阅读说明：本技术 一种跳频星载微波辐射计射频干扰抑制方法 (Radio frequency interference suppression method for frequency hopping satellite-borne microwave radiometer ) 是由 李一楠 崔新东 王佳坤 宋广南 李鹏飞 卢海梁 杨小娇 吕容川 李�浩 于 2019-08-26 设计创作，主要内容包括：一种跳频星载微波辐射计射频干扰抑制方法,包括步骤如下：步骤1、辐射计接收机选择<Image he="97" wi="147" file="DDA0002179722610000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>频带进行正常工作,初始本振频率为f<Sub>L0</Sub>；步骤2、将开关切至匹配负载,计算得到辐射计接收机多次观测匹配负载输出的电压的方差<Image he="52" wi="106" file="DDA0002179722610000012.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>步骤3、将开关切至天线输出端口,观测得到辐射计接收机第m次观测天线时的输出电压值V<Sub>A</Sub>(m)；步骤4、根据获得的天线输出电压值V<Sub>A</Sub>(m)和观测匹配负载输出的电压的方差<Image he="53" wi="83" file="DDA0002179722610000013.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>进行RFI检测,判断是否存在RFI；步骤5、如果不存在RFI干扰,则本振不进行跳频,辐射计接收机保持工作频段；如果存在RFI干扰,则本振进行跳频。本发明的方法有效地进行射频干扰抑制,同时方法简单,处理复杂度低,对整星资源需求较低。(A radio frequency interference suppression method for a frequency hopping satellite-borne microwave radiometer comprises the following steps: step 1, radiometer receiver selection The frequency band is normally operated, and the initial local oscillator frequency is f L0 (ii) a Step 2, switching the switch to the matched load, and calculating to obtain the variance of the voltage output by the radiometer receiver for observing the matched load for multiple times And 3, switching the switch to an antenna output port, and observing to obtain an output voltage value V when the radiometer receiver observes the antenna for the m-th time A (m); step 4, according to the obtained antenna output voltage value V A (m) and observing the variance of the voltage output by the matched load Performing RFI detection to judge whether the RFI exists; step 5, if no RFI interference exists, the local oscillator does not carry out frequency hopping, and the radiometer receiver keeps the working frequency band; if the RFI interference exists, the local oscillator performs frequency hopping. The method of the invention effectively suppresses the radio frequency interference, and has the advantages of simple method, low processing complexity and low requirement on whole satellite resources.)

1. A radio frequency interference suppression method for a frequency hopping satellite-borne microwave radiometer is characterized by comprising the following steps:

step 1, radiometer receiver selection

Wherein f is₀The working center frequency of the radiometer receiver is B, and the working bandwidth of the radiometer receiver is B;

step 2, switching the switch to the matched load, continuously observing N integration times, and calculating to obtain the variance of the voltage output by the radiometer receiver for observing the matched load for multiple timesN is a positive integer;

and 3, switching the switch to an antenna output port, continuously observing the output of the antenna, and observing to obtain an output voltage value V when the radiometer receiver observes the antenna for the m-th time_A(m); m is a positive integer;

step 4, according to obtainingThe obtained output voltage value V of the antenna_A(m) and observing the variance of the voltage output by the matched load

step 5, if no RFI interference exists, the local oscillator does not carry out frequency hopping, and the radiometer receiver keeps the working frequency band; if RFI interference exists, the local oscillator performs frequency hopping, and the local oscillator frequency is converted to f_L1Radiometer receiver selection

2. The method for suppressing radio frequency interference of the frequency hopping satellite-borne microwave radiometer according to claim 1, wherein the radiometer receiver observes the variance of the voltage output by the matched load for a plurality of times:

wherein, V_U(i) Observing the output voltage value of the matched load for the ith integration time; 1,2, N; n is a positive integer.

3. The method for suppressing radio frequency interference of the frequency hopping satellite-borne microwave radiometer according to claim 1 or 2, wherein in the step 4, the criterion for determining whether the RFI exists is:

if it is notThen RFI is present, if

wherein X is a threshold factor.

4. The method for suppressing radio frequency interference of the frequency hopping satellite-borne microwave radiometer according to claim 3, wherein the threshold factor X is taken as:

wherein, T_SFor observing the bright temperature of the scene, T_RFor radiometer receiver noise temperature, T_PTo match the load physical temperature.

5. The method for suppressing the radio frequency interference of the frequency hopping satellite-borne microwave radiometer according to claim 4, wherein the frequency after frequency hopping f_L1Selection range of f_L0±4B。

6. The method for suppressing the radio frequency interference of the frequency hopping satellite-borne microwave radiometer according to claim 1, wherein N is greater than or equal to 100.

7. A frequency hopping satellite-borne radiometer receiver is characterized by comprising a switch, a low noise amplifier, a band-pass filter, a frequency mixer, an adjustable local oscillation source, an intermediate frequency filter, an intermediate frequency amplifier, an AD collector and an FPGA;

the switch periodically selects and receives signals output by the antenna or signals output by the load, the low-noise amplifier receives radio frequency microwave radiation signals output by the antenna, and bandwidth signals of the working range of the whole frequency hopping radiometer are obtained through the band-pass filter; the adjustable local oscillation source can provide local oscillation signals with any frequency, the signals are mixed to intermediate frequency through the frequency mixer, the intermediate frequency filter is used for clamping, the intermediate frequency signals are amplified to the working range of the AD collector through the intermediate frequency amplifier, the analog-to-digital change is carried out on the intermediate frequency signals through the AD collector, and the digital signals are subjected to signal processing through the FPGA; and the FPGA carries out power detection and RFI detection, if the RFI exists, the information is fed back to the adjustable local oscillator source, the adjustable local oscillator source is controlled to adjust the local oscillator output frequency, and the working frequency band of the system is changed.

8. The receiver of claim 7, wherein the criterion for determining whether the RFI exists is:

if it is not

wherein X is a threshold factor, V_A(m) is the output voltage value of the radiometer receiver when observing the antenna for the m-th time,

9. The receiver of claim 8, wherein the threshold factor X is selected from the group consisting of:

wherein, T_SFor observing the bright temperature of the scene, T_RFor radiometer receiver noise temperature, T_PTo match the load physical temperature.

10. A frequency hopping space-borne radiometer receiver according to claim 8 or 9, characterized in that the radiometer receiver observes the variance of the voltage output by the matched load a plurality of times:

wherein, V_U(i) Observing the output voltage value of the matched load for the ith integration time; 1,2, N; n is a positive integer.

Technical Field

The invention relates to a radio frequency interference suppression method.

Background

A Microwave Radiometer (Microwave Radiometer) is a passive remote sensing instrument for measuring Microwave radiation energy of a target, obtains characteristic information of the target by receiving Microwave noise radiation of the target, and obtains specific target parameters (mainly a brightness temperature value) by inverting output data, thereby knowing physical characteristics of the detected target. Essentially, a microwave radiometer is a high sensitivity, noisy receiver. The microwave radiometer receives the brightness temperature of a target, amplifies an antenna output signal to a certain power through the receiver, and then detects the antenna output signal to obtain a voltage value output by the radiometer, wherein the voltage value corresponds to the radiometer receiving power, and the brightness temperature received by the antenna aperture surface can be obtained through calibration.

Although the satellite-borne microwave radiometer generally works in a radio astronomical protection frequency band, with the enhancement of human communication activities and the increase of illegal emission, the satellite-borne microwave radiometer is easy to be interfered by man-made radio frequency from the ground in a low frequency band, particularly in the L, C, X band, so that observation data of the radiometer is unavailable, a large amount of regional data is blank, the observation capability of the satellite-borne microwave radiometer is reduced, and a certain influence is caused on numerical prediction. Moreover, with the development of 5G communication, satellite-borne passive radiation remote sensing of K, Ka and V bands faces a great challenge, and a satellite-borne RFI radio frequency interference suppression method is urgently needed to be developed to solve the problem.

The existing radio frequency suppression method has the following defects: firstly, only the suppression of narrow-band interference can be satisfied, and the suppression of broadband interference cannot be performed; secondly, the processing is complex and requires high digital signal processing resources; third, the data rate of the radiating system is increased, increasing the demand on the whole satellite resources.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method overcomes the defects of the prior art, provides the radio frequency interference suppression method for the frequency hopping satellite-borne microwave radiometer, overcomes the limitations of the prior radio frequency interference suppression method, can effectively suppress the radio frequency interference aiming at broadband and narrowband interference signals, and has the advantages of simple method, low processing complexity and low requirement on whole satellite resources.

The technical scheme adopted by the invention is as follows: a radio frequency interference suppression method for a frequency hopping satellite-borne microwave radiometer comprises the following steps:

step 1, radiometer receiver selection

The frequency band is normally operated, and the initial local oscillator frequency is f_L0；

Wherein f is₀The working center frequency of the radiometer receiver is B, and the working bandwidth of the radiometer receiver is B;

step 2, switching the switch to the matched load, continuously observing N integration times, and calculating to obtain the variance of the voltage output by the radiometer receiver for observing the matched load for multiple timesN is a positive integer;

and 3, switching the switch to an antenna output port, continuously observing the output of the antenna, and observing to obtain an output voltage value V when the radiometer receiver observes the antenna for the m-th time_A(m); m is a positive integer;

step 4, according to the obtained antenna output voltage value V_A(m) and observing the variance of the voltage output by the matched load

Performing RFI detection to judge whether the RFI exists;

step 5, if no RFI interference exists, the local oscillator does not carry out frequency hopping, and the radiometer receiver keeps the working frequency band; if RFI interference exists, the local oscillator performs frequency hopping, and the local oscillator frequency is converted to f_L1Radiometer receiver selection

The frequency band operates normally.

The radiometer receiver observes the variance of the voltage output by the matched load multiple times:

wherein, V_U(i) Observing the output voltage value of the matched load for the ith integration time; 1,2, …, N; n is a positive integer.

In step 4, the criterion for determining whether RFI exists is as follows:

if it is notThen RFI is present, if

Then RFI is not present;

wherein X is a threshold factor.

Taking a threshold factor X:

wherein, T_SFor observing the bright temperature of the scene, T_RFor radiometer receiver noise temperature, T_PTo match the load physical temperature.

Frequency f after frequency hopping_L1Selection range of f_L0±4B。

N≥100。

A frequency hopping satellite-borne radiometer receiver comprises a switch, a low noise amplifier, a band-pass filter, a frequency mixer, an adjustable local oscillation source, an intermediate frequency filter, an intermediate frequency amplifier, an AD collector and an FPGA;

the switch periodically selects and receives signals output by the antenna or signals output by the load, the low-noise amplifier receives radio frequency microwave radiation signals output by the antenna, and bandwidth signals of the working range of the whole frequency hopping radiometer are obtained through the band-pass filter; the adjustable local oscillation source can provide local oscillation signals with any frequency, the signals are mixed to intermediate frequency through the frequency mixer, the intermediate frequency filter is used for clamping, the intermediate frequency signals are amplified to the working range of the AD collector through the intermediate frequency amplifier, the analog-to-digital change is carried out on the intermediate frequency signals through the AD collector, and the digital signals are subjected to signal processing through the FPGA; and the FPGA carries out power detection and RFI detection, if the RFI exists, the information is fed back to the adjustable local oscillator source, the adjustable local oscillator source is controlled to adjust the local oscillator output frequency, and the working frequency band of the system is changed.

The decision criteria for whether RFI is present are:

if it is not

Then RFI is present, if

Then RFI is not present;

wherein X is a threshold factor, V_A(m) is the output voltage value of the radiometer receiver when observing the antenna for the m-th time,

m is a positive integer for the radiometer receiver to observe the variance of the voltage output by the matched load multiple times.

Taking a threshold factor X:

wherein, T_SFor observing the bright temperature of the scene, T_RFor radiometer receiver noise temperature, T_PTo match the load physical temperature.

The radiometer receiver observes the variance of the voltage output by the matched load multiple times:

wherein, V_U(i) Observing the output voltage value of the matched load for the ith integration time; 1,2, …, N; n is a positive integer.

Compared with the prior art, the invention has the advantages that:

the invention adopts a mode based on a frequency hopping radiometer receiver to complete on-orbit real-time RFI detection and inhibition of the satellite-borne microwave radiometer. By adopting the adjustable local oscillator, the working bandwidth of the radiometer can be flexibly changed, an RFI interference frequency band is avoided, and both narrow-band interference and broadband interference can be well detected and suppressed; the whole RFI detection algorithm is simple to process, the digital signal processing resource consumption is low, automatic detection and suppression of interference can be directly carried out on a satellite, data do not need to be downloaded to the ground for processing, and the detection performance and effectiveness are improved; the data rate of the output signals after detection is equivalent to that of the output signals of the traditional radiometer, the data volume is not additionally increased, and the requirement on a satellite platform is low.

Drawings

Fig. 1 is a block diagram of a frequency hopping radiometer receiver.

Fig. 2 is a flow chart of the operation of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

The invention adopts a mode based on a frequency hopping radiometer receiver to complete on-orbit real-time RFI detection and inhibition of the satellite-borne microwave radiometer. As shown in fig. 1, the frequency hopping satellite-borne microwave radiometer receiver is composed of a switch, a low noise amplifier, a band-pass filter, a mixer, an adjustable local oscillation source, an intermediate frequency filter, an intermediate frequency amplifier, an AD collector and an FPGA.

In the working process of the radiometer receiver, the switch can periodically select and receive signals output by the antenna or signals output by the load, the low-noise amplifier receives radio frequency microwave radiation signals output by the antenna, and bandwidth signals of the working range of the whole frequency hopping radiometer are obtained through the band-pass filter; the adjustable local oscillation source can provide local oscillation signals with any frequency, the signals are mixed to intermediate frequency through the frequency mixer, the intermediate frequency filter is used for clamping, the intermediate frequency signals are amplified to the working range of the AD collector through the intermediate frequency amplifier, the analog-to-digital change is carried out on the intermediate frequency signals through the AD collector, and the digital signals are subjected to signal processing through the FPGA; in FPGA, power detection and RFI (radio frequency interference) detection analysis can be carried out, if the RFI exists, information is fed back to the adjustable local oscillator source, the local oscillator output frequency is adjusted, the system working frequency band is changed, the frequency band which is interfered is avoided, and radio frequency interference suppression is finished.

As shown in fig. 2, a method for suppressing radio frequency interference of a frequency hopping satellite-borne microwave radiometer includes the following steps:

step 1, normal work of a radiometer receiver: radiometer receiver selection

Frequency band of where f₀Is the radiometer receiver operating center frequency, and B is the radiometer receiver operating bandwidth. Performing normal operation, wherein the initial local oscillator frequency is f_L0(for a certain radiometer receiver, the choice of initial local oscillator frequency is determined by the specifics of the radiometer receiver).

And 2, observing the matched load.

Switching to a matched load, continuously observing N (N is more than or equal to 100) integration times, and calculating to obtain the variance of the voltage output by the radiometer receiver for observing the matched load for multiple times:

wherein, V_U(i) The output voltage value of the matched load is observed for the ith integration time. 1,2, …, N; n is a positive integer;

and 3, continuously observing the output of the antenna. The switch is switched to the output port of the antenna, and the output voltage value V when the antenna is observed for the mth time by the radiometer receiver is obtained through observation_A(m) of the reaction mixture. m is a positive integer;

and 4, RFI detection. According to the obtained antenna output voltage value V_A(m) and observing the variance of the voltage output by the matched load

Calculating, judging whether RFI exists, and when the judgment criterion is:

if it is not

Then RFI is present, if

Then RFI is not present.

Wherein X is a threshold factor. The X threshold factor needs to be determined according to the radiometer receiver and the specific situation of the specific observation scene, generally, X is taken as:

wherein, T_SFor observing the bright temperature of the scene, T_RFor radiometer receiver noise temperature, T_PTo match the load physical temperature.

Step 5, if no RFI interference exists, the local oscillator does not carry out frequency hopping, and the radiometer receiver keeps the working frequency band; if there is RFI interference, the local oscillator performs frequency hopping, and the local oscillator frequency is converted to f_L1(frequency f after frequency hopping_L1Needs to be set according to the concrete conditions of the actual radiometer receiver, and in general, f_L1Selection range of f_L04B), radiometer receiver selection

The frequency band operates normally.