WO2020119106A1 - 太赫兹多模实时成像系统 - Google Patents

太赫兹多模实时成像系统 Download PDF

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Publication number
WO2020119106A1
WO2020119106A1 PCT/CN2019/095548 CN2019095548W WO2020119106A1 WO 2020119106 A1 WO2020119106 A1 WO 2020119106A1 CN 2019095548 W CN2019095548 W CN 2019095548W WO 2020119106 A1 WO2020119106 A1 WO 2020119106A1
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Prior art keywords
signal
terahertz
frequency
module
baseband
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PCT/CN2019/095548
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English (en)
French (fr)
Inventor
牟进超
许戎戎
刘昊
于勇
李凉海
刘峰
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北京遥测技术研究所
航天长征火箭技术有限公司
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Priority to EP19895621.1A priority Critical patent/EP3896492A4/en
Publication of WO2020119106A1 publication Critical patent/WO2020119106A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation

Definitions

  • the invention belongs to the technical field of terahertz imaging, and particularly relates to a terahertz real-time imaging system.
  • the terahertz wave has very important application value in air-space situational awareness and air-space target monitoring and tracking.
  • terahertz waves can be used to detect and track long-range targets in the above space .
  • the shape (profile) characteristics of terahertz frequency band targets are clearer than that of Weibo band, and the electromagnetic environment is more pure, which can effectively improve the target detection and recognition capabilities in complex environments.
  • the detection information system in the terahertz frequency band can comprehensively utilize the technical advantages of the microwave frequency band and the infrared frequency band.
  • the infrared focal plane imaging architecture can be comprehensively used to improve the timeliness of target detection, and at the same time, the microwave coherent detection capability can be used to improve the anti-interference ability in complex environments.
  • a terahertz real-time imaging information system with the advantages of miniaturization, high resolution, good real-time performance, wide field of view, and coherent detection can be realized, effectively improving target detection and recognition capabilities .
  • the existing terahertz imaging system has a single working mode, which cannot meet the needs of all-weather monitoring and imaging tracking of suspected targets.
  • the existing terahertz imaging system mainly has two imaging methods.
  • the first way is to use the focal plane imaging architecture to achieve real-time gaze imaging, but the target phase information cannot be obtained.
  • the second imaging method is to use the synthetic aperture radar imaging architecture to achieve coherent detection, but there are the following shortcomings: (1) poor real-time performance; (2) must rely on the relative movement of the system and the target imaging, can not remain relatively stationary; (3 ) No forward looking imaging, limited viewing angle and field of view.
  • the system architecture of the existing terahertz imaging system is not flexible and does not have the equipment potential for standardization and lineage.
  • the technical problem solved by the invention is to overcome the shortcomings of the prior art and provide a terahertz real-time imaging system, which can work in four jobs: passive non-coherent, passive coherent, active non-coherent and active coherent
  • the mode can meet the application requirements of all-weather silent monitoring, imaging and tracking of suspected key targets, and can improve image contrast in the case of poor imaging quality due to environmental factors.
  • a terahertz multimode real-time imaging system including: terahertz quasi-optical feed module, terahertz focal plane imaging array front-end module, intermediate frequency readout circuit, signal processing and control module, A display module, a baseband signal generating module, a terahertz transmit signal and a local oscillator signal module; wherein, the terahertz quasi-optical feeding module is used to receive a terahertz signal of the target and transmit the terahertz signal to the terahertz focal
  • the front-end module of the planar imaging array; the front-end module of the terahertz focal plane imaging array is used to convert the received terahertz signal into a terahertz current, and down-convert the terahertz current to an intermediate frequency signal, and pass the intermediate frequency signal to all
  • the intermediate frequency readout circuit the intermediate frequency readout circuit is used for reading out the intermediate frequency signal output from the front-end module of the
  • the terahertz quasi-optical feed module includes a terahertz quasi-optical lens group and a servo control unit; wherein, the terahertz quasi-optical lens group and the servo control unit are connected,
  • the servo control unit controls the displacement of the terahertz quasi-optical lens group to realize the adjustment of the focal length and field of view of the terahertz quasi-optical lens group;
  • the terahertz quasi-optical lens group is used to receive a terahertz signal of the target, and
  • the terahertz signal is transmitted to the front-end module of the terahertz focal plane imaging array.
  • the front-end module of the terahertz focal plane imaging array includes a terahertz microlens array, a terahertz focal plane array chip, an intermediate frequency output network, and a local oscillator power distribution network; wherein, the terahertz The microlens array and the terahertz focal plane array chip as a whole are used to convert the received terahertz signal into a terahertz current, and down-convert the terahertz current to an intermediate frequency signal; the intermediate frequency output network is used for reading The intermediate frequency signal output by the terahertz focal plane array chip; the local oscillator power distribution network is used to provide point-to-point local oscillator power for the detection/mixing antenna unit in the terahertz focal plane array chip.
  • the intermediate frequency readout circuit includes a matrix switch and a readout circuit array; wherein the matrix switch is controlled by a control instruction unit, gates corresponding rows and columns, and transmits the intermediate frequency signal For the readout circuit array; the readout circuit array includes a number of channels corresponding to the array size of the matrix switch, wherein each channel includes a power amplifier and an analog-to-digital converter, wherein the power amplifier is used for amplification
  • the intermediate frequency signal and the analog-to-digital converter are used to convert the amplified intermediate frequency signal into a digital signal, and pass the digital signal to the signal processing and control module.
  • the signal processing and control module includes a control instruction unit and a signal processing unit; wherein, the signal processing unit is used to receive and process digital signals to generate images and analyze target features, and convert the images Passed to the display module; the control instruction unit is used to generate a control instruction, used to control the servo control unit in the terahertz quasi-optical feed module, and then realize the focal length and field of view transformation of the terahertz quasi-optical lens group; used for control
  • the matrix switch in the intermediate frequency readout circuit further controls the pixel readout sequence in the front-end module of the terahertz focal plane imaging array; it is used to control the baseband signal control unit in the baseband signal generation module to generate the baseband signal waveform.
  • the display module includes a display screen and a manual control unit; wherein, the manual control unit is used to control the control instruction unit; and the display screen is used to receive and display images.
  • the baseband signal generation module includes a baseband signal control unit, a direct digital frequency synthesizer, a clock, an ⁇ D frequency multiplier, a baseband mixer, and an ⁇ E frequency multiplier; wherein, The baseband output signal of the baseband signal control unit and the clock signal of the clock are simultaneously input to the direct digital frequency synthesizer; the direct digital frequency synthesizer synthesizes the baseband output signal and the clock signal to obtain a synthesized signal, And input the synthesized signal to the baseband mixer; the ⁇ D frequency multiplier receives the clock signal and processes to obtain the D frequency multiplied signal, and inputs the D frequency multiplied signal to the baseband mixer; the baseband mixer Receiving the D frequency multiplier signal and the synthesized signal, and processing to obtain the mixing signal, and inputting the mixing signal to the ⁇ E frequency multiplier; the ⁇ E frequency multiplier receiving the mixing signal and processing to obtain the E frequency multiplication signal, and The E-frequency
  • the terahertz transmit signal and local oscillator signal module includes an ⁇ N frequency multiplier, a first drive amplifier, a first single-pole double-throw switch, a second single-pole double-throw switch, a coupler, A second driver amplifier, an ⁇ M frequency multiplier and a terahertz horn antenna; wherein, the ⁇ N frequency multiplier receives the E frequency multiplier signal and processes to obtain an N frequency multiplier signal, and inputs the N frequency multiplier signal to the first Drive amplifier; the first drive amplifier receives the N-multiplied signal and processes it to obtain the first amplified signal; the first amplified signal passes through the first single-pole double-throw switch to select channel 73A or channel 73B; if the first amplified signal passes through channel 73A, Then the first amplified signal is directly fed into the local oscillator power distribution network; if the first amplified signal passes through the channel 73B, then through the second single
  • the frequency of the baseband output signal is f 601
  • the frequency of the clock signal is f 603
  • the present invention has the following beneficial effects:
  • the present invention uses the terahertz quasi-optical feed module to input the terahertz signal of the target and the environment, the terahertz focal plane imaging array front-end module converts the terahertz signal into an intermediate frequency signal, and the path of the transmission and local oscillator signal Switching realizes flexible switching of four working modes: passive non-coherent, passive coherent, active non-coherent and active coherent.
  • the present invention realizes the switching between coherent receiving and non-coherent receiving modes by using a terahertz focal plane array chip based on terahertz Schottky diodes and a local oscillator power distribution network, and solves the problem of simultaneously achieving gaze imaging and acquiring phase information The contradiction between.
  • the terahertz focal plane imaging array chip of the present invention uses flat and compact terahertz pixels to form a two-dimensional high-density array, which is beneficial to achieve flexible design of array scale and flexible splicing of sub-arrays of different scales.
  • the present invention controls the imaging focal length and field of view by controlling the relative position between the lenses in the terahertz quasi-optical lens group with a servo control unit.
  • the present invention generates high-purity, low-phase noise baseband signals by means of baseband mixing to ensure system sensitivity in three working modes: passive coherent, active non-coherent, and active coherent.
  • Figure 1 is a system block diagram of a terahertz multimode real-time imaging system.
  • Figure 2 is a schematic diagram of the composition of the terahertz quasi-optic lens group
  • FIG. 3 is a schematic structural diagram of the front end of a terahertz focal plane imaging array.
  • FIG. 4 is a schematic diagram of sub-array stitching at the front end of a terahertz focal plane imaging array.
  • FIG. 5 is a schematic structural diagram of a terahertz focal plane imaging array pixel.
  • Figure 6 is a topological block diagram of the intermediate frequency readout circuit.
  • This embodiment provides a terahertz multimode real-time imaging microsystem, which includes a terahertz quasi-optical feed module 1, a terahertz focal plane imaging array front-end module 2, an intermediate frequency readout circuit 3, and a signal processing and control module 4.
  • Display module 5 baseband signal generation module 6, terahertz transmission signal and local oscillator signal module 7, as shown in Figure 1.
  • the terahertz quasi-optical feeding module 1 includes a terahertz quasi-optical lens group 11 and a servo control unit 12, and a control interface 4112.
  • the front-end module 2 of the terahertz focal plane imaging array includes a terahertz microlens array 21, a terahertz focal plane array chip 22, an intermediate frequency output network 23, and a local oscillator power distribution network 24.
  • the intermediate frequency readout circuit 3 includes a matrix switch 31 and a readout circuit array 32, and a control interface 4131.
  • the signal processing and control module 4 includes a control instruction unit 41 and a signal processing unit 42, and a control interface 4112, a control interface 4131, a control interface 4161, a control interface 4173 and a control interface 4174.
  • the display module 5 includes a display screen 51 and a manual control unit 52.
  • the baseband signal generation module 6 includes a baseband signal control unit 61, a direct digital frequency synthesizer 62, a clock 63, an ⁇ D frequency multiplier 64, a baseband mixer 65, an ⁇ E frequency multiplier 66, and a control interface 4161.
  • the terahertz transmit signal and local oscillator signal module 7 includes an ⁇ N frequency multiplier 71, a first drive amplifier 72, a first single-pole double-throw switch 73, a second single-pole double-throw switch 74, a coupler 75, a drive amplifier 76, ⁇ M Frequency multiplier 77 and terahertz horn antenna 78, as well as control interface 4173 and control interface 4174.
  • the terahertz quasi-optical feeding module 1 is used to receive the terahertz signal Rx of the target and transmit the signal to the front-end module 2 of the terahertz focal plane imaging array.
  • the front-end module 2 of the terahertz focal plane imaging array is used to convert the received terahertz signal into a terahertz current, and down-convert the terahertz current to an intermediate frequency signal IFx.
  • the intermediate frequency signal IFx will be passed to the intermediate frequency readout circuit 3.
  • the intermediate frequency readout circuit 3 is used to read out the intermediate frequency signal IFx output from the front-end module 2 of the terahertz focal plane imaging array, and further amplify and analog-to-digital convert the intermediate frequency signal to output a digital signal Dx.
  • the digital signal Dx will be passed to the signal processing and control module 4.
  • the signal processing and control module 4 is used to process digital signals to generate images and analyze target features, and pass the images to the display module 5.
  • the signal processing and control module 4 is also used to generate control commands for the following three control functions:
  • the baseband signal control unit 61 in the baseband signal generation module 6 is controlled to generate a baseband signal waveform.
  • the display module 5 is used to display terahertz images of the target and the environment and provide a manual control interface.
  • the baseband signal generation module 6 is used to generate the baseband signal Bx and transmit it to the terahertz transmission signal and local oscillator signal module 7.
  • the terahertz transmission signal and the input signal of the local oscillation signal module 7 are provided by the baseband signal generation module 6, and the local oscillation signal LOx and the terahertz transmission signal Tx are generated by frequency multiplication and amplification.
  • the local oscillator signal is transmitted to the front-end module 2 of the terahertz focal plane imaging array as a local oscillator reference signal.
  • the terahertz transmission signal is radiated onto the target via the terahertz horn antenna 78.
  • the terahertz quasi-optical lens group 11 is composed of at least three terahertz quasi-optical lenses, which are sequentially referred to as a lens 111, a lens 112, a lens 11 (N-1), and a lens 11N.
  • the lens 111 is located on the outermost side of the system, and the lens 11N is located on the side near the front end module 2 of the terahertz focal plane imaging array.
  • the material used in the terahertz quasi-optical lens has a transmittance in the terahertz band of not less than 0.8 and a dielectric constant of not more than 5, such as polytetrafluoroethylene.
  • the optical axes of all terahertz collimator lenses are on the same straight line.
  • the position of the lens 111 is fixed; the position of the lens 112...the lens 11N can be moved along the direction of the optical axis, and the displacement is controlled by the servo control unit 12, thereby realizing the adjustment of the focal length and the field of view, as shown in FIG.
  • the terahertz microlens array 21 and the terahertz focal plane array chip 22 jointly realize the induction and frequency conversion processing of the terahertz spatial signal.
  • the intermediate frequency output network 23 is used to read out the intermediate frequency signal output by the terahertz focal plane array chip 22.
  • the local oscillator power distribution network 24 is used to provide point-to-point local oscillator power for the detection/mixing antenna unit 220 in the terahertz focal plane array chip 22, as shown in FIG.
  • the micro lens unit 210 in the terahertz micro lens array 21 is a medium expansion hemisphere, that is, composed of a hemisphere and a cylinder.
  • the medium expansion hemisphere is used to optimize the directivity of the basic picture element in the terahertz focal plane array chip 22 and improve the radiation gain of the basic picture element.
  • the radius of the hemisphere is R; the height of the cylinder is L, and the radius of the cross section is R.
  • the transmissivity of the material of the extended hemisphere in the terahertz band is not less than 0.8, and the dielectric constant is not more than 5, thereby reducing the impedance mismatch loss between the terahertz microlens array 21 and the terahertz focal plane array chip 22.
  • the microlens units 210 are closely arranged to form a two-dimensional compound eye array structure, and the array size is recorded as A ⁇ B.
  • the basic unit in the terahertz focal plane array chip 22 is the detection/mixing antenna unit 220, as shown in FIG.
  • the characteristic of the detection/mixing antenna is that the differential antenna is used as the basic radiating unit, such as dipole, butterfly antenna, log period antenna, etc.; the diode is used as the frequency conversion unit, and the diode is located at the RF feed port of the differential antenna.
  • Differential antennas are used to convert terahertz radiation into terahertz current and pass it to the diode.
  • Diodes convert terahertz current to low-frequency current.
  • the detection/mixing antenna works in the mixing mode; if the diode does not load a local oscillation signal, the detection/mixing antenna works in the detection mode.
  • the low-frequency current is output through both ends of the differential antenna. Further, in order to improve the conversion efficiency of the detection/mixing antenna and the size of the basic unit in the terahertz focal plane array chip is kept within 1 square wavelength (1 ⁇ 2 , ⁇ is the wavelength of the terahertz signal), the present invention proposes a Compact detection/mixing detection antenna unit structure.
  • a dipole antenna and its deformation (hereinafter collectively referred to as "dipole antenna") are used as the basic radiating element, with a typical length of ⁇ /2; 2 It can be loaded at the RF feed port of the dipole antenna Electrically coupled stripline parallel to the edge of the dipole, typical width ⁇ /20 ⁇ /10, typical length ⁇ /8 ⁇ /3, thus expanding the bandwidth of the dipole antenna; 3 The band-stop filter is loaded at the end, and the center frequency of the stop band is f Signal (f Signal is the working frequency of the terahertz signal).
  • the filter is the passband within the local oscillator bandwidth and the intermediate frequency bandwidth of the terahertz multimode real-time imaging system; 4
  • the typical implementation of the band-reject filter is a "concave" or "I" shaped slot, the concave part of which faces the RF feed port. Its outstanding advantage is that it avoids the dipole antenna from generating sidelobe levels and has a small size.
  • the stopband bandwidth can be controlled; 5
  • the best choice for the diode is a planar terahertz Schottky diode , Its junction capacitance is not greater than 2fF, and its cascade resistance is not greater than 5 ⁇ ; 6
  • the detection/mixing antenna uses dielectric loss of the substrate material Tangent tan ⁇ is not greater than 0.001, dielectric constant ⁇ r is not greater than 5, thickness is not greater than ⁇ /[100 ⁇ ( ⁇ r ) 1/2 ], and the typical material is quartz.
  • the basic pixel pitch D in the terahertz focal plane array chip 22 is ⁇ -5 ⁇ .
  • the array size of the terahertz focal plane array chip 22 is A ⁇ B, which is consistent with the array size of the terahertz microlens array 21.
  • the medium side of the terahertz focal plane array chip 22 closely adheres to the plane side of the image element and the terahertz microlens array 21.
  • the pixels of the terahertz focal plane array chip 22 and the microlenses of the terahertz microlens array 21 maintain a one-to-one spatial relationship, and the center of the pixel is located on the axis of the microlens.
  • the intermediate frequency output network 23 uses a micro-coaxial structure as a basic transmission line for the output of the intermediate frequency signal of the terahertz focal plane array chip 22.
  • the array size of the network is A ⁇ B, which is consistent with that of the terahertz focal plane array chip 22.
  • the basic characteristics of the micro-coaxial structure are: 1contains an outer conductor and an inner conductor, where the inner conductor is electrically connected to one side of the detection/mixing antenna unit 220; The diameters are a and b, respectively, which satisfies (a+b) ⁇ , which ensures that the micro-coax will not produce higher-order modes at the intermediate frequency.
  • the local oscillator power distribution network 24 uses a waveguide as a basic transmission line, and includes A ⁇ B local oscillator power distribution branches 240.
  • the local oscillator power distribution network 24 includes a local oscillator input port 231 and A ⁇ B local oscillator output ports 242.
  • the local oscillator input port 231 is a standard waveguide structure.
  • the terahertz transmission signal and the local oscillator signal module 7 feed the local oscillator signal through the local oscillator input port 231.
  • the local oscillator output port 242 is a non-standard waveguide and works in the TE mode, and the direction of the electric field is consistent with the polarization direction of the dipole antenna in the detection/mixing antenna unit 220.
  • the diode in the detection/mixing antenna unit 220 is located at the center of the local oscillator output port 242.
  • the picture element 20 in the front-end module 2 of the terahertz focal plane imaging array includes a micro lens unit 210, a detection/mixing antenna unit 220, an intermediate frequency output branch 230 and a local oscillator power distribution branch 240.
  • the detection/mixing antenna unit 220 is located between the micro lens unit 210 and the local oscillator power distribution branch 240.
  • the terahertz signal Tx is input to the detection/mixing antenna unit 220 through the micro lens unit 210, and the local oscillation signal LOx is input to the detection/mixing antenna unit 220 through the local oscillation power distribution branch 240.
  • FIG. 4 shows a schematic diagram of sub-array stitching at the front end of the terahertz focal plane imaging array. If the front end of a terahertz focal plane imaging array with an array size of A ⁇ B is used as a subarray, then by two-dimensional stitching, there are M subarrays in the row direction and N subarrays in the column direction to form a larger The front end of the terahertz focal plane array with a scale of (M ⁇ A) ⁇ (N ⁇ B).
  • the matrix switch 31 in the IF readout circuit 3 is used to gate the IF output network 23 to realize the orderly output of the IF signal IFx.
  • the array size is A ⁇ B, which is consistent with the array size of the IF output network 23.
  • the matrix switch 31 receives the control of the control command unit 41 through the control interface 4131, gates the corresponding row and column according to the row and column control unit 311, and transmits the intermediate frequency signal IFx to the readout circuit array 32.
  • the number of channels of the readout circuit array 32 is P (P ⁇ A ⁇ B). As shown in FIG. 6, each channel includes at least a power amplifier 321 and an analog-to-digital converter 322.
  • the power amplifier 321 is used to amplify the intermediate frequency signal, and the analog-to-digital converter 322 is used to convert the amplified intermediate frequency signal into a digital signal.
  • the digital signal output from the readout circuit array 32 is passed to the signal processing and control module 4.
  • the control instruction unit 41 includes five control interfaces, namely a control interface 4112, a control interface 4131, a control interface 4161, a control interface 4173, and a control interface 4174.
  • the control instruction unit 41 accepts the control of the manual control unit 52.
  • the baseband signal control unit 61 outputs the baseband output signal and the clock signal (frequency f 603 ) of the clock 63 to the direct digital frequency synthesizer 62 at the same time, and the output signal is a synthesized signal (frequency f 602 ).
  • the baseband signal generated by this module has the characteristics of small phase noise and pure spectrum.
  • the first amplified signal passes through the first single-pole double-throw switch 73 to select the passage 73A or 73B. If the first amplified signal passes through the channel 73A, the first amplified signal is directly fed into the local oscillator power distribution network 24.
  • the terahertz multi-mode real-time imaging system has four working modes: mode 1-passive non-coherent mode, mode 2-passive coherent mode, mode 3-active non-coherent mode, and mode 4-active coherent mode.
  • the switching of the four working modes is realized by the manual control unit 52 sending commands to the baseband signal generation module 6 and the terahertz signal transmission module and the local oscillator signal module 7 through the control instruction unit 41.
  • Passive non-coherent mode If the control interface 4161 receives a close command, the baseband signal generation module 6 and the terahertz transmit signal and local oscillator signal module 7 stop working, then the terahertz multimode real-time imaging system works in passive non-coherent mode.
  • Passive coherent mode If the control interface 4161 receives the start command, and the control interface 4173 sends a command to the first single-pole double-throw switch 73 to turn on the channel 73A and the channel 73B is disconnected, the THz multimode real-time imaging system works in passive Coherent mode.
  • Active non-coherent mode if the control interface 4161 receives the start command, and the control interface 4173 sends a command to the first single-pole double-throw switch 73 to turn off the channel 73A and the channel 73B is on, and the control interface 4174 gives the second single-pole double-throw
  • the switch 74 sends a command to turn on the channel 74B and the channel 74A is off
  • the terahertz multimode real-time imaging system works in an active non-coherent mode.
  • Active coherent mode if the control interface 4161 receives the start command, and the control interface 4173 sends a command to the first single-pole double-throw switch 73 to turn off the channel 73A and the channel 73B is turned on, and the control interface 4174 gives the second single-pole double-throw switch 74 sends a command to turn on channel 74A and channel 74B is disconnected, the terahertz multimode real-time imaging system works in active coherent mode.
  • the working mode of the terahertz multimode real-time imaging system is as follows:
  • the display module 5, the signal processing and control module 4, the intermediate frequency readout circuit 3, the terahertz focal plane imaging array front-end module 2 and the terahertz quasi-light feeding module 1 are sequentially activated.
  • the terahertz multi-mode real-time imaging system enters a passive non-coherent working mode and enters a 24/7 silent monitoring stage.
  • the baseband signal generation module 6 and the terahertz signal and local oscillator signal module 7 are periodically activated with the T0 cycle as the channel 73A.
  • the terahertz multimode real-time imaging system enters the passive coherent working mode. This can periodically improve the system sensitivity and range.
  • the baseband signal generation module 6 and the terahertz transmission signal and local oscillator signal module 7 are activated, and the channels 73B and 74B are gated.
  • the terahertz multimode real-time imaging system enters the active non-coherent working mode.
  • the channel 73B and the channel 74A are gated.
  • the terahertz multimode real-time imaging system enters the active coherent working mode, and implements imaging and tracking of the target.
  • the servo control unit 12 adjusts the focal length and field of view of the terahertz collimator lens group 11 according to the instruction of the control interface 4112 to implement high-resolution imaging of the target.
  • the baseband signal generation module 6 and the terahertz transmission signal and local oscillator signal module 7 are disabled, and the passive non-coherent working mode is entered again, and the all-weather silent monitoring stage is entered.
  • the terahertz signal of the target and the environment is input by using the terahertz quasi-optical feed module, the terahertz signal is converted into an intermediate frequency signal by the front-end module of the terahertz focal plane imaging array, and the path switching of the transmission and local oscillator signals is implemented Flexible switching of four working modes: passive non-coherent, passive coherent, active non-coherent, and active coherent; this embodiment uses a terahertz focal plane array chip based on a terahertz Schottky diode and a local oscillator power distribution network Realize the switching between coherent receiving and non-coherent receiving modes, and solve the contradiction between simultaneously achieving gaze imaging and acquiring phase information; the terahertz focal plane imaging array chip in this embodiment is formed by flattened compact terahertz pixels The two-dimensional high-density array is conducive to the flexible design of the array size and the flexible splicing of sub-arrays of different sizes; in this embodiment, the relative position between

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Abstract

一种太赫兹多模实时成像系统，包括太赫兹准光馈入模块(1)、太赫兹平面成像阵列前端模块(2)、中频读出电路(3)、信号处理与控制模块(4)、显示模块(5)、基带信号产生模块(6)、太赫兹发射信号与本振信号模块(7)。该系统能够工作于被动非相参、被动相参、主动非相参、主动相参四个工作模式，可以满足全天候静默监视、疑似重点目标成像与跟踪等应用需求，并且可以在由于环境因素导致的成像质量变差的情况下提升图像对比度。该系统适用于空天态势感知与空天目标成像跟踪。

Description

太赫兹多模实时成像系统
本申请要求于2018年12月13日提交中国专利局、申请号为201811522278.X、发明名称为“太赫兹多模实时成像系统”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明属于太赫兹成像技术领域，尤其涉及一种太赫兹实时成像系统。
背景技术
太赫兹(Terahertz，THz)波通常指的是频率在0.1THz～10THz(波长3mm～30μm)范围内的电磁辐射(1THz＝10 12Hz)，在电磁波谱中介于微波和红外辐射之间。太赫兹波在空天态势感知与空天目标监视跟踪方面具有非常重要的应用价值。
从传播特性角度来说，太赫兹波在高空、临近空间和外层空间的传播衰减很小，远远低于近地面空间，因此，可以利用太赫兹波在上述空间实现远距离目标探测与跟踪。
其次，从目标特征角度来说，太赫兹频段目标的形影(轮廓)特征相比于微博频段更为清晰，且电磁环境更为纯净，从而可以有效提升复杂环境下的目标探测与识别能力。
第三，从技术特色角度来说，太赫兹频段的探测信息系统可以综合利用微波频段和红外频段的技术优势。例如可以综合采用红外焦平面成像架构提升目标探测的时效性，同时，利用微波相参探测能力提升复杂环境下的抗干扰能力。通过综合微波频段和红外频段的技术优势，可以实现兼具小型化、分辨率高、实时性好、宽视场、相参探测等优点的太赫兹实时成像信息系统，有效提升目标探测与识别能力。
现有的太赫兹成像系统普遍存在以下问题：
首先，现有太赫兹成像系统的工作模式单一，无法满足全天候监视与疑似目标成像跟踪的需求。
其次，现有太赫兹成像系统主要有两种成像方式。第一种方式是采用焦平面成像架构实现实时凝视成像方式，但是无法获取目标的相位信息。第二种成像方式是采用合成孔径雷达成像架构实现相参探测，但是存在如下不足：(1)实时性较差；(2)必须借助系统与目标的相对移动成像，无法保持相对静止；(3)无法前视成像，观测角度和视场受限。
第三，现有太赫兹成像系统的系统架构不灵活，不具备标准化、谱系化的装备潜力。
发明内容
本发明解决的技术问题是：克服现有技术的不足，提供了一种太赫兹实时成像系统，该系统能够工作于被动非相参、被动相参、主动非相参、主动相参四个工作模式，可以满足全天候静默监视、疑似重点目标成像与跟踪等应用需求，并且可以在由于环境因素导致的成像质量变差的情况下提升图像对比度。
本发明目的通过以下技术方案予以实现：一种太赫兹多模实时成像系统，包括：太赫兹准光馈入模块、太赫兹焦平面成像阵列前端模块、中频读出电路、信号处理与控制模块、显示模块、基带信号产生模块和太赫兹发射信号与本振信号模块；其中，所述太赫兹准光馈入模块用于接收目标的太赫兹信号，并将太赫兹信号传递给所述太赫兹焦平面成像阵列前端模块；所述太赫兹焦平面成像阵列前端模块用于将接收到的太赫兹信号转变为太赫兹电流，并将太赫兹电流降频至中频信号，并将中频信号将传递给所述中频读出电路；所述中频读出电路用于读出所述太赫兹焦平面成像阵列前端模块输出的中频信号，并将中频信号做进一步放大和模-数转换，输出数字信号，并将数字信号将传递给所述信号处理与控制模块；所述信号处理与控制模块用于接收并处理数字信号生成图像，并将图像传递给所述显示模块；所述显示模块用于接收并显示图像并提供 人工控制接口；所述基带信号产生模块用于产生基带信号并传递给所述太赫兹发射信号与本振信号模块；所述太赫兹发射信号与本振信号模块将基带信号通过倍频和放大方式产生本振信号以及太赫兹发射信号，其中，本振信号传递给所述太赫兹焦平面成像阵列前端模块作为本振参考信号，太赫兹发射信号照射到目标上。
上述太赫兹多模实时成像系统中，所述太赫兹准光馈入模块包括太赫兹准光透镜组和伺服控制单元；其中，所述太赫兹准光透镜组和所述伺服控制单元相连接，所述伺服控制单元控制所述太赫兹准光透镜组的位移，实现太赫兹准光透镜组的焦距和视场的调节；所述太赫兹准光透镜组用于接收目标的太赫兹信号，并将太赫兹信号传递给所述太赫兹焦平面成像阵列前端模块。
上述太赫兹多模实时成像系统中，所述太赫兹焦平面成像阵列前端模块包括太赫兹微透镜阵列、太赫兹焦平面阵列芯片、中频输出网络和本振功率分配网络；其中，所述太赫兹微透镜阵列和所述太赫兹焦平面阵列芯片作为整体，用于将接收到的太赫兹信号转变为太赫兹电流，并将太赫兹电流降频至中频信号；所述中频输出网络用于读出太赫兹焦平面阵列芯片输出的中频信号；所述本振功率分配网络用于为太赫兹焦平面阵列芯片中的检波/混频天线单元提供点到点的本振功率。
上述太赫兹多模实时成像系统中，所述中频读出电路包括矩阵开关和读出电路阵列；其中，所述矩阵开关接受控制指令单元的控制，选通相应的行与列，将中频信号传递给所述读出电路阵列；所述读出电路阵列包括与所述矩阵开关的阵列规模相对应数量的通道，其中，每个通道包含功率放大器和模数转换器，其中，功率放大器用于放大中频信号，模数转换器用于将放大后的中频信号转换为数字信号，并将数字信号传递给信号处理与控制模块。
上述太赫兹多模实时成像系统中，所述信号处理与控制模块包括控制指令单元和信号处理单元；其中，所述信号处理单元用于接收并处理数字信号生成图像并分析目标特征，并将图像传递给所述显示模块；控制指令单元用于产生 控制指令，用于控制太赫兹准光馈入模块中的伺服控制单元，进而实现太赫兹准光透镜组的焦距和视场变换；用于控制中频读出电路中的矩阵开关进而控制太赫兹焦平面成像阵列前端模块中的像元读出顺序；用于控制基带信号产生模块中的基带信号控制单元，用于产生基带信号波形。
上述太赫兹多模实时成像系统中，所述显示模块包括显示屏幕和人工控制单元；其中，所述人工控制单元用于控制所述控制指令单元；所述显示屏幕用于接收并显示图像。
上述太赫兹多模实时成像系统中，所述基带信号产生模块包括基带信号控制单元、直接数字式频率合成器、时钟、×D倍频器、基带混频器和×E倍频器；其中，所述基带信号控制单元的基带输出信号和所述时钟的时钟信号同时输入至所述直接数字式频率合成器；所述直接数字式频率合成器将基带输出信号和时钟信号合成后得到合成信号，并将合成信号输入至所述基带混频器；所述×D倍频器接收时钟信号并处理得到D倍频信号，并将D倍频信号输入至基带混频器；所述基带混频器接收D倍频信号和合成信号，并处理得到混频信号，并将混频信号输入至×E倍频器；所述×E倍频器接收混频信号并处理得到E倍频信号，并将E倍频信号输入至所述太赫兹发射信号与本振信号模块。
上述太赫兹多模实时成像系统中，所述太赫兹发射信号与本振信号模块包括×N倍频器、第一驱动放大器、第一单刀双掷开关、第二单刀双掷开关、耦合器、第二驱动放大器、×M倍频器和太赫兹喇叭天线；其中，所述×N倍频器接收E倍频信号并处理得到N倍频信号，并将N倍频信号输入至所述第一驱动放大器；所述第一驱动放大器接收N倍频信号并处理得到第一放大信号；第一放大信号经过第一单刀双掷开关选择经过通道73A或者通道73B；若第一放大信号经过通道73A，则第一放大信号直接馈入本振功率分配网络；若第一放大信号经过通道73B，则经过第二单刀双掷开关选择经过通道74A或者通道74B；若第一放大信号经过通道74A，则经过耦合器分别输入至×M倍频器和第二驱动放大器，所述第二驱动放大器将第一放大信号直接馈入本振功率分配网络； 若第一放大信号经过通道74B，则直接输入至×M倍频器，所述×M倍频器接收第一放大信号并处理得到M倍频信号，并将M倍频信号通过所述太赫兹喇叭天线发射到自由空间中。
上述太赫兹多模实时成像系统中，所述基带输出信号的频率为f 601，所述时钟信号的频率为f 603，合成信号的频率为f 602＝f 601+f 603；D倍频信号的频率为f 604＝D·f 603，混频信号的频率为f 605＝f 604-f 602，E倍频信号的频率为f 606＝E·f 605。
上述太赫兹多模实时成像系统中，所述N倍频信号的频率为f 701＝N·f 606，第一放大信号的频率为f 702＝f 701，M倍频信号的频率为f 707＝M·f 702。
本发明与现有技术相比具有如下有益效果：
(1)本发明通过采用太赫兹准光馈入模块输入目标和环境的太赫兹信号、通过太赫兹焦平面成像阵列前端模块将太赫兹信号转变为中频信号，以及通过发射和本振信号的通路切换实现被动非相参、被动相参、主动非相参、主动相参四个工作模式的灵活切换。
(2)本发明通过采用基于太赫兹肖特基二极管的太赫兹焦平面阵列芯片以及本振功率分配网络实现相参接收和非相参接收模式的切换，并解决同时实现凝视成像和获取相位信息之间的矛盾。
(3)本发明中的太赫兹焦平面成像阵列芯片采用扁平化紧凑型太赫兹像元形成二维高密度阵列，有利于实现阵列规模的灵活设计以及不同规模子阵的灵活拼接。
(4)本发明通过用伺服控制单元控制太赫兹准光透镜组中透镜间的相对位置控制成像焦距和视场。
(5)本发明通过基带混频的方式产生高纯度、低相噪基带信号，保证被动相参、主动非相参、主动相参三个工作模式的系统灵敏度。
附图说明
通过阅读下文优选实施方式的详细描述，各种其他的优点和益处对于本领 域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本发明的限制。而且在整个附图中，用相同的参考符号表示相同的部件。在附图中：
图1为太赫兹多模实时成像系统的系统框图。
图2为太赫兹准光透镜组的组成示意图
图3为太赫兹焦平面成像阵列前端的结构示意图。
图4为太赫兹焦平面成像阵列前端的子阵列拼接示意图。
图5为太赫兹焦平面成像阵列像元的结构示意图。
图6为中频读出电路的拓扑框图。
具体实施方式
下面将参照附图更详细地描述本公开的示例性实施例。虽然附图中显示了本公开的示例性实施例，然而应当理解，可以以各种形式实现本公开而不应被这里阐述的实施例所限制。相反，提供这些实施例是为了能够更透彻地理解本公开，并且能够将本公开的范围完整的传达给本领域的技术人员。需要说明的是，在不冲突的情况下，本发明中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
本实施例提供了一种太赫兹多模实时成像微系统，所述系统包括太赫兹准光馈入模块1、太赫兹焦平面成像阵列前端模块2、中频读出电路3、信号处理与控制模块4、显示模块5、基带信号产生模块6、太赫兹发射信号与本振信号模块7，如图1所示。
太赫兹准光馈入模块1包括太赫兹准光透镜组11和伺服控制单元12，以及控制接口4112。
太赫兹焦平面成像阵列前端模块2包括太赫兹微透镜阵列21、太赫兹焦平面阵列芯片22、中频输出网络23和本振功率分配网络24。
中频读出电路3包括矩阵开关31和读出电路阵列32，以及控制接口4131。
信号处理与控制模块4包括控制指令单元41和信号处理单元42，以及控制接口4112，控制接口4131，控制接口4161，控制接口4173和控制接口4174。
显示模块5包括显示屏幕51和人工控制单元52。
基带信号产生模块6包括基带信号控制单元61、直接数字式频率合成器62、时钟63、×D倍频器64，基带混频器65、×E倍频器66，以及控制接口4161。
太赫兹发射信号与本振信号模块7包括×N倍频器71、第一驱动放大器72、第一单刀双掷开关73、第二单刀双掷开关74、耦合器75、驱动放大器76、×M倍频器77和太赫兹喇叭天线78，以及控制接口4173和控制接口4174。
【系统各部分主要功能】
太赫兹准光馈入模块1用于接收目标的太赫兹信号Rx，并将信号传递给太赫兹焦平面成像阵列前端模块2。
太赫兹焦平面成像阵列前端模块2用于将接收到的太赫兹信号转变为太赫兹电流，并将太赫兹电流降频至中频信号IFx。中频信号IFx将传递给中频读出电路3。
中频读出电路3用于读出太赫兹焦平面成像阵列前端模块2输出的中频信号IFx，并将中频信号做进一步放大和模-数转换，输出数字信号Dx。数字信号Dx将传递给信号处理与控制模块4。
信号处理与控制模块4用于处理数字信号生成图像并分析目标特征，并将图像传递给显示模块5。另外，信号处理与控制模块4还用于产生控制指令，用于以下三个控制功能：
控制太赫兹准光馈入模块1中的伺服控制单元12，进而实现太赫兹准光透镜组11的焦距和视场变换；
控制中频读出电路3中的矩阵开关31进而控制太赫兹焦平面成像阵列前端模块2中的像元读出顺序；
控制基带信号产生模块6中的基带信号控制单元61，用于产生基带信号波形。
显示模块5用于显示目标和环境的太赫兹图像并提供人工控制接口。
基带信号产生模块6用于产生基带信号Bx并传递给太赫兹发射信号与本振信号模块7。
太赫兹发射信号与本振信号模块7的输入信号由基带信号产生模块6提供，通过倍频和放大方式产生本振信号LOx以及太赫兹发射信号Tx。本振信号传递给太赫兹焦平面成像阵列前端模块2作为本振参考信号。太赫兹发射信号经由太赫兹喇叭天线78照射到目标上。
【模块1-太赫兹准光馈入模块】
太赫兹准光透镜组11至少由三个太赫兹准光透镜组成，依次记为透镜111、透镜112……透镜11(N-1)、透镜11N。透镜111位于系统最外侧，透镜11N位于靠近太赫兹焦平面成像阵列前端模块2一侧。太赫兹准光透镜所采用的材料在太赫兹频段的透射率不小于0.8且其介电常数不大于5，例如聚四氟乙烯材料。所有太赫兹准光透镜的光轴位于同一直线上。透镜111的位置固定不变；透镜112……透镜11N的位置可以沿着光轴方向移动，位移由伺服控制单元12控制，由此实现焦距和视场的调节，如图2所示。
【模块2-太赫兹焦平面成像阵列前端模块】
太赫兹微透镜阵列21和太赫兹焦平面阵列芯片22共同实现太赫兹空间信号的感应以及变频处理。中频输出网络23用于读出太赫兹焦平面阵列芯片22输出的中频信号。本振功率分配网络24用于为太赫兹焦平面阵列芯片22中的检波/混频天线单元220提供点到点的本振功率，如图3所示。
太赫兹微透镜阵列21中的微透镜单元210为介质扩展半球，即由半球和圆柱组成。介质扩展半球用于优化太赫兹焦平面阵列芯片22中基本像元的方向性，提升基本像元的的辐射增益。其中半球的半径为R；圆柱的高度为L，横截面半径为R。扩展半球的材料在太赫兹频段的透射率不小于0.8，介电常数不大于5，从而减小太赫兹微透镜阵列21和太赫兹焦平面阵列芯片22之间的阻抗失配损耗。微透镜单元210紧密排布，形成二维复眼阵列结构，其阵列规模记为A×B。
太赫兹焦平面阵列芯片22中的基本单元为检波/混频天线单元220，如图2所示。检波/混频天线的特征是采用差分式天线为基本辐射单元，例如偶极子、蝶形天线、对数周期天线等；采用二极管为变频单元，二极管位于差分式天线的射频馈电端口处。差分式天线用于将太赫兹辐射转变为太赫兹电流并传递给二极管。二极管将太赫兹电流转变为低频电流。若二极管加载了本振信号，则检波/混频天线工作于混频模式；若二极管没有加载本振信号，则检波/混频天线工作于检波模式。低频电流通过差分天线两端输出。进一步地，为了提高检波/混频天线的变频效率且太赫兹焦平面阵列芯片中的基本单元尺寸保持在1个平方波长内(1λ 2，λ为太赫兹信号的波长)，本发明提出一种紧凑型检波/混频检波天线单元结构。其基本特征是：①采用偶极子天线及其变形(以下统称为“偶极子天线”)为基本辐射单元，典型长度为λ/2；②在偶极子天线射频馈电端口处可以加载平行于偶极子边缘的电耦合带状线，典型宽度λ/20～λ/10，典型长度为λ/8～λ/3，从而扩展偶极子天线的带宽；③在偶极子天线两端加载带阻滤波器，其阻带中心频率为f Signal(f Signal为太赫兹信号的工作频率)，该滤波器在太赫兹多模实时成像系统的本振带宽和中频带宽内为通带；④带阻滤波器的典型实现方式为“凹”字形或者“工”字形缝隙，其内凹部分面向射频馈电端口，其突出优点是避免使偶极子天线产生副瓣电平且尺寸很小，通过级联多个尺寸不同的“凹”字缝隙和“工”字形缝隙可以控制阻带带宽；⑤为了满足太赫兹频段信号检测需求，二极管的最佳选择为平面型太赫兹肖特基二极管，其结电容不大于2fF，且其级联电阻不大于5Ω；⑥为了减小太赫兹频段的损耗以及检波/混频天线单元220间的串扰，检波/混频天线采用衬底材料的介质损耗角正切tanδ不大于0.001，介电常数ε r不大于5，厚度不大于λ/[100·(ε r) 1/2]，典型材料为石英。
太赫兹焦平面阵列芯片22中的基本像元间距D为λ～5λ。太赫兹微透镜阵列21中微透镜的直径等于太赫兹焦平面阵列芯片22中的基本像元间距，即D＝2R。太赫兹焦平面阵列芯片22的阵列规模为A×B，与太赫兹微透镜阵列21 的阵列规模保持一致。太赫兹焦平面阵列芯片22的介质一侧与像元与太赫兹微透镜阵列21的平面一侧紧密贴合。太赫兹焦平面阵列芯片22的像元与太赫兹微透镜阵列21的微透镜保持一一对应的空间关系，且像元中心位于微透镜轴线上。
中频输出网络23采用微同轴结构作为基本传输线，用于太赫兹焦平面阵列芯片22的中频信号输出，网络的阵列规模为A×B，与太赫兹焦平面阵列芯片22的阵列规模保持一致。微同轴结构的基本特征是①包含外导体和内导体，其中内导体与检波/混频天线单元220的一侧电气相连；②微同轴内导体和外导体截面形状为圆形或者方形，直径分别为a和b，满足(a+b)≤λ，保证微同轴在中频处不会产生高次模。
本振功率分配网络24采用波导作为基本传输线，包括A×B个本振功率分配支路240。本振功率分配网络24包括一个本振输入端口231，A×B个本振输出端口242。本振输入端口231为标准波导结构。太赫兹发射信号与本振信号模块7通过本振输入端口231馈入本振信号。本振输出端口242为非标准波导，工作于TE模式，且电场方向与检波/混频天线单元220中的偶极子天线极化方向一致。检波/混频天线单元220中的二极管位于本振输出端口242的中心位置。
如图5所示，太赫兹焦平面成像阵列前端模块2中的像元20包括微透镜单元210、检波/混频天线单元220、中频输出支路230和本振功率分配支路240。检波/混频天线单元220位于微透镜单元210和本振功率分配支路240之间。太赫兹信号Tx通过微透镜单元210输入到检波/混频天线单元220上，本振信号LOx通过本振功率分配支路240输入到检波/混频天线单元220上。
图4给出了太赫兹焦平面成像阵列前端的子阵列拼接示意图。若将一个阵列规模为A×B的太赫兹焦平面成像阵列前端作为一个子阵，则通过二维拼接方式，在行方向有M个子阵，列方向上有N个子阵，可以形成一个更大规模的太赫兹焦平面阵列前端，其阵列规模为(M×A)×(N×B)。
【模块3-中频读出电路】
中频读出电路3中的矩阵开关31用于选通中频输出网络23，实现中频信号IFx的有序输出，阵列规模为A×B，与中频输出网络23的阵列规模保持一致。矩阵开关31通过控制接口4131接受控制指令单元41的控制，根据行列控制单元311选通相应的行与列，将中频信号IFx传递给读出电路阵列32。读出电路阵列32的通道数为P(P≤A×B)，如图6所示，每个通道至少包含功率放大器321和模数转换器322。功率放大器321用于放大中频信号，模数转换器322用于将放大后的中频信号转换为数字信号。读出电路阵列32输出的数字信号传递给信号处理与控制模块4。
【模块4-信号处理与控制模块】
控制指令单元41包括五个控制接口，分别是控制接口4112，控制接口4131，控制接口4161，控制接口4173，控制接口4174。控制指令单元41接受人工控制单元52的控制。
【模块6-基带信号产生模块】
基带信号控制单元61输出基带输出信号和时钟63的时钟信号(频率为f 603)同时输入至直接数字式频率合成器62，输出信号为合成信号(频率为f 602)。时钟信号输入至×D倍频器64，输出为D倍频信号(频率为f 604＝D·f 603)和D倍频信号输入至基带混频器65，输出信号为混频信号(频率为f 605，且f 605＝f 604-f 602)。混频信号输入×E倍频器66，输出信号为信号606(频率为f 606，且f 606＝E·f 605)。经过该模块产生的基带信号具有相位噪声小、频谱纯的特点。
【模块7-太赫兹发射信号与本振信号模块】
信号606输入至×N倍频器71，输出信号为N倍频信号(频率为f 701，且f 701＝N·f 606)。N倍频信号输入至第一驱动放大器72，输出信号为第一放大信号(频率为f 702，且f 702＝f 701)。第一放大信号经过第一单刀双掷开关73选择经过通道73A或者73B。若第一放大信号经过通道73A，则第一放大信号直接馈入本振功率分配网络24。若第一放大信号经过通道73B，则经过第二单刀双掷开关74选择经过通道74A或者通道74B。若第一放大信号经过通道74A，则输 入至耦合器75，分别输入至×M倍频器77和驱动放大器76。若第一放大信号经过通道74B，则直接输入至×M倍频器77，输出信号为M倍频信号(频率为f 707，且f 707＝M·f 702)。经过×M倍频器77的信号通过太赫兹喇叭天线78发射到自由空间中。
【系统四种工作模式】
太赫兹多模实时成像系统具有四种工作模式：模式1-被动非相参模式、模式2-被动相参模式、模式3-主动非相参模式、模式4-主动相参模式。四种工作模式的切换由人工控制单元52通过控制指令单元41给基带信号产生模块6和太赫兹发射信号与本振信号模块7发送指令实现。
被动非相参模式：若控制接口4161接收到关闭指令，基带信号产生模块6和太赫兹发射信号与本振信号模块7停止工作，则太赫兹多模实时成像系统工作于被动非相参模式。
被动相参模式：若控制接口4161接收到开启指令，并且控制接口4173给第一单刀双掷开关73发送指令使通道73A导通而通道73B断开，则太赫兹多模实时成像系统工作于被动相参模式。
主动非相参模式：若控制接口4161接收到开启指令，并且控制接口4173给第一单刀双掷开关73发送指令使通道73A断开而通道73B导通，并且控制接口4174给第二单刀双掷开关74发送指令使通道74B导通而通道74A断开，则太赫兹多模实时成像系统工作于主动非相参模式。
主动相参模式：若控制接口4161接收到开启指令，并且控制接口4173给第一单刀双掷开关73发送指令使通道73A断开而通道73B导通，并且控制接口4174给第二单刀双掷开关74发送指令使通道74A导通而通道74B断开，则太赫兹多模实时成像系统工作于主动相参模式。
【工作方式】
太赫兹多模实时成像系统的工作方式如下：
首先，依次启动显示模块5、信号处理与控制模块4、中频读出电路3、太 赫兹焦平面成像阵列前端模块2和太赫兹准光馈入模块1。太赫兹多模实时成像系统进入被动非相参工作模式，进入全天候静默监视阶段。
其次，在全天候静默监视阶段，若无异常情况发生，以T0为周期，周期性启动基带信号产生模块6和太赫兹发射信号与本振信号模块7，选通通道73A。太赫兹多模实时成像系统进入被动相参工作模式。由此可以周期性提升系统灵敏度和作用距离。
在全天候静默监视阶段，若由于环境因素导致图像对比度变差，则启动基带信号产生模块6和太赫兹发射信号与本振信号模块7，选通通道73B和74B。太赫兹多模实时成像系统进入主动非相参工作模式。
在全天候静默监视阶段，若发现异常情况，则选通通道73B和通道74A。太赫兹多模实时成像系统进入主动相参工作模式，实施对目标的成像与跟踪。同时，伺服控制单元12根据控制接口4112的指令调整太赫兹准光透镜组11的焦距和视场，实施对目标的高分辨率成像。
然后，若排除疑似危险目标后，则停用基带信号产生模块6和太赫兹发射信号与本振信号模块7，再次进入被动非相参工作模式，进入全天候静默监视阶段。
本实施例通过采用太赫兹准光馈入模块输入目标和环境的太赫兹信号、通过太赫兹焦平面成像阵列前端模块将太赫兹信号转变为中频信号，以及通过发射和本振信号的通路切换实现被动非相参、被动相参、主动非相参、主动相参四个工作模式的灵活切换；本实施例通过采用基于太赫兹肖特基二极管的太赫兹焦平面阵列芯片以及本振功率分配网络实现相参接收和非相参接收模式的切换，并解决同时实现凝视成像和获取相位信息之间的矛盾；本实施例中的太赫兹焦平面成像阵列芯片采用扁平化紧凑型太赫兹像元形成二维高密度阵列，有利于实现阵列规模的灵活设计以及不同规模子阵的灵活拼接；本实施例通过用伺服控制单元控制太赫兹准光透镜组中透镜间的相对位置控制成像焦距和视场；本实施例通过基带混频的方式产生高纯度、低相噪基带信号，保证被动相参、 主动非相参、主动相参三个工作模式的系统灵敏度。
以上所述的实施例只是本发明较优选的具体实施方式，本领域的技术人员在本发明技术方案范围内进行的通常变化和替换都应包含在本发明的保护范围内。

Claims (10)

  1. 一种太赫兹多模实时成像系统，其特征在于包括：太赫兹准光馈入模块(1)、太赫兹焦平面成像阵列前端模块(2)、中频读出电路(3)、信号处理与控制模块(4)、显示模块(5)、基带信号产生模块(6)和太赫兹发射信号与本振信号模块(7)；其中，
    所述太赫兹准光馈入模块(1)用于接收目标的太赫兹信号，并将太赫兹信号传递给所述太赫兹焦平面成像阵列前端模块(2)；
    所述太赫兹焦平面成像阵列前端模块(2)用于将接收到的太赫兹信号转变为太赫兹电流，并将太赫兹电流降频至中频信号，并将中频信号将传递给所述中频读出电路(3)；
    所述中频读出电路(3)用于读出所述太赫兹焦平面成像阵列前端模块(2)输出的中频信号，并将中频信号做进一步放大和模-数转换，输出数字信号，并将数字信号将传递给所述信号处理与控制模块(4)；
    所述信号处理与控制模块(4)用于接收并处理数字信号生成图像，并将图像传递给所述显示模块(5)；
    所述显示模块(5)用于接收并显示图像并提供人工控制接口；
    所述基带信号产生模块(6)用于产生基带信号并传递给所述太赫兹发射信号与本振信号模块(7)；
    所述太赫兹发射信号与本振信号模块(7)将基带信号通过倍频和放大方式产生本振信号以及太赫兹发射信号，其中，本振信号传递给所述太赫兹焦平面成像阵列前端模块(2)作为本振参考信号，太赫兹发射信号照射到目标上。
  2. 根据权利要求1所述的太赫兹多模实时成像系统，其特征在于：所述太赫兹准光馈入模块(1)包括太赫兹准光透镜组(11)和伺服控制单元(12)；其中，
    所述太赫兹准光透镜组(11)和所述伺服控制单元(12)相连接，所述伺 服控制单元(12)控制所述太赫兹准光透镜组(11)的位移，实现太赫兹准光透镜组(11)的焦距和视场的调节；
    所述太赫兹准光透镜组(11)用于接收目标的太赫兹信号，并将太赫兹信号传递给所述太赫兹焦平面成像阵列前端模块(2)。
  3. 根据权利要求1所述的太赫兹多模实时成像系统，其特征在于：所述太赫兹焦平面成像阵列前端模块(2)包括太赫兹微透镜阵列(21)、太赫兹焦平面阵列芯片(22)、中频输出网络(23)和本振功率分配网络(24)；其中，
    所述太赫兹微透镜阵列(21)和所述太赫兹焦平面阵列芯片(22)作为整体，用于将接收到的太赫兹信号转变为太赫兹电流，并将太赫兹电流降频至中频信号；
    所述中频输出网络(23)用于读出太赫兹焦平面阵列芯片(22)输出的中频信号；
    所述本振功率分配网络(24)用于为太赫兹焦平面阵列芯片(22)中的检波/混频天线单元(220)提供点到点的本振功率。
  4. 根据权利要求1所述的太赫兹多模实时成像系统，其特征在于：所述中频读出电路(3)包括矩阵开关(31)和读出电路阵列(32)；其中，
    所述矩阵开关(31)接受控制指令单元(41)的控制，选通相应的行与列，将中频信号传递给所述读出电路阵列(32)；
    所述读出电路阵列(32)包括与所述矩阵开关(31)的阵列规模相对应数量的通道，其中，每个通道包含功率放大器(321)和模数转换器(322)，其中，功率放大器(321)用于放大中频信号，模数转换器(322)用于将放大后的中频信号转换为数字信号，并将数字信号传递给信号处理与控制模块(4)。
  5. 根据权利要求1所述的太赫兹多模实时成像系统，其特征在于：所述信号处理与控制模块(4)包括控制指令单元(41)和信号处理单元(42)；其中，
    所述信号处理单元(42)用于接收并处理数字信号生成图像并分析目标特征，并将图像传递给所述显示模块(5)；
    控制指令单元(41)用于产生控制指令，用于控制太赫兹准光馈入模块(1)中的伺服控制单元(12)，进而实现太赫兹准光透镜组(11)的焦距和视场变换；用于控制中频读出电路(3)中的矩阵开关(31)进而控制太赫兹焦平面成像阵列前端模块(2)中的像元读出顺序；用于控制基带信号产生模块(6)中的基带信号控制单元(61)，用于产生基带信号波形。
  6. 根据权利要求4所述的太赫兹多模实时成像系统，其特征在于：所述显示模块(5)包括显示屏幕(51)和人工控制单元(52)；其中，
    所述人工控制单元(52)用于控制所述控制指令单元(41)；
    所述显示屏幕(51)用于接收并显示图像。
  7. 根据权利要求1所述的太赫兹多模实时成像系统，其特征在于：所述基带信号产生模块(6)包括基带信号控制单元(61)、直接数字式频率合成器(62)、时钟(63)、×D倍频器(64)、基带混频器(65)和×E倍频器(66)；其中，
    所述基带信号控制单元(61)的基带输出信号和所述时钟(63)的时钟信号同时输入至所述直接数字式频率合成器(62)；
    所述直接数字式频率合成器(62)将基带输出信号和时钟信号合成后得到合成信号，并将合成信号输入至所述基带混频器(65)；
    所述×D倍频器(64)接收时钟信号并处理得到D倍频信号，并将D倍频信号输入至基带混频器(65)；
    所述基带混频器(65)接收D倍频信号和合成信号，并处理得到混频信号，并将混频信号输入至×E倍频器(66)；
    所述×E倍频器(66)接收混频信号并处理得到E倍频信号，并将E倍频信号输入至所述太赫兹发射信号与本振信号模块(7)。
  8. 根据权利要求7所述的太赫兹多模实时成像系统，其特征在于：所述太赫兹发射信号与本振信号模块(7)包括×N倍频器(71)、第一驱动放大器(72)、第一单刀双掷开关(73)、第二单刀双掷开关(74)、耦合器(75)、第二驱动放大器(76)、×M倍频器(77)和太赫兹喇叭天线(78)；其中，
    所述×N倍频器(71)接收E倍频信号并处理得到N倍频信号，并将N倍频信号输入至所述第一驱动放大器(72)；
    所述第一驱动放大器(72)接收N倍频信号并处理得到第一放大信号；
    第一放大信号经过第一单刀双掷开关(73)选择经过通道73A或者通道73B；若第一放大信号经过通道73A，则第一放大信号直接馈入本振功率分配网络(24)；若第一放大信号经过通道73B，则经过第二单刀双掷开关(74)选择经过通道74A或者通道74B；
    若第一放大信号经过通道74A，则经过耦合器(75)分别输入至×M倍频器(77)和第二驱动放大器(76)，所述第二驱动放大器(76)将第一放大信号直接馈入本振功率分配网络(24)；若第一放大信号经过通道74B，则直接输入至×M倍频器(77)，所述×M倍频器(77)接收第一放大信号并处理得到M倍频信号，并将M倍频信号通过所述太赫兹喇叭天线(78)发射到自由空间中。
  9. 根据权利要求7所述的太赫兹多模实时成像系统，其特征在于：所述基带输出信号的频率为f 601，所述时钟信号的频率为f 603，合成信号的频率为f 602＝f 601+f 603；
    D倍频信号的频率为f 604＝D·f 603，混频信号的频率为f 605＝f 604-f 602，E倍频信号的频率为f 606＝E·f 605。
  10. 根据权利要求8所述的太赫兹多模实时成像系统，其特征在于：所述N倍频信号的频率为f 701＝N·f 606，第一放大信号的频率为f 702＝f 701，M倍频信号的频率为f 707＝M·f 702。
PCT/CN2019/095548 2018-12-13 2019-07-11 太赫兹多模实时成像系统 WO2020119106A1 (zh)

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