CN201207064Y - Fully digital compensation microwave radiometer - Google Patents
Fully digital compensation microwave radiometer Download PDFInfo
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- CN201207064Y CN201207064Y CNU2008200655802U CN200820065580U CN201207064Y CN 201207064 Y CN201207064 Y CN 201207064Y CN U2008200655802 U CNU2008200655802 U CN U2008200655802U CN 200820065580 U CN200820065580 U CN 200820065580U CN 201207064 Y CN201207064 Y CN 201207064Y
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- radiometer
- microwave
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- data acquisition
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Abstract
The utility model discloses an all digital compensation microwave radiometer, comprising an antenna, a mating load, a microwave switch, a total power radiometer, a digital control unit, a communication unit and a display unit. According to periodical detection of the mating load and the input voltage of the antenna, together with the actual temperature of the mating load, influence to the performance of the radiometer from the amplification indeterminacy of the radiometer system and the fluctuation of the noise of the machine is offset by an digital compensation operator of the digital control unit. The radiometer is greatly improved in sensitivity and long-time stability and is simple in structure and small in size. The radiometer can work for a long time after initial calibration, avoids the trouble of calibration at a groundsill, a space base and a satellite-based period, and greatly improves target observation time and range.
Description
Technical field
The utility model belongs to microwave remote sensing, guidance and Technology of Precision Measurement field, is specifically related to a kind of all-digital compensation microwave radiometer.
Background technology
Microwave radiometer is the nucleus equipment of passive microwave remote sensing, is the unique instrument that carries out microwave radiation characteristics detection, imaging and the judgement of surface feature background and target.
The development trend of microwave radiometer is from the figure to the imaging radiometer, from the low resolution radiometer to the height resolution radiometer.Usually the microwave radiometer output pulsation is by the own ship's noise uncertainty
With the system-gain uncertainty
Decision, for reducing the influence that system-gain is unstable and the own ship's noise fluctuation is exported radiometer, people have adopted various ways, have developed dissimilar radiometers.At first, on the basis of total power radiometer, nineteen forty-six Dicke develops the Dicke radiometer, adopts the single-pole double-throw (SPDT) microwave switch, has significantly reduced the influence of gain fluctuation, makes microwave radiometer move towards practicability.But only when antenna temperature equated with the reference source temperature, ability is the influence of cancellation receiver gain fluctuations all for this method.Goggins developed negative feedback zero balancing microwave radiometer in 1967, but PIN diode can be introduced Johnson noise more or less, had increased negative feedback loop and active, the passive device of several microwave simultaneously, made complex system, and technical difficulty is big.Nineteen sixty-eight Hach develops two reference temperature automatic gain compensation microwave radiometers, is that difference by two known reference sources changes and adjusts the postsignal amplifier gain, with the bucking-out system change in gain.The exigent rearmounted feedback control loop of this radiometer has increased a reference source simultaneously, and cost is higher.On the basis of such scheme, comrade Zhang Zuyin of 1990 Central China University of Science and Technology has proposed " pulsed modulation constant current source noise inject zero balancing type radiometer " scheme, and successively to succeed in developing with 8 millimeters, 2 centimetres and 21 superhigh frequency bands be the high precision microwave radiometer series of representative.This method can be eliminated owing to the front end loss and reflect the measuring error that causes, further improves the absolute precision of system; And because circuitry and device work in the isoperibol, can guarantee that system works is stable and reliable for performance, but its hardware system is comparatively complicated, uses very inconvenient.
Airborne in order to adapt to, spaceborne condition, two kinds of novel microwave radiometer (lists of references: Li Jing of Chinese Academy of Sciences's Changchun digital gain compensation that Geographical Study has been developed and real-time calibration, Zhang Junrong, Zou Tong. digital gain compensation and real-time calibration microwave radiometer. electronic letters, vol, 1999,27 (3): 49～51).Its digital gain compensation type microwave radiometer, be with a benchmark microwave source signal by the microwave radiation meter systems, detect the undulate quantity of system-gain at output terminal, go to revise the radiation of institute's receiving target with single-chip microcomputer by this undulate quantity again, just can obtain true value.It is constant to suppose in this derivation that receiver noise TREC stablizes, but in the actual use, because system exists noise fluctuations and reference source also can change, this compensation method will certainly cause measuring error, thus the accuracy that influence is measured.And real-time calibration microwave radiometer has adopted two radio-frequency (RF) switch and two microwave reference sources, has increased the complexity of device, thereby can introduce extra error.
More than these radiometers influence and all received certain effect reducing or eliminating system-gain fluctuation and own ship's noise, but they otherwise adopt two reference sources, adopt synchronous demodulation and negative feedback loop, go the Adjustment System gain by AGC simultaneously or use two reference sources to eliminate system-gain and own ship's noise fluctuation, these bring considerable influence all for the degree of accuracy of radiometer measurement and system stability; The circuit structure complexity brings difficulty for the long-term use of radiometer simultaneously; A plurality of hypothesis of carrying out in derivation all can be brought no small error to measurement.Therefore problems such as the calculating of the choosing of the elimination of system-gain and own ship's noise influence of fluctuations, reference noise source, radiation brightness and temperature detection all are that the problem of fine solution is failed in the radiometer development.These radiometers all need carry out the cycle calibration simultaneously, not only calibrate complex structure, also can bring bigger measuring error, bring difficulty for the long-term use of radiometer.
By last analysis as can be known, for microwave radiometer, the breakthrough improvement of circuit system type is very difficult, along with development of computer, how to give full play to the advantage that microprocessing speed is fast, volume is little, precision is high and design the high performance microwave radiometer, and simplify its calibration structure, and will be an important development direction of novel microwave radiometer research, this seems particularly important for radiometer in the application of spaceborne platform.
Summary of the invention
The purpose of this utility model is to provide a kind of all-digital compensation microwave radiometer, and this microwave radiometer not only volume is little, in light weight, and its sensitivity, degree of stability height.
The all-digital compensation microwave radiometer that the utility model provides, comprise antenna, matched load, microwave switch, total power radiometer, data acquisition and control module, display unit, the fixed end of microwave switch links to each other with the input end of total power radiometer, two contacts link to each other with the stiff end of antenna and matched load respectively, the input end of data acquisition and control module links to each other with the output terminal of total power radiometer, the temperature measurement circuit output terminal of matched load links to each other with the input end of data acquisition and control module, the output terminal of data acquisition and control module links to each other with the input end of display unit, and the control signal output ends of data acquisition simultaneously and control module links to each other with the control end of microwave switch;
The output voltage V of total power radiometer when data acquisition and control module are gathered microwave switch connection matched load respectively and connected antenna
RnAnd V
An, and the temperature measurement circuit output terminal temperature T of matched load
Rn, wherein n is the cycle sequence number; Utilize following formula to calculate the bright temperature value T of measured target again
An:
Wherein, G
S1Be system's initial gain.
The utility model is exported on the uncertain basis of mechanism analysis at radiometer, the method of employing digital compensation is eliminated the influence of system-gain and own ship's noise fluctuation, cancellation synchronous demodulation and negative feedback loop adopt simple, manageable reference source to design all-digital compensation microwave radiometer simultaneously.The type radiometer not only volume is little, in light weight, and sensitivity, the degree of stability of radiometer are greatly improved simultaneously, and also can set flexibly according to demand the integral time of radiometer; Because radiometer is after initially calibrating, just can carry out the compensation of noise and gain automatically, need not to calibrate once more, thereby avoid the trouble of cycle calibration in the past, antenna for radiometer can carry out for a long time target, observe on a large scale simultaneously, has improved the efficient of radiometer.These bring huge convenience all for the use (especially spaceborne application) of radiometer.
Description of drawings
Fig. 1 is the structural representation of the utility model all-digital compensation microwave radiometer;
Fig. 2 is the program flow chart of TT﹠C software;
Fig. 3 is an all-digital compensation microwave radiometer switch motion sequential chart.
Embodiment
Below in conjunction with accompanying drawing and example the utility model is described in further detail.
As shown in Figure 1, the utility model all-digital compensation microwave radiometer comprises antenna 1, matched load 2, microwave switch 3, total power radiometer 4, data acquisition and control module 5, communication interface 6 and display unit 7.
Matched load 2 is given reference noise of total power radiometer, the utility model directly adopts matched load as the reference source, and its physical temperature is directly measured in real time, avoids adopting constant temperature and temperature regulating device, simplify the structure of device, required matched load standing-wave ratio (SWR)＜1.1.
Data acquisition and control module 5 are used for the voltage of total power radiometer 4 outputs is gathered calculating, the control of microwave switch 3 action sequences, matched load 2 temperature surveys, system-gain and own ship's noise compensation.And send communication interface 6 communication, the bright temperature of measured target to send display unit 7 to show the relevant information (measuring voltage, the bright temperature of measured target etc.).
In data acquisition and the control module 5 TT﹠C software is installed, it comprises following several sections: voltage, temperature acquisition calculate; Gain and noise compensation calculate; The bright temperature of measurement target shows; Calibration temperature is provided with; Compositions such as communication.Its program flow chart as shown in Figure 2.The course of work is as follows:
System power on or reset after at first finish power-up initializing and serial port initialization, the serial port initialization section finish baud rate setting, make this machine be in functions such as intercepting address state.After finishing all initial work, open interrupt latency and interrupt producing.Judge to have or not calibration temperature that request is set, have and just after the calibration temperature setting is finished, ask for system's initial gain, otherwise from external ROM, read the system-gain value of storage.Begin voltage acquisition and system balance then and calculate, calculate the antenna temperature of measured target, and finish data framing, antenna temperature Presentation Function and whether finish master routine.Return data collection again after all functions are finished, circulation is until EOP (end of program).In cyclic process,, then enter the reception transmission that serial is interrupted if there is serial to interrupt producing; Obtain " calibration temperature setting " order if look into key, then carry out the calibration temperature setting, single-chip microcomputer then resets.
The bright temperature of measured target of 7 pairs of data collections of display unit and control module 5 outputs shows on the spot.
The switch motion sequential of all-digital compensation microwave radiometer can be thought as shown in Figure 3.Suppose in period T
1, T
2, T
3, T
4In, the gain of system is respectively G
S1, G
S2, G
S3, G
S4At T
1Preceding semiperiod T
10The noise of interior system is T
REC1T
1Later half period T
11And T
2Preceding semiperiod T
20The noise of interior system is T
REC2T
21, T
30And T
31, T
40The noise of interior system is respectively T
REC3And T
REC4The temperature of the bright gentle matched load of tested scene is thought real-time change, is expressed as T respectively
A1～T
A7And T
R1～T
R7(T wherein
R2=T
R3, T
R4=T
R5, T
R6=T
R7, i.e. each T
RECPeriod of change is measured once).
At T
10, T
11In, when switch was got to matched load and antenna, the output valve of radiometer was respectively:
V
R1＝G
S1(T
R1+T
REC1)；V
A1＝G
S1(T
A1+T
REC1)
V
R2＝G
S1(T
R2+T
REC2)；V
A2＝G
S1(T
A2+T
REC2)
Then:
ΔV
1＝V
R1-V
A1＝G
S1(T
R1-T
A1)；Δ
V2＝V
R2-V
A2＝G
S1(T
R2-T
A2)
Abbreviation gets: T
A1=T
R1-Δ V
1/ G
S1T
A2=T
R2-Δ V
2/ G
S1
In like manner can get:
T
A3＝T
R3-ΔV
3/G
S2； T
A4＝T
R4-ΔV
4/G
S2
T
A5＝T
R5-ΔV
5/G
S3； T
A6＝T
R6-ΔV
6/G
S3
Again because
Then following formula can turn to:
T
A3＝T
R3-ΔV
3/(k
3·G
S1)
T
A5＝T
R5-ΔV
5/(k
5·G
S2)＝T
R5-ΔV
5/(k
5·k
3·G
S1)
The rest may be inferred:
ΔV
n＝V
Rn-V
An
Make k
1=k
2=1, can get:
By this formula as can be known, no matter how system-gain and own ship's noise change, and after handling by software compensation, it is constant to think that the gain of system and own ship's noise remain, from the radiometer output Δ V that records
n=V
Rn-V
AnAnd the initial gain G of system
S1(the initial calibration by system obtains) just can try to achieve antenna temperature T
AnAnd G
S1Can obtain by the initial calibration of radiometer.
By last analysis as can be known, come bucking-out system gain and own ship's noise with software after.By the switch motion time sequence control, after initial calibration and the compensation of digital compensation operator, radiometer can aim at the mark always and measure, and need not to calibrate once more.
The all compensation work of this radiometer realize by software, compare with microwave radiometer in the past and can save automatic gain control (AGC) part, have avoided increasing the inconvenience that hardware brings.Therefore its design proposal is as follows: use a matched load as the reference source, avoid the trouble of in the past using two reference sources to bring; Reference source is carried out real time temperature detect, and do not adopt thermostatically controlled way; After compensation, the bright temperature of the target that records can show on the spot, also can communicate by same ground-based computer (host computer), just can finish radiometer switch motion frequency, data sampling interval, isoparametric setting integral time on ground, and bright temperature curve or the radiation image of drawing the target of surveying.Therefore designed all-digital compensation microwave radiometer schematic diagram as shown in Figure 1.
At first build the all-digital compensation microwave radiometer hardware system, and write the software of data acquisition and control module by software flow shown in Figure 2 by Fig. 1.Wherein the single-chip microcomputer and the corresponding A/D chip of selection instruction cycle weak point come design circuit, and the instruction cycles of backoff algorithm program will carry out accurate Calculation simultaneously, are strict controlled in the stable of interior system-gain of a switch periods and own ship's noise.
Example:
Developed an all-digital compensation 8mm radiometer, this radiometer has mainly adopted as lower member:
1, antenna 1 is selected the 8mm pyramidal horn antenna for use, antenna aperture: 8cm*4cm;
2, microwave switch 3 is selected the junction type locking-type waveguide switch that the space flight Second Academy produces for use.This switch is equivalent to a single-pole double-throw (SPDT) microwave switch, and it is low that switch good stability, forward insert loss.
3, matched load 2 adopts the matched load that the big magnificent company in Beijing produces, and standing-wave ratio (SWR) is 1.05;
4, the integral structure pattern that Russian Saturn company produced before total power radiometer 4 adopted, frequency of operation f=35GHz, intermediate-frequency bandwidth Δ f ≈ 1GHz; Front-end gain G=65dB; Double-side band noise figure F=6dB.
5, data acquisition and control module 5 are core components of all-digital compensation microwave radiometer, and controlled microwave switch 3 is connected antenna 1 or matched load 2; Calibration and the initial gain of finishing radiometer calculate; The collection of control data, processing are finished the compensation of the bright temperature of target and are calculated, and result of calculation is outputed to display unit 7 show and communicate by letter.Consider the get it right requirement of time of compensation cycle and compensating gage, single-chip microcomputer selects for use high speed processing chip C8051F120 to finish; Select for use 2K serial CSI24WC02 as exterior storage simultaneously, preserve initial gain, gather voltage and the bright temperature of target.
6, communication interface 6 adopts transmitting-receiving control chips (MAX1487) to finish communicating by letter of radiometer and host computer through the RS485 bus.
7, display unit 7 adopts four LCD (LCD) to connect, and is used for showing antenna temperature value and calibration temperature value, links to each other by two mouth lines of data (DATA) and clock (CLK) with single-chip microcomputer.
Calibration process is as follows:
After the start, allow radiometer working stability (work more than 30 minutes), under the environment temperature of radiometer work, calibrate.
1, allows a known noise source (temperature of this noise source output should have uniform temperature at interval with the output temperature of reference source) of temperature aim at the port of antenna, obtain the antenna output temperature T of this moment
A'; Adopted a solid-state noise source (MSC produces), to adopt a variable attenuator that the input noise of radiometer is controlled simultaneously in the experiment, carried out the high temperature calibration as the input of radiometer.Again with calibration temperature T
A' deposit EEPROM in; Can utilize cold sky initially to calibrate for spaceborne radiometer.
2, send a calibration instruction (controlling by the button or the telecommunication that are provided with in data acquisition and the control module 5) to single-chip microcomputer, single-chip microcomputer is given 3 gating pulse of microwave switch, and gauge tap is in the switching of 2 of antenna 1 and matched loads; When pointing to by switch is different, the relevant voltage value that single-chip microcomputer is noted just can calculate the initial gain G of system
S1, and deposit EEPROM in;
Then single-chip microcomputer carries out T by sequential in deriving
11, T
20, T
21Step, through compensation with calculate, by cycle (T
10The interval) refresh the antenna temperature T of the measurand of demonstration in real time
An, T
AnCan not change with system-gain and own ship's noise.
After above step calibration, radiometer just can be worked down always, need not to calibrate once more.
In sum, the uncertainty of the utility model elimination radiometer system-gain and the fluctuation of own ship's noise are to the radiometer Effect on Performance, the sensitivity and the long-term stability of radiometer have been improved greatly, while is simple in structure, volume is little, just can carry out long-term observation to target after the initial calibration of radiometer, avoided the trouble of radiometer, improved target observation time and scope in ground, space base and the calibration of satellite-based cycle.
Claims (2)
1, a kind of all-digital compensation microwave radiometer, it is characterized in that: it comprises antenna (1), matched load (2), microwave switch (3), total power radiometer (4), data acquisition and control module (5) and display unit (7), the fixed end of microwave switch (3) links to each other with the input end of total power radiometer (4), two contacts link to each other with the stiff end of antenna (1) with matched load (2) respectively, the input end of data acquisition and control module (5) links to each other with the output terminal of total power radiometer (4), the temperature measurement circuit output terminal of matched load (2) links to each other with the input end of data acquisition with control module (5), the output terminal of data acquisition and control module (5) links to each other with the input end of display unit (7), and the control signal output ends of data acquisition simultaneously and control module (5) links to each other with the control end of microwave switch (3);
The output voltage V of total power radiometer (4) when data acquisition and control module (5) are gathered microwave switch (3) connection matched load (2) respectively and connected antenna (1)
RnAnd V
An, and the temperature measurement circuit output terminal temperature T of matched load (2)
Rn, wherein n is the cycle sequence number; Utilize following formula to calculate the bright temperature value T of measured target again
An:
Wherein, G
S1Be system's initial gain.
2, all-digital compensation microwave radiometer according to claim 1 is characterized in that: it also comprises communication interface (6), and its input end links to each other with the output terminal of data acquisition with control module (5), is used for the remote monitoring and the networking of radiometer.
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| CNU2008200655802U CN201207064Y (en) | 2008-01-29 | 2008-01-29 | Fully digital compensation microwave radiometer |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261934A (en) * | 2019-07-18 | 2019-09-20 | 常州感通威视微波科技有限公司 | Ground-Based Microwave Radiometer system and its calibrating method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261934A (en) * | 2019-07-18 | 2019-09-20 | 常州感通威视微波科技有限公司 | Ground-Based Microwave Radiometer system and its calibrating method |
| CN110261934B (en) * | 2019-07-18 | 2022-03-08 | 常州感通威视微波科技有限公司 | Foundation microwave radiometer system and calibration method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20090311 Termination date: 20110129 |