CN118311613A - Multi-radio frequency channel on-line quick correction method and system of GNSS array antenna - Google Patents
Multi-radio frequency channel on-line quick correction method and system of GNSS array antenna Download PDFInfo
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Abstract
The invention relates to a multi-radio frequency channel online quick correction system of a GNSS array antenna, belongs to the technical field of circuits and signal processing, and solves the problems that a radio frequency channel consistency correction method in the prior art is complex in algorithm, high in hardware cost, difficult in hardware delay time measurement and the like. And a signal generating module generates a coherent correction signal to a radio frequency distribution network, a plurality of paths of radio frequency channels are input, the radio frequency signals are processed to a signal and information processing module, and after the radio frequency signals are processed, the correction of the plurality of paths of radio frequency channels and the test of the system delay time are realized, so that the influence of the inconsistency of the plurality of paths of radio frequency channels on external signals is eliminated. The method simplifies the hardware structure, reduces the hardware cost, has the function of completing the detection of the on-line hardware and the rapid correction of the channel at any time, has the characteristics of stable power and flexible and editable frequency, and can measure the hardware absolute time delay of each path of radio frequency channel to the signals of different frequency points at one time.
Description
Technical Field
The invention relates to the technical field of circuits and signal processing, in particular to a method and a system for on-line rapid correction of multiple radio frequency channels of a GNSS array antenna.
Background
The satellite navigation system is an important space infrastructure, can provide high-precision positioning, speed measurement and time service, and can bring great social and economic benefits. Although different satellite navigation systems have great differences in operating frequency bands, constellation distribution, system configuration, etc. However, a common problem with satellite navigation systems is that the receiver at the satellite navigation client is very susceptible to interference and influence from external factors. The light weight affects the positioning accuracy, and the heavy weight disables the positioning capability of the receiver. In some special occasions, high positioning accuracy is ensured while anti-interference is required. If the airport needs to ensure that the aircraft can take off and land smoothly, the position of the aircraft can be accurately judged, and the like. Therefore, how to solve the anti-interference problem by using the space-time domain combined filtering algorithm and ensure the high-precision positioning effect is a popular research direction at present.
The key points affecting the anti-interference capability and high-precision positioning are mainly the following aspects: antenna array, radio frequency front end and corresponding anti-interference algorithm. The radio frequency front end is used as a link for connecting free space and intermediate frequency signal processing in the wireless communication technology, and the performance of the radio frequency front end is crucial to the whole communication system. The space-time filtering algorithm realizes high-precision positioning under the anti-interference condition and highly depends on the consistency of the radio frequency channel. When the amplitude of the channel is in error, the peak value of the signal is reduced, and when the phase error is generated in the channel, the position of the peak value of the signal is shifted. Channel mismatch due to differences between electronic components is unavoidable, so real-time correction of the radio frequency channel is important. For high-precision positioning and time service functions, delay of a receiver on signals is one of important points to be considered, and in a positioning algorithm, the positioning precision is affected by the existence of uncertain delay. Thus, it is also necessary to determine the delay of the signal by the radio frequency channel. However, in the prior art, in the application of high-precision positioning timing in some anti-interference scenes, after the anti-interference receiver is installed at a fixed position, the anti-interference receiver cannot be corrected and debugged at will, and the external source is inaccurate in calibration, and a common method for moving signals to radio frequency points through a mixer by using a traditional dds signal generator or DAC output signal is complex in algorithm, high in hardware cost, incapable of measuring hardware delay time, or complex in corresponding measuring method.
In summary, the existing radio frequency channel consistency correction method has the problems of complex algorithm, high hardware cost and difficulty in measuring hardware delay time.
Disclosure of Invention
In view of the above analysis, the embodiments of the present invention aim to provide a method and a system for online and rapid calibration of multiple radio frequency channels of a GNSS array antenna, which are used for solving the problems of complex algorithm, high hardware cost and difficulty in measuring hardware delay time in the existing radio frequency channel consistency calibration method.
The aim of the invention is mainly realized by the following technical scheme:
In one aspect, an embodiment of the present invention provides an online rapid calibration system for multiple radio frequency channels of a GNSS array antenna, including a signal generating module, a radio frequency distribution network, multiple radio frequency channels, and a signal and information processing module; wherein,
The signal generation module is used for generating a coherent correction signal to the radio frequency distribution network;
The radio frequency distribution network is used for transmitting the coherent correction signal to the multipath radio frequency channels in a self-checking stage or transmitting an external signal received through an antenna to the multipath radio frequency channels in an actual use stage;
The multipath radio frequency channel is used for processing the coherent correction signal in a self-checking stage to obtain a first radio frequency signal and transmitting the first radio frequency signal to the signal and information processing module; the system is also used for processing the external signal in the actual use stage to obtain a second radio frequency signal and transmitting the second radio frequency signal to the signal and information processing module;
the signal and information processing module is used for processing the first radio frequency signal in a self-checking stage to realize the correction of a plurality of radio frequency channels and the test of system delay time; and the second radio frequency signal is processed in the actual use stage, so that the influence of the inconsistency of the multipath radio frequency channels on the external signal is eliminated.
Based on a further improvement of the method, the signal and information processing module is further used for enabling the signal generating module in the self-checking stage, sending control information to the signal generating module, and generating a coherent correction signal by the control signal generating module.
Based on the further improvement of the method, the signal generating module comprises a PLL and a power divider, wherein the PLL is in common source with the clocks of the multiple radio frequency channels and is used for generating corresponding coherent correction signals and inputting the signals into the multiple radio frequency channels; wherein, by rewriting the control word of the PLL, any path of radio frequency channel generates a required single frequency signal; and when the single-frequency signals in the radio frequency channels have the same frequency and the phase difference is fixed, obtaining the coherent correction signals in the multiple radio frequency channels.
Based on further improvement of the method, the multi-radio frequency channel online quick correction system of the GNSS array antenna further comprises a crystal oscillator, wherein the crystal oscillator is used for generating a mixing clock to the multi-channel radio frequency channel, the multi-channel radio frequency channel processes the coherent correction signal based on the mixing clock to obtain a first radio frequency signal, and processes an external signal based on the mixing clock to obtain a second radio frequency signal; the crystal oscillator is also used for generating a sampling clock to the signal and information processing module, the signal and information processing module processes the first radio frequency signal based on the sampling clock to realize correction of multiple paths of radio frequency channels and test of system delay time, processes the second radio frequency signal based on the sampling clock, and eliminates the influence of inconsistent multiple paths of radio frequency channels on the external signal.
Based on the further improvement of the method, a plurality of radio frequency signal wires with equal length wiring are further arranged between the signal generating module and the radio frequency distribution network and used for transmitting the coherence correction signal to the radio frequency distribution network.
Based on the further improvement of the method, the radio frequency distribution network comprises a plurality of mutually independent radio frequency switches which are in one-to-one correspondence with each path of radio frequency channel and are used for enabling the system to enter a self-checking stage or an actual use stage through switching; when the system is switched to be communicated with the signal generation module, the system enters a self-checking stage, so that the coherent correction signal can be transmitted to a corresponding radio frequency channel; when the system is switched to be communicated with the external antenna, the system enters an actual use stage, so that external signals can be transmitted to the corresponding radio frequency channel.
Based on the further improvement of the method, each path of the multipath radio frequency channels sequentially comprises the same radio frequency filter, a low noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier and a variable gain intermediate frequency amplifier; wherein,
The radio frequency filter is used for filtering out-of-band interference signals; the low-noise amplifier is used for amplifying and filtering signals obtained after out-of-band interference signals to obtain first radio frequency signals or second radio frequency signals; the mixer is used for down-converting the first or second radio frequency signals to an intermediate frequency to obtain intermediate frequency signals; the intermediate frequency filter is used for filtering interference signals in the intermediate frequency signals; the intermediate frequency amplifier is used for amplifying the intermediate frequency signal after filtering the interference signal based on the OIP3 index of the whole link; the variable gain amplifier is used for finely adjusting the multipath channels so that the amplitude-frequency characteristics among the multipath channels of the system are consistent.
On the other hand, the embodiment of the invention provides a multi-radio frequency channel on-line quick correction method of a GNSS array antenna, which comprises the following steps:
In the correction stage, starting a multi-radio frequency channel on-line rapid correction system of the GNSS array antenna, and measuring to obtain delay time of the system;
Carrying out consistency correction on a plurality of paths of radio frequency channels to obtain a plurality of digital filter coefficients corresponding to the paths of radio frequency channels one by one;
in the actual use stage, external satellite navigation signals are processed based on the digital filter coefficients, and the influence of inconsistent multipath radio frequency channels on the external satellite navigation signals is eliminated.
Based on the further improvement of the method, the on-line rapid correction system of the multiple radio frequency channels of the GNSS array antenna is started, and the delay time of the system is measured and obtained, comprising the following steps:
measuring hardware delay: the signal and information processing module controls the radio frequency distribution network to switch each radio frequency switch to a corresponding link of the signal generating module, enables the signal generating module, and sends control information to the signal generating module, wherein the control information is the starting point of timing time;
When the signal and information processing module receives the coherent correction signal, the signal and information processing module is the end point of the timing time, and the time difference is recorded as t Total (S) ; the time counted is:
t Total (S) ＝t1+t2+t3+t4
Wherein t 1 is the time elapsed for the signal and information processing module to enable the signal generation module and send control information to the signal generation module; t 2 is the time that the signal generation module takes from receiving the control information to sending out the coherence correction signal; t 3 is the time that the coherent correction signal takes to reach the radio frequency distribution network from the transmission of the multi-channel radio frequency signal line; t 4 is the time that the radio frequency distribution network sends out a coherent correction signal or an external signal, generates a radio frequency signal through a plurality of radio frequency channels and then reaches the signal and the information processing module; the actual delay time caused by the radio frequency channel is:
tdelay＝t Total (S) -t2+Δt
the absolute time delay of each channel is obtained, so that delay errors brought by a hardware system during high-precision time-giving are compensated.
Based on further improvement of the method, consistency correction is carried out on the multi-path radio frequency channel to obtain a plurality of digital filter coefficients corresponding to the multi-path radio frequency channel one by one, and the method comprises the following steps:
correcting the consistency of the multipath radio frequency channels, and enabling the amplitude-frequency response and the phase-frequency response of the coherent correction signals of different radio frequency channels to be consistent by adjusting the digital filter coefficients;
according to the nature of convolution, there are respectively in the time domain and the frequency domain:
Y(ω)＝X(ω)·H(ω)
Wherein x (n) is an original time domain signal obtained after the adc samples the radio frequency signal, h (n) is a digital filter coefficient, and y (n) is a corrected time domain signal; x (omega) is an original frequency domain signal obtained after the adc samples the radio frequency signal, and H (omega) is Fourier transform corresponding to the digital filter coefficient;
For a time domain nth order coefficient H (N) of the digital filter, the corresponding fourier transformed frequency domain is expressed as H (ω) having N corresponding frequency bins;
The sampling rate is Fs, the frequency corresponding to the Mth point is The signal generating module needs to generate the frequencies of the N corresponding frequency points;
After the coherent correction signals are stabilized, sampling the coherent correction signals through an ADC (analog to digital converter) at N points, and recording the data of each channel as d1 (N), d2 (N) and d3 (N) respectively;
and performing FFT conversion on the obtained data of each channel to obtain D1 (N), D2 (N) and D3 (N).
Dividing the ideal reference channel H ref by the corresponding frequency point of the channel to be balanced to obtain H i＝Href/Di (N);
Repeating the calculation for a plurality of times, and taking an average value;
changing the frequency point of the signal, repeating the steps until all the tests of the frequencies of the N corresponding frequency points are completed, and obtaining:
H＝{H1,H2......HN}
Performing inverse Fourier transform on the H to obtain hi, thereby obtaining a digital filter coefficient of the channel; and then, different signals passing through different radio frequency channels enter corresponding digital filters to be processed, and hi is calculated for each channel of radio frequency channel to obtain the digital filter coefficient of each channel.
Compared with the prior art, the invention has at least one of the following beneficial effects:
1. According to the embodiment of the invention, the on-board signal generation module is arranged, and the method of moving the signal to the radio frequency point by the traditional dds signal generator or DAC output signal through the mixer is simplified into the method of generating the required coherent frequency signal by using only one phase-locked loop, so that the hardware structure on the circuit board is simplified, and the hardware cost is reduced. The system has the functions of completing detection of on-line hardware and rapid channel correction at any time, and the coherent correction signal has the characteristics of stable power and flexible frequency.
2. The on-line rapid correction method for the multiple radio frequency channels of the GNSS array antenna provided by the embodiment of the invention not only can support the simultaneous completion of correction of the information such as the relative time delay, frequency, amplitude, phase and the like of the multiple radio frequency channels, but also can measure the hardware absolute time delay of each channel of radio frequency channel to signals of different frequency points at one time, thereby being capable of compensating the problems such as differential code deviation, differential phase deviation and the like caused by the hardware delay and meeting the high-precision timing and positioning application of the array antenna under the interference condition.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a schematic diagram of an online rapid calibration system for multiple RF channels of a GNSS array antenna according to an embodiment of the present invention;
FIG. 2 is a flowchart of an on-line fast calibration algorithm for multiple RF channels of a GNSS array antenna according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a hardware delay calculation method according to an embodiment of the present invention;
fig. 4 is a flowchart of calculating a hardware delay time according to an embodiment of the present invention.
Detailed Description
The following detailed description of preferred embodiments of the application is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the application, are used to explain the principles of the application and are not intended to limit the scope of the application.
Example 1
In one embodiment of the present invention, a system for online and rapid calibration of multiple rf channels of a GNSS array antenna is disclosed, as shown in fig. 1, including a signal generating module, an rf distribution network, multiple rf channels, a signal and information processing module, a crystal oscillator, and multiple rf signal lines; wherein,
The signal generation module is used for generating a coherent correction signal to the radio frequency distribution network.
The radio frequency distribution network is used for transmitting the coherent correction signal to the multi-path radio frequency channel in the self-checking stage or transmitting the external signal received through the antenna to the multi-path radio frequency channel in the actual use stage.
The multi-channel radio frequency channel is used for processing the coherent correction signal in the self-checking stage to obtain a first radio frequency signal and transmitting the first radio frequency signal to the signal and information processing module; and the antenna is also used for processing the external signal received through the antenna in the actual use stage to obtain a second radio frequency signal and transmitting the second radio frequency signal to the signal and information processing module.
The signal and information processing module is used for enabling the signal generating module in the self-checking stage, sending control information to the signal generating module and controlling the signal generating module to generate a coherent correction signal; the system is also used for processing the first radio frequency signal generated by the coherent correction signal to realize the correction of the multipath radio frequency channel and the test of the system delay time; and the system is also used for processing a second radio frequency signal generated by an external signal, such as an external satellite navigation signal, at the actual use stage after the correction of the multipath radio frequency channels and the test of the system delay time are completed, so as to eliminate the influence of the inconsistency of the multipath radio frequency channels on the external signal.
The crystal oscillator is used for generating a mixing clock to a plurality of radio frequency channels, the plurality of radio frequency channels process the coherent correction signals based on the mixing clock to obtain a first radio frequency signal, and process the external signals based on the mixing clock to obtain a second radio frequency signal; the crystal oscillator is also used for generating a sampling clock to the signal and information processing module, the signal and information processing module processes the first radio frequency signal based on the sampling clock to realize the correction of the multipath radio frequency channels and the test of the system delay time, processes the second radio frequency signal based on the sampling clock, and eliminates the influence of the inconsistency of the multipath radio frequency channels on external signals.
And the multipath radio frequency signal lines are used for transmitting the coherent correction signals to the radio frequency distribution network.
Specifically, the signal generating module is configured to generate a coherent correction signal to the radio frequency distribution network, where the signal generating module includes a PLL (phase locked loop ) and a power divider, where the PLL is configured to be co-source with a clock of multiple radio frequency channels, and configured to generate a corresponding coherent correction signal and input the corresponding coherent correction signal to the multiple radio frequency channels; wherein, by rewriting the control word of the PLL, any path of radio frequency channel generates a required single frequency signal; and when the single-frequency signals in the radio frequency channels have the same frequency and the phase difference is fixed, obtaining the coherent correction signals in the multiple radio frequency channels.
The radio frequency distribution network comprises a plurality of mutually independent radio frequency switches which are in one-to-one correspondence with the multipath radio frequency channels and are used for switching the radio frequency switches so that the system enters a self-checking stage or an actual use stage.
Specifically, when the system is switched to be communicated with the signal generation module, the system enters a self-checking stage, so that a coherent correction signal can be transmitted to a corresponding radio frequency channel, and the functions of consistency correction, fault detection, system time delay detection and the like of a plurality of channels of radio frequency channels are completed by utilizing the signal and information processing module; when the system is switched to be communicated with an external antenna, the system enters an application stage, so that the system can receive external satellite navigation signals and can transmit the signals to corresponding radio frequency channels, and high-precision navigation positioning time service is realized by utilizing the signals and the information processing module; the fault detection means that a signal is generated through a signal generation module, whether the signal can be received at a receiving end or not is judged, and normal receiving is considered to be fault-free. Failure is considered to be present if no signal is received.
The multipath radio frequency channel is a main signal receiving link, and each path of the multipath radio frequency channel sequentially comprises the same radio frequency filter, a low noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier and a variable gain intermediate frequency amplifier. The main function is to transfer the coherent correction signal or the external satellite navigation signal to an ADC (Analog-to-Digital Converter) in the signal and information processing module. Wherein,
The radio frequency filter is used for filtering out-of-band interference signals; the low-noise amplifier is used for amplifying and filtering signals obtained after out-of-band interference signals to obtain first radio frequency signals or second radio frequency signals; the mixer is used for down-converting the first or second radio frequency signals to an intermediate frequency to obtain intermediate frequency signals; the intermediate frequency filter is used for filtering interference signals in the intermediate frequency signals; the intermediate frequency amplifier is used for amplifying the intermediate frequency signal after filtering the interference signal based on the OIP3 index of the whole link; the variable gain amplifier is used for finely adjusting the multipath channels so that the amplitude-frequency characteristics among the multipath channels of the system are consistent. Illustratively, the signal amplitude adjustment circuit is used for primarily adjusting the signal amplitude so as to meet the power requirement of the ADC input signal.
The signal and information processing module is used for enabling the signal generating module in the self-checking stage and sending control information to the signal generating module; the system is also used for processing radio frequency signals generated by the coherent correction signals or radio frequency signals generated by external satellite navigation signals, so that the functions of amplitude frequency/phase frequency correction, fault detection, beam forming anti-interference and the like of the multipath radio frequency channels are realized; the Beamforming (Beamforming) is also called Beamforming and spatial filtering, and functions to combine signals, suppress interference signals in non-target directions, and enhance sound signals in target directions. The principle is to adjust the basic unit parameters of the phased array so that signals at certain angles get constructive interference and signals at other angles get destructive interference. The signals output by the array elements are weighted, summed and filtered, and finally signals in the expected direction are output, which is equivalent to forming a beam.
Multiple radio frequency signal lines require equal length wiring.
Compared with the scheme of adopting DDS or DAC to generate intermediate frequency signals and then converting the intermediate frequency signals into radio frequency signals in the prior art, the embodiment of the invention only adopts one phase-locked loop circuit to directly generate radio frequency signals, namely the coherent correction signals, thereby simplifying the hardware structure on a circuit board, reducing the hardware cost, having the functions of completing the detection of on-line hardware and the rapid correction of channels at any time, and simultaneously having the characteristics of stable power and flexible and editable frequency.
Example 2
The invention discloses a method for rapidly correcting multiple radio frequency channels of a GNSS array antenna on line, which comprises the following steps:
When the system is started, the signal and information processing module configures and enables the signal generating module to generate a coherent correction signal, a radio frequency signal is generated after passing through a radio frequency distribution network and a plurality of radio frequency channels, the signal enters the ADC to complete input conversion, then the signal and information processing module is utilized to conduct multichannel parallel data processing, after the amplitude statistics processing of data of each channel is completed, the adjustment value of the channel variable gain intermediate frequency amplifier is calculated to realize rough adjustment of the signal amplitude, and the signal amplitude entering the ADC is ensured to meet the power requirement of the input signal of the ADC.
And then, the detection and calibration of the absolute hardware time delay and amplitude value under the corresponding frequency of each radio frequency channel are completed according to the coherent correction signal, related values are transmitted to the signal and information processing module, and the time delay is compensated in the signal processing of the subsequent application stage.
When the time delay calculation is carried out, the amplitude frequency/phase frequency response of the system can be estimated by utilizing a system identification method based on the input/output information of the radio frequency channels, namely the coherent correction signal/radio frequency signal, then the tap coefficient of the digital filter is calculated by the corrected system response, and the automatic calibration of the amplitude frequency/phase frequency of each channel is realized through a filtering algorithm, so that the amplitude frequency characteristic and the phase frequency characteristic of each radio frequency channel tend to be consistent. Thereby completing the correction of the consistency of the multipath radio frequency channels and transmitting the absolute amplitude frequency/phase frequency value of the reference channel to the signal and information processing module; wherein the digital filter is implemented in the signal and information processing module.
Under the condition that the receiving equipment is normally used, the consistency of amplitude and phase parameters of the multipath radio frequency channels can be achieved through one-time correction, the capacity of further calibrating absolute time delay and amplitude is achieved, and meanwhile, the capacity of detecting faults of the multipath radio frequency channels of the array antenna is achieved through cooperation of the signal processing module and the information processing module.
Example 3
The invention discloses a method for rapidly correcting multiple radio frequency channels of a GNSS array antenna on line, which comprises the following steps:
s1, starting a multi-radio frequency channel on-line rapid correction system of a GNSS array antenna, and measuring to obtain delay time of the system.
Specifically, when the system is started, initial correction is performed, and at this time, each channel can perform correction of hardware time delay at the same time. The specific flow is shown in fig. 2.
Measuring hardware delay: the signal and information processing module controls the radio frequency distribution network to switch each radio frequency switch to a corresponding link of the signal generating module, enables the signal generating module, and sends control information to the signal generating module, and the control information is the starting point of timing time at the moment.
When the signal and information processing module receives the coherent correction signal, this is the end of the timing time. The time difference is noted as t Total (S) .
As shown in fig. 3, the time counted:
t Total (S) ＝t1+t2+t3+t4
where t 1、t3、t5 is the propagation time of the signal in the circuit board. t 1 is the time elapsed for the signal and information processing module to enable the signal generation module and send control information to the signal generation module; t 2 is the time that the signal generation module takes from receiving the control information to sending out the coherence correction signal; t 3 is the time that the coherent correction signal takes to reach the radio frequency distribution network from the transmission of the multi-channel radio frequency signal line; t 5 is the time that the external signal has elapsed to reach the radio frequency distribution network; t 4 is the time that the RF distribution network transmits a coherent correction signal or an external signal, generates an RF signal through a plurality of RF channels, and then reaches the signal and the information processing module.
Taking a microstrip line as an example, 50 ohm impedance control is performed on the surface layer of the circuit board, the distance between the microstrip line and the bottom reference layer is 8.5mil, the relative dielectric constant is 4.2, the line width is 15mil, and the simulation result shows that the delay result is 149.216ps/in.
If the sampling frequency is chosen to be 100MHz, the time interval between sampling points is 10ns. Assuming a transmission line length of 200 mils, the delays of the t1, t3, t5 portions are 149.216ps/in 200 mils = 29.8432ps, with little effect being negligible.
In a practical circuit, delay is mainly caused by a chip and various devices, and the influence of a transmission line with a short length is negligible.
T 2 is the time from the receiving of the control information to the generating of the coherent correction signal by the signal generating module, which is generally more than 10ns, and is not negligible. In the test system, the delay time t 2 from the input of the enable to control signal to the output of the coherent correction signal needs to be measured in advance and the data stored in the system.
The actual delay time caused by the radio frequency channel is:
tdelay＝t Total (S) -t2+Δt
the absolute time delay of each channel is obtained, so that delay errors brought by a hardware system during high-precision time-giving are compensated.
Further, since Δt is an neglected delay, which may be omitted in a hardware implementation, the delay time caused by the radio frequency channel may be reduced to:
tdelay＝t Total (S) -t2
s2, carrying out consistency correction on the multi-channel radio frequency channels to obtain a plurality of digital filter coefficients corresponding to the multi-channel radio frequency channels one by one, as shown in fig. 4.
The consistency correction of the multipath radio frequency channels is realized mainly by a digital filter, and the coefficients of the digital filter are regulated so that the amplitude-frequency response and the phase-frequency response of the coherent correction signals of different radio frequency channels tend to be consistent; the digital filter refers to an FIR (finite length unit impulse response, finite Impulse Response) filter, also called a non-recursive filter, is the most basic element in a digital signal processing system, can ensure any amplitude-frequency characteristic and has strict linear phase-frequency characteristic, and meanwhile, the unit sampling response is finite, so that the filter is a stable system.
Taking an N-order digital filter as an example, n=2 K; among these, the benefit of choosing the power of k of 2 is that the fast fourier transform (fft) can be applied directly, while applying fft to other values requires the addition of 0 to a fixed length, i.e. the power of k of 2.
According to the nature of convolution, there are respectively in the time domain and the frequency domain:
Y(ω)＝X(ω)·H(ω)
Wherein x (n) is an original time domain signal obtained after the adc samples the radio frequency signal, h (n) is a filter coefficient, and y (n) is a corrected time domain signal; x (omega) is an original frequency domain signal obtained after the adc samples the radio frequency signal, and H (omega) is Fourier transform corresponding to the filter coefficient.
For the time domain nth order coefficient H (N) of the filter, the corresponding fourier transformed frequency domain is expressed as H (ω) with N corresponding frequency bins.
Then the sampling rate is set to be Fs, and the frequency corresponding to the Mth point is set to beThe signal generation module needs to generate the frequencies of the N corresponding frequency points.
And (3) respectively inputting homologous coherent correction signals of a single frequency point into each channel at the beginning of equalization, sampling the coherent correction signals through an ADC (analog to digital converter) as N points after the coherent correction signals are stable, and respectively recording the data of each channel as d1 (N), d2 (N) and d3 (N).
And performing FFT conversion on the obtained data of each channel to obtain D1 (N), D2 (N) and D3 (N).
Dividing the ideal reference channel H ref by the corresponding frequency point of the channel to be balanced to obtain H i＝Href/Di (N)
The calculation was repeated a number of times and the average was taken.
Changing the frequency point of the signal, and repeating the steps until all the frequencies of the N corresponding frequency points are tested. The method comprises the following steps:
H＝{H1,H2......HN}
And carrying out inverse Fourier transform on the H to obtain hi, thereby obtaining the digital filter coefficient of the channel. The obtained system response H can be extracted or interpolated according to different requirements, and then the inverse Fourier transform is performed, so that various filter coefficients meeting specific requirements can be obtained rapidly.
And (3) for different signals passing through different radio frequency channels, entering corresponding digital filters for processing, and performing hi calculation on each channel of radio frequency channel to obtain digital filter coefficients of each channel, so as to complete the equalization process.
In the running process of the device equipment, the equipment test is carried out:
Firstly, selecting a single radio frequency channel through a radio frequency selection network each time, testing hardware delay time according to a hardware delay measurement method, selecting one of the channels as a reference channel, and sequentially selecting one of the rest radio frequency channels to finish consistency correction relative to the reference channel.
S3, based on the digital filter coefficients, processing the external satellite navigation signals, and eliminating the influence of inconsistent multipath radio frequency channels on the external satellite navigation signals.
Compared with the prior art, the on-line rapid correction method for the multiple radio frequency channels of the GNSS array antenna provided by the embodiment of the invention not only can support the correction of the information such as the relative time delay, frequency, amplitude, phase and the like of the multiple radio frequency channels, but also can measure the hardware absolute time delay of each channel of radio frequency channel to signals of different frequency points at one time, thereby being capable of compensating the problems such as differential code deviation, differential phase deviation and the like caused by the hardware delay and meeting the high-precision timing and positioning application of the array antenna under the interference condition.
Those skilled in the art will appreciate that all or part of the flow of the methods of the embodiments described above may be accomplished by way of a computer program to instruct associated hardware, where the program may be stored on a computer readable storage medium. Wherein the computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, etc.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The system is characterized by comprising a signal generation module, a radio frequency distribution network, a plurality of radio frequency channels and a signal and information processing module; wherein,
The signal generation module is used for generating a coherent correction signal to the radio frequency distribution network;
The radio frequency distribution network is used for transmitting the coherent correction signal to the multipath radio frequency channels in a self-checking stage or transmitting an external signal received through an antenna to the multipath radio frequency channels in an actual use stage;
The multipath radio frequency channel is used for processing the coherent correction signal in a self-checking stage to obtain a first radio frequency signal and transmitting the first radio frequency signal to the signal and information processing module; the system is also used for processing the external signal in the actual use stage to obtain a second radio frequency signal and transmitting the second radio frequency signal to the signal and information processing module;
the signal and information processing module is used for processing the first radio frequency signal in a self-checking stage to realize the correction of a plurality of radio frequency channels and the test of system delay time; and the second radio frequency signal is processed in the actual use stage, so that the influence of the inconsistency of the multipath radio frequency channels on the external signal is eliminated.
2. The system of claim 1, wherein the signal and information processing module is further configured to enable the signal generating module during the self-test phase, send control information to the signal generating module, and control the signal generating module to generate the coherent correction signal.
3. The system of claim 2, wherein the signal generating module comprises a PLL and a power divider, the PLL being configured to be co-source with a plurality of rf channels, for generating corresponding coherent correction signals and inputting the signals into the plurality of rf channels; wherein, by rewriting the control word of the PLL, any path of radio frequency channel generates a required single frequency signal; and when the single-frequency signals in the radio frequency channels have the same frequency and the phase difference is fixed, obtaining the coherent correction signals in the multiple radio frequency channels.
4. The system of claim 3, further comprising a crystal oscillator configured to generate a mixing clock to the multiple radio frequency channels, wherein the multiple radio frequency channels process the coherent correction signal based on the mixing clock to obtain a first radio frequency signal, and process an external signal based on the mixing clock to obtain a second radio frequency signal; the crystal oscillator is also used for generating a sampling clock to the signal and information processing module, the signal and information processing module processes the first radio frequency signal based on the sampling clock to realize correction of multiple paths of radio frequency channels and test of system delay time, processes the second radio frequency signal based on the sampling clock, and eliminates the influence of inconsistent multiple paths of radio frequency channels on the external signal.
5. The system of claim 4, further comprising a plurality of rf signal lines of equal length between the signal generation module and the rf distribution network for transmitting the coherent correction signals to the rf distribution network.
6. The system for online rapid calibration of multiple rf channels of a GNSS array antenna of claim 5, wherein the rf distribution network comprises a plurality of independent rf switches in one-to-one correspondence with each rf channel for switching to allow the system to enter a self-test phase or an actual use phase; when the system is switched to be communicated with the signal generation module, the system enters a self-checking stage, so that the coherent correction signal can be transmitted to a corresponding radio frequency channel; when the system is switched to be communicated with the external antenna, the system enters an actual use stage, so that external signals can be transmitted to the corresponding radio frequency channel.
7. The system of claim 6, wherein each of the plurality of rf channels comprises, in order, a same rf filter, a low noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier, and a variable gain intermediate frequency amplifier; wherein,
The radio frequency filter is used for filtering out-of-band interference signals; the low-noise amplifier is used for amplifying and filtering signals obtained after out-of-band interference signals to obtain first radio frequency signals or second radio frequency signals; the mixer is used for down-converting the first or second radio frequency signals to an intermediate frequency to obtain intermediate frequency signals; the intermediate frequency filter is used for filtering interference signals in the intermediate frequency signals; the intermediate frequency amplifier is used for amplifying the intermediate frequency signal after filtering the interference signal based on the OIP3 index of the whole link; the variable gain amplifier is used for finely adjusting the multipath channels so that the amplitude-frequency characteristics among the multipath channels of the system are consistent.
8. A multi-radio frequency channel on-line rapid calibration method based on the on-line rapid calibration system of any one of claims 1-7, comprising the steps of:
In the correction stage, starting a multi-radio frequency channel on-line rapid correction system of the GNSS array antenna, and measuring to obtain delay time of the system;
Carrying out consistency correction on a plurality of paths of radio frequency channels to obtain a plurality of digital filter coefficients corresponding to the paths of radio frequency channels one by one;
in the actual use stage, external satellite navigation signals are processed based on the digital filter coefficients, and the influence of inconsistent multipath radio frequency channels on the external satellite navigation signals is eliminated.
9. The system for online rapid calibration of multiple rf channels of a GNSS array antenna of claim 8, wherein starting the system for online rapid calibration of multiple rf channels of a GNSS array antenna, measuring the delay time of the system, comprises:
measuring hardware delay: the signal and information processing module controls the radio frequency distribution network to switch each radio frequency switch to a corresponding link of the signal generating module, enables the signal generating module, and sends control information to the signal generating module, wherein the control information is the starting point of timing time;
When the signal and information processing module receives the coherent correction signal, the signal and information processing module is the end point of the timing time, and the time difference is recorded as t Total (S) ; the time counted is:
t Total (S) ＝t1+t2+t3+t4
Wherein t 1 is the time elapsed for the signal and information processing module to enable the signal generation module and send control information to the signal generation module; t 2 is the time that the signal generation module takes from receiving the control information to sending out the coherence correction signal; t 3 is the time that the coherent correction signal takes to reach the radio frequency distribution network from the transmission of the multi-channel radio frequency signal line; t 4 is the time that the radio frequency distribution network sends out a coherent correction signal or an external signal, generates a radio frequency signal through a plurality of radio frequency channels and then reaches the signal and the information processing module; the actual delay time caused by the radio frequency channel is:
tdelay＝t Total (S) -t2+Δt
the absolute time delay of each channel is obtained, so that delay errors brought by a hardware system during high-precision time-giving are compensated.
10. The system for online rapid calibration of multiple rf channels of a GNSS array antenna of claim 9, wherein performing a consistency calibration on multiple rf channels to obtain multiple digital filter coefficients corresponding to the multiple rf channels one-to-one, comprises:
correcting the consistency of the multipath radio frequency channels, and enabling the amplitude-frequency response and the phase-frequency response of the coherent correction signals of different radio frequency channels to be consistent by adjusting the digital filter coefficients;
according to the nature of convolution, there are respectively in the time domain and the frequency domain:
Y(ω)＝X(ω)·H(ω)
Wherein x (n) is an original time domain signal obtained after the adc samples the radio frequency signal, h (n) is a digital filter coefficient, and y (n) is a corrected time domain signal; x (omega) is an original frequency domain signal obtained after the adc samples the radio frequency signal, and H (omega) is Fourier transform corresponding to the digital filter coefficient;
For a time domain nth order coefficient H (N) of the digital filter, the corresponding fourier transformed frequency domain is expressed as H (ω) having N corresponding frequency bins;
The sampling rate is Fs, the frequency corresponding to the Mth point is The signal generating module needs to generate the frequencies of the N corresponding frequency points;
After the coherent correction signals are stabilized, sampling the coherent correction signals through an ADC (analog to digital converter) at N points, and recording the data of each channel as d1 (N), d2 (N) and d3 (N) respectively;
and performing FFT conversion on the obtained data of each channel to obtain D1 (N), D2 (N) and D3 (N).
Dividing the ideal reference channel H ref by the corresponding frequency point of the channel to be balanced to obtain H i＝Href/Di (N);
Repeating the calculation for a plurality of times, and taking an average value;
changing the frequency point of the signal, repeating the steps until all the tests of the frequencies of the N corresponding frequency points are completed, and obtaining:
H＝{H1,H2......HN}
Performing inverse Fourier transform on the H to obtain hi, thereby obtaining a digital filter coefficient of the channel; and then, different signals passing through different radio frequency channels enter corresponding digital filters to be processed, and hi is calculated for each channel of radio frequency channel to obtain the digital filter coefficient of each channel.
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