Single-antenna satellite navigation signal tracking method under carrier high-speed rotation condition

Abstract

The invention relates to the technical field of satellite navigation, and discloses a single-antenna satellite navigation signal tracking method under a carrier high-speed rotation condition. The method comprises the following steps: capturing a navigation signal; tracking the captured navigation signal by adopting a loop filter and a code loop; and performing energy judgment on the signal locked in the tracking process. When a satellite signal is received, the rough Doppler frequency offset of the signal is obtained by capturing, and then the tracking process is carried out, and the Doppler frequency offset is estimated more finely, so that the carrier Doppler frequency offset and the code Doppler frequency offset of the locally generated satellite synchronization signal are closer to the real satellite signal, and the problem that in the tracking process, the Doppler frequency offset cannot be accurately estimated is solved. And the subsequent synchronization process cannot be carried out due to overlarge frequency error or incapability of locking, and normal work of the satellite navigation receiver can be ensured.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation technology, and in particular to a single-antenna satellite navigation signal tracking method under conditions of high-speed carrier rotation. Background Technology

[0002] Many modern aircraft carriers incorporate high-speed rotation capabilities into their control chains for aerodynamic purposes or other uses. Under high-speed rotation conditions, such as 100–400 r / s, satellite signals received by a single-antenna carrier will be distorted due to the carrier's own obstruction. Furthermore, the dynamic characteristics introduced by rotation will also affect satellite signal reception. Conventional satellite navigation receiver tracking loops can no longer accurately lock onto the signal, rendering positioning and velocity measurement functions impossible. Therefore, it is necessary to research single-antenna satellite navigation signal tracking methods under high-speed rotation conditions to ensure the normal operation of the satellite navigation receiver and provide positioning and velocity measurement results for the carrier. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-antenna satellite navigation signal tracking method under high-speed carrier rotation conditions, which can solve the satellite navigation signal tracking problem in the prior art.

[0004] The technical solution of this invention: a single-antenna satellite navigation signal tracking method under high-speed carrier rotation conditions, wherein the method includes:

[0005] Capture navigation signals;

[0006] The captured navigation signal is tracked using a loop filter and a code loop;

[0007] Energy determination is performed on the signals locked during the tracking process.

[0008] Preferably, a short-time correlation matched filter and a combination of FFT and PMF-FFT are used to capture navigation signals.

[0009] Preferably, tracking the captured navigation signal using a loop filter includes:

[0010] Set up one channel for noise floor statistics and obtain the noise channel coherence integral result I. N ;

[0011] Calculate the frequency discrimination error f e Phase detection error φ e ;

[0012] Based on the frequency discrimination error f e Phase detection error φ e Calculate the input of the loop filter;

[0013] The filter output result u is obtained from the loop filter input. f (s);

[0014] For the filter output result u f (s) Perform a bilinear transformation to obtain the transformed result u. f (z).

[0015] Preferably, the frequency discrimination error f is calculated using the following formula. e Phase detection error φ e :

[0016]

[0017] cross=I(n-1)Q(n)-Q(n-1)I(n),

[0018] dot=I(n-1)I(n)+Q(n-1)Q(n),

[0019] Where cross represents the cross product, dot represents the dot product, and T coh Q represents the coherent integration time. P I represents the instantaneous coherent integral result of the Q branch. P Let I(n) represent the current coherent integration result of branch I, I(n-1) represent the coherent integration result of branch I in the current frame, I(n-1) represent the coherent integration result of branch I in the previous frame, Q(n) represent the current coherent integration result of branch Q, and Q(n-1) represent the coherent integration result of branch Q in the previous frame.

[0020] Preferably, the frequency discrimination error f is determined by the following formula. e Phase detection error φ e Calculate the input of the loop filter:

[0021] c1 = f e a2ω nf

[0022]

[0023] c5=φ e b3ω n ,

[0024] Where c1, c2, c3, c4, and c5 are all filter inputs, a2, a3, and b3 are filter parameters, and ω... nf ω is the characteristic frequency of the frequency-locked loop. n This is the characteristic frequency of the phase-locked loop.

[0025] Preferably, the filter output result u is obtained from the loop filter input using the following formula. f (s):

[0026]

[0027] Where s is the generalized complex frequency of the continuous-time system.

[0028] Preferably, the filter output result u is expressed by the following formula. f (s) Perform a bilinear transformation to obtain the transformed result u. f (z):

[0029]

[0030] Where z is the generalized complex frequency of the discrete-time system.

[0031] Preferably, tracking the captured navigation signal using a code loop comprises the following formula:

[0032]

[0033] Where, δ cp (n) represents the current phase detection error of the timing code. This is the output result of the code ring in the previous cycle, where α is the code ring loop parameter.

[0034] Preferably, energy determination of the signal locked during tracking includes:

[0035] Calculate the current beat signal energy P(n);

[0036] Based on the noise channel coherence integral result I N Calculate the noise channel power P N ;

[0037] Based on the current image signal energy P(n) and the coherent integral result of the noise channel I... N Calculate the current energy ratio ρ;

[0038] If the current energy ratio ρ is greater than the threshold, the loop filter and code loop will provide feedback normally.

[0039] If the current energy ratio ρ is less than or equal to the threshold, feedback from the loop filter and code loop is disabled.

[0040] Preferably, the current beat signal energy P(n) is calculated using the following formula:

[0041] P(n)=I 2 (n)+Q 2 (n);

[0042] The noise channel power P is calculated using the following formula. N :

[0043]

[0044] The current energy ratio ρ is calculated using the following formula:

[0045]

[0046] Through the above technical solution, when the satellite signal is received, the coarse Doppler frequency offset of the signal is captured, and then transferred to the tracking process to make a more precise estimate of the Doppler frequency offset. This makes the carrier Doppler frequency offset and code Doppler frequency offset of the locally generated satellite synchronization signal closer to the real satellite signal, which solves the problem that the frequency error is too large or cannot be locked during the tracking process, thus preventing the subsequent synchronization process from being carried out. This ensures that the satellite navigation receiver can work normally. Attached Figure Description

[0047] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0048] Figure 1 A flowchart of a single-antenna satellite navigation signal tracking method under high-speed carrier rotation conditions provided in an embodiment of the present invention;

[0049] Figure 2 This is a block diagram of the signal acquisition scheme in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of a loop filter in an embodiment of the present invention. Detailed Implementation

[0051] Specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, specific details are set forth for purposes of explanation and not limitation, in order to aid in a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced in other embodiments departing from these specific details.

[0052] It should be noted that, in order to avoid obscuring the invention with unnecessary details, only the device structure and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0053] Figure 1 A flowchart of a single-antenna satellite navigation signal tracking method under high-speed carrier rotation conditions provided in an embodiment of the present invention.

[0054] like Figure 1As shown, this embodiment of the invention provides a single-antenna satellite navigation signal tracking method under conditions of high-speed carrier rotation, wherein the method includes:

[0055] Capture navigation signals;

[0056] Among these, the coarse Doppler frequency offset of the signal can be obtained by capturing it.

[0057] The captured navigation signal is tracked using a loop filter (carrier loop) and a code loop (code loop);

[0058] Energy determination is performed on the signals locked during the tracking process.

[0059] Through the above technical solution, when the satellite signal is received, the coarse Doppler frequency offset of the signal is captured, and then transferred to the tracking process to make a more precise estimate of the Doppler frequency offset. This makes the carrier Doppler frequency offset and code Doppler frequency offset of the locally generated satellite synchronization signal closer to the real satellite signal, which solves the problem that the frequency error is too large or cannot be locked during the tracking process, thus preventing the subsequent synchronization process from being carried out. This ensures that the satellite navigation receiver can work normally.

[0060] According to one embodiment of the present invention, such as Figure 2 As shown, a short-time correlation matched filter and a combination of FFT and PMF-FFT are used to capture navigation signals.

[0061] According to one embodiment of the present invention, tracking the captured navigation signal using a loop filter includes:

[0062] Set up one channel for noise floor statistics and obtain the noise channel coherence integral result I. N ;

[0063] For example, assuming a satellite signal at frequency B1I is used, the non-existent PRN code 0 is selected and correlated with the received signal to obtain the coherent integral result I of the noise channel. N The same applies to B3I and other frequency points.

[0064] Calculate the frequency discrimination error f e Phase detection error φ e ;

[0065] Based on the frequency discrimination error f e Phase detection error φ e Calculate the input of the loop filter;

[0066] The filter output result u is obtained from the loop filter input. f (s);

[0067] For the filter output result u f (s) Perform a bilinear transformation to obtain the transformed result u.f (z).

[0068] Because it is applicable to high-speed rotating scenarios, carrier tracking (loop filter tracking) can employ a second-order frequency-locked loop assisted by a third-order phase-locked loop (traditional second-order assisted third-order loop) to resist dynamics. The loop filter is as follows: Figure 3 As shown. Among them, the frequency and phase detection adopts the two-quadrant arctangent phase detection method.

[0069] According to one embodiment of the present invention, when the coherence integration time is T coh At that time, the frequency discrimination error f is calculated using the following formula. e Phase detection error φ e :

[0070]

[0071] cross=I(n-1)Q(n)-Q(n-1)I(n),

[0072] dot=I(n-1)I(n)+Q(n-1)Q(n),

[0073] Where cross represents the cross product, dot represents the dot product, and T coh Q represents the coherent integration time. P I represents the instantaneous coherent integral result of the Q branch. P Let I(n) represent the current coherent integration result of branch I, I(n-1) represent the coherent integration result of branch I in the current frame, I(n-1) represent the coherent integration result of branch I in the previous frame, Q(n) represent the current coherent integration result of branch Q, and Q(n-1) represent the coherent integration result of branch Q in the previous frame.

[0074] According to one embodiment of the present invention, the frequency discrimination error f is determined by the following formula. e Phase detection error φ e Calculate the input of the loop filter:

[0075] c1 = f e a2ω nf

[0076]

[0077] c5=φ e b3ω n ,

[0078] Where c1, c2, c3, c4, and c5 are all filter inputs (loop inputs), a2, a3, and b3 are filter parameters (loop parameters), and ω nf ω is the characteristic frequency of the frequency-locked loop. n This is the characteristic frequency of the phase-locked loop.

[0079] According to one embodiment of the present invention, the filter output result u is obtained from the loop filter input using the following formula. f (s):

[0080]

[0081] Where s is the generalized complex frequency of the continuous-time system.

[0082] According to one embodiment of the present invention, the filter output result u is expressed by the following formula. f (s) Perform a bilinear transformation to obtain the transformed result u. f (z):

[0083]

[0084] Where z is the generalized complex frequency of the discrete-time system.

[0085] Therefore, the signal can be tracked and fed back according to the above formula.

[0086] For example, the loop parameters can be taken as the following ideal parameters:

[0087] a2 = 1.414

[0088] a3 = 1.1

[0089] b3 = 2.4

[0090] ω n =B PLL / 0.7845

[0091] ω nf =B FLL / 0.53,

[0092] Among them, B PLL For the phase-locked loop bandwidth, B FLL This is the bandwidth of the frequency-locked loop.

[0093] According to one embodiment of the present invention, tracking the captured navigation signal using a code loop via the following formula includes:

[0094]

[0095] Where, δ cp (n) represents the current phase detection error of the timing code. This is the output result of the code ring in the previous cycle. α is the code ring loop parameter, which is usually not less than 0.9.

[0096] In this invention, the code loop (code tracking) can be a first-order loop.

[0097] According to one embodiment of the present invention, energy determination of a signal locked during tracking includes:

[0098] Calculate the current beat signal energy P(n);

[0099] Based on the noise channel coherence integral result I N Calculate the noise channel power P N ;

[0100] Based on the current image signal energy P(n) and the coherent integral result of the noise channel I... N Calculate the current energy ratio ρ;

[0101] If the current energy ratio ρ is greater than the threshold, it is considered that a good satellite signal can be received at this time, and the loop filter and code loop will feed back normally.

[0102] If the current energy ratio ρ is less than or equal to the threshold, it is assumed that there is no normal satellite signal input at this time, and feedback from the loop filter and code loop is prohibited (that is, the carrier tracking loop and code tracking loop are prohibited from feeding back any results to prevent incorrect adjustments to the switching route under noisy conditions).

[0103] In other words, to cope with high-speed rotation conditions, the current signal energy can be judged during tracking.

[0104] According to one embodiment of the present invention, the current beat signal energy P(n) is calculated by the following formula:

[0105] P(n)=I 2 (n)+Q 2 (n);

[0106] The noise channel power P is calculated using the following formula. N :

[0107]

[0108] The current energy ratio ρ is calculated using the following formula:

[0109]

[0110] Because of the rotating environment, the satellite signal energy received by a single antenna carrier will vary in a sinusoidal pattern. The received satellite signal energy is maximized when the antenna pattern gain is directly opposite the transmitting satellite, and almost zero when the carrier completely blocks the signal. This characteristic can be used to adjust the tracking loop.

[0111] The value of ρ can generally be between 3 and 12, depending on the noise figure and other characteristics of the satellite navigation receiver itself. The impact of the radio frequency front-end and acquisition performance needs to be considered.

[0112] As can be seen from the above embodiments, the single-antenna satellite navigation signal tracking method under high-speed carrier rotation conditions described in this invention provides a technical solution from acquisition to tracking. This solution allows the satellite navigation receiver to still track and lock onto the satellite signal normally under high-speed rotation conditions, without losing lock and thus failing to work properly.

[0113] The features described and / or illustrated above with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, and / or in combination with or in lieu of features in other embodiments.

[0114] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, components, or combinations thereof.

[0115] The apparatus and methods described above can be implemented in hardware or in combination with software. This invention relates to computer-readable programs that, when executed by a logic component, enable that logic component to implement the apparatus or constituent parts described above, or to implement the various methods or steps described above. This invention also relates to storage media for storing the above programs, such as hard disks, magnetic disks, optical disks, DVDs, flash memory, etc.

[0116] Many features and advantages of these embodiments are apparent from this detailed description, and therefore the appended claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the invention are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

[0117] The parts of this invention not described in detail are techniques known to those skilled in the art.

Claims

1. A method for tracking satellite navigation signals with a single antenna under conditions of high-speed carrier rotation, characterized in that, The method includes: Capture navigation signals; The captured navigation signal is tracked using a loop filter and a code loop; Energy determination is performed on the signals locked during the tracking process.

2. The method according to claim 1, characterized in that, Navigation signals are captured using a combination of short-time correlation matched filter and FFT with PMF-FFT.

3. The method according to claim 2, characterized in that, Tracking the captured navigation signal using a loop filter includes: A channel is set for noise floor statistics, and a noise channel coherent integration result I is obtained N ; Computing the frequency error f e and the phase error φ e ; According to the frequency error f e and the phase error φ e calculating loop filter input; According to the loop filter input, the filter output result u is obtained f (s); The filter output result u f (s) is bilinearly transformed to obtain the transformed result u f (z).

4. The method according to claim 3, characterized in that, The frequency discrimination error f is calculated using the following formula. e Phase detection error φ e : cross=I(n-1)Q(n)-Q(n-1)I(n), dot=I(n-1)I(n)+Q(n-1)Q(n), Where cross represents the cross product, dot represents the dot product, and T coh Q represents the coherent integration time. P I represents the instantaneous coherent integral result of the Q branch. P Let I(n) represent the current coherent integration result of branch I, I(n-1) represent the coherent integration result of branch I in the current frame, I(n-1) represent the coherent integration result of branch I in the previous frame, Q(n) represent the current coherent integration result of branch Q, and Q(n-1) represent the coherent integration result of branch Q in the previous frame.

5. The method according to claim 4, characterized in that, The frequency discrimination error f is determined by the following formula. e Phase detection error φ e Calculate the input of the loop filter: Where c1, c2, c3, c4, and c5 are all filter inputs, a2, a3, and b3 are filter parameters, and ω... nf ω is the characteristic frequency of the frequency-locked loop. n This is the characteristic frequency of the phase-locked loop.

6. The method according to claim 5, characterized in that, The filter output result u is obtained from the loop filter input using the following formula. f (s): Where s is the generalized complex frequency of the continuous-time system.

7. The method according to claim 6, characterized in that, The filter output result u is expressed by the following formula. f (s) Perform a bilinear transformation to obtain the transformed result u. f (z): Where z is the generalized complex frequency of the discrete-time system.

8. The method according to claim 7, characterized in that, Tracking the captured navigation signals using a code loop is achieved through the following formula: Where, δ cp (n) represents the current phase detection error of the timing code. This is the output result of the code ring in the previous cycle, where α is the code ring loop parameter.

9. The method according to claim 8, characterized in that, Energy determination of the signal locked during tracking includes: Calculate the current beat signal energy P(n); Based on the noise channel coherence integral result I N Calculate the noise channel power P N ; Based on the current image signal energy P(n) and the coherent integral result of the noise channel I... N Calculate the current energy ratio ρ; If the current energy ratio ρ is greater than the threshold, the loop filter and code loop will provide feedback normally. If the current energy ratio ρ is less than or equal to the threshold, feedback from the loop filter and code loop is disabled.

10. The method according to claim 9, characterized in that, The current beat signal energy P(n) is calculated using the following formula: P(n)=I 2 (n)+Q 2 (n); The noise channel power P is calculated using the following formula. N : The current energy ratio ρ is calculated using the following formula:

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