Anti-jamming L-band microwave remote sensing radiometer

Abstract

The application discloses an anti-interference L-band microwave remote sensing radiometer, which comprises the following components: a radio frequency receiving component, a signal control and collection component, a calibration component, a data processing and transmission component, and a miniaturized array antenna, a single-pole three-throw switch, a band-pass filter, a low-noise amplifier, a mixer, a local oscillator source, an intermediate frequency filter, an intermediate frequency amplifier and a detector; the miniaturized array antenna is used for receiving a radio frequency noise signal in a target direction; the single-pole three-throw switch is used for switching the radio frequency noise signal in the target direction, a radio frequency noise signal matched with a heat source and a radio frequency noise signal matched with a cold source respectively; the radio frequency noise signal is sequentially processed by the band-pass filter, the low-noise amplifier, the mixer, the intermediate frequency filter, the intermediate frequency amplifier and the detector; a detection signal is combined with a calibration algorithm to complete noise temperature measurement in the target direction; and the data processing and transmission component is transmitted to a platform; the radiometer has strong anti-interference capability and can be used in various scenes for searching environmental parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the fields of microwave remote sensing technology and meteorological monitoring technology, and particularly relates to an anti-interference L-band microwave remote sensing radiometer. BACKGROUND

[0002] In order to more accurately and comprehensively provide information for artificial prediction work and prevent disastrous weather, the monitoring capability of water vapor and precipitation information in the atmosphere under rainfall and non-rainfall conditions needs to be strengthened. In the existing atmospheric environmental parameter remote sensing equipment, the micro rain radar can monitor the vertical distribution and time evolution of the raindrop spectrum under rainfall conditions, monitor parameters such as precipitation rate and liquid water content, and judge the rainfall condition, so as to prevent disastrous weather and provide information for artificial prediction work.

[0003] The patent with publication number CN111095033A provides a meteorological radar device, which calculates the threat information of a storm to an object location through the results of device identification, and can accurately predict and analyze the storm in a local area, but the meteorological radar cannot realize the inversion of parameters such as integrated liquid water content, comprehensive water vapor, and dry and wet delay under non-rainfall conditions. The microwave passive radiometer can obtain atmospheric parameters such as integrated liquid water content, comprehensive water vapor, and dry and wet delay by measuring atmospheric radiation temperature, which is of great significance to the fields of weather prediction, artificial rainfall, and atmospheric science research. The patent with publication number CN115113207A discloses an atmospheric environmental parameter active and passive microwave remote sensing device, which obtains the water vapor pressure profile through the data tested by the active radar and the passive microwave radiometer, so as to realize the monitoring of atmospheric environmental parameters under rainfall and non-rainfall conditions. However, both of the two devices provided have problems such as large volume, heavy weight, high cost, complex maintenance, and poor measurement accuracy. The patent with application number CN202310890132.5 provides an L-band microwave remote sensing radiometer, which has high precision and small volume, but has some difficulties in being carried by a small unmanned aerial vehicle, and has poor anti-interference ability in a complex electromagnetic environment.

[0004] To solve the above problems, the present application provides an anti-interference L-band microwave remote sensing radiometer, which has strong anti-interference ability, small volume, and light weight, and is suitable for various application scenarios. SUMMARY

[0005] In view of the above problems, the present application provides an anti-interference L-band microwave remote sensing radiometer, which comprises:

[0006] The radio frequency receiving component comprises a miniaturized array antenna, a single-pole three-throw switch, a band-pass filter, a low-noise amplifier, a mixer, a local oscillator source, an intermediate frequency filter, an intermediate frequency amplifier, and a detector.

[0007] The signal control and acquisition component is used to control the switching of the single-pole three-throw switch and acquire the signals output by the detector.

[0008] a calibration component comprising a hot source and a cold source for providing a radio frequency noise signal for calibration;

[0009] a data processing and transmission component comprising a satellite positioning module, an external data storage card, a mobile communication module and an RJ-45 interface for processing the measurement data and transmitting to a big data analysis platform;

[0010] The miniaturized array antenna is used for receiving a radio frequency noise signal in a target direction, and the single-pole three-throw switch is used for switching the radio frequency noise signal in the target direction, the radio frequency noise signal matched with the hot source and the radio frequency noise signal matched with the cold source, respectively. The radio frequency noise signal is processed in sequence through a band-pass filter, a low-noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier and a detector, and the noise temperature measurement in the target direction is completed by combining the A / D sampling of the detected signal and the calibration algorithm of the internal hot source and cold source. The data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface.

[0011] In an optional mode, the band-pass filter is a dielectric band-pass filter, an LC band-pass filter or a cavity band-pass filter, which is used for suppressing out-of-band noise signals and radio frequency interference signals.

[0012] The low-noise amplifier has an in-band noise coefficient less than 0.6 at the working frequency and at least includes three-stage low-noise amplifiers for amplifying the radio frequency noise signals in the target direction, after the hot source matching and after the cold source matching, respectively.

[0013] In an optional mode, the mixer is used for moving the received radio frequency signal to an intermediate frequency signal by mixing with a local oscillator source.

[0014] The intermediate frequency filter includes a first-stage intermediate frequency filter and a second-stage intermediate frequency filter, which are used for suppressing intermediate frequency out-of-band noise signals and radio frequency interference signals, respectively.

[0015] In an optional mode, the detector is a Schottky detection diode, a radio frequency power detection chip or a logarithmic detector, which is used for detecting the radio frequency noise signal to output a direct current level.

[0016] The satellite positioning module is a Beidou satellite positioning module, a GPS satellite positioning module, a Galileo satellite positioning module or a GLONASS satellite positioning module, which is used for receiving a satellite positioning signal to mark a target position.

[0017] The miniaturized array antenna is a microwave array antenna, a dual-polarized horn antenna, a circularly polarized horn antenna, a waveguide slot antenna or a dipole antenna.

[0018] In an alternative way, the method further comprises:

[0019] The transmission function of the band-pass filter is adjusted in real time to suppress the radio frequency interference signal, wherein the transmission function is:

[0020]

[0021] wherein ω z is the notch frequency; ω p is the pole frequency; ζ is the damping coefficient; and s is the complex frequency variable.

[0022] In an alternative way, the method further comprises:

[0023] The notch frequency and the damping coefficient are adjusted to maximize the interference rejection ratio, wherein the expression of the adjustment is:

[0024]

[0025] wherein IRR is the interference rejection ratio; η is the adjustment coefficient; t is the time; Δt is the time step; ζ(t) is the value of the damping coefficient at time t; mod is the modulo function; ζ(t+Δt) is the value of the damping coefficient at time t+Δt; mod is the modulo function; is the partial derivative of the interference rejection ratio IRR with respect to the notch frequency ω z ; is the partial derivative of the interference rejection ratio IRR with respect to the damping coefficient ζ.

[0026] In an alternative way, the low-noise amplifier is based on Volterra series expansion to compensate for the nonlinear characteristics of the low-noise amplifier; wherein the expression of the Volterra series is:

[0027]

[0028] wherein x[n] is the input signal; y[n] is the amplitude value of the pre-distorted signal; is the Volterra kernel coefficient; N is the order of the series; K is the memory depth; ε[n] is the error term, used to model the nonlinearity that is not captured by the Volterra series; n is the time point; x[n] is the amplitude value of the input signal sampled at the time point n.

[0029] In an alternative way, the miniaturized array antenna improves the directivity of the antenna through a minimum variance distortionless response beamformer;

[0030] wherein the weight vector of the minimum variance distortionless response beamformer is:

[0031]

[0032] wherein a is a steering vector; a H is a conjugate transpose of the steering vector; R xx is a covariance matrix of the received signal, R xx = R ii + lambda x I, wherein R ii is an interference covariance matrix, lambda is a diagonal loading factor, and I is an identity matrix.

[0033] In an alternative way, the mixer adopts an image rejection mixer structure, which comprises a quadrature mixer module, a local oscillator signal generator, and an image frequency rejection circuit;

[0034] The quadrature mixer module performs in-phase / quadrature mixing on the radio frequency signal according to two mixer branches to generate an intermediate frequency signal containing a target signal and an image signal.

[0035] The local oscillator signal generator feeds its local oscillator frequency to the quadrature mixer module.

[0036] The image frequency rejection circuit performs phase adjustment and amplitude balance on the intermediate frequency signal to suppress the image frequency signal.

[0037] In an alternative way, the data processing and transmission assembly comprises a data preprocessing module, a noise temperature inversion module, a data compression module, and a communication interface driver;

[0038] The data preprocessing module performs average processing on the original data.

[0039] The noise temperature inversion module inverses the noise temperature value into a ground or atmospheric parameter through a radiation transmission model.

[0040] The communication interface driver supports a data storage card, a mobile communication network, and an RJ-45 interface.

[0041] According to the scheme provided by the application, the scheme comprises: a radio frequency receiving component, comprising a miniaturized array antenna, a single-pole three-throw switch, a band-pass filter, a low-noise amplifier, a mixer, a local oscillator source, an intermediate frequency filter, an intermediate frequency amplifier and a detector; a signal control and collection component, used for controlling the switching of the single-pole three-throw switch and collecting the signal output by the detector; a calibration component, comprising a heat source and a cold source, used for providing a radio frequency noise signal for calibration; a data processing and transmission component, comprising a satellite positioning module, an external data storage card, a mobile communication module and an RJ-45 interface, used for processing the measurement data and transmitting the measurement data to a big data analysis platform; wherein the miniaturized array antenna is used for receiving a radio frequency noise signal in a target direction, the single-pole three-throw switch is used for switching the radio frequency noise signal in the target direction, the radio frequency noise signal matched with the heat source and the radio frequency noise signal matched with the cold source respectively; the radio frequency noise signal is processed in turn by the band-pass filter, the low-noise amplifier, the mixer, the intermediate frequency filter, the intermediate frequency amplifier and the detector, the detection signal is A / D sampled and combined with the calibration algorithm of the internal heat source and the cold source, and the noise temperature measurement in the target direction is completed; the data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits the measurement data to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface. The application significantly improves the anti-interference ability and measurement precision of the L-band microwave remote sensing radiometer, has a simple structure, a smaller measurement precision volume and a lighter weight, and has stronger applicability and higher application value in the field of environmental monitoring and weather observation. Specifically, the transmission function zero point position (notch frequency and damping coefficient) of the band-pass filter is adjusted in real time through the tunable band-pass filter, the radio frequency interference signal is dynamically suppressed, and the interference rejection ratio (IRR) is maximized. The miniaturized array antenna is combined with the minimum variance distortionless response beamformer, the directivity of the antenna is improved, and the interference from the non-target direction is further suppressed. The image rejection mixer adopts the quadrature mixer and the image frequency rejection circuit, and effectively suppresses the image frequency interference. The band-pass filter and the intermediate frequency filter are used in the radio frequency receiving component, and multiple levels are used to suppress the out-of-band noise signal and the radio frequency interference signal. The heat source and the cold source are used for internal calibration, and the accuracy of the noise temperature measurement is ensured. The non-linear characteristics of the low-noise amplifier are compensated based on the Volterra series expansion. The miniaturized array antenna reduces the volume of the device. The built-in satellite positioning module can simultaneously output the latitude and longitude position information of the measurement data.

[0042] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application, the content of the specification can be implemented, and in order to make the above and other purposes, characteristics and advantages of the application more obvious and easy to understand, the specific embodiments of the application are as follows. BRIEF DESCRIPTION OF DRAWINGS

[0043] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments with reference made to the accompanying drawings. The drawings are for purposes of illustration only and are not intended to be limiting in

[0044] Figure 1 A schematic diagram of an anti-interference L-band microwave remote sensing radiometer according to an embodiment of the present application is shown;

[0045] Figure 2 A flowchart of an anti-interference L-band microwave remote sensing radiometer according to an embodiment of the present application is shown;

[0046] Figure 3 A signal processing flowchart of an anti-interference L-band microwave remote sensing radiometer according to an embodiment of the present application is shown.

[0047] Reference numerals:

[0048] 1, miniaturized array antenna, 2, cold source, 3, hot source, 4, single-pole triple-throw switch, 5, first-stage low-noise amplifier, 6, first-stage band-pass filter, 7, second-stage low-noise amplifier, 8, second-stage band-pass filter, 9, second-stage low-noise amplifier, 10, mixer, 11, first-stage intermediate frequency filter, 12, first-stage intermediate frequency amplifier, 13, second-stage intermediate frequency filter, 14, second-stage intermediate frequency amplifier, 15, satellite positioning receiving antenna and module, 16, mobile communication antenna and communication module, 17, signal processing board, 18, external data storage card, 19, RJ45 interface, 20, local oscillator source filter, 21, local oscillator source low-noise amplifier, 22, local oscillator source. DETAILED DESCRIPTION

[0049] Exemplary embodiments of the present application will be described herein below with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it is understood that the present application can be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0050] Figure 1 A schematic diagram of an anti-interference L-band microwave remote sensing radiometer according to an embodiment of the present application is shown. Specifically, as shown in Figure 1 includes:

[0051] A radio frequency receiving assembly including a miniaturized array antenna, a single-pole triple-throw switch, a band-pass filter, a low-noise amplifier, a mixer, a local oscillator source, an intermediate frequency filter, an intermediate frequency amplifier, and a detector;

[0052] A signal control and collection component is configured to control the switching of the single-pole three-throw switch and collect the signal output by the detector.

[0053] A calibration component including a hot source and a cold source is configured to provide a radio frequency noise signal for calibration.

[0054] A data processing and transmission component including a satellite positioning module, an external data storage card, a mobile communication module and an RJ-45 interface is configured to process the measurement data and transmit the data to a big data analysis platform.

[0055] The miniaturized array antenna is configured to receive a radio frequency noise signal in a target direction, and the single-pole three-throw switch is configured to switch the radio frequency noise signal in the target direction, the radio frequency noise signal matched with the hot source and the radio frequency noise signal matched with the cold source, respectively. The radio frequency noise signal is processed by a band-pass filter, a low-noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier and a detector in sequence, and the detection signal is A / D sampled and combined with the calibration algorithm of the internal hot source and cold source to complete the noise temperature measurement in the target direction. The data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits the data to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface.

[0056] In this embodiment, as shown in Figure 2 The miniaturized array antenna is configured to receive a radio frequency noise signal in a target direction, and the single-pole three-throw switch is configured to switch the radio frequency noise signal in the target direction, the radio frequency noise signal matched with the hot source and the radio frequency noise signal matched with the cold source, respectively. The radio frequency noise signal is processed by a band-pass filter, a low-noise amplifier, a mixer, an intermediate frequency filter, an intermediate frequency amplifier and a detector in sequence, and the detection signal is A / D sampled and combined with the calibration algorithm of the internal hot source and cold source to complete the noise temperature measurement in the target direction. The data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits the data to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface.

[0057] Specifically, the miniaturized array antenna is used to receive the radio frequency noise signal of the target direction. The single-pole three-throw switch is used to switch the radio frequency noise signal of the target direction, the radio frequency noise signal matched with the heat source, and the radio frequency noise signal matched with the cold source. The band-pass filter selects a medium band-pass filter, which is used to suppress the out-of-band noise signal and the radio frequency interference signal. The low-noise amplifier selects a low-noise amplifier with a noise figure less than 0.6, and at least includes three stages, which are respectively used to amplify the radio frequency noise signals of the target direction, the heat source matched, and the cold source matched. The mixer mixes the received radio frequency signal with the local oscillator source to move to the intermediate frequency signal. The intermediate frequency filter includes a first stage and a second stage intermediate frequency filter, which is used to suppress the out-of-band noise signal and the radio frequency interference signal. The intermediate frequency amplifier amplifies the intermediate frequency signal. The detector selects a Schottky detection diode, which is used to detect the radio frequency noise signal and output a direct current level. The switching of the single-pole three-throw switch is controlled, and the signal output by the detector is collected and A / D sampled. The calibration component includes a heat source and a cold source, which are used to provide the radio frequency noise signal for calibration, and the noise temperature measurement of the target direction is completed by combining the calibration algorithm of the internal heat source and the cold source. The satellite positioning module selects a Beidou satellite positioning module, which is used to receive the satellite positioning signal to mark the target position. The external data storage card is used to store the measurement data. The mobile communication module is used to transmit the measurement data through the mobile communication network. The RJ-45 interface is used to transmit the measurement data through the wired network.

[0058] As shown in Figure 1 The new anti-interference L-band microwave remote sensing radiometer includes multiple working states. In the first working state, the single-pole three-throw switch is switched to 1, the miniaturized array antenna receives the radio frequency noise signal of the target horizontal direction, and outputs 4 through the single-pole three-throw switch. The signal is amplified by the first-stage low-noise amplifier 5 and enters the first-stage band-pass filter 6 to filter out the out-of-band signal. Then, the signal is amplified by the second-stage low-noise amplifier 7, and the amplified signal is output to the second-stage band-pass filter 8 to further filter out the out-of-band signal. Then, the signal is output to the third-stage low-noise amplifier 9 to amplify the radio frequency noise signal. The amplified signal enters the mixer 10 to mix the radio frequency signal to the intermediate frequency signal, which enters the first-stage intermediate frequency filter 11 to filter out the out-of-band signal. The filtered signal is amplified by the first-stage intermediate frequency amplifier 12, and then enters the second-stage intermediate frequency filter 13 to filter out the out-of-band signal. The filtered signal is amplified by the second-stage intermediate frequency amplifier 14, and finally enters the detector to output the detection signal for measurement. The first working state is suitable for normal remote sensing measurement, which receives the radio frequency noise signal from the target area (such as the earth's surface) to obtain the radiation characteristics of the target area.

[0059] The second working state: the single-pole three-throw switch is switched to the cold source 2, the received radio frequency noise signal of the cold source is output through the single-pole three-throw switch 4, the amplified signal is input into the first-stage band-pass filter 6 through the first-stage low-noise amplifier 5, the out-of-band signal is filtered out, then the amplified signal is input into the second-stage low-noise amplifier 7, the output signal after amplification is input into the second-stage band-pass filter 8 to further filter out the out-of-band signal, then the output signal is output to the third-stage low-noise amplifier 9 to amplify the radio frequency noise signal again, the amplified output signal is input into the mixer to mix the radio frequency signal 10 into the intermediate frequency signal, the out-of-band signal is filtered out by the first-stage intermediate frequency filter 11 to ensure the interference signal, then the amplified signal is input into the second-stage intermediate frequency filter 13 to filter out the out-of-band signal to ensure the interference signal, then the amplified noise signal is input into the second-stage intermediate frequency amplifier 14, and finally the amplified noise signal is input into the detector to output the detection signal for measurement. The second working state is cold source measurement, and the applicable scene is internal calibration. The radio frequency noise signal of the known low-temperature noise source (cold source) is measured to calibrate the zero drift and low-end response of the radiometer. The cold source provides a known low-temperature reference point to help determine the behavior of the radiometer at a lower noise temperature.

[0060] The third working state: the single-pole three-throw switch is switched to the hot source 3, the received radio frequency noise signal of the hot source is output through the single-pole three-throw switch 4, the amplified signal is input into the first-stage band-pass filter 6 through the first-stage low-noise amplifier 5, the out-of-band signal is filtered out, then the amplified signal is input into the second-stage low-noise amplifier 7, the output signal after amplification is input into the second-stage band-pass filter 8 to further filter out the out-of-band signal, then the output signal is output to the third-stage low-noise amplifier 9 to amplify the radio frequency noise signal again, the amplified output signal is input into the mixer 10 to mix the radio frequency signal into the intermediate frequency signal, the out-of-band signal is filtered out by the first-stage intermediate frequency filter 11 to ensure the interference signal, then the amplified signal is input into the second-stage intermediate frequency filter 13 to filter out the out-of-band signal to ensure the interference signal, then the amplified noise signal is input into the second-stage intermediate frequency amplifier 14, and finally the amplified noise signal is input into the detector to output the detection signal for measurement. The third working state is hot source measurement, and the applicable scene is internal calibration. The radio frequency noise signal of the known high-temperature noise source (hot source) is measured. The gain and high-end response of the radiometer are calibrated. The hot source provides a known high-temperature reference point to help determine the behavior of the radiometer at a higher noise temperature.

[0061] In the present application, the cold source and the hot source are characterized to calibrate the remote sensing data, so that the accurate passive remote sensing measurement value is obtained, and the radiometer does not need temperature stability. The modeled cold source sky brightness temperature is used to characterize the response of the noise temperature to the physical temperature variation within its expected operating temperature range, so that the radiometer can be fully internally calibrated without further sky measurement. Since the mixer is used to move the radio frequency signal through the local oscillator source to the intermediate frequency signal, the out-of-band signals are filtered out by the intermediate frequency filter to ensure the interference signals. The radiometer feed receives the target radiation noise signal, the filter suppresses the out-of-band signal, and the radio frequency amplification link amplifies the noise signal to meet the input requirements of the square-law detector, and the integration amplification link amplifies the detection output for integration output. Both the radiometer link and the radiometer remote sensing measurement data are protected and accurate.

[0062] In an alternative way, the mixer is used to move the received radio frequency signal through the local oscillator to the intermediate frequency signal.

[0063] The intermediate frequency filter includes a first-stage intermediate frequency filter and a second-stage intermediate frequency filter, which are used to suppress intermediate frequency out-of-band noise signals and radio frequency interference signals, respectively.

[0064] In the present embodiment, the mixer converts the received radio frequency signal (with a higher frequency) into an intermediate frequency signal (with a lower frequency). Signal processing is performed at a lower intermediate frequency, which reduces the requirements for circuit elements (such as filters, amplifiers, etc.), simplifies circuit design and reduces costs. At the same time, the intermediate frequency signal is easier to digitize. By setting two-stage intermediate frequency filters, the intermediate frequency out-of-band noise and radio frequency interference signals are more effectively suppressed. The first-stage intermediate frequency filter provides a wider bandwidth to preliminarily suppress out-of-band noise, while the second-stage filter has a narrower bandwidth and higher selectivity, and can more accurately filter out interference signals of specific frequencies.

[0065] Specifically, the first-stage intermediate frequency filter selects an LC filter, a ceramic filter, a surface acoustic wave (SAW) filter, or a dielectric filter. The second-stage intermediate frequency filter uses a high-Q ceramic filter, a crystal filter, or a cavity filter. The two filters are cascaded together and the impedance matching between the filters is optimized to ensure that the signal can pass through the entire filter system effectively. The mixer and the intermediate frequency filter are integrated into the radio frequency receiving assembly and the signal connection between the components is ensured to be good.

[0066] In an alternative way, the detector is a Schottky detection diode, a radio frequency power detection chip, or a logarithmic detector, which is used to detect the radio frequency noise signal and output a direct current level.

[0067] The satellite positioning module is a Beidou satellite positioning module, a GPS satellite positioning module, a Galileo satellite positioning module, or a GLONASS satellite positioning module, and is configured to receive a satellite positioning signal to mark a target position.

[0068] The miniaturized array antenna is a microwave array antenna, a dual-polarized horn antenna, a circularly polarized horn antenna, a waveguide slot antenna, or a dipole antenna.

[0069] In this embodiment, the Schottky diode and the RF power detection chip have high sensitivity characteristics, can accurately detect weak RF noise signals and convert them into DC levels, can handle a variety of situations from weak to strong signals, and are suitable for different measurement environments. Low power consumption and miniaturization are suitable for embedded and portable devices. The miniaturized array antenna, such as the microwave array antenna, the dual-polarized horn antenna, the circularly polarized horn antenna, the waveguide slot antenna, and the dipole antenna, has high gain and good directivity, and can effectively receive RF noise signals in the target direction. The above antenna design is compact, light in weight, and easy to install and carry. The dual-polarized and circularly polarized antennas can receive signals of different polarizations, improving the sensitivity of signal reception.

[0070] In an alternative way, the method further comprises:

[0071] The transmission function zero point position of the band-pass filter is adjusted in real time to suppress the RF interference signal, wherein the transmission function is:

[0072]

[0073] wherein ω z is the notch frequency; ω p is the pole frequency; ζ is the damping coefficient; and s is a complex frequency variable.

[0074] In this embodiment, the conventional fixed notch filter can only suppress interference of a specific frequency. In this embodiment, the notch frequency of the band-pass filter is dynamically adjusted to suppress time-varying or frequency-varying RF interference (RFI) signals, track and suppress constantly changing interference signals. By effectively suppressing RFI, the noise floor is reduced, thereby improving the accuracy of the measurement results. By finely adjusting the notch frequency, the frequency range of the useful signal is avoided from being excessively suppressed, thereby maximizing the integrity of the target signal.

[0075] In an alternative way, the method further comprises:

[0076] The notch frequency and the damping coefficient are adjusted to maximize the interference suppression ratio, wherein the expression for adjustment is:

[0077]

[0078] wherein IRR is the interference rejection ratio; η is an adjustment factor; t is time; Δt is a time step; ζ(t) is the value of the damping coefficient at time t; mod is a modulo function; ζ(t+Δt) is the value of the damping coefficient at time t+Δt; mod is a modulo function; is the partial derivative of the interference rejection ratio IRR with respect to the notch frequency ω z . is the partial derivative of the interference rejection ratio IRR with respect to the damping coefficient ζ.

[0079] In this embodiment, the notch frequency and the damping coefficient are adjusted in real time to dynamically suppress the changing radio frequency interference signals. The influence of the interference signals on the useful signals is reduced by maximizing the interference rejection ratio. There is no need to pre-set fixed filtering parameters, and the adaptability is stronger.

[0080] In an alternative way, the low noise amplifier is based on Volterra series expansion to compensate for the nonlinear characteristics of the low noise amplifier; wherein the expression of the Volterra series is:

[0081]

[0082] wherein x[n] is the input signal; y[n] is the amplitude value of the pre-distorted signal; is the Volterra kernel coefficient; N is the order of the series; K is the memory depth; ε[n] is the error term, which is used to model the nonlinearity that is not captured by the Volterra series; n is the time point; x[n] is the amplitude value of the input signal sampled at the time point n.

[0083] In this embodiment, the Volterra series considers the memory effect and high-order nonlinear components of the signal, models and pre-compensates the nonlinear characteristics of the LNA, thereby improving the linearity of the LNA, reducing signal distortion, and ultimately improving the measurement accuracy of the radiometer.

[0084] For example, assume that the LNA operates in L-band (1-2 GHz) and exhibits significant second and third order nonlinear distortion. Measure the S-parameters of the LNA using a vector network analyzer (VNA) and characterize the AM / AM and AM / PM distortion of the LNA using the non-linear measurement function of the VNA. Select the Volterra model order (N) and memory depth (K) based on the measurement results. For example, select N=3 and K=3. Use the data measured by the VNA or generate multi-tone signals by a dedicated test equipment and use the input-output data of the LNA for estimating the Volterra kernel coefficients. Integrate the Volterra model into the signal processing unit of the radiometer (using an FPGA). Pre-distort the input signal before the LNA to compensate for the non-linearity of the LNA. Evaluate the impact of the Volterra pre-distortion on the performance of the radiometer using calibration signals and actual remote sensing data.

[0085] In an alternative way, the miniaturized array antenna improves the directivity of the antenna through a minimum variance distortionless response beamformer;

[0086] wherein the weight vector of the minimum variance distortionless response beamformer is:

[0087]

[0088] wherein a is a steering vector; a H is the conjugate transpose of the steering vector; R xx is the covariance matrix of the received signal, R xx = R ii + λ × I, where R ii is the interference covariance matrix, λ is a diagonal loading factor, and I is an identity matrix.

[0089] In this embodiment, the minimum variance distortionless response (MVDR) beamformer significantly improves the directivity of the antenna by optimizing the weight vector, reduces sidelobe interference, and thus improves the reception quality of the signal. The MVDR beamformer suppresses interference signals, especially in a multi-interference source environment, and effectively suppresses interference signals through processing of the interference covariance matrix. The MVDR beamformer dynamically adjusts the weight vector based on the covariance matrix of the received signal, adapts to different interference environments and signal characteristics, and has strong adaptability. By suppressing interference signals and improving directivity, the MVDR beamformer significantly improves the signal-to-noise ratio (SNR), thereby improving the measurement accuracy of the microwave remote sensing radiometer.

[0090] In an alternative way, the mixer adopts a mirror rejection mixer structure, which comprises a quadrature mixer module, a local oscillator signal generator and a mirror frequency rejection circuit;

[0091] The quadrature mixer module performs in-phase / quadrature mixing of the radio frequency signal according to two mixer branches respectively to generate an intermediate frequency signal containing a target signal and a mirror signal;

[0092] The local oscillator signal generator feeds its local oscillator frequency to the quadrature mixer module;

[0093] The mirror frequency rejection circuit performs phase adjustment and amplitude balance on the intermediate frequency signal to suppress the mirror frequency signal.

[0094] In the embodiment, the mixer generates a mirror frequency, which is another frequency symmetric to the target frequency with respect to the local oscillator frequency. The signal of the mirror frequency is also down-converted to the intermediate frequency by the mixer, thereby interfering with the target signal. By eliminating the mirror frequency interference, the noise temperature of the target direction is more accurately measured, thereby improving the sensitivity of the radiometer and detecting a weaker signal change.

[0095] Specifically, the quadrature mixer module contains two mixers, which respectively mix the radio frequency signal with in-phase (I) and quadrature (Q) components of the local oscillator signal (using a mixer such as Gilbert Cell structure). The input radio frequency signal is divided into two paths and input to the two mixers respectively. The local oscillator signal generator also generates two signals, one of which is 90 degrees out of phase with the other, and the two local oscillator signals are input to the two mixers respectively. The local oscillator signal generator includes in-phase and quadrature components, and generates high-quality local oscillator signals using a phase-locked loop (PLL) or direct digital frequency synthesis (DDS). The mirror frequency rejection circuit is to perform phase adjustment and amplitude balance on the intermediate frequency signals output by the two mixers, thereby realizing destructive interference of the mirror frequency signal and constructive interference of the target signal. The mirror rejection circuit includes a phase shifter, a variable gain amplifier and an adder / difference device, wherein the phase shifter is used to accurately adjust the phase relationship of the two intermediate frequency signals. The variable gain amplifier (VGA) is used to adjust the amplitude balance of the two intermediate frequency signals. The adder / difference device is used to add or subtract the two intermediate frequency signals, thereby realizing mirror rejection.

[0096] For example, assuming that the working frequency of the L-band microwave remote sensing radiometer is 1.4 GHz, and the local oscillator frequency is set to 1.3 GHz. Target frequency: 1.4 GHz; Local oscillator frequency: 1.3 GHz; Intermediate frequency: 1.4 GHz-1.3 GHz=0.1 GHz; Image frequency: 1.3 GHz-0.1 GHz=1.2 GHz; If there is no image rejection, the 1.2 GHz signal will also be mixed to the 0.1 GHz intermediate frequency, mixed with the target signal, causing measurement error. After using the image rejection mixer, the quadrature mixer module mixes the 1.4 GHz and 1.2 GHz radio frequency signals to the intermediate frequency of 0.1 GHz. Then, the image frequency rejection circuit finely adjusts the phase and amplitude of the two intermediate frequency signals. By setting the parameters of the phase shifter and VGA, the 1.2 GHz signal is canceled at the output end, while the 1.4 GHz signal is enhanced. Finally, at the output end of the mixer, the 1.2 GHz image signal is suppressed, and the 1.4 GHz target signal is retained, thereby improving the measurement accuracy of the radiometer.

[0097] In an alternative way, the data processing and transmission component comprises a data preprocessing module, a noise temperature inversion module, a data compression module and a communication interface driver;

[0098] The data preprocessing module averages the original data;

[0099] The noise temperature inversion module converts the noise temperature value measured by the radiometer into a more practically meaningful ground or atmospheric parameter (such as soil moisture, sea surface temperature, vegetation coverage, etc.) through a radiative transfer model;

[0100] The communication interface driver supports data storage cards, mobile communication networks and RJ-45 interfaces.

[0101] In this embodiment, as shown in Figure 3 The noise temperature inversion module converts the noise temperature value measured by the radiometer into a more practically meaningful ground or atmospheric parameter (such as soil moisture, sea surface temperature, vegetation coverage, etc.) through a radiative transfer model, making the remote sensing data have higher application value. The data compression module reduces the data volume, thereby reducing the storage cost and transmission bandwidth requirement, which is very important for long-term continuous observation.

[0102] The scheme provided by the application comprises: a radio frequency receiving component, including a miniaturized array antenna, a single-pole three-throw switch, a band-pass filter, a low-noise amplifier, a mixer, a local oscillator source, an intermediate frequency filter, an intermediate frequency amplifier and a detector; a signal control and collection component, used for controlling the switching of the single-pole three-throw switch and collecting the signal output by the detector; a calibration component, including a heat source and a cold source, used for providing a calibration radio frequency noise signal; a data processing and transmission component, including a satellite positioning module, an external data storage card, a mobile communication module and an RJ-45 interface, used for processing the measurement data and transmitting the measurement data to a big data analysis platform; wherein the miniaturized array antenna is used for receiving a radio frequency noise signal in a target direction, the single-pole three-throw switch is used for switching the radio frequency noise signal in the target direction, the radio frequency noise signal matched with the heat source and the radio frequency noise signal matched with the cold source respectively; the radio frequency noise signal is processed in turn by the band-pass filter, the low-noise amplifier, the mixer, the intermediate frequency filter, the intermediate frequency amplifier and the detector, the detection signal is A / D sampled and combined with the calibration algorithm of the internal heat source and the cold source, and the noise temperature measurement in the target direction is completed; the data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits the measurement data to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface. The application significantly improves the anti-interference ability and measurement precision of the L-band microwave remote sensing radiometer, has a simple structure, a smaller measurement precision volume and a lighter weight, has stronger applicability and higher application value in the field of environmental monitoring and weather observation. Specifically, the transmission function zero point position (trap frequency and damping coefficient) of the band-pass filter is adjusted in real time through the tunable band-pass filter, the radio frequency interference signal is dynamically suppressed, and the interference rejection ratio (IRR) is maximized. The miniaturized array antenna is combined with the minimum variance distortionless response beamformer, the directivity of the antenna is improved, and the interference from the non-target direction is further suppressed. The image rejection mixer adopts the quadrature mixer and the image frequency rejection circuit, and effectively suppresses the image frequency interference. The band-pass filter and the intermediate frequency filter are used in the radio frequency receiving component, and the out-of-band noise signal and the radio frequency interference signal are suppressed in multiple stages. The heat source and the cold source are used for internal calibration, and the accuracy of the noise temperature measurement is ensured. The non-linear characteristics of the low-noise amplifier are compensated based on the Volterra series expansion. The miniaturized array antenna reduces the device volume. The built-in satellite positioning module can simultaneously output the latitude and longitude position information of the measurement data.

[0103] Those skilled in the art will appreciate that the modules in the apparatuses in the embodiments can be adapted and placed in one or more apparatuses other than the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and furthermore can be divided into multiple sub-modules or sub-units or sub-components. Any combination of all the features disclosed in the present specification (including the accompanying claims, abstract and drawings), and any method or apparatus so disclosed, can be taken in any combination, except that at least some of such features and / or processes or units are mutually exclusive, unless explicitly stated otherwise. Each feature disclosed in the present specification (including the accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose, unless explicitly stated otherwise. Furthermore, the skilled person will appreciate that the combination of features of different embodiments implies that the features of the different embodiments are meant to be combined, unless explicitly stated otherwise. For example, in the claims below, any of the embodiments can be used in any combination. The application can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unitary claim, several of the devices mentioned in the embodiments can be implemented by means of one and the same hardware item. The steps of the above-described embodiments, unless explicitly stated otherwise, are not to be understood as having to be carried out in the order in which they are described.

Claims

1. An anti-jamming L-band microwave remote sensing radiometer, characterized in that, Comprise: Radio frequency receiving component, including miniaturized array antenna, single-pole three-throw switch, band-pass filter, low noise amplifier, mixer, local oscillator source, intermediate frequency filter, intermediate frequency amplifier and detector; Wherein, by adjusting the transmission function zero point position of the band-pass filter in real time to suppress radio frequency interference signals, wherein the transmission function is: wherein is the notch frequency; is the pole frequency; is the damping coefficient; is the complex frequency variable; Adjust the notch frequency and damping coefficient to maximize the interference suppression ratio, wherein the expression of adjustment is: wherein is an interference rejection ratio; is an adjustment coefficient; is a time; is a time step; is a value of a damping coefficient at a time ; is a value of a damping coefficient at a time ; is a modulo function; is a partial derivative of the interference rejection ratio IRR with respect to a notch frequency ; is a partial derivative of the interference rejection ratio IRR with respect to a damping coefficient ; The miniaturized array antenna improves the directivity of the antenna through the minimum variance distortionless response beamformer; Wherein, the weight vector of the minimum variance distortionless response beamformer is: wherein is a steering vector; is a conjugate transpose of the steering vector; is a covariance matrix of the received signal, , wherein is an interference covariance matrix, is a diagonal loading factor, is an identity matrix; The low noise amplifier is based on Volterra series expansion to compensate for the nonlinear characteristics of the low noise amplifier, and the Volterra series considers the memory effect and high-order nonlinear components of the signal, models and compensates the nonlinear characteristics of the LNA in advance; Signal control and acquisition component for controlling the switching of the single-pole three-throw switch and acquiring the signal output by the detector; Calibration component, including heat source and cold source, for providing calibration radio frequency noise signals; Data processing and transmission component, including satellite positioning module, external data storage card, mobile communication module and RJ-45 interface, for processing measurement data and transmitting to big data analysis platform; Wherein, the miniaturized array antenna is used to receive radio frequency noise signals in the target direction, and the single-pole three-throw switch is used to switch the radio frequency noise signals in the target direction, the radio frequency noise signals matched with the heat source and the radio frequency noise signals matched with the cold source respectively; the radio frequency noise signals are processed in turn through the band-pass filter, the low noise amplifier, the mixer, the intermediate frequency filter, the intermediate frequency amplifier and the detector, and the detection signal is A / D sampled and combined with the calibration algorithm of the internal heat source and cold source to complete the noise temperature measurement in the target direction; the data processing and transmission component simultaneously outputs the latitude and longitude position information of the measurement data and transmits it to the big data analysis platform through the external data storage card, the mobile communication network or the RJ-45 interface.

2. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, characterized in that, The band-pass filter is a dielectric band-pass filter, an LC band-pass filter or a cavity band-pass filter, used to suppress out-of-band noise signals and radio frequency interference signals; The low noise amplifier has an in-band noise coefficient less than 0.6 at the working frequency and at least includes three low noise amplifiers for amplifying the radio frequency noise signals in the target direction, after the heat source matching and after the cold source matching.

3. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, wherein, The mixer is used to move the received radio frequency signal to intermediate frequency signal by mixing with the local oscillator source; Wherein, the intermediate frequency filter includes a first-stage intermediate frequency filter and a second-stage intermediate frequency filter, respectively used to suppress intermediate frequency out-of-band noise signals and radio frequency interference signals.

4. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, wherein, The detector is a Schottky detection diode, a radio frequency power detection chip or a logarithmic detector, used to detect the radio frequency noise signal and output a direct current level; The satellite positioning module is a Beidou satellite positioning module, a GPS satellite positioning module, a Galileo satellite positioning module or a GLONASS satellite positioning module, used to receive satellite positioning signals to mark the target position; The small-size array antenna is a microwave array antenna, a dual-polarized horn antenna, a circularly polarized horn antenna, a waveguide slot antenna or a dipole antenna.

5. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, wherein, The expression of the Volterra series is: The mixer adopts a mirror rejection mixer structure, and the mirror rejection mixer structure comprises a quadrature mixer module, a local oscillator signal generator and a mirror frequency rejection circuit. wherein, is an input signal; is an amplitude value of a predistorted signal; is a Volterra kernel coefficient; is a series order; is a memory depth; is an error term for modeling non-linearities not captured by the Volterra series; is a time point; is an amplitude value of the input signal sampled at the time point .

6. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, wherein, The quadrature mixer module performs in-phase / quadrature mixing on the radio frequency signal according to two mixer branches to generate an intermediate frequency signal containing a target signal and a mirror signal. The local oscillator signal generator feeds a local oscillator frequency to the quadrature mixer module. The mirror frequency rejection circuit adjusts the phase and balances the amplitude of the intermediate frequency signal to suppress the mirror frequency signal. The data processing and transmission component comprises a data preprocessing module, a noise temperature inversion module, a data compression module and a communication interface driver program.

7. The anti-jamming L-band microwave remote sensing radiometer according to claim 1, wherein, The data preprocessing module averages the original data. The noise temperature inversion module inverses the noise temperature value into a ground or atmospheric parameter through a radiation transmission model; and the communication interface driver program supports a data storage card, a mobile communication network and an RJ-45 interface. ​

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