Surface acoustic wave measurement system based on superheterodyne demodulation technology

Abstract

The invention discloses a surface acoustic wave measurement system based on a superheterodyne demodulation technology, and belongs to the technical field of surface acoustic wave measurement. Comprising a fractional phase-locked loop, an FPGA-based digital phase-locked module and an SAW device module, the fractional phase-locked loop is connected with the SAW device module through the attenuator, the first broadband bottom noise amplifier and the first mixer, the first mixer is further connected with the FPGA-based digital phase-locked module, and the FPGA-based digital phase-locked module is connected with the SAW device module through the microcontroller and the upper computer. According to the invention, the long-time phase detection capability of a single-frequency small signal is improved, and the amplitude and phase shift of a weak radio-frequency signal can be detected with extremely high stability and resolution by using circuit modules such as a fractional phase-locked loop, a frequency mixer and a low-noise amplifier.

Description

Technical Field

[0001] The invention relates to the technical field of surface acoustic wave measurement, and in particular to a surface acoustic wave measurement system based on superheterodyne demodulation technology. Background Art

[0002] Surface acoustic wave (SAW) is a special type of acoustic mode that propagates along a solid surface at a length scale of approximately its wavelength. Environmental disturbances directly affect the propagation velocity v and insertion loss Γ of the surface acoustic wave. Therefore, SAW is widely used as a sensor in many applications due to its unique advantages, such as small size, low cost and easy manufacturing. In the past few decades, SAW sensors have been developed for various applications, such as temperature, pressure, strain or biosensing applications. In the study of quantum phenomena, surface acoustic wave is also a very useful current-free transmission measurement technique. It has been used to study the properties of two-dimensional systems and to understand the properties of fragile quantum states.

[0003] The existing surface acoustic wave measurement technology still has the following shortcomings: 1) The existing surface acoustic wave measurement technology has low phase stability and low resolution, and cannot achieve high phase detection accuracy; 2) The existing surface acoustic wave measurement technology has no exploration of temperature sensors and cannot realize the process of measuring surface acoustic wave velocity from 30K to room temperature. Summary of the invention

[0004] The purpose of the present invention is to provide a surface acoustic wave measurement system based on superheterodyne demodulation technology, which uses the superheterodyne orthogonal demodulation principle to design a radio frequency phase-locked amplifier, improves the long-term phase detection capability of a single-frequency small signal, and uses circuit modules such as a fractional phase-locked loop, a mixer, and a low-noise amplifier to detect the amplitude and phase shift of a weak radio frequency signal with extremely high stability and resolution, and has high phase stability, and works in an environment below 30K to above 300K, with a sensitivity of 40ppm / K at room temperature.

[0005] To achieve the above-mentioned purpose, the present invention provides a surface acoustic wave measurement system based on superheterodyne demodulation technology, comprising a fractional phase-locked loop, a digital phase-locked module based on FPGA and a SAW device module; the fractional phase-locked loop is connected to the SAW device module through an attenuator, a first broadband noise floor amplifier and a first mixer, and the first mixer is also connected to the digital phase-locked module based on FPGA, and the digital phase-locked module based on FPGA is connected to the SAW device module through a microcontroller and a host computer.

[0006] Preferably, the fractional phase-locked loop includes a first fractional phase-locked loop and a second fractional phase-locked loop, the first fractional phase-locked loop is connected to the attenuator, and the second fractional phase-locked loop is connected to the first mixer.

[0007] Preferably, the first fractional phase-locked loop and the second fractional phase-locked loop respectively generate two single-frequency signals V in and V LO , V in The frequency is f in =(n / m)f CLK , V LO The frequency is f LO =f CLK (n+k) / m;

[0008] Where n, m, k are positive integers, f CLK is the reference clock frequency.

[0009] Preferably, the FPGA-based digital phase-locked module includes a bandpass filter, which is connected in series with a second broadband noise floor amplifier, an analog-to-digital converter, a second mixer and a first low-frequency filter, and in parallel with a second low-frequency filter, a third mixer, a frequency shifter and a digitally controlled oscillator, and the digitally controlled oscillator is connected in parallel with the first fractional phase-locked loop and the second fractional phase-locked loop.

[0010] Preferably, the first low-frequency filter and the second low-frequency filter are both connected to the microcontroller, and the microcontroller is connected to the host computer for mutual communication.

[0011] Preferably, the SAW device module comprises a SAW device and a reference module, and the SAW device is connected to the reference module in a circumferential manner via a first microwave mechanical switch and a second microwave mechanical switch.

[0012] Preferably, the first microwave mechanical switch is connected to the attenuator, and the second microwave mechanical switch is connected to the first broadband floor noise amplifier.

[0013] Therefore, the present invention adopts a surface acoustic wave measurement system based on superheterodyne demodulation technology with the above structure, which has the following beneficial effects:

[0014] The present invention improves the long-term phase detection capability of a small single-frequency signal, and can detect the amplitude and phase shift of a weak radio frequency signal with extremely high stability and resolution by using circuit modules such as a fractional phase-locked loop, a mixer, and a low-noise amplifier.

[0015] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a superheterodyne quadrature phase demodulation system of a surface acoustic wave measurement system based on superheterodyne demodulation technology of the present invention;

[0017] Reference numerals

[0018] 1. First fractional phase-locked loop; 2. Second fractional phase-locked loop; 3. Attenuator; 4. First broadband noise floor amplifier; 5. First mixer; 6. Bandpass filter; 7. Second broadband noise floor amplifier; 8. Analog-to-digital converter; 9. Second mixer; 10. First low-frequency filter; 11. Second low-frequency filter; 12. Microcontroller; 13. Third mixer; 14. Frequency shifter; 15. Digitally controlled oscillator; 16. SAW device; 17. Reference module; 18. Host computer; 19. First microwave mechanical switch; 20. Second microwave mechanical switch. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0021] Example

[0022] like Figure 1 As shown, the present invention provides a surface acoustic wave measurement system based on superheterodyne demodulation technology, including a fractional phase-locked loop, a digital phase-locked module based on FPGA and a SAW device module; the fractional phase-locked loop is connected to the SAW device module through an attenuator 3, a first broadband noise floor amplifier 4 and a first mixer 5, and the first mixer 5 is also connected to the digital phase-locked module based on FPGA, and the digital phase-locked module based on FPGA is connected to the SAW device module through a microcontroller 12 and a host computer 18.

[0023] The fractional phase-locked loop comprises a first fractional phase-locked loop 1 and a second fractional phase-locked loop 2 . The first fractional phase-locked loop 1 is connected to an attenuator 3 , and the second fractional phase-locked loop 1 is connected to a first mixer 5 .

[0024] The first fractional phase-locked loop 1 and the second fractional phase-locked loop 2 generate two single-frequency signals V in and V LO , Vin The frequency is f in =(n / m)f CLK , V LO The frequency is f LO =f CLK (n+k) / m;

[0025] Where n, m, k are positive integers, f CLK is the reference clock frequency.

[0026] The FPGA-based digital phase-locked module includes a bandpass filter 6, which is connected in series with a second broadband noise floor amplifier 7, an analog-to-digital converter 8, a second mixer 9 and a first low-frequency filter 10, and is connected in parallel with a second low-frequency filter 11, a third mixer 13, a frequency shifter 14 and a digitally controlled oscillator 15. The digitally controlled oscillator 15 is connected in parallel with the first fractional phase-locked loop 1 and the second fractional phase-locked loop 2.

[0027] The first low-frequency filter 10 and the second low-frequency filter 11 are both connected to the microcontroller 12 , and the microcontroller 12 is connected to the host computer 18 for mutual communication.

[0028] The SAW device module includes a SAW device 16 and a reference module 17. The SAW device 16 is connected to the reference module 17 through a first microwave mechanical switch 19 and a second microwave mechanical switch 20. The first microwave mechanical switch 19 is connected to the attenuator 3, and the second microwave mechanical switch 20 is connected to the first broadband noise floor amplifier 4.

[0029] Working principle: The first fractional phase-locked loop 1 and the second fractional phase-locked loop 2 generate two single-frequency signals V in and V LO , whose frequencies are f in =(n / m)f CLK , f LO =f CLK (n+k) / m, n, m, k are positive integers. CLK is the reference clock frequency, to which the signal source frequency is tightly locked. V in Insertion loss (|S 21 ∣) and phase shift (Ф). V out The output signal is amplified by the first broadband noise floor amplifier 4 and the reference signal V LO After the first mixer 5, the frequency is shifted to the intermediate frequency f d (100kHz). The bandpass filter 6 and the second broadband noise floor amplifier 7 are used to convert it into a digital signal through the analog-to-digital converter 8. For the detection of such an audio signal, the digital phase-locked technology based on FPGA is used. Specifically, the digital controlled oscillator 15 is used to generate two orthogonal reference signals, the intermediate frequency signal f IF =|fin -f LO |=(k / m)f CLK and the signal after it is shifted 90° by the frequency shifter 14. d The two orthogonal signals are filtered through the second mixer 9 and the third mixer 13 and the first low-frequency filter 10 and the second low-frequency filter 11 to obtain the I component and the Q component. The amplitude information and phase information of the signal can be derived from this.

[0030]

[0031] Φ d =tan -1 (Q / I)

[0032] From this, we can get the device insertion loss (|S 21 ∣) and phase shift (Ф)

[0033]

[0034] Φ=Φ d -const

[0035] G is the total gain of the low noise amplifier and the mixer. The measured V d The phase (Φ d ) and the phase shift Φ of the device will differ by a constant.

[0036] Therefore, the present invention adopts the above-mentioned surface acoustic wave measurement system based on superheterodyne demodulation technology to improve the long-term phase detection capability of single-frequency small signals, and uses circuit modules such as fractional phase-locked loops, mixers, and low-noise amplifiers to detect the amplitude and phase shift of weak radio frequency signals with extremely high stability and resolution.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A surface acoustic wave measurement system based on superheterodyne demodulation technology, characterized in that: A fractional phase-locked loop, a digital phase-locked module based on FPGA and a SAW device module; the fractional phase-locked loop is connected to the SAW device module via an attenuator, a first broadband noise floor amplifier and a first mixer, and the first mixer is also connected to the digital phase-locked module based on FPGA, and the digital phase-locked module based on FPGA is connected to the SAW device module via a microcontroller and a host computer.

2. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 1, characterized in that: The fractional phase-locked loop includes a first fractional phase-locked loop and a second fractional phase-locked loop, the first fractional phase-locked loop is connected to the attenuator, and the second fractional phase-locked loop is connected to the first mixer.

3. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 1, characterized in that: The first fractional phase-locked loop and the second fractional phase-locked loop respectively generate two single-frequency signals V in and V LO , V in The frequency is f in =(n / m)f CLK , V LO The frequency is f LO =f CLK (n+k) / m; Where n, m, k are positive integers, f CLK is the reference clock frequency.

4. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 1, characterized in that: The FPGA-based digital phase-locked module includes a bandpass filter, which is connected in series with a second broadband noise floor amplifier, an analog-to-digital converter, a second mixer and a first low-frequency filter, and in parallel with the second low-frequency filter, a third mixer, a frequency shifter and a digitally controlled oscillator, and the digitally controlled oscillator is connected in parallel with the first fractional phase-locked loop and the second fractional phase-locked loop.

5. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 4, characterized in that: The first low-frequency filter and the second low-frequency filter are both connected to the microcontroller, and the microcontroller is connected to the host computer for mutual communication.

6. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 1, characterized in that: The SAW device module includes a SAW device and a reference module. The SAW device is connected to the reference module via a first microwave mechanical switch and a second microwave mechanical switch.

7. The surface acoustic wave measurement system based on superheterodyne demodulation technology according to claim 6, characterized in that: The first microwave mechanical switch is connected to the attenuator, and the second microwave mechanical switch is connected to the first broadband floor noise amplifier.

Images