Wide / narrow band signal synchronization measurement method based on time scale interpolation and fractional delay filtering

Abstract

This invention provides a method for synchronizing wideband and narrowband signals based on time-stamped interpolation and fractional delay filtering, comprising: S1. Signal preprocessing; S2. Time-stamped synchronization processing; S3. Phase synchronization processing; S4. ILS signal processing; S5. Station identification code processing; S6. DVOR signal processing. This invention aims to overcome the time delay difference problem caused by the reliance on clock synchronization methods for wideband and narrowband signal synchronization in existing technologies. It eliminates the time delay difference between channels with different sampling rates through a time-stamped interpolation algorithm and achieves cross-channel phase synchronization using a fractional delay filter combined with phase compensation technology, providing technical support for the accurate analysis of navigation signals.

Description

Technical Field

[0001] This invention relates to the field of signal processing technology, and in particular to a method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering. Background Technology

[0002] Currently, the technologies and equipment used for receiving and acquiring ILS, DVOR, and MB signals are mostly developed and manufactured in Europe and the United States. In domestic research, the Civil Aviation University of China has developed underlying algorithms and related technologies for the AD9361.

[0003] By collecting the IQ signals of the ILS, DVOR, and MB transmitted signals from civil aviation signal transmitting equipment, the collected signal patterns are converted into formulas to form an algorithm for receiving signals, ensuring that the algorithm can identify ILS, DVOR, and MB signals and read their signal strength and modulation mode in both indoor and outdoor fields.

[0004] The existing equipment and technologies are all foreign, and the corresponding algorithms are theoretically similar, but certain errors have occurred in the processing and analysis of key values. Especially when synchronizing wide and narrow band signals, the traditional solution uses clock synchronization, which cannot eliminate the time delay difference between channels with different sampling rates, resulting in insufficient phase synchronization accuracy and affecting the accurate analysis of navigation signals. Summary of the Invention

[0005] This invention provides a method for synchronizing wideband and narrowband signals based on time-stamped interpolation and fractional delay filtering. Signal preprocessing is performed using an AD9361 and a ZYNQ FPGA, dividing the wideband signal into narrowband processing. A time-stamped interpolation algorithm is used to eliminate delay differences between channels with different sampling rates. A fractional delay filter combined with phase compensation technology is employed to achieve cross-channel phase synchronization. This method can accurately calculate key performance indicators of signals such as ILS and DVOR. In its heading test indicators, the RFLEVEL measurement tolerance is ±1.0 dBm in the range of -87 dBm to -10 dBm, providing effective support for the accurate analysis of navigation signals.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering includes: S1. Signal preprocessing: Acquire radio frequency signals, perform low-noise amplification, and orthogonal mixing with the local oscillator signal to obtain IQ signals. Then, use filtering and an AD converter to obtain two digital intermediate frequency signals. The digital intermediate frequency signals are processed by digital down-conversion to obtain DDC broadband signals. Then, according to the characteristics of the signal under test, the DDC broadband signals are divided into four narrowband signals, namely DDC1 signal, DDC2 signal, DDC3 signal and DDC4 signal, to reduce the sampling rate of each signal. S2. Time stamp synchronization processing: The four narrowband signals and the DDC wideband signal are time-stamped using a unified clock. The fractional delay is calculated based on the time stamp difference using a time stamp interpolation algorithm, and fractional delay filtering is implemented using a Farrow structure to adjust the time delay of the subsampling period. S3. Phase synchronization processing; Real-time detection of the phase difference between the four narrowband signals and the DDC broadband signal after time-stamp synchronization processing at the target frequency, and use a second-order phase-locked loop to control the compensation amount; S4. ILS signal processing: AM demodulation is performed on the DDC1 signal after phase synchronization processing to obtain two time-domain signals; FFT operation is performed on the time-domain signals to obtain the spectrum; the carrier power at 0Hz, the signal power at 90Hz, and the signal power at 150Hz are extracted from the spectrum as FFT data, and parameter calculation is performed to obtain the key indicators of the ILS signal. S5. Station identification code processing; Obtain the IQ data of the identification code from the DDC2 signal after phase synchronization processing, perform pulse demodulation to obtain a time-domain pulse signal; reduce the signal bandwidth through a low-pass filter, and then reduce the data volume through sampling; determine the number of consecutive high and low levels to obtain the Morse code and look up the identification code in the table; S6. DVOR signal processing: The phase-synchronized DDC3 signal is distributed into three narrowband sub-bands. The first sub-band is demodulated with AM to obtain the reference signal, the second sub-band is demodulated with FM to obtain the variable signal, and the third sub-band is demodulated with pulse to obtain the pulse signal. The reference signal, variable signal, and pulse signal are used to calculate the measurement parameters.

[0007] In this manual, the radio frequency signal in S1 is acquired by the radio frequency zero intermediate frequency transceiver AD9361. The operating frequency range of AD9361 is 70MHz to 6.0GHz. The sampling rate is configured to be 51.2MHz / s, bandwidth is 40MHz, gain is 63dB, and the frequency of the digital intermediate frequency signal is 10MHz through the SDK software.

[0008] In this specification, the time-stamped interpolation algorithm in S2 uses a unified clock to time-stamp the four narrowband signals and the DDC wideband signal. The minimum precision of the time stamp is 1 / 1000 of the sampling period, and the time stamp difference resolution used to calculate the fractional delay is ≤0.1. μs .

[0009] In this specification, the fractional delay filter of the Farrow structure in S2 uses a polynomial fitting coefficient generation method, which is achieved by adjusting the delay time. δt With sampling period T ratio μ = δt / TSubstituting into the polynomial generates adjustable filter coefficients, enabling subsampling delay adjustment from 0.01 to 10 sampling periods.

[0010] In this specification, the transfer function of the second-order phase-locked loop in S3 is: ; This is the proportionality coefficient. Here, z represents the integral coefficients, and z represents the complex frequency domain variables of the discrete-time system.

[0011] In this manual, the parameter tuning rules for the second-order phase-locked loop are as follows: ; ; The damping coefficient is... It is the natural angular frequency. This is for frequency-controlled gain.

[0012] In this specification, the FFT operation in S4 uses a 16384-point sliding window mode to perform complex number operations on continuous time-domain signals. The measurement error of the 0Hz carrier power, 90Hz and 150Hz signal power extracted from the spectrum is ≤±0.5dB.

[0013] In this specification, in S5, the signal bandwidth is reduced by a low-pass filter with a cutoff frequency of 50Hz, and the data volume is reduced by sampling with a sampling coefficient of 40. After sampling, the signal sampling rate is reduced to 100Hz. The dots and dashes of Morse code are distinguished by judging the duration of the high level.

[0014] In this specification, in S6, the reference signal channel uses a 1kHz bandwidth low-pass filter to extract the 30Hz AM modulation component, and the variable signal channel uses a 4kHz bandwidth low-pass filter to retain the 9960Hz subcarrier FM modulation bandwidth.

[0015] In this specification, the phase-synchronized DDC4 signal is used for pointing beacon signal processing, the 75MHz MB signal is pulse demodulated, the modulation index and the identification code of 300-3000Hz are calculated, and the modulation index measurement error is ≤±0.2%.

[0016] In summary, the present invention has at least the following beneficial effects: This invention achieves time-frequency synchronization of wide and narrow band signals through time-stamped interpolation and fractional delay filtering, significantly improving the measurement accuracy of navigation signals. By eliminating delay differences between channels with different sampling rates through time-stamped interpolation and fractional delay filtering, it provides a foundation for accurate phase difference measurement. The wideband signal is processed into four narrowband channels to reduce the sampling rate. Combined with the subsampling delay adjustment of the Farrow structure filter, processing delay is reduced to meet real-time measurement requirements. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the method for synchronous measurement of wide and narrow band signals based on time-scale interpolation and fractional delay filtering involved in this invention.

[0019] Figure 2 This is a schematic diagram of the two time-domain signals, 90Hz and 150Hz, obtained by AM demodulation involved in this invention.

[0020] Figure 3 This is a schematic diagram of the spectrum obtained by FFT calculation involved in this invention.

[0021] Figure 4 This is a schematic diagram of the pulse waveform involved in this invention.

[0022] Figure 5 This is a schematic diagram of the Morse code lookup table involved in this invention.

[0023] Figure 6 This is a schematic diagram of the synchronization process involved in this invention.

[0024] Figure 7 This is a schematic diagram of the closed-loop control architecture involved in this invention. Detailed Implementation

[0025] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0026] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0027] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 1 As shown, this embodiment provides a method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering, including: S1. Signal preprocessing: Acquire radio frequency signals, perform low-noise amplification, and orthogonal mixing with the local oscillator signal to obtain IQ signals. Then, use filtering and an AD converter to obtain two digital intermediate frequency signals. The digital intermediate frequency signals are processed by digital down-conversion to obtain DDC broadband signals. Then, according to the characteristics of the signal under test, the DDC broadband signals are divided into four narrowband signals, namely DDC1 signal, DDC2 signal, DDC3 signal and DDC4 signal, to reduce the sampling rate of each signal. S2. Time stamp synchronization processing: The four narrowband signals and the DDC wideband signal are time-stamped using a unified clock. The fractional delay is calculated based on the time stamp difference using a time stamp interpolation algorithm, and fractional delay filtering is implemented using a Farrow structure to adjust the time delay of the subsampling period. S3. Phase synchronization processing; Real-time detection of the phase difference between the four narrowband signals and the DDC broadband signal after time-stamp synchronization processing at the target frequency, and use a second-order phase-locked loop to control the compensation amount; S4. ILS signal processing: AM demodulation is performed on the DDC1 signal after phase synchronization processing to obtain two time-domain signals; FFT operation is performed on the time-domain signals to obtain the spectrum; the carrier power at 0Hz, the signal power at 90Hz, and the signal power at 150Hz are extracted from the spectrum as FFT data, and parameter calculation is performed to obtain the key indicators of the ILS signal. S5. Station identification code processing; Obtain the IQ data of the identification code from the DDC2 signal after phase synchronization processing, perform pulse demodulation to obtain a time-domain pulse signal; reduce the signal bandwidth through a low-pass filter, and then reduce the data volume through sampling; determine the number of consecutive high and low levels to obtain the Morse code and look up the identification code in the table; S6. DVOR signal processing: The phase-synchronized DDC3 signal is distributed into three narrowband sub-bands. The first sub-band is demodulated with AM to obtain the reference signal, the second sub-band is demodulated with FM to obtain the variable signal, and the third sub-band is demodulated with pulse to obtain the pulse signal. The reference signal, variable signal, and pulse signal are used to calculate the measurement parameters.

[0029] It should be noted that the parameter calculations involved in this invention are all existing technologies. The focus of this invention is to overcome the time delay difference problem caused by the reliance on clock synchronization methods for wide and narrow band signal synchronization in existing technologies, eliminate the time delay difference between channels with different sampling rates through a time-scale interpolation algorithm (S2), and achieve cross-channel phase synchronization by using a fractional delay filter combined with phase compensation technology (S3), thus providing technical support for the accurate analysis of navigation signals.

[0030] In some embodiments, the radio frequency signal in S1 is acquired by the radio frequency zero intermediate frequency transceiver AD9361. The operating frequency range of AD9361 is 70MHz to 6.0GHz. The sampling rate is configured to be 51.2MHz / s, the bandwidth is 40MHz, and the gain is 63dB through SDK software. The frequency of the digital intermediate frequency signal is 10MHz.

[0031] In some embodiments, the time-stamped interpolation algorithm in S2 times-stamps the four narrowband signals and the DDC wideband signal using a unified clock. The minimum precision of the time stamping is 1 / 1000 of the sampling period, and the time stamp difference resolution used to calculate the fractional delay is ≤0.1. μs .

[0032] In some embodiments, the fractional delay filter of the Farrow structure in S2 is generated using a polynomial fitting coefficient generation method, by adjusting the delay time... δt With sampling period T ratio μ = δt / T Substituting into the polynomial generates adjustable filter coefficients, enabling subsampling delay adjustment from 0.01 to 10 sampling periods.

[0033] In some embodiments, the transfer function of the second-order phase-locked loop in S3 is: ; This is the proportionality coefficient. The integral coefficient is... z These represent the complex frequency domain variables of a discrete-time system.

[0034] In some embodiments, the parameter tuning rules for the second-order phase-locked loop are as follows: ; ; The damping coefficient is... It is the natural angular frequency. This is for frequency-controlled gain.

[0035] In some embodiments, the FFT operation in S4 adopts a 16384-point sliding window mode to perform complex number operations on continuous time-domain signals, and the measurement error of the 0Hz carrier power, 90Hz and 150Hz signal power extracted from the spectrum is ≤±0.5dB.

[0036] In some embodiments, in S5, the signal bandwidth is reduced by a low-pass filter with a cutoff frequency of 50Hz, and the data volume is reduced by sampling with a sampling coefficient of 40. The sampling rate of the sampled signal is reduced to 100Hz, and the dots and dashes of Morse code are distinguished by judging the duration of the high level.

[0037] In some embodiments, in S6, the reference signal channel uses a 1kHz bandwidth low-pass filter to extract the 30Hz AM modulation component, and the variable signal channel uses a 4kHz bandwidth low-pass filter to retain the 9960Hz subcarrier FM modulation bandwidth.

[0038] In some embodiments, the phase-synchronized DDC4 signal is used for pointing beacon signal processing, the 75MHz MB signal is pulse demodulated, the modulation index and the identification code of 300-3000Hz are calculated, and the modulation index measurement error is ≤±0.2%.

[0039] The technical concept of this invention is as follows: 1. Signal preprocessing Signal preprocessing was performed using Analog Devices' AD9361 RF zero-IF transceiver combined with a ZYNQ FPGA. The AD9361 operates in the 70MHz–6.0GHz frequency range. Configurable via SDK software, it features a sampling rate of 51.2MHz / s, a bandwidth of 40MHz, and a gain of 63dB. The local oscillator frequency is set based on the received signal frequency. The received RF signal undergoes low-noise amplification, and after quadrature mixing with the local oscillator signal, an I / O signal is obtained. This signal is then filtered and converted to an AD converter to obtain two 12-bit digital intermediate frequency (IF) signals at a frequency of 10MHz, which are then transmitted to the ZYNQ chip via differential connections. Since the AD9361 operates at 160MHz and has a sampling rate of 51.2MHz, the initial sampled data volume is relatively large (51200 samples / millisecond). A filter was designed to adjust the decimation factor and reduce the sampling rate. Furthermore, at the PL terminal, the wideband signal is divided into four narrowband signals based on the characteristics of the measured signal for real-time processing.

[0040] 2. ILS signal processing ILS signal processing mainly calculates the key performance indicators of ILS signals. ILS signal processing can be divided into two parts: first, for LOC signals, it mainly calculates the modulation amplitude of 90Hz and 150Hz signals, as well as the DDM and SDM between these two signals; second, for GS signals, the parameters are the same as those for localizer beacon measurements, only the required index values ​​are different.

[0041] AM demodulation was performed on the preprocessed DDC signal to obtain the time-domain signals of the 90Hz and 150Hz signals, as follows: Figure 2 As shown; an FFT operation was performed on the time-domain signal. To ensure signal accuracy, a sliding window mode was used during the calculation. The spectrum was obtained by performing FFT on 16384 consecutive points in the time domain, as shown in the figure. Figure 3As shown, the FFT output reveals three stable peaks: the carrier power at 0 Hz, the signal power at 90 Hz, and the signal power at 150 Hz. The FFT data is used to calculate key ILS metrics using a parameter calculation module.

[0042] ILS signal processing mainly performs calculations of key performance indicators, including LOC and GS signal processing: AM demodulation is performed on the preprocessed DDC signal to obtain the time-domain waveforms of the 90Hz and 150Hz signals; The time-domain signal was subjected to FFT operation using a 16384-point sliding window mode to obtain the spectrum containing the 0Hz carrier power, 90Hz and 150Hz signal power; Input the FFT data into the parameter calculation module to obtain key indicators such as DDM and SDM.

[0043] 3. Station Identification Code Decryption Each navigation station has its own unique identification code, which is contained within the 1020Hz audio signal. The presence and duration of the 1020Hz signal are controlled by Morse code transmission. Typical Morse code consists of 2-3 English letters, with a transmission rate of approximately 7 digits per minute. ICAO recommends transmitting at least three times at equal intervals every 30 seconds. Verification is performed by checking if the identification code of the measured station matches the one published on the aeronautical chart. Since the Morse code information is contained within the 1020Hz audio signal, the first step is to acquire the 1020Hz audio signal. The IQ data of the identification code is obtained from the pre-processed DDC4. This data is demodulated to obtain a time-domain pulse signal. After demodulation, the pulse signal enters the pulse calculation module, which reduces the sampling rate by decimation to facilitate subsequent calculations.

[0044] like Figure 4 As shown, the demodulated pulse waveform: Based on the characteristics of Morse code, the shortest duration of Morse code is 0.1s, corresponding to a maximum signal bandwidth of 10Hz. This allows for further reduction of the sampling rate and improvement of the processing speed. By using a low-pass filter with a cutoff frequency of 50Hz to reduce the signal bandwidth, and then reducing the data volume through sampling with a sampling coefficient of 40, the sampling frequency becomes 100Hz. This significantly reduces the number of subsequent processing points; only 100 data points need to be processed per second. Even the shortest Morse code requires only 10 high-level data points, and the longest, 0.48s, requires only 48 data points. As can be seen from the diagram, Morse code is a series of high and low level changes. By marking high level as 1 and low level as 0, an array of 0 and 1 changes is obtained. By counting consecutive 0s and 1s, a set of Morse code composed of dots and dashes is obtained. The Morse code is then looked up in a table in the parameter calculation module (…). Figure 5 ), and obtain the identification code.

[0045] The navigation station identification code is contained in the Morse code of the 1020Hz audio signal. The processing flow is as follows: IQ data of the identification code is extracted from the preprocessed DDC2 signal and obtained as a time-domain pulse signal through pulse demodulation. The signal bandwidth is reduced by using a 50Hz low-pass filter, and the sampling rate is reduced to 100Hz by using 40x sampling. The Morse code is parsed based on the duration of the high / low level (dot: 0.1s, dash: 0.48s), and the station identification code is obtained by looking up the table.

[0046] 4. DVOR signal processing The DVOR signal comprises a DC carrier, a 30Hz reference signal, a 9980Hz subcarrier, and a station identification signal, and is processed in three sub-bands based on its characteristics: The first sub-band processes the DC carrier and the 30Hz reference signal, and obtains the reference signal through AM demodulation. The second sub-band processes the 9980Hz subcarrier and obtains a 30Hz variable signal through FM demodulation. The third sub-band processes and identifies the signal, and obtains pulse data through pulse demodulation. The three signals complete the calculation of parameters such as azimuth angle in the parameter calculation module. The specific DVOR signal processing flow includes: Broadband signal acquisition: Receiving frequency band: 108-118MHz VHF band; ADC sampling: satisfies Nyquist's theorem (≥2 × highest frequency); Output: Complex baseband IQ data stream; Signal separation and preprocessing: Reference signal channel (1kHz bandwidth): Down-conversion: Moving the reference carrier (e.g., 108MHz+f0) to the baseband; Filtering: A 1kHz low-pass filter is used to extract the AM modulation component; Variable signal channel (4kHz bandwidth): Downconversion: Moving the 9960Hz subcarrier to the baseband; Filtering: A 4kHz low-pass filter preserves the FM modulation bandwidth; Reference signal demodulation (30Hz AM demodulation): Amplitude demodulation: Calculating the amplitude of the IQ signal ; For the first In-phase at each sampling point Quantity; For the first orthogonal sampling points Quantity; For the first Time index of each sampling point; For the first The signal amplitude at each sampling point.

[0047] Low-pass filtering: 30Hz cutoff frequency, extract AM envelope signal; Phase-locked loop (PLL): tracks a 30Hz reference phase and suppresses noise; Subcarrier signal demodulation (30Hz FM demodulation): Phase difference method: Calculate instantaneous phase ; Phase difference ; Integration operation: Accumulate the phase difference to recover the frequency offset; Low-pass filter: 30Hz cutoff, extracting the azimuth signal of FM modulation; Phase difference calculation and azimuth calculation: Zero-crossing detection: Aligning the reference with the 30Hz waveform of the variable signal; Cross-correlation algorithm: maximize the correlation between two signals and calculate the time delay difference; Azimuth formula: θ = ΔΦ / 2π × 180° (calibrated according to DVOR specifications); Anti-interference and fault-tolerant design: Adaptive filtering: suppressing out-of-band noise (such as the LMS algorithm); Multipath suppression: temporal equalization or spatial beamforming; Verification mechanism: CRC check or redundant channel verification of data validity.

[0048] The navigation signal measurement indicators achieved by this invention are as follows: The heading measurement parameters are as follows: a) Frequency range: 108.1~111.95MHz; b) Channel spacing: 50kHz; c) RFLEVEL radio frequency level range: 0dBm to -87dBm; d) RFLEVEL measurement tolerance: -87dBm to -10dBm: ±1.0dBm; -10dBm to 0dBm: ±2.0dBm; e) DDM modulation difference range: 0–40%; f) DDM error: 0DDM for channel: 0.07%DDM. Deviation from channel: 0.07%DDM ± 1.25% × DDM reading; g) SDM modulation scheme and range: 0–95%; h) SDM modulation and error: 0.5% DDM; i) Identification code frequency range: 1020Hz±50Hz; j) Identification code adjustment scheme: 1-55%; k) Identification code modulation error: ±1%; l) Low-frequency (90Hz, 150Hz) frequency accuracy: ±0.2%; m) Low-frequency (90Hz, 150Hz) modulation error: ±2%.

[0049] n) Frequency range: 5KHz~14KHz; o) Low-frequency phase: -180°~180°; The following are the metrics for the slide test: a) Frequency range: 329.15~335.0MHz; b) Channel spacing: 150kHz; c) RFLEVEL radio frequency level range: 10dBm to -70dBm; d) RFLEVEL measurement tolerance: -87dBm to -10dBm: ±1.0dBm; -10dBm to 0dBm: ±2.0dBm; e) DDM modulation difference range: 0–80%; f) DDM error: 0 DDM for channel deviation: 0.15% DDM. Deviation from channel: 0.15% DDM ± 1.25% × DDM reading; g) SDM modulation scheme and range: 0–95%; h) SDM modulation and error: 1% DDM; i) Low-frequency (90Hz, 150Hz) frequency accuracy: ±0.2%; j) Low-frequency (90Hz, 150Hz) modulation error: ±2%.

[0050] k) Frequency range: 4kHz~32kHz; l) Low-frequency phase: -180°~180°; The DVOR test parameters for VHF omnidirectional beacons are as follows: a) Frequency range: 108–118 MHz; b) Channel spacing: 50kHz; c) RFLEVEL radio frequency level range: 0dBm to -80dBm; d) RFLEVEL measurement tolerance: -80dBm to -10dBm: ±1.0dBm; -10dBm to 0dBm: ±2.0dBm; e) Azimuth error: -50dBm to 0dBm: 0.05°; -76dBm to -50dBm: ±0.2°; f) Adjustment depth range: 10%–50%; g) 30Hz / 9960Hz modulation depth range error: -50dBm~0dBm: ±0.6%. -76dBm~-50dBm: ±1%; h) Identification code frequency range: 1020Hz±50Hz; i) Identification code adjustment scheme: 1-55%; j) Identification code modulation error: ±1%; k) Frequency modulation index: 16±1.

[0051] The pointer beacon MB test metrics are as follows: a) Frequency range: 75MHz; b) RFLEVEL radio frequency level range: 0dBm to -83dBm; c) RFLEVEL measurement tolerance: -83dBm to -10dBm: ±1.0dBm; -10dBm to 0dBm: ±2.0dBm; d) Scope of adjustment: 80%–100%; e) Modulation error: ±0.2%; Identification code range: 300-3000Hz.

[0052] This invention achieves time-frequency synchronization of wideband and narrowband signals through the following core mechanisms (such as...). Figure 6 ): 1. Time stamp synchronization processing A unified clock is used to time-stamp the broadband signal and the four narrowband signals (DDC1-DDC4), and the fractional delay is calculated based on the time-stamp interpolation algorithm according to the time-stamp difference; (time-stamp alignment) Subsampling period delay adjustment is achieved using a Farrow-structured fractional delay filter (FDF). The filter expression is as follows: ; The output signal of the filter, i.e., at time t. The output sample values, These are time-varying filter coefficients, dependent on the fractional delay. Let the filter order be . For summation index; This is a delayed input signal sample.

[0053] coefficient Generated by polynomial fitting: ; . is the highest order of the polynomial; As a summation index, it ranges from 0 to M; The coefficients in the polynomial fitting depend on the pattern k and the power.

[0054] 2. Phase synchronization processing Phase Compensator (PC): In addition to the delay adjustment of FDF, phase compensation is also required for the signal to ensure that the broadband and narrowband signals achieve accurate phase alignment (not just timestamp alignment) on the target frequency components.

[0055] Real-time detection of the phase difference between wideband and narrowband signals at the target frequency: ; For reference signal; It is the complex conjugate of the narrowband signal, used to eliminate the influence of the imaginary part when calculating the phase difference.

[0056] The phase angle is calculated using the CORDIC algorithm; Closed-loop control based on a second-order phase-locked loop (PLL) Figure 7 ), transfer function: ; Parameter tuning rules: ; ; Dynamic phase compensation is achieved using a complex multiplication compensator: ; The compensated signal, i.e., the complex signal after phase compensation processing, in time... The value of . The signal is uncompensated (baseband signal), that is, at time point The original complex signal has not yet undergone phase compensation; It is a constant, approximately equal to 2.71828; The number is an imaginary number, satisfying j squared = -1; The estimated phase error is at time point . The phase value.

[0057] The phase prediction update formula is: ; Eliminate the remaining phase deviation. Finally, obtain the phase synchronization signal.

[0058] In summary, a unified clock is used for both broadband and narrowband sampling, with precise time marking. The fractional delay is calculated based on the time mark difference, and a Farrow structure is employed to achieve efficient and adjustable fractional delay. The phase difference between broadband and narrowband signals at the target frequency is detected in real time, and a second-order phase-locked loop (PLL) is used to control the compensation amount. A fractional delay filter addresses the "integer + fractional" sampling delay, and a phase compensator eliminates the remaining phase deviation. This invention achieves true phase synchronization of broadband and narrowband signals by decomposing the time delay into an integer sampling period (solved by clock synchronization) and a fractional sampling period (solved by FDF), combined with closed-loop phase compensation, providing a technical foundation for high-precision time difference measurement.

[0059] The embodiments described above are for illustrative purposes only and are not intended to limit the invention. Therefore, any changes in numerical values ​​or substitutions of equivalent elements should still fall within the scope of this invention.

[0060] The above detailed description will enable those skilled in the art to understand that the present invention can indeed achieve the aforementioned objectives and has complied with the provisions of the Patent Law.

[0061] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

[0062] It should be noted that the above description of the process is for illustrative purposes only and does not limit the scope of this specification. Those skilled in the art can make various modifications and changes to the process under the guidance of this specification. However, these modifications and changes remain within the scope of this specification.

[0063] The basic concepts have been described above. Obviously, for those skilled in the art who have read this application, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore, such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0064] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different positions in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0065] Furthermore, those skilled in the art will understand that aspects of this application can be described and illustrated through several patentable types or situations, including any new and useful combination of processes, machines, products, or substances, or any new and useful improvements thereof. Therefore, aspects of this application can be implemented entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. All of the above hardware or software can be referred to as a “unit,” “module,” or “system.” Furthermore, aspects of this application can take the form of a computer program product embodied in one or more computer-readable media, wherein computer-readable program code is contained therein.

[0066] The computer program code required for the operation of each part of this application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, and Python; general programming languages ​​such as C; Visual Basic, Fortran2103, Perl, COBOL2102, PHP, and ABAP; dynamic programming languages ​​such as Python, Ruby, and Groovy; or other programming languages. This program code can run entirely on the user's computer, or as a standalone software package on the user's computer, or partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer via any network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as Software as a Service (SaaS).

[0067] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this application are not intended to limit the order of the processes and methods of this application. Although some currently considered useful embodiments of the invention have been discussed in the foregoing disclosure by way of various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments of this application. For example, although the implementation of the various components described above can be embodied in a hardware device, it can also be implemented as a purely software solution, such as an installation on an existing server or mobile device.

[0068] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this approach of the present application should not be construed as reflecting an intention that the claimed subject matter requires more features than expressly recited in each claim. Rather, the subject of the invention should possess fewer features than in any single embodiment described above.

Claims

1. A method for wide and narrow band signal synchronization measurement based on time scale interpolation and fractional delay filtering, characterized in that, include: S1. Signal preprocessing: Acquire radio frequency signals, perform low-noise amplification, and orthogonal mixing with the local oscillator signal to obtain IQ signals. Then, use filtering and an AD converter to obtain two digital intermediate frequency signals. The digital intermediate frequency signals are processed by digital down-conversion to obtain DDC broadband signals. Then, according to the characteristics of the signal under test, the DDC broadband signals are divided into four narrowband signals, namely DDC1 signal, DDC2 signal, DDC3 signal and DDC4 signal, to reduce the sampling rate of each signal. S2. Time stamp synchronization processing: The four narrowband signals and the DDC wideband signal are time-stamped using a unified clock. The fractional delay is calculated based on the time stamp difference using a time stamp interpolation algorithm, and fractional delay filtering is implemented using a Farrow structure to adjust the time delay of the subsampling period. S3. Phase synchronization processing; The phase difference between the four narrowband signals and the DDC broadband signal after real-time time-stamping and synchronization is detected at the target frequency, and the compensation amount is controlled by a second-order phase-locked loop. S4. ILS signal processing; AM demodulation is performed on the DDC1 signal after phase synchronization processing to obtain two time-domain signals; FFT operation is performed on the time-domain signals to obtain the spectrum; the carrier power at 0Hz, the signal power at 90Hz, and the signal power at 150Hz are extracted from the spectrum as FFT data, and parameters are calculated to obtain the key indicators of the ILS signal. The key indicators include: channel DDM, SDM, 90Hz and 150Hz modulation, ILS identification code frequency and modulation, radio frequency level RFLEVEL, and frequency difference and low-frequency phase. S5. Station identification code processing; Obtain the IQ data of the identification code from the DDC2 signal after phase synchronization processing, perform pulse demodulation to obtain a time-domain pulse signal; reduce the signal bandwidth through a low-pass filter, and then reduce the data volume through sampling; determine the number of consecutive high and low levels to obtain the Morse code and look up the identification code in the table; S6. DVOR signal processing: The phase-synchronized DDC3 signal is distributed into three narrowband sub-bands. The first sub-band is demodulated using AM to obtain the reference signal, the second sub-band is demodulated using FM to obtain the variable signal, and the third sub-band is demodulated using pulse to obtain the pulse signal. The reference signal, variable signal, and pulse signal are used to calculate the measurement parameters, which include: azimuth angle, modulation depth at 30Hz and 9960Hz, frequency modulation index, and DVOR identification code frequency and modulation degree.

2. The method of claim 1, wherein, In S1, the radio frequency signal is acquired by the RF zero intermediate frequency transceiver AD9361. The operating frequency range of AD9361 is 70MHz to 6.0GHz. The sampling rate is configured to be 51.2MHz, the bandwidth is 40MHz, and the gain is 63dB through the SDK software. The frequency of the digital intermediate frequency signal is 10MHz.

3. The method of claim 1, wherein, The time-stamped interpolation algorithm in S2 uses a unified clock to time-stamp the four narrowband signals and the DDC wideband signal. The minimum precision of the time stamp is 1 / 1000 of the sampling period, and the time stamp difference resolution used to calculate the fractional delay is ≤0.

1. μs .

4. The method of claim 1, wherein, The fractional delay filter in the Farrow structure of S2 uses a polynomial fitting coefficient generation method, which involves adjusting the delay time... δt With sampling period T ratio μ = δt / T Substituting into the polynomial generates adjustable filter coefficients, enabling subsampling delay adjustment from 0.01 to 10 sampling periods.

5. The method of claim 1, wherein, The transfer function of the second-order phase-locked loop in S3 is: ； is a proportional coefficient, is an integral coefficient, and z represents a complex frequency domain variable of a discrete time system.

6. The method of claim 5, wherein, The parameter tuning rules for a second-order phase-locked loop are as follows: ； ； is the damping coefficient, is the natural angular frequency, is the frequency control gain.

7. The method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering according to claim 1, characterized in that, The FFT operation in S4 uses a 16384-point sliding window mode to perform complex number operations on continuous time-domain signals. The measurement error of the 0Hz carrier power, 90Hz and 150Hz signal power extracted from the spectrum is ≤±0.5dB.

8. The method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering according to claim 1, characterized in that, In S5, the signal bandwidth is reduced by a low-pass filter with a cutoff frequency of 50Hz, and the data volume is reduced by sampling with a sampling coefficient of 40. After sampling, the signal sampling rate is reduced to 100Hz. The dots and dashes of Morse code are distinguished by judging the duration of the high level.

9. The method for synchronous measurement of wide and narrow band signals based on time-scaled interpolation and fractional delay filtering according to claim 1, characterized in that, In S6, the reference signal channel uses a 1kHz bandwidth low-pass filter to extract the 30Hz AM modulation component, while the variable signal channel uses a 4kHz bandwidth low-pass filter to retain the 9960Hz subcarrier FM modulation bandwidth.

10. The method of claim 1, wherein, The phase-synchronized DDC4 signal was used for pointing beacon signal processing. The 75MHz MB signal was pulse demodulated, and the modulation index and identification code of 300-3000Hz were calculated. The modulation index measurement error was ≤±0.2%.

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