Passive chaff interference testing device and method based on vector network analyzer

Abstract

The invention discloses a passive chaff interference testing device and method based on a vector network analyzer. The passive chaff interference testing device comprises a radar transmitting antenna installed on an antenna platform and a radar receiving antenna installed on the antenna platform. And a radar absorbing material located between the transmitting antenna and the receiving antenna for attenuating linear transmission of signals from the transmitting antenna to the receiving antenna, a low power transmitter for implementing a safe ground test connected to the transmitting antenna for radar radio frequency signals generated by chaff scattering units dispersed above the platform, meanwhile, a network analyzer is connected to a receiving antenna, and the network analyzer can measure low-power radio frequency signals reflected by the decentralized countermeasure unit; according to the invention, the medium-range ground test of the chaff confrontation unit can be carried out, including radar reflection cross section measurement. This test makes it possible to manufacture a higher quality unit and send it to an operator counter to the unit with greater convenience, safety, and lower test costs.

Description

Technical Field

[0001] The present invention relates to the field of radar testing, and in particular to a passive chaff interference testing device and method based on a vector network analyzer. Background Art

[0002] In the field of electronic countermeasures, it is necessary to ensure the performance consistency of equipment units. To ensure that the countermeasures manufactured throughout the production process do not change, and thus ensure their performance consistency, we conduct a test called Lot Acceptance Testing (LAT). The working principle of the Lot Acceptance Testing is to first test a large number of "good" units, and then use the obtained data to set a benchmark for the units produced subsequently. The benchmark used for the Lot Acceptance Testing should be directly related to the key factors that make the electronic countermeasures effective.

[0003] It should be further noted that the Lot Acceptance Testing is not testing whether a single countermeasure is effective, but only determining whether the unit is similar to the previously considered "good" units by using the previously established benchmark. Therefore, the Lot Acceptance Testing focuses on the repeatability between individual tests so that any differences can be fully attributed to the production quality.

[0004] Radar countermeasures, such as chaff, can generate a large number of small-scale clouds of metal-coated glass fibers. The metal coating enables the fibers to act as dipoles that can reflect radar. When the reflectivity is combined with extensive dispersion, a large radar cross-section is produced. For example, a large radar cross-section can prevent an enemy radio frequency seeker from locking onto the user's aircraft.

[0005] Currently, radar countermeasures such as chaff units are mainly tested in two ways. The first test is a simple functional test. The second test measures the size of the sleeve, the length of the fiber, and the appearance of the markings. Although these tests are necessary, neither of them directly checks the radar cross-section (RCS), which is one of the key factors determining the effectiveness of the countermeasure unit. To ensure test effectiveness, countermeasure units such as chaff are operated on an aircraft while monitoring the guidance threat to see if they lift the lock on the aircraft. This test method is extremely costly and time-consuming. In addition, the regulations related to operating the aircraft, operating and maintaining the threat, and the limited number of units that can be distributed per flight (for example, 30 units) further increase the complexity of the flight test. In addition, since the chaff is released from a moving platform, the distance between the release point and the measuring device changes every time the test is run. Although this effect can be measured, it must be considered after each test. In addition, during the entire test process, the wind factor and turbulence may vary greatly, which will affect the way the chaff is dispersed. Summary of the Invention

[0006] The object of the present invention is to provide a passive chaff interference test device and method based on a vector network analyzer, which can perform mid-range ground tests on countermeasure units such as chaff, including measuring the radar cross section. Such tests enable the manufacture of higher-quality units and their delivery to countermeasure unit operators with greater convenience, safety, and lower test costs.

[0007] A passive chaff interference RCS test device based on a vector network analyzer provided by the present invention, an antenna platform mounted on a ground support member, and at least one first radar transmitting antenna is arranged on the antenna platform; At least one first radar receiving antenna is arranged on the antenna platform, and the first radar receiving antenna is configured to transmit at a Ka-band frequency or an X-band frequency; The radar absorbing material arranged on the antenna platform, the radar absorbing material is linearly located between the first radar transmitting antenna and the first radar receiving antenna, and is used to attenuate the linear transmission of the signal between the radar transmitting antenna and the radar receiving antenna; The first low-power transmitter is communicatively connected to the radar transmitting antenna and is configured to generate a radio frequency signal in a predetermined frequency band for the radar transmitting antenna to transmit; The first network analyzer is communicatively connected to the radar receiving antenna and is configured to determine the received power of the transmitted radio frequency signal reflected by the countermeasure unit dispersed above the antenna platform; The countermeasure dispersion mechanism disperses the countermeasure unit into a volume at a certain distance above the antenna platform.

[0008] Further, the low-power transmitter is configured to operate in the range of 20 - 21 dBmw.

[0009] Further, the radar absorbing material includes one or more of foam absorbents, polyurethane foams, Holland shields, rubber foams, ferrite materials, semiconductors, graphite, carbon nanotubes, iron ball coatings, or carbon nanotube-based coatings, wherein the polyurethane foam is carbon loaded with conductive carbon black and / or crystalline graphite particles, and the rubber foam is impregnated with carbon and iron.

[0010] Further, the countermeasure dispersion mechanism is within a range of 4.5 - 15 M above the antenna platform, and the countermeasure dispersion mechanism includes an air flow unit configured to control the air flow passing through the countermeasure unit during the test to achieve uniform dispersion.

[0011] Further, at least one second radar transmitting antenna and a second radar receiving antenna are provided on the antenna platform; the second low-power transmitter is communicatively connected to the second radar transmitting antenna and is configured to generate a second radio frequency signal in a second frequency band for transmission with the second radar transmitting antenna; the second network analyzer is communicatively connected to the second radar receiving antenna and is configured to determine the received power of the second radio frequency signal reflected from the countermeasure units scattered above the antenna platform; the radar absorbing material is linearly located between the second radar transmitting antenna and the second radar receiving antenna.

[0012] A test method for a passive chaff interference RCS test device based on a vector network analyzer, characterized in that: at least one radar transmitting antenna and at least one radar receiving antenna, both of which are connected to the transmitting and receiving mechanisms, emit continuous wave or pulsed electromagnetic radiation towards a certain 3D target through the radar transmitting antenna, and then receive the reflected electromagnetic radiation pulses through the radar receiving antenna; then measure the returned pulses at the site to determine the characteristics of the object. The frequency of the emitted electromagnetic radiation depends on the desired target, and the ratio between the transmitted signal and the returned signal is used to calculate the two-dimensional (2D) projected area of the 3D target measured by the radar wave. This ratio represents the radar cross section of the object. Formula 1 shows the method for calculating the radar cross section RCS (σc) of a sphere; (1) Wherein, "R" is the distance to the target; "Sr" and "St" are the received power and the transmitted power respectively, "Gt" and "Gr" are the gains of the transmitting antenna and the receiving antenna respectively, and "λ" is the wavelength of the used radiation signal.

[0013] The beneficial effects are as follows: It can perform mid-range ground tests on countermeasure units such as chaff, including measuring the radar cross section. Such tests enable the manufacture of higher-quality units and their delivery to the operators of countermeasure units with greater convenience, safety, and lower test costs; the parts not detailed in the present invention are common existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below with reference to the accompanying drawings: Figure 1 Shows a schematic diagram of an exemplary radar system according to certain aspects;

[0015] Figure 2 Shows a schematic diagram of a currently disclosed measuring device or setup according to certain aspects;

[0016] Figure 3 Shows an acceptance criteria chart for countermeasure unit tests according to certain aspects;

[0017] Figure 4Disclosed is a method flowchart for testing the radar cross section of an anti-countermeasure device using Figure 2 a device. Detailed implementation manners

[0018] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0019] As Figure 1 shown, a passive chaff interference RCS test device based on a vector network analyzer includes at least one first radar transmitting antenna 3 and at least one first radar receiving antenna 4, both of which are connected to a transmitting / receiving station or device; electromagnetic radiation in the form of continuous waves or pulses is transmitted to an anti-countermeasure unit 8 through the first transmitting antenna 3, and then the electromagnetic radiation pulses reflected back are received through the first receiving antenna 4; Then the returned pulses are measured at the station to determine the characteristics of the anti-countermeasure unit 8. The frequency of the transmitted radiation depends on the target required. The ratio between the transmitted signal and the returned signal is used to calculate the two-dimensional (2D) projected area of the anti-countermeasure unit 8 measured by the radar wave. This ratio represents the radar cross section of the object. Equation 1 shows the method for calculating the radar cross section RCS; (1) where "R" is the distance to the target; "Sr" and "St" are the received power and the transmitted power respectively, "Gt" and "Gr" are the gains of the transmitting antenna and the receiving antenna respectively, and "λ" is the wavelength of the radiation signal used. Embodiment

[0020] Different from infrared countermeasures, radar chaff is passive, which means it does not actively transmit interference signals. Instead, chaff is designed to reflect radar signals. Therefore, a radar energy source pointing to the chaff is required to measure the radar cross section of the chaff. Although it is envisioned that the radar source can use any frequency, considering the application of chaff in certain frequency bands, in order to optimally test the chaff, at least two radar frequency bands may be implemented: the X band of 8-12 GHz and the Ka band of 26.5-40 GHz.

[0021] As Figure 2A passive chaff interference RCS test device based on a vector network analyzer is shown, including an antenna platform 2. The antenna platform 2 is installed on a support member 1 on the ground. The support member 1 raises the antenna platform 2 to a certain distance above the ground. In some aspects, the distance above the ground ranges from 0.3 meters to 1.8 meters, but the present invention is not limited thereto. The antenna platform 2 itself includes a bottom support frame or member, such as a tripod, on which one or more antenna brackets are installed. The antenna brackets are in turn used to install one or more first transmitting antennas 3 and second transmitting antennas 3.1, and one or more first receiving antennas 4 and second receiving antennas 4.1. In the shown example, two pairs of transmitting / receiving antennas are shown, and each pair of antennas operates at different frequencies to provide measurements using two different radar frequency bands;

[0022] The antenna platform 2 further includes radar absorbing material 5. The radar absorbing material 5 is located or arranged between the first transmitting antenna 3, second transmitting antenna 3.1 and the first receiving antenna 4, second receiving antenna 4.1 on the antenna platform 2 for attenuating the direct or linear signal transmission between the transmitting antenna and the receiving antenna; As shown in the figure, the radar absorbing material 5 is linearly arranged between the transmitting antenna and the receiving antenna along a direction parallel to the top surface of the support frame 5 to attenuate or impede the linear transmission of radio frequency signals directly from the transmitting antenna to the receiving antenna, so that all or at least most of the radio frequency signals received by the first receiving antenna 4, second receiving antenna 4.1 will be those signals transmitted from the first transmitting antenna 3, second transmitting antenna 3.1. These signals are reflected from the countermeasure unit 8 during the test in a volume scattered in a certain optimal height range above the antenna platform 2; In addition, the height of the radar absorbing material 5 above the antenna platform 2 is configured to ensure sufficient attenuation of radio frequency signals and little or no spillover of direct radio frequency signal transmission between the transmitting antenna and the receiving antenna. The radar absorbing material 5 can be composed of various materials, including but not limited to foam absorbing materials, such as polyurethane foam, which is carbon-loaded with conductive carbon black and / or crystalline graphite particles, rubber foam impregnated with carbon and iron, ferrite materials, semiconductors, graphite, carbon nanotubes, iron ball coatings, that is, microspheres coated with carbonyl iron or ferrite, or carbon nanotube-based coatings; In addition, although Figure 2 the geometric shape of the radar absorbing material 5 shown in the figure is shown in a block form, the geometric shape of the radar absorbing material 5 can be configured according to any geometric shape to provide optimal or maximum radar attenuation.

[0023] including one or more low-power transmitters configured to generate radar signals at a specific frequency or wavelength and then transmit these signals through the first transmitting antenna 3 or the second transmitting antenna 3.1; In Figure 2In the example, the first low-power transmitter 6 is configured to generate a signal in the X-band of 8 - 12 GHz, and the second low-power transmitter 6.1 is configured to generate a signal in the Ka-band of 26.5 - 40 GHz. The first low-power transmitter 6 and the second low-power transmitter 6.1 are communicatively connected to their respective first transmitting antenna 3 or second transmitting antenna 3.1 through power output cables to transmit and drive the signals emitted by the antennas. The lengths of the power output cables are set to allow a safe operating distance to be maintained between the first transmitting antenna 3 or second transmitting antenna 3.1 and the personnel operating the system at the first low-power transmitter 6 and the second low-power transmitter 6.1.

[0024] including one or more network analyzers configured to receive the reflected radar signals received by the first receiving antenna 4 and the second receiving antenna 4.1 to determine the radar cross-section of the countermeasure unit 8. Figure 2 In the example, the first network analyzer 7 is configured to receive and analyze the X-band signal received by the first receiving antenna 4, and the second signal or network analyzer 7.1 is configured to receive and analyze the Ka-band signal received by the second receiving antenna 4.1. The first network analyzer 7 and the second network analyzer 7.1 are communicatively connected to the first receiving antenna 4 and the second receiving antenna 4.1 through power receiving cables, and the lengths of these cables are set to allow a safe operating distance to be maintained between the first receiving antenna 4, the second receiving antenna 4.1 and the personnel operating the system at the first network analyzer 7 and the second network analyzer 7.1.

[0025] The countermeasure dispersion mechanism is configured to release and disperse the countermeasure unit 8 into the volume of space above the antenna platform 2, as shown by the countermeasure unit cloud 8 in Figure 2 ; in one example, the countermeasure dispersion mechanism may include using a wind flow facility that allows a controlled airflow of the countermeasure unit during testing to achieve consistent dispersion. By fixing the positions of the countermeasure dispersion mechanism and the antenna platform 2 during testing, changes in the measurement distance are eliminated. Although there is more background noise in this arrangement than in clean air, by releasing the countermeasure unit in the same area, the background noise can be reduced by zeroing it each time before launching or dispersing the countermeasure unit. Although testing the countermeasure unit in the wind flow facility does not simulate an aircraft, this is not necessary for batch acceptance testing; this is because repeatability between tests is the main goal of batch acceptance testing. Then, a baseline is constructed from tests of "good" units known under the same conditions as the later units. In some aspects, the distance of the countermeasure unit 8 above the antenna platform 2 may be in the range of approximately 4.5 meters - 7.5 meters above the platform, but the present disclosure is not necessarily limited to this.

[0026] Using Figure 2A passive chaff interference RCS test device based on a vector network analyzer as shown determines the radar cross section. First, it should be noted that the above Equation 1 is rearranged to solve for the return power Sr, resulting in the following Equation 2: (2) Equation 2 can be used to model the device settings to determine which device pairings can achieve the best cooperation. The equation mainly focuses on the relationship between the return power and the transmit power.

[0027] Table 1 below illustrates: at 9.3 GHz, for a one-square-meter radar cross section target within 15 meters, and moderately focused transmit and receive antennas with an omnidirectional antenna power gain of 22.1, the specific situation of the returned signal power as the transmit power changes.

[0028] Table 1 Transmitted Power [dBm] Transmitted Power [mW] Returned Power [mW] Returned Power [dBm] 0 1 3.64E-09 -83.2 5 3.16 1.15E-08 -78.2 10 10 3.64E-08 -73.2 15 31.62 1.15E-07 -68.2 20 100 3.64E-07 -63.2 From the data in Table 1 above, it can be inferred that when testing the countermeasure device unit, if the returned power is significantly less than the transmitted power, it will result in a large loss. This means that a low-power transmitter needs to drive the transmission at a certain minimum power level or higher than a certain minimum power level, and the network analyzer needs to be sensitive enough to measure the returned signal; in one example, a low-power transmitter capable of providing a peak power of 21 dBmW at 9.3 GHz is used. Given the same settings as in Table 1, this low-power transmitter allows a return of approximately -62 dBm. In the Ka band, the same low-power transmitter with an antenna gain of 20 dBi can output 20 dBm at 35 GHz and can achieve an echo of -75 dBm; due to non-ideal conditions, the expected returned signal will be less than those calculated in Table 1; this means that most basic power sensors on the market will not be able to detect the returned signal from the noise; therefore, for example, when performing radar cross section measurements at 15 meters, network analyzers such as the first network analyzer 7 and the second network analyzer 7.1 are utilized to be able to measure lower power signals; however, the present invention is not limited thereto, and any equivalent device capable of measuring low-power signals can be used. In a further aspect, the first network analyzer 7 and the second network analyzer 7.1 may be configured to calculate and / or determine the radar cross section of the countermeasure device unit from the measured signals, for example, by implementing the above equations (1) and / or (2).

[0029] Figure 3 A chart is shown, showing the acceptance criteria for testing the countermeasure device unit; curve 302 shows the lower limit or envelope threshold, and curve 304 shows the data obtained from testing the actual unit, indicating that it meets the minimum set criteria for passing the unit.

[0030] Although the tests are designed for the X and Ka bands, measurements can be made at any desired wavelength by using appropriate antennas, low-power transmitters, and network analyzers. The present invention provides commercial value to any company wishing to manufacture products or materials with specific radar characteristics and provides a low-cost means of testing products in a limited space. Companies manufacturing radio frequencies will benefit from in-house testing using this system for quality control.

[0031] As described above, this is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A passive chaff interference test device based on a vector network analyzer, characterized in that: An antenna platform 2 mounted on a support structure 1 on the ground, at least one first radar transmitting antenna 3 disposed on the antenna platform; at least one first radar receiving antenna 4 disposed on the antenna platform, the first radar receiving antenna 4 being configured to transmit in a Ka-band frequency or an X-band frequency; A radar absorbing material 5 is arranged on the antenna platform, wherein the radar absorbing material 5 is linearly located between the first radar transmitting antenna 3 and the first radar receiving antenna 4, and is used to attenuate the linear transmission of the signal from the radar transmitting antenna to the radar receiving antenna; The first low-power transmitter 6 is communicatively connected to the first radar transmitting antenna 3 and is configured to generate a radio frequency signal in a predetermined frequency band for transmission by the radar transmitting antenna; The first network analyzer 7 is communicatively connected to the first radar receiving antenna 4 and is configured to determine the received power of the transmitted radio frequency signal reflected from the countermeasure units dispersed above the antenna platform 2; The countermeasure dispersing mechanism disperses the countermeasure units into a volume at a certain distance above the antenna platform 2 .

2. A passive chaff interference test device based on a vector network analyzer according to claim 1, characterized in that: The radar absorbing material 5 includes one or more of foam absorbent, polyurethane foam, Holland shield, rubber foam, ferrite material, semiconductor, graphite, carbon nanotube, iron ball coating or carbon nanotube-based coating, wherein the polyurethane foam is carbon loaded with conductive carbon black and / or crystalline graphite particles, and the rubber foam is impregnated with carbon and iron.

3. A passive chaff interference testing device and method based on a vector network analyzer according to claim 1, characterized in that: The distance between the countermeasure dispersion mechanism and the antenna platform 2 is within the range of 4.5-15M. The countermeasure dispersion mechanism includes a wind flow unit configured to control the airflow passing through the countermeasure unit during the test to achieve uniform dispersion.

4. A passive chaff interference test device based on a vector network analyzer according to claim 1, characterized in that: The antenna platform 2 is provided with at least one second radar transmitting antenna 3.1 and a second radar receiving antenna 4.1; a second low-power transmitter 6.1 is communicatively connected to the second radar transmitting antenna and configured to generate a second radio frequency signal of a second frequency band for transmission with the second radar transmitting antenna; a second network analyzer 7.1 in communication with the second radar receiving antenna 4.1 and configured to determine a received power of a second radio frequency signal reflected from a countermeasure unit dispersed above the antenna platform 2; The radar absorbing material 5 is linearly located between the second radar transmitting antenna 3.1 and the second radar receiving antenna 4.

1.

5. The passive chaff interference test device based on a vector network analyzer according to claim 1, characterized in that: The first low power transmitter 6 and the second low power transmitter 6.1 are configured to operate in the range of 20-21 dBmw.

6. A test method for a passive chaff interference test device based on a vector network analyzer as described in claim 1, characterized in that: At least one first radar transmitting antenna 3 and at least one first radar receiving antenna 4, the first radar transmitting antenna 3 and the first radar receiving antenna 4 are both connected to the transmitting and receiving mechanism, and the first radar transmitting antenna 3 transmits continuous wave or pulse electromagnetic radiation to the countermeasure unit 8, and then the first radar receiving antenna 4 receives the reflected electromagnetic radiation pulse; then the returned pulse is measured at the site to determine the characteristics of the object, the frequency of the emitted electromagnetic radiation depends on the desired target, and the ratio between the transmitted signal and the returned signal is used to calculate the two-dimensional projection area of ​​the countermeasure unit 8 measured by the radar wave, and this ratio represents the radar reflection cross section of the object. Formula 1 shows the method for calculating the radar reflection cross section RCS of a sphere; (1) Where "R" is the distance to the target; "Sr" and "St" are the return power and the transmitted power respectively, "Gt" and "Gr" are the gains of the transmitting antenna and the receiving antenna respectively, and "λ" is the wavelength of the radiated signal used.

Images