CN104569980A - Ground terahertz radar system for detecting cloud - Google Patents
Ground terahertz radar system for detecting cloud Download PDFInfo
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- G—PHYSICS
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- 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
- G01S13/95—Radar or analogous systems specially adapted for specific applications for meteorological use
- G01S13/951—Radar or analogous systems specially adapted for specific applications for meteorological use ground based
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Abstract
The invention discloses a ground terahertz radar system for detecting a cloud. The system comprises a terahertz transmitting module, a terahertz receiving module, a terahertz transmitting-and-receiving antenna module, a terahertz signal processing module and an upper computer module; the center frequency of a terahertz signal transmitted by the terahertz transmitting module is 220 GHz, the work bandwidth is 5 GHz, the transmitting power is 200 mW, the pulse width is adjustable ranging from 100ns to 3mus and the adjusted step length is 100ns, and the pulse repletion frequency is adjustable ranging from 1KHz to 10KHz and the adjusted step length is 1KHz. Compared with a laser radar and a millimeter wave radar, the ground terahertz radar system for detecting the cloud utilizes a set of parameters applicable to the cloud detection and is capable of penetrating into a thin cloud and an extremely thin cloud to carry out the three-dimensional structure detection for the cloud, and therefore not only a macrostructure such as the cloud thickness, the cloud height, the number of cloud layers, the vertical section variance of the cloud can be obtained, but also a microstructure such as the size, the shape, and the ice water content of a cloud particle can be obtained.
Description
Technical field
The present invention relates to Radar Technology field, particularly relating to a kind of ground Terahertz radar system for surveying cloud.
Background technology
Cloud is most important in global climate model is also one of the most doubt meteorological element, and it has vital role to earth energy equilibrium, climate change and weather modification.Cloud, by affecting solar shortwave radiation and earth long-wave radiation, controls earth energy budget.The distribution character of cloud and the monitoring of evolution motion process thereof have very important effect for research Global climate change, weather forecast etc.
The means mainly microwave radar of cloud is surveyed in current research, specifically comprises microwave radiometer, machine throws sonde and millimeter wave cloud detection radar etc.Wherein, sonde thrown by microwave radiometer and machine can obtain certain cloud information, but can not penetrate spissatus top layer detects its vertical dimension and inner structure, can not obtain the microscopic characteristics such as the size and shape of cloud particle, ice water content.
Sonde is thrown compared to microwave radiometer and machine, millimetre-wave radar has more high detection sensitivity to cloud particle, there is the ability penetrating cloud, therefore macroscopically the cloud external structures such as cloud is thick, the cloud level not only can be described, the cloud internal physical structure of cloud layer number, vertical section change etc. can also be described; And the millimeter wave that millimetre-wave radar sends is more close to the yardstick of cloud particle, and it utilizes cloud particle to electromagnetic scattering properties, by analyzing the microscopic characteristics of cloud to cloud radar return, comprises the information such as the size of cloud particle, shape, ice water content.First millimeter wave cloud detection radar satellite---the CloudSat that NASA in 2004 succeeds in sending up, cloud section radar (the cloud profilingradar of the Main Load of this satellite to be exactly a service band be 94GHz, be called for short CPR), for realizing the measurement of cloud layer internal information.But millimetre-wave radar is relatively more effective for spissatus detection, and because it is excessively strong to the cloud particle penetrability that particle diameter is less, echo strength is more weak, therefore not good to thin cloud Effect on Detecting, even cannot detect.
Another means of research cloud are laser radars, and such as CALIPSO laser radar provides the thin ice cloud information on top, a large amount of troposphere.But laser penetration power is more weak, only can measure cloud layer surface, cannot obtain cloud internal information.
But existing cloud measurement means also has some limitations:
(1) microwave radar is excessively strong to the cloud particle penetrability that particle diameter is less, and echo strength is more weak, even cannot detect thin cloud and very thin cloud;
(2) laser radar penetration power is more weak, only can measure cloud layer surface, therefore only can provide cloud layer surface information, can not stretch into the three-dimensional detection that cloud structure is done in cloud inside;
(3) for very thin cloud and the change of Cloudless atmosphere particulate, cloudlike particle size and shape, cloud particle, ice water content carries out high-precision detection and inverting, need wavelength closer to the detection system of particulate yardstick, and more high resolving power and sensitivity are provided.
Along with the application of cloud means surveyed by millimeter wave cloud detection radar etc., next atmospheric window frequency range becomes inexorable trend for surveying cloud.In recent years, along with the development of THz source technology, THz wave (0.1THz ~ 10THz) has potential and important science and using value in the application such as aerological sounding, causes the interest of relevant scholar, becomes new research direction.
Summary of the invention
In view of this, the invention provides a kind of ground Terahertz radar system for surveying cloud, it realizes thin cloud and the detection of very thin cloud internal structure external structure, and can provide more high resolving power and sensitivity.
In order to solve the problems of the technologies described above, the present invention is achieved in that
For surveying a ground Terahertz radar system for cloud, comprising: terahertz sources module, Terahertz receiver module, Terahertz dual-mode antenna module, terahertz signal processing module and upper computer module;
Terahertz sources module, the intermediate-freuqncy signal source produced for utilizing Terahertz receiver module completes generation and the power amplification of terahertz signal, is then launched by Terahertz dual-mode antenna module; The centre frequency of the terahertz signal launched is 220GHz, bandwidth of operation is 5GHz, emissive power is 200mW, and pulse width is adjustable within the scope of the μ s of 100ns ~ 3 and regulates step-length to be 100ns, and pulse repetition rate is adjustable within the scope of 1KHz ~ 10KHz and regulates step-length to be 1KHz;
Terahertz receiver module, for complete the generation of derived reference signal, intermediate-freuqncy signal source generation, to the down coversion of the Terahertz echoed signal that Terahertz dual-mode antenna module receives and secondary intermediate frequency process, then send to terahertz signal processing module; The centre frequency of this Terahertz receiver module is 220GHz, and bandwidth of operation is 5GHz, and receiving sensitivity is better than-80dBm, and dynamic range is better than 60dB;
Terahertz signal processing module, for realizing collection, the storage of the secondary intermediate-freuqncy signal of Terahertz echo and processing;
Upper computer module communicates with Terahertz receiver module with terahertz signal processing module respectively, controls with frequently comprehensive to realize data transmission.
Preferably, this system comprises Terahertz internal calibration module further, this Terahertz internal calibration module obtains the terahertz signal of transmitting from terahertz sources module, and the down-converted identical with Terahertz receiver module is carried out to it, then send to Terahertz receiver module to carry out secondary intermediate frequency process, the internal calibration secondary intermediate-freuqncy signal of acquisition sends to terahertz signal processing module; Whether terahertz signal processing module checks the emissive power of terahertz sources signal and frequency to offset according to internal calibration secondary intermediate-freuqncy signal further, according to the amplifying power of transmit power offset value adjustment terahertz sources module, according to the generation in the intermediate-freuqncy signal source of frequency skew adjustment Terahertz receiver module.
Preferably, described terahertz sources module comprises Terahertz frequency multiplication link, Terahertz power amplifier and coupling mechanism;
Described Terahertz frequency multiplication link, the intermediate-freuqncy signal source frequency multiplication for being produced by Terahertz receiver module obtains the signal of Terahertz frequency range, frequency multiplication adopts the cascade system of two frequency multiplication+two frequencys multiplication+frequency triplings to realize: the frequency that first receiving Terahertz receiver module provides is 18.33GHz ± 0.208GHz, power is the signal of 0dBm, the output of 73.2GHz ± 0.832GHz is obtained by the E wave band quadrupler of two varactor doubler composition and E band filter, then 73.2GHz ± 0.832GHz is obtained through E band power compositor, power is the output of 300mW, finally drive 220GHz frequency tripler, finally 220GHz ± 2.5GHz is realized by frequency tripler, power is transmitting of 10mW, be transmitted to Terahertz power amplifier,
Wherein, E wave band quadrupler is made up of two varactor doublers, Ka varactor doubler and E wave band varactor doubler respectively, the signal frequency multiplication of 18.33GHz ± 0.208GHz is frequency by Ka varactor doubler is 36.666GHz ± 1GHz signal, then is the signal of 73.333GHz ± 0.832GHz by E wave band varactor doubler frequency multiplication;
Terahertz power amplifier, carries out power amplification for the terahertz signal exported by Terahertz frequency multiplication link;
Coupling mechanism, the signal for being produced by Terahertz power amplifier exports to Terahertz dual-mode antenna module and Terahertz internal calibration module.
Preferably, described Terahertz receiver module comprises referrer module, secondary ifd module, local oscillator module and down coversion receiver module;
Referrer module, for producing reference frequency source for Terahertz receiver module, reference frequency source is 100MHz;
Local oscillator module, for producing intermediate-freuqncy signal source for Terahertz receiver module and terahertz sources module; This local oscillator module is passed through by the Frequency Hopping Signal of 2.18GHz ~ 3.203GHz by being divided into two-way after amplifier F0 and power splitter G1 process, and a road is device L1, amplifier F1, frequency mixer H1, wave filter L2, the rear signal output producing 1 road 17.83GHz ~ 18.853GHz of amplifier F2 process after filtering successively; Another road signal produced after power splitter G1 process successively after filtering after device L3, amplifier F3, frequency mixer H2, wave filter L4, amplifier F4 process through being produced the signal output of 2 road 17.74GHz ~ 18.763GHz by power splitter G2; Wherein the signal of 17.83GHz ~ 18.853GHz exports to terahertz sources module, as the intermediate-freuqncy signal source of terahertz sources module; The signal of 17.74GHz ~ 18.763GHz exports to down coversion receiver module and Terahertz internal calibration module, as the intermediate-freuqncy signal source of down coversion receiver module and Terahertz internal calibration module;
Down coversion receiver module, the Terahertz radar for obtaining receiving antenna in Terahertz dual-mode antenna module is surveyed cloud echo signal and is carried out down coversion;
Secondary ifd module, the 1020MHz signal produced for the 1080MHz of Terahertz receiver module or Terahertz internal calibration module being exported and fixed local vibration source carries out mixing and obtains 60MHz bis-intermediate-freuqncy signals, exports to terahertz signal processing module.
Preferably, described down coversion receiver module, the signal of the 17.74GHz ~ 18.763GHz produced from local oscillation signal exports and extracts the signal of 18.04GHz ~ 18.45GHz after frequency tripler, wave filter L5, amplifier F5, wave filter L6, amplifier F6, varactor doubler, carries out the secondary intermediate frequency that mixing obtains 1080MHz export with the echoed signal of the 217.56GHz ~ 222.48GHz received by Terahertz receiving antenna module.
Preferably, described Terahertz dual-mode antenna module comprises terahertz sources antenna and Terahertz receiving antenna; When being applied to high mountain mountain top survey cloud, the form of terahertz sources antenna and Terahertz receiving antenna is Cassegrain antenna, and Cassegrain antenna gain is 50dBi, and beam angle is not more than 0.7 °; When being applied to simulation cloud chamber, the form of terahertz sources antenna and Terahertz receiving antenna is electromagnetic horn, and the receiving antenna gain in electromagnetic horn is 30dBi, and beam angle is 8 °.Transmitter antenna gain (dBi) in electromagnetic horn is 20dBi, and beam angle is 15 °.
Preferably, described terahertz signal processing module comprises analog to digital converter, storer A, storer B, FPGA, DSP and Gigabit Ethernet module; Analog to digital converter, storer B, DSP are all connected with FPGA with Gigabit Ethernet module, and storer A and DSP is connected; Analog to digital converter adopts AD9254 chip, and FPGA adopts Altera EP2S90F1020 chip, and DSP adopts TMS320C6455 chip, and storer B adopts 128MB SDRAM, and storer A adopts 512MB DDR2.
Beneficial effect:
Compared to laser radar and millimetre-wave radar, Terahertz cloud detection radar system of the present invention have employed the parameter that a group is applicable to cloud detection, the deep enough thin cloud of energy and very thin cloud carry out the stereoscopic three-dimensional structure detection of cloud, thus can not only cloud thick, the cloud level, cloud layer number, the macrostructure such as vertical section change, the micromechanisms such as the size of cloud particle, shape, ice water content can also be obtained.
And the wavelength of terahertz signal is closer to cloud particle yardstick, and cloud particle reflection echo has better directivity, meticulousr stereoscopic three-dimensional structure detection can be carried out to cloud layer, thus improve systemic resolution and sensitivity.
In addition, higher radar frequency makes to have better correlativity between ice water content (IWC) and reflectivity (Z), improve the precision of cloud layer ice water content inverting, to monitor for the inverting of cloud product and clear-air turbulence of carrying out closing to reality more and estimation improves basis.
Its using value of the present invention embodies and is: the subtle three-dimensional vertical stratification 1. detecting cloud layer, contributes to understanding cloud how to affect locality or large scale atmospheric condition and cloud to the influencing mechanism of radiation environment.2. the effect of qualitative assessment weather and climate Forecast Mode medium cloud, and then the quality improving weather and climate forecast.
Accompanying drawing explanation
Fig. 1 is the composition frame chart of Terahertz cloud detection radar system;
Fig. 2 is the schematic diagram of Terahertz frequency multiplication link;
Fig. 3 is the schematic diagram of local oscillator module in Terahertz receiver module;
Fig. 4 is the schematic diagram of down coversion receiver module (Terahertz internal calibration module);
Fig. 5 is the schematic diagram of terahertz signal processing module.
Embodiment
To develop simultaneously embodiment below in conjunction with accompanying drawing, describe the present invention.
The centre frequency of terahertz signal can be 110GHz, 150GHz, 220GHz, 340GHz, bandwidth of operation is 300MHz ~ 5GHz (resolution reaches as high as 3cm), power stage is 200mW ~ 100W, pulse width is 100ns ~ 3 μ s (step-length is 100ns), and pulse repetition rate (PRF) is 1 ~ 10KHz (step-length is 1KHz).
The parameter of Terahertz radar system needs to carry out making a concrete analysis of and screening for the feature of cloud.
(1) centre frequency is determined
Different detection frequency range is different to the susceptibility of meteorological target.At atmospheric window places such as above-mentioned 110GHz, 150GHz, 220GHz and 340GHz, decay relatively little, the one-way attenuation of every kilometer is about 5 ~ 6dB, and along with the increase of sea level elevation, atmosphere moisture content reduces rapidly, the atmospheric attenuation of terahertz wave band also declines fast, therefore preferential at above-mentioned atmospheric window place selection transmitting frequency.Meanwhile, 110GHz, 150GHz launch window due to wavelength longer, penetrability is excessively strong, and echo strength is more weak, cannot meet the detectivity to thin cloud and very thin cloud; And 340GHz atmospheric window due to transmission frequency too high, current THz devices development level is limited, therefore is chosen to be 220GHz to detect the Terahertz radar center frequency that cloud is fundamental purpose in the present invention.
(2) power stage is determined
When surveying cloud, need to consider radar horizon.In general, the distance that cloud is surveyed on ground is 1000m ~ 1500m, and Terahertz radar of the present invention also needs to carry out cloud measurement test at simulation cloud chamber and high mountain mountain top, therefore needs the power stage of the radar weather equation determination terahertz signal according to practical application Distance geometry formula (1).
Being defined as follows of parameter in above formula:
P
r: the mean value (W) of the echo power that radar receives
P
t: radar transmitted pulse power (W)
G: the actual gain (dBi) of radar antenna
θ: antenna horizontal beam width (rad)
antennas orthogonal beam angle (rad)
τ: fire pulse width (s)
λ: radar operation wavelength (m)
C: electromagnetic wave propagation speed 3x10
8(m/s)
K: the decay factor of electromagnetic wave when spatial
R: target range (m)
Z: cloud reflection factor
L
Σ: total link loss (dB)
The natural logarithm of ln2:2, gets 0.69315
In this example, the actual gain of radar antenna can get 50dBi according to current level of processing in link budget.Reflectivity factor Z is a cloud parameter irrelevant with frequency, and border cloud layer reflectivity is between-20dBz to 10dBz, and non-Precipitation Clouds is about-35dBz.For the distance by radar equation of meteorological target, in formula (1), parameters value is as follows:
τ＝0.3μs
G＝50dBi
L
Σ＝5dB
When radar transmitted pulse power P
tduring for 200mW, after coherent accumulation process, for the cloud layer of reflectivity at-20dBz, detection range can reach 3002 meters, meet cloud and measure test demand, therefore in the present invention, Terahertz radar transmission power is chosen to be 200mW.
In the present embodiment, pulse width is 100ns ~ 3 μ s (adjustable, step-length is 100ns), and pulse repetition rate (PRF) is 1KHz ~ 10KHz (adjustable, step-length is 1KHz).
(3) bandwidth of operation is determined
System works bandwidth is wider, and range resolution is higher.Native system is applied to survey cloud field, by cloud parameter model, show that smaller strip is wide and can improve cloud parametric inversion precision, but bandwidth reduction can cause the reduction of range resolution, and in the application of survey cloud, emphasis needs to ensure cloud parametric inversion precision.On the basis of trade off bandwidth, range resolution and inversion accuracy index, Terahertz radar is surveyed cloud bandwidth of operation and is decided to be 5GHz, now the range resolution of native system is better than 3cm, can meet and survey cloud accuracy requirement.
(4) pulse width and pulse repetition rate is determined
In the present embodiment, pulse width is 100ns ~ 3 μ s (adjustable, step-length is 100ns), and pulse repetition rate (PRF) is 1KHz ~ 10KHz (adjustable, step-length is 1KHz).
(5) receiving sensitivity is better than-80dBm
Receiver sensitivity is the important indicator of reflection Terahertz cloud detection radar system acceptance performance, main relevant with system noise factor with the system bandwidth of receiver.According to above-mentioned analysis, when system bandwidth is 5GHz, when system noise factor is 12dB, native system receiving sensitivity is in theory:
P
rmin＝-114+10lgΔf+N
F＝-114+10lg5+12＝-87.41dBm
Wherein, Δ f is system works bandwidth, N
ffor system noise factor.In actual design, consider that environment and component influences etc. can affect the receptivity of receiver, therefore Terahertz radar system receiver sensitivity is decided to be is better than-80dBm.
(6) dynamic range is better than 60dB
The requirement of dynamic range depends primarily on the variation range of the signal power that receiver receives.In native system, receiver dynamic range mainly affects by cloud layer reflectivity factor Z, and reflectivity factor Z is a cloud parameter irrelevant with frequency, and border cloud layer reflectivity is between-20dBz to 10dBz, and non-Precipitation Clouds is about-35dBz.Consider that the cloud layer reflectivity that native system mainly detects is that between-40dBz to 10dBz, the received signal power caused thus is changed to 50dB; Antenna part, the change in gain of feeding line portion in broadband are about 3 ~ 5dB simultaneously.As fully visible, the change of received signal power is about 53 ~ 55dB, therefore Terahertz radar system receiver dynamic range is decided to be and is better than 60dB.
Select based on above-mentioned parameter, composition graphs 1, the ground Terahertz radar system for surveying cloud provided by the invention specifically comprises terahertz sources module, Terahertz receiver module, Terahertz dual-mode antenna module, terahertz signal processing module and upper computer module.
Terahertz sources module, the intermediate-freuqncy signal source produced for utilizing Terahertz receiver module completes generation and the power amplification of terahertz signal, is then launched by Terahertz dual-mode antenna module.The centre frequency of the terahertz signal launched is 220GHz, and bandwidth of operation is 5GHz, and emissive power is 200mW, pulse width is that 100ns ~ 3 μ s is (adjustable, step-length is 100ns), pulse repetition rate is 1KHz ~ 10KHz (adjustable, step-length is 1KHz).
Terahertz receiver module, for complete the generation of derived reference signal, intermediate-freuqncy signal source generation, to the down coversion of the Terahertz echoed signal that Terahertz dual-mode antenna module receives and secondary intermediate frequency process, then send to terahertz signal processing module.The centre frequency of this Terahertz receiver module is 220GHz, and bandwidth of operation is 5GHz, and receiving sensitivity is better than-80dBm, and dynamic range is better than 60dB.
Terahertz signal processing module, for realizing collection, the storage of the secondary intermediate-freuqncy signal of Terahertz echo and processing.
Upper computer module communicates with Terahertz receiver module with terahertz signal processing module respectively, controls with frequently comprehensive to realize data transmission.
In order to realize precision controlling, the present invention also comprises Terahertz internal calibration module for the ground Terahertz radar system surveying cloud.As shown in Figure 1, this Terahertz internal calibration module obtains the terahertz signal of transmitting from terahertz sources module, and the down-converted identical with Terahertz receiver module is carried out to it, then send to Terahertz receiver module to carry out secondary intermediate frequency process, the internal calibration secondary intermediate-freuqncy signal of acquisition sends to terahertz signal processing module; Whether terahertz signal processing module checks the emissive power of terahertz sources signal and frequency to offset according to internal calibration secondary intermediate-freuqncy signal further, according to the amplifying power of transmit power offset value adjustment terahertz sources module, according to the generation in the intermediate-freuqncy signal source of frequency skew adjustment Terahertz receiver module.
Be described in detail below in conjunction with the realization of accompanying drawing to each comprising modules in the Terahertz radar system of ground of the present invention.
◎ terahertz sources module
As shown in Figure 1, terahertz sources module comprises Terahertz frequency multiplication link, Terahertz power amplifier, coupling mechanism.Wherein,
Terahertz frequency multiplication link, the intermediate-freuqncy signal source frequency multiplication for being produced by Terahertz receiver module obtains the signal of Terahertz frequency range.
This Terahertz frequency multiplication link will realize that frequency is 220GHz, bandwidth of operation is 5GHz, and output power reaches more than 10mW, require very high to the Primary Component such as high frequency power amplifier, diode, simultaneously Terahertz frequency multiplication source can not adopt high order frequency, and frequency multiplication mode has × and 2 × 2 × 3 and × 3 × 2 × 2 two kinds of modes are optional.The frequency relation of × 2 × 2 × 3 frequency multiplication modes is 18.3GHz → 36.6GHz → 73.3GHz → 220GHz, compared to × 3 × 2 × 2 frequencys multiplication, which drives in 73.3GHz band limits in prime desirable power amplifier chip, and its output power can use power synthetic technique to realize higher driving power; In link, maximum power output is about 300mW simultaneously, and current diode can bear, and in addition, × 2 × 2 × 3 frequency multiplication mode volumes are little, low in energy consumption, can meet system requirements.Therefore, as shown in Figure 2, Terahertz frequency multiplication link in the present embodiment adopts × 2 × 2 × 3 frequency multiplication cascade systems to realize, first the frequency received from Terahertz receiver module is 18.33 ± 0.208GHz, power is the local oscillation signal of 0dBm, the output of 73.2 ± 0.832GHz is obtained by an E wave band quadrupler (being made up of two varactor doublers) and E band filter, then 73.2 ± 0.832GHz is obtained through E band power compositor, power is about the output of 300mW, finally drive 220GHz frequency tripler, frequency tripling finally realizes 220 ± 2.5GHz, power is transmitting of 10mW, be transmitted to Terahertz power amplifier.
Wherein, E wave band quadrupler is made up of two varactor doublers, Ka varactor doubler and E wave band varactor doubler respectively, 18.33 ± 0.208GHz local oscillation signal frequency multiplication is frequency by Ka varactor doubler (HMC598) is 36.666GHz ± 0.416GHz signal, then is the signal of 73.333GHz ± 0.832GHz by E wave band varactor doubler (CHU3277) frequency multiplication.
Terahertz power amplifier, carries out power amplification, to increase the operating distance of radar for the terahertz signal exported by Terahertz frequency multiplication link.Terahertz power amplifier adopts folded waveguide travelling-wave tube amplifier (TWTA) to realize the power stage of large bandwidth (5GHz, resolution 3cm), 200mW.
Coupling mechanism, the signal for being produced by Terahertz power amplifier exports to Terahertz dual-mode antenna module and Terahertz internal calibration module.
◎ Terahertz receiver module
As shown in Figure 1, Terahertz receiver module comprises referrer module, secondary ifd module, local oscillator module and down coversion receiver module.In the present embodiment, Terahertz receiver module centre frequency is 220GHz, bandwidth of operation is 5GHz, receiving sensitivity is better than-80dBm, dynamic range is better than 60dB.
Referrer module, for producing reference frequency source for Terahertz receiver module, reference frequency source is 100MHz.
Local oscillator module, for producing intermediate-freuqncy signal source for Terahertz receiver module and terahertz sources module.As shown in Figure 3, local oscillator module by by the Frequency Hopping Signal (being produced by frequency hopping synthesizer module generator) of 2.18 ~ 3.203GHz (step-length is 1MHz) by being divided into two-way after amplifier F0 and power splitter G1 process, device L1, amplifier F1, frequency mixer H1 (with 15.65GHz mixing), wave filter L2, the signal that produces 1 tunnel 17.83 ~ 18.853GHz after amplifier F2 process export after filtering successively on a road; Another road signal produced after power splitter G1 process signal that warp produces 2 tunnel 17.74 ~ 18.763GHz by power splitter G2 after device L3, amplifier F3, frequency mixer H2 (with 15.56GHz mixing), wave filter L4, amplifier F4 process after filtering successively exports; Wherein the signal of 17.83 ~ 18.853GHz exports to terahertz sources module, as the intermediate-freuqncy signal source of terahertz sources module; The signal of 17.74 ~ 18.763GHz exports to down coversion receiver module and Terahertz internal calibration module, as the intermediate-freuqncy signal source of down coversion receiver module and Terahertz internal calibration module.
Down coversion receiver module, Terahertz radar for obtaining receiving antenna in Terahertz dual-mode antenna module is surveyed cloud echo signal and is carried out down coversion, as shown in Figure 4, the signal of the 17.74 ~ 18.763GHz produced from local oscillation signal exports the signal of extraction 18.04 ~ 18.45GHz after frequency tripler, wave filter L5, amplifier F5, wave filter L6, amplifier F6, varactor doubler, carries out the intermediate frequency that mixing obtains 1080MHz export with the echoed signal of 217.56 ~ 222.48GHz received by Terahertz receiving antenna module.
Secondary ifd module, the 1020MHz signal produced for the 1080MHz of Terahertz receiver module or Terahertz internal calibration module being exported and fixed local vibration source carries out mixing and obtains 60MHz bis-intermediate-freuqncy signals, exports to terahertz signal processing module.
◎ Terahertz dual-mode antenna module
Terahertz dual-mode antenna module comprises terahertz sources antenna, Terahertz receiving antenna.
In this example, Terahertz radar needs to carry out cloud measurement test at simulation cloud chamber and high mountain mountain top.When high mountain mountain top, the form of Terahertz dual-mode antenna is Cassegrain antenna, and according to the discussion of formula (1), Cassegrain antenna gain is 50dBi, and beam angle is not more than 0.7 °.When simulating cloud chamber, the size of cloud chamber is 3.5m × 3.5m, and the form of Terahertz dual-mode antenna is electromagnetic horn, and the receiving antenna gain in electromagnetic horn is 30dBi, and beam angle is 8 °.Transmitter antenna gain (dBi) in electromagnetic horn is 20dBi, and beam angle is 15 °.
◎ Terahertz internal calibration module
The structure of Terahertz internal calibration module is identical with the structure of down coversion receiver module.As shown in Figure 4, the 220GHz terahertz sources signal that Terahertz internal calibration module is obtained after frequency tripler, wave filter L5 ', amplifier F5 ', wave filter L6 ', amplifier F6 ', varactor doubler and from the coupling mechanism terahertz sources module by the signal of 18.04 ~ 18.45GHz carries out the intermediate frequency that down coversion obtains 1080MHz and exports, and the secondary ifd module exported in Terahertz receiver module, obtain 60MHz bis-intermediate-freuqncy signals, export to terahertz signal processing module.
◎ terahertz signal processing module
The collection of the secondary intermediate-freuqncy signal of terahertz signal processing modules implement Terahertz echo, store and process.
Terahertz signal processing module also realizes periodic internal calibration and the adjustment of Terahertz cloud detection radar system according to the internal calibration intermediate-freuqncy signal from Terahertz internal calibration module, detect the drift of terahertz sources module, Terahertz receiver module, to ensure stability and the accuracy of Terahertz cloud detection radar system.The emissive power of terahertz sources signal and frequency is checked whether to offset according to internal calibration secondary intermediate-freuqncy signal specifically, according to the amplifying power of transmit power offset value adjustment terahertz sources module, according to the generation in the intermediate-freuqncy signal source of frequency skew adjustment Terahertz receiver module.
As shown in Figure 1, this terahertz signal processing module comprises analog to digital converter (AD), storer A, storer B, field programmable gate array (FPGA), digital signal processor (DSP), Gigabit Ethernet module.Analog to digital converter, storer B, digital signal processor are all connected with field programmable gate array with Gigabit Ethernet module, and storer A is connected with digital signal processor.
As shown in Figure 5, analog to digital converter adopts AD9254 chip, realize 14bit (bit), the data acquisition ability of 150MSPS (million samplings are per second), Altera EP2S90F1020 (FPGA) and TMS320C6455 (DSP) is adopted to realize being not less than the arithmetic capability of 9600MMACS (million multiply-add operations are per second), FPGA is plug-in 128MB SDRAM, DSP is plug-in 512MB DDR2.
◎ upper computer module
Upper computer module is communicated with Terahertz receiver module with terahertz signal processing module with serial ports respectively by gigabit Ethernet, controls with frequently comprehensive to realize data transmission.Upper computer module comprises computer main board, display, realizes controlling and Presentation Function.
In sum, these are only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (7)
1. for surveying a ground Terahertz radar system for cloud, it is characterized in that, comprise: terahertz sources module, Terahertz receiver module, Terahertz dual-mode antenna module, terahertz signal processing module and upper computer module;
Terahertz sources module, the intermediate-freuqncy signal source produced for utilizing Terahertz receiver module completes generation and the power amplification of terahertz signal, is then launched by Terahertz dual-mode antenna module; The centre frequency of the terahertz signal launched is 220GHz, bandwidth of operation is 5GHz, emissive power is 200mW, and pulse width is adjustable within the scope of the μ s of 100ns ~ 3 and regulates step-length to be 100ns, and pulse repetition rate is adjustable within the scope of 1KHz ~ 10KHz and regulates step-length to be 1KHz;
Terahertz receiver module, for complete the generation of derived reference signal, intermediate-freuqncy signal source generation, to the down coversion of the Terahertz echoed signal that Terahertz dual-mode antenna module receives and secondary intermediate frequency process, then send to terahertz signal processing module; The centre frequency of this Terahertz receiver module is 220GHz, and bandwidth of operation is 5GHz, and receiving sensitivity is better than-80dBm, and dynamic range is better than 60dB;
Terahertz signal processing module, for realizing collection, the storage of the secondary intermediate-freuqncy signal of Terahertz echo and processing;
Upper computer module communicates with Terahertz receiver module with terahertz signal processing module respectively, controls with frequently comprehensive to realize data transmission.
2. the system as claimed in claim 1, it is characterized in that, this system comprises Terahertz internal calibration module further, this Terahertz internal calibration module obtains the terahertz signal of transmitting from terahertz sources module, and the down-converted identical with Terahertz receiver module is carried out to it, then send to Terahertz receiver module to carry out secondary intermediate frequency process, the internal calibration secondary intermediate-freuqncy signal of acquisition sends to terahertz signal processing module; Whether terahertz signal processing module checks the emissive power of terahertz sources signal and frequency to offset according to internal calibration secondary intermediate-freuqncy signal further, according to the amplifying power of transmit power offset value adjustment terahertz sources module, according to the generation in the intermediate-freuqncy signal source of frequency skew adjustment Terahertz receiver module.
3. system as claimed in claim 2, it is characterized in that, described terahertz sources module comprises Terahertz frequency multiplication link, Terahertz power amplifier and coupling mechanism;
Described Terahertz frequency multiplication link, the intermediate-freuqncy signal source frequency multiplication for being produced by Terahertz receiver module obtains the signal of Terahertz frequency range, frequency multiplication adopts the cascade system of two frequency multiplication+two frequencys multiplication+frequency triplings to realize: the frequency that first receiving Terahertz receiver module provides is 18.33GHz ± 0.208GHz, power is the signal of 0dBm, the output of 73.2GHz ± 0.832GHz is obtained by the E wave band quadrupler of two varactor doubler composition and E band filter, then 73.2GHz ± 0.832GHz is obtained through E band power compositor, power is the output of 300mW, finally drive 220GHz frequency tripler, finally 220GHz ± 2.5GHz is realized by frequency tripler, power is transmitting of 10mW, be transmitted to Terahertz power amplifier,
Wherein, E wave band quadrupler is made up of two varactor doublers, Ka varactor doubler and E wave band varactor doubler respectively, the signal frequency multiplication of 18.33GHz ± 0.208GHz is frequency by Ka varactor doubler is 36.666GHz ± 1GHz signal, then is the signal of 73.333GHz ± 0.832GHz by E wave band varactor doubler frequency multiplication;
Terahertz power amplifier, carries out power amplification for the terahertz signal exported by Terahertz frequency multiplication link;
Coupling mechanism, the signal for being produced by Terahertz power amplifier exports to Terahertz dual-mode antenna module and Terahertz internal calibration module.
4. system as claimed in claim 2, it is characterized in that, described Terahertz receiver module comprises referrer module, secondary ifd module, local oscillator module and down coversion receiver module;
Referrer module, for producing reference frequency source for Terahertz receiver module, reference frequency source is 100MHz;
Local oscillator module, for producing intermediate-freuqncy signal source for Terahertz receiver module and terahertz sources module; This local oscillator module is passed through by the Frequency Hopping Signal of 2.18GHz ~ 3.203GHz by being divided into two-way after amplifier F0 and power splitter G1 process, and a road is device L1, amplifier F1, frequency mixer H1, wave filter L2, the rear signal output producing 1 17.83GHz ~ 18.853, road GHz of amplifier F2 process after filtering successively; Another road signal produced after power splitter G1 process successively after filtering after device L3, amplifier F3, frequency mixer H2, wave filter L4, amplifier F4 process through being produced the signal output of 2 17.74GHz ~ 18.763, road GHz by power splitter G2; Wherein the signal of 17.83GHz ~ 18.853GHz exports to terahertz sources module, as the intermediate-freuqncy signal source of terahertz sources module; The signal of 17.74GHz ~ 18.763GHz exports to down coversion receiver module and Terahertz internal calibration module, as the intermediate-freuqncy signal source of down coversion receiver module and Terahertz internal calibration module;
Down coversion receiver module, the Terahertz radar for obtaining receiving antenna in Terahertz dual-mode antenna module is surveyed cloud echo signal and is carried out down coversion;
Secondary ifd module, the 1020MHz signal produced for the 1080MHz of Terahertz receiver module or Terahertz internal calibration module being exported and fixed local vibration source carries out mixing and obtains 60MHz bis-intermediate-freuqncy signals, exports to terahertz signal processing module.
5. system as claimed in claim 4, it is characterized in that, described down coversion receiver module, the signal of 17.74GHz ~ 18.763 GHz produced from local oscillation signal exports and extracts the signal of 18.04GHz ~ 18.45 GHz after frequency tripler, wave filter L5, amplifier F5, wave filter L6, amplifier F6, varactor doubler, carries out the secondary intermediate frequency that mixing obtains 1080MHz export with the echoed signal of the 217.56GHz ~ 222.48GHz received by Terahertz receiving antenna module.
6. system as claimed in claim 2, it is characterized in that, described Terahertz dual-mode antenna module comprises terahertz sources antenna and Terahertz receiving antenna;
When being applied to high mountain mountain top survey cloud, the form of terahertz sources antenna and Terahertz receiving antenna is Cassegrain antenna, and Cassegrain antenna gain is 50dBi, and beam angle is not more than 0.7 °;
When being applied to simulation cloud chamber, the form of terahertz sources antenna and Terahertz receiving antenna is electromagnetic horn, and the receiving antenna gain in electromagnetic horn is 30dBi, and beam angle is 8 °.Transmitter antenna gain (dBi) in electromagnetic horn is 20dBi, and beam angle is 15 °.
7. system as claimed in claim 2, it is characterized in that, described terahertz signal processing module comprises analog to digital converter, storer A, storer B, FPGA, DSP and Gigabit Ethernet module; Analog to digital converter, storer B, DSP are all connected with FPGA with Gigabit Ethernet module, and storer A and DSP is connected;
Analog to digital converter adopts AD9254 chip, and FPGA adopts Altera EP2S90F1020 chip, and DSP adopts TMS320C6455 chip, and storer B adopts 128MB SDRAM, and storer A adopts 512MBDDR2.
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