A high-speed frequency hopping signal acquisition apparatus and method

Abstract

The application provides a high-speed frequency hopping signal capturing device and method, which comprises a radio frequency channel processing unit, a wideband frequency division unit and a first switch switching unit connected in sequence, the first switch switching unit is connected with a frequency counting frequency measurement unit and a wideband demodulation frequency measurement unit, the frequency counting frequency measurement circuit unit and the wideband demodulation frequency measurement circuit unit are connected to a second switch switching unit, the second switch switching unit is connected with a wideband high-speed frequency hopping signal capturing processing unit; the radio frequency channel processing unit is used for measuring the power of the measured radio frequency signal and filtering the stray outside the bandwidth; the wideband frequency division unit is used for frequency dividing the measured radio frequency signal to obtain a wideband intermediate frequency signal; the application adds the wideband demodulation frequency measurement circuit unit, improves the time resolution to several ns, and only needs a low-cost sampling rate ADC and an easily programmable logic device to realize, so that the design difficulty and complexity of the circuit and timing are greatly simplified.

Description

Technical Field

[0001] This invention relates to the field of time and frequency measurement technology, and specifically to a high-speed frequency hopping signal acquisition device and method. Background Technology

[0002] In modulation domain analysis, the ability to capture high-speed frequency-hopping signals is affected by the sampling frequency. If a broadband FM signal experiences instantaneous frequency changes, a higher sampling rate is required to identify these changes. Since modulation domain analysis measures the frequency change of the input signal over time, time resolution is a particularly important and intuitive indicator. The development of communication technology has led to the increasingly widespread use of various frequency modulation combinations, such as linear frequency hopping, frequency agile modulation, pulse modulation, and digital modulation. Therefore, the requirements for capturing and analyzing high-speed frequency-hopping signals are becoming increasingly stringent. To meet these new demands, the minimum time resolution needs to reach several nanoseconds, requiring large bandwidth and high-speed gapless measurement capabilities.

[0003] Existing modulation domain analysis techniques measure the signal under test at high speed and continuously with zero idle time, and achieve precise measurement of gate time and pulse count through counting and interpolation to accurately characterize the frequency transient characteristics of the signal under test.

[0004] Currently, frequency counting methods rely on interpolation to ensure measurement accuracy. Interpolation is primarily divided into analog and digital interpolation. Analog interpolation requires expanding the pulse width; to achieve high resolution, the error pulse needs to be amplified multiple times. However, this results in a wider pulse width, extending the acquisition time for frequency-hopping signals and making it impossible to capture fast frequency-hopping signals, while also leading to poor stability. Digital interpolation uses high-response logic converters, eliminating the impact of interpolation measurements on gate time variations and significantly improving measurement accuracy. However, as the frequency change time of frequency-hopping signals decreases, the required gate response time becomes increasingly smaller, making frequency-hopping signal acquisition increasingly difficult. Another method involves splicing together multi-stage counting frequency measurement circuits, infinitely shortening the time interval (i.e., adding a smaller time interval delay to start each counting frequency measurement circuit), and then splicing them together. While this method achieves lower time resolution, the measurement results are averaged, resulting in large frequency conversion time errors and low accuracy for fast frequency-hopping signals.

[0005] Currently, high-performance time-to-digital converters (TDDs) both domestically and internationally are limited by the response capability of logic devices. Their ability to capture frequency-hopping signals with sampling intervals below a few hundred ns deteriorates, leading to inaccurate measurements. To address this issue, this invention proposes a novel high-speed frequency-hopping signal synchronous acquisition method. This method overcomes the limitation of a few hundred ns sampling time resolution, further improving the analysis bandwidth and enabling instantaneous synchronous acquisition of frequency change results for high-speed frequency-hopping signals. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a high-speed frequency hopping signal acquisition device and method, which is rationally designed, overcomes the shortcomings of existing technologies, and has excellent performance.

[0007] To achieve the first objective of the invention, the following technical solution is adopted:

[0008] A high-speed frequency hopping signal acquisition device includes a radio frequency channel processing unit, a broadband frequency division unit, and a first switch switching unit connected in sequence. The first switch switching unit is simultaneously connected to a frequency counting and frequency measurement unit and a broadband demodulation and frequency measurement unit. The frequency counting and frequency measurement circuit unit and the broadband demodulation and frequency measurement circuit unit are jointly connected to a second switch switching unit. The second switch switching unit is connected to a broadband high-speed frequency hopping signal acquisition and processing unit.

[0009] The radio frequency channel processing unit is used to measure the power of the radio frequency signal under test and to filter out bandwidth spurious signals.

[0010] The broadband frequency division unit is used to divide the measured radio frequency signal to obtain a broadband intermediate frequency signal;

[0011] The frequency counting and measurement unit is used to measure the frequency of the frequency hopping signal when the time resolution is x ns, where x takes the value of several hundred.

[0012] The broadband demodulation frequency measurement unit is used to measure the frequency of the frequency hopping signal when the time resolution is y ns, where y < x, and the value of y ranges from a few to several hundred.

[0013] Furthermore, the frequency counting and measurement unit includes an intermediate frequency shaping unit, two counting units, an interpolation measurement unit, a gate generation unit, and a data buffer unit. The intermediate frequency shaping unit is used to shape the broadband intermediate frequency signal into a square wave. The two counting units and the interpolation measurement unit are used to solve gapless large bandwidth modulation domain measurement. The gate generation unit is used to generate the original gate and adjust the gate time according to the measurement needs.

[0014] Furthermore, the counting unit includes a clock counting unit and an event counting unit for event counting and clock counting; the interpolation measurement unit is used to calculate the interpolated measurement values ​​of the leading and trailing edges.

[0015] Furthermore, the broadband demodulation frequency measurement unit includes a low-pass filter unit, an ADC sampling unit, a two-channel frequency measurement and calculation unit, and a data buffer unit.

[0016] To achieve objective 2 of the invention, the following technical solution is adopted:

[0017] A method for capturing high-speed frequency modulation signals, using a high-speed frequency modulation signal capture device as described above, includes the following steps:

[0018] S1. The radio frequency channel processing unit receives the signal under test, measures the power of the signal under test, filters out spurious signals outside the bandwidth, and then transmits it to the broadband frequency division unit.

[0019] S2. The broadband frequency division unit divides the processed signal under test into frequencies, reducing the signal within the bandwidth range to the bandwidth of the frequency measurement unit, thus obtaining a broadband intermediate frequency signal.

[0020] S3. If the time resolution is x ns, the first switching unit allows the broadband intermediate frequency signal to enter the frequency counting and measurement unit. The intermediate frequency shaping unit shapes the broadband intermediate frequency signal into a square wave and then drives it to the counting unit and the interpolation measurement unit in two paths. The gate generation unit generates an original gate with a resolution of x ns or more. The counting unit counts and measures the event gate using a standard time base signal. The interpolation measurement unit performs precise time interpolation measurement on the error between the leading edge and trailing edge of the event gate and the time base signal, calculates the frequency value f1, and transmits the frequency value f1 to the data buffer unit.

[0021] If the time resolution is y ns, the first switching unit allows the broadband intermediate frequency signal to enter the broadband demodulation frequency measurement unit. The broadband intermediate frequency signal is first filtered by the low-pass filter unit and then sampled by the ADC sampling unit. In order to ensure gapless large bandwidth measurement and analysis, the gate generation unit generates a ping-pong synchronization signal of less than y ns to control the two-way operation frequency measurement units to measure the frequency f2 and transmit the measured frequency value to the data buffer unit.

[0022] S4. The frequency value f1 or f2 in the data buffer unit is sent to the broadband high-speed frequency modulation signal acquisition unit through the second switching unit.

[0023] Furthermore, the formula for calculating f1 is:

[0024]

[0025] In the formula: f1 is the measurement frequency value; N1 is the event count value; T1 is the time base counting time; ΔT1 and ΔT2 are the interpolated measurement values ​​of the leading and trailing edges.

[0026] Furthermore, the calculation process of f2 is as follows: Frequency measurement is performed on the digital intermediate frequency signal after ADC sampling, reducing the time resolution to a minimum of (2 / sampling rate) s. The phase between two sampling points is obtained using the phase conversion formula of the digital intermediate frequency signal. for:

[0027]

[0028] Among them, s i+1 s i These are the values ​​of two adjacent sampling points;

[0029] The signal frequency f is:

[0030]

[0031] Where t is the sampling time;

[0032] After continuous AD sampling, s is continuously acquired. i+1 s i The continuous instantaneous frequency values ​​are calculated continuously. This is the intermediate frequency after frequency division. The frequency f2 of the measured signal is then calculated as follows:

[0033] f2 = f * N;

[0034] Where N is the frequency division factor.

[0035] The beneficial effects of this invention are:

[0036] 1. A broadband demodulation and frequency measurement circuit unit has been added, which improves the time resolution to a few ns. It can be implemented with only a low-cost sampling rate ADC of hundreds of MHz and easily programmable logic devices, which greatly simplifies the design difficulty and complexity of circuits and timing.

[0037] 2. It combines the advantages of broadband high-speed frequency measurement with the advantages of broadband demodulation frequency measurement, which is very beneficial for capturing high-speed frequency hopping signals and has high working stability and reliability.

[0038] 3. In this invention, the digital intermediate frequency can easily obtain the instantaneous frequency value using the phase-frequency conversion formula, reducing the time resolution to a minimum of (2 / sampling rate) seconds. The switching unit enables the measurement of different time resolutions, thereby achieving synchronous acquisition of broadband frequency hopping signals. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a high-speed frequency hopping signal acquisition device according to the present invention;

[0040] Figure 2 This is a timing diagram of the frequency counting and frequency measurement unit in this invention. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described below with reference to specific examples:

[0042] A high-speed frequency hopping signal acquisition device, such as Figure 1 As shown, it includes a radio frequency channel processing unit, a broadband frequency division unit and a first switching unit connected in sequence. The first switching unit is connected to both a frequency counting and frequency measurement unit and a broadband demodulation and frequency measurement unit. The frequency counting and frequency measurement circuit unit and the broadband demodulation and frequency measurement circuit unit are connected to a second switching unit. The second switching unit is connected to a broadband high-speed frequency hopping signal acquisition and processing unit.

[0043] The RF channel processing unit is used to measure the power of the RF signal under test and to filter out spurious signals outside the bandwidth.

[0044] The broadband frequency divider unit is used to divide the measured radio frequency signal to obtain a broadband intermediate frequency signal. Generally, the intermediate frequency range of the counting frequency measurement circuit is 10MHz to 500MHz. The broadband demodulation frequency measurement circuit is limited by the analysis bandwidth of the ADC, and the intermediate frequency range is DC to 1 / 2 sampling rate. The broadband frequency division of the measured signal adopts a flexible division ratio, which will realize large bandwidth modulation domain analysis.

[0045] The frequency counting and measurement unit is used to measure the frequency of a frequency-hopping signal when the time resolution is greater than 500 ns. The unit includes an intermediate frequency (IF) shaping unit, two counting units, an interpolation measurement unit, a gate generation unit, and a data buffer unit. The IF shaping unit shapes the broadband IF signal into a square wave. The two counting units and the interpolation measurement unit are used to solve gapless, large-bandwidth modulation domain measurements. The gate generation unit generates the initial gate and adjusts the gate time according to measurement needs. The counting unit includes a clock counting unit and an event counting unit for event counting and clock counting, respectively. The interpolation measurement unit calculates the interpolated measurement values ​​for the leading and trailing edges.

[0046] The broadband demodulation frequency measurement unit is used to measure the frequency of frequency-hopping signals when the time resolution is below 500ns. The broadband demodulation frequency measurement unit includes a low-pass filter unit, an ADC sampling unit, two-channel frequency measurement and calculation units, and a data buffer unit. First, the intermediate frequency signal after broadband frequency division is filtered by the low-pass filter unit, and then sampled. To ensure gapless, large-bandwidth measurement and analysis, a ping-pong synchronization signal is generated by a gate generation unit to control the broadband frequency measurement and calculation unit. Then, the frequency value is transmitted to the processing unit through the two-channel data buffer units. This achieves synchronous acquisition of broadband high-speed frequency-hopping signals, with a time resolution of several nanoseconds. Full-range coverage can be achieved through a switching unit.

[0047] A method for capturing high-speed frequency modulation signals, using a high-speed frequency modulation signal capture device as described above, includes the following steps:

[0048] S1. The radio frequency channel processing unit receives the signal under test, measures the power of the signal under test, filters out spurious signals outside the bandwidth, and then transmits it to the broadband frequency division unit.

[0049] S2. The broadband frequency division unit divides the processed signal under test into frequencies, reducing the signal within the bandwidth range to the bandwidth of the frequency measurement unit, thus obtaining a broadband intermediate frequency signal.

[0050] S3. If the time resolution is greater than 500ns, the first switching unit allows the broadband intermediate frequency signal to enter the frequency counting and measurement unit. The intermediate frequency shaping unit shapes the broadband intermediate frequency signal into a square wave and then drives it to the counting unit and the interpolation measurement unit in two paths. The gate generation unit generates an original gate with a resolution greater than 500ns. The counting unit counts and measures the event gate using a standard time base signal. The interpolation measurement unit performs precise time interpolation measurement on the error between the leading edge and trailing edge of the event gate and the time base signal, calculates the frequency value f1, and transmits the frequency value f1 to the data buffer unit.

[0051] If the time resolution is less than 500ns, the first switching unit allows the broadband intermediate frequency signal to enter the broadband demodulation frequency measurement unit. The broadband intermediate frequency signal is first filtered by the low-pass filter unit and then sampled by the ADC sampling unit. In order to ensure gapless large bandwidth measurement and analysis, the gate generation unit generates a ping-pong synchronization signal of less than 500ns to control the two-way operation frequency measurement units to measure the frequency f2 and transmit the measured frequency value to the data buffer unit.

[0052] S4. The frequency value f1 or f2 in the data buffer unit is sent to the broadband high-speed frequency modulation signal acquisition unit through the second switching unit.

[0053] Specifically, such as Figure 2 As shown, the intermediate frequency (IF) signal under test must be capable of high-speed triggering and shaping, and synchronized with the gate. The IF event count N within the time gate after synchronization can eliminate ±1 event error of the tested signal. The event gate is then counted using a standard time base signal to achieve time measurement. Since the standard time base signal and the event gate are not synchronized, there is a ±1 time base error. To improve measurement resolution, precise time interpolation measurement of the error ΔT between the leading and trailing edges of the event gate and the time base signal is required. The measurement results are calculated as follows:

[0054]

[0055] In the formula: f1 is the measurement frequency value; N1 is the event count value; T1 is the time base counting time; ΔT1 and ΔT2 are the interpolated measurement values ​​of the leading and trailing edges;

[0056] The event gate is synchronously counted using a standard time base, and the interpolation time before and after is precisely measured using a digital interpolation method. The frequency value is calculated according to formula (1). The counter method time measurement ensures that the high-resolution time measurement is not affected by the error of ±1 event of the measured signal. The time resolution is determined by the resolution of the precise interpolation time measurement, and is not affected by the frequency of the measured signal. It can always maintain high-precision frequency and time measurement, and thus realize the high-speed gapless capture of the measured frequency hopping signal by using the gate time as the achievable time resolution.

[0057] Specifically, to achieve high time resolution, high sampling rate converters are typically used to reduce the signal analysis time resolution to the nanosecond or millisecond level. Therefore, to solve the problem of capturing wide-bandwidth frequency-hopping signals, this wideband demodulation frequency measurement method can first divide the signal under test into a sufficiently narrowband signal, then perform AD sampling, and finally demodulate and analyze the sampled data to obtain the frequency data. In this way, the acquisition time of wideband frequency-hopping signals can be reduced to the level of AD analysis capability. For example, with a sampling rate of 250MHz, the minimum analysis capability can reach 8ns. This can solve the problem of frequency-hopping acquisition with time resolution in the range of 8ns to several hundred nanoseconds.

[0058] Therefore, to achieve rapid acquisition of frequency-hopping signals in the large bandwidth modulation domain, a combination of frequency counting and broadband demodulation frequency measurement can be used. For time resolutions of several hundred ns (e.g., 500 ns) or higher, the frequency counting method is used to ensure measurement accuracy, measurement speed, and bandwidth. For frequencies below 500ns, wideband demodulation frequency measurement is employed, which uses phase-frequency calculations to obtain a fast demodulation frequency measurement method. Although the accuracy of this method is affected by resolution bandwidth, the ADC sampling rate can generally reach several hundred MHz, with a minimum resolution of several ns, which is very beneficial for measuring the frequency changes of high-speed, short-time frequency-hopping signals. Of course, wideband frequency division can convert a larger bandwidth to a narrower signal, for example, covering the sampling time range from tens of seconds to several ns, but this will increase the difficulty and complexity of data processing and affect the measurement speed. Therefore, the method of combining frequency counting and wideband demodulation frequency measurement can combine the advantages of both methods. For frequencies below 500ns, a wideband demodulation frequency measurement circuit is used for ADC sampling, and the phase information is demodulated to obtain frequency data, with a time resolution covering several ns to 500ns, which is very beneficial for capturing high-speed frequency-hopping signals. For sampling intervals that are not critical and are greater than 500ns, a switching selection counting frequency measurement circuit channel can be used to achieve high-precision modulation domain frequency measurement, fast measurement speed, long gapless measurement time, and a large monitoring range bandwidth.

[0059] The calculation process for f2 is as follows: The frequency of the digital intermediate frequency (IF) signal after ADC sampling is measured, and the time resolution is reduced to a minimum of (2 / sampling rate) s. The phase between two sampling points is obtained using the phase conversion formula for the digital IF signal. for:

[0060]

[0061] Among them, s i+1 s i These are the values ​​of two adjacent sampling points;

[0062] The signal frequency f is:

[0063]

[0064] Where t is the sampling time;

[0065] After continuous AD sampling, s is continuously acquired. i+1 s i The continuous instantaneous frequency values ​​are calculated continuously. This is the intermediate frequency after frequency division. The frequency f2 of the measured signal is then calculated as follows:

[0066] f2 = f * N;

[0067] Where N is the frequency division factor.

[0068] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A high-speed frequency hopping signal acquisition device, characterized in that, It includes a radio frequency channel processing unit, a broadband frequency division unit and a first switch selection unit connected in sequence. The first switch selection unit is connected to both a frequency counting and frequency measurement unit and a broadband demodulation and frequency measurement unit. The frequency counting and frequency measurement unit and the broadband demodulation and frequency measurement unit are connected to a second switch selection unit. The second switch selection unit is connected to a broadband high-speed frequency hopping signal acquisition unit. The radio frequency channel processing unit is configured to measure the power of the radio frequency signal under test and filter out bandwidth spurious signals. The broadband frequency division unit is configured to divide the measured radio frequency signal to obtain a broadband intermediate frequency signal; The frequency counting and measurement unit is configured to measure the frequency of the frequency hopping signal when the time resolution is x ns, where x takes the value of several hundred. The broadband demodulation frequency measurement unit is configured to measure the frequency of the frequency hopping signal when the time resolution is y ns, where y < x, and the value of y ranges from a few to several hundred.

2. The high-speed frequency hopping signal acquisition device according to claim 1, characterized in that, The frequency counting and measurement unit includes an intermediate frequency shaping unit, two counting units, an interpolation measurement unit, a gate generation unit, and a data buffer unit. The intermediate frequency shaping unit is used to shape the broadband intermediate frequency signal into a square wave. The two counting units include a clock counting unit and an event counting unit. The two counting units and the interpolation measurement unit are used to solve gapless large bandwidth modulation domain measurement. The gate generation unit is used to generate the original gate and adjust the gate time according to the measurement needs.

3. The high-speed frequency hopping signal acquisition device according to claim 2, characterized in that, The counting unit includes a clock counting unit and an event counting unit for event counting and clock counting; the interpolation measurement unit is used to calculate the interpolated measurement values ​​of the leading and trailing edges.

4. The high-speed frequency hopping signal acquisition device according to claim 3, characterized in that, The broadband demodulation and frequency measurement unit includes a low-pass filter unit, an ADC sampling unit, a two-channel frequency measurement and calculation unit, and a data buffer unit.

5. A method for acquiring high-speed frequency hopping signals, employing the high-speed frequency hopping signal acquisition device as described in claim 4, characterized in that, Includes the following steps: S1. The radio frequency channel processing unit receives the signal under test, measures the power of the signal under test, filters out spurious signals outside the bandwidth, and then transmits it to the broadband frequency division unit. S2. The broadband frequency division unit divides the processed signal under test into frequencies, reducing the signal within the bandwidth range to the bandwidth of the frequency measurement unit, thus obtaining a broadband intermediate frequency signal. S3. If the time resolution is x ns, the first switch selection unit allows the broadband intermediate frequency signal to enter the frequency counting and measurement unit. The intermediate frequency shaping unit shapes the broadband intermediate frequency signal into a square wave and then drives it to the counting unit and the interpolation measurement unit in two paths. The gate generation unit generates an original gate with a resolution greater than x ns. The counting unit counts and measures the event gate using a standard time base signal. The interpolation measurement unit performs precise time interpolation measurement on the error between the leading and trailing edges of the event gate and the time base signal, and calculates the frequency value. , frequency value Transmitted to the data buffer unit; If the time resolution is y ns, the first switch selection unit allows the broadband intermediate frequency signal to enter the broadband demodulation frequency measurement unit. The broadband intermediate frequency signal is first filtered by the low-pass filter unit, and then sampled by the ADC sampling unit. To ensure gapless, large-bandwidth measurement and analysis, the gate generation unit generates a ping-pong synchronization signal of less than y ns to control the two frequency measurement and calculation units to calculate the frequency value. The measured frequency value is transmitted to the data buffer unit. S4. Transfer the frequency value from the data buffer unit. or The signal is then transmitted to the broadband high-speed frequency hopping signal acquisition unit via the second switch selection unit.

6. The high-speed frequency hopping signal acquisition method according to claim 5, characterized in that, The The calculation formula is: ； In the formula: It measures the frequency value; It is the event count value; It is the time base counting time; , These are interpolated measurements from the leading and trailing edges.

7. A high-speed frequency hopping signal acquisition method according to claim 5, characterized in that, The The calculation process is as follows: The frequency of the digital intermediate frequency (IF) signal after ADC sampling is measured, and the time resolution is reduced to a minimum of 2 / sampling rate (in seconds). The phase between two sampling points is obtained using the phase conversion formula of the digital IF signal. for: ； in, , These are the values ​​of two adjacent sampling points; signal frequency for: ； Where t is the sampling time; After continuous ADC sampling, continuously acquire , The continuous instantaneous frequency values ​​are calculated continuously. This is the intermediate frequency after frequency division. The frequency value of the measured signal is then calculated. for: ； Where N is the frequency division factor.

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