Laser microwave dual-mode composite Doppler velocimeter

Abstract

The invention, which belongs to the technical field of sensor measurement, relates to a laser microwave dual-mode composite Doppler velocimeter comprising a measurement module and a signal processing module. The measuring module comprises an optical measuring module and a microwave measuring module; and the signal processing module is used for receiving the optical signal output by the optical measurement module and the microwave signal output by the microwave measurement module and carrying out frequency detection to respectively obtain an optical Doppler frequency and a microwave Doppler frequency, discriminating the data validity of the two kinds of Doppler frequencies, and realizing signal mode selection and speed inversion. According to the invention, the optical part adopts an all-fiber continuous wave scheme, and the radio frequency part adopts a transceiving combined antenna continuous wave scheme, so that the device has the advantages of high measurement precision, small size and strong environmental adaptability; the velocimeter realizes two measurement systems of laser and microwave, and the two paths of measurement are mutually independent, so that the interference of the two paths of measurement is avoided, and the measurement reliability is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sensor measurement, and in particular to a laser microwave dual-mode composite Doppler velocimeter. Background Art

[0002] Doppler velocimeters have extremely high application value in various military and civilian fields such as fully autonomous navigation and positioning, space measurement, and carrier collision avoidance warning. According to the different measurement signals used by the Doppler velocimeter, it can be divided into infrared Doppler velocimeter, laser Doppler velocimeter, microwave Doppler velocimeter, etc. Among them, the infrared light system has high requirements for the temperature environment, and an additional temperature compensation module needs to be added to the system, which restricts its use in wide temperature range scenarios; the laser Doppler velocimeter has higher resolution and better stability, and is suitable for high-precision measurement scenarios, but because the laser's penetration power is sharply reduced in rainy and snowy weather, and the reflectivity on different surfaces is different, its adaptability to harsh environments is weak; in contrast, the microwave Doppler velocimeter has outstanding advantages in environmental adaptability.

[0003] At present, the more mature Doppler velocimeter solutions mostly adopt single-mode measurement, that is, laser measurement alone or microwave measurement alone. In order to combine the advantages of laser and microwave measurement, expand the scope of use of the instrument, improve measurement accuracy, and promote practical application, the present invention proposes a microwave and laser dual-mode optical path solution, and uses signal processing circuits to perform state discrimination and switching to achieve high-precision speed measurement in multiple scenarios. Summary of the invention

[0004] In view of the above problems, the present invention proposes a laser microwave dual-mode composite Doppler speed meter. In response to the high-precision speed measurement needs in complex environments, the corresponding mode is selected for measurement according to different test environments to ensure signal validity, improve overall measurement accuracy, and provide accurate speed references for various types of carriers. In the present invention, the optical part adopts an all-fiber continuous wave solution, and the radio frequency part adopts a continuous wave solution with a combined transmitting and receiving antenna, which has the advantages of high measurement accuracy, small size, and strong environmental adaptability; the signal processing circuit part completes the filtering, noise reduction, and frequency detection of the Doppler signal, and realizes intelligent switching of the two measurement modes. The speed meter is lightweight and small in size; the speed meter of the present invention realizes two measurement systems, laser and microwave, and the two-way measurement is independent of each other, avoiding interference between the two and improving measurement reliability; in addition, the speed meter of the present invention outputs digital measurement results, which are highly adapted to the guidance and control systems of various land and air carriers, and are convenient for combined application.

[0005] The present invention provides a laser microwave dual-mode composite Doppler velocimeter, comprising: a measurement module and a signal processing module 13;

[0006] The measurement module includes an optical measurement module and a microwave measurement module;

[0007] Optionally, the optical measurement module includes a laser 1, a coupler 1 2, a polarization controller 3, a coupler 2 4, an optical antenna 5, a detector 6, and a circulator 7 respectively connected to the coupler 1 and the coupler 2, which are sequentially connected along the transmission direction of the optical signal;

[0008] The microwave measurement module includes an oscillator 8, a mixer 9, a filter 10, a detector 12 and an amplifier 14 which are sequentially connected along the transmission direction of the microwave signal; the mixer 9 is also connected to a microwave antenna 11;

[0009] The signal processing module 13 is used to receive the optical signal output by the detector 6 and the microwave signal output by the detector 12 and perform frequency detection to obtain the optical Doppler frequency and the microwave Doppler frequency respectively, determine the data validity of the two types of Doppler frequencies, and realize signal mode selection and velocity inversion.

[0010] It can be understood that the signal velocity inversion is implemented according to the Doppler frequency shift formula to obtain the velocity v, and the expression of the Doppler frequency shift formula is:

[0011]

[0012] Among them, λ is the wavelength of the electromagnetic wave, θ is the angle between the relative motion direction and the radial direction of the wave source, both of which are known quantities; f d is the Doppler frequency shift, measured by the above module.

[0013] Optionally, the signal processing circuit 13 includes a preamplifier circuit 1 13-1, an AD sampling circuit 1 13-2, an AD sampling circuit 2 13-3, a digital signal processing chip FPGA 13-4, a DSP operation circuit 13-5, a preamplifier circuit 2 13-6, an LCD real-time display 13-7, and a serial port RS422 13-8;

[0014] The preamplifier circuit 1 13-1 and the preamplifier circuit 2 13-6 are connected to the digital signal processing chip FPGA 13-4 through the AD sampling circuit 1 13-2 and the AD sampling circuit 2 13-3 respectively. The digital signal processing chip FPGA 13-4 is also connected to the DSP operation circuit 13-5, the LCD real-time display 13-7 and the serial port RS422 13-8.

[0015] The digital signal processing chip FPGA is responsible for receiving and sending data externally; the DSP operation circuit is used for performing logical operations, including frequency resolution, data validity judgment and data selection;

[0016] Furthermore, the specific steps of receiving the optical signal output by the detector 6 and the microwave signal output by the detector 12 and performing frequency detection to determine the validity of the data and realize signal mode selection include:

[0017] After receiving the data, the DSP operation circuit 13-5 performs fast Fourier transform on the optical signal and the microwave signal respectively, solves the signal frequency, and obtains the optical Doppler frequency at time t and the microwave Doppler frequency at time t;

[0018] Compare the optical Doppler frequency at time t and the microwave Doppler frequency at time t;

[0019] At the same time, it is compared with the optical Doppler frequency at time t-1 and the microwave Doppler frequency at time t-1. If the signal deviation is within the set threshold range, it is considered that both the optical signal and the microwave signal are valid, and the optical Doppler frequency is selected as the output; if the optical signal is lost or the deviation is too large, the microwave Doppler frequency is selected as the result output.

[0020] Another object of the present invention is to provide a method for using a laser microwave dual-mode composite Doppler velocimeter, comprising:

[0021] Laser 1 emits light source light, which is divided into reference light and signal light by coupler 1 2. The signal light enters optical antenna 5 through circulator 7, is emitted to the ground, and is scattered by the ground to obtain the Doppler frequency of the signal light. The Doppler frequency of the signal light is coupled into the signal light to obtain updated signal light and return to optical antenna 5, and is transmitted to coupler 2 through circulator 7.

[0022] The reference light is transmitted to the coupler 2 4 via the coupler 1 2 and the polarization controller 3;

[0023] The updated signal light and the reference light interfere with each other at the coupler 2 4 to generate interference light, which is transmitted to the detector 6 and outputs an electrical signal; the electrical signal is transmitted to the signal processing module 13 to obtain the optical Doppler frequency;

[0024] The oscillator 8 generates a single frequency f o High power continuous wave t (t), a part of the microwave antenna 11 generates a microwave beam, and the microwave beam is directed to the ground to generate an echo signal, and the echo signal u r (t) Entering the input port 2 of the mixer 9 through the microwave antenna 11;

[0025] The single frequency f o High power continuous wave t The other part of (t) is transmitted to the input port 1 of the mixer 9 to generate a local oscillator signal;

[0026] The local oscillator signal and the echo signal are mixed by the mixer 9 to obtain a mixed signal, and the sum frequency and difference frequency signals are output through the output port of the mixer 9. The sum frequency and difference frequency signals are transmitted to the filter 10 for filtering, and the target echo intermediate frequency signal u is output. d (t);

[0027] The target echo intermediate frequency signal u d (t) transmitting to the amplifier 14 for amplification, and then sending to the signal end of the detector 12 to obtain the final echo signal; the final echo signal is output to the signal processing module 13 for frequency reading to obtain the microwave Doppler frequency;

[0028] Furthermore, the specific steps of obtaining the optical Doppler frequency and the microwave Doppler frequency include:

[0029] The preamplifier circuit 13-1 amplifies and filters the electrical signal to obtain an analog electrical signal, which is transmitted to the AD sampling circuit 13-2. After analog-to-digital conversion of the analog electrical signal, it is transmitted to the digital signal processing chip FPGA13-4 and the DSP operation circuit 13-5 to obtain the optical Doppler frequency. The operation result is sent to the outside through the serial port RS422 and displayed in real time on the LCD.

[0030] The preamplifier circuit 13-6 amplifies and filters the target echo frequency to obtain an analog echo signal, which is transmitted to the AD sampling circuit 13-2. After analog-to-digital conversion of the analog echo signal, it is transmitted to the digital signal processing chip FPGA13-4 and the DSP operation circuit 13-5 to obtain the microwave Doppler frequency.

[0031] Optionally, the expressions of the light source light, signal light and reference light are respectively:

[0032]

[0033] Among them, E Laser Represents the light source light signal, E s Represents signal light signal, E r represents the reference light signal, t represents the transmission time; A0 represents the amplitude of the light source, A s Represents the amplitude of the signal light, A r represents the amplitude of the reference light, f0 represents the frequency of the light emitted by the light source, and f d represents the Doppler frequency shift, represents the phase of the light source, represents the phase of the signal light, Indicates the phase of the reference light.

[0034] Preferably, the expression of the interference light is:

[0035]

[0036] Where I(t) represents the intensity of interference light.

[0037] Preferably, the expression of the electrical signal is:

[0038]

[0039] Where β is the detector response coefficient, V out Indicates the detector output voltage.

[0040] Optionally, the mixer 9 includes a solid-state device network; the solid-state device network includes a nonlinear element and a coupler; the mixing signal is a linear combination of the local oscillator signal and the echo signal frequency, and the expression is:

[0041]

[0042] Among them, y(t) is the output mixing signal at time t, y1(t) is the input signal one at time t, y2(t) is the input signal two at time t, ω1 is the frequency of signal one input to the mixer, and ω2 is the frequency of signal two input to the mixer.

[0043] Optionally, the single frequency f o High power continuous wave t The expression of (t) is:

[0044] u t (t) = U tm cos(2πf o t)

[0045] Among them, u t (t) represents a single frequency f o High power continuous wave t (t), is the local oscillator signal; U tm Indicates the voltage amplitude of the local oscillator signal, f o Indicates the local oscillator signal frequency.

[0046] The echo signal u r The expression of (t) is:

[0047] u r (t) = U rm cos[2π(f o +f d )t]

[0048] Among them, u r (t) represents the echo signal, U rm Indicates the voltage amplitude of the echo signal, f d Indicates the amount of Doppler shift.

[0049] In the present invention, the local oscillator signal and the echo signal are outputted by the mixer including the sum frequency and the difference frequency signal, and the sum frequency is filtered out by the filter to output the target echo intermediate frequency signal u d (t).

[0050] Optionally, the target echo intermediate frequency signal u d (t) is expressed as:

[0051] u d (t) = U dm cos(2πf d t)

[0052] Among them, U dm Indicates the intermediate frequency signal amplitude, f d is the Doppler shift.

[0053] The present invention extracts the Doppler frequency of the moving target echo by means of coherent detection, that is, the echo is subtracted from the local oscillator wave to detect the difference frequency signal. In the optical path, the difference frequency detection is completed by the optical detector, and in the microwave circuit, the difference frequency detection is completed by the detector.

[0054] The present invention sets a signal processing module 13 as a speed data output control unit, taking into account that in actual application scenarios there may be interference from rain and snow, slippery and muddy roads, etc., which will cause a significant reduction in the laser echo power. At this time, a microwave radar with a larger working wavelength has better environmental adaptability. The signal processing module 13 is responsible for collecting speed measurement data of the two modes and judging their effectiveness, which is of great significance for ensuring continuous high-precision speed measurement in complex environments.

[0055] The Doppler speed meter in the present invention utilizes the Doppler effect of electromagnetic waves to generate a linear relationship between frequency shift and speed, and calculates the speed of the object being measured by detecting the Doppler frequency shift. It has the advantages of non-contact measurement, high speed measurement accuracy, good spatial resolution, wide speed measurement range, fast dynamic response, and good directional sensitivity, and is suitable for measuring the speed of vehicles, low-altitude drones and other carriers.

[0056] The laser microwave dual-mode composite velocimeter proposed in the present invention can improve the environmental adaptability while ensuring the speed measurement accuracy of the velocimeter, which helps to improve the performance of the velocimeter in the actual environment. The velocimeter does not rely on external information, and the high-precision speed reference measured autonomously can be provided to various types of carriers such as land and low altitude. In conjunction with the inertial navigation system, it can significantly improve the fully autonomous navigation performance of the carrier.

[0057] Compared with the prior art, the present invention has at least the following beneficial effects:

[0058] The present invention designs a dual-mode composite speed meter solution. When the climate is good and the surface conditions are excellent, a laser Doppler speed meter with higher accuracy is activated. When the climate is bad and the surface conditions are poor, a microwave Doppler speed measurement radar with stronger environmental adaptability is activated. The switching between the two working modes and the final data output channel are controlled and scheduled by the signal processing module 13 according to environmental changes, which can ensure that the moving carrier can measure the speed at any time and place under complex climatic conditions, effectively improving the practicality of the speed meter equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0060] Figure 1 Schematic diagram of the Doppler velocity measurement principle in an embodiment of the present invention;

[0061] Figure 2 It is a schematic diagram of a system scheme diagram of a laser microwave dual-mode composite velocimeter in an embodiment of the present invention;

[0062] Figure 3 A schematic diagram of the laser measurement part of the velocimeter in an embodiment of the present invention;

[0063] Figure 4 A schematic diagram of the microwave measurement part of the velocimeter in an embodiment of the present invention;

[0064] Figure 5 Schematic diagram of a signal detection circuit portion of a tachometer in an embodiment of the present invention;

[0065] Figure 6 The figure is a schematic diagram of the working logic diagram of the speed data output control module of the laser microwave dual-mode composite velocimeter in an embodiment of the present invention.

[0066] Reference numerals:

[0067] Laser 1, coupler 1 2, polarization controller 3, coupler 2 4, optical antenna 5, detector 6, circulator 7, oscillator 8, mixer 9, filter 10, detector 12, amplifier 14, microwave antenna 11, signal processing circuit 13, preamplifier circuit 1 13-1, AD sampling circuit 1 13-2, AD sampling circuit 2 13-3, digital signal processing chip FPGA 13-4, DSP operation circuit 13-5, preamplifier circuit 2 13-6, LCD real-time display 13-7, serial port RS422 13-8. DETAILED DESCRIPTION

[0068] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0069] A specific embodiment of the present invention, as Figure 1-6 , discloses a laser microwave dual-mode composite Doppler velocimeter. In order to illustrate the effectiveness of the method proposed by the present invention, the above technical solution of the present invention is described in detail through a specific embodiment below. The specific implementation steps are as follows:

[0070] The present invention provides a laser microwave dual-mode composite Doppler velocimeter, comprising: a measurement module and a signal processing module 13;

[0071] The measurement module includes an optical measurement module and a microwave measurement module;

[0072] Optionally, the optical measurement module includes a laser 1, a coupler 1 2, a polarization controller 3, a coupler 2 4, an optical antenna 5, a detector 6, and a circulator 7 respectively connected to the coupler 1 and the coupler 2, which are sequentially connected along the transmission direction of the optical signal;

[0073] The microwave measurement module includes an oscillator 8, a mixer 9, a filter 10, a detector 12 and an amplifier 14 which are sequentially connected along the transmission direction of the microwave signal; the mixer 9 is also connected to a microwave antenna 11;

[0074] The signal processing module 13 is used to receive the optical signal output by the detector 6 and the microwave signal output by the detector 12 and perform frequency detection to obtain the optical Doppler frequency and the microwave Doppler frequency respectively, determine the data validity of the two types of Doppler frequencies, and realize signal mode selection and velocity inversion.

[0075] It can be understood that the signal velocity inversion is implemented according to the Doppler frequency shift formula to obtain the velocity v, and the expression of the Doppler frequency shift formula is:

[0076]

[0077] Among them, λ is the wavelength of the electromagnetic wave, θ is the angle between the relative motion direction and the radial direction of the wave source, both of which are known quantities; f d is the Doppler frequency shift, measured by the above module.

[0078] Optionally, the signal processing circuit 13 includes a preamplifier circuit 1 13-1, an AD sampling circuit 1 13-2, an AD sampling circuit 2 13-3, a digital signal processing chip FPGA 13-4, a DSP operation circuit 13-5, a preamplifier circuit 2 13-6, an LCD real-time display 13-7, and a serial port RS422 13-8; Figure 5 ;

[0079] The preamplifier circuit 1 13-1 and the preamplifier circuit 2 13-6 are connected to the digital signal processing chip FPGA 13-4 through the AD sampling circuit 1 13-2 and the AD sampling circuit 2 13-3 respectively. The digital signal processing chip FPGA 13-4 is also connected to the DSP operation circuit 13-5, the LCD real-time display 13-7 and the serial port RS422 13-8.

[0080] The digital signal processing chip FPGA is responsible for receiving, transmitting and forwarding data externally; the DSP operation circuit is used for performing logical operations, including frequency resolution, data validity judgment and / or data selection;

[0081] Furthermore, the specific steps of receiving the optical signal output by the detector 6 and the microwave signal output by the detector 12 and performing frequency detection to determine the validity of the data and realize signal mode selection include:

[0082] After receiving the data, the DSP operation circuit 13-5 performs fast Fourier transform on the optical signal and the microwave signal respectively, solves the signal frequency, and obtains the optical Doppler frequency at time t and the microwave Doppler frequency at time t;

[0083] Compare the optical Doppler frequency at time t and the microwave Doppler frequency at time t;

[0084] At the same time, it is compared with the optical Doppler frequency at time t-1 and the microwave Doppler frequency at time t-1. If the signal deviation is within the set threshold range, it is considered that both the optical signal and the microwave signal are valid, and the optical Doppler frequency is selected as the output; if the optical signal is lost or the deviation is too large, the microwave Doppler frequency is selected as the result output.

[0085] Another object of the present invention is to provide a method for using a laser microwave dual-mode composite Doppler velocimeter, comprising:

[0086] Laser 1 emits light source light, which is divided into reference light and signal light by coupler 1 2. The signal light enters optical antenna 5 through circulator 7, is emitted to the ground, and is scattered by the ground to obtain the Doppler frequency of the signal light. The Doppler frequency of the signal light is coupled into the signal light to obtain updated signal light and return to optical antenna 5, and is transmitted to coupler 2 through circulator 7.

[0087] The reference light is transmitted to the coupler 2 4 via the coupler 1 2 and the polarization controller 3;

[0088] The updated signal light and the reference light interfere with each other at the coupler 2 4 to generate interference light, which is transmitted to the detector 6 and outputs an electrical signal; the electrical signal is transmitted to the signal processing module 13 to obtain the optical Doppler frequency;

[0089] The oscillator 8 generates a single frequency f o High power continuous wave t (t), a part of the microwave antenna 11 generates a microwave beam, and the microwave beam is directed to the ground to generate an echo signal, and the echo signal u r (t) Entering the input port 2 of the mixer 9 through the microwave antenna 11;

[0090] The single frequency f o High power continuous wave t The other part of (t) is transmitted to the input port 1 of the mixer 9 to generate a local oscillator signal;

[0091] The local oscillator signal and the echo signal are mixed by the mixer 9 to obtain a mixed signal, and the sum frequency and difference frequency signals are output through the output port of the mixer 9. The sum frequency and difference frequency signals are transmitted to the filter 10 for filtering, and the target echo intermediate frequency signal u is output. d (t);

[0092] The target echo intermediate frequency signal u d (t) transmitting to the amplifier 14 for amplification, and then sending to the signal end of the detector 12 to obtain the final echo signal; the final echo signal is output to the signal processing module 13 for frequency reading to obtain the microwave Doppler frequency;

[0093] Furthermore, the specific steps of obtaining the optical Doppler frequency and the microwave Doppler frequency include:

[0094] The preamplifier circuit 13-1 amplifies and filters the electrical signal to obtain an analog electrical signal, which is transmitted to the AD sampling circuit 13-2. After analog-to-digital conversion of the analog electrical signal, it is transmitted to the digital signal processing chip FPGA13-4 and the DSP operation circuit 13-5 to obtain the optical Doppler frequency. The operation result is sent to the outside through the serial port RS422 and displayed in real time on the LCD.

[0095] The preamplifier circuit 13-6 amplifies and filters the target echo frequency to obtain an analog echo signal, which is transmitted to the AD sampling circuit 13-2. After analog-to-digital conversion of the analog echo signal, it is transmitted to the digital signal processing chip FPGA 13-4 and the DSP operation circuit 13-5 to obtain the microwave Doppler frequency.

[0096] Optionally, the expressions of the light source light, signal light and reference light are respectively:

[0097]

[0098] Among them, E Laser Represents the light source light signal, E s Represents signal light signal, E r represents the reference light signal, t represents the transmission time; A0 represents the amplitude of the light source, A s Represents the amplitude of the signal light, A r represents the amplitude of the reference light, f0 represents the frequency of the light emitted by the light source, and f d represents the Doppler frequency shift, represents the phase of the light source, represents the phase of the signal light, Indicates the phase of the reference light.

[0099] Preferably, the expression of the interference light is:

[0100]

[0101] Where I(t) represents the intensity of interference light.

[0102] Preferably, the expression of the electrical signal is:

[0103]

[0104] Where β is the detector response coefficient, V out Indicates the detector output voltage.

[0105] Optionally, the mixer 9 includes a solid-state device network; the solid-state device network includes a nonlinear element and a coupler; the mixing signal is a linear combination of the local oscillator signal and the echo signal frequency, and the expression is:

[0106]

[0107] Among them, y(t) is the output mixing signal at time t, y1(r) is the input signal one at time t, y2(t) is the input signal two at time t, ω1 is the frequency of signal one input to the mixer, and ω2 is the frequency of signal two input to the mixer.

[0108] Optionally, the single frequency f o High power continuous wave t The expression of (t) is:

[0109] u t (t) = U tm cos(2πf o t)

[0110] Among them, u t (t) represents a single frequency f o High power continuous wave t (t), is the local oscillator signal; U tm Indicates the voltage amplitude of the local oscillator signal, f o Indicates the local oscillator signal frequency.

[0111] The echo signal u r The expression of (t) is:

[0112] u r (t) = U rm cos[2π(f o +f d )t]

[0113] Among them, u r (t) represents the echo signal, U rm Indicates the voltage amplitude of the echo signal, f d Indicates the amount of Doppler shift.

[0114] In the present invention, the local oscillator signal and the echo signal are outputted by the mixer including the sum frequency and the difference frequency signal, and the sum frequency is filtered out by the filter to output the target echo intermediate frequency signal u d (t).

[0115] Optionally, the target echo intermediate frequency signal u d (t) is expressed as:

[0116] u d (t) = U dm cos(2πf d t)

[0117] Among them, U dm Indicates the intermediate frequency signal amplitude, f d is the Doppler shift.

[0118] The present invention extracts the Doppler frequency of the moving target echo by means of coherent detection, that is, the echo is subtracted from the local oscillator wave to detect the difference frequency signal. In the optical path, the difference frequency detection is completed by the optical detector, and in the microwave circuit, the difference frequency detection is completed by the detector.

[0119] The present invention sets a signal processing module 13 as a speed data output control unit, taking into account that in actual application scenarios there may be interference from rain and snow, slippery and muddy roads, etc., which will cause a significant reduction in the laser echo power. At this time, a microwave radar with a larger working wavelength has better environmental adaptability. The signal processing module 13 is responsible for collecting speed measurement data of the two modes and judging their effectiveness, which is of great significance for ensuring continuous high-precision speed measurement in complex environments.

[0120] The Doppler speed meter in the present invention utilizes the Doppler effect of electromagnetic waves to generate a linear relationship between frequency shift and speed, and calculates the speed of the object being measured by detecting the Doppler frequency shift. It has the advantages of non-contact measurement, high speed measurement accuracy, good spatial resolution, wide speed measurement range, fast dynamic response, and good directional sensitivity, and is suitable for measuring the speed of vehicles, low-altitude drones and other carriers.

[0121] The laser microwave dual-mode composite velocimeter proposed in the present invention can improve the environmental adaptability while ensuring the speed measurement accuracy of the velocimeter, which helps to improve the performance of the velocimeter in the actual environment. The velocimeter does not rely on external information, and the high-precision speed reference measured autonomously can be provided to various types of carriers such as land and low altitude. In conjunction with the inertial navigation system, it can significantly improve the fully autonomous navigation performance of the carrier.

[0122] The Doppler effect of the electromagnetic wave in the present invention is as follows Figure 1 As shown, the wave source inertial coordinate system O′ and the observer inertial coordinate system O are established respectively; the coordinate origin O is stationary relative to the observer, and the coordinate origin O′ is stationary relative to the wave source;

[0123] The relative speed between the source and the observer determines the received frequency.

[0124] The observer is at the origin O of the coordinate system. At time t1, the wave source emits the first wave crest, and the position vector relative to the observer is recorded as r1. The wave source moves at a speed v relative to the observer. At time t2, the wave source emits the second wave crest, and the position vector relative to the observer is recorded as r2. The speed of light is recorded as c.

[0125] The frequency f0 of the light wave in the O′ system and the frequency f of the electromagnetic wave observed by the observer r for

[0126]

[0127] The Doppler speed meter uses a combined transmitting and receiving antenna. When light hits the target, it produces a Doppler frequency shift, and the scattered echo signal produces another Doppler frequency shift.

[0128] The relative motion speed of the target is much smaller than the speed of light. In a certain small period of time, the angle between the electromagnetic wave propagation direction and the relative motion direction can be approximately considered unchanged.

[0129] make Then the frequency at the detection target and the frequency at the transmitting and receiving antenna can be expressed as

[0130]

[0131] Therefore, the electromagnetic frequency observed by the final observer is expressed as:

[0132]

[0133] In the application scenario, the relative speed between the light source and the target is much smaller than the speed of light, that is, The electromagnetic frequency observed by the final observer is Taylor expanded to obtain the modified electromagnetic frequency observed by the observer, which is expressed as:

[0134]

[0135] Based on the modified electromagnetic frequency observed by the observer, the frequency shift f caused by the Doppler effect is obtained d , the expression is:

[0136]

[0137] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A laser microwave dual-mode composite Doppler velocimeter, characterized in that: include: A measurement module and a signal processing module (13); The measurement module includes an optical measurement module and a microwave measurement module; The optical measurement module comprises a laser (1), a coupler 1 (2), a polarization controller (3), a coupler 2 (4), an optical antenna (5), and a detector (6) which are sequentially connected along the optical signal transmission direction; The microwave measurement module comprises an oscillator (8), a mixer (9), a filter (10), a detector (12) and an amplifier (14) which are sequentially connected along the microwave signal transmission direction; The signal processing module (13) is used to receive the optical signal output by the detector (6) and the microwave signal output by the detector (12) and perform frequency detection to obtain the optical Doppler frequency and the microwave Doppler frequency respectively, to judge the data validity of the two types of Doppler frequencies, and to achieve signal mode selection and velocity inversion.

2. The Doppler velocimeter according to claim 1, characterized in that: The optical measurement module further comprises a circulator (7) connected to the coupler 1 (2) and the coupler 2 (4) respectively; The microwave measurement module also includes a microwave antenna (11) connected to the mixer (9).

3. The Doppler velocimeter according to claim 1, characterized in that: The signal processing circuit (13) comprises a preamplifier circuit 1 (13-1), an AD sampling circuit 1 (13-2), an AD sampling circuit 2 (13-3), a digital signal processing chip FPGA (13-4), a DSP operation circuit (13-5) and a preamplifier circuit 2 (13-6); The preamplifier circuit 1 (13-1) and the preamplifier circuit 2 (13-6) are connected to the digital signal processing chip FPGA (13-4) through the AD sampling circuit 1 (13-2) and the AD sampling circuit 2 (13-3), respectively. The digital signal processing chip FPGA (13-4) is also connected to the DSP operation circuit (13-5).

4. The Doppler velocimeter according to claim 3, characterized in that: The signal processing circuit (13) also includes an LCD real-time display (13-7) and a serial port RS422 (13-8); The digital signal processing chip FPGA (13-4) is also connected to the LCD real-time display (13-7) and the serial port RS422 (13-8).

5. The Doppler velocimeter according to claim 1, characterized in that: The mixer (9) comprises a solid-state device network; the solid-state device network comprises a nonlinear element and a coupler.

6. A method for using the laser microwave dual-mode composite Doppler velocimeter according to any one of claims 1 to 5, characterized in that: The laser (1) emits light source light, which is divided into reference light and signal light through a coupler (2). The signal light enters an optical antenna (5) through a circulator (7), is emitted to the ground, and is scattered by the ground to obtain the Doppler frequency of the signal light. The Doppler frequency of the signal light is coupled into the signal light to obtain updated signal light and return to the optical antenna (5), and is transmitted to the second coupler through the circulator (7). The reference light is transmitted to coupler 2 (4) via coupler 1 (2) and polarization controller (3); The updated signal light and the reference light interfere with each other at the coupler 2 (4), generating interference light, which is transmitted to the detector (6) and outputs an electrical signal; the electrical signal is transmitted to the signal processing module (13) to obtain an optical Doppler frequency; The oscillator (8) generates a single-frequency high-power continuous wave, a portion of which is used to generate a microwave beam via a microwave antenna (11). The microwave beam is directed toward the ground to generate an echo signal, and the echo signal enters the second input port of the mixer (9) via the microwave antenna (11); Another part of the high-power continuous wave of the single frequency is transmitted to the first input port of the mixer (9) to generate a local oscillation signal; The single-frequency high-power continuous wave and the echo signal are mixed by a mixer (9) to obtain a mixed signal, and the sum frequency and difference frequency signals are output through the output port of the mixer (9). The sum frequency and difference frequency signals are transmitted to a filter (10) for filtering, and a target echo intermediate frequency signal is output; The target echo intermediate frequency signal is transmitted to the amplifier (14) for amplification and then sent to the signal end of the detector (12) to obtain a final echo signal; the final echo signal is output to the signal processing module (13) for frequency reading to obtain a microwave Doppler frequency.

7. The method for using the laser microwave dual-mode composite Doppler velocimeter according to claim 6, characterized in that: The specific steps of obtaining the optical Doppler frequency and the microwave Doppler frequency include: A preamplifier circuit (13-1) amplifies and filters the electrical signal to obtain an analog electrical signal, which is then transmitted to an AD sampling circuit (13-2). After analog-to-digital conversion is performed on the analog electrical signal, the analog electrical signal is transmitted to a digital signal processing chip FPGA (13-4) and a DSP operation circuit (13-5) to obtain an optical Doppler frequency. The operation result is sent to the outside through a serial port RS422 (13-8) and simultaneously displayed in real time on an LCD (13-7). The preamplifier circuit 2 (13-6) amplifies and filters the target echo frequency to obtain an analog echo signal, which is transmitted to the AD sampling circuit 1 (13-2). After performing analog-to-digital conversion on the analog echo signal, it is transmitted to the digital signal processing chip FPGA (13-4) and the DSP operation circuit (13-5) to obtain the microwave Doppler frequency.

8. The method for using the laser microwave dual-mode composite Doppler velocimeter according to claim 6, characterized in that: The expressions of the light source light, signal light and reference light are respectively: Among them, E Laser Represents the light source light signal, E s Represents signal light signal, E r represents the reference light signal, t represents the transmission time; A0 represents the amplitude of the light source, A s Represents the amplitude of the signal light, A r represents the amplitude of the reference light, f0 represents the frequency of the light emitted by the light source, and f d represents the Doppler frequency shift, represents the phase of the light source, represents the phase of the signal light, Indicates the phase of the reference light.

9. The method for using the laser microwave dual-mode composite Doppler velocimeter according to claim 8, characterized in that: The expression of the interference light is: Where I(t) represents the intensity of interference light.

10. The method for using the laser microwave dual-mode composite Doppler velocimeter according to claim 9, characterized in that: The target echo intermediate frequency signal expression is: u d (t)=U dm cos(2πf d t) Among them, u d (t) is the intermediate frequency signal of the target echo, U dm Indicates the intermediate frequency signal amplitude, f d is the Doppler shift.

Images