Analog correlation circuit of synthetic aperture radiometer receiver

Abstract

The invention provides an analog correlation circuit of a synthetic aperture radiometer receiver, and relates to the technical field of weak signal detection and processing. The circuit comprises 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 a second-order differential active filter in the high-linearity differential active filtering unit is used for carrying out noise filtering and low-noise amplification on a low-noise amplifier output signal in a differential form, and a differential signal of which the bandwidth is matched with the variation range of the amplitude of a target radiation brightness temperature signal and the amplitude meets the subsequent analog-to-digital conversion requirement is output. The high-linearity differential active filtering unit designed by the invention is realized by a second-order differential active filter formed by connecting two differential active filters in series, a low-pass filter with the cut-off frequency as low as possible filters noise in a link to the maximum extent, only the bandwidth matched with signal change is reserved, the amplitude which is two times of that of a single-ended signal can be provided, and the filtering efficiency is improved. And the linearity and the signal-to-noise ratio performance are better.

Description

Technical Field

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

[0002] The synthetic aperture radiometer does not rely on the radiation source to work. It uses multi-baseline correlation interference to observe the target radiation brightness temperature signal. It is not affected by the weather and can work in multiple frequencies, multiple polarizations, multiple perspectives, all day and all weather. It is gaining more and more attention in the field of passive remote sensing. The interferometric measurement of the synthetic aperture radiometer is realized through the internal correlation circuit. 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 related circuits are mainly digital and analog. The hardware of digital related circuits is composed of high-speed AD and FPGA, and is implemented in the form of digital domain multiplication and digital filtering after intermediate frequency digitization. The main problem is that with the increase of processing paths and instantaneous working bandwidth, the size, power consumption and cost of the equipment increase rapidly, and its use in scenarios such as airborne and satellite platforms is limited. Compared with digital related circuits, the hardware of analog related circuits is mainly composed of broadband analog multipliers and operational amplifiers, and is implemented in the form of signal analog multiplication combined with low-noise amplification and analog active filtering. It has the characteristics of large processing bandwidth, small size, low power consumption and relatively simple implementation.

[0004] However, the analog correlation circuits of existing synthetic aperture radiometer receivers cannot take into account both broadband high gain and linearity, which deteriorates the measurement accuracy. Summary of the invention

[0005] 1. Technical issues to be resolved 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 analog correlation circuit of the prior art synthetic aperture radiometer receiver cannot take into account both broadband high gain and linearity.

[0006] (II) Technical solution To achieve the above objectives, the present invention is implemented through the following technical solutions: In a first aspect, the present invention provides an analog correlation circuit of a synthetic aperture radiometer receiver, comprising 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 correlation signal output in differential form; The low noise amplification unit is used to perform low noise and high gain differential amplification on the related signal output in differential form, and output a low noise amplifier output signal in differential form; 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 amplify low noise output signals in differential form, and output a pair of differential signals whose bandwidth matches the range of variation of the target radiation brightness temperature signal amplitude and whose amplitude meets the requirements of subsequent analog-to-digital conversion.

[0007] Preferably, the high-stability power supply reference unit includes a linear 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.

[0008] Preferably, the reference voltage converter adopts 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.

[0009] Preferably, the voltage follower adopts the low noise and low distortion AD8031 with rail-to-rail output.

[0010] Preferably, the high-performance broadband multiplication unit comprises a broadband unbalanced-balanced conversion circuit, a broadband analog multiplier and an active 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.

[0011] Preferably, the broadband analog multiplier adopts the analog multiplier ADL5391, and 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.

[0012] Preferably, the low-noise amplification unit comprises a precision instrumentation amplifier with a low-noise, high-gain, fully differential rail-to-rail output.

[0013] In a second aspect, the present invention provides a synthetic aperture radiometer receiver, comprising the analog correlation circuit of the synthetic aperture radiometer receiver as described above.

[0014] (III) Beneficial effects The present invention provides an analog correlation circuit for a synthetic aperture radiometer receiver. Compared with the prior art, it has the following beneficial effects: The analog correlation circuit of a synthetic aperture radiometer receiver of the present invention comprises a high-stable power supply reference unit, a high-performance broadband multiplication unit, a low-noise amplification unit and a high-linearity differential active filter unit; wherein the high-linearity differential active filter unit comprises a second-order differential active filter formed by a first-stage differential active filter and a second-stage differential active filter connected in series, and the low-noise amplifier output signal in a differential form output by the low-noise amplifier unit is subjected to noise filtering and low-noise amplification processing by the second-order differential active filter, and the output bandwidth matches the range of variation of the target radiation brightness temperature signal amplitude, and the amplitude satisfies the differential filter output signal required by the subsequent analog-to-digital conversion. The high-linearity differential active filter unit designed by the present invention is realized by a second-order differential active filter formed by two differential active filters connected in series, and a low-pass filter with a cutoff frequency as low as possible filters out the noise in the link to the maximum extent, and only retains the bandwidth matching the signal change, which can provide an amplitude twice that of a single-ended signal, as well as better linearity and signal-to-noise ratio performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a structural diagram of the analog correlation circuit of the synthetic aperture radiometer receiver according to an embodiment of the present invention; Figure 2 A circuit diagram of an analog correlation circuit of a synthetic aperture radiometer receiver according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the single-ended active filtering to differential active filtering conversion. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The embodiment of the present application solves the technical problem that the analog correlation circuit of the existing aperture synthesis radiometer receiver cannot take into account both broadband high gain and linearity by providing an analog correlation circuit of the aperture synthesis radiometer receiver, thereby improving the measurement accuracy of the aperture synthesis radiometer receiver.

[0019] The technical solution in the embodiment of the present application is to solve the above technical problems, and the overall idea is as follows: The target radiation brightness temperature is a weak signal. To achieve high-performance detection, the receiver of the synthetic aperture radiometer not only needs to implement broadband analog correlation processing, but also needs to perform high-quality low-noise high-gain amplification and filtering on the millivolt voltage signal output by the correlation processing. The typical amplification factor of the correlation processing link is usually one thousand times, which requires the analog correlation circuit to have excellent linearity, extremely low gain drift, extremely high temperature stability and working stability while working at broadband high gain. The existing technology cannot meet the above needs at the same time. In order to make up for this gap, the embodiment of the present invention provides a broadband low-noise, high-linearity analog correlation circuit. The designed high-stability power supply reference unit provides extremely low temperature drift and extremely high temperature stability reference voltage for the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filter unit; the designed high-performance broadband multiplication unit converts the input two-way pre-stage signal into two pairs of differential signals (each pre-stage signal becomes a pair of differential signals) through a broadband unbalanced-balanced conversion circuit, and sends them to the broadband analog multiplier to implement correlation processing, so as to obtain a DC signal proportional to the target radiation intensity, and the maximum working bandwidth can support more than two gigahertz. The designed low-noise amplifier unit is used to perform low-noise and high-gain amplification on the filtered signal after correlation processing. The maximum gain of the low-noise DC amplifier circuit can reach 2000 times, and the noise level introduced by the circuit itself is less than 1mV. It has extremely low gain drift, extremely high linearity and temperature stability. The designed high-linearity differential active filter unit 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 cutoff frequency filters out the noise in the link to the maximum extent, and only retains the bandwidth that matches the signal change. The differential output can provide twice the amplitude of the single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0020] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] The embodiment of the present invention provides an analog correlation circuit of a synthetic aperture radiometer receiver, such as Figure 1 As shown, it includes a high-stable 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 processing on the two pairs of differential signals to obtain a DC signal proportional to the target radiation intensity, and perform filtering preprocessing on the DC signal to obtain a correlation signal output in differential form; The low noise amplification unit is used to perform low noise and high gain differential amplification on the output related signal in differential form, and output a low noise amplification output signal in differential form; 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 performs noise filtering and low-noise amplification on the differential low-noise amplifier output signal, and outputs a pair of differential signals (i.e., Figure 1 Filtered output signal in ).

[0022] The high linearity differential active filter unit designed in the embodiment of the present invention is implemented by a second-order differential active filter consisting of two differential active filters connected in series. A low-pass filter with a cut-off frequency as low as possible filters out the noise in the link to the maximum extent, retaining only the bandwidth matching the signal change, and can provide an amplitude twice that of a single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0023] Combine the following Figure 2 A detailed description of each unit: High stability power reference unit: The unit includes a linear regulator N1, a reference voltage converter N2 and a voltage follower N3, wherein the input end of the linear regulator N1 is directly connected to an 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 end of the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filter unit to provide a high-precision and high-stability reference reference voltage; wherein the voltage follower N3 isolates the front and rear stage circuits and provides a buffering function with load. In an embodiment of the present invention, the voltage follower N3 uses a low-distortion operational amplifier with rail-to-rail output.

[0024] 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 setting model is ADR431. The device uses ADI's temperature drift curvature correction technology and external ion implantation field effect transistor (XFET) technology to minimize the nonlinearity of the output reference voltage with temperature changes. Compared with the traditional embedded Zener reference voltage source, the maximum temperature coefficient is only 3 ppm / ℃. N3 is set to AD8031, which is a low-distortion op amp with rail-to-rail output, configured in voltage follower mode, providing a highly stable, low-temperature drift buffered isolated reference voltage output.

[0025] In the high-stability power supply reference unit, the reference voltage converter N2 and the voltage follower N3 are core components. The resistor R (R1) and the capacitor C (C4) located between the compensation port (COMP) of N2 and the output port (V-) form an RC compensation network, which can further reduce the noise burrs of the output reference voltage. In the embodiment of the present invention, the value of R1 is preferably 81KΩ, and the value of C4 is preferably 0.01uF. In the embodiment of the present invention, the high-stability power supply reference unit can provide a high-precision and high-stability reference voltage output with a buffer function at 2.5V.

[0026] High-performance wideband multiplication unit: The unit comprises a pair of broadband unbalanced-balanced conversion circuits N4 and N5, a broadband analog multiplier N6 and a passive differential low-pass filter Z1, wherein the inputs of the broadband unbalanced-balanced conversion circuits N4 and N5 are connected to the pre-stage signal input, and the outputs are respectively connected to the input differential ports X + / X - and Y + / Y - The other input differential port of N6 is connected to + / Z - Connected to the precision resistor adjustment network composed of R3, R4, R5, R6 and R7, the output differential port W of N6 + / W - It is connected to a resistor matching network composed of R8, R9, and R10, and the other end of the resistor matching network is connected to a passive differential filter Z1.

[0027] The core device of the high-performance broadband multiplication unit is the broadband analog multiplier N6 mentioned above. N6 is set as a broadband, high-performance, super-symmetric analog multiplier ADL5391 with a two-gigahertz available bandwidth. 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. / Connect to adjust the resistance of the precision resistor to change The imbalance of the broadband analog multiplier output itself can be corrected, further improving the accuracy of the output voltage of the related operation itself. N4 and N5 are set as a broadband unbalanced-balanced conversion circuit 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 broadband analog multiplier output and the passive differential low-pass filter. In the embodiment of the present invention, R8 is preferably 100Ω, and R9 and R10 are preferably 24Ω.

[0028] In the embodiment of the present invention, in order to prevent the high-frequency noise after the coherent operation from entering the subsequent low-noise amplifier unit, thereby deteriorating the noise and causing circuit instability, the passive low-pass differential filter uses an LC filter with a high stop-band suppression capability of more than MHz.

[0029] The working characteristics of the broadband multiplier are as follows (1): Z(1) in, , , , They correspond to the output and three input signals of the broadband analog multiplier respectively. Is a fixed proportional constant. Ideally, when there is no input to the three ports, the output port should be zero output. If it is not zero output, adjust the termination and the broadband analog multiplier port. and The precision resistor network corrects the output imbalance of the broadband analog multiplier itself and improves the accuracy of the output voltage of the multiplication-related operation.

[0030] Low noise amplifier unit: The unit uses a precision instrument amplifier N7 with a rail-to-rail output in a low-noise, high-gain, fully differential form, and inputs a reference voltage at its reference end. The high-precision, high-stability reference voltage with buffer isolation generated by a high-stable power supply reference unit is used to effectively ensure the stability of the output voltage under high gain conditions. The input end of the precision instrument amplifier N7 with rail-to-rail output is connected to the output end of the passive differential LC filter, and the output end of the precision instrument amplifier N7 with rail-to-rail output is connected to the post-stage high-linearity differential active filter unit. In an embodiment of the present invention, N7 is set to be a precision instrument amplifier AD8139 with extremely low gain drift, extremely high linearity and temperature stability. The low-noise amplifier unit is constructed in the form of a fully differential amplifier. R11, R12 and R13, R14 are feedback resistors respectively. Different amplification factors can be achieved by adjusting the feedback terminal resistance, and the maximum gain can reach 1000 times. In an embodiment of the present invention, R11 and R13 are preferably 0.2KΩ, and R12 and R14 are preferably 24KΩ.

[0031] The input voltage range of the low noise amplifier unit is -10mV to 0mV, and the noise level introduced by the low noise amplifier unit itself is below 1mV.

[0032] High linearity differential active filter unit: The second-order differential active filter N8 and N9 are composed of two stages of low offset and high stability operational amplifiers connected in series. The input end of the first-stage differential active filter N8 is connected to the output end of the previous-stage low-noise amplifier unit, and 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 consistent. The signal after two filtering and conditioning is sent to the signal processing system from the output end of the second-stage differential active filter to achieve maximum filtering of the noise in the link, retaining only the bandwidth that matches the amplitude variation range of the target radiation brightness temperature signal, and further amplifying the amplitude to meet the subsequent analog-to-digital conversion requirements.

[0033] The core components of the high linearity differential active filter unit are the second-order differential active filters N8 and N9. N8 and N9 are configured as differential drive amplifiers LTC1992 with low offset and high stability. In the embodiment of the present invention, an active single-ended filter is designed according to the bandwidth and out-of-band suppression requirements that match the signal changes. The active single-ended filter here is preferably a MultipleFeedback structure, and then according to Figure 3 The schematic diagram is converted into a fully differential active filter. In the embodiment of the present invention, the specific component parameters can be set to: R16 = R25 = R20 = R29 = 20kΩ, R15 = R17 = R19 = R21 = R24 = R26 = R28 = R30 = 40kΩ, and 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 capacitor C12 is determined by the integration time of the radiometer receiver, and the integration time τ = RC, the unit is ms.

[0034] From the above description, it can be seen that the high linearity differential active filter unit adopts a differential active filter design, which can provide twice the amplitude of the single-ended signal under the same power supply voltage, as well as better linearity and signal-to-noise ratio performance. At the same time, the differential active filter has an extremely high common-mode rejection ratio, which can provide good suppression for the gain drift and common-mode interference caused by the high-gain pre-amplifier. In conjunction with the buffered high-precision and high-stable reference voltage provided by the connected high-stable power supply reference unit, the linearity of the link is further improved and the gain drift is reduced.

[0035] It should be noted that, in the specific implementation process, the high-stability power supply reference unit, the high-performance broadband multiplication unit, the low-noise amplification unit and the high-linearity differential active filter unit are all realized on the same multi-layer printed circuit board (PCB) through the reflow soldering process and the use of surface mount devices (SMD). This analog related circuit has the advantages of small size, low cost, good consistency and simple debugging.

[0036] An embodiment of the present invention further provides a synthetic aperture radiometer receiver, which includes the analog correlation circuit as described above.

[0037] In summary, compared with the prior art, the present invention has the following beneficial effects: 1. The high linearity differential active filter unit designed in the embodiment of 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 maximum extent, and only retains the bandwidth matching the signal change. It can provide an amplitude twice that of a single-ended signal, as well as better linearity and signal-to-noise ratio performance.

[0038] 2. The embodiment of the present invention designs a high-precision and high-stability reference voltage with buffer isolation, which provides a reference voltage for the high-performance broadband multiplication unit, low-noise amplification unit and high-linearity differential active filter unit voltage, and effectively ensures the stability of the output voltage under high gain state.

[0039] 3. The embodiment of the present invention utilizes the extremely high common-mode rejection ratio of differential active filtering to suppress the zero drift and offset caused by the high-gain pre-amplifier, and cooperates with the high-precision and high-stable reference voltage reference with buffer isolation provided by the high-stable 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.

[0040] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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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