A method for resisting transmission and reception blocking in full-range of Doppler radar

Abstract

The present invention relates to a Doppler radar full-range anti-transmission and reception blocking method, comprising: in a normal speed measurement mode of the Doppler radar, obtaining the working altitude data and attitude data of the Doppler radar, wherein the working altitude data is the relative altitude of the working position of the Doppler radar relative to the ground or sea surface; stratifying the full altitude of the Doppler radar, and judging the altitude stratification of the Doppler radar according to the working altitude data; determining the repetition frequency of the Doppler radar according to the altitude stratification and attitude data; the Doppler radar irradiates the ground according to the repetition frequency to eliminate the "altitude dead zone" and altitude scale error of the Doppler radar. The Doppler radar full-range anti-transmission and reception blocking method provided by the present invention ensures the altitude measurement accuracy and altitude measurement range of the Doppler radar during the flight of an aircraft.

Description

Technical Field

[0001] The invention relates to the technical field of Doppler radars, and in particular to a full-range anti-transmission and reception blocking method for Doppler radars. Background Art

[0002] During the operation of the Doppler radar, the three-axis velocity in the carrier coordinate system is obtained for use by measuring the Doppler center frequency of 3 or 4 different directional beam echoes.

[0003] In a pulse Doppler radar with a common antenna for both transmission and reception, when the transmitter is working, the blocking pulse will synchronously block the receiver. When the aircraft flies at a higher altitude, due to the high repetition frequency, the time for the signal to propagate from the aircraft to the ground and back will be much longer than the pulse period. Since the receiver is periodically blocked, when the aircraft flies at many altitude levels, the radar stops working because it cannot receive the echo signal. This is the pulse blocking phenomenon caused by the blocking of transmission and reception. Generally, the altitude level where these phenomena occur is called the altitude dead zone.

[0004] When the aircraft flies at the edge of the dead zone, part of the echo signal cannot pass through the receiver because the receiver is blocked, which narrows the pulse signal width received by the radar and reduces the power of the useful signal received, thereby reducing the signal-to-noise ratio. At the same time, when the aircraft flies at the edge of the dead zone, due to the different slant distances from each reflection unit to the antenna in the beam irradiation area, the signals reflected by each reflection unit do not reach the input end of the receiver at the same time, so the distribution of the spectrum of the Doppler signal received by the radar is distorted, which brings errors to the measurement of the Doppler frequency. This error is called the altitude scale error.

[0005] In order to overcome the altitude dead zone and altitude scale error, the prior art usually adopts the following two measures: First, a noise generator is set in the transmitter, and the low-frequency noise generated by it is added to the pulse generator, so that the repetition frequency of the radar changes according to a random law. When the aircraft flies at a certain altitude, although some repetition frequencies are in the altitude dead zone and the radar cannot receive the echo signal, there are other repetition frequencies and the radar can receive the echo signal. The second is to use a fan-shaped beam, by widening the beam width, increasing the duration of the echo pulse signal received in the entire beam, and reducing the impact of the altitude dead zone. Although the above method can reduce the impact of the altitude dead zone, it is difficult to design and implement. Summary of the invention

[0006] In view of the above analysis, an embodiment of the present invention aims to provide a Doppler radar full-range anti-transmission and reception blocking method to solve the problem that the prior art overcomes the high dead zone and high scale error design and implementation difficulties.

[0007] The technical solution provided by the present invention is:

[0008] The present invention discloses a Doppler radar full-range anti-transmission and reception blocking method, comprising the following steps:

[0009] In a normal speed measurement mode of the Doppler radar, obtaining working height data and attitude data of the Doppler radar, wherein the working height data is a relative height of the working position of the Doppler radar relative to the ground or sea surface;

[0010] The full altitude of the Doppler radar is layered, and the altitude layer of the Doppler radar is determined according to the working altitude data;

[0011] Determine the repetition frequency of the Doppler radar based on the altitude layer and attitude data;

[0012] The Doppler radar irradiates the ground according to the repetition frequency to eliminate the "altitude dead zone" and altitude scale error of the Doppler radar.

[0013] Further, the full altitude stratification divides the altitude of the Doppler radar into a low altitude layer, a medium altitude layer and a high altitude layer;

[0014] The lower limit of the middle altitude layer h1≥m·τ·c, where τ is the delay and transition time of the RF switch, c is the speed of light, and m is a preset integer; the height below the lower limit of the middle altitude layer is the low altitude layer;

[0015] The upper limit setting range of the middle-altitude layer is 1000-1500m; the height above the upper limit of the middle-altitude layer is the high-altitude layer.

[0016] Furthermore, the altitude layer is a low altitude layer, and the repetition frequency of the Doppler radar is a group of high repetition frequencies;

[0017] The altitude layer is a middle altitude layer, and the repetition frequency of the Doppler radar is set according to the altitude value provided by the airborne altitude measuring device;

[0018] The altitude layer is a high altitude layer, and the repetition frequency of the Doppler radar is a group of low repetition frequencies.

[0019] Furthermore, when at a low altitude layer or a high altitude layer, the determination of the Doppler radar repetition frequency includes:

[0020] 1) In the corresponding altitude layer, divide the Doppler radar beam illumination time into N segments;

[0021] 2) selecting a corresponding height value for each of the N segments, and determining a set of beam slant ranges in combination with the attitude data;

[0022] 3) According to the formula Calculate a set of repetition frequencies corresponding to the set of beam slant distances; where f r is the repetition frequency, R is the beam slant distance; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f i ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar;

[0023] 4) According to the group repetition frequency, radar signals are sent and received in sequence, and the echo signals corresponding to the group repetition frequency are counted to see whether they are within the preset gate range. If they are not within the preset gate range, the process returns to step 2) to reselect the height value and adjust the group repetition frequency until the echo signals are within the preset gate range.

[0024] 5) The adjusted repetition frequency group is used as the repetition frequency of the Doppler radar within the altitude range.

[0025] Further, the counting of whether the echo signal corresponding to the group of repetition frequencies is within a preset gate range includes:

[0026] Signals are sent and received according to each repetition frequency in the group. When the echo falls within the receiving wave gate, it is marked as 1, otherwise, it is marked as 0, and the number num of echoes falling within the receiving wave gate is obtained;

[0027] Whether the echo signal corresponding to the group of repetition frequencies is within the preset gate range is determined according to the following preset conditions: if num is greater than N / 3, it is determined that the echo signal corresponding to the group of repetition frequencies is within the preset gate range and the repetition frequency is appropriately selected; otherwise, it is determined that the echo signal corresponding to the group of repetition frequencies is not within the preset gate range.

[0028] Furthermore, when at the mid-altitude layer, the determination of the Doppler radar repetition frequency includes:

[0029] Determine the beam slant range R based on the working height data and attitude data measured in real time;

[0030] Calculating Doppler Radar Repetition Frequency In the formula, f r is the repetition frequency; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f ri ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar.

[0031] Furthermore, the Doppler radar includes four X-shaped radar beams that are centrally symmetrical; when the vehicle of the Doppler radar is flying level, the slant ranges of the four radar beams are R1=R2=R3=R4=H / sinβ, β is the angle between the center line of the radar beam and the ground projection, and H is the working altitude of the Doppler radar.

[0032] Furthermore, the Doppler radar includes four X-shaped radar beams that are centrally symmetrical; when the vehicle of the Doppler radar is maneuvering, the slant ranges of the four radar beams are respectively:

[0033] R1=H / sinβ′1=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ;

[0034] R2=H / sinβ′2=H / (cosα·sinγ·cosv c ·cosγ c -cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ;

[0035] R3=H / sinβ′3=H / (cosα·sinγ·cosv c ·cosγ c -cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ;

[0036] R4=H / sinβ′4=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ;

[0037] Where H is the operating altitude of the Doppler radar; β′1, β′2, β′3, and β′4 are the angles between the center lines of beams 1 to 4 and their projections on the ground; v c is the pitch angle of the vehicle, γ c is the rolling angle of the vehicle, γ is the angle between the center line of the entire beam and the X-axis of the vehicle body coordinate system; α is the angle between the projection of the center line of the entire beam on the plane where the center lines of beams 1 and 2 are located and the X-axis.

[0038] Furthermore, the pulse duty cycle coefficient Δ of the output signal of the Doppler radar is the ratio of the output signal pulse width T to the pulse repetition period T r The ratio of , Δ is between 0.3 and 0.5.

[0039] Furthermore, in the normal speed measurement mode of the Doppler radar, obtaining the working altitude data and attitude data of the Doppler radar includes:

[0040] After the airborne Doppler radar is powered on, a self-test is performed to determine whether its hardware functions are normal; if not, the corresponding hardware is corrected until the functions are normal;

[0041] After receiving the speed measurement command from the operator, the Doppler radar works in the normal speed measurement mode;

[0042] The real-time working altitude data of the Doppler radar is obtained through the vehicle's radio altimeter or laser altimeter, and the attitude data of the Doppler radar is obtained through the vehicle's inertial navigation device.

[0043] The present invention can achieve at least the following beneficial effects:

[0044] The Doppler radar full-range anti-transmission and reception blocking method provided by the present invention solves the problem of "altitude dead zone" of the Doppler radar by setting the repetition frequency in sections according to the relative altitude and controlling the repetition frequency by the relative altitude, thereby ensuring the altitude measurement accuracy and altitude measurement range of the Doppler radar during the flight of the aircraft.

[0045] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0047] Figure 1 is a schematic diagram of antenna beam configuration in an embodiment of the present invention;

[0048] Figure 2 Schematic diagram of a top view of a four-beam antenna with integrated transceiver in an embodiment of the present invention;

[0049] Figure 3 The figure is a flow chart of the method for resisting the whole-process transmission and reception blocking of the Doppler radar in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0051] The working principle of Doppler radar is based on the Doppler effect. The transmitting antenna of the radar radiates continuous waves to the ground. Since the antenna beam has a certain width, the echo returned from the ground has a certain spectrum width. Due to the Doppler effect, the center frequency has an offset relative to the transmitting frequency. The offset f d It is proportional to the projection of the velocity in the direction of signal radiation, see the following formula:

[0052]

[0053] Where: V is the ground velocity vector; λ is the wavelength of the transmitted signal; γ is the angle between the beam centerline and the ground velocity vector.

[0054] Doppler radar will always have a drift angle under the influence of wind, and there will also be vertical velocity. Only one beam cannot accurately measure the velocity vector of the radar in three-dimensional space. Therefore, the Doppler radar antenna adopts a symmetrical system with four radar beams in a centrally symmetrical X shape, which radiate electromagnetic wave beams in four different directions in turn. The specific working diagram is shown in the figure below. Figure 1 shown.

[0055] Figure 1 The coordinate system shown in is the carrier coordinate system, the γ0 angle is the fixed angle between the antenna beam and the longitudinal axis of the aircraft, and the δ0 angle is the angle between the antenna beam and the longitudinal axis of the aircraft. y OV z Projection on the surface and V y The fixed angle between the two axes, β is the angle between the center line of the radar beam and the ground projection, v c is the pitch angle of the vehicle, γ c is the rolling angle of the vehicle, β′1, β′2, β′3, β′4 are the angles between the center lines of beams 1 to 4 and the projections on the ground respectively; γ is the angle between the center line of the entire beam and the X-axis of the vehicle body coordinate system; α is the angle between the projection of the center line of the entire beam on the plane where the center lines of beams 1 and 2 are located and the X-axis, is the angle between the beam centerline and the Z axis.

[0056] According to the Doppler effect, there is the following relationship:

[0057]

[0058]

[0059]

[0060]

[0061] Since the system only detects positive frequencies, and the forward velocity is much greater than the lateral and vertical velocities, that is, v x >>v z ,v y The above formula can be transformed into:

[0062]

[0063]

[0064]

[0065]

[0066] Then calculate V x , V y , V z The expression is as follows:

[0067]

[0068]

[0069]

[0070] Therefore, as long as the instantaneous Doppler frequency values ​​of the four beams are measured in real time, the various components of the radar carrier velocity vector (i.e. the longitudinal velocity along the heading, the lateral velocity perpendicular to the heading, and the vertical velocity) can be calculated in real time according to the above formula for navigation.

[0071] In this embodiment, the structural dimensions of the four-beam traveling waveguide antenna that generates four X-shaped radar beams do not exceed 400 mm×200 mm×30 mm, and a co-aperture integrated design of the receiving and transmitting antennas is adopted.

[0072] The transmitting antenna and receiving antenna of the four-beam traveling wave waveguide antenna both have four beams with strictly symmetrical beam pointing angles, ensuring that the precise flight speed of the flying vehicle in three directions can be solved through the relationship between the Doppler frequency shift and the beam pointing angle.

[0073] Specifically, the staggered arrangement of the transmitting and receiving waveguides and their high and low placement solves the problem of antenna transmitting and receiving integration;

[0074] Since the receiving or transmitting antenna uses a traveling wave array with a narrow waveguide slot, there will be a large gap between the radiating waveguides of the transmitting antenna to accommodate the radiating waveguide of the receiving antenna. In this way, the radiating part of the transmitting and receiving antennas is designed in an integrated manner by staggering the radiating waveguides of the transmitting and receiving antennas. At the same time, considering the influence of the feeding network, the radiating waveguides of the transmitting and receiving antennas are arranged in a high and low position in the same plane so that each feeding waveguide can feed the transmitting and receiving antennas separately. The staggered arrangement and high and low position of the radiating waveguides of the transmitting and receiving antennas solves the miniaturization and integration of the transmitting and receiving antennas, so that the beam pointing angles of the transmitting and receiving antennas are in a reference coordinate system, and at the same time solves the problem of staggered feeding of the transmitting and receiving antennas.

[0075] More specifically, Figure 2 As shown, the four-beam traveling wave waveguide antenna is composed of a plurality of radiating waveguides and four feeding waveguides, and each radiating waveguide is a narrow-side slotted waveguide with the same structure;

[0076] The two upper feeding waveguides are responsible for the transmitting antenna, with a total of four ports, generating four beams; the two lower feeding waveguides are responsible for the receiving antenna, with a total of four ports, generating four beams. All eight ports are connected to the waveguide isolator, with port 1 being incident, and ports 2, 3, and 4 being isolators that function as reverse load absorption.

[0077] The number and wavelength of the radiation waveguides of the transmitting antenna and the receiving antenna are determined according to the antenna size and the frequency of the radar;

[0078] The spacing between each slot of the narrow side slotted waveguide is determined according to the X-direction beam pointing angle of the antenna pattern;

[0079] The spacing of the feed waveguide slots is determined based on the Y-direction beam pointing angle of the antenna pattern;

[0080] The inclination angle and penetration depth of each slot of the narrow-edge slotted waveguide are determined according to the amplitude distribution function and coupling function to meet the requirements of the side lobes of the antenna pattern.

[0081] The transmitting and receiving waveguides are arranged in a staggered manner to ensure consistent spacing. The height direction is arranged according to the actual size requirements to ensure that the isolation of the transmitting and receiving antennas is as high as possible.

[0082] A specific embodiment of the present invention discloses a Doppler radar full-range anti-transmission and reception blocking method, such as Figure 3 As shown, the following steps are included:

[0083] Step S1, in a normal speed measurement mode of the Doppler radar, obtaining working height data and attitude data of the Doppler radar, wherein the working height data is a relative height of the working position of the Doppler radar relative to the ground or sea surface;

[0084] Step S2, stratifying the full altitude of the Doppler radar, and determining the altitude stratification of the Doppler radar according to the working altitude data;

[0085] Step S3, determining the repetition frequency of the Doppler radar according to the altitude layer and the attitude data;

[0086] Step S4: The Doppler radar irradiates the ground according to the repetition frequency to eliminate the "altitude dead zone" and altitude scale error of the Doppler radar.

[0087] Specifically, step S1 further includes:

[0088] 1) After the airborne Doppler radar is powered on, it will perform a self-test (enter the normal speed measurement mode of the radar) to determine whether its hardware functions are normal; if not, correct the corresponding hardware until the functions are normal; after the self-test is normal, it will enter the silent state.

[0089] 2) After receiving the speed measurement command issued by the operator, it enters the speed measurement mode, obtains the real-time working altitude data of the Doppler radar through the vehicle's altitude measurement device, and obtains the attitude data of the airborne Doppler radar through the airborne inertial navigation device.

[0090] Among them, the vehicle's altitude measuring device is a radio altimeter or a laser altimeter; the working altitude data obtained by the radio altimeter or the laser altimeter is the relative altitude of the working position of the Doppler radar relative to the ground or sea surface; the repetition frequency is set using the relative altitude provided by the radio altimeter or the laser altimeter, which can not only ensure full-altitude resistance to transceiver blocking, but also ensure the accuracy of speed measurement.

[0091] Preferably, the radar operating altitude data and attitude data are obtained through a communication interface such as a 1553B bus or RS-422.

[0092] The attitude measurement device is an inertial device such as IMU, INS, etc.; the attitude data is data such as the pitch angle, roll angle, and heading angle of the carrier aircraft.

[0093] Specifically, in step S2, the full altitude of the Doppler radar is stratified into a low altitude layer, a medium altitude layer and a high altitude layer;

[0094] The lower limit of the middle altitude layer is determined according to the delay and transition time of the Doppler radar radio frequency switch; the upper limit of the middle altitude layer is set in advance according to the mission of the Doppler radar, generally 1000-1500m, and can be flexibly set according to the mission type.

[0095] The height below the lower limit of the middle-altitude layer is the low-altitude layer; the height above the upper limit of the middle-altitude layer is the high-altitude layer.

[0096] More preferably, the lower limit of the middle altitude layer h1≥m·τ·c, where τ is the delay and transition time of the RF switch, c is the speed of light, and m is a preset integer;

[0097] For example, the delay and transition time of the switch is 100ns, and the distance corresponding to this time is about 15m. m is selected as 6 times greater than this distance as the upper limit of the low altitude layer, such as 100m.

[0098] The upper limit of the middle altitude layer is 1500m, and the range of the high altitude layer is greater than 1500m to the working upper limit of the Doppler radar.

[0099] At a low altitude (eg, less than 100 m, for example), the repetition frequency of the Doppler radar is a set of high repetition frequencies.

[0100] At the middle altitude layer (eg, 100m to 1500m), the repetition frequency of the Doppler radar is set according to the altitude value provided by the onboard altitude measuring device.

[0101] At high altitudes (eg, greater than 1500 m), the repetition frequency of the Doppler radar is a set of low repetition frequencies.

[0102] Preferably, different methods are selected to set the repetition frequency according to different height layers.

[0103] When the layer type is a low-altitude layer, a set of repetition frequencies corresponding to the low-altitude layer is used to resist the blocking of transmission and reception, that is, the repetition frequency of the Doppler radar is determined in combination with the above-mentioned attitude data, which is further refined as follows:

[0104] 1) In the low altitude layer, the Doppler radar beam illumination time is divided into N segments.

[0105] 2) Select a corresponding height value for each of the N segments, and determine a set of beam slant ranges in combination with the attitude data.

[0106] 3) According to the formula Calculate a set of repetition frequencies corresponding to the set of beam slant distances; where f r is the repetition frequency, R is the beam slant distance; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f i ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar.

[0107] For example, if f dmax =20kHz, then the value of n should ensure that f r ≥100kHz.

[0108] Specifically, the pulse duty cycle coefficient Δ of the output signal of the Doppler radar is the sum of the output signal pulse width T and the pulse repetition period T r The ratio of Δ is between 0.3 and 0.5, and is preferably 1 / 3.

[0109] 4) According to the group repetition frequency, the radar signal is sent and received in sequence, and the echo signal corresponding to the group repetition frequency is counted to see whether it is within the preset gate range. If it is not within the preset gate range, return to step 2) to reselect the height value and adjust the group repetition frequency until the echo signal is within the preset gate range.

[0110] Specifically, the counting of whether the echo signal corresponding to the group of repetition frequencies is within a preset gate range includes:

[0111] Signals are sent and received according to each repetition frequency in the group. When the echo falls within the receiving wave gate, it is marked as 1, otherwise, it is marked as 0, and the number num of echoes falling within the receiving wave gate is obtained;

[0112] Whether the echo signal corresponding to the group of repetition frequencies is within the preset gate range is determined according to the following preset conditions: if num is greater than N / 3, it is determined that the echo signal corresponding to the group of repetition frequencies is within the preset gate range and the repetition frequency is appropriately selected; otherwise, it is determined that the echo signal corresponding to the group of repetition frequencies is not within the preset gate range.

[0113] 5) The adjusted repetition frequency group is used as the repetition frequency of the Doppler radar within the low altitude layer.

[0114] For example, the beam irradiation time is divided into 8 segments, and a different repetition frequency is set in each segment, such as 1.40MHz, 1.36MHz, 1.26MHz, 1.21MHz, 1.11MHz, 0.91MHz, 0.85MHz, and 0.82MHz, to ensure that there is no transmission and reception blocking of echo data in at least 3 time periods corresponding to the repetition frequencies.

[0115] When the layer type is the middle altitude layer, that is, when the radar working altitude is in the middle altitude layer, the repetition frequency is determined according to the real-time working altitude data of the Doppler radar combined with the attitude data to resist the blocking of transmission and reception. Since the middle altitude layer is the main layer height of the Doppler radar, in order to increase the measurement accuracy, a repetition frequency is used for each altitude and each attitude in the middle altitude layer.

[0116] Specifically, the determination of the repetition frequency of the mid-altitude Doppler radar includes:

[0117] 1) Determine the beam slant range R based on the working height data and attitude data measured in real time;

[0118] 2) Calculate the real-time Doppler radar repetition frequency In the formula, f r is the repetition frequency; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f ri ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar;

[0119] 3) Using real-time calculation of Doppler radar repetition frequency f r as the Doppler radar repetition rate at the current altitude and attitude.

[0120] When the layer type is a high-altitude layer, a set of repetition frequencies corresponding to the high-altitude layer is used to resist the blocking of transmission and reception, that is, the repetition frequency of the Doppler radar is determined in combination with the above-mentioned attitude data, which is further refined as follows:

[0121] 1) In the high altitude layer, that is, from the upper limit of the middle altitude layer to the upper limit of the Doppler radar operation, the Doppler radar beam illumination time is divided into N segments;

[0122] 2) selecting a corresponding height value for each of the N segments, and determining a set of beam slant ranges in combination with the attitude data;

[0123] 3) According to the formula Calculate a set of repetition frequencies corresponding to the set of beam slant distances; where f r is the repetition frequency, R is the beam slant distance; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f i ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar;

[0124] 4) According to the group repetition frequency, radar signals are sent and received in sequence, and the echo signals corresponding to the group repetition frequency are counted to see whether they are within the preset gate range. If they are not within the preset gate range, the process returns to step 2) to reselect the height value and adjust the group repetition frequency until the echo signals are within the preset gate range.

[0125] Specifically, the counting of whether the echo signal corresponding to the group of repetition frequencies is within a preset gate range includes:

[0126] Signals are sent and received according to each repetition frequency in the group. When the echo falls within the receiving wave gate, it is marked as 1, otherwise, it is marked as 0, and the number num of echoes falling within the receiving wave gate is obtained;

[0127] Whether the echo signal corresponding to the group of repetition frequencies is within the preset gate range is determined according to the following preset conditions: if num is greater than N / 3, it is determined that the echo signal corresponding to the group of repetition frequencies is within the preset gate range and the repetition frequency is appropriately selected; otherwise, it is determined that the echo signal corresponding to the group of repetition frequencies is not within the preset gate range.

[0128] 5) The adjusted repetition frequency group is used as the repetition frequency of the Doppler radar within the high altitude layer.

[0129] For example: divide the beam irradiation time into 8 segments, set a different repetition frequency in each segment (generally a low repetition frequency, such as 0.37MHz, 0.35MHz, 0.32MHz, 0.28MHz, 0.25MHz, 0.23MHz, 0.16MHz, and 0.15MHz), and ensure that there is no blocking of transmission and reception of echo data in at least 3 time periods corresponding to the repetition frequencies.

[0130] More specifically, the Doppler radar in this embodiment includes four centrally symmetrical X-shaped radar beams; each radar beam corresponds to a slant range; that is, each radar beam uses the slant range of the radar beam to obtain the repetition frequency of the corresponding beam.

[0131] When the Doppler radar vehicle is flying horizontally, the four radar beams are centrally symmetrical, so the slant ranges of the four radar beams are equal, R1 = R2 = R3 = R4 = H i / sinβ, β is the angle between the center line of the radar beam and the ground projection.

[0132] When the Doppler radar vehicle maneuvers, the slant ranges of the four radar beams are:

[0133] R1=H / sinβ′1=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ;

[0134] R2=H / sinβ′2=H / (cosα·sinγ·cosv c ·cosγ c -cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ;

[0135] R3=H / sinβ′3=H / (cosα·sinγ·cosv c ·cosγ c-cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ;

[0136] R4=H / sinβ′4=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ;

[0137] In the formula, v c is the pitch angle of the vehicle, γ c is the rolling angle of the vehicle, β′1, β′2, β′3, β′4 are the angles between the center lines of beams 1 to 4 and their projections on the ground, respectively; γ is the angle between the center line of the entire beam and the X-axis of the vehicle's coordinate system; α is the angle between the projection of the center line of the entire beam on the plane where the center lines of beams 1 and 2 are located and the X-axis.

[0138] In summary, the Doppler radar full-range anti-transmission and reception blocking method provided in this embodiment solves the problem of the "altitude dead zone" of the Doppler radar by setting the repetition frequency in segments according to the relative altitude and controlling the repetition frequency using the relative altitude, thereby ensuring the altitude measurement accuracy and altitude measurement range of the Doppler radar during the flight of the aircraft.

[0139] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A Doppler radar full-range anti-transmission and reception blocking method, characterized in that: The steps include: In a normal speed measurement mode of the Doppler radar, obtaining working height data and attitude data of the Doppler radar, wherein the working height data is a relative height of the working position of the Doppler radar relative to the ground or sea surface; The full altitude of the Doppler radar is layered, and the altitude layer of the Doppler radar is determined according to the working altitude data; Determine the repetition frequency of the Doppler radar based on the altitude layer and attitude data; The Doppler radar irradiates the ground according to the repetition frequency to eliminate the "altitude dead zone" and altitude scale error of the Doppler radar; The full altitude stratification divides the altitude of the Doppler radar into a low altitude layer, a medium altitude layer and a high altitude layer; The altitude layer is a low altitude layer, and the repetition frequency of the Doppler radar is a group of high repetition frequencies; The altitude layer is a middle altitude layer, and the repetition frequency of the Doppler radar is set according to the altitude value provided by the airborne altitude measuring device; The altitude layer is a high altitude layer, and the repetition frequency of the Doppler radar is a group of low repetition frequencies; When at a low or high altitude, the determination of the Doppler radar repetition frequency includes: 1) In the corresponding altitude layer, divide the Doppler radar beam illumination time into N segments; 2) selecting a corresponding height value for each of the N segments, and determining a set of beam slant ranges in combination with the attitude data; 3) According to the formula Calculate a set of repetition frequencies corresponding to the set of beam slant distances; where f r is the repetition frequency, R is the beam slant distance; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f r ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar; 4) According to the group repetition frequency, radar signals are sent and received in sequence, and the echo signals corresponding to the group repetition frequency are counted to see whether they are within the preset gate range. If they are not within the preset gate range, the process returns to step 2) to reselect the height value and adjust the group repetition frequency until the echo signals are within the preset gate range. 5) The adjusted repetition frequency group is used as the repetition frequency of the Doppler radar within the altitude range; When at mid-altitude, the determination of Doppler radar repetition frequency includes: Determine the beam slant range R based on the working height data and attitude data measured in real time; Calculating Doppler Radar Repetition Frequency In the formula, f r is the repetition frequency; Δ is the pulse duty cycle coefficient of the output signal of the Doppler radar; n is a positive integer, and the value of n ensures that f r ≥5f dmax , f dmax is the maximum Doppler frequency of the Doppler radar.

2. The full-height anti-transmitting and receiving blocking method according to claim 1 is characterized in that: The lower limit of the middle altitude layer h1≥m·τ·c, where τ is the delay and transition time of the RF switch, c is the speed of light, and m is a preset integer; the height below the lower limit of the middle altitude layer is the low altitude layer; The upper limit setting range of the middle-altitude layer is 1000-1500m; the height above the upper limit of the middle-altitude layer is the high-altitude layer.

3. The full-height anti-transmitting and receiving blocking method according to claim 1 is characterized in that: The counting of whether the echo signal corresponding to the group of repetition frequencies is within a preset gate range includes: Signals are sent and received according to each repetition frequency in the group. When the echo falls within the receiving wave gate, it is marked as 1, otherwise, it is marked as 0, and the number num of echoes falling within the receiving wave gate is obtained; Whether the echo signal corresponding to the group of repetition frequencies is within the preset gate range is determined according to the following preset conditions: if num is greater than N / 3, it is determined that the echo signal corresponding to the group of repetition frequencies is within the preset gate range and the repetition frequency is appropriately selected; otherwise, it is determined that the echo signal corresponding to the group of repetition frequencies is not within the preset gate range.

4. The full-height anti-transmitting and receiving blocking method according to any one of claims 1 to 3, characterized in that: The Doppler radar includes four X-shaped radar beams that are centrally symmetrical; when the vehicle of the Doppler radar is flying level, the slant ranges of the four radar beams are R1=R2=R3=R4=H / sinβ, where β is the angle between the center line of the radar beam and the ground projection, and H is the working altitude of the Doppler radar.

5. The full-height anti-transmitting and receiving blocking method according to any one of claims 1 to 3, characterized in that: The Doppler radar includes four radar beams in a centrally symmetrical X shape; when the vehicle of the Doppler radar is maneuvering, the slant ranges of the four radar beams are respectively: R1=H / sinβ′1=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ; R2=H / sinβ′2=H / (cosα·sinγ·cosv c ·cosγ c -cosγ·sinv c -sinγ·sinα·sinγ c ·cosv c ; R3=H / sinβ3'=H / (cosα·sinγ·cosv c ·cosγ c -cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ; R4=H / sinβ′4=H / (cosα·sinγ·cosv c ·cosγ c +cosγ·sinv c +sinγ·sinα·sinγ c ·cosv c ; Where H is the operating altitude of the Doppler radar; β′1, β′2, β′3, and β′4 are the angles between the center lines of beams 1 to 4 and their projections on the ground; v c is the pitch angle of the vehicle, γ c is the rolling angle of the vehicle, γ is the angle between the center line of the entire beam and the X-axis of the vehicle body coordinate system; α is the angle between the projection of the center line of the entire beam on the plane where the center lines of beams 1 and 2 are located and the X-axis.

6. The full-height anti-transmitting and receiving blocking method according to any one of claims 1 to 3, characterized in that: is the pulse duty cycle coefficient of the output signal of the Doppler radar. Δ is the pulse width T of the output signal and the pulse repetition period T r The ratio of , Δ is between 0.3 and 0.

5.

7. The full-height anti-transmitting and receiving blocking method according to claim 1 is characterized in that: The method of obtaining the working altitude data and attitude data of the Doppler radar in the normal speed measurement mode of the Doppler radar includes: After the airborne Doppler radar is powered on, a self-test is performed to determine whether its hardware functions are normal; if not, the corresponding hardware is corrected until the functions are normal; After receiving the speed measurement command from the operator, the Doppler radar works in the normal speed measurement mode; The real-time working altitude data of the Doppler radar is obtained through the vehicle's radio altimeter or laser altimeter, and the attitude data of the Doppler radar is obtained through the vehicle's inertial navigation device.

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