Measurement method of space electromagnetic field intensity

Abstract

The invention relates to the field of space electromagnetic wave intensity measurement, in particular to a space electromagnetic field intensity measurement method. The space electromagnetic field intensity of the radiation source is measured, the space coordinate information and the time mark information are recorded in real time, and the space magnetic field distribution condition of the radiation source is drawn by using the measured data after the measurement is completed. According to the method, the space reachability of the unmanned aerial vehicle is combined with the electromagnetic wave intensity measuring equipment to form the space electromagnetic wave intensity measuring equipment, so that the radar antenna emission lobe can be measured; the method can also be used for drawing the spatial synthesis magnetic field intensity distribution condition under a plurality of identical radiation sources, and solves the problem that the synthesis magnetic field of a plurality of radiation sources is difficult to test.

Description

Technical Field

[0001] The invention relates to the field of space electromagnetic field intensity measurement and unmanned aerial vehicles, and in particular to a method for measuring space electromagnetic field intensity. Background Art

[0002] With the development of modern electronic countermeasure technology, radar decoy system has been widely used as an effective means for radar to counter anti-radiation missile (ARM). GJB7210-2011 and other national military standards stipulate that radar decoy must be able to cover the average sidelobe power of the protected radar, which requires testing the transmission lobe of the radar antenna to obtain the average sidelobe when the radar is working normally.

[0003] Radar antenna emission lobe measurement Currently, there is no equipment that can complete the antenna lobe test of the radar antenna when it radiates normally at a low cost, conveniently and quickly. Darkroom testing has high costs and long test cycles, and it is impossible to directly obtain the actual measured data of the antenna's emission lobe when the radar is transmitting normally. When using an elevated tower for field testing, due to the height and limitations of the elevated tower, the test of the radar lobe is mostly biased towards the horizontal lobe, and the radar antenna pitch lobe test cannot be completed. At present, the use of large-load drones carrying equipment such as spectrum analyzers can test the lobe of the radar pitch surface, but there are problems such as high test difficulty, difficulty in data collection and high cost. The method of using drones to conduct field antenna testing is becoming more and more perfect, but there is still a lack of a low-cost, convenient measurement device that can directly measure and store the intensity of electromagnetic waves in space. Summary of the invention

[0004] In view of the shortcomings of the background technology, the purpose of the present invention is to provide a method for measuring the electromagnetic field strength in space. The present invention uses a drone as a carrier to measure the transmission lobe in the far field area of ​​the radar antenna radiation. The measurement range is large enough to cover the radar lobe amplitude range. The microwave signal of the three receiving branches is measured after passing through a linear detector, which increases the frequency band coverage.

[0005] The technical solution of the present invention is: a method for measuring the strength of a spatial electromagnetic field, characterized in that it comprises the following steps:

[0006] Step 1. Determine the operating frequency band of the measurement device;

[0007] Step 2. Divide the antenna signal into multiple paths after it enters the receiving channel, at least into 3 paths;

[0008] Step 3. First, coupler 1 is used to divide the receiving channel into branch 1 (coupling branch) and a straight-through branch;

[0009] Step 4. The through branch is divided into branch 2 and branch 3 through coupler 2, and the measurement range of branch 2 and the through branch remains unchanged;

[0010] Step 5. Add an amplifier circuit to branch 3 to increase the measurement range;

[0011] Step 6. After the microwave signals of the three receiving branches pass through the linear detector, the detection signals are sent to the AD sampling interface of the microprocessor, and the detection voltage is quantized under the action of the high-stability sampling clock; when the microwave signal strength entering the antenna is [10dBm, 40dBm], only the receiving branch 1 can detect and output normally, and the branches 2 and 3 are both in a saturated state; when the microwave signal strength entering the antenna is [-20dBm, 10dBm], only the receiving branch 2 can detect and output normally, the through branch 1 has a detection output of 0 due to the low amplitude of the microwave signal, and the branch 3 is in a saturated state; when the microwave signal strength entering the antenna is [-50dBm, -20dBm], only the receiving branch 3 can detect and output normally, and the through branch 1 and branch 2 have a detection output of 0 due to the low amplitude of the microwave signal;

[0012] Step 7. By detecting the output values ​​of the three receiving channels, the real-time amplitude of the microwave signal entering from the antenna is obtained.

[0013] The beneficial effects of the present invention are: A. Large measurement range: When measuring the same radar emission lobe, no additional operation and parameter setting are required when facing beams with different gains. After setting the flight route of the drone, the equipment can complete the collection of required data at one time; B. Strong versatility: The product fully considers the emission lobe test requirements of radars of different models working in the same frequency band; C. The equipment is small in size and light in weight. The equipment volume and weight are much smaller than those of spectrum analyzers and other equipment, and the load requirements for the drone carrying the equipment are relatively low. D. Continuous working ability: The equipment has a large data storage space, which can access test data in real time and read the data after the test is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a block diagram of the present invention.

[0015] Figure 2 This is a block diagram of the electromagnetic wave intensity measurement device of the present invention.

[0016] Figure 3 This is a principle block diagram of the simulation unit of the present invention.

[0017] Figure 4 This is a principle block diagram of the digital unit of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings.

[0019] like Figures 1 to 4As shown, a method for measuring the spatial electromagnetic field strength of the present invention takes a measuring device capable of measuring the L-band, omnidirectional antenna gain of 0dB, [-50dBm, 40dBm], 90dB amplitude range as an example, and the method is as follows:

[0020] Step 1. Determine the operating frequency band of the measuring device and select microwave devices with appropriate operating frequency band;

[0021] Step 2. Divide the antenna signal into multiple paths after it enters the receiving channel, at least into 3 paths;

[0022] Step 3. First, the receiving channel is divided into a coupling channel (receiving branch 1) and a straight-through channel through a -30dB coupler (coupler 1). Coupler 1 allows receiving branch 1 to process microwave signals with an amplitude range of [10dBm, 40dBm] entering from the antenna; at this time, the straight-through channel can process microwave signals with an amplitude of [-20dBm, 10dBm] entering from the antenna. At this time, under the action of receiving branch 1 and the straight-through channel, the microwave amplitude that the device can measure is expanded to [-20dBm, 40dBm], and the measurement range reaches 60dB;

[0023] Step 4. The through channel is further divided into receiving branch 2 and receiving branch 3 through a -10dB coupler (coupler 2). The measurement range of branch 2 and the through channel remains unchanged. Receiving branch 1, branch 2, and branch 3 correspond to channel 1, channel 2, and channel 3, respectively.

[0024] Step 5. A 40dB amplifier circuit is added to branch 3, and its saturated output amplitude is 10dBm. The amplitude range of the microwave signal that can be measured by branch 3 from the antenna is [-50dBm, -20dBm]. At this time, under the action of receiving branch 1, branch 2, and branch 3, the microwave amplitude that the device can measure is expanded to [-50dBm, 40dBm], and the measurement range reaches 90dB;

[0025] Step 6. After the microwave signals of the three receiving branches (receiving branch 1, branch 2, and branch 3) pass through the linear detector, the detection signal is sent to the AD sampling interface of the microprocessor, and the detection voltage is quantized under the action of the high-stability sampling clock. If the amplitude of the microwave signal entering from the antenna is between [-50dBm, 40dBm], the receiving channel can be measured. When the microwave signal strength entering the antenna is [10dBm, 40dBm], only receiving branch 1 can detect and output normally, while branches 2 and 3 are both in a saturated state; when the microwave signal strength entering the antenna is [-20dBm, 10dBm], only receiving branch 2 can detect and output normally, while branch 1 has a detection output of 0 due to the low amplitude of the microwave signal, and branch 3 is in a saturated state; when the microwave signal strength entering the antenna is [-50dBm, -20dBm], only receiving branch 3 can detect and output normally, while branches 1 and 2 have a detection output of 0 due to the low amplitude of the microwave signal;

[0026] Step 7. By detecting the output values ​​of the three receiving channels, the quantized effective voltage detection voltage value can be determined at this time, and the channel compensation value of the effective value output channel (30dB for direct branch 1, 0dB for branch 2, and -30dB for branch 3) can be added to obtain the real-time amplitude of the microwave signal entering from the antenna. Dividing the channel into three is ideal in terms of processing. In engineering practice, it is also necessary to pay attention to the amplitude measurement processing at the two breakpoints in the middle, namely 10dBm and -20dBm. In order to ensure that there is no gap in the amplitude measurement at the segment, the amplitude of the segment needs to be fine-tuned so that the two adjacent measurement ranges overlap slightly. At this time, the output data of the two adjacent channels are valid. The average of the two output values ​​can be taken in the program processing, and whether the equipment is working properly can be judged based on whether the two output data are consistent.

[0027] The present invention may also include the following steps:

[0028] Step 8. Install and fix the measuring device on the drone. If the drone has a data transmission port, the data of the drone can be transmitted to the measuring device. The measuring device can read the latitude and longitude coordinates, altitude, time scale and other information of the drone as backup information for data processing;

[0029] Step 9. Send the latitude and longitude coordinates, altitude or time scale information of the high-precision Beidou module to the microprocessor of the measuring equipment. The microprocessor outputs the measured time microwave amplitude signal and the signal output by the high-precision Beidou module according to the specified data rate (the data rate is controlled by the sampling program inside the microprocessor, and the data rate is adjustable) (according to actual needs, the amount of sampling data is controlled). The output batch data includes: longitude and latitude coordinates, altitude, time scale, signal amplitude (dB);

[0030] Step 10. The microprocessor stores the generated data into FLASH according to a certain data length and time relationship. After the measurement is completed, the tester will export the test data and draw the spatial synthetic magnetic field distribution diagram of the radar antenna radiation lobe or multiple radiation sources according to the test data.

[0031] The present invention is based on modular design, separates the functions of the analog unit and the digital unit, adopts a multi-branch design for the receiving channel of the analog unit, and expands the measuring microwave amplitude range thereof.

[0032] like Figure 3 and Figure 4 As shown, a device for measuring electromagnetic field strength in space based on an unmanned aerial vehicle of the present invention includes an analog unit and a digital unit. The analog unit includes an omnidirectional receiving antenna and a receiving channel. The receiving channel includes at least three receiving channel branches. The output of the omnidirectional receiving antenna is connected to the receiving channel coupler, one output of the receiving channel coupler is connected to the first limiter, the output of the first limiter is connected to the first bandpass filter, the output of the first bandpass filter is connected to the first detector, and the output of the first detector is connected to the AD port 1 processed by the digital unit. Another output of the receiving channel coupler is connected to the power divider, one output of the power divider is connected to the second limiter, the output of the second limiter is connected to the second bandpass filter, the output of the second bandpass filter is connected to the second detector, and the output of the second detector is connected to the AD port 2 processed by the digital unit. Another output of the power divider is connected to the third limiter, the output of the third limiter is connected to the low noise amplifier, the output of the low noise amplifier is connected to the third bandpass filter, the output of the third bandpass filter is connected to the first amplifier, the output of the first amplifier is connected to the matching attenuator, the output of the matching attenuator is connected to the second amplifier, the output of the second amplifier is connected to the third detector, and the output of the third detector is connected to AD port 3 processed by the digital unit.

[0033] The first detector, the second detector and the third detector of the present invention are linear detectors.

[0034] Each receiving channel branch of the present invention has a linear detector to detect the amplitude of the microwave signal entering the detector. The detection amplitude range of the linear detector is usually -20dBm to 10dBm, and the detection amplitude range is 30dB. Taking a certain model of radar as an example, the radar transmission power is 16kW, the antenna gain is 33dB, the maximum side lobe of the antenna is -30dBc, and the minimum side lobe is about -70dBc. The far field distance of the radar is (D is the maximum size of the radar array aperture, λ is the wavelength), when D is 6.5m, the far field distance is 395m, and R is 500m. According to the radar radiation power density formula (P t Radar transmit power, G tAntenna gain, R is the distance to the radar), it can be calculated that the power density of the main lobe, maximum side lobe, and minimum side lobe at a distance of 500m are 34dBm / m 2 , 4dBm / m 2 、-36dBm / m 2 If the measuring device has only one receiving channel and one linear detector, the measuring range is only 30dB, which cannot meet the measurement requirements of the radar beam amplitude range of 70dB. By expanding the receiving channels of the measuring device and allowing each receiving channel branch to measure microwave signals in different ranges, the problem of insufficient detection capability of a single linear detector can be solved.

[0035] The digital unit of the present invention includes a microprocessor, a high-stable crystal oscillator, a high-precision Beidou positioning module, FLASH and a communication interface. With the microprocessor as the data processing core, the detection voltage output by the receiving channel is sent to the AD sampling interface of the microprocessor for sampling; the high-stable crystal oscillator provides a stable sampling clock for the microprocessor; the high-precision Beidou positioning module transmits the spatial coordinate information and time scale information of the device to the microprocessor in real time; FLASH is used to store real-time data generated by the microprocessor; the communication interface is used to read and erase the data in the FLASH, and send the spatial coordinate information and time scale information output by the drone into the device as backup data during data processing. The measuring device can be combined with the human-machine device, and the spatial accessibility of the drone is used to send the device to any area of ​​interest to measure the electromagnetic field strength of the space, and automatically record the measurement results.

[0036] The analog unit of the present invention, namely the receiving channel module, is the core part of the present invention and is also a replaceable part for expanding the applicable frequency band of the device. It uses the design scheme of expanding the receiving channel to expand the detection amplitude range several times to about 90dB, overcoming the drawbacks of the single linear detector that the detection amplitude range is insufficient and cannot completely cover the radar antenna transmission lobe amplitude range. At the same time, after quantizing the detection signals output by the corresponding receiving channel branches using the microprocessor AD sampling interface, a comprehensive judgment is made on each sampling value, and the channel compensation value of the branch is added to obtain the final measurement result.

[0037] The measurement capability of the measuring equipment with a large dynamic range can meet the test of radar emission lobes and the test and drawing of spatial synthetic magnetic fields of multi-transmitter systems. The measuring equipment is fixed on the drone. When the operator flies according to a pre-planned path or an arbitrary path, the microwave signal received from the omnidirectional antenna on the equipment enters the receiving channel, and then enters the three receiving channel branches according to the signal distribution circuit of the receiving channel. The three receiving channel branches process the incoming signals and then send the signals to the microprocessor for analog / digital conversion. At the same time, the high-stability clock circuit provides a stable and reliable sampling clock signal for the microprocessor, and the high-precision Beidou positioning module sends the longitude, altitude, time scale and other information of the spatial position of the equipment to the microprocessor. The microprocessor makes a comprehensive judgment on the input signals of the three receiving channel branches, and then processes the high-precision Beidou module, drone data, etc. Finally, the complete test data includes longitude, latitude, altitude (Beidou module built into the equipment); longitude, latitude, altitude (provided by the drone); electromagnetic field strength (unit dBm / m 2 ); time information, etc. are stored in FLASH. After the equipment completes the test, the data is exported through the communication interface, and then the data is processed to obtain the antenna transmission lobe diagram or the spatial electromagnetic field distribution diagram.

[0038] The devices and modules used in the measuring equipment can be purchased on the market. Currently, the relevant mature devices or modules are small in size and weight. By analogy with the size and weight of single-channel microwave measuring equipment, the weight of the measuring equipment is no more than 500g, the volume is no more than 150mm×100mm×30mm, and the antenna weight is no more than 50g.

[0039] During the working process of the present invention, it is assumed that the gain of the omnidirectional receiving antenna of the microwave measuring device is 0 dB. The working conditions of each branch when different transmitting lobes enter the three branches are analyzed.

[0040] The antenna main lobe energy enters the measurement equipment: receiving channel branch 1. The function of the coupler is used to allow the high-power microwave signal to enter the receiving channel main channel, and only allow weak signals to enter the receiving channel branch 1. Assuming that the coupling degree of the coupler is -30dB, the amplitude of the microwave signal of the radar main lobe entering the receiving channel branch 1 is 4dBm (channel loss is not considered here), which is just within the detection range of the linear detector. At this time, the amplitude of the microwave signal entering the receiving channel branch 2 and the receiving channel branch 3 is 34dBm and 24dBm. Under the action of the limiter, the input amplitude is limited to 10dBm. The detection amplitude of the receiving channel branch 2 and the receiving channel branch 3 is in a saturated output state, but it will not damage these two branches.

[0041] When the energy of the maximum sidelobe enters the measuring device: the amplitude of the microwave signal entering the receiving channel branch 1 under the action of the coupler is -26dBm, which is below the amplitude that the detector can effectively detect, and the detection output value is zero. At this time, the amplitude of the amplitude signal entering the receiving channel branch 2 is 4dBm, which is within the detection amplitude range of the receiving channel branch 2; the amplitude of the signal entering the receiving channel branch 3 is -6dBm, and the receiving channel branch 3 contains a linear amplifier circuit (amplification factor is 40dB, saturation output value is 10dBm), at this time the output power of the amplifier circuit of branch 3 is saturated, and the output of the detector is in a saturated state.

[0042] When the energy at the minimum sidelobe enters the measuring device: the amplitude of the microwave signal entering the receiving channel branch 1 under the action of the coupler is -66dBm, which is below the amplitude that the detector can effectively detect, and the detection output value is zero. At this time, the amplitude entering the receiving channel branch 2 is -36dBm, which is below the amplitude that the receiving channel branch 2 can effectively detect, and the amplitude entering the receiving channel branch 3 is -46dBm. The receiving channel branch 3 contains a linear amplifier circuit (amplification factor is 40dB, saturation output value is 10dBm). At this time, the amplitude of the microwave signal sent to the linear detector of branch 3 is -6dBm, which is within the amplitude that the detector can effectively detect.

[0043] The receiving channel module of the present invention has only one antenna interface to the outside. The receiving channel is divided into three receiving channel branches through branching devices such as -30dB couplers and -10dB couplers. The three receiving channel branches share one receiving antenna. The three receiving channels after division can process the electromagnetic field of their corresponding measurement intervals respectively. The output value of the linear detector in each receiving channel branch is judged as valid data only within the linear detection range. If it is saturated or the output is zero, it is considered that the data output by the receiving channel branch is invalid.

[0044] At a distance of 500m from the radar (far field), receiving channel branch 1 is used to measure the microwave amplitude of the antenna main lobe beam. The amplitude range that can be measured is [10dBm / m 2 ,40dBm / m 2 ]; receiving channel branch 2 is used to measure the antenna sidelobe microwave amplitude, and its measurable amplitude range is [-20dBm / m 2 ,10dBm / m 2 ]; receiving channel branch 3 is used to measure the antenna sidelobe microwave amplitude, and its measurable amplitude range is [-50dBm / m 2 ,-20dBm / m 2], so that the measurement range of the measuring equipment completely covers the antenna transmission lobe of this type of radar. The three measurement ranges are divided, and attention should be paid to the coverage of the critical points to prevent the measurement values ​​from being missed. The integrity of the measurement range is ensured by expanding the receiving channel branches and allowing a small range of measurement overlap at the three measurement critical points. The specific adjustment needs to be fine-tuned according to the specific plan.

[0045] The measurement results are sent to the AD sampling interface of the microprocessor for AD sampling. After comprehensive processing of the data sampled from each AD port, the final measurement results and the latitude, longitude, altitude, time and other information of the equipment are generated into a batch file and stored in the FLASH chip. The receiving channel is a large dynamic receiving and processing channel. When testing the antenna transmission lobe and space magnetic field of the radar and other radiation sources, the main lobe and side lobe signals of the radar can adaptively measure the magnetic field strength of the current beam and output the correct measurement results.

[0046] The beneficial effects of the present invention are as follows: using a drone, electromagnetic wave measuring equipment can easily measure the emission lobe of a radar in the far field, and draw the radar emission lobe according to the test results; at the same time, the electromagnetic field intensity of the space of interest can be measured; using this equipment to test the emission lobe of a radar or other equipment greatly reduces the investment in manpower and material resources, and the test of the lobe data is also more complete.

Claims

1. A method for measuring the electromagnetic field strength in space, characterized in that: The following steps are involved: Step 1. Determine the operating frequency band of the measuring device; Step 2. Divide the antenna signal into multiple paths after it enters the receiving channel, at least into 3 paths; Step 3. First, coupler 1 is used to divide the receiving channel into branch 1 (coupling branch) and a straight-through branch; Step 4. The through branch is divided into branch 2 and branch 3 through coupler 2, and the measurement range of branch 2 and the through branch remains unchanged; Step 5. Add an amplifier circuit to branch 3 to increase the measurement range; Step 6. After the microwave signals of the three receiving branches pass through the linear detector, the detection signals are sent to the AD sampling interface of the microprocessor, and the detection voltage is quantized under the action of the high-stability sampling clock; when the microwave signal strength entering the antenna is [10dBm, 40dBm], only the receiving branch 1 can detect and output normally, and the branches 2 and 3 are both in a saturated state; when the microwave signal strength entering the antenna is [-20dBm, 10dBm], only the receiving branch 2 can detect and output normally, the detection output of branch 1 is 0 due to the low amplitude of the microwave signal, and branch 3 is in a saturated state; when the microwave signal strength entering the antenna is [-50dBm, -20dBm], only the receiving branch 3 can detect and output normally, and the detection output of the through branch 1 and branch 2 is 0 due to the low amplitude of the microwave signal; Step 7. By detecting the output values ​​of the three receiving channels, the real-time amplitude of the microwave signal entering from the antenna is obtained.

2. The method for measuring the electromagnetic field strength in space according to claim 1, characterized in that: The amplitude measurement at the two breakpoints in step 7 is: take the average value of the two segment amplitudes.

3. The method for measuring the electromagnetic field strength in space according to claim 1, characterized in that: The method also includes step eight, wherein the measuring device is installed and fixed on the UAV, and the measuring device reads the latitude and longitude coordinates, altitude and time scale information of the UAV.

4. The method for measuring the spatial electromagnetic field strength according to claim 3, characterized in that: It also includes step nine, sending the longitude and latitude coordinates, altitude or time scale information of the high-precision Beidou module to the microprocessor of the measuring device, and the microprocessor outputs the measured time microwave amplitude signal and the signal output by the high-precision Beidou module at a specified data rate. The output batch data includes: longitude and latitude coordinates, altitude, time scale, and signal amplitude.

5. The method for measuring the spatial electromagnetic field strength according to claim 4, characterized in that: The method also includes step 10. The microprocessor stores the generated data into FLASH according to a certain data length and time relationship.

6. The method for measuring the spatial electromagnetic field strength according to claim 1, characterized in that: The measuring device comprises an analog unit and a digital unit. The analog unit comprises an omnidirectional receiving antenna and a receiving channel. The receiving channel comprises at least three receiving channel branches. The output of the omnidirectional receiving antenna is connected to a receiving channel coupler. One output of the receiving channel coupler is connected to a first limiter. The output of the first limiter is connected to a first band-pass filter. The output of the first band-pass filter is connected to a first detector. The output of the first detector is connected to an AD port 1 processed by the digital unit. Another output of the receiving channel coupler is connected to a power divider. One output of the power divider is connected to a second limiter. The output of the second limiter is connected to a second band-pass filter. The output of the second band-pass filter is connected to a second detector. The output of the second detector is connected to an AD port 2 processed by the digital unit. Another output of the power divider is connected to a third limiter. The output of the third limiter is connected to a low-noise amplifier. The output of the low-noise amplifier is connected to a third band-pass filter. The output of the third band-pass filter is connected to the first amplifier. The output of the first amplifier is connected to a matching attenuator. The output of the matching attenuator is connected to the second amplifier. The output of the second amplifier is connected to a third detector. The output of the third detector is connected to an AD port 3 processed by the digital unit.

7. The method for measuring the spatial electromagnetic field strength according to claim 1, characterized in that: The digital unit consists of a microprocessor, a high-stable crystal oscillator, a high-precision Beidou positioning module, FLASH and a communication interface; the microprocessor samples the AD port; the high-stable crystal oscillator provides a stable sampling clock for the microprocessor; the high-precision Beidou positioning module transmits the spatial coordinate information and time stamp information of the equipment to the microprocessor in real time; the FLASH stores the real-time data generated by the microprocessor; the communication interface is used to read and erase the data in the FLASH.

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