CN115407328A - Doppler radar for measuring speed by using overlapped synthetic beams - Google Patents

Abstract

The present invention relates to a kind of Doppler radar that utilizes overlapped and synthesized beams to measure speed, comprising an antenna unit, a beam transceiver control unit and a beam transceiver control unit; The signal F2 radiates into space and overlaps in pairs to form 4 groups of overlapping composite beams; when receiving, respectively receive 4 groups of overlapping composite beam echo signals, and feed out the 4-channel signal F1 echo signal and the 4-channel signal F2 echo signal; the beam transceiver control unit is used to control the timing of the signals fed into the antenna unit to form 4 groups of overlapping synthetic beams; control the timing of the signals fed out of the antenna unit to receive the echo signals of 4 groups of overlapping synthetic beams; speed measurement processing The unit is used to extract the Doppler frequency shift of the overlapping area of 4 sets of overlapping synthetic beams, and measure the speed of the aircraft. The Doppler spectrum width of the invention is 20%-25% narrower than that of the common four-beam radar, thereby improving the spectrum purity and greatly improving the velocity measurement accuracy.

Description

A Doppler Radar Using Overlapped Synthetic Beams for Velocity Measurement

technical field

The invention relates to the technical field of radar, in particular to a Doppler radar for measuring speed by using overlapping synthetic beams.

Background technique

Doppler radar can automatically, continuously and accurately measure the velocity vector information of flying carriers such as UAVs. Its work is not limited by geographical and meteorological conditions, and its speed measurement accuracy is the same throughout the flight. The speed measurement accuracy of ordinary Doppler radar can only meet the requirements of civil aircraft, and it is difficult to meet the requirements of flight carriers with very high speed measurement accuracy. There are two main factors that affect the accuracy of Doppler speed radar: 1) the non-uniformity of the ground scattering coefficient; 2) the antenna beam width is not narrow enough, which is reflected in the Doppler frequency shift as a wide spectrum.

In the case of a certain radar antenna size and beam angle, the existing technology generally applies a correction factor according to the scattering characteristics of the current flight area, and corrects the speed measurement error of the Doppler radar in real time to improve the speed measurement accuracy of the Doppler radar. However, this method requires a large amount of flight data of various terrains to establish the target clutter model library. Existing Doppler radars use the pointing angles of four inclined beams to calculate the speed. The accuracy of the pointing angles of the echoes is extremely high. However, due to the limited antenna surface, the beams irradiate the ground is an area, and the radar receives a certain amount. For the spectrum of bandwidth, relying on the algorithm to correct the center of gravity leads to large errors.

Contents of the invention

In view of the above analysis, the embodiment of the present invention aims to provide a Doppler radar for speed measurement by using overlapping synthetic beams, so as to solve the problem of poor accuracy of existing Doppler speed measurement radars.

The technical scheme provided by the invention is:

The invention discloses a Doppler radar for measuring speed by using overlapping synthetic beams, which includes an antenna unit, a beam transmitting and receiving control unit, and a beam transmitting and receiving control unit;

The antenna unit is a shared antenna for sending and receiving. When transmitting, the fed-in 4-channel signal F1 is radiated to the space to form four center-symmetrical X-shaped radar beams; the fed-in 4-channel signal F2 is radiated to the space center Symmetrical X-shaped 4 radar beams; the 4 radar beams of the signal F1 and the 4 radar beams of the signal F2 are overlapped in pairs to form 4 groups of overlapping composite beams; when receiving, the responses of the 4 groups of overlapping composite beams are respectively received Wave signal, feed out 4-channel signal F1 echo signal and 4-channel signal F2 echo signal;

The beam transmitting and receiving control unit is used to control the timing of the signals fed into the antenna unit to form 4 groups of overlapping synthetic beams; control the timing of the signals fed out of the antenna unit to receive the echo signals of 4 groups of overlapping synthetic beams;

The speed measurement processing unit is used to extract the Doppler frequency shift of the overlapping area of the 4 sets of overlapping synthetic beams, and measure the speed of the aircraft.

Further, the antenna unit includes a radiation front subunit and a feed subunit;

The radiation front subunit includes N parallel and uniformly arranged radiation waveguides;

The feeding subunit includes first, second, third and fourth feeding waveguides with the same structure;

Both the radiation waveguide and the feeding waveguide are rectangular waveguides; wherein, the first and the third feeding waveguides are placed in a row on the left side of the radiation front subunit, feeding power to the left input end of each radiation waveguide; the second and the third The fourth feeding waveguide is arranged on the right side of the radiation front subunit, and feeds power to the right input end of each radiation waveguide;

Both ends of each feed waveguide are feed ports, and both ends of the first feed waveguide and the second feed waveguide on the upper layer of the 4 feed waveguides placed in pairs are fed into the signal F1 or fed out the signal The echo signal of F1; the echo signal of the feed-in signal F2 or the feed-out signal F2 at both ends of the third feed waveguide and the fourth feed waveguide in the lower layer of the 4 feed waveguides arranged in pairs.

Further, each radiation waveguide includes a horn section located at the left and right ends and a radiation section in the middle; wherein, the wide ends of the horn sections at the left and right ends will be respectively located at the first and third feeding waveguides at the left end of the radiation waveguide The second and fourth feeder waveguides at the right end are accommodated therein; the narrow end of the horn section is connected to the radiation section; the horn section is used to realize the transition of signals from the feeder wave to the radiation section; the radiation section is used for radiating signals.

Further, the radiation section of the radiation waveguide is a traveling wave slot radiation waveguide with slots on the narrow side; a plurality of narrow side slits with the same length and width and staggered inclination angles are arranged on the narrow side of the waveguide, and every two adjacent The intervals of the narrow-side cracks are the same, and the narrow-side cracks are distributed symmetrically on both sides relative to the center line of the radiation waveguide;

The first, second, third and fourth feeding waveguides have N narrow side cracks on the short side wall of the waveguide facing the radiation section, and transmit electromagnetic signals through the narrow side cracks and the radiating waveguide array .

在方向图Y向的偏转角

其中，i＝1或2，λ₁、λ₂为信号F1、F2在自由空间内的信号波长，λ_1g、λ_2g为信号F1、F2在波导内的导内波长；d₁为辐射波导上相邻两个窄边裂缝中心的间距；d₂为馈电波导上相邻两个窄边裂缝中心的间距；通过控制信号F1、F2的频率，控制信号F1、F2在方向图X、Y向的偏转角，从而控制交叠合成波束的交叠程度。Further, the deflection angle of a group of overlapping synthetic beams radiated outward by the antenna unit in the X direction of the pattern

The deflection angle in the Y direction of the pattern

Wherein, i=1 or 2, λ ₁ and λ ₂ are the signal wavelengths of the signals F1 and F2 in free space, λ _1g and λ _2g are the in-guide wavelengths of the signals F1 and F2 in the waveguide; d ₁ is the radiation waveguide The distance between the centers of two adjacent narrow-side cracks; _d2 is the distance between the centers of two adjacent narrow-side cracks on the feeder waveguide; through the frequency of the control signals F1 and F2, the control signals F1 and F2 are controlled in the X and Y directions of the pattern. The deflection angle of , thus controlling the degree of overlap of the overlapping synthetic beams.

其中，E(x)为幅度分布函数，P(x)为通过波导的功率，x是相对于天线半个长度归一化了的值；P(0)＝P₀；

φ(+1)＝[P(+1)-P₀]/[P(+1)+P₀]。Further, the amplitude distribution function of the narrow side crack on the radiation waveguide to the waveguide coupling function is

Wherein, E(x) is the amplitude distribution function, P(x) is the power passing through the waveguide, and x is the value normalized relative to the half length of the antenna; P(0)=P ₀ ;

φ(+1)=[P(+1)-P ₀ ]/[P(+1)+P ₀ ].

Further, each port of the first, second, third and fourth feed waveguides includes a waveguide isolator;

When one of the four ports in the first and second feed waveguides is incident, the isolators at the three ports function as reverse load absorbers;

When one of the four ports of the third and fourth feeding waveguides is incident, the isolators of the three ports function as reverse load absorption.

Further, the beam transmitting and receiving control unit adopts a time-sharing control method to control the first and third feeding waveguides or the second and fourth feeding waveguides placed on the same side in a certain transmission control time sequence. The ports are fed with signals F1 and F2 at the same time, and form a group of overlapping synthetic beams through the radiation front subunit to radiate into space; after the receiving control sequence after the transmitting control sequence, the echo signals of the overlapping synthetic beams are received, and from the The port on the side feeds out the signal F1 echo signal and the signal F2 echo signal.

Further, the beam transmitting and receiving control unit controls the irradiation order of the 4 sets of overlapping synthetic beams to be random irradiation, which is used to overcome co-channel interference.

Further, the speed measurement processing unit calculates the speed measurement information in the navigation information of the aircraft according to the Doppler frequency shift of the overlapping area as:

为多普勒雷达测量的在载体坐标系X、Y、Z轴的速度分量；f_d1、f_d2、f_d3、f_d4分别为4波束的相对信号F1的多普勒频移；γ₀为每个波束中心线与飞行器载体坐标系X轴的夹角；δ₀为波束线在相应平面上的投影与载体坐标系Y轴的夹角；λ为雷达发射信号F1的波长。In the formula,

is the velocity component measured by the Doppler radar on the X, Y, and Z axes of the carrier coordinate system; f _d1 , f _d2 , f _d3 , and f _d4 are the Doppler frequency shifts of the relative signal F1 of the 4 beams; γ ₀ is The angle between the centerline of each beam and the X-axis of the aircraft carrier coordinate system; δ ₀ is the angle between the projection of the beamline on the corresponding plane and the Y-axis of the carrier coordinate system; λ is the wavelength of the radar emission signal F1.

The Doppler radar of the present invention uses overlapped and synthesized beams for speed measurement. By receiving the overlapping beams of four echoes, the Doppler spectrum width is 20%-25% narrower than that of ordinary four-beam radars, thereby improving Spectrum purity greatly improves the accuracy of speed measurement.

In the present invention, the above technical solutions can also be combined with each other to realize more preferred combination solutions. Additional features and advantages of the invention will be set forth in the description which follows, and some of the advantages will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the matter particularly pointed out in the written description and appended drawings.

Description of drawings

The drawings are for the purpose of illustrating specific embodiments only and are not to be considered as limitations of the invention, and like reference numerals refer to like parts throughout the drawings.

Fig. 1 is a composition block diagram of Doppler radar in the embodiment of the present invention;

Fig. 2 is a top view of a Doppler radar four-beam antenna in an embodiment of the present invention;

Fig. 3 is a side view of a Doppler radar four-beam antenna in an embodiment of the present invention;

FIG. 4 is a schematic diagram of the relationship between two overlapping four beams generated by antennas in an embodiment of the present invention;

5 is a schematic diagram of the projection of the antenna pattern on the transmitting surface in the embodiment of the present invention;

FIG. 6 is a schematic diagram of a feeding structure of an overlapping beam antenna in an embodiment of the present invention.

Detailed ways

Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the application and together with the embodiments of the present invention are used to explain the principle of the present invention and are not intended to limit the scope of the present invention.

A specific embodiment of the present invention discloses a Doppler radar for speed measurement using overlapping synthetic beams, as shown in Figure 1, including an antenna unit, a beam transmitting and receiving control unit, and a beam transmitting and receiving control unit;

The antenna unit is a shared antenna for sending and receiving. When transmitting, the fed-in 4-channel signal F1 is radiated to the space to form four center-symmetrical X-shaped radar beams; the fed-in 4-channel signal F2 is radiated to the space center Symmetrical X-shaped 4 radar beams; the 4 radar beams of the signal F1 and the 4 radar beams of the signal F2 are overlapped in pairs to form 4 groups of overlapping composite beams; when receiving, the responses of the 4 groups of overlapping composite beams are respectively received Wave signal, feed out 4-channel signal F1 echo signal and 4-channel signal F2 echo signal;

The beam transceiver control unit is used to control the timing of the signals fed into the antenna unit to form 4 groups of overlapping composite beams; control the timing of the echo signals fed out by the antenna unit to receive the echo signals of 4 groups of overlapping composite beams;

The speed measurement processing unit is used to extract the Doppler frequency shift of the overlapping area of the 4 sets of overlapping synthetic beams, and measure the speed of the aircraft.

By extracting the Doppler frequency shift in the overlapping area of 4 groups of overlapping synthetic beams, the Doppler spectral width is 20%-25% narrower than that of the ordinary four-beam radar, thereby improving the spectral purity and effectively eliminating multiple The influence of the Puler radar on the ground scattering improves the speed measurement accuracy by at least 5 times, greatly improving the speed measurement accuracy.

Specifically, as shown in Figure 2 and Figure 3, the antenna unit includes a radiation front sub-unit and a feed sub-unit;

The radiation front subunit includes N parallel and uniformly arranged radiation waveguides;

The feeding subunit includes first, second, third and fourth feeding waveguides with the same structure;

Both the radiation waveguide and the feeding waveguide are rectangular waveguides; wherein, the first and third feeding waveguides are placed in a row on the left side of the radiation front subunit, feeding power to the left input end of each radiation waveguide ; The second and fourth feeding waveguides are arranged and placed on the right side of the radiation front subunit, feeding power to the right input end of each radiation waveguide;

Both ends of each feed waveguide are feed ports, and the two ends of the first feed waveguide and the two ends of the second feed waveguide in the upper layer of the four feed waveguides placed in pairs are fed with signals F1 or the echo signal of the feed-out signal F1; the two ends of the third feed waveguide and the two ends of the fourth feed waveguide in the lower layer of the 4 feed waveguides placed in pairs are fed into the signal F2 or the feed-out signal The echo signal of F2.

The frequencies of the signal F1 and the signal F2 are set to two frequencies with a certain frequency difference from each other. When the N radiation waveguides are radiated outward, due to the different responses of the antenna to signals of different frequencies, there will be a phenomenon in the radiation field of the antenna. Patterns for two different frequencies. By controlling the range of the frequency difference, the two beams generated by the signal F1 and the signal F2 can be controlled to overlap to a certain extent. Therefore, when the antenna of this embodiment transmits the signals of the frequency F1 and the frequency F2, it will produce a signal as shown in Figure 4. The projections of the four overlapping beams on the ground are shown in Figure 5. Since the two beams are very close together, the ground reflection characteristics do not change. In the case that the bias angle has been corrected, it can be found that the frequency corresponding to the intersection of the Doppler spectrum envelopes of the two signals has nothing to do with the type of reflector.

More specifically, in order to realize the signal interaction between the feed waveguide and the radiation waveguide arranged in pairs, as shown in FIG. 6, each radiation waveguide includes horn sections located at the left and right ends and a radiation section in the middle; wherein, The wide ends of the horn sections at the left and right ends accommodate the first and third feed waveguides at the left end of the radiation waveguide and the second and fourth feed waveguides at the right end respectively; the narrow ends of the horn sections are connected to the radiation section; the horn section It is used to realize the transition of the signal from the feeding wave to the radiation section; the radiation section is used to radiate the signal.

Preferably, the radiation section of the radiation waveguide is a traveling wave slot radiation waveguide with slots on the narrow side; a plurality of narrow side cracks with the same length and width and staggered inclination angles are arranged on the narrow side of the waveguide, and every two adjacent The intervals of the narrow-side cracks are the same, and the narrow-side cracks are distributed symmetrically on both sides relative to the center line of the radiation waveguide; the distance between the narrow-side cracks of the radiation waveguide determines the X-direction beam pointing angle of the pattern.

The first, second, third and fourth feeding waveguides have N narrow side cracks on the short side wall of the waveguide facing the radiating section, and the N narrow side cracks have staggered inclination angles. The edge crack and the radiating waveguide array transmit electromagnetic signals. The pitch of the narrow side slits of the feeding waveguide is the same as that of the emitting radiation waveguides in the emitting radiation waveguide array. Therefore, the spacing of the narrow side cracks of the radiation waveguide determines the beam pointing angle in the Y direction of the pattern.

在方向图Y向的偏转角

其中，i＝1或2，1代表信号F1，2代表信号F2；λ₁、λ₂为信号F1、F2在自由空间内的信号波长，λ_1g、λ_2g为信号F1、F2在波导内的导内波长；d₁为辐射波导上相邻两个窄边裂缝中心的间距；d₂为馈电波导上相邻两个窄边裂缝中心的间距；通过控制信号F1、F2的频率，控制信号F1、F2在方向图X、Y向的偏转角θ_i、φ_i，从而控制交叠合成波束的交叠程度。More specifically, the deflection angle of a group of overlapping synthetic beams radiated outward by the antenna unit in the X direction of the pattern

The deflection angle in the Y direction of the pattern

Among them, i=1 or 2, 1 represents the signal F1, 2 represents the signal F2; λ ₁ , λ ₂ are the signal wavelengths of the signals F1 and F2 in free space, λ _1g , λ _2g are the wavelengths of the signals F1 and F2 in the waveguide wavelength in the guide; d ₁ is the distance between the centers of two adjacent narrow-side cracks on the radiation waveguide; d ₂ is the distance between the centers of two adjacent narrow-side cracks on the feeding waveguide; by controlling the frequencies of the signals F1 and F2, the control signal The deflection angles θ _i and φ _i of F1 and F2 in the X and Y directions of the pattern control the overlapping degree of the overlapping synthetic beams.

The four sets of overlapping synthetic beams in this embodiment are X-shaped with central symmetry, and their beam pointing angles are strictly symmetrical, which ensures that the subsequent calculation of the three directions of the flying carrier is based on the relationship between the Doppler frequency offset and the beam pointing angle. precise flight speed.

Furthermore, unlike the traditional traveling wave array design, in order to make the incoming waves in two directions of a single radiation waveguide have symmetrical pattern characteristics, and ensure that the slot coupling function is an even function. The radiating waveguide of this embodiment arranges the slit symmetrically relative to both ends, that is, the coupling function of the slit to the waveguide is an even function relative to the middle of the radiation aperture, and the amplitude distribution function is no longer symmetrical (traditional traveling wave antennas are symmetrical).

Therefore, the amplitude distribution function of the coupling function of the narrow side crack to the waveguide of the emitting radiation waveguide in this embodiment is

Wherein, E(x) is the amplitude distribution function, P(x) is the power passing through the waveguide, and x is the value normalized relative to the half length of the antenna; P(0)=P ₀ ;

φ(+1)=[P(+1)-P ₀ ]/[P(+1)+P ₀ ].

After the degree distribution function (amplitude characteristic) is obtained, the pattern characteristic can be obtained, so as to comprehensively solve the four-beam symmetry problem of the pattern.

And the inclination angle and cutting depth of each slot of a single waveguide with narrow side slots can be determined through the amplitude distribution function and the coupling function of the waveguide.

More specifically, each port of the first, second, third and fourth feed waveguides includes a waveguide isolator;

in,

When one of the four ports in the first and second feed waveguides is incident or outgoing, the isolators of the three ports function as reverse load absorption;

When one of the four ports of the third and fourth feeding waveguides is incident or outgoing, the isolators of the three ports function as reverse load absorption.

The transmission and reception among the beams are independent of each other through isolation, and each beam can be transmitted or received by using the radiation waveguide of the entire radiation front subunit of the antenna unit.

In a specific embodiment of the present invention, the overall structural size of the antenna unit is no more than 400mm×200mm×30mm.

Among them, the radiation array sub-unit is composed of 22 radiation waveguides, and each radiation waveguide has 36 narrow-side slots with staggered inclination angles, which are used to radiate electromagnetic energy to space. The spacing of the radiation slots is 11 mm. The size is 17mm×4mm; the amplitude distribution function of the radiation waveguide is weighted by -20dB Chebyshev, the inclination angle of each slot is determined according to the weighted result, and the cutting depth is determined according to the simulated resonance size of each slot.

Of the 4 feed waveguides included in the feed sub-unit, two of them are arranged on the left side, and the other two are stacked and placed on the right side. The size of the feeding waveguide is 18.75mm×4mm; there are also 22 narrow-side slots with staggered inclination angles in the direction of the narrow side of each feeding waveguide towards the radiation waveguide; the spacing between the feeding waveguide slots is 9mm.

Preferably, the frequencies of the feed-in signal F1 and the signal F2 are 13.325 GHz and 13.5 GHz, respectively.

In this embodiment, the beam transmitting and receiving control unit adopts a time-sharing control method, and controls the first and third feeding waveguides or the second and fourth feeding waveguides placed in a row at a certain transmission control time sequence. The ports on the side are fed with signals F1 and F2 at the same time, and a group of overlapping synthetic beams are radiated to space through the radiation front sub-unit; after the receiving control sequence after the transmitting control sequence, the echo signal of the overlapping synthetic beam is received, The signal F1 echo signal and the signal F2 echo signal are fed out from the port on this side.

A control method of time-sharing control in this embodiment includes:

1) At time T1, the beam transceiver control unit controls the antenna unit to transmit; the feed port 1 on one side of the first feed waveguide feeds the signal F1, and the feed port 5 on the same side of the third feed waveguide is listed together at the same time Feed the signal F2 to generate two beams in the geodetic quadrant I of the beam projection, one beam is generated by the signal F1, the azimuth angle is 1, and the elevation angle is 1; the other beam is generated by the signal F2, the azimuth angle is 5, and the elevation angle is 5 . Since the frequencies of the signal F1 and the signal F2 are very close, the angle difference between the azimuth angle 1 and 5 and the elevation angle 1 and 5 is very small, between 0.5-3 degrees, the frequency difference between the signal F1 and the signal F2 can be passed Control; thus, overlapping beams with mutually incoherent frequencies will be generated, and the projection on the ground will produce overlapping area projection.

2) After the radiating front subunit radiates the signal, the beam transceiver control unit controls the antenna unit to receive; the echo signals of the two beams generated in the ground quadrant I are received by the antenna unit, and are fed from the feed port 1 of the first feed waveguide and the feed port 5 of the third feed waveguide are fed out to the velocity measurement processing unit to extract the Doppler spectrum information in the overlapping region of the beams formed by the two frequencies, and the azimuth and Pitch angle for speed calculation;

3) At time T2, the beam transceiver control unit controls the antenna unit to transmit; the feed port 2 on one side of the first feed waveguide feeds the signal F1, and the feed port 6 on the same side of the third feed waveguide is listed together at the same time Feed the signal F2 to generate two beams in the geodetic quadrant II of the beam projection, one beam is generated by the signal F1, the azimuth angle is 2, and the elevation angle is 2; the other beam is generated by the signal F2, the azimuth angle is 6, and the elevation angle is 6 . Since the frequencies of the signal F1 and the signal F2 are very close, the angle difference between the azimuth angle 2 and 6, and the elevation angle 2 and 6 is very small, between 0.5-3 degrees, and the frequency difference between the signal F1 and the signal F2 can be passed Control; thus, overlapping beams with mutually incoherent frequencies will be generated, and the projection on the ground will produce overlapping area projection.

4) After the radiating front subunit radiates the signal, the beam transceiver control unit controls the antenna unit to receive; the echo signals of the two beams generated in the geodetic quadrant II are received by the antenna unit, from the feed port 2 of the first feed waveguide and the feed port 6 of the third feed waveguide are fed out to the speed measurement processing unit, and the spectrum information of the overlapping area of the two frequency forming beams is extracted, and the azimuth and elevation angles after the overlap of the beams of the known ports 1 and 5 are known. speed solution.

5) The working principles of the other four feeding ports are the same as above, and the projections of the four beams generated on the ground are also X-shaped, and they are also orthocentrically symmetrical about the antenna; the overlapping beams generated by ports 1 and 5 are in a quadrant, and the port 2 and 6 produce overlapping beams in two quadrants, ports 3 and 7 produce overlapping beams in three quadrants, and ports 4 and 8 produce overlapping beams in four quadrants.

Therefore, by receiving the overlapping beams of four echoes, the high-frequency receiving system of the radar can extract the spectrum of the beam overlapping area, and the spectrum width should be narrowed by 20%-25%, thereby improving the spectrum purity and greatly improving the speed measurement accuracy.

Furthermore, if a fixed sequence of 4 groups of overlapping beams are used for irradiation in each irradiation cycle, if co-channel interference occurs, it will occur in each irradiation process, thus affecting the speed measurement performance of Doppler radar. It will have a greater impact, and even lead to the unavailability of speed measurement data.

Therefore, the beam transmitting and receiving control unit controls the irradiation sequence of the 4 sets of overlapping synthetic beams to be random irradiation, which is used to overcome co-channel interference.

Specifically, methods to overcome co-channel interference include:

1) Numbering the 4 groups of overlapping synthetic beams of the Doppler radar; arranging the numbers to form a one-dimensional array, which is used as the irradiation sequence set of the 4 groups of overlapping synthetic beams of the Doppler radar;

More specifically, the 4 groups of overlapping synthetic beams are numbered as 1, 2, 3, and 4;

When 4 numbers are arranged to form 24 combinations, a one-dimensional array with a length of 24 is formed, which is:

{3142,4312,3421,4321,2413,4213,2431,4231,2314,3214,2341,3241,1423,4123,1432,4132,1324,3124,1342,3142,1234,1243,2134,2143}.

Using the one-dimensional array as the irradiation sequence set of each beam of the Doppler radar,

2) Generate a corresponding random number in each data acquisition cycle;

The random number can be generated by a software random number generator, or by a hardware random number generator.

3) Perform a remainder operation on the random number of the current data acquisition period and the length of the array; use the remainder value to index the value at the corresponding position in the array, and use the order of numbers in the value as the beam irradiation sequence of the current period.

Specifically, the random number generated by the random number generator is used to take the remainder of 24, the range of the remainder is [0,23], and then the remainder value is used to index the sequence array corresponding to the subscript to determine the beam irradiation sequence of the current period.

For example, if the generated random number is 0, the remainder is 0. If the first value in the array is 3142, the order of beam irradiation is 3-1-4-2. If the generated random number is 47, the remainder is 23. If the twenty-fourth value 2143 of the array is found, the order of beam irradiation is 2-1-4-3, and so on for others, so as to achieve random control of beam irradiation. Therefore, the same-frequency interference problem caused by the fixed beam irradiation sequence in each data acquisition cycle is overcome.

Further, the speed measurement processing unit calculates the speed measurement information in the navigation information of the aircraft according to the Doppler frequency shift of the overlapping area as:

为多普勒雷达测量的在载体坐标系X、Y、Z轴的速度分量；γ₀为交叠波束中心线与飞行器载体坐标系X轴的夹角；δ₀为交叠波束线在相应平面上的投影与载体坐标系Y轴的夹角；当λ为雷达发射信号F1的波长时，f_d1、f_d2、f_d3、f_d4分别为4波束的相对信号F1的多普勒频移；当λ为雷达发射信号F2的波长时，f_d1、f_d2、f_d3、f_d4分别为4波束的相对信号F2的多普勒频移。In the formula,

is the velocity component measured by the Doppler radar on the X, Y, and Z axes of the carrier coordinate system; γ ₀ is the angle between the centerline of the overlapping beam and the X axis of the aircraft carrier coordinate system; δ ₀ is the overlapping beamline on the corresponding plane The angle between the projection on and the Y axis of the carrier coordinate system; when λ is the wavelength of the radar transmitted signal F1, f _d1 , f _d2 , f _d3 , and f _d4 are the Doppler frequency shifts of the relative signal F1 of the 4 beams; When λ is the wavelength of the radar transmitted signal F2, f _d1 , f _d2 , f _d3 , and f _d4 are the Doppler frequency shifts of the 4 beams relative to the signal F2.

Therefore, as long as the Doppler instantaneous frequency values of the four overlapping beams are measured in real time, the various components of the radar carrier velocity vector (that is, the longitudinal velocity along the heading, the lateral velocity perpendicular to the heading) can be calculated in real time according to the above formula. speed and vertical speed) for navigation purposes.

In summary, this embodiment effectively eliminates the influence of Doppler radar on ground scattering by using overlapping synthetic beams, so that the beam projection area used by the Doppler radar antenna changes from the original single beam area to the overlapping area of beams. The beam projection area is reduced, and the available beam is sharpened to a certain extent, thereby improving the Doppler spectrum purity and improving the speed measurement accuracy by at least 5 times. For Doppler radar, the speed measurement accuracy of Doppler navigation radar is directly related to the effect of other inertial navigation integrated navigation. Therefore, overlapping beam antenna technology is of great significance to high-precision Doppler speed radar.

垂向

侧向

测速范围为25m/s≤v_x≤250m/s、|v_y|≤40m/s，|v_z|≤40m/s。三轴向随机误差：≤1.5m/s。The test results show that the speed measurement accuracy is forward

vertically

sideways

The speed measurement range is 25m/s≤v _x ≤250m/s, |v _y |≤40m/s, |v _z |≤40m/s. Three-axis random error: ≤1.5m/s.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention.

Claims (10)

1. A Doppler radar utilizing overlapping synthetic beams to measure speed is characterized in that it comprises an antenna unit, a beam transmitting and receiving control unit and a beam transmitting and receiving control unit; The antenna unit is a shared antenna for sending and receiving. When transmitting, the fed-in 4-channel signal F1 is radiated to the space to form four center-symmetrical X-shaped radar beams; the fed-in 4-channel signal F2 is radiated to the space center Symmetrical X-shaped 4 radar beams; the 4 radar beams of the signal F1 and the 4 radar beams of the signal F2 are overlapped in pairs to form 4 groups of overlapping composite beams; when receiving, the responses of the 4 groups of overlapping composite beams are respectively received Wave signal, feed out 4-channel signal F1 echo signal and 4-channel signal F2 echo signal; The beam transmitting and receiving control unit is used to control the timing of the signals fed into the antenna unit to form 4 groups of overlapping synthetic beams; control the timing of the signals fed out of the antenna unit to receive the echo signals of 4 groups of overlapping synthetic beams; The speed measurement processing unit is used to extract the Doppler frequency shift of the overlapping area of the 4 sets of overlapping synthetic beams, and measure the speed of the aircraft. 2. Doppler radar according to claim 1, is characterized in that, described antenna unit comprises radiation front subunit and feed subunit; The radiation front subunit includes N parallel and uniformly arranged radiation waveguides; The feeding subunit includes first, second, third and fourth feeding waveguides with the same structure; Both the radiation waveguide and the feeding waveguide are rectangular waveguides; wherein, the first and the third feeding waveguides are placed in a row on the left side of the radiation front subunit, feeding power to the left input end of each radiation waveguide; the second and the third The fourth feeding waveguide is arranged on the right side of the radiation front subunit, and feeds power to the right input end of each radiation waveguide; Both ends of each feed waveguide are feed ports, and both ends of the first feed waveguide and the second feed waveguide on the upper layer of the 4 feed waveguides placed in pairs are fed into the signal F1 or fed out the signal The echo signal of F1; the echo signal of the feed-in signal F2 or the feed-out signal F2 at both ends of the third feed waveguide and the fourth feed waveguide in the lower layer of the 4 feed waveguides arranged in pairs. 3. Doppler radar according to claim 1, is characterized in that, described each radiation waveguide comprises the horn section that is positioned at left and right two ends and the radiation section in the middle; Wherein, the horn section wide end of left and right two ends The first and third feeder waveguides located at the left end of the radiation waveguide and the second and fourth feeder waveguides at the right end are accommodated therein; the narrow end of the horn section is connected to the radiation section; the horn section is used to realize the radiation of signals from the feeder waveguide transition of segments; the radiating segments are used to radiate signals. 4. Doppler radar according to claim 3, is characterized in that, the radiation section of described radiation waveguide is the traveling wave slot radiation waveguide of narrow side slit; Multiple same length, width are set on the narrow side of waveguide The narrow-side cracks with staggered dip angles, the intervals between every two adjacent narrow-side cracks are the same, and the narrow-side cracks are symmetrically distributed on both sides relative to the center line of the radiation waveguide; The first, second, third and fourth feeding waveguides have N narrow side cracks on the short side wall of the waveguide facing the radiation section, and transmit electromagnetic signals through the narrow side cracks and the radiating waveguide array . 5. Doppler radar according to claim 3, is characterized in that, the deflection angle of a group of overlapping synthetic beams of the external radiation of the antenna unit in the X direction of the pattern

The deflection angle in the Y direction of the pattern

Wherein, i=1 or 2, λ ₁ and λ ₂ are the signal wavelengths of the signals F1 and F2 in free space, λ _1g and λ _2g are the in-guide wavelengths of the signals F1 and F2 in the waveguide; d ₁ is the radiation waveguide The distance between the centers of two adjacent narrow-side cracks; _d2 is the distance between the centers of two adjacent narrow-side cracks on the feeder waveguide; through the frequency of the control signals F1 and F2, the control signals F1 and F2 are controlled in the X and Y directions of the pattern. The deflection angle of , thus controlling the degree of overlap of the overlapping synthetic beams. 6. Doppler radar according to claim 3, is characterized in that, the amplitude distribution function of the narrow edge crack on the described radiation waveguide to waveguide coupling function is

Wherein, E(x) is the amplitude distribution function, P(x) is the power passing through the waveguide, and x is the value normalized relative to the half length of the antenna; P(0)=P ₀ ;

φ(+1)=[P(+1)-P ₀ ]/[P(+1)+P ₀ ]. 7. The Doppler radar of claim 5, wherein each port of the first, second, third and fourth feed waveguides includes a waveguide isolator; When one of the four ports in the first and second feed waveguides is incident, the isolators at the three ports function as reverse load absorbers; When one of the four ports of the third and fourth feeding waveguides is incident, the isolators of the three ports function as reverse load absorption. 8. The Doppler radar according to claim 3, characterized in that, the beam transceiver control unit adopts a time-sharing control control mode, and controls the first and third placed beams in a certain emission control sequence. The ports on the same side of the feeder waveguide or the second and fourth feeder waveguides are simultaneously fed with signals F1 and F2, and radiate to space through the radiation front subunit to form a group of overlapping composite beams; the receiving control sequence after the transmitting control sequence , receiving the echo signals of the overlapping synthetic beams, feeding out the echo signals of the signal F1 and the echo signal of the signal F2 from the ports on this side. 9. The Doppler radar according to claim 8, characterized in that, the beam transceiver control unit controls the irradiation sequence of the 4 sets of overlapping synthetic beams to be random irradiation, which is used to overcome co-channel interference. 10. Doppler radar according to claim 1, characterized in that, The speed measurement processing unit calculates the speed measurement information in the navigation information of the aircraft according to the Doppler frequency shift in the overlapping area as:

In the formula,

is the velocity component measured by the Doppler radar on the X, Y, and Z axes of the carrier coordinate system; f _d1 , f _d2 , f _d3 , and f _d4 are the Doppler frequency shifts of the relative signal F1 of the 4 beams; γ ₀ is The angle between the centerline of each beam and the X-axis of the aircraft carrier coordinate system; δ ₀ is the angle between the projection of the beamline on the corresponding plane and the Y-axis of the carrier coordinate system; λ is the wavelength of the radar emission signal F1.

Images