CN105700850A - Zero balancing digital combination integrator used for Dicke-type radiometer - Google Patents

Abstract

The invention relates to a zero balancing digital combination integrator used for a Dicke-type radiometer. The zero balancing digital combination integrator comprises an ADC conversion unit, a signal combination integrator, a temperature value estimator, a pulse generator and a clock synchronization unit, wherein the ADC conversion unit is used for sampling and quantifying a detection signal to generate a digital signal; the signal combination integrator carries out timing sequence discrimination, segmenting and combining, integral operation and comparison and discrimination on the digital signal, outputs a control signal to the pulse generator according to the comparison result, and outputs a timing sequence discrimination result, a segmenting and combining result, an integral operation result and a comparison and discrimination result to the temperature value estimator; the pulse generator generates pulses of different frequencies or different duty ratios according to the control signal and outputs the pulses to an external noise source switch; the temperature value estimator carries out comprehensive processing on a timing sequence logic signal, two-end digital signals, two integration values and a balance logic judgment result and obtains the antenna-end radiation temperature through calculation; and the clock synchronization unit generates a clock synchronization signal.

Description

A kind of zero balancing numeral for Dick's type radiometer combines integrator

Technical field

The present invention relates to remote sensing survey technical field, relate to a kind of zero balancing numeral for Dick's type radiometer and combine integrator。

Background technology

Radiometer is the passive remote sensing device that a kind of sensitivity is higher, for the thermal electromagnetic radiation of measurement of species。According to Planck's quantum theory, any temperature is higher than the material of absolute zero all by radiation electric magnetic energy。The electromagnetic radiation of target being observed is received by antenna for radiometer and is passed in highly sensitive receiver and is amplified processing, then uses some inversion methods can obtain the information of target being observed。According to radiation transfer theory, the temperature T of feed antenna_A' with the power P delivering to receiver via antenna_A' there is P_A'=KT_A' the relation of B, wherein K is Boltzmann constant, and B is effective receiver bandwith, T_A' physical quantity that namely radiometer to be measured, T_A' representing the radiant power being delivered to receiver by antenna, this measurement result is characterized by two important attribute, i.e. accuracy and precision, and wherein, precision is also referred to as the actinometry sensitivity of radiometer or resolution, and it is the key parameter characterizing radiometer。

Radiometer conventional at present is divided into total power type radiometer and Dick's type radiometer。

Total power type principle of radiometer figure is as shown in Figure 1。In total power radiometer, what be connected with antenna be effective bandwidth is B, overall power gain is the superhet (in Fig. 1 the part in broken box) of G, and superhet is sequentially connected with cymoscope, low pass filter, and low pass filter output voltage is V_out。

The equivalent schematic diagram of total power type radiometer is as shown in Figure 2。In Fig. 2, antenna part is P by an output_A'=KT_A' B noise source substitute；Receiver (comprises transmission line) by one without making an uproar receiver and output is P_REC'=KT_REC' B input noise source combination replaced, wherein, T_REC' it is the equivalent input noise temperature of transmission line-receiver combination。Total input noise power of system is P_SYS=P_A'+P_REC'=KT_SYSB, in formula, T_SYS=T_A'+T_REC'。

According to theory analysis, the actinometry sensitivity Δ T of total power type radiometer is represented byWherein, Δ T_NRepresent the measuring uncertainty only caused by noise bounce,Wherein B is the effective bandwidth of receiver, and τ is the equivalent point time；Δ T_GRepresent the measuring uncertainty caused by receiver system change in gain,Wherein, G_SIt is average system power gain, Δ G_SIt it is the virtual value of the power gain change detected。In actual remote sensing observations, actinometry sensitivity depends mainly on the change of system gain。Such as, for conventional L-band receiver, design parameter is as follows: T_SYS=600K, B=100MHz, τ=0.01s, Δ G_S/G_S=0.01, if antenna temperature T_A' near 300K, then can obtain following result: Δ T_N=0.9K, Δ T_G=9K, Δ T=9.05K。It is to say, actinometry sensitivity actually depends mainly on the change of gain。Sensitivity required in remote sensing observations is usually 1K or less magnitude, and this just requires to improve the change in gain factor (Δ G_S/G_S)。For the radiometer that operating frequency is relatively low, the method controlling supply voltage and ambient temperature can be adopted, make change in gain reduce a magnitude or more better；But for higher frequency range, the Δ G meeting instructions for use to be produced_S/G_S≤10^-4High stability receiver be extremely difficult。For solving this difficult problem, designing again Dick's type radiometer, the theory diagram of Dick's type radiometer is as shown in Figure 3。

Be can be seen that by Dick's type radiometer composition frame chart, compare total power type radiometer, there are two feature: (1) has Dick's switch, is connected (as far as possible near the place of antenna) with receiver inlet, inputs signal for modulation receiver；(2) have a lock detector, with Dick switch with the use of。Modulation is to make receiver inlet periodically at antenna T_A' and reference source T_REFBetween switching, the switching rate of employing is higher than the highest influential spectral component in receiver gain change spectrum。It is to say, within the half period that receiver is connected with antenna, and within the half period being connected with reference noise source, G_SIt is identical。For connecting the first half cycle of antenna and the later half cycle connecting reference source, the output of cymoscope direct current is expressed as:

$\left\{\begin{array}{cc}{\stackrel{\‾}{V}}_{dANT}=C_{d}GkB({T_A}^{\′}+{T_{REC}}^{\′});& 0\≤t\≤{\mathrm{\τ}}_s/2,\\ {\stackrel{\‾}{V}}_{dREF}=C_{d}GkB(T_{REF}+{T_{REC}}^{\′});& {\mathrm{\τ}}_s\≤t\≤{\mathrm{\τ}}_s,\end{array}\right.$

In formula,The direct current detection output of respective antenna half period；The direct current detection output of corresponding reference source half period；K represents Boltzmann constant, and it is sized to 1.38 × 10^-23J·K^-1；C_dExpression cymoscope power sensitivity constant (volt/watt)；T_REFIt is the noise temperature of reference source, τ_s(=1/f_s) it is time of a switch periods。Receiver noise temperature T_REC' including the noise contribution of input switch, its representative value is between 7 to 75K。

Being superimposed upon on DC voltage is the AC compounent formed because of noise and gain fluctuation。Synchronous demodulator in Fig. 3 is switched the switch worked asynchronously and subsequent two unity gain amplifier composition (parallel connection) compositions, the opposite polarity of two amplifiers, the signal V of a reception antenna half period by one with Dick_dANTT (), another receives the signal V of reference source half period_dREF(t)。The output of two unity gain amplifiers delivers to integrator after being added, and then, the direct current of synchronous demodulator is output as:

${\stackrel{\‾}{V}}_{syn}=\frac{1}{2}({\stackrel{\‾}{V}}_{dANT}-{\stackrel{\‾}{V}}_{dREF})=\frac{1}{2}{C}_{d}GkB({T_A}^{\′}-T_{REF})---\left(1\right)$

Owing to being the time of integration τ, so the output of low pass filter practically equals to:

${\stackrel{\‾}{V}}_{out}\left(t\right)=\frac{g_{LF}}{\mathrm{\τ}}\[{\∫}_0^{\mathrm{\τ}/2}{V}_{dANT}\left(t\right)dt-{\∫}_{\mathrm{\τ}/2}^{\mathrm{\τ}}{V}_{dREF}\left(t\right)dt\]---\left(2\right)$

Wherein, g_LFRepresent the voltage gain of low pass filter。

Rising and falling owing to integration eliminates major part exchange, then, output voltage is by a DC componentVery little root-mean-square value relative to one is σ_outAlternating component formed, by above-mentioned formula, can obtainFor:

${\stackrel{\‾}{V}}_{out}=\frac{1}{2}{g}_{LF}{C}_{d}GkB(T_A^{\′}-T_{REF})=\frac{1}{2}{G}_S(T_A^{\′}-T_{REF})---\left(3\right)$

Except filtering V_synT, outside most of heave component of (), low pass filter has also filtered f_sOn AC compounent and higher hamonic wave (producing due to square-wave frequency modulation)。That is, switching rate f_sBandwidth B with low pass filter_LFCompare, it is necessary to much bigger。F_sWith B_LFBetween relation can also take in from the viewpoint of sampling thheorem。B_LFRepresent in output voltage, remain with the frequency range inputting signal fluctuation component, and f_sRepresent the sample frequency of input signal。In order to meet sampling thheorem, it is necessary to make f_s≥2B_LF。

According to formula (3), VD is proportional to T '_AWith T_REFDifference, and with receiver noise temperature T '_RECUnrelated。The expression of the radiometric resolution Δ T of brief description Dick's type radiometer。(3) are rewritten as follows:

${\stackrel{\‾}{V}}_{out}=\frac{1}{2}{G}_S\[(T_A^{\′}+T_{REC}^{\′})-(T_{REF}+T_{REC}^{\′})\]$

V_outT the AC compounent of () comprises three ingredients:

A. change in gain, the gain that it causes is uncertain, is expressed as:

ΔT_G=(T '_A-T_REF)(ΔG_S/G_S)；

b.(T′_A+T′_REC) noise change, during τ/2 during integration, the incorrect noise that it causes is:

${\mathrm{\ΔT}}_{N-ANT}=\frac{T_A^{\′}+T_{REC}^{\′}}{\sqrt{B\mathrm{\τ}/2}}=\frac{\sqrt{2}(T_A^{\′}+T_{REC}^{\′})}{\sqrt{B\mathrm{\τ}}};$

c.(T_REF+T′_REC) noise change, the incorrect noise that it causes is:

${\mathrm{\ΔT}}_{N-REF}=\frac{\sqrt{2}(T_{REF}+T_{REC}^{\′})}{\sqrt{B\mathrm{\τ}}}.$

Assume that these three uncertainty is statistical iteration, then total actinometry resolving power is

Δ T=[(Δ T_G)²+(ΔT_N-ANT)²+(ΔT_N-REF)²]^1/2

Substitute into and abbreviation,

$\mathrm{\Δ}T={\[\frac{2{(T_A^{\′}+T_{REC}^{\′})}^2+2{(T_{REF}+T_{REC}^{\′})}^2}{B\mathrm{\τ}}+\left(\frac{{\mathrm{\ΔG}}_S}{G_S}\right){(T_A^{\′}-T_{REF})}^2\]}^{1/2}---\left(4\right)$

When satisfying condition T '_A=T_REFTime, the Section 2 in formula (4) square brackets is zero, thus the impact of change in gain is completely eliminated。As T '_A=T_REFTime, radiometer is referred to as balance, and in the case, formula (4) is reduced to

$\mathrm{\Δ}T=\frac{2(T_A^{\′}+T_{REC}^{\′})}{\sqrt{B\mathrm{\τ}}}=2{\mathrm{\ΔT}}_{IDEAL}$

It is to say, be the twice of desirable total power radiometer (without change in gain) theoretic sensitivity。The reason of appearance coefficient 2 is to T '_AHalf the time has only been used in observation。

If Dicke's radiometer satisfies conditionIt is referred to as the Dicke's radiometer of balance, in formula,It it is the DC component of detecting circuit in receiver input switch half period when receiving antenna；AndIt is also adopted by similar definition。In equilibrium conditions,ThusA kind of impulsive noise conventional at present injects Dick's type radiometer。The type radiometer equipment volume is little, and it is convenient to regulate, and uses extensively。Impulsive noise injects Dick's type principle of radiometer as shown in Figure 4。Its principle is before input switch, regulates T "_AEqual to T_REF, it is achieved balance。

Diode switch is most stable of under the on and off state that it is extreme。When connecting, cause minimum decay (≈ 2.0dB), when off-state, cause maximum decay (representative value is 60dB)。In the equilibrium radiation meter that impulsive noise is injected, make use of this characteristic of diode。Feedback control circuit has encouraged a voltage controlled oscillator (VCO), and VCO is drive pulse generator again。The output of pulse generator is made up of narrow rectangular pulse, and the width of each pulse is τ_p, the repetition period is τ_R=1/f_R, f_RFor pulse recurrence frequency。When diode switch is off, obtain maximum decay, actually mask the noise that noise diode produces, at this moment T '_NIntegrated value be designated as T '_OFF。When diode switch is connected, obtain minimum decay or a big T '_NValue, is designated as T '_ON。Therefore, at whole repetition period τ_ROn,

Pulse recurrence frequency f_RShould than the square-wave modulation frequencies f of input switch_SMuch higher, thus, at τ_sMany pulses, T ' is formed during/2_NMeansigma methods be

${\stackrel{\‾}{T}}_N^{\′}={\mathrm{\τ}}_p{f}_R{T}_{ON}^{\′}+(1-{\mathrm{\τ}}_p{f}_R)T_{OFF}^{\′},$

In formula, τ_pf_RIt it is the total time that in one second, diode is converted on on-position。

If τ_pRemain constant, then f_RCan by feedback loop control with needed for providing injection antenna port(via directional coupler, the coefficient of coup is F to value_c, F_c> 1), cause the outfan of integrator forever to keep zero condition。The output indicator of this kind of radiometer is a measurement f_RFrequency counter。Noise temperature T "_AWith antenna noise temperature T '_ARelation be:

$T_A^{\′\′}=(1-\frac{1}{F_c})T_A^{\′}+\frac{T_N^{\′}}{F_c}$

(its noise temperature is T to the reference load of the front end of this kind of radiometer_REF), bonder and other radio-frequency devices, it is sealed in the box of a constant temperature, thermostat temperature is T₀。When input switch is connected to 2 end, input noise temperature T_REF=T₀=constant。In order to balance with reference load, sufficient amount of noise power to be made, be injected into antenna opening by directional coupler, so that at the upper input noise temperature T occurred of input switch (1 end of Fig. 4) "_AEqual to T_REF, it may be assumed that

T″_A=T_REF=T₀；

According to above-mentioned relation, it can be deduced that f_RWith T '_ALinear relationship between 4:

$f_R=\frac{(F_c{T}_0-T_{OFF}^{\′})-(F_c-1)T_A^{\′}}{{\mathrm{\τ}}_p(T_{ON}^{\′}-T_{OFF}^{\′})};$

General, during switching diode disconnects, the fissipation factor of attenuator is sufficiently high, it is possible to make the contribution of noise diode be reduced to negligible value, at this moment T '_OFFIt is approximately equal to T₀, thus f_RWith T '_ARelation between 4 can be written as further:

$f_R=\frac{(F_c-1)(T_0-T_A^{\′})}{{\mathrm{\τ}}_p(T_{ON}^{\′}-T_0)}---\left(5\right)$

Due to T₀It is known that in order to determine in (5) formula with T₀-T′_A4 factors being multipliedValue, as long as demarcate source a known noise temperature value on measure f_RThat's all。The measurement sensitivity of this kind of type radiometer is:

$\mathrm{\Δ}T=\frac{2(T_0+T_{REC}^{\′})}{\sqrt{B\mathrm{\τ}}}.$

Can be seen that from formula (5), Product-factorFor positive number, because F_c> 1, T '_ON> T₀(noise temperature of noise diode is more than the thermostat temperature of constant temp. box), and f_R> 0, so necessarily there being T '_A< T₀, say, that this kind of Dick's type radiometer can only measure radiation brightness lower than T₀Target。The radiation brightness scope of natural feature on a map target is typically in 0～300K, T₀It is generally less than 400K。But, when measuring radiation brightness more than T₀Thermal source or during made Target, this kind of method is just no longer applicable。

Summary of the invention

It is an object of the invention to overcome existing Dick's type radiometer can only measure radiation brightness lower than thermostat temperature T₀The defect of target, thus providing the zero balancing numeral for Dick's type radiometer of the target observation that can realize bigger temperature range to combine integrator。

To achieve these goals, the invention provides a kind of zero balancing numeral for Dick's type radiometer and combine integrator, including: ADC converting unit 1, signal combined integral device 2, Temperature numerical estimator 3, pulse generator 4 and clock synchronization unit 5；Wherein,

Described ADC converting unit 1 is connected with the radio-frequency transmitter of front end, and for the rectified signal that radio-frequency transmitter exports is carried out sample quantization, the digital signal after quantization is exported to signal combined integral device 2 by described ADC converting unit 1；The digital signal that described ADC converting unit 1 is inputted by described signal combined integral device 2 carries out sequential differentiation, segmentation combination, integral operation, compares differentiation, going to control described pulse generator 4 according to comparing differentiation result output control signal, output timing differentiates result, segmentation combination result, integral operation result and compares differentiation result extremely described Temperature numerical estimator 3；Described pulse generator 4 is controlled by described signal combined integral device 2, produces the pulse of different frequency or different duty according to the control signal of described signal combined integral device 2 output, the noise source switch that output is extremely outside；Signal combined integral device 2 described in the integrated treatment of described Temperature numerical estimator 3 is differentiated the sequential logic signal obtained by sequential, the two ends digital signal obtained by time period segmentation combination, two integrated value obtained by integral operation, equilibrium ratio relatively differentiates obtained logical judgment result, draws the radiation temperature T ' of antenna end through computing_A；Described clock synchronization unit 5 is for producing the clock sync signal of described ADC converting unit 1, signal combined integral device 2, pulse generator 4, it is ensured that the strict time synchronizing relation between described ADC converting unit 1, signal combined integral device 2, pulse generator 4。

In technique scheme, the input of described ADC converting unit 1 is connected with the detection output port of radiometer radio-frequency transmitter by radio-frequency cable, and output port is connected with described signal combined integral device 2 by low-frequency cable；ADC converting unit 1 is connected by radio-frequency cable with clock synchronization unit 5。

In technique scheme, described signal combined integral device 2 includes: sequential arbiter 21, time period dispenser 22, signal combiner 23, integrator computing unit 24, comparator 25 and balance arbiter 26；Wherein, described sequential arbiter 21 is connected with ADC converting unit 1, and digital signal ADC converting unit 1 inputted carries out sequential differentiation, it is determined that the accurate sequential relationship of antenna port signals and noise source signal so that noise source half period=antenna half period=τ_s/ 2, wherein τ_sIt it is the time of a switch periods, and the sequential logic signal 31 after processing is inputted to time period dispenser 22 and Temperature numerical estimator 3, being connected by radio-frequency cable between described sequential arbiter 21 and clock synchronization unit 5, clock synchronization unit 5 provides system-wide clock sync signal for sequential arbiter 21；Signal and the signal of antenna half period of noise source half period are split by described time period dispenser 22, and noise source signal is divided into t_onAnd t_offTwo time periods, and have t_on+t_off=τ_s/ 2, the antenna half period was divided into according to the time periodWithTwo time periods, and have The four piece of digital signals 32 split are exported to signal combiner 23 and Temperature numerical estimator 3 by described time period dispenser 22 according to strict temporal and logic relation；Described signal combiner 23 receives the four piece of digital signals that time period dispenser 22 input comes, and being reconfigured is two groups of mixed signals, t_onSection noise source signal withSection aerial signal is combined as one group, t_offSection noise source signal withSection aerial signal is combined as one group, by two groups of digital signal outputs after combination to integrator computing unit 24；Described integrator computing unit 24 receives the digital signal after two groups of restructuring that signal combiner 23 input comes, and respectively these two groups of signals is done integral operation, obtains this two segment data respectively at τ_sIntegrated value in/2 times, exports operation result 33 to comparator 25, Temperature numerical estimator 3 and pulse generator 4；Described comparator 25 receives two integral operation results of integrator computing unit 24 output, it is carried out range value and compares, and by comparative result output to balance arbiter 26；Described balance arbiter 26 receives the digital logic signal of comparator 25 output and carries out logical judgment, exports logical judgment signal 34 to Temperature numerical estimator 3, and produces control signal according to judged result, and output is described pulse generator 4 extremely。

In technique scheme, described balance arbiter 26, when generating control signal, if two integral operation results of described integrator computing unit 24 output are equal, then do not change control signal, kept identical with a upper cycle；If two integral operation results are unequal, then change control signal, thus changing output frequency or the dutycycle of described pulse generator 4。

In technique scheme, described pulse generator 4 receives the logic discrimination signal of described balance arbiter 26 output and the integral operation result of integrator computing unit 24 output, after processing by analysis, produces to control accordingly pulse, controls switching on and off of noise source switch。

It is an advantage of the current invention that:

The zero balancing numeral combination integrator for Dick's type radiometer of the present invention all obtains good application in laboratory test and the observation of outfield radiation target。Actual test result shows: this zero balancing numeral combination integrator operational excellence in Dick's type radiometer, test result is stable and has repetition concordance, it is possible to observing the atural object radiation target from 0K to several thousand K and man-made target, purposes is very extensive。And combining Dick's type radiometer volume reduction after integrator optimizes through this zero balancing numeral, structure simplifies, and runs more stable and simple operation。

Accompanying drawing explanation

Fig. 1 is the schematic diagram of total power type radiometer；

Fig. 2 is the equivalent schematic diagram of total power type radiometer；

Fig. 3 is the schematic diagram of Dick's type radiometer；

Fig. 4 is the schematic diagram that impulsive noise injects Dick's type radiometer；

Fig. 5 is the structure chart of the zero balancing numeral combination integrator for Dick's type radiometer of the present invention；

Fig. 6 is the structure chart for the signal combined integral device in the zero balancing numeral combination integrator of Dick's type radiometer of the present invention；

The zero balancing numeral for Dick's type radiometer that Fig. 7 is the present invention combines integrator application example schematic block diagram in Dick's type radiometer；

Fig. 8 is the working timing figure that the zero balancing numeral for Dick's type radiometer combines integrator。

Accompanying drawing explanation

1, ADC converting unit 2, signal combined integral device

3, Temperature numerical estimator 4, pulse generator

5, clock synchronization unit

21, sequential arbiter 22, time period dispenser

23, signal combiner 24, integrator computing unit

25, comparator 26, balance arbiter

31, four piece of digital signals of the sequential logic signal 32 of sequential arbiter output, the output of time period dispenser

33, the logical judgment signal of the digital integration signal 34 of integrator computing unit output, balance arbiter output

51, the clock sync signal of the clock sync signal 52 of ADC converting unit, sequential arbiter

53, the clock sync signal of pulse generator

Detailed description of the invention

In conjunction with accompanying drawing, the invention will be further described。

With reference to Fig. 5, the zero balancing numeral combination integrator for Dick's type radiometer of the present invention includes: ADC converting unit 1, signal combined integral device 2, Temperature numerical estimator 3, pulse generator 4 and clock synchronization unit 5；Wherein, described ADC converting unit 1 is connected with the radio-frequency transmitter of front end, and for the rectified signal that radio-frequency transmitter exports is carried out sample quantization, the digital signal after quantization is exported to signal combined integral device 2 by ADC converting unit 1；The digital signal that ADC converting unit 1 is inputted by described signal combined integral device 2 carries out sequential differentiation, segmentation combination, integral operation, compares differentiation, going to control pulse generator 4 according to comparing differentiation result output control signal, output timing differentiates result, segmentation combination result, integral operation result and compares differentiation result to Temperature numerical estimator 3；Described pulse generator 4 is controlled by signal combined integral device 2, produces the pulse of different frequency or different duty according to the control signal of signal combined integral device 2 output, and output is to outside noise source switch, so that noise source produces different make-to-break ratio states；Described Temperature numerical estimator 3 integrated treatment signal combined integral device 2 is differentiated the sequential logic signal obtained by sequential, the two ends digital signal obtained by time period segmentation combination, two integrated value obtained by integral operation, equilibrium ratio relatively differentiates obtained logical judgment result, draws the radiation temperature T ' of antenna end through computing_A；Described clock synchronization unit 5 is for producing the clock sync signal of ADC converting unit 1, signal combined integral device 2, pulse generator 4, it is ensured that the strict time synchronizing relation between ADC converting unit 1, signal combined integral device 2, pulse generator 4。

Below all parts in the integrator of the present invention is described further。

ADC converting unit 1 farther includes ADC modular converter, amplifier, wave filter。The input of ADC converting unit 1 is connected with the detection output port of radiometer radio-frequency transmitter by radio-frequency cable, and output port is connected with signal combined integral device 2 by low-frequency cable；ADC converting unit 1 is connected by radio-frequency cable with clock synchronization unit 5, and clock sync signal 51 is inputted to ADC converting unit 1 by clock synchronization unit 5 so that it is completes analog-digital conversion and sets up time synchronizing relation with other unit modules。

With reference to Fig. 6, described signal combined integral device 2 includes: sequential arbiter 21, time period dispenser 22, signal combiner 23, integrator computing unit 24, comparator 25 and balance arbiter 26；Wherein, described sequential arbiter 21 is connected with ADC converting unit 1, and digital signal ADC converting unit 1 inputted carries out sequential differentiation, it is determined that the accurate sequential relationship of antenna port signals and noise source signal so that noise source half period=antenna half period=τ_s/ 2, and the sequential logic signal 31 after processing is inputted to time period dispenser 22 and Temperature numerical estimator 3, being connected by radio-frequency cable between sequential arbiter 21 with clock synchronization unit 5, clock synchronization unit 5 provides system-wide clock sync signal for sequential arbiter 21；Signal and the signal of antenna half period of noise source half period are split by described time period dispenser 22, and noise source signal is divided into t_onAnd t_offTwo time period (t_onCorresponding to the state that noise source is connected, i.e. T '_ONState；T_offThe state that corresponding noise source disconnects, i.e. T '_OFF(or T₀) state), and have t_on+t_off=τ_s/ 2, the antenna half period was divided into according to the time periodWithTwo time periods, and haveThe four piece of digital signals 32 split are exported to signal combiner 23 and Temperature numerical estimator 3 by time period dispenser 22 according to strict temporal and logic relation；Described signal combiner 23 receives the four piece of digital signals that time period dispenser 22 input comes, and being reconfigured is two groups of mixed signals, t_onSection noise source signal withSection aerial signal is combined as one group, t_offSection noise source signal withSection aerial signal is combined as one group, by two groups of digital signal outputs after combination to integrator computing unit 24；Described integrator computing unit 24 mainly includes accumulator and smoothing filter, and integrator computing unit 24 receives the digital signal after two groups of restructuring that signal combiner 23 input comes, and respectively these two groups of signals is done integral operation, obtains this two segment data respectively at τ_sIntegrated value in/2 times, exports operation result 33 to comparator 25, Temperature numerical estimator 3 and pulse generator 4；Described comparator 25 receives two integral operation results of integrator computing unit 24 output, it is carried out range value and compares, and by comparative result output to balance arbiter 26；Described balance arbiter 26 receives the digital logic signal of comparator 25 output and carries out logical judgment, exports logical judgment signal 34 to Temperature numerical estimator 3, and produces control signal according to judged result, exports to pulse generator 4；When generating control signal, if two integral operation results of integrator computing unit 24 output are equal, then do not change control signal, kept identical with a upper cycle；If two integral operation results are unequal, then change control signal, thus changing output frequency or the dutycycle of pulse generator。

Described Temperature numerical estimator 3 farther includes: memorizer, wave filter, discriminating data device, Temperature numerical inverting module。Temperature numerical estimator 3 and sequential arbiter 21, time period dispenser 22, integrator computing unit 24, balance arbiter 26 connects, and the digital signal of these 4 modules of integrated treatment calculates antenna observed temperature T '_A。

Described pulse generator 4 farther includes: logical signal decipherer, and digit pulse forms module, pulse-modulator, amplifier。The logic discrimination signal of pulse generator 4 receiving balance arbiter 26 output and the integral operation result of integrator computing unit 24 output, after processing by analysis, produce to control accordingly pulse, control switching on and off of noise source switch。

Described clock synchronization unit 5 is for producing all clock signals needed for this zero balancing numeral combination integrator, and the clock signal of the clock signal of generation and other unit modules of radiometer keeps synchronized relation。Clock synchronization unit 5 is connected with ADC converting unit 1, sequential arbiter 21, pulse generator 4, the respectively clock sync signal 53 of the clock sync signal 51 of output DAC converting unit, the clock sync signal 52 of sequential arbiter and pulse generator, the signal of clock synchronization unit output has the characteristic of high stability, low spurious。

The zero balancing numeral for Dick's type radiometer that Fig. 7 is the present invention combines integrator application example schematic block diagram in Dick's type radiometer。This zero balancing numeral combination integrator is applied in Dick's type radiometer, simplify the structural design of radiometer radio-frequency front-end on the one hand, eliminate the reference load of radio-frequency front-end and the bonder of antenna input, eliminate the measurement unstability owing to the change of the bonder degree of coupling causes, and the front-end architecture after simplifying makes local constant temperature be more easily implemented, and reduce overall power；On the other hand, this zero balancing numeral combination integrator achieves signal restructuring flexibly, makes radiometer observed temperature scope be greatly increased。

The zero balancing numeral combination integrator for Dick's type radiometer of the present invention has large-scale temperature measurement function。Existing Dick's type radiometer measurement scope is confined to 0～T₀(K) between, due to T₀For the thermostat temperature of radio-frequency front-end thermostat module, it is generally less than 400K。And due to the fact that the mode adopting two channel signal combined integrals, it is possible to make Dick's type radiometer realize larger range of temperature survey。

Fig. 8 is the working timing figure that the zero balancing numeral for Dick's type radiometer combines integrator。It can be seen that front τ_s/ 2 half periods were that receiver connects noise source half period, rear τ_s/ 2 half periods were the half period that antenna connected by receiver。At front τ_sIn/2 half periods, total duration that noise source is connected is t_on, total duration that noise source disconnects is t_off, and have t_on+t_off=τ_s/ 2；At rear τ_sIn/2 half periods, the observed temperature of antenna remains unchanged, for T '_A。The shutoff temperature T ' of noise source_OFFFor the thermostat temperature of thermostat module, it is generally less than 400K, the connection temperature T ' of noise source_ONIt is generally hundreds of or several thousand K；The observed temperature T ' of antenna_A。According to above-mentioned Dick's type radiometer equilibrium principle, have:

$T_{ON}^{\&prime;}\&CenterDot;t_{on}+T_A^{\&prime;}\&CenterDot;t_a^2=T_{OFF}^{\&prime;}\&CenterDot;t_{off}+T_A^{\&prime;}\&CenterDot;t_a^1\&DoubleRightArrow;$

$T_A^{\&prime;}(t_a^2-t_a^1)=T_{OFF}^{\&prime;}\&CenterDot;t_{off}-T_{ON}^{\&prime;}\&CenterDot;t_{on}\&DoubleRightArrow;$

$T_A^{\&prime;}=\frac{T_{OFF}^{\&prime;}\&CenterDot;t_{off}-T_{ON}^{\&prime;}\&CenterDot;t_{on}}{t_a^2-t_a^1}$

Because $t_a^1=t_{on},t_a^2=t_{off},$ Therefore have

$T_A^{\&prime;}=\frac{T_{OFF}^{\&prime;}\&CenterDot;t_{off}-T_{ON}^{\&prime;}\&CenterDot;t_{on}}{t_{off}-t_{on}}$

According to T '_ONWith T '_OFFActual temp value, to arbitrary more than 0K and less than T '_ONT '_A, always have the t matched_onAnd t_offSo that two combined integral numerical value are equal, it is achieved zero balancing。

The zero balancing numeral combination integrator for Dick's type radiometer of the present invention simplifies the structure of existing Dick's type radiometer, improves measurement stability。The radio-frequency front-end of existing Dick's type radiometer has a noise reference load, has a bonder at antenna input。Adopt zero balancing numeral combination integrator, reference load and the bonder of existing Dick's type radiometer front end can be saved, simplify the structure of radiometer, less equipment component, eliminates the degree of coupling change of the signal fluctuation owing to the reflection of reference load port causes and the bonder impact on measuring sensitivity。

The digital combined integral mode for the zero balancing numeral combination integrator of Dick's type radiometer of the present invention makes integral measurement and balance differentiate more flexible。FPGA can be adopted to carry out digital processing and feedback control, integration duration is set flexibly, regulate noise source output duty cycle, it is possible to meet the detection demand of different ground object target。

It should be noted last that, above example is only in order to illustrate technical scheme and unrestricted。Although the present invention being described in detail with reference to embodiment, it will be understood by those within the art that, technical scheme being modified or equivalent replacement, without departure from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of scope of the presently claimed invention。

Claims (5)

1. the zero balancing numeral combination integrator for Dick's type radiometer, it is characterized in that, including: ADC converting unit (1), signal combined integral device (2), Temperature numerical estimator (3), pulse generator (4) and clock synchronization unit (5)；Wherein,

Described ADC converting unit (1) is connected with the radio-frequency transmitter of front end, rectified signal for being exported by radio-frequency transmitter carries out sample quantization, and the digital signal after quantization is by described ADC converting unit (1) output to signal combined integral device (2)；The digital signal that described ADC converting unit (1) is inputted by described signal combined integral device (2) carries out sequential differentiation, segmentation combination, integral operation, compares differentiation, going to control described pulse generator (4) according to comparing differentiation result output control signal, output timing differentiates result, segmentation combination result, integral operation result and compares differentiation result extremely described Temperature numerical estimator (3)；Described pulse generator (4) is controlled by described signal combined integral device (2), the control signal generation different frequency exported according to described signal combined integral device (2) or the pulse of different duty, output switchs to outside noise source；Signal combined integral device (2) described in the integrated treatment of described Temperature numerical estimator (3) is differentiated the sequential logic signal obtained by sequential, the two ends digital signal obtained by time period segmentation combination, two integrated value obtained by integral operation, equilibrium ratio relatively differentiates obtained logical judgment result, draws the radiation temperature T ' of antenna end through computing_A；Described clock synchronization unit (5) is used for producing the clock sync signal of described ADC converting unit (1), signal combined integral device (2), pulse generator (4), it is ensured that the strict time synchronizing relation between described ADC converting unit (1), signal combined integral device (2), pulse generator (4)。

2. the zero balancing numeral for Dick's type radiometer according to claim 1 combines integrator, it is characterized in that, the input of described ADC converting unit (1) is connected with the detection output port of radiometer radio-frequency transmitter by radio-frequency cable, and output port is connected with described signal combined integral device (2) by low-frequency cable；ADC converting unit (1) is connected by radio-frequency cable with clock synchronization unit (5)。

3. the zero balancing numeral for Dick's type radiometer according to claim 1 combines integrator, it is characterized in that, described signal combined integral device (2) including: sequential arbiter (21), time period dispenser (22), signal combiner (23), integrator computing unit (24), comparator (25) and balance arbiter (26)；Wherein, described sequential arbiter (21) is connected with ADC converting unit (1), the digital signal that ADC converting unit (1) inputs is carried out sequential differentiation, determine the accurate sequential relationship of antenna port signals and noise source signal so that noise source half period=antenna half period=τ_s/ 2, wherein τ_sIt it is the time of a switch periods, and the sequential logic signal (31) after processing is inputted to time period dispenser (22) and Temperature numerical estimator (3), being connected by radio-frequency cable between described sequential arbiter (21) and clock synchronization unit (5), clock synchronization unit (5) provides system-wide clock sync signal for sequential arbiter (21)；Signal and the signal of antenna half period of noise source half period are split by described time period dispenser (22), and noise source signal is divided into t_onAnd t_offTwo time periods, and have t_on+t_off=τ_s/ 2, the antenna half period was divided into according to the time periodWithTwo time periods, and have The four piece of digital signals (32) split are exported to signal combiner (23) and Temperature numerical estimator (3) by described time period dispenser (22) according to strict temporal and logic relation；Described signal combiner (23) receives the four piece of digital signals that time period dispenser (22) input comes, and being reconfigured is two groups of mixed signals, t_onSection noise source signal withSection aerial signal is combined as one group, t_offSection noise source signal withSection aerial signal is combined as one group, by two groups of digital signal outputs after combination to integrator computing unit (24)；Described integrator computing unit (24) receives the digital signal after two groups of restructuring that signal combiner (23) input comes, and respectively these two groups of signals is done integral operation, obtains this two segment data respectively at τ_sIntegrated value in/2 times, by operation result (33) output to comparator (25), Temperature numerical estimator (3) and pulse generator (4)；Described comparator (25) receives two integral operation results that integrator computing unit (24) exports, and it is carried out range value and compares, and exports comparative result to balancing arbiter (26)；Described balance arbiter (26) receives digital logic signal that comparator (25) exports and carries out logical judgment, by logical judgment signal (34) output to Temperature numerical estimator (3), and producing control signal according to judged result, output is described pulse generator (4) extremely。

4. the zero balancing numeral for Dick's type radiometer according to claim 3 combines integrator, it is characterized in that, described balance arbiter (26) is when generating control signal, if two integral operation results that described integrator computing unit (24) exports are equal, then do not change control signal, kept identical with a upper cycle；If two integral operation results are unequal, then change control signal, thus changing output frequency or the dutycycle of described pulse generator (4)。

5. the zero balancing numeral for Dick's type radiometer according to claim 3 combines integrator, it is characterized in that, described pulse generator (4) receives logic discrimination signal that described balance arbiter (26) exports and the integral operation result that integrator computing unit (24) exports, after processing by analysis, produce to control accordingly pulse, control switching on and off of noise source switch。