Method, device and electronic equipment for measuring the length of the symbol interval of a low carrier frequency CPFSK signal

Abstract

The application provides a symbol interval length measurement method and device of a low carrier frequency CPFSK signal and an electronic device, acquires additional phase information through IQ demodulation and generates a modulation absolute frequency curve, accurately determines a symbol interval starting point and an ending point by using a waveform intermediate value, and realizes measurement of an instantaneous symbol interval length; secondly, when the carrier frequency is lower than a preset threshold, the demodulation center frequency is offset from the carrier frequency to a target frequency, the maximum analysis bandwidth is expanded to twice the offset center frequency, thereby breaking through the limitation of twice the carrier frequency bandwidth, improving the sampling rate and time resolution capability. Thus, under the condition of a low carrier frequency, a high-resolution symbol interval length measurement result can still be obtained.

Description

Technical Field

[0001] This application relates to the field of wireless communication measurement technology, and in particular to a method, apparatus and electronic device for measuring the symbol interval length of a low carrier frequency CPFSK signal. Background Technology

[0002] In existing technologies, the digital modulation quality of CPFSK signals is typically measured using a vector signal analyzer. Parameters such as vector modulation error are obtained through steps including down-conversion, digital intermediate frequency (IF), IQ demodulation, and modulation data demodulation. However, when measuring the symbol interval length of low-carrier-frequency CPFSK signals, vector signal analyzers have the following problems: First, they usually only provide the measurement result of the average symbol rate error, which cannot meet the measurement requirements of the instantaneous symbol interval length; second, when the analysis bandwidth needs to cross the zero-point frequency, the maximum analysis bandwidth is limited by twice the carrier frequency, resulting in a limited sampling frequency and preventing further reduction of the sampling interval to improve time resolution. Summary of the Invention

[0003] This application provides a method, apparatus, and electronic device for measuring the symbol interval length of a low carrier frequency CPFSK signal, which is used to measure the instantaneous symbol interval length and improve the sampling rate and time resolution.

[0004] In a first aspect, embodiments of this application provide a method for measuring the symbol interval length of a low carrier frequency CPFSK signal, including: Receives digital intermediate frequency signals; The digital intermediate frequency signal is demodulated using IQ modulation to obtain the IQ signal; The additional phase of the measured signal is calculated based on the IQ signal, and the absolute modulation frequency curve is obtained based on the phase change; The start and end points of the symbol are determined based on the waveform midpoint of the modulation absolute frequency curve, and the symbol interval length measurement result is obtained based on the sampling interval count. When the carrier frequency of the CPFSK signal under test is lower than a preset threshold, the center frequency of the demodulation analysis is shifted from the carrier frequency to the target frequency to increase the analysis bandwidth.

[0005] Secondly, embodiments of this application provide a symbol interval length measurement device for low carrier frequency CPFSK signals, the device comprising: The receiving module is used to receive digital intermediate frequency signals; The demodulation module is used to perform IQ demodulation on the digitized intermediate frequency signal to obtain the IQ signal; The frequency curve generation module is used to calculate the additional phase of the measured signal based on the IQ signal, and obtain the modulation absolute frequency curve based on the phase change; The symbol boundary determination module is used to determine the start and end points of the symbol based on the waveform midpoint of the modulation absolute frequency curve, and to calculate the symbol interval length measurement result based on the sampling interval count. The center frequency control module is used to shift the center frequency of demodulation analysis from the carrier frequency to the target frequency when the carrier frequency of the CPFSK signal under test is lower than a preset threshold, so as to increase the analysis bandwidth.

[0006] Thirdly, embodiments of this application provide an electronic device, including: Memory, used to store one or more programs; processor; When the one or more programs are executed by the processor, the methods described in the first aspect and various possible implementations above are implemented.

[0007] The technical solutions provided in the embodiments of this specification may include the following beneficial effects: Compared to existing technologies, the symbol interval length measurement method, apparatus, and electronic device for low carrier frequency CPFSK signals provided in this application obtains additional phase information and generates a modulation absolute frequency curve through IQ demodulation. It accurately determines the start and end points of the symbols using the waveform's median value, thus achieving instantaneous symbol interval length measurement. Secondly, when the carrier frequency is below a preset threshold, the demodulation center frequency is shifted from the carrier frequency to the target frequency, expanding the maximum analysis bandwidth to twice that of the shifted center frequency. This overcomes the limitation of twice the carrier frequency bandwidth, improving the sampling rate and time resolution. Therefore, high-resolution symbol interval length measurement results can still be obtained under low carrier frequency conditions.

[0008] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this specification. Attached Figure Description

[0009] Figure 1 A flowchart illustrating a method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 2 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 3 A schematic diagram of a modulation absolute frequency curve provided in an embodiment of the present invention; Figure 4 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating an increase in maximum analysis bandwidth provided in an embodiment of the present invention; Figure 6 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 7 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 8 A schematic diagram of a symbol interval length measuring device for a low carrier frequency CPFSK signal provided in an embodiment of the present invention; Figure 9 A schematic diagram illustrating a possible implementation of a symbol interval length measurement device for a low carrier frequency CPFSK signal, provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0010] The exemplary embodiments will now be described in detail. When the description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this specification; they are merely exemplary embodiments of apparatuses and methods consistent with some aspects of this specification.

[0011] In this specification, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, the term "coupled connection" can be a direct electrical connection or an indirect electrical connection through an intermediate medium. The term "contact" can be direct contact or indirect contact through an intermediate medium.

[0012] In existing technologies, the digital modulation quality of CPFSK signals is typically measured using a vector signal analyzer. The measurement process of a vector signal analyzer includes: down-conversion to intermediate frequency (IF), digitization of the IF signal, IQ demodulation to obtain the original I and Q channels of the measured signal, demodulation of the modulation data according to the modulation type, generation of an ideal reference signal, and comparison of the measured signal with the reference signal to obtain the modulation error.

[0013] However, vector signal analyzers typically only provide the measurement result of the average symbol rate error. The principle is to calculate the average symbol rate by counting the total number of symbols over a certain period, and then compare this to the nominal symbol rate to obtain the error. However, this measurement method cannot reflect the actual length variation of each symbol interval, and cannot meet the measurement requirements of instantaneous symbol interval length. In some application scenarios, it is necessary to accurately measure the actual length of each symbol interval to evaluate the stability and consistency of modulation quality.

[0014] Specifically, the center carrier frequency used for demodulation analysis in a vector signal analyzer is consistent with the carrier frequency of the FSK signal. During spectrum shifting, the RF analysis bandwidth expands symmetrically to both sides of the center frequency. However, since the analysis bandwidth cannot cross the zero frequency (DC), the maximum analysis bandwidth is limited when the center frequency is low, and cannot exceed twice the FSK carrier frequency. For example, when the carrier frequency is 5MHz, the maximum usable analysis bandwidth is 10MHz.

[0015] Furthermore, since the analysis bandwidth directly corresponds to the sampling frequency of the measured baseband signal (typically 1.25 times the analysis bandwidth), the sampling frequency is also limited. When higher time resolution is required, the sampling interval needs to be reduced by increasing the sampling frequency. However, under low carrier frequency conditions, the increase in sampling frequency is constrained by the analysis bandwidth limitation, making it impossible to further improve the time resolution.

[0016] The core characteristic of CPFSK signals lies in the continuity of their phase. Unlike ordinary FSK signals generated using independent oscillators, CPFSK maintains phase continuity at symbol transition times; that is, the phase at the end of the previous symbol is equal to the phase at the beginning of the next symbol. This constraint makes the phase of a CPFSK signal a continuous function of time, and its instantaneous frequency (the derivative of the phase with respect to time) also exhibits a continuous variation characteristic.

[0017] It is precisely because of this phase continuity that the instantaneous frequency of the CPFSK signal transitions continuously between two frequency offset values ​​as the symbol changes, forming an observable and analyzable absolute frequency change curve. By analyzing the frequency variation over time on this curve, the actual length of each symbol interval can be deduced.

[0018] Therefore, to solve the aforementioned technical problems, this application provides a novel measurement mechanism: using the waveform of the absolute frequency of the modulated signal changing with the symbol to analyze the instantaneous symbol interval length. By capturing the absolute frequency waveform of the modulated signal, determining the symbol boundary based on the frequency jump, and calculating the actual length of each symbol interval, accurate measurement of the instantaneous symbol interval length is achieved. Furthermore, the demodulation analysis center carrier frequency of the vector signal analyzer is shifted up to the target frequency point (rather than being consistent with the signal carrier frequency). This increases the maximum analysis bandwidth to twice the target frequency. By increasing the analysis bandwidth, the baseband analysis sampling frequency is increased, and the time resolution interval of the baseband signal is reduced, thereby improving the accuracy of CPFSK symbol interval length measurement.

[0019] Alternatively, the following provides a possible implementation of a method for measuring the symbol interval length of a low carrier frequency CPFSK signal. Specifically, Figure 1 This is a flowchart illustrating a method for measuring the symbol interval length of a low carrier frequency CPFSK signal according to an embodiment of the present invention. (See attached diagram.) Figure 1 The process includes: Step 100: Receive the digital intermediate frequency signal.

[0020] Optionally, the digital intermediate frequency signal is the digital intermediate frequency signal of the CPFSK signal under test. The CPFSK signal under test can be a 2FSK signal with a carrier frequency of 5MHz, a symbol rate of 0.5MHz, a modulation frequency offset of 0.25MHz, and modulation data of an alternating sequence of 10101010.

[0021] In one possible implementation, the measured CPFSK signal is received by the RF receiving module of a vector signal analyzer, and then a digital intermediate frequency signal is obtained after down-conversion and analog-to-digital conversion.

[0022] Step 101: Demodulate the digital intermediate frequency signal using IQ to obtain the IQ signal.

[0023] Optionally, the digitized intermediate frequency (IF) signal is decomposed into an in-phase component (I-channel) and a quadrature component (Q-channel), with a 90-degree phase difference between the two signals. The IF signal is then converted into a baseband complex signal form via quadrature demodulation. This I / Q signal can be represented as... In the form of, It is the imaginary unit.

[0024] Step 102: Calculate the additional phase of the measured signal based on the IQ signal, and obtain the modulation absolute frequency curve based on the phase change.

[0025] Optionally, the instantaneous phase is calculated based on vector operations of the IQ signal. In the formula, atan2 is the arctangent of the four elements, and then phase expansion is performed to obtain... The instantaneous frequency is the derivative of the expanded instantaneous phase with respect to time divided by... ,Right now The aforementioned additional phase refers to the instantaneous phase of this expansion.

[0026] Optionally, a waveform curve showing the change of the absolute modulation frequency with the symbol is generated based on the instantaneous frequency. This curve directly reflects the frequency jump characteristics of the CPFSK signal during symbol switching.

[0027] Optionally, in one example, the data "1" corresponds to a frequency offset of 250 kHz above the carrier frequency, and the data "0" corresponds to a frequency offset of 250 kHz below the carrier frequency.

[0028] Step 103: Determine the start and end points of the symbol based on the waveform midpoint of the modulation absolute frequency curve, and calculate the symbol interval length measurement result based on the sampling interval count.

[0029] Specifically, the processor first calculates the average of the maximum and minimum values ​​of the modulation absolute frequency curve as the waveform determination threshold, i.e., the waveform median value.

[0030] Optionally, in one example, the frequency offset result ranges from -250kHz to +250kHz, and the calculated waveform median value is 0kHz. The processor determines the sign boundary based on the comparison between the curve value and the waveform median value: when the measurement sign is "1", the starting point is the point where the curve value is lower than the waveform median value, and the ending point is the point where the curve value first exceeds the waveform median value; when the measurement sign is "0", the starting point is the point where the curve value is higher than the waveform median value, and the ending point is the point where the curve value first falls below the waveform median value.

[0031] After determining the start and end points, the total continuous symbol interval length is obtained by multiplying the number of sampling intervals between the two points by the sampling interval time. This total continuous symbol interval length is then divided by the number of symbols to obtain the measurement result of the symbol interval length for a single symbol. In one example, the sampling rate is 8MHz (16 times the symbol rate), the sampling interval time is 0.125μs, the number of sampling intervals between the start and end points is 16, and the number of symbols is 1. The calculated single symbol interval length is 2μs, or 1 symbol interval length.

[0032] Step 104: When the carrier frequency of the CPFSK signal under test is lower than the preset threshold, the processor will shift the center frequency of the demodulation analysis from the carrier frequency to the target frequency to increase the analysis bandwidth.

[0033] It should be noted that when the carrier frequency is low, the analysis bandwidth of conventional vector signal analyzers is limited by the inability to cross zero frequency (DC), and the maximum usable bandwidth cannot exceed twice the carrier frequency. This results in a limited sampling rate, which in turn limits the time resolution of symbol interval length measurement, making it difficult to meet the requirements of high-precision measurement. Therefore, this application provides an offset mechanism to overcome the above problems.

[0034] Optionally, it can be determined whether the carrier frequency of the CPFSK signal under test meets a preset offset condition. In one example, the preset threshold can be set to half of the required analysis bandwidth, i.e., the target frequency is half of the required analysis bandwidth. When the carrier frequency of the CPFSK signal under test is 5MHz, and the required analysis bandwidth is 16MHz (sampling rate 32 times symbol rate), since half of 16MHz is 8MHz, which is greater than the carrier frequency of 5MHz, the offset condition is met.

[0035] When the offset condition is met, the center frequency of the demodulation analysis is set to half of the analysis bandwidth. In this example, the analysis bandwidth is 16MHz, so the center frequency is set to 8MHz. Thus, the demodulation process of the vector signal analyzer shifts the signal spectrum to a center of 8MHz, expanding the maximum usable analysis bandwidth to 16MHz. Compared to the previous offset where the maximum usable analysis bandwidth was only 10MHz when centered at 5MHz, the analysis bandwidth has increased by 60%, correspondingly increasing the sampling rate from 16 times the symbol rate to 32 times the symbol rate, and the symbol interval resolution from 0.0625 standard symbol intervals to 0.03125 standard symbol intervals.

[0036] The symbol interval length measurement method for low carrier frequency CPFSK signals provided in this embodiment obtains additional phase information through IQ demodulation and generates a modulation absolute frequency curve. It then uses the waveform midpoint to accurately determine the start and end points of the symbol interval, achieving instantaneous symbol interval length measurement. Secondly, when the carrier frequency is below a preset threshold, the demodulation center frequency is shifted from the carrier frequency to the target frequency, expanding the maximum analysis bandwidth to twice that of the shifted center frequency. This overcomes the limitation of twice the carrier frequency bandwidth, improving the sampling rate and time resolution. Therefore, high-resolution symbol interval length measurement results can still be obtained under low carrier frequency conditions.

[0037] Optionally, the following provides a possible implementation of the rule for determining the start and end points of symbols to improve measurement accuracy. Specifically, in Figure 1 On this basis, Figure 2 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 2 Step 103 includes: Step 103-1: Calculate the average of the maximum and minimum values ​​of the modulation absolute frequency curve, and use it as the waveform median value.

[0038] Optionally, all sampling points in the modulation absolute frequency curve are traversed to find the maximum and minimum values ​​of the frequency offset result, and the arithmetic mean of the two is calculated as the waveform median.

[0039] Symbol position is the symbol coordinate axis information data in the waveform where the modulation frequency offset changes with the symbol, that is, the position of the measurement point within the symbol, which is the result of multiplying the sequence number by the symbol resolution. For example, in one example, the data extracted in Table 1 starts from the first symbol, which is the first measurement point. Symbol position is the symbol-related time information displayed by the vector signal analyzer. Taking the data in Table 1 as an example, the frequency offset result ranges approximately from -250kHz to 250kHz, and the calculated waveform midpoint is approximately 0kHz, which serves as the reference threshold for subsequent symbol determination.

[0040] Table 1: Measurement results of modulation frequency offset as a function of sign in absolute frequency waveform Fd (sampling rate 8MHz)

[0041] The expression for the intermediate value of the waveform is as follows: in, The intermediate value of the absolute frequency curve waveform Fd is used to modulate the waveform. To modulate the maximum value of the absolute frequency curve waveform Fd, The minimum value of the absolute frequency curve waveform Fd.

[0042] Optionally, Figure 3 A schematic diagram of a modulation absolute frequency curve provided in an embodiment of the present invention, see below. Figure 3 The horizontal axis (sym) represents the symbol position, measured in symbol periods (one standard symbol interval). It ranges from 1.000 to 3.750, spanning nearly three symbol periods. The vertical axis (kHz) represents the frequency offset, i.e., the deviation of the instantaneous frequency relative to the carrier frequency (5MHz).

[0043] for Figure 3 The modulation absolute frequency curve shown has the following waveform characteristics: around +250kHz corresponds to modulation data "1"; around -250kHz corresponds to modulation data "0"; the middle sloping transition band corresponds to the core characteristic of CPFSK, "phase continuity". Ordinary FSK has an instantaneous frequency jump, while CPFSK has a continuous frequency transition between two symbols, so you can see that smooth sloping line instead of a vertical, impulsive step.

[0044] Therefore, in Figure 3 In the example shown, the carrier frequency of the CPFSK signal under test is 5MHz, the symbol rate is 0.5MHz, and the frequency offset is ±250kHz. IQ demodulation is performed on this signal, and the modulation absolute frequency curve Fd is generated, as shown in the attached figure. Figure 3 As shown in the curve, data "1" corresponds to a +250kHz frequency offset plateau, and data "0" corresponds to a -250kHz frequency offset plateau. The sign transition is marked by a continuous sloping line, reflecting the continuous phase characteristics of CPFSK.

[0045] The average of the maximum (+250kHz) and minimum (-250kHz) values ​​of the Fd waveform is calculated, yielding an approximate midpoint of 0kHz. When a symbol "1" is identified, the scan begins from a point below 0kHz on the curve, with the first sampling point exceeding 0kHz as the starting point and the first sampling point falling back below 0kHz as the ending point. There are 16 sampling intervals (sampling rate 8MHz) between the starting and ending points, corresponding to a duration of 2μs. After dividing by the standard symbol interval number and rounding, the number of symbols is confirmed to be 1, therefore the length of a single symbol interval is 2μs, or one symbol period. Thus, the symbol boundary can be accurately determined using the midpoint of the waveform, achieving high-resolution measurement of the instantaneous symbol interval length.

[0046] Step 103-2: When the measurement symbol is 1, start from the point where the curve value is lower than the waveform midpoint, take the point where it first exceeds the waveform midpoint as the starting point, and take the point where it first falls below the waveform midpoint as the ending point.

[0047] Optionally, the measurement symbol "1" corresponds to a CPFSK signal (frequency f1) that is 250 kHz higher than the carrier frequency (the same as the center frequency of the vector signal analyzer, 5 MHz), and the measurement symbol "0" corresponds to a CPFSK signal (frequency f2) that is 250 kHz lower than the carrier frequency.

[0048] Step 103-3: When the measurement sign is 0, start from the point where the curve value is higher than the waveform midpoint, take the first point where it is lower than the waveform midpoint as the starting point, and take the first point where it is higher than the waveform midpoint as the ending point.

[0049] Optionally, specifically, the determination logic for the measurement symbol "0" is the opposite of that for the measurement symbol "1". The scan begins in the stable region before the boundary of the measurement symbol. When the curve value is detected to fall below the waveform midpoint for the first time from a state higher than the waveform midpoint, it is determined as the starting point of the symbol "0". The scan continues, and when the curve value is detected to rise above the waveform midpoint for the first time from a state lower than the waveform midpoint, it is determined as the ending point of the symbol "0".

[0050] Step 103-4: Multiply the number of sampling intervals between the start point and the end point by the sampling interval time to obtain the total continuous symbol interval length, and then divide by the number of symbols to obtain the symbol interval length measurement result of a single symbol.

[0051] Optionally, the starting point of the measurement symbol "1" is analyzed according to the algorithm. Starting from the first point Fd1, it is compared with the middle value of the waveform. When the first value is greater than the middle value of the waveform, it is the starting point. When the 17th point Fd2 meets the requirements, it is the starting point. Then, when the first value is less than the middle value of the waveform, it is the ending point. When the 33rd point Fd18 meets the requirements, it is the ending point.

[0052] Furthermore, the number of sampling intervals for the measurement symbol "1" between point 17 and point 33 is calculated using the following formula, with an interval of 16.

[0053] Where, N TI N represents the number of sampling intervals. STOP N is the end point index. start This is the starting point number.

[0054] Calculate the number of measurement symbols "1" using the following formula: Where, N Sym To measure the number of symbols, SN Sym This represents the interval number of one standard symbol. The standard symbol is the (nominal) symbol interval length of the indicator, a theoretical reference value. It is used to calculate the number of symbols, serving as the divisor. Therefore, the interval number of standard symbols is the number of sampling intervals (theoretical value) corresponding to one nominal symbol interval length.

[0055] As can be seen, when multiple consecutive identical measurement symbols (e.g., three consecutive "1") span the area from the start point to the end point, the total number of intervals in this region is actually the sum of the interval lengths of the multiple measurement symbols. If the number of measurement symbols is not determined, multiple measurement symbols will be incorrectly treated as a single excessively long symbol.

[0056] Therefore, this embodiment may further include: dividing the number of sampling intervals between the start point and the end point by the number of intervals of a single standard symbol, and rounding the calculation result to obtain the number of symbols.

[0057] Therefore, by dividing the total number of intervals by the number of intervals for a single standard symbol and rounding down, the number of measurement symbols contained in this continuous region can be accurately identified.

[0058] Furthermore, the length of the measurement symbol "1" is 16 intervals (symbol interval length resolution, since 1sym = 16 symbol interval length resolutions, this length resolution is 0.0625). The nominal value for the symbol interval length is 0.0625sym. Therefore, the symbol interval length for this symbol "1" is 1sym. If there are multiple symbols, the interval length for each symbol is calculated using the following formula: Where, N TI-Sym The number of sampling intervals for each measurement symbol.

[0059] Optionally, the following provides a possible implementation of the triggering conditions and calculation method for center frequency offset, thereby enabling flexible configuration of analysis parameters according to actual needs. Specifically, in Figure 1 On this basis, Figure 4 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 4 Step 104 includes: Step 104-1: Determine whether the carrier frequency of the CPFSK signal under test meets the preset offset condition.

[0060] Optionally, the relationship between the carrier frequency of the measured CPFSK signal and a preset threshold can be compared.

[0061] In one example, the preset offset condition can be set to a carrier frequency lower than half the required analysis bandwidth. When the carrier frequency is 5MHz and the required analysis bandwidth is 16MHz, because... Therefore, the offset condition is met, and center frequency offset is required.

[0062] Conversely, if the carrier frequency is 20MHz and the required analysis bandwidth is 16MHz, then due to If so, refer to step 104-3. No center frequency offset is required, and the carrier frequency can be directly used as the center frequency for demodulation analysis.

[0063] Step 104-2: When the offset condition is met, the center frequency of the demodulation analysis is set to half of the analysis bandwidth, so that the maximum analysis bandwidth is expanded to twice the center frequency after offset.

[0064] Optionally, the center frequency of the demodulation analysis Set to half of the analysis bandwidth BW, i.e. .

[0065] Optionally, in one example, if the analysis bandwidth is 16MHz, then the center frequency is set to 8MHz. In this way, the demodulation process shifts the signal spectrum to a center of 8MHz, with an RF analysis bandwidth of 16MHz (from 0Hz to 16MHz) and a baseband analysis bandwidth of 8MHz (from 0Hz to 8MHz), ensuring the signal is not filtered out by a low-pass filter.

[0066] Therefore, compared to the previous method where the maximum analysis bandwidth was only 10MHz when centered at 5MHz (limited by the inability to cross the zero frequency), the analysis bandwidth has been increased by 60%, and the corresponding sampling rate can be increased from 16 times the symbol rate to 32 times the symbol rate. The symbol interval length resolution has also been increased from 0.0625 standard symbol interval lengths to 0.03125 standard symbol interval lengths.

[0067] For example, Figure 5 This is a schematic diagram illustrating an increase in maximum analysis bandwidth provided in an embodiment of the present invention. (See attached diagram.) Figure 5 , where f sc It is the carrier frequency of the FSK signal, f c-n It is the center frequency of the demodulation analysis of the vector signal analyzer.

[0068] In existing technologies, the center frequency of demodulation analysis is related to the signal carrier frequency f. sc Consistent, at this time the RF analysis bandwidth is f sc It expands symmetrically to both sides of the center. However, since the analysis bandwidth cannot cross the 0-point frequency (DC), the maximum analysis bandwidth is limited to 2. f sc .like Figure 5 As shown in "RF Analysis Bandwidth (Before Offset)", when f sc At lower speeds (e.g., 5MHz), the available bandwidth is only 10MHz, which limits the baseband analysis bandwidth and prevents the sampling rate from being increased.

[0069] To solve the above problem, the center frequency of the demodulation analysis is shifted from the carrier frequency to the target frequency f. c-n ,Right now Figure 5 The RF analysis bandwidth shown is (after offset), and the center frequency shifts upward to f after the offset. c-n At this point, the maximum available analysis bandwidth is increased to 2. f c-n .

[0070] This embodiment, through explicit offset condition judgment and center frequency calculation rules, can flexibly configure analysis parameters according to actual needs, effectively expand the analysis bandwidth in low carrier frequency scenarios, and significantly improve the applicability and resolution of the measurement system.

[0071] Optionally, in order to improve measurement accuracy by utilizing the increased analysis bandwidth, and by increasing the sampling rate to reduce the symbol interval length resolution, this application also provides a mechanism for increasing the sampling rate. Figure 1 On this basis, Figure 6 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 6 It also includes: Step 105: Based on the increased analysis bandwidth, the sampling rate will be increased accordingly to improve the resolution of the symbol interval length measurement results.

[0072] Optionally, the sampling rate is directly related to the analysis bandwidth, typically 1.25 times the analysis bandwidth (considering that the available IQ bandwidth is 0.8 times the analysis bandwidth). When the analysis bandwidth increases from 10MHz to 20MHz, the sampling rate is correspondingly adjusted from 16 times the symbol rate (8MHz) to 32 times the symbol rate (16MHz).

[0073] The sampling interval is determined by the sampling rate and is the reciprocal of the sampling rate. For a sampling rate of 8MHz, the sampling interval is... After the sampling rate was increased to 16MHz, the sampling interval was shortened to The resolution of the symbol interval length is equal to the sampling interval time divided by the nominal value of the symbol interval length. When the symbol interval length is 2 μs, the resolution increases from... The standard symbol interval length (1 / 16 of a symbol) has been increased to Standard symbol interval length (1 / 32 symbol).

[0074] Optionally, in a verification example, by changing the symbol rate of the CPFSK signal generator to 484.848485 kHz (about 3% slower than the nominal value of 500 kHz, i.e., increasing by 1 / 32 of the nominal symbol interval length), the improved resolution can accurately identify 33 resolution intervals (corresponding to 1.03125 standard symbol interval lengths), verifying the effect of the resolution improvement.

[0075] To better verify the improved measurement resolution of symbol interval length based on the above mechanism, a verification example is provided below. Data "1" corresponds to a CPFSK signal (frequency f1) 2.75MHz lower than the center frequency (8MHz) of the vector signal analyzer, while data "0" corresponds to a CPFSK signal (frequency f2) 3.25MHz lower than the center frequency. The absolute frequency varies with the symbol measurement results (sampling rate 16MHz) as shown in Table 2 below. Applying the same symbol interval length determination rule, the approximate value of the waveform's median is calculated to be -3MHz. The calculated length of symbol "1" is 1sym, but the length resolution is only 0.03125. The nominal value of the symbol interval length is 0.03125sym. Therefore, the measurement resolution of the symbol interval length is improved.

[0076] Table 2. Absolute frequency as a function of symbol measurement (sampling rate 16MHz)

[0077] By changing the symbol rate of the CPFSK signal generator to 484.848485 kHz, i.e., changing the symbol interval length (increasing it by 1 / 32 of the nominal symbol interval length, i.e., increasing the resolution by 0.03125 sym), the improved resolution of the symbol interval length measurement was further verified. The demodulation parameters of the vector signal analyzer remained unchanged, and the measurement results are shown in Table 3 below: Table 3. Absolute frequency as a function of symbol measurement (sampling rate 16MHz, symbol rate 484.848485kHz)

[0078] According to the symbol interval length determination rule, point 2 is the starting point and point 35 is the ending point, with a total of 33 resolution intervals, which is consistent with the symbol interval length of the actual CPFSK signal. Therefore, the new resolution of 0.03125sym is verified.

[0079] This embodiment fully utilizes the increased analysis bandwidth by synchronously adjusting the sampling rate, further reducing the sampling interval time, thereby improving the resolution of symbol interval length measurement. This enables the system to detect more subtle changes in symbol interval length, improving measurement accuracy and sensitivity.

[0080] Optionally, for the specific CPFSK signal type 2FSK, step 102 above can be implemented in one possible way. Figure 1 On this basis, Figure 7 A flowchart illustrating another method for measuring the symbol interval length of a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 7 Step 102 includes: Step 102-1: When the measured CPFSK signal is a 2FSK signal, calculate the instantaneous frequency offset based on the vector operation of the IQ signal.

[0081] Specifically, the 2FSK signal uses two different frequencies ( and The cosine signals of the I / Q signals represent data "1" and data "0" respectively, and the signal phase changes continuously within one symbol period. The analysis module calculates the instantaneous phase based on the I / Q signals. ,in For in-phase components, These are orthogonal components. The instantaneous frequency offset is the derivative of the expanded instantaneous phase with respect to time divided by... ,Right now .

[0082] Optionally, in one example, when the transmitted data is "1", the instantaneous frequency offset is close to +250kHz (above the carrier frequency); when the transmitted data is "0", the instantaneous frequency offset is close to -250kHz (below the carrier frequency).

[0083] Step 102-2: Generate the modulation absolute frequency curve based on the instantaneous frequency deviation.

[0084] Specifically, a curve is generated by plotting the symbol position on the x-axis and the instantaneous frequency offset on the y-axis to show the absolute frequency changing with the symbol. This curve forms a waveform that jumps between positive and negative frequency offsets, clearly reflecting the symbol switching moments of the 2FSK modulated data.

[0085] In one example, when the center frequency shifts to 8MHz, data "1" corresponds to a CPFSK signal with a center frequency of 2.75MHz lower than the center frequency, and data "0" corresponds to a CPFSK signal with a center frequency of 3.25MHz lower than the center frequency. The modulation absolute frequency curve jumps between -2.75MHz and -3.25MHz.

[0086] This embodiment provides specific phase and frequency offset calculation methods for 2FSK signal types, making the scheme clearly operable in typical application scenarios, ensuring the accuracy of signal demodulation and frequency extraction, and providing a reliable data foundation for subsequent symbol interval length measurement.

[0087] Continuing with the example above, the data "1" corresponds to a CPFSK signal (frequency f1) 2.75MHz lower than the center frequency (8MHz) of the vector signal analyzer, while the data "0" corresponds to a CPFSK signal (frequency f2) 3.25MHz lower than the center frequency. The absolute frequency varies with the symbol measurement results (sampling rate 16MHz) as shown in Table 2. Applying the same symbol interval length determination rule, the approximate value of the waveform's median is calculated to be -3MHz. The calculated length of the symbol "1" is 1sym, but the length resolution is 0.03125. The nominal value of the symbol interval length is 0.03125sym. Therefore, the measurement resolution of the symbol interval length is improved.

[0088] Optionally, a symbol spacing length measurement device for low carrier frequency CPFSK signals is provided below, used to perform the steps and corresponding technical effects of the above examples. Specifically, Figure 8 A schematic diagram of a symbol interval length measurement device for a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 8 The symbol interval length measuring device 20 for the low carrier frequency CPFSK signal includes: a receiving module 200, a demodulation module 201, a frequency curve generation module 202, a symbol boundary determination module 203, and a center frequency control module 204.

[0089] The receiving module 200 is used to receive digital intermediate frequency signals.

[0090] The demodulation module 201 is used to perform IQ demodulation on the digital intermediate frequency signal to obtain the IQ signal.

[0091] The frequency curve generation module 202 is used to calculate the additional phase of the measured signal based on the IQ signal and obtain the modulation absolute frequency curve based on the phase change.

[0092] The symbol boundary determination module 203 is used to determine the start and end points of the symbol based on the waveform midpoint of the modulation absolute frequency curve, and to calculate the symbol interval length measurement result based on the sampling interval count.

[0093] The center frequency control module 204 is used to shift the center frequency of demodulation analysis from the carrier frequency to the target frequency when the carrier frequency of the CPFSK signal under test is lower than a preset threshold, so as to increase the analysis bandwidth.

[0094] Optionally, the symbol boundary determination module 203 is specifically used to calculate the average of the maximum and minimum values ​​of the modulation absolute frequency curve as the waveform intermediate value. When the measured symbol is 1, it starts from the point where the curve value is lower than the waveform intermediate value, takes the point where it first exceeds the waveform intermediate value as the starting point, and takes the point where it first falls below the waveform intermediate value as the ending point. When the measured symbol is 0, it starts from the point where the curve value is higher than the waveform intermediate value, takes the point where it first falls below the waveform intermediate value as the starting point, and takes the point where it first exceeds the waveform intermediate value as the ending point. The total continuous symbol interval length is obtained by multiplying the number of sampling intervals between the starting point and the ending point by the sampling interval time, and then divided by the number of symbols to obtain the symbol interval length measurement result of a single symbol.

[0095] Optionally, the symbol boundary determination module 203 is also used to divide the number of sampling intervals between the start point and the end point by the number of intervals of a single standard symbol, and to perform a rounding operation on the calculation result to obtain the number of symbols.

[0096] Optionally, the center frequency control module 204 is specifically used to determine whether the carrier frequency of the CPFSK signal under test meets the preset offset condition. When the offset condition is met, the center frequency of the demodulation analysis is set to half of the analysis bandwidth, so that the maximum analysis bandwidth is expanded to twice the center frequency after offset.

[0097] Optionally, the center frequency control module 204 is specifically used to increase the sampling rate according to the increased analysis bandwidth in order to improve the resolution of the symbol interval length measurement results.

[0098] Optionally, the frequency curve generation module 202 is specifically used to calculate the instantaneous frequency offset based on the vector operation of the IQ signal when the measured CPFSK signal is a 2FSK signal, and generate the modulation absolute frequency curve based on the instantaneous frequency offset.

[0099] Optionally, in specific implementation examples, the analysis instance can typically be deployed on a vector signal analyzer with a Vector Modulation Analysis Option (VSA) as the measurement hardware. The following provides an implementation scheme for a symbol spacing length measurement device for low carrier frequency CPFSK signals based on measurement hardware and analysis software.

[0100] Specifically, Figure 9 A schematic diagram illustrating a possible implementation of a symbol interval length measurement device for a low carrier frequency CPFSK signal provided in an embodiment of the present invention is shown below. Figure 9 The symbol interval length measuring device for a low carrier frequency CPFSK signal can be composed of a vector signal analyzer 2A and a terminal 2B with test software deployed.

[0101] The vector signal analyzer 2A may include: a receiving module 200, a demodulation module 201, and a frequency curve generation module 202.

[0102] Terminal 2B may include a symbol boundary determination module 203 and a center frequency control module 204.

[0103] Alternatively, the symbol boundary determination module 203 can also be deployed on the vector signal analyzer 2A.

[0104] Alternatively, for this vector signal analyzer 2A, the following is a setup example: 1) Use a vector signal generator to output a 2FSK signal (without channel filter) with a carrier frequency of 5MHz, a symbol rate of 0.5MHz and a modulation frequency offset of 0.25MHz, and the modulation data is 10101010….

[0105] 2) On the vector signal analyzer, select the vector signal analysis mode (VSA) and set the demodulation analysis center frequency to 5MHz, the modulation type to 2FSK, the symbol rate to 0.5MHz, the modulation frequency offset to 0.25MHz, no transmit filter, the analysis signal source to capture buffer, and the data result type to absolute frequency.

[0106] 3) The sampling rate of the vector signal analyzer is 16. Symbol rate, i.e., 8MHz (maximum analysis bandwidth without errors).

[0107] 4) Perform a single measurement of the vector signal on the vector signal analyzer.

[0108] Correspondingly, the following is an example of reading data and calculating the interval length for symbol analysis: A frequency offset measurement value was read from the waveform results of modulation frequency offset changing with symbol in the absolute frequency data results, as shown in Table 1 above. The frequency offset result is the absolute frequency of the signal relative to the center frequency of the vector signal analyzer. Data "1" corresponds to a CPFSK signal (frequency f1) 250kHz higher than the carrier frequency (the same as the center frequency of the vector signal analyzer, 5MHz), while data "0" corresponds to a CPFSK signal (frequency f2) 250kHz lower than the carrier frequency. The symbol position is the symbol coordinate axis information data in the waveform of modulation frequency offset changing with symbol, that is, the position of the measurement point within the symbol, which is the length corresponding to the sequence number multiplied by the sampling interval time. The data extracted in Table 1 starts from the first symbol, representing the first measurement point. The symbol position is the time information related to the symbol displayed by the vector signal analyzer.

[0109] Accordingly, this specification also provides an apparatus that can be applied to computer devices, such as servers or terminal devices. The apparatus can be implemented in software, hardware, or a combination of both. Taking software implementation as an example, as a logically defined apparatus, it is formed by a processor reading the corresponding computer program instructions from non-volatile memory into memory and executing them. From a hardware perspective, such as... Figure 10 As shown, Figure 10 This is a schematic diagram of an electronic device provided in an embodiment of the present invention, and a hardware structure diagram of a computer device in which the device provided in this specification is located, except... Figure 10 In addition to the processor 310, memory 330, network interface 320, and non-volatile memory 340 shown, the server or electronic device where the device 20 is located in the embodiment may also include other hardware depending on the actual function of the computer device, which will not be described in detail here.

[0110] The specific implementation process of the functions and roles of each module in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0111] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative, and the modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of the solution in this specification according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0112] The foregoing has described exemplary embodiments of this specification. It should be understood that in some cases, the modules described in this specification may be divided in a manner different from that in the embodiments, and the described actions or steps may be performed in a different order than that in the embodiments, while still achieving the desired result. Furthermore, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0113] The above are merely preferred embodiments of this specification and are not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification shall be included within the scope of protection of this specification.

Claims

1. A method for measuring the symbol interval length of a low carrier frequency CPFSK signal, characterized in that, include: Receives digital intermediate frequency signals; The digital intermediate frequency signal is demodulated using IQ modulation to obtain the IQ signal; The additional phase of the measured signal is calculated based on the IQ signal, and the modulation absolute frequency curve is obtained based on the phase change; The start and end points of the symbol are determined based on the waveform midpoint of the modulation absolute frequency curve, and the symbol interval length measurement result is obtained based on the sampling interval count. When the carrier frequency of the CPFSK signal under test is lower than a preset threshold, the center frequency of the demodulation analysis is shifted from the carrier frequency to the target frequency to increase the analysis bandwidth.

2. The method according to claim 1, characterized in that, The steps of determining the start and end points of a symbol based on the waveform midpoint of the modulation absolute frequency curve, and calculating the symbol interval length measurement result based on the sampling interval count, include: Calculate the average of the maximum and minimum values ​​of the modulation absolute frequency curve, and use it as the waveform median value; When the measurement symbol is 1, the starting point is the point where the curve value is lower than the middle value of the waveform, the starting point is the point where the value first exceeds the middle value of the waveform, and the ending point is the point where the value first falls below the middle value of the waveform. When the measurement sign is 0, the starting point is the point where the curve value is higher than the midpoint of the waveform, and the ending point is the point where the first value is lower than the midpoint of the waveform. Multiply the number of sampling intervals between the start and end points by the sampling interval time to obtain the total continuous symbol interval length, and then divide by the number of symbols to obtain the symbol interval length measurement result of a single symbol.

3. The method according to claim 2, characterized in that, Also includes: The number of sampling intervals between the start and end points is divided by the number of intervals for a single standard symbol, and the result is rounded down to obtain the number of symbols.

4. The method according to claim 1, characterized in that, The step of shifting the center frequency of the demodulation analysis from the carrier frequency to the target frequency when the carrier frequency of the measured CPFSK signal is lower than a preset threshold includes: Determine whether the carrier frequency of the tested CPFSK signal meets the preset offset condition; When the offset condition is met, the center frequency of the demodulation analysis is set to half of the analysis bandwidth, so that the maximum analysis bandwidth is expanded to twice the center frequency after offset.

5. The method according to claim 1, characterized in that, After shifting the center frequency of the demodulation analysis from the carrier frequency to the target frequency when the carrier frequency of the CPFSK signal under test is lower than a preset threshold, the method further includes: The sampling rate will be increased accordingly based on the increased analysis bandwidth to improve the resolution of the symbol interval length measurement results.

6. The method according to claim 4, characterized in that, The steps of calculating the additional phase of the measured signal based on the IQ signal and obtaining the modulation absolute frequency curve based on the phase change include: When the measured CPFSK signal is a 2FSK signal, the analysis module calculates the instantaneous frequency offset based on the vector operation of the IQ signal; The modulation absolute frequency curve is generated based on the instantaneous frequency deviation.

7. A device for measuring the symbol interval length of a low carrier frequency CPFSK signal, characterized in that, The device includes: The receiving module is used to receive digital intermediate frequency signals; The demodulation module is used to perform IQ demodulation on the digitized intermediate frequency signal to obtain the IQ signal; The frequency curve generation module is used to calculate the additional phase of the measured signal based on the IQ signal, and obtain the modulation absolute frequency curve based on the phase change; The symbol boundary determination module is used to determine the start and end points of the symbol based on the waveform midpoint of the modulation absolute frequency curve, and to calculate the symbol interval length measurement result based on the sampling interval count. The center frequency control module is used to shift the center frequency of demodulation analysis from the carrier frequency to the target frequency when the carrier frequency of the CPFSK signal under test is lower than a preset threshold, so as to increase the analysis bandwidth.

8. The apparatus according to claim 7, characterized in that, The symbol boundary determination module is specifically used to calculate the average of the maximum and minimum values ​​of the modulation absolute frequency curve as the waveform median value. When the measured symbol is 1, it starts from the point where the curve value is lower than the waveform median value, takes the first point where it is higher than the waveform median value as the starting point, and takes the first point where it is lower than the waveform median value as the ending point. When the measured symbol is 0, it starts from the point where the curve value is higher than the waveform median value, takes the first point where it is lower than the waveform median value as the starting point, and takes the first point where it is higher than the waveform median value as the ending point. The number of sampling intervals between the starting point and the ending point is multiplied by the sampling interval time to obtain the total continuous symbol interval length, and then divided by the number of symbols to obtain the symbol interval length measurement result of a single symbol.

9. The apparatus according to claim 8, characterized in that, The symbol boundary determination module is further configured to divide the number of sampling intervals between the start point and the end point by the number of intervals of a single standard symbol, and to perform a rounding operation on the calculation result to obtain the number of symbols.

10. An electronic device, characterized in that, include: Memory, used to store one or more programs; processor; When the one or more programs are executed by the processor, the method as described in any one of claims 1-6 is implemented.

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