A high-precision frequency measurement method based on a surface acoustic wave filter

Abstract

The application relates to the field of electronic measurement technology, in particular to a high-precision frequency measurement method based on a surface acoustic wave filter, which comprises a D flip-flop circuit, a surface acoustic wave circuit and an FPGA circuit which are electrically connected in sequence. The FPGA circuit generates a gate signal to control the D flip-flop circuit to accurately extract the start and stop pulses of the integer multiple periods of a to-be-measured signal, and a narrow-band signal stretched in time domain is obtained through the surface acoustic wave filter. After high-speed sampling and interpolation of the narrow-band signal through an ADC circuit, autocorrelation operation is performed on the narrow-band signal, and a time interval measurement value, i.e. the integer multiple period value of the to-be-measured signal, is obtained. Finally, the period value of the to-be-measured signal is obtained by combining the counting value of the complete pulse of the to-be-measured signal in the gate time of the FPGA circuit, and the frequency measurement value is obtained through conversion. The application realizes a high-precision and high-stability frequency measurement method based on the time interval measurement method of the surface acoustic wave filter and the multi-period synchronization technology controlled by the FPGA circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic measurement technology, and in particular to a high-precision frequency measurement method based on a surface acoustic wave filter. BACKGROUND

[0002] High-precision time-frequency measurement technology plays a crucial role and has a profound impact in many fields, providing accurate synchronization and clock reference for communication systems, navigation systems, radar systems, and scientific experiments, ensuring stable system performance and accuracy. In addition, high-precision measurement helps improve data transmission efficiency, enhance system anti-interference capability, and promote technological progress and innovative development in related fields.

[0003] Traditionally, the measurement of signal frequency generally relies on the direct counting method of digital frequency meters, which calculates the frequency by counting the number of trigger event periods through a 1-second gate signal. However, this method has inherent limitations: the gate time may not be synchronized with the input signal trigger time, introducing a measurement error of ±1 period. Therefore, the accuracy of frequency measurement using traditional frequency measurement methods is often not high. SUMMARY

[0004] The main purpose of the present application is to overcome the shortcomings of the prior art and provide a high-precision frequency measurement method. The time interval measurement method based on a surface acoustic wave filter combines multi-cycle synchronization technology to solve the technical problem of not being able to effectively achieve high-precision and high-resolution signal frequency measurement in the prior art.

[0005] The technical solution adopted by the present application to achieve its technical purpose is as follows: a high-precision frequency measurement method based on a surface acoustic wave filter, comprising a D flip-flop circuit, a surface acoustic wave circuit, an ADC circuit, and an FPGA circuit connected in sequence;

[0006] The FPGA circuit generates a gate signal to control the D flip-flop circuit to accurately extract the start and stop pulses of an integer multiple of the period of the signal to be measured. The surface acoustic wave circuit obtains a time-domain stretched narrowband signal. The narrowband signal is high-speed sampled and interpolated by the ADC circuit, and then subjected to autocorrelation operation to obtain a time interval measurement value, which is the integer multiple of the period of the signal to be measured.

[0007] Finally, the FPGA circuit counts the number of complete pulses of the signal to be measured within the gate time, and calculates the period value of the signal to be measured to obtain the frequency measurement value.

[0008] Preferably, the FPGA circuit generates a gate signal to control the D flip-flop circuit to accurately extract the start and stop pulses of an integer multiple of the period of the signal to be measured. At the same time, the number of complete pulses within the gate time is counted by the counting method.

[0009] Preferably, the D flip-flop circuit is composed of 1 D flip-flop and 2 differential converters;

[0010] The D flip-flop is synchronized by a gate signal generated by the FPGA circuit, and the differential converter is used for converting differential signals and single-ended signals.

[0011] Preferably, the surface acoustic wave circuit is used for stretching signals in the time domain to obtain narrow-band signals in the frequency domain.

[0012] The surface acoustic wave circuit comprises a surface acoustic wave filter, and the center frequency and time domain width of the narrow-band signal are determined by the center frequency and bandwidth of the surface acoustic wave filter.

[0013] Preferably, the FPGA circuit part performs autocorrelation operation on the signal after high-speed sampling and interpolation of the ADC circuit to obtain an integer multiple period value of the to-be-measured signal , and the period of the to-be-measured signal is obtained by combining the count value n of the complete pulse of the to-be-measured signal in the gate time of the FPGA circuit , and the frequency can be represented as .

[0014] Compared with the prior art, the beneficial effects of the present application are:

[0015] The high-precision frequency measurement method based on the surface acoustic wave filter combines the multi-cycle synchronization technology controlled by the FPGA circuit, and realizes a high-precision and high-stability frequency measurement method. Improvements and enhancements are mainly made in two aspects:

[0016] Firstly, the traditional frequency counting method is improved, such as the multi-cycle synchronization method and the equal-precision frequency measurement technology, which eliminates the ±1 error by keeping synchronization with the measured signal, and improves the measurement precision;

[0017] Secondly, the high-precision time interval measurement technology is used to directly measure the period of the measured signal, and the short time interval in the signal period is accurately captured and measured, such as using the surface acoustic wave filter (SAWF) and the time-amplitude converter (TAC) measurement method, to realize high-precision and high-resolution measurement of the signal frequency. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of the present application.

[0019] Figure 2 is a principle diagram of the D flip-flop circuit in the embodiment of the present application.

[0020] Figure 3 is a general timing diagram of the system in the embodiment of the present application.

[0021] Figure 4 is a schematic diagram of the signal after ADC sampling in an embodiment of the present application.

[0022] Figure 5 is a measurement result of an integer multiple of the period of the signal to be measured in an embodiment of the present application.

[0023] Figure 6 is a measurement result of the period of the signal to be measured in an embodiment of the present application.

[0024] Figure 7 is a measurement result of the frequency of the signal to be measured in an embodiment of the present application. DETAILED DESCRIPTION

[0025] For the purpose of clarity and conciseness, the present application will be described in detail in the following with reference to the accompanying drawings and specific embodiments. It should be noted that these embodiments are only used to illustrate the present application and do not limit the scope thereof. In the description, well-known structures and technologies will not be described in detail to avoid obscuring the core points of the present application.

[0026] In the present application, the terms "fixed to" or "provided on" used to describe the relationship between elements should be understood as including direct fixation or indirect fixation through other elements. Similarly, the term "connected to" should be understood as including direct connection or indirect connection through intermediate connecting elements. The use of these terms does not limit the specific implementation of the present application, but is used to clearly illustrate the relative positional relationship between elements.

[0027] The orientation and position terms used in the description of the present application, such as "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or position relationship shown in the drawings or the conventional orientation or position relationship of the product in use. The use of these terms is intended to simplify the description of the present application and is not intended to limit the described device or element to a particular orientation or to be constructed and operated in a particular orientation. Therefore, the use of these terms should not be understood as limiting the present application. In the description of the present application, "a plurality of" means two or more elements or features, and "several" means one or more elements or features, unless otherwise specifically limited in the context. These definitions help accurately describe the scope and characteristics of the present application, but do not limit the scope of the present application.

[0028] In the present invention, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, including but not limited to fixed, removable, or integral connections, mechanical or electrical connections, direct or indirect connections via a medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms based on specific circumstances. Unless otherwise expressly defined, these interpretations apply.

[0029] Example:

[0030] See also Figure 1-Figure 7 , a high-precision frequency measurement method based on surface acoustic wave filter, specifically including the following parts:

[0031] (1) D flip-flop circuit, which controls the D flip-flop through the gate signal generated by the FPGA circuit to accurately extract the start and stop pulses of the integer multiple period of the signal to be measured;

[0032] In a specific embodiment, the gate is open for 1 second and the duty cycle is 50%. The D flip-flop circuit consists of one D flip-flop and two differential converters. The D flip-flop is synchronized with the gate signal generated by the FPGA circuit for multiple cycles, and the differential converter is used to convert differential signals to single-ended signals. Figure 2 As shown, the overall timing diagram of the system is as follows Figure 3 shown.

[0033] (2) Surface acoustic wave circuit, through which a time-domain stretched narrowband signal is obtained. The extracted start and stop pulses are passed through a surface acoustic wave filter and stretched in the time domain to obtain a frequency-domain narrowband signal.

[0034] The surface acoustic wave circuit includes a surface acoustic wave filter. The center frequency and time domain width of the narrowband signal are determined by the center frequency and bandwidth of the surface acoustic wave filter. The function of the surface acoustic wave circuit is to stretch the signal in the time domain to obtain a narrowband signal in the frequency domain.

[0035] In a specific embodiment, the narrowband signal has a center frequency of 140 MHz and a bandwidth of 7 MHz.

[0036] (3) ADC circuit, used for high-speed sampling of narrowband signals. After high-speed sampling and interpolation by the ADC circuit, the narrowband signal is subjected to autocorrelation operation to obtain the time interval measurement value, that is, the integer multiple period value of the signal to be measured;

[0037] In a specific embodiment, digital sampling is performed by an ADC chip with a sampling frequency of 200 MHz to ensure that the sampling sequence has no aliasing phenomenon, and the voltage threshold is used to effectively judge and obtain the waveform to obtain the required sampling signal. The sampling signal is as follows: Figure 4 shown.

[0038] (4) FPGA circuit, for generating gate signal, control D flip-flop circuit accurate extraction of the start and stop pulse of the integer multiple period of the signal to be measured, at the same time, through counting method, the complete pulse in the gate time is counted. And the signal after ADC sampling is carried out interpolation operation and autocorrelation operation, the integer multiple period value of the signal to be measured is obtained, combined with the counting result in the gate time, the period value of the signal to be measured is obtained, after conversion, the frequency measurement value is obtained, the integer multiple period measurement result of the signal to be measured is as shown in Figure 5 , the period measurement result of the signal to be measured is as shown in Figure 6 , and the frequency measurement result is as shown in Figure 7 .

[0039] In specific embodiments, the period of the signal to be measured can be represented as , and the frequency can be represented as , wherein is the integer multiple period value of the signal to be measured, and n is the counting value of the FPGA circuit for the complete pulse of the signal to be measured in the gate time.

[0040] Conclusion: The time interval measurement method based on the surface acoustic wave filter in the application realizes the measurement resolution of 1ps under the limited sampling frequency, greatly improves the accuracy and stability of the frequency measurement. Through the preset gate time of the FPGA to control the D flip-flop circuit for multi-period synchronous measurement, the accuracy of the measurement is further improved.

[0041] It should be noted that although the above embodiments have been described in this paper, the patent protection scope of the application is not limited thereby. Therefore, based on the innovative idea of the application, the changes and modifications of the embodiments described in this paper, or the equivalent structure, equivalent process or equivalent function transformation made by using the content of the application specification and drawings, directly or indirectly, apply the above technical solutions to other related technical fields, all are included in the protection scope of the patent of the application.

Claims

1. A high-precision frequency measurement method based on a surface acoustic wave filter, characterized by: The D flip-flop circuit, the surface acoustic wave circuit, the ADC circuit and the FPGA circuit are sequentially electrically connected; the FPGA circuit generates a gate signal to control the D flip-flop circuit to accurately extract start and stop pulses of an integer multiple period of a to-be-measured signal, the surface acoustic wave circuit obtains a time-domain stretched narrowband signal, the narrowband signal is high-speed sampled and interpolated by the ADC circuit, and then autocorrelation operation is performed to obtain a time interval measurement value, i.e. an integer multiple period value of the to-be-measured signal; finally, the FPGA circuit combines a counting value of complete pulses of the to-be-measured signal in the gate time to obtain a period value of the to-be-measured signal, and a frequency measurement value is obtained through conversion; The D flip-flop circuit is composed of one D flip-flop and two differential converters; wherein the D flip-flop is synchronized by a gate signal generated by the FPGA circuit for multiple periods, and the differential converter is used for conversion between differential signals and single-ended signals. The center frequency of the narrowband signal is 140 MHz, and the bandwidth is 7 MHz; the ADC chip with a sampling frequency of 200 MHz is used for digital sampling processing to ensure that the sampling sequence has no aliasing phenomenon, and the voltage threshold value is used for judgment to effectively judge and obtain the waveform and obtain the required sampling signal.

2. The high-precision frequency measurement method based on the surface acoustic wave filter according to claim 1, characterized in that: The FPGA circuit generates a gate signal to control the D flip-flop circuit to accurately extract start and stop pulses of an integer multiple period of a to-be-measured signal; at the same time, the counting method is used to count the complete pulses in the gate time.

3. The high-precision frequency measurement method based on the surface acoustic wave filter according to claim 1, characterized in that: The surface acoustic wave circuit is used to stretch the signal in the time domain to obtain a narrowband signal in the frequency domain; the surface acoustic wave circuit includes a surface acoustic wave filter, and the center frequency and time domain width of the narrowband signal are determined by the center frequency and bandwidth of the surface acoustic wave filter.

4. The high-precision frequency measurement method based on the surface acoustic wave filter according to claim 1, characterized in that: The FPGA circuit part performs autocorrelation operation on the high-speed sampled and interpolated signal of the ADC circuit to obtain an integer multiple period value of the signal to be measured , and the FPGA circuit counts the number of complete pulses of the signal to be measured in the gate time to obtain the period of the signal to be measured , and the frequency is represented as .

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