Analog correlation circuit of synthetic aperture radiometer receiver

Abstract

The present invention provides an analog correlation circuit for a synthetic aperture radiometer receiver, which relates to the technical field of weak signal detection and processing. The present invention includes a high-stability power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit, and a high-linearity differential active filtering unit; wherein, the second-order differential active filter in the high-linearity differential active filtering unit is used to filter the noise and perform low-noise amplification on the output signal of the low-noise amplifier in differential form, and output a differential signal whose output bandwidth matches the change range of the amplitude of the target radiation brightness temperature signal and whose amplitude meets the requirements of subsequent analog-to-digital conversion. The high-linearity differential active filtering unit designed by the present invention is implemented by a second-order differential active filter composed of two differential active filters connected in series. The low-pass filter with the lowest possible cut-off frequency filters out the noise in the link to the greatest extent, only retaining the bandwidth that matches the signal change, and can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance.

Description

Technical Field

[0001] The present invention relates to the technical field of weak signal detection and processing, and particularly to an analog correlation circuit for a synthetic aperture radiometer receiver. Background Art

[0002] The synthetic aperture radiometer does not rely on an irradiation source for operation. It observes the target radiation brightness temperature signal by means of multi-baseline correlation interference, is not affected by weather, and can work in multiple frequencies, multiple polarizations, multiple perspectives, all day and all weather, and has attracted increasing attention in the field of passive remote sensing. The interferometric measurement of the synthetic aperture radiometer is realized through an internal correlation circuit, and the noise, stability, and linearity of the correlation circuit directly restrict the resolution and accuracy of the temperature measurement of the radiometer. Therefore, the correlation circuit is the core component of the synthetic aperture radiometer.

[0003] In practice, the implementation forms of the correlation circuit mainly include digital and analog forms. The digital correlation circuit is composed of a high-speed AD and an FPGA in hardware, and is realized in the form of digital domain multiplication and digital filtering after intermediate frequency digitization. The main problem is that with the increase in the number of processing channels and the instantaneous working bandwidth, the volume, power consumption, and cost of the equipment increase rapidly, and its use in scenarios such as airborne and spaceborne platforms is restricted. Compared with the digital correlation circuit, the analog correlation circuit is mainly composed of a broadband analog multiplier and an operational amplifier in hardware, and is realized in the form of signal analog multiplication combined with low-noise amplification and analog active filtering, and has the characteristics of large processing bandwidth, small volume, low power consumption, and relatively simple implementation form.

[0004] However, the existing analog correlation circuit of the synthetic aperture radiometer receiver cannot balance broadband high gain and linearity, deteriorating the measurement accuracy. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides an analog correlation circuit for a synthetic aperture radiometer receiver, which solves the technical problem that the existing analog correlation circuit of the synthetic aperture radiometer receiver cannot balance broadband high gain and linearity.

[0007] (2) Technical Solutions

[0008] To achieve the above object, the present invention is realized through the following technical solutions:

[0009] In a first aspect, the present invention provides an analog correlation circuit for a synthetic aperture radiometer receiver, including a high-stability power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit, and a high-linearity differential active filtering unit;

[0010] Among them, the high-stability power reference unit is used to provide a reference voltage for the high-performance broadband multiplication unit, the low-noise amplification unit, and the high-linearity differential active filter unit voltage.

[0011] The high-performance broadband multiplication unit is used to convert two input pre-stage signals into two pairs of differential signals, perform correlation operations on the two pairs of differential signals to obtain a DC signal proportional to the target radiation intensity, and perform pre-filtering processing on the DC signal to obtain a correlation signal output in differential form.

[0012] The low-noise amplification unit is used to perform low-noise and high-gain differential amplification on the correlation signal output in differential form, and output a low-noise amplifier output signal in differential form.

[0013] The high-linearity differential active filter unit includes a second-order differential active filter formed by connecting a first-stage differential active filter and a second-stage differential active filter in series. The second-order differential active filter is used to filter out noise and perform low-noise amplification on the low-noise amplifier output signal in differential form, and output a pair of differential signals with a bandwidth matching the change range of the target radiation brightness temperature signal amplitude and an amplitude meeting the requirements of subsequent analog-to-digital conversion.

[0014] Preferably, the high-stability power reference unit includes a linear voltage regulator, a reference voltage converter, and a voltage follower.

[0015] Among them, the input end of the linear voltage regulator is directly connected to the external power supply, and the output end is connected to the input end of the reference voltage converter; the output end of the reference voltage converter is connected to the voltage follower, and the voltage follower is respectively connected to the voltage reference ends of the high-performance broadband multiplication unit, the low-noise amplification unit, and the high-linearity differential active filter unit.

[0016] Preferably, the reference voltage converter uses an ultra-low-noise voltage reference ADR431, and an RC compensation network is connected between the compensation port and the output port of the ultra-low-noise voltage reference ADR431.

[0017] Preferably, the voltage follower uses a rail-to-rail output low-noise and low-distortion AD8031.

[0018] Preferably, the high-performance broadband multiplication unit includes a broadband unbalanced-to-balanced conversion circuit, a broadband analog multiplier, and an active differential low-pass filter.

[0019] Among them, the inputs of the broadband unbalanced-to-balanced conversion circuit are respectively connected to the two pre-stage signals; the outputs are respectively connected to the input differential ports X + / X - and Y + / Y - of the broadband analog multiplier; the output port of the broadband analog multiplier is connected to the source differential low-pass filter via a resistor matching network.

[0020] Preferably, the broadband analog multiplier uses the analog multiplier ADL5391, and the input differential port of the ADL5391 / is connected to a precision resistor adjustment network, and the input end of the precision resistor adjustment network is connected to a reference voltage.

[0021] Preferably, the low-noise amplification unit includes a precision instrumentation operational amplifier with a rail-to-rail output in a low-noise and high-gain fully differential form.

[0022] In a second aspect, the present invention provides a synthetic aperture radiometer receiver, including the analog correlation circuit of the synthetic aperture radiometer receiver as described above.

[0023] (III) Beneficial effects

[0024] The present invention provides an analog correlation circuit of a synthetic aperture radiometer receiver. Compared with the prior art, it has the following beneficial effects:

[0025] The analog correlation circuit of a synthetic aperture radiometer receiver of the present invention includes a high-stability power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit, and a high-linearity differential active filtering unit; wherein, the high-linearity differential active filtering unit includes a second-order differential active filter formed by connecting a first-stage differential active filter and a second-stage differential active filter in series. The differential low-noise amplifier output signal output by the low-noise amplification unit is subjected to noise filtering and low-noise amplification processing through the second-order differential active filter, and the output bandwidth matches the change range of the amplitude of the target radiation brightness temperature signal, and the amplitude meets the requirements of subsequent analog-to-digital conversion for the differential filtered output signal. The high-linearity differential active filtering unit designed by the present invention is realized by a second-order differential active filter composed of two differential active filters connected in series. The low-pass filter with the lowest possible cut-off frequency filters out the noise in the link to the greatest extent, only retaining the bandwidth matching the signal change, and can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance. Description of the drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is the architecture diagram of the analog correlation circuit of the synthetic aperture radiometer receiver in the embodiment of the present invention;

[0028] Figure 2 This is the circuit diagram of the analog correlation circuit of the synthetic aperture radiometer receiver according to the embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the conversion from single-ended active filtering to differential active filtering. Specific embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] By providing an analog correlation circuit of a synthetic aperture radiometer receiver, the embodiment of the present application solves the technical problem that the existing analog correlation circuit of the synthetic aperture radiometer receiver cannot balance broadband high gain and linearity, and realizes the improvement of the measurement accuracy of the synthetic aperture radiometer receiver.

[0032] The technical solution in the embodiment of the present application for solving the above technical problem is generally as follows:

[0033] The target radiance temperature is a weak signal. To achieve high-performance detection, the synthetic aperture radiometer receiver not only needs to perform broadband analog correlation processing, but also needs to condition the millivolt-level voltage signal output by the correlation processing through high-quality low-noise and high-gain amplification and filtering. The typical amplification factor of the correlation processing link is usually in the thousands. This requires that the analog correlation circuit should have excellent linearity, extremely low gain drift, extremely high temperature stability and working stability while operating at broadband and high gain. The existing technologies cannot meet the above needs simultaneously. To fill this gap, the embodiments of the present invention provide a broadband low-noise and high-linearity analog correlation circuit. The designed high-stability power supply reference unit provides a reference voltage with extremely low temperature drift and extremely high temperature stability for the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filtering unit. The designed high-performance broadband multiplication unit converts the two input pre-stage signals into two pairs of differential signals through a broadband unbalanced-to-balanced conversion circuit (each pre-stage signal becomes a pair of differential signals), sends them into a broadband analog multiplier to perform correlation processing, obtains a DC signal proportional to the target radiation intensity, and can support a maximum working bandwidth of more than two gigahertz after filtering and preprocessing the DC signal. The designed low-noise amplification unit is used to perform low-noise and high-gain amplification on the filtered signal after correlation processing. The highest gain of this low-noise DC amplification circuit can reach 2000 times, the noise level introduced by the circuit itself is less than 1 mV, and it has extremely low gain drift, extremely high linearity and temperature stability. The designed high-linearity differential active filtering unit is implemented by a second-order differential active filter composed of two cascaded differential active filters. The low-pass filter with the lowest possible cut-off frequency filters out the noise in the link to the greatest extent, only retains the bandwidth matching the signal change, and the differential form output can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0034] To better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners.

[0035] The embodiments of the present invention provide an analog correlation circuit for a synthetic aperture radiometer receiver, as Figure 1 shown, including a high-stability power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit and a high-linearity differential active filtering unit;

[0036] Among them, the high-stability power supply reference unit is used to provide a reference voltage for the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filtering unit;

[0037] The high-performance broadband multiplication unit is used to convert the two input pre-stage signals into two pairs of differential signals, perform correlation processing on the two pairs of differential signals, obtain a DC signal proportional to the target radiation intensity, and perform filtering and preprocessing on the DC signal to obtain a correlated signal output in differential form;

[0038] The low-noise amplification unit is used to perform low-noise and high-gain differential amplification on the output correlation signals in differential form, and output the low-noise amplifier output signals in differential form;

[0039] The high-linearity differential active filtering unit includes a second-order differential active filter formed by connecting a first-stage differential active filter and a second-stage differential active filter in series. The second-order differential active filter is used to filter out noise and perform low-noise amplification on the low-noise amplifier output signals in differential form, and output a pair of differential signals whose bandwidth matches the variation range of the amplitude of the target radiation brightness temperature signal and whose amplitude meets the requirements of subsequent analog-to-digital conversion (i.e., Figure 1 the filtered output signal in

[0040] The high-linearity differential active filtering unit designed in the embodiment of the present invention is implemented by a second-order differential active filter composed of two differential active filters connected in series. A low-pass filter with as low a cut-off frequency as possible filters out the noise in the link to the greatest extent, only retaining the bandwidth matching the signal variation, and can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0041] The following will Figure 2 describe each unit in detail:

[0042] High-stability power supply reference unit:

[0043] This unit includes a linear voltage regulator N1, a reference voltage converter N2, and a voltage follower N3. Among them, the input end of the linear voltage regulator N1 is directly connected to the external power supply, the output end is connected to the input end of the reference voltage converter N2, the output end of the reference voltage converter N2 is connected to the voltage follower N3, and the voltage follower N3 is respectively connected to the voltage reference ends of the high-performance broadband multiplication unit, the low-noise amplification unit, and the high-linearity differential active filtering unit, providing a high-precision and high-stability reference voltage; among them, the voltage follower N3 isolates the front and rear stage circuits and provides a buffering function with load. In the embodiment of the present invention, the voltage follower N3 uses a rail-to-rail output low-distortion operational amplifier.

[0044] In the embodiment of the present invention, the reference voltage converter N2 is a reference voltage converter with extremely low temperature drift and extremely high temperature stability, and the model is set as ADR431. This device uses the temperature drift curvature correction technology of ADI Corporation and the external ion-implanted field-effect transistor (XFET) technology, which can minimize the non-linearity of the output reference voltage with temperature change. Compared with the traditional embedded Zener reference voltage source, the maximum temperature coefficient is only 3 ppm / °C. The model of N3 is set as AD8031. This device is a low-distortion operational amplifier with rail-to-rail output, configured in a voltage follower mode, providing a high-stability and low-temperature-drift buffered isolated reference voltage output.

[0045] In the high-stability power supply reference unit, the reference voltage converter N2 and the voltage follower N3 are the core devices. The resistor R (R1) and the capacitor C (C4) located between the compensation port (COMP) and the output port (V-) of N2 form an RC compensation network, which can further reduce the noise spikes of the output reference voltage. In the embodiment of the present invention, the value of R1 is preferably 81 KΩ, and the value of C4 is preferably 0.01 uF. In the embodiment of the present invention, the high-stability power supply reference unit can provide a buffered and stable high-precision high-stability reference voltage output of 2.5V.

[0046] High-performance broadband multiplication unit:

[0047] This unit includes a pair of broadband unbalanced-to-balanced conversion circuits N4 and N5, a broadband analog multiplier N6, and a passive differential low-pass filter Z1. Among them, the inputs of the broadband unbalanced-to-balanced conversion circuits N4 and N5 are connected to the previous-stage signal input, and the outputs are respectively connected to the input differential ports X + / X - and Y + / Y - of the broadband analog multiplier N6. The other input differential port Z + / Z - of N6 is connected to the precision resistor adjustment network composed of R3, R4, R5, R6, and R7. The output differential port W + / W - of N6 is connected to the resistor matching network composed of R8, R9, and R10. The other end of the resistor matching network is connected to the passive differential filter Z1.

[0048] The core device of the high-performance broadband multiplication unit is the above-mentioned broadband analog multiplier N6. N6 is set as a broadband, high-performance, and ultra-symmetric analog multiplier ADL5391 with an available bandwidth of two gigahertz. One end of the precision resistor adjustment network composed of R3, R4, R5, R6, and R7 is connected to the output of the high-stability power supply reference unit, and the other end is connected to the input differential port / of N6. By adjusting the resistance value of the precision resistor, the output imbalance of the broadband analog multiplier itself can be corrected, further improving the accuracy of the output voltage of the relevant operation. N4 and N5 are set as broadband unbalanced-to-balanced conversion circuits TC-1-13M+ with good consistency and amplitude-phase balance. The resistor matching network composed of R8, R9, and R10 realizes the impedance matching between the output of the broadband analog multiplier and the passive differential low-pass filter. In the embodiment of the present invention, the value of R8 is preferably 100 Ω, and the values of R9 and R10 are preferably 24 Ω.

[0049] In the embodiments of the present invention, in order to prevent high-frequency noise after coherent operation from entering the subsequent low-noise amplifier unit, which deteriorates the noise and causes circuit instability while doing so, a passive low-pass differential filter selects an LC filter with a high stopband suppression ability above megahertz.

[0050] Operating characteristic formula (1) of the broadband multiplier:

[0051] Z(1)

[0052] Among them, , , , respectively correspond to the signals at the output end of the broadband analog multiplier and the three input ends, is a fixed proportional constant. In an ideal state, when there is no input at the three ports, the output port should be zero output. If it is not zero output, then by adjusting the precision resistor network terminating at the ports and of the broadband analog multiplier, the self-output imbalance of the broadband analog multiplier is corrected, improving the accuracy of the output voltage of the multiplication-related operation.

[0053] Low-noise amplification unit:

[0054] This unit uses a precision instrumentation amplifier N7 with rail-to-rail output in a low-noise and high-gain fully differential form. Its reference terminal inputs a reference voltage, and uses the highly accurate and stable reference voltage with buffering and isolation generated by the high-stability power supply reference unit to effectively ensure the stability of the output voltage in the high-gain state. The input terminal of the precision instrumentation amplifier N7 with rail-to-rail output is connected to the output terminal of the passive differential LC filter, and the output terminal of the precision instrumentation amplifier N7 with rail-to-rail output is connected to the subsequent high-linearity differential active filter unit. In the embodiments of the present invention, N7 is set to a precision instrumentation amplifier AD8139 with extremely low gain drift, extremely high linearity, and temperature stability. The low-noise amplification unit is constructed in a fully differential operational amplifier form. R11, R12 and R13, R14 are feedback resistors respectively. By adjusting the feedback resistors at its feedback terminals, different amplification multiples can be achieved, and the maximum gain can reach 1000 times. In the embodiments of the present invention, the values of R11 and R13 are preferably 0.2KΩ, and the values of R12 and R14 are preferably 24KΩ.

[0055] The range of the input voltage of the low-noise amplification unit is -10mV to 0mV, and the noise level introduced by the low-noise amplification unit itself is below 1mV.

[0056] High-linearity differential active filter unit:

[0057] A second-order differential active filter N8 and N9 composed of two-stage cascaded low-offset and high-stable operational amplifiers. The input end of the first-stage differential active filter N8 is connected to the output end of the previous low-noise amplification unit. The output end of the first-stage differential active filter N8 is connected to the input end of the second-stage differential active filter N9. The parameters of the two-stage differential active filters are kept consistent. The signal after two-stage filtering and conditioning is sent from the output end of the second-stage differential active filter to the signal processing system, realizing the maximum filtering of the noise in the link, only retaining the bandwidth that matches the amplitude change range of the target radiation brightness temperature signal, and further amplifying the amplitude to meet the requirements of subsequent analog-to-digital conversion.

[0058] The core devices of the high-linearity differential active filtering unit are the above-mentioned second-order differential active filters N8 and N9. N8 and N9 are set to have low-offset and high-stable differential drive amplifiers LTC1992. In the embodiment of the present invention, an active single-ended filter is designed according to the bandwidth matching the signal change and the out-of-band rejection requirement. The active single-ended filter here is preferably in the form of MultipleFeedback (multiple feedback), and then according to Figure 3 It is converted into the form of a fully differential active filter. In the embodiment of the present invention, the specific component parameters can be set as: R16 = R25 = R20 = R29 = 20 kΩ, R15 = R17 = R19 = R21 = R24 = R26 = R28 = R30 = 40 kΩ. The high-precision reference voltage can be stabilized at 2.5V, so that the maximum output voltage of the second-stage LTC1992 is close to about 5V. In addition, the value of the capacitor C12 is determined by the integration time of the radiometer receiver. The integration time τ = RC, and the unit is ms.

[0059] As can be seen from the above description, the high-linearity differential active filtering unit adopts a differential form of active filtering design. Under the same power supply voltage, it can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance. At the same time, the differential active filtering has an extremely high common-mode rejection ratio, which can provide good suppression for the gain drift and common-mode interference brought by the high-gain pre-amplifier. Cooperating with the buffered high-precision and high-stable reference voltage provided by the connected high-stable power supply reference unit, it further improves the linearity of the link and reduces the gain drift.

[0060] It should be noted that in the specific implementation process, the high-stable power supply reference unit, the high-performance broadband multiplication unit, the low-noise amplification unit, and the high-linearity differential active filtering unit are all realized on the same multi-layer printed circuit board (PCB) by using surface mount devices (SMD) through the reflow soldering process. This analog-related circuit has the advantages of small volume, low cost, good consistency, and simple debugging.

[0061] An embodiment of the present invention also provides a synthetic aperture radiometer receiver, which includes the analog correlation circuit as described above.

[0062] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0063] 1. The high-linear differential active filter unit designed in the embodiment of the present invention is implemented by a second-order differential active filter composed of two differential active filters connected in series. A low-pass filter with as low a cut-off frequency as possible filters out the noise in the link to the greatest extent, only retaining the bandwidth matching the signal change, and can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0064] 2. The embodiment of the present invention designs a high-precision and high-stability reference voltage with buffer isolation to provide a reference voltage for the high-performance broadband multiplication unit, the low-noise amplification unit, and the high-linear differential active filter unit. It effectively ensures the stability of the output voltage in the high-gain state.

[0065] 3. The embodiment of the present invention utilizes the characteristic that the differential active filter has an extremely high common-mode rejection ratio to suppress the zero drift and offset brought by the high-gain pre-amplifier, and cooperates with the high-precision and high-stability reference voltage reference with buffer isolation provided by the high-stability power supply reference unit to further improve the linearity and temperature stability of the link, and reduce the measurement error introduced by the system itself.

[0066] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprises", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An analog correlation circuit for a synthetic aperture radiometer receiver, characterized in that: It includes a high-stability power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit and a high-linearity differential active filter unit; Among them, the high-stability power supply reference unit is used to provide a reference voltage for the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filter unit voltage; The high-performance broadband multiplication unit is used to convert the two input front-stage signals into two pairs of differential signals, and perform correlation operations on the two pairs of differential signals to obtain a DC signal proportional to the target radiation intensity, and perform pre-filtering on the DC signal to obtain a differential form of correlation output signal; The low noise amplifier unit is used for performing low noise and high gain differential amplification on the differential related output signal, and outputting a differential low noise amplifier output signal; The high linearity differential active filter unit includes a second-order differential active filter formed by a first-stage differential active filter and a second-stage differential active filter connected in series. The second-order differential active filter is used to filter out noise and perform low-noise amplification processing on the differential low-noise amplifier output signal, and the output bandwidth matches the variation range of the target radiation brightness temperature signal amplitude and the amplitude meets the requirements of subsequent analog-to-digital conversion.

2. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 1, characterized in that: The high-stability power supply reference unit includes a linear voltage regulator, a reference voltage converter and a voltage follower; Among them, the input end of the linear regulator is directly connected to the external power supply, and the output end is connected to the input end of the reference voltage converter; the output end of the reference voltage converter is connected to the voltage follower, and the voltage follower is respectively connected to the voltage reference ends of the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filter unit.

3. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 2, characterized in that: The reference voltage converter adopts an ultra-low noise voltage reference device ADR431, and an RC compensation network is connected between a compensation port and an output port of the ultra-low noise voltage reference device ADR431.

4. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 2, characterized in that: The voltage follower adopts the low noise and low distortion AD8031 with rail-to-rail output.

5. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 1, characterized in that: The high-performance broadband multiplication unit comprises a broadband unbalanced-balanced conversion circuit, a broadband analog multiplier and a source differential low-pass filter; The input of the broadband unbalanced-balanced conversion circuit is connected to two front-stage signals respectively; the output is connected to the input differential port X of the broadband analog multiplier respectively. + / X - and Y + / Y - The output port of the broadband analog multiplier is connected to the source differential low-pass filter via a resistor matching network.

6. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 5, characterized in that: The broadband analog multiplier adopts the analog multiplier ADL5391. The input differential port of ADL5391 / A precision resistor adjustment network is connected, and an input end of the precision resistor adjustment network is connected to a reference voltage.

7. The analog correlation circuit of the synthetic aperture radiometer receiver according to claim 1, characterized in that: The low noise amplification unit includes a precision instrumentation amplifier with a low noise, high gain, fully differential rail-to-rail output.

8. A synthetic aperture radiometer receiver, characterized in that: The invention comprises an analog correlation circuit of a synthetic aperture radiometer receiver as described in any one of claims 1 to 7.

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