be eliminated, namely:
although d cannot be accurately obtained at the current stagekHowever, the value is limited, and can be determined by traversing all possible values and then finding the maximum value. Assuming that there is a possibility of message inversion in each pulse, if M slots are used for joint estimation, there is a total of 2 messagesMAnd/2 (if the text is totally evaluated, the result is not influenced) different types of combinations. Therefore, I can be calculated in each text combination moden,kAnd Qn,kThen according to different text combinations do 2MAnd/2 times of summation, calculating the correlation values of the time hopping pulse signals containing Doppler information and the received signals corresponding to the positions under all the telegraph text combinations, searching the maximum correlation value, obtaining Doppler estimation, and eliminating the influence caused by the telegraph text. It can be understood that when the method is used for eliminating text bit inversion, local signals do not need to be reproduced additionally, extra correlation operation does not need to be carried out, summation operation only needs to be carried out according to different text combinations, and therefore the calculation complexity is very small.
Exemplary embodiments of the present application are described above with reference to the accompanying drawings. It will be appreciated by those skilled in the art that the above-described embodiments are merely exemplary for purposes of illustration and are not intended to be limiting, and that any modifications, equivalents, etc. that fall within the teachings of this application and the scope of the claims should be construed to be covered thereby.
Claims (14)
1. A pseudolite time hopping signal acquisition method, comprising:
firstly, time-hopping pulse position estimation of a pseudo satellite signal to be captured is obtained, and then Doppler estimation of the pseudo satellite signal to be captured is obtained;
locally reproducing a spread spectrum code signal of a pseudo satellite to be captured in a time slot length, and carrying out correlation operation on the reproduced spread spectrum code signal and a received signal to obtain a time-hopping pulse position estimation of the pseudo satellite signal to be captured; and
according to the obtained time-hopping pulse position estimation, the time-hopping pulse signals of the pseudo satellite to be captured containing Doppler information are locally reproduced, signals corresponding to the position of the reproduced time-hopping pulse signals in the received signals are determined, the reproduced time-hopping pulse signals and the received signals corresponding to the position are subjected to correlation operation, and the Doppler estimation of the pseudo satellite signals to be captured is obtained.
2. The pseudolite time hopping signal acquisition method of claim 1 comprising: obtaining the time-hopping pulse position estimation of the pseudolite signal to be captured through the spread spectrum code signal of the pseudolite to be captured; and obtaining the Doppler estimation of the pseudo satellite signal to be acquired through multi-pulse joint estimation according to the obtained time-hopping pulse position estimation.
3. The pseudolite time hopping signal acquisition method according to claim 1, wherein a repeated spread spectrum code signal of one time slot length and a received signal of more than one signal frame length are subjected to sliding correlation operation to obtain a start pulse position; determining the position of a subsequent time slot according to the obtained initial pulse position, and performing correlation operation on the reproduced spread spectrum code signal with the length of one time slot and the received signal corresponding to each subsequent time slot position to obtain a plurality of subsequent pulse positions; matching the starting pulse position and the subsequent pulse positions with a time hopping pattern of a pseudolite to be captured, and determining all pulse positions to obtain a time hopping pulse position estimate.
4. A pseudolite time hopping signal acquisition method as set forth in claim 1, wherein the reproduced time hopping pulse signal includes pulse signals at a plurality of pulse positions determined from the time hopping pulse position estimate.
5. The method of claim 1, wherein the doppler information comprises a series of doppler shifts, and the time-hopping pulse signal containing each doppler shift is correlated with the received signal at the corresponding location, and the doppler shift corresponding to the maximum correlation value is searched to determine the doppler estimate of the pseudolite signal to be acquired.
6. The method of pseudolite time hopping signal acquisition of claim 1, wherein the recurring time hopping pulse signals include a plurality of sets of signals, each set of signals in the plurality of sets of signals includes a pulse signal located at a plurality of pulse positions, each set of signals including doppler information is correlated with a received signal corresponding to a position of the set of signals, correlation results corresponding to each set of signals are incoherently accumulated, and a doppler estimate of the pseudolite signal to be acquired is determined based on the incoherence accumulation results.
7. The method of claim 1, wherein all telegraph text combination modes corresponding to the pulse signals at the pulse positions of the reproduced time-hopping pulse signal are determined, correlation is performed on the reproduced time-hopping pulse signal containing doppler information and the received signal corresponding to the position in each telegraph text combination mode, and the doppler estimation of the pseudolite signal to be acquired is determined according to the correlation calculation result in each telegraph text combination mode.
8. A pseudolite time hopping signal acquisition device, comprising:
the time-hopping pulse position estimation unit is used for obtaining the time-hopping pulse position estimation of the pseudo satellite signal to be captured; and
a Doppler estimation unit for obtaining Doppler estimation of pseudo satellite signals to be captured,
wherein the time hopping information estimating unit includes a spread code signal generator and a first processor,
the spread spectrum code signal generator locally reproduces a spread spectrum code signal of a pseudo satellite to be captured with a time slot length; and
the first processor performs correlation operation on the reproduced spread spectrum code signal and the received signal to obtain the time-hopping pulse position estimation of the pseudo satellite signal to be captured,
wherein the Doppler estimation unit comprises a time hopping pulse signal generator and a second processor,
the time-hopping pulse signal generator estimates from the obtained time-hopping pulse positions,
locally reproducing a time hopping pulse signal of a pseudo satellite to be captured, which contains Doppler information; and
and the second processor determines a signal corresponding to the position of the reproduced time hopping pulse signal in the received signals, and performs correlation operation on the reproduced time hopping pulse signal and the received signal corresponding to the position to obtain the Doppler estimation of the pseudo satellite signal to be captured.
9. The pseudolite time hopping signal acquisition apparatus of claim 8, wherein the time hopping pulse position estimation unit obtains a time hopping pulse position estimate of a pseudolite signal to be acquired through a spread spectrum code signal of the pseudolite signal to be acquired; and the Doppler estimation unit obtains the Doppler estimation of the pseudo satellite signal to be captured through multi-pulse joint estimation according to the obtained time-hopping pulse position estimation.
10. The pseudo-satellite time hopping signal acquisition apparatus according to claim 8, wherein the first processor performs a sliding correlation operation on a reproduced spreading code signal of one time slot length and a received signal of more than one signal frame length to obtain a start pulse position; determining the position of a subsequent time slot according to the obtained initial pulse position, and performing correlation operation on the reproduced spread spectrum code signal with the length of one time slot and the received signal corresponding to each subsequent time slot position to obtain a plurality of subsequent pulse positions; matching the starting pulse position and the subsequent pulse positions with a time hopping pattern of a pseudolite to be captured, and determining all pulse positions to obtain a time hopping pulse position estimate.
11. A pseudolite time hopped signal acquisition apparatus as set forth in claim 8, wherein the time hopped pulse signal reproduced by said time hopped pulse signal generator comprises pulse signals at a plurality of pulse positions determined from said time hopped pulse position estimate.
12. The pseudolite time hopping signal acquisition device of claim 8, wherein the doppler information comprises a series of doppler shifts, the second processor correlates the time hopping pulse signal containing each doppler shift with the received signal at the corresponding location, searches for the doppler shift corresponding to the maximum correlation value, and determines the doppler estimate of the pseudolite signal to be acquired.
13. The pseudolite time hopping signal acquisition device of claim 8, wherein the time hopping pulse signal reproduced by the time hopping pulse signal generator comprises a plurality of sets of signals, each set of signals in the plurality of sets of signals comprises a pulse signal at a plurality of pulse positions, the second processor performs correlation operation on each set of signals containing doppler information and a received signal corresponding to the position of the set of signals, performs incoherent accumulation on the correlation operation results corresponding to each set of signals, and determines the doppler estimation of the pseudolite signal to be acquired according to the incoherent accumulation result.
14. The pseudolite time hopping signal acquisition device of claim 8, wherein the second processor determines all telegraph text combination modes corresponding to the pulse signals at a plurality of pulse positions of the reproduced time hopping pulse signal, performs correlation operation on the reproduced time hopping pulse signal containing doppler information and the received signal corresponding to the position in each telegraph text combination mode, and determines the doppler estimation of the pseudolite signal to be acquired according to the correlation operation result in each telegraph text combination mode.
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