High-precision frequency measurement method based on surface acoustic wave filter

Abstract

The invention relates to the technical field of electronic measurement, in particular to a high-precision frequency measurement method based on a surface acoustic wave filter, comprising a D flip-flop circuit, a surface acoustic wave circuit and an FPGA (field programmable gate array) circuit which are electrically connected in sequence. The FPGA circuit generates a gate signal, controls the D flip-flop circuit to accurately extract starting and stopping pulses of an integral multiple period of a signal to be measured, obtains a time domain stretched narrow-band signal through the surface acoustic wave filter, and carries out self-correlation operation after high-speed sampling and interpolation of the narrow-band signal through the ADC circuit to obtain a time interval measurement value, namely an integral multiple period value of the signal to be measured. And finally, calculating to obtain a period value of the signal to be measured by combining a counting value of the complete pulse of the signal to be measured in the gate time of the FPGA circuit, and converting to obtain a frequency measurement value. According to the time interval measurement method based on the surface acoustic wave filter, the multi-cycle synchronization technology controlled by the FPGA circuit is combined, and the high-precision and high-stability frequency measurement method is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic measurement, and in particular to a high-precision frequency measurement method based on a surface acoustic wave filter. Background Art

[0002] High-precision time and frequency measurement technology plays a vital role and has a far-reaching impact in many fields. It can provide accurate synchronization and clock reference for communication systems, navigation systems, radar systems, and scientific experiments, ensuring stable and accurate system performance. In addition, high-precision measurement can also help improve data transmission efficiency, enhance the system's anti-interference ability, 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 cycles of a 1-second gate signal. However, this method has inherent limitations: the gate time may not be synchronized with the input signal trigger moment, thus introducing a measurement error of ±1 cycle. Therefore, the accuracy of frequency measurement using traditional frequency measurement methods is often not high. Summary of the invention

[0004] The main purpose of the present invention is to overcome the deficiencies in the prior art and provide a high-precision frequency measurement method. The time interval measurement method based on the surface acoustic wave filter, combined with the multi-cycle synchronization technology, solves the technical problem that the prior art cannot effectively achieve high-precision and high-resolution signal frequency measurement.

[0005] The technical solution adopted by the present invention to achieve its technical purpose is: a high-precision frequency measurement method based on a surface acoustic wave filter, comprising a D trigger circuit, a surface acoustic wave circuit, an ADC circuit and an FPGA circuit electrically connected in sequence; The FPGA circuit generates a gate signal to control the D-type flip-flop circuit to accurately extract the start and stop pulses of the integer multiple period of the signal to be measured, and obtains a time domain stretched narrowband signal through the surface acoustic wave circuit. The narrowband signal is sampled and interpolated at high speed by the ADC circuit, and then an autocorrelation operation is performed to obtain a time interval measurement value, that is, an integer multiple period value of the signal to be measured; Finally, the count value of the complete pulse of the signal to be measured within the gate time is combined with the FPGA circuit to calculate the period value of the signal to be measured, and the frequency measurement value is obtained after conversion.

[0006] Preferably, the FPGA circuit generates a gate signal to control the D-type flip-flop circuit to accurately extract the start and stop pulses of integer multiple cycles of the signal to be measured; at the same time, the complete pulses within the gate time are counted by a counting method.

[0007] Preferably, the D flip-flop circuit is composed of 1 D flip-flop and 2 differential converters; The D trigger performs multi-cycle synchronization through a gate signal generated by an FPGA circuit, and the differential converter is used for converting differential signals and single-ended signals.

[0008] Preferably, the surface acoustic wave circuit functions 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.

[0009] 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 signal to be measured. , combined with the count value n of the complete pulse of the signal to be measured by the FPGA circuit within the gate time, the period of the signal to be measured is obtained , the frequency can be expressed as .

[0010] Compared with the prior art, the present invention has the following beneficial effects: This high-precision frequency measurement method based on the surface acoustic wave filter, combined with the multi-cycle synchronization technology controlled by the FPGA circuit, realizes a high-precision and high-stability frequency measurement method. The improvements and enhancements are mainly made in two aspects: The first is to improve the traditional frequency counting method, such as multi-cycle synchronization method, equal-precision frequency measurement technology, etc., by keeping synchronization with the measured signal, eliminating the ±1 error and improving the measurement accuracy; The second is to use high-precision time interval measurement technology to directly determine the period of the measured signal, and to achieve high-precision and high-resolution measurement of the signal frequency by accurately capturing and measuring the short time intervals within the signal period, such as using surface acoustic wave filters (SAWF) and time-amplitude converters (TAC) and other measurement methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the process of the present invention.

[0012] Figure 2 Schematic diagram of the principle of a D flip-flop circuit in an embodiment of the present invention.

[0013] Figure 3 It is an overall timing diagram of the system in the embodiment of the present invention.

[0014] Figure 4 It is a schematic diagram of the signal after ADC sampling in an embodiment of the present invention.

[0015] Figure 5It is the integer multiple period measurement result of the signal to be measured in the embodiment of the present invention.

[0016] Figure 6 is the period measurement result of the signal to be measured in the embodiment of the present invention.

[0017] Figure 7 is the frequency measurement result of the signal to be measured in the embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to clearly explain the purpose, technical solutions and advantages of the present invention, the following will be described in detail with reference to the accompanying drawings and specific implementation cases. However, it should be noted that these implementation cases are only used to illustrate the present invention and do not constitute a limitation on its scope. In the description process, well-known structures and technologies will not be described in detail to avoid confusing the core points of the present invention.

[0019] In the present invention, when the terms "fixed to" or "arranged to" are used to describe the relationship between elements, it should be understood to include the situation of being fixed directly or indirectly fixed through other elements; similarly, the term "connected to" should be understood to include the situation of being directly connected or indirectly connected through an intermediate connector. The use of these terms does not constitute a limitation on the specific implementation of the present invention, but is used to clearly explain the relative positional relationship between elements.

[0020] The orientation and position terms used in the description of the present invention, such as "center", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., are all based on the conventional placement orientation or position relationship of the product shown in the drawings or when in use. The use of these terms is intended to simplify the description of the present invention and is not intended to limit the described devices or elements to have a specific orientation or to be constructed and operated in a specific orientation. Therefore, the use of these terms should not be understood as a limitation on the present invention. In the description of the present invention, the meaning of "multiple" refers to two or more elements or features, while "several" refers to one or more elements or features, unless otherwise clearly and specifically defined in the context. These definitions help to accurately describe the scope and features of the present invention, but do not constitute a limitation on the scope of the present invention.

[0021] In the present invention, the terms "disposed", "installed", "connected" and "connected" should be interpreted in a broad sense, including but not limited to fixed, detachable or integrated connection, mechanical or electrical connection, direct or indirect connection through a medium, and internal communication between two components. Those skilled in the art can understand the specific meanings of these terms according to specific circumstances. Unless otherwise explicitly defined, these interpretations apply.

[0022] Example: See also Figure 1-Figure 7 , a high-precision frequency measurement method based on surface acoustic wave filter, specifically including the following parts: (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; In a specific embodiment, the gate opening time is 1s and the duty cycle is 50%. The D flip-flop circuit is composed of 1 D flip-flop and 2 differential converters, wherein the D flip-flop is synchronized with the gate signal generated by the FPGA circuit for multiple cycles, and the differential converter is used for the conversion between differential signals and single-ended signals. Figure 2 As shown, the overall timing diagram of the system is as follows Figure 3 shown.

[0023] (2) A surface acoustic wave circuit is used to obtain a time-domain stretched narrowband signal. 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. 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.

[0024] In a specific embodiment, the center frequency of the narrowband signal is 140 MHz and the bandwidth is 7 MHz.

[0025] (3) ADC circuit, used for high-speed sampling of narrow-band signals. The narrow-band signals are sampled and interpolated by the ADC circuit at high speed, and then autocorrelation operation is performed to obtain the time interval measurement value, that is, the integer multiple period value of the signal to be measured; In a specific embodiment, digital sampling is performed through 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.

[0026] (4) FPGA circuit, used to generate gate signal, control D flip-flop circuit to accurately extract the start and stop pulses of integer multiple period of the signal to be measured, and count the complete pulses within the gate time by counting method. Interpolation and autocorrelation operation are performed on the signal sampled by ADC to obtain the integer multiple period value of the signal to be measured, and the period value of the signal to be measured is obtained by calculation combined with the counting result within the gate time. The frequency measurement value is obtained after conversion. The integer multiple period measurement result of the signal to be measured is as follows: Figure 5 As shown in the figure, the period measurement result of the signal to be measured is as follows Figure 6 The frequency measurement results are shown in Figure 7 shown.

[0027] In a specific embodiment, the period of the frequency signal to be measured can be expressed as , the frequency can be expressed as ,in, is an integer multiple of the period value of the signal to be measured, and n is the count value of the complete pulse of the signal to be measured by the FPGA circuit within the gate time.

[0028] Conclusion: The time interval measurement method based on the surface acoustic wave filter of the present invention achieves a measurement resolution of 1ps under a limited sampling frequency, greatly improving the accuracy and stability of frequency measurement. The multi-cycle synchronous measurement is performed by controlling the D flip-flop circuit through the preset gate time of FPGA, further improving the measurement accuracy.

[0029] It should be noted that although the above embodiments have been described in this article, the scope of patent protection of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, changes and modifications made to the embodiments described herein, or equivalent structures, equivalent processes or equivalent functional transformations made using the contents of the present specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields are all included in the scope of protection of the patent of the present invention.

Claims

1. A high-precision frequency measurement method based on a surface acoustic wave filter, characterized in that: The invention comprises a D-type flip-flop circuit, a surface acoustic wave circuit, an ADC circuit and an FPGA circuit which are electrically connected in sequence; the FPGA circuit generates a gate signal to control the D-type flip-flop circuit to accurately extract the start and stop pulses of the integer multiple period of the signal to be measured, and obtains a time domain stretched narrowband signal through the surface acoustic wave circuit; the narrowband signal is sampled and interpolated at high speed by the ADC circuit, and then an autocorrelation operation is performed to obtain a time interval measurement value, that is, an integer multiple period value of the signal to be measured; finally, the period value of the signal to be measured is obtained by operation in combination with the count value of the complete pulse of the signal to be measured by the FPGA circuit within the gate time, and the frequency measurement value is obtained by conversion.

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

3. The high-precision frequency measurement method based on a surface acoustic wave filter according to claim 1, characterized in that: The D flip-flop circuit is composed of one D flip-flop and two differential converters; wherein the D flip-flop is synchronized in multiple cycles by a gate signal generated by an FPGA circuit, and the differential converter is used for converting differential signals and single-ended signals.

4. The high-precision frequency measurement method based on a surface acoustic wave filter according to claim 1, characterized in that: 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; 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.

5. The high-precision frequency measurement method based on a surface acoustic wave filter according to claim 1, characterized in that: 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 signal to be measured. , combined with the count value n of the complete pulse of the signal to be measured by the FPGA circuit within the gate time, the period of the signal to be measured is obtained , the frequency can be expressed as .

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