A multi-channel time-division multiplexing method for tracking modules of satellite navigation receivers

Abstract

The present invention discloses a multi-channel time-sharing multiplexing method for a tracking module of a satellite navigation receiver, comprising: S1: acquiring intermediate frequency sampling data of a satellite navigation receiver; S2: pre-processing the intermediate frequency sampling data to obtain intermediate frequency data, and performing "ping-pong" loop data caching; S3: utilizing a state machine to perform tracking processing on different tracking channels of a satellite navigation receiver tracking module on the cached intermediate frequency data, thereby achieving time-sharing multiplexing. The present invention significantly increases the number of tracking channels and optimizes the use of computing units without affecting the synchronization between tracking channels. At the same time, both low cost and high performance are achieved. The present invention time-sharing multiplexes logical resources, and can achieve signal tracking effects for multiple tracking channels with the computing resources of one channel, the storage resources of multiple channels, and two state machines. The number of resources used is far less than that of a method in which all channels are directly and independently implemented.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite navigation and relates to a multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver. Background Art

[0002] In the field of satellite navigation, the number of satellite systems, satellites, and satellite frequencies are increasing day by day. Therefore, for full-frequency receivers, the number of tracking channels must be increased to meet the requirements of stable tracking and signal screening as the number of signals increases.

[0003] When implementing the tracking function of the tracking channel in the existing design, too many resources are used, and the total number of tracking channels has not increased significantly, making it difficult to achieve low-cost multi-channel full-star and full-frequency satellite signal tracking. Summary of the Invention

[0004] In view of the problems existing in the prior art, the object of the present invention is to provide a multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver, which at least partially solves the above technical problems.

[0005] An embodiment of the present invention provides a multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver, comprising:

[0006] S1: Obtain intermediate frequency sampling data from the satellite navigation receiver;

[0007] S2: Preprocessing the intermediate frequency sampling data to obtain intermediate frequency data, and performing a "ping-pong" loop data buffering;

[0008] S3: Using the state machine to perform tracking processing on different tracking channels of the satellite navigation receiver tracking module on the buffered intermediate frequency data to achieve time-division multiplexing.

[0009] Furthermore, the intermediate frequency sampling data is data pre-processed by a front end of a satellite navigation receiver.

[0010] Furthermore, the preprocessing is to sequentially perform down-conversion, low-pass filtering, integral down-sampling and 3-bit quantization on the intermediate frequency sampling data.

[0011] Furthermore, the "ping-pong" loop data cache is implemented by two BRAM blocks.

[0012] Furthermore, the S3 includes:

[0013] S31: The state machine is idle and waits for the current BRAM storage to complete;

[0014] S32: The state machine controls the reading of the current BRAM channel parameter storage table. Different channels have different addresses for storing and reading parameters.

[0015] S33: The state machine controls the reading of the current BRAM intermediate frequency signal for baseband demodulation calculation;

[0016] S34: the state machine controls the current BRAM channel to write into the parameter storage table, and saves a state in which BRAM data processing is completed;

[0017] S35: When the current BRAM channel is not full, the state machine chooses to repeat S32 to enter the next channel processing of the current BRAM; when the current BRAM channel is full, another BRAM is used as the current BRAM and returns to the idle state S31.

[0018] Furthermore, the frequency of the intermediate frequency sampling data is 66 MHz or 62 MHz.

[0019] Furthermore, the frequency of the intermediate frequency data does not exceed 25 MHz.

[0020] An embodiment of the present invention provides a multi-channel time-sharing multiplexing method for a satellite navigation receiver's tracking module. Compared with the prior art, this method significantly increases the number of tracking channels and optimizes the use of computing units without affecting the synchronization between tracking channels. It also achieves both low cost and high performance. The present invention time-sharing multiplexes logical resources, achieving signal tracking across multiple tracking channels with the computing resources of one channel, the storage resources of multiple channels, and two state machines. This method uses far fewer resources than a method that directly and independently implements all channels.

[0021] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 An overall logic diagram provided for an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of a portion of intermediate frequency storage and playback provided by an embodiment of the present invention.

[0024] Figure 3 This is another schematic diagram of the intermediate frequency storage and playback provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0027] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "internalized," and "connected" should be understood in a broad sense. For example, "connected" can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium; and it can refer to internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention in specific circumstances.

[0028] The embodiment of the present invention provides a multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver, such as Figure 1 Shown, including:

[0029] S1: Obtain intermediate frequency sampling data from the satellite navigation receiver;

[0030] S2: Preprocess the intermediate frequency sampling data to obtain intermediate frequency data and perform "ping-pong" loop data caching;

[0031] S3: Use the state machine to perform tracking processing on different tracking channels of the satellite navigation receiver tracking module on the cached intermediate frequency data to achieve time-division multiplexing.

[0032] The present invention significantly increases the number of tracking channels without affecting the synchronization between the tracking channels, optimizes the use of computing units, and achieves both low cost and high performance.

[0033] The present invention time-division multiplexes logic resources, achieving signal tracking effects for multiple tracking channels with the computing resources of one channel, the storage resources of multiple channels, and two state machines, using far fewer resources than a method that directly implements all channels independently.

[0034] The present invention pre-processes the collected satellite intermediate frequency signals (which have already been mixed, filtered, and sampled at the receiver front end) to a unified intermediate frequency across multiple channels. Mixing, filtering, and downsampling are performed during pre-processing. The pre-processed signals are cached in a "ping-pong" loop, and then the data is repeatedly read out to perform tracking processing on different tracking channels based on the state machine's call control. The specific steps are as follows:

[0035] Step 1: Preprocess the 66MHz-sampled satellite IF signal to a 22MHz-sampled IF signal. The IF sampling data can use sampling information from other frequencies, with 66MHz and 62MHz being the most common frequencies used in the market. A 100MHz processing clock is used to time-multiplex one tracking channel into four channels, so the sampling frequency cannot exceed 25MHz.

[0036] First, the 66MHz sampled satellite intermediate frequency signal is mixed with the locally generated kcos(2πωt) and ksin(2πωt) signals to generate I / Q branch signals. Then, the I / Q signals are low-pass filtered to remove high-frequency components. Then, downsampling is performed to convert the original 66MHz sampling signal into a 22MHz sampling signal through integration and accumulation. Finally, the signal is quantized into a 3-bit wide signal with no DC component through a signal quantization algorithm.

[0037] Step 2: Use two 8x1024 BRAM blocks and registers to cache the 22MHz pre-processed signal, TIC, and start time. Each BRAM block contains two channels. The present invention uses the above two BRAM blocks to achieve 4-channel multiplexing.

[0038] Two BRAM blocks are used to implement a ping-pong storage function. For example, when BRAM0 is storing data, BRAM1 data is read for tracking processing, and when BRAM1 is storing data, BRAM0 data is read for tracking processing. This design ensures that while one BRAM is storing data, the other BRAM data is read for tracking processing in advance, ensuring that no data is lost.

[0039] The data format is 8 bits, consisting of 6 bits of I / Q branch data, 1 bit of carrier TIC, and 1 bit of pseudo-code TIC. The TIC signal is generated by counting the sampling clock cycles and is used to periodically extract the carrier observation and pseudo-code observation of the tracking channel.

[0040] When starting to store BRAM data, the time point is recorded, and the accumulated count is used to record the exact time point when waiting for playback.

[0041] Step 3: Under a processing clock of 100 MHz, use the state machine to implement the 4-channel time-division multiplexing function.

[0042] The specific implementation steps are as follows:

[0043] Step 31: The state machine is idle and waits for the first BRAM storage to complete;

[0044] Step 32: The state machine controls the channel parameter table BRAM to read, and different channel parameters are stored and read at different addresses;

[0045] Step 33: The state machine controls the intermediate frequency signal BRAM to read for baseband demodulation calculation;

[0046] Step 34: The state machine controls the channel parameter table BRAM to write and save a BRAM data processing completion status;

[0047] Step 35: When the current BRAM channel is not full, the state machine chooses to repeat S32 to enter the next channel processing of the current BRAM; when the current BRAM channel is full, another BRAM is used as the current BRAM and returns to the idle state S31.

[0048] A lot of hardware resources are saved by time-sharing computing units.

[0049] Step 4: Due to data caching and time-multiplexed tracking channel processing delays, the observation data must be read and used after a fixed delay. This delay must exceed the overall multiplexing time, that is, the storage time of a BRAM.

[0050] The following is a description of some of the technical principles used in the invention.

[0051] Downconversion. The RF 66MHz sampling data (but other sampling frequencies are possible) is input for IF preprocessing. First, the IF frequency is downconverted to near zero frequency by mixing with a local fixed-frequency digital carrier signal, simultaneously becoming the I and Q branch signals. For example, the Beidou B1I signal sampling input is 15.902MHz (determined by the hardware design), and the local digital carrier 15.46875MHz is mixed to obtain a 433.25kHz signal and a high-frequency component. The specific principles are as follows:

[0052] I=IF*COS

[0053] Q=IF*SIN

[0054] Where IF is the input intermediate frequency signal, COS / SIN is the sine and cosine carrier signal reproduced locally based on the carrier, and a new I / Q branch signal I / Q is generated.

[0055] Low-pass filtering: A set of low-pass filter parameters is calculated based on the satellite signal bandwidth to perform low-pass filtering on the mixed signal, removing high-frequency components and out-of-band noise. For example, the Beidou B1I signal bandwidth is 2.046MHz, so the low-pass filter parameters with a 66MHz sampling frequency and a 3MHz cutoff frequency are used to ensure signal integrity.

[0056] Downsampling. The filtered data is then subjected to an integral downsampling process to ensure time-division multiplexing of the tracking channels. Integral downsampling involves accumulating data for a specified length and then outputting it. For example, the figure shows three accumulations and one output, downsampling the 66MHz sampled data to 22MHz. This operation also filters out 11MHz out-of-band noise and high-frequency components at the intermediate frequency.

[0057] 3-bit quantization. The downsampled signal is quantized to 3 bits to reduce the computational complexity of subsequent processing. This design uses bidirectional adaptive logic to quantize the high-bitwidth signal value after filtering and integration to 3 bits while maintaining satellite signal integrity. For example, a 5-bit signed intermediate frequency input is mixed with a local 6-bit digital carrier to become a 10-bit signed number. This is then combined with the 8-bit signed filter parameters to become a 17-bit signed number. Three integrations are performed to obtain a 19-bit signed number, and finally adaptively quantized to a 3-bit signed number. This significantly reduces the resources required for subsequent computation.

[0058] Ping-Pong Buffer. Three bits of preprocessed I / Q IF data are combined with a two-bit delayed TIC period extraction signal and stored in a ping-pong buffer loop. When one BRAM block is full, the other is opened. The IF data and TIC signal are then repeatedly read out to achieve multi-channel tracking using time-division multiplexing of tracking channels.

[0059] IF mixing. The tracking channel performs complex mixing calculations on the readout 3-bit I / Q signal and the locally reproduced carrier signal to remove the remaining carrier component and Doppler frequency value in the signal. The specific principles are as follows:

[0060] I`=I*COS–Q*SIN

[0061] Q`=-I*SIN–Q*COS

[0062] Where I / Q is the 3-bit value of the I / Q component of the intermediate frequency signal, COS / SIN is the local sine and cosine carrier signal reproduced based on the carrier and Doppler, and the new I / Q branch signal I` / Q` is generated.

[0063] Pseudo-code correlation. The mixed signal is multiplied by a locally reproduced pseudo-code of a specified frequency and phase to achieve code correlation. This despreads the satellite spread spectrum modulated signal, leaving only the modulated digital signal within the satellite signal. For example, the Beidou B1I signal has a pseudo-code half-chip frequency of 2.046MHz*2=4.092MHz. The pseudo-code Doppler value is calculated by converting the carrier Doppler value based on the carrier frequency and the pseudo-code frequency.

[0064] Integration calculation. The signal after code correlation is integrated and accumulated within the specified pseudo code period, and the accumulated value is finally output as the I / Q branch energy component of the signal. For example, the Beidou B1I signal has a pseudo code period of

[0065] T=4092 / (4092000+CDPL)

[0066] Where 4092 is the half-chip length of the B1I signal period, 4092000 is the half-chip rate value of the B1I signal, and CDPL is the half-chip Doppler frequency value of the B1I signal pseudo code.

[0067] Data caching. First, the IF data and TIC delay are combined into 8-bit data and written into the corresponding data cache BRAM block under the IF valid and ping-pong loop switching logic. At the same time, the IF clock count value corresponding to the IF valid is also cached, representing the starting time point of the cached data on the IF clock timeline.

[0068] like Figure 2 and Figure 3 As shown, the intermediate frequency data playback logic of the tracking channel time-division multiplexing.

[0069] 1. Start the playback logic after confirming that the current tracking channel state machine is idle and there is a BRAM block with complete data storage in the ping-pong loop.

[0070] 2. Read the parameter value of the specified channel from the multi-channel tracking parameter storage BRAM block and put it into the channel for tracking calculation.

[0071] 3. After the parameter reading is completed, start reading 8-bit data from the BRAM block stored in the intermediate frequency, parse the data into I / Q branch signals and TIC delay signals, and read out the stored intermediate frequency clock count value at the same time. Several signals are input into the tracking channel at the same time. Figure 1 IF mixing, pseudo-code correlation, and integral calculation operations.

[0072] 4. After the intermediate frequency data BRAM block is processed (ie, read out is completed), the key parameters of the current tracking channel are written into the designated tracking channel parameter storage BRAM block.

[0073] 5. Start processing the next tracking channel and perform the same steps 2, 3, and 4 above again, except that the parameters are changed to another channel parameter. Until all channels are processed, the tracking channel state machine enters the idle state again and waits for the next intermediate frequency data cache BRAM block to be full. If the conditions of step 1 are met, it will enter step 2 again.

[0074] like Figure 1 As shown, the present invention requires preprocessing the IF data and mixing the 66MHz IF data, that is, removing a certain amount of the certification frequency from the IF signal; then low-pass filtering the mixed signal to remove the high-frequency components generated by the mixing, leaving only the frequency difference signal component; then integrating and accumulating the filtered signal to reduce the signal sampling rate from 66MHz to 22MHz; finally, quantizing the 22MHz IF signal with 3 bits, preserving signal integrity to the greatest extent while simplifying data calculations. The final preprocessed output is a 22MHz IF signal.

[0075] like Figure 2 and Figure 3 As shown, the present invention caches preprocessed IF data and TIC signals in a tracking channel using two BRAM blocks in a ping-pong loop. The stored starting time point is also cached. The IF data playback control state machine first reads all tracking channel parameters from the storage BRAM according to the different addresses of different tracking channels. It then begins playback of the IF data and TIC, and starts time counting accumulation for IF processing. Once the IF data playback calculation for that channel is complete, all channel parameters are written to the BRAM at the corresponding tracking channel address. By caching data, TIC, and time, the computational unit achieves the effect of time-division multiplexing of tracking channels.

[0076] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, and these changes should be covered by the scope of protection of the present invention.

Claims

1. A multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver, characterized in that: include: S1: Obtain intermediate frequency sampling data from the satellite navigation receiver; The intermediate frequency sampling data is data pre-processed by the front end of the satellite navigation receiver; S2: Preprocessing the intermediate frequency sampling data to obtain intermediate frequency data, and performing "ping-pong" loop data caching; the data format of the intermediate frequency data is 8-bit data, including 6-bit I / Q branch data, 1-bit carrier TIC, and 1-bit pseudo code TIC; the "ping-pong" loop data caching is implemented by two BRAM blocks, each BRAM block contains two channels, which are used to implement time-division multiplexing of one tracking channel into four channels; the preprocessing is to sequentially perform down-conversion, low-pass filtering, integral downsampling, and 3-bit quantization on the intermediate frequency sampling data; S3: Using a state machine to perform tracking processing on different tracking channels of a satellite navigation receiver tracking module on the buffered intermediate frequency data to achieve time-division multiplexing; The tracking processing of the different tracking channels includes: ping-pong buffering, intermediate frequency mixing, pseudo-code correlation and integral calculation; Said S3 comprises: S31: The state machine is idle and waits for the current BRAM storage to complete; S32: The state machine controls the reading of the current BRAM channel parameter storage table. Different channels have different addresses for storing and reading parameters. S33: The state machine controls the reading of the current BRAM intermediate frequency signal for baseband demodulation calculation; S34: the state machine controls the current BRAM channel to write into the parameter storage table, and saves a state in which BRAM data processing is completed; S35: When the current BRAM channel is not full, the state machine chooses to repeat S32 to enter the next channel processing of the current BRAM; when the current BRAM channel is full, another BRAM is used as the current BRAM and returns to the idle state S31.

2. The multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver according to claim 1, characterized in that: The frequency of the intermediate frequency sampling data is 66 MHz or 62 MHz.

3. The multi-channel time-division multiplexing method for a tracking module of a satellite navigation receiver according to claim 1, characterized in that: The frequency of the intermediate frequency data does not exceed 25 MHz.

Images