CN116186937A - Log periodic antenna linear array design method considering sidelobe level and application thereof - Google Patents
Log periodic antenna linear array design method considering sidelobe level and application thereof Download PDFInfo
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Abstract
The invention discloses a design method of a log periodic antenna considering side lobe level, which comprises the following steps: acquiring a normalized direction function of the main lobe direction of a uniform linear array formed by a plurality of antenna units, which is influenced by the scanning width of a beam of the main lobe direction; obtaining the corresponding relation between the maximum sidelobe level and the beam scanning width, and obtaining a beam width factor corresponding to the target sidelobe level according to the corresponding relation; determining the scale factors and the interval factors of the corresponding antenna units according to the beam width factors; determining the gain of the antenna array, and determining the number of antenna units in the uniform linear array according to the gain of the antenna array; and determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating to obtain vibrator parameters of corresponding antenna units to complete the linear array design. The antenna array can solve the problems that the complexity and the cost of feeding are increased due to the fact that the traditional antenna array controls the side lobe level in a mode of changing the interval, the feeding amplitude and the phase of the antenna units.
Description
Technical Field
The present invention relates to the field of antenna technologies, and in particular, to a method for designing a log periodic antenna linear array with consideration of side lobe levels, a device for designing a log periodic antenna linear array with consideration of side lobe levels, an electronic device, and a computer readable storage medium.
Background
Phased array antennas have been a hotspot in the field of antenna research, which can achieve beam scanning by changing the feed phase of the antenna elements, and are widely used in radio systems. As the beam scan angle increases, the maximum sidelobe level will also increase. Too high a side lobe level may cause "false alarm targets" in other directions for radar and interference for communication targets in other directions. Therefore, effective control of the side lobe level is very critical when designing phased array antennas.
Conventional side lobe level control methods generally include the following methods: (1) Changing the spacing between the antenna units, namely non-equidistant arrangement; (2) Changing the feeding amplitude of the antenna unit, and adopting non-constant amplitude feeding; (3) Changing the feed phase of the antenna unit, and adopting a nonlinear variation phase difference; (4) any combination of the above three methods. The above methods can effectively inhibit the side lobe level of the antenna array, but most of the methods are to perform a large amount of computation by means of intelligent optimization algorithms (genetic algorithms, particle swarm algorithms and the like), and the methods add complexity and cost of feeding to the design of the antenna array (for example, a method of non-equal amplitude and non-linear phase difference change will add an amplitude control device, a phase control device and the like), so that a method for effectively inhibiting the side lobe level without adding additional control devices and computation complexity is a current urgent problem.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a design method of a log periodic antenna linear array with controllable side lobe level, which can solve the problems of increasing the complexity and cost of feeding caused by controlling the side lobe level in a mode of changing the interval, the feeding amplitude and the phase of antenna units in the traditional antenna array.
In one aspect, a first embodiment of the present invention provides a method for designing a log periodic antenna linear array in consideration of side lobe levels, including: acquiring a normalized direction function of the main lobe direction of a uniform linear array formed by a plurality of logarithmic period dipole antenna units, wherein the normalized direction function is influenced by the beam scanning width of the antenna units; obtaining a corresponding relation between the maximum side lobe level and the beam scanning width according to the normalized direction function, and obtaining a beam width factor corresponding to the target side lobe level according to the corresponding relation; determining a scale factor and a spacing factor of the corresponding antenna unit according to the beam width factor; determining antenna array gain according to the scale factor and the interval factor, so as to determine the number of antenna units in the uniform linear array according to the antenna array gain; and determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating the oscillator parameters of the corresponding antenna units according to the highest working frequency, the scale factors and the interval factors to complete the linear array design.
In one embodiment of the present invention, the normalized direction function is:
where M is the number of antenna elements, ψ=kd (sin θ -sin θ) 0 ) M is defined as a beam width factor; wherein (1)>
Is the wave constant, d is the antenna unit spacing, theta is the included angle between the main lobe and the normal direction, theta 0 Is the main lobe direction.
In one embodiment of the present invention, the obtaining the correspondence between the maximum sidelobe level and the beam width factor according to the normalized direction function includes: the side lobe level is expressed as:
wherein θ 0 Representing the beam scanning direction, θ s Representing the grating lobe angle.
In one embodiment of the present invention, the obtaining the beam width factor corresponding to the target side lobe level according to the correspondence includes: the beam width factor is calculated as:
in one embodiment of the present invention, the determining the number of antenna units in the uniform linear array according to the antenna array gain includes: the antenna array gain is expressed as: g (dB) =g 0 (dB) +10log 10 (M) +Δg, thereby calculating the number of antenna elements M; wherein G is 0 (dB) is the antenna element gain in free space and Δg is the mirror gain of the antenna element.
In one embodiment of the present invention, the determining the lowest operating frequency of the uniform linear array according to the normalized direction function includes: obtaining an antenna unit interval range which does not have grating lobes and is not overlapped among the antenna units of the uniform linear array according to the normalization direction function; and determining a corresponding beam scanning bandwidth according to the antenna unit interval range so as to determine the lowest working frequency according to the beam scanning bandwidth and the highest working frequency.
In one embodiment of the present invention, the calculating to obtain the oscillator parameters corresponding to the antenna units includes: calculating to obtain the number of vibrators according to the highest working frequency and the lowest working frequency; and calculating the length of the longest oscillator and the length of the shortest oscillator according to the scale factors and the interval factors, and calculating the distance between every two adjacent oscillators according to an antenna theory.
On the other hand, the embodiment of the invention provides a log periodic antenna linear array design device considering side lobe level, which comprises: the normalized direction function acquisition module is used for acquiring a normalized direction function of which the main lobe direction of a uniform linear array formed by a plurality of dipole antenna units with logarithmic periods is influenced by the beam scanning width of the antenna units; the beam width factor obtaining module is used for obtaining the corresponding relation between the maximum sidelobe level and the beam scanning width according to the normalized direction function and obtaining the beam width factor corresponding to the target sidelobe level according to the corresponding relation; a scale/interval factor determining module, configured to determine a scale factor and an interval factor of a corresponding antenna unit according to the beam width factor; the antenna unit number determining module is used for determining antenna array gain according to the scale factor and the interval factor so as to determine the number of antenna units in the uniform linear array according to the antenna array gain; and the oscillator parameter calculation module is used for determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating the oscillator parameters of the corresponding antenna units according to the highest working frequency, the scale factors and the interval factors to complete the linear array design.
In still another aspect, an embodiment of the present invention provides an electronic device, including: a memory and one or more processors coupled to the memory, the memory storing a computer program for executing the computer program to implement the log periodic antenna design method taking into account sidelobe levels as in any of the embodiments described above.
In yet another aspect, an embodiment of the present invention proposes a computer-readable storage medium storing computer-executable instructions for performing the log-periodic antenna design method taking into account the sidelobe level as in any one of the embodiments described above.
As can be seen from the above, compared with the prior art, the above solution contemplated by the present invention may have one or more of the following advantages:
(1) By analyzing the relation between the side lobe level of the antenna unit and the beam scanning bandwidth, the side lobe level meeting the requirement can be realized by controlling the beam scanning bandwidth, and the beam scanning bandwidth can be realized by designing the structural parameters of the log-periodic dipole antenna linear array, so that the additional increase of a control device and the calculation complexity is avoided;
(2) The condition of generating grating lobes when antenna units are assembled and the influence of different antenna units on the grating lobes are simultaneously analyzed and considered, so that the space between the antenna units which meets the condition of not generating grating lobes is calculated more accurately, and the main lobe deviation and the grating lobes can be effectively avoided;
(3) The limitation of the beam scanning bandwidth of the log periodic dipole uniform linear array which does not have grating lobes and is not overlapped among the antenna units is obtained by considering the relation between different antenna units and the beam scanning bandwidth, and the effect of maximizing the linear array bandwidth can be achieved on the premise that the grating lobes and the antenna units are not overlapped.
Other aspects of the features of the invention will become apparent from the following detailed description, which refers to the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
fig. 1 is a flowchart of a log periodic antenna design method considering side lobe level according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a log-periodic dipole antenna according to an embodiment of the present invention;
FIG. 3 is a normalized direction diagram of a 16-element uniform linear array provided by an embodiment of the present invention under different scanning angles with different pitches;
fig. 4 is a schematic diagram of a log-periodic dipole antenna according to an embodiment of the present invention;
FIG. 5 is a horizontal plane normalized pattern of a log periodic dipole antenna at different beamwidth factors provided by an embodiment of the present invention;
fig. 6 is a normalized pattern when a beam of a 16-element log periodic dipole linear array (d=0.645 λ) provided by an embodiment of the present invention is scanned to 30 °;
fig. 7 is a normalized pattern when a beam of a 16-element log periodic dipole linear array (d=0.75λ) provided by an embodiment of the present invention is scanned to 30 °;
fig. 8 is a normalized pattern when a beam of a 16-element log periodic dipole linear array (d=0.85λ) provided by an embodiment of the present invention is scanned to 30 °;
fig. 9 is a normalized pattern when a beam of a 16-element log-periodic dipole linear array (d=λ) provided by an embodiment of the present invention is scanned to 30 °;
fig. 10 is a normalized pattern when a beam of a 16-element log periodic dipole linear array (d=1.15λ) provided by an embodiment of the present invention is scanned to 30 °;
FIG. 11 is a schematic view of angles corresponding to grating lobes at different pitches according to an embodiment of the present invention;
FIG. 12 is a diagram of a log periodic dipole antenna simulation model according to an embodiment of the present invention;
FIG. 13 is a graph of gain for a log periodic dipole antenna according to an embodiment of the present invention;
FIG. 14 is a chart of standing wave ratio of a log-periodic dipole antenna according to an embodiment of the present invention;
FIG. 15 is a graph of beam width of a log periodic dipole antenna according to an embodiment of the present invention;
FIG. 16 is a simulated contrast pattern of a log periodic dipole antenna in a horizontal plane according to an embodiment of the present invention;
FIG. 17 is a diagram of a simulation model of a 16-element horizontal log periodic dipole linear array according to an embodiment of the present invention;
FIG. 18 is a horizontal plane pattern of a 16-element horizontal log periodic dipole linear array (30 MHz) provided by an embodiment of the present invention;
fig. 19 is a horizontal plane pattern of a 16-element horizontal log periodic dipole linear array (20 MHz) according to an embodiment of the present invention.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The invention will be described below with reference to the accompanying drawings in combination with embodiments.
In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments of the embodiments are all within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the above figures are applicable to distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, it is possible to provide a device for the treatment of a disease. The terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be further noted that the division of the embodiments in the present invention is only for convenience of description, and should not be construed as a specific limitation, and features in the various embodiments may be combined and mutually referenced without contradiction.
As shown in fig. 1, an embodiment of the present invention proposes a method for designing a log periodic antenna linear array in consideration of side lobe levels, including, for example: step S1, a normalized direction function of the main lobe direction of a uniform linear array formed by a plurality of dipole antenna units with logarithmic periods, which is influenced by the beam scanning width of the antenna units, is obtained; step S2, obtaining a corresponding relation between the maximum side lobe level and the beam scanning width according to the normalized direction function, and obtaining a beam width factor corresponding to the target side lobe level according to the corresponding relation; step S3, determining the scale factors and the interval factors of the corresponding antenna units according to the beam width factors; s4, determining antenna array gain according to the scale factor and the interval factor, so as to determine the number of antenna units in the uniform linear array according to the antenna array gain; and step S5, determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating the oscillator parameters of the corresponding antenna units according to the highest working frequency, the scale factors and the interval factors to complete the linear array design.
Specifically, the Log-periodic dipole antenna (Log-Periodic Dipole Antenna, abbreviated as LPDA) is composed of several parallel dipoles, and all the dipole structures are changed according to a certain proportion. Each vibrator is connected to a pair of transmission lines, called aggregate lines, and fed through the aggregate lines. To achieve coaxial cable feeding, a balun is typically used to connect at the center of the shortest vibrator. To achieve the directionality of the radiation (from the longest element to the shortest element), the two arms of two adjacent elements are cross fed. By shorting or adding a matching load to the collection line terminal, terminal reflection can be reduced, thereby improving its low frequency standing wave characteristics.
A schematic structure of the log periodic dipole antenna is shown in fig. 2, and is composed of N parallel elements. The length of the ith vibrator is l i (i=1,., N), (transducer cross-section radius) radius a i It is at a distance R from the (virtual) vertex O i ,d i The distance between the i-th transducer and the i+1-th transducer is shown. The structure of a log periodic dipole antenna generally satisfies the following relationship:
τ, σ, α are referred to as scale factor, spacing factor, and imaginary vertex angle, respectively. The following relationship is satisfied:
the number of elements in a log periodic dipole antenna is related to the operating bandwidth and gain factor of the desired design. The higher the gain the greater the number of required elements and the greater the scaling factor. Typically determined by the following formula:
N＝1+log(B s )/log(1/τ) (5)
B s ＝B(1.1+7.7*(1-τ) 2 cot(α))，B＝f H /f L (6)
f H 、f L representing the highest operating frequency and the lowest operating frequency of the antenna, respectively.
The length of the elements in a log periodic dipole antenna is also related to the operating frequency range of the designed antenna. Engineering uses the cut-off factor K 1 And K 2 To determine the lengths of the longest and shortest elements. Wherein l 1 ＝K 1 λ L ，l N ＝K 2 λ H 。K 1 And K 2 Then the low frequency cut-off coefficient and the high frequency cut-off coefficient are called, the size of which depends on the scale factor and the interval factor, and the specific calculation formula is as follows:
K 1 ＝1.01-0.519τ (7)
K 2 ＝7.1τ 3 -21.3τ 2 +21.98τ-7.3+σ(21.82-66τ+61.12τ 2 -18.29τ 3 ) (8)
in step S1, a uniform linear array composed of M point source antennas is provided, the pitch is d, and the phase difference of feed currents between the antenna units is ζ. According to the antenna array theory, the direction function of the main lobe direction along with the change of the feed phase can be expressed as:
where, ψ=ζ+kdsin θ, ψ is the total phase,
is a wave constant.
When the array elements are fed in phase (ζ=0), a uniform linear array will now form maximum radiation (main lobe) in the 0 ° direction and 180 ° due to structural symmetry. When the feed xi= -kdsin theta is changed 0 At this time, the main lobe points to theta 0 . This is the principle of operation of a phased array antenna, where the maximum radiation direction is changed by changing the feed phase of the antenna elements.
The normalized pattern of the uniform linear array can be drawn according to formula (9). Fig. 2 shows normalized patterns of a 16-element uniform linear array at different scan angles and pitches. It is clear that when the spacing of the array elements is too large, a region of the same size as the main lobe will appear in other directions, which we call grating lobes. The presence of grating lobes means that the antenna radiates energy without concentration, resulting in a decrease in directivity. The occurrence of grating lobes is therefore generally avoided when designing an antenna array. According to the antenna array theory, the condition that grating lobes do not appear in the antenna array directional diagram is as follows:
fig. 3 shows normalized patterns of a 16-element uniform linear array at different scanning angles with different pitches, and the corresponding maximum pitch values at different scanning angles can be calculated according to the formula (10), as shown in the following table 1:
TABLE 1 corresponding maximum value of spacing at different scan angles
| Scan angle (θ) 0 ) | 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 |
| Maximum value of distance (lambda) | 1 | 0.852 | 0.745 | 0.667 | 0.609 | 0.566 | 0.536 | 0.516 | 0.504 | 0.5 |
As can be seen from Table 1, when the scanning angle θ 0 ＝30°，d<0.667λ. From the normalized pattern of the 16-element uniform linear array given in FIG. 3 at different pitches with a different maximum scan angle of 30, it is evident that grating lobes appear when d.gtoreq.0.667λ. It can be seen from fig. 3 that when d=0.6λ, a grating lobe appears in the 150 ° direction, mainly due to the symmetry of the linear array and the non-directivity of the point source antennaResulting in that.
According to the working principle of the log periodic antenna, the log periodic antenna belongs to a medium gain antenna. In order to improve the directivity of the system, an antenna array consisting of log-periodic antennas can be used, and the wave beam of each antenna unit has scanning capability by changing the feed phase of the antenna unit. The uniform linear array is the array type with the simplest feeding and has wide application. For a horizontally erected log periodic dipole antenna, a uniform linear array as shown in fig. 4 is formed as an antenna unit. And the horizontal plane beam scanning capability is realized by changing the feed phase of the antenna unit.
According to the pattern product theorem, the normalized directional function of a uniform linear array consisting of M log periodic dipole antennas can be expressed as:
F(θ)＝F 1 (θ)×F a (θ) (11)
f in the formula 1 (θ) is a direction function of the log periodic dipole antenna, called the self-factor, which is related to the antenna element only. F (F) a And (theta) is a formula (1), called an array factor, which is only related to the form of an array and is not related to the antenna element. F in equation (11) due to the need to achieve beam scanning of the log periodic dipole antenna array in the horizontal plane (called the beamforming plane) 1 (θ) may be selected as a function of the horizontal plane direction.
In particular, for example, using cos m (θ/2) to represent the horizontal plane direction function of the log periodic dipole antenna. m is defined as a beam width factor, the size of which is related to the horizontal plane beam width of the log periodic dipole antenna, and there is a relationship as follows:
wherein 2 theta 0.5E Representing the 3dB beamwidth of a log periodic dipole antenna in the horizontal plane.
Fig. 5 shows a horizontal plane normalization pattern of the log periodic dipole antenna at different values of m. The values of m corresponding to different horizontal plane beamwidths are given in table 2 below, it being found that the larger the beamwidth factor, the narrower the horizontal plane beamwidth.
Table 2m values corresponding to different horizontal plane beamwidths
| |
30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 |
| m | 40.35 | 22.65 | 14.45 | 10.00 | 7.32 | 5.57 | 4.38 | 3.52 | 2.89 | 2.41 |
According to the pattern product theorem, the horizontal plane normalization direction function of the log periodic dipole antenna linear array can be expressed as:
wherein ψ=kd (sinθ -sinθ 0 )。
Normalized patterns of the 16-element log periodic dipole linear array at the beam scanning angle of 30 degrees under different intervals are shown in fig. 5-9.
Fig. 6 shows normalized patterns (d=0.645 λ) at different beamwidths when a linear array beam consisting of 16-element log periodic antennas is scanned to 30 °. Since the distance d=0.645 λ satisfies the requirement that no grating lobe appears at this time, when the log-periodic dipole antenna takes different m values, no grating lobe appears in the pattern of the antenna array. Meanwhile, grating lobes caused by structural symmetry of the linear array are also suppressed due to the directivity of the log-periodic dipole antenna. It has also been found from the figure that the larger the value of m, the narrower the beam width of the log periodic dipole antenna, and the lower the sidelobe level of the antenna array. The side lobe level can be effectively reduced by controlling the beam width of the log periodic dipole antenna unit.
Fig. 7 shows a pattern of a 16-element linear array scanned to 30 ° at an array element pitch d=0.75λ. It can be seen from the figure that 3 grating lobes are present in the array factor since d=0.75λ has exceeded the limit in table 1 that no grating lobes are present. After the direction function of the log-periodic dipole antenna is multiplied by the direction function of the array factor, the grating lobes of the linear array can be well restrained due to the directivity of the log-periodic dipole antenna. And the narrower the beam width of the log periodic dipole antenna is, the better the grating lobe suppression effect is, and the lower the side lobe level is. When m=16, not only there is no grating lobe but also the side lobe level drops to-12.5 dB.
Fig. 8, 9, and 10 show normalized patterns of a 16-element log periodic dipole antenna linear array beam scan to 30 ° for d=0.85λ, d=λ, d=1.15λ, respectively. It can be seen from the figure that as the spacing increases, so does the sidelobe level of the antenna array pattern. It has also been found that when the spacing is large to some extent (e.g., d=1.15λ), the maximum pointing direction of the beam is not in the 30 ° direction, no matter what the beam width factor m of the log periodic dipole antenna element takes. Therefore, for a uniform linear array, the angle corresponding to when grating lobes are generated due to excessive spacing is:
θ s ＝arcsin(sin(θ 0 )-λ/d) (14)
fig. 11 shows the corresponding angles of grating lobes at different pitches. When the array normal direction of the linear array is 0 DEG, the + -theta is usually used 0 Describing its beam scanning range. θ 0 The positive and negative are only representative of the scan direction, and only one direction is typically analyzed due to structural symmetry. For scan angles described herein as positive, θ s Then negative; conversely, when the scan angle is negative, then θ s Then it is positive. As can be seen from fig. 10, as the spacing increases gradually, a uniform linear array will appear with grating lobes positioned gradually closer to 0 °. When |theta s |<θ 0 In time, due to the self-factor direction function (cos m Symmetry of (θ/2)), cos m (θ s /2)>cos m (θ 0 And/2), the values of the matrix factor direction functions are the same (both are 1), and F (theta) can be obtained according to the product theorem of the direction diagram s )>F(θ 0 ) The main lobe is necessarily caused to shift.
Therefore, to avoid the occurrence of main lobe shift and grating lobe, it is required that |θ s |>θ 0 That is, the following conditions should be satisfied:
according to equation (16),can calculate the equivalent theta 0 The uniform linear array of 30 ° log periodic dipole antennas has a spacing constraint d without grating lobes<Lambda. This condition can also be verified from the log periodic dipole linear array normalization pattern at different pitches in fig. 6 to 9.
In addition, log periodic dipole antennas are made up of several elements, with a very wide operating bandwidth being achievable by selecting appropriate scaling and spacing factors. Assume that the operating frequency range of the log periodic dipole antenna is [ f ] L ,f H ]，f L 、f H Representing the lowest operating frequency and the highest operating frequency, respectively. Corresponding lambda L 、λ H Then the wavelengths corresponding to the lowest and highest operating frequencies are represented, respectively.
Further, when the log-periodic dipole antenna with a wider operating frequency range is horizontally erected, the length of the longest element may exceed the operating principle of the log-periodic antenna
Then structural overlap between adjacent elements may occur. To avoid structural overlap of log periodic dipole antennas during array, a spacing d of antenna elements is required>K 1 λ L . The conditions that grating lobes do not appear and the grating lobes do not overlap structurally are combined, and the time interval for forming a uniform linear array by the log-periodic dipole antenna is required to meet the following relation:
further, the limitation of the scanning bandwidth of the log periodic dipole uniform linear array beam which does not have grating lobes and is not overlapped structurally is that:
as can be seen from the above equation (18), when the maximum beam scanning angle θ 0 The larger the selected scaling factor, the larger the achievable bandwidth of the antenna element.
In step S2, the maximum side lobe level is expressed as:
it can be found from the formula that when |θ s |<θ 0 SLL is greater than zero, meaning that the main beam is now offset. When |theta s |>θ 0 SLL is less than zero, when main lobe is pointed to theta 0 . And the side lobe level can be arbitrarily set to select m and the array element spacing, so that the design of the low side lobe log period dipole antenna linear array is realized.
Substituting the normalized direction function into the above arrangement to obtain:
accordingly, the corresponding beam width factor can be calculated by substituting the preset target sidelobe level into the formula (20).
In step S3, the scale factor τ and the spacing factor are obtained from the beam width factor table 3 σ . Preferably, the largest scale factor is selected when there are multiple sets of scale factors and spacing factors that meet the requirements.
TABLE 3 half-power angle of E-plane directional diagram of log periodic vibrator array antenna
In step S4, a gain value G which can be realized by the antenna array is determined according to the scale factor and the interval factor 0 (dB). And then the system determines the number M of antenna array units according to the requirement of the antenna array gain G by the formula (21):
G(dB)＝G 0 (dB)+10*log10(M)+ΔG (21)
where ΔG is the mirror gain of an antenna mounted on the ground, typically about 5-6 dB.
In step S5, the highest operating frequency satisfying the requirement of the log-periodic dipole antenna linear array can be obtained according to the formula (18), and the lowest operating frequency can be calculated according to the beam width factor. Further, the structural parameters such as the number N of the vibrators, the lengths of the vibrators, the spacing between the vibrators and the like can be calculated according to the formulas (1) - (8).
The following examples illustrate specific embodiments and effects:
assuming that the gain of the antenna array to be designed is 17dBi, the maximum scanning angle is theta 0 =30°, maximum side lobe level sll= -5dB. Maximum operating frequency f H =30mhz, the working wavelength is λ H =10m. The following begins the design:
(1) Lambda is set to H ＝10m、θ 0 Take =30° into
The maximum pitch at which grating lobes do not occur can be calculated to be 10m.10m is the upper limit value of the array element spacing, which is chosen here for convenience as d=8m;
(2) Let d=8m, sll= -5dB, and θ 0 The beamwidth factor m=10 can be calculated by substituting 30 ° into equation (19);
(3) Bringing m=10 to equation (12) to calculate the horizontal plane beam width of the log periodic dipole antenna to be 60.3 °, table look-up 3 yields a scaling factor τ=0.925 and a spacing factor σ=0.18;
(4) The gain of the log periodic dipole antenna in free space is about G, which can be obtained by looking up a table based on the scaling factor τ=0.925 and the spacing factor σ=0.18 0 ≈9dBi；
(5) The number of antenna units can be calculated to be 8 according to the formula (20);
(8) According to formula (17)Can be obtained by
Bringing τ=0.92 into the obtainable λ L <15.02m, lambda is taken to ensure that the structures do not overlap L =15m, so that the lowest operating frequency can be calculated to be about f L ＝20MHz；
(9) Will f L 、f H Bringing τ, σ into equations (5) and (6) can calculate the length of the transducers and their distance from each other, see table 4.
Table 4 log periodic dipole antenna structure
| Vibrator numbering | Length of vibrator | Distance between |
| 1 | 7.95 | 0.00 |
| 2 | 7.35 | 2.86 |
| 3 | 6.80 | 2.65 |
| 4 | 6.29 | 2.45 |
| 5 | 5.82 | 2.26 |
| 6 | 5.38 | 2.09 |
| 7 | 4.98 | 1.94 |
| 8 | 4.61 | 1.79 |
| 9 | 4.26 | 1.66 |
| 10 | 3.94 | 1.53 |
| 11 | 3.65 | 1.42 |
| 12 | 3.37 | 1.31 |
| 13 | 3.12 | |
| 14 | 2.89 |
In addition, a log periodic dipole antenna simulation model is built from the structural parameters in table 4, for example using FEKO software, as shown in fig. 12. The antenna wire is made to be an ideal conductor. The simulation frequency is 20 MHz-30 MHz, and the frequency interval is 0.5MHz.
Fig. 13 to 15 show the gain, standing wave ratio and horizontal plane beam width curves of the log-periodic dipole antenna in free space with frequency, respectively. As can be seen from fig. 13, the gain of the log-periodic dipole antenna designed according to the previous design process is about 9dBi in the whole frequency band, and the gain is very consistent with the theoretical estimation. It can be seen from the standing wave curve in fig. 14 that the standing wave in the entire frequency band is less than 1.5. As can be seen from the law of the beam width variation with frequency in fig. 15, the horizontal plane beam width of the entire frequency band is uniform by about 60 °.
Fig. 16 shows a comparison of the horizontal plane pattern obtained by beam width simulation and the horizontal plane pattern obtained by FEKO simulation calculation, and it can be seen from the figure that the difference between the two is small.
The gain curve of the front unit antenna shows that the gain of the designed log-periodic dipole antenna is about 9dBi, which is equivalent to a theoretical estimated value. A linear array as in fig. 17 was established using 16 pairs of log periodic dipole antenna spacings 8m of the previous design.
Fig. 18 and 19 show horizontal plane patterns of beam sweeps of the design frequency band, maximum frequency 30MHz and minimum operating frequency 20MHz, to 0 °, 15 °, 30 °, respectively.
From FIG. 18, it can be seen that the linear array has gains of 20.4dBi, 20.1dBi and 18.6dBi at a working frequency of 30MHz, the relative sidelobe levels are-13.7 dB, -13.2dB and-5 dB, respectively, and the sidelobe generation angles are 48 degrees, and from FIG. 19, it can be seen that the linear array has gains of 18.9dBi, 18.7dBi and 18.1dBi at a working frequency of 20MHz, and the relative sidelobe levels are-13.6 dB, -12.7dB and-12.1 dB, respectively.
The design method of the log-periodic dipole antenna linear array provided by the patent is verified through the simulation cases, and the method can effectively control the side lobe level.
In summary, according to the log periodic antenna linear array design method considering the side lobe level provided by the embodiment of the invention, the side lobe level of the antenna unit and the beam scanning bandwidth are analyzed, so that the side lobe level meeting the requirement can be realized by controlling the beam scanning bandwidth, and the beam scanning bandwidth can be realized by designing the structural parameters of the log periodic dipole antenna linear array, thereby avoiding additional increase of a control device and calculation complexity.
In addition, the second embodiment of the present invention further provides a log periodic antenna linear array design device considering the side lobe level, for example, including: the device comprises a normalized direction function acquisition module, a beam width factor acquisition module, a proportion/interval factor determination module, an antenna unit number determination module and a vibrator parameter calculation module.
The normalization direction function acquisition module is used for acquiring a normalization direction function of which the main lobe direction of a uniform linear array formed by a plurality of log-periodic dipole antenna units is influenced by the beam scanning width of the antenna units. The beam width factor obtaining module is used for obtaining the corresponding relation between the maximum side lobe level and the beam scanning width according to the normalized direction function, and obtaining the beam width factor corresponding to the target side lobe level according to the corresponding relation. The proportion/interval factor determining module is used for determining proportion factors and interval factors of corresponding antenna units according to the beam width factors. The antenna element number determining module is used for determining antenna array gain according to the scale factor and the interval factor so as to determine the number of antenna elements in the uniform linear array according to the antenna array gain. The oscillator parameter calculation module is used for determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating to obtain the oscillator parameters of the corresponding antenna units according to the highest working frequency, the scale factors and the interval factors, so that the linear array design is completed.
The method for designing the log periodic antenna linear array taking the side lobe level into consideration, which is realized by the device for designing the log periodic antenna linear array taking the side lobe level into consideration according to the second embodiment of the present invention, is as described in the first embodiment, and therefore will not be described in detail herein. Optionally, each module in the second embodiment and the other operations or functions described above are respectively for implementing the method described in the first embodiment, and the beneficial effects of this embodiment are the same as those of the foregoing first embodiment, which are not described herein for brevity.
The third embodiment of the present invention also proposes an electronic device, for example, including: a memory and one or more processors coupled to the memory. The memory stores a computer program for execution by the processor to implement a log periodic antenna array design taking into account side lobe levels as described in the first embodiment. The specific method for designing the log-periodic antenna linear array with consideration of the side lobe level can refer to the method described in the first embodiment, and is not described herein for brevity.
The third embodiment of the present invention also proposes a computer-readable storage medium, which is a nonvolatile memory and stores computer-readable instructions that, when executed by one or more processors, for example, cause the one or more processors to execute the log periodic antenna linear array design method taking into account the sidelobe level described in the foregoing first embodiment. The specific method may refer to the method described in the first embodiment, which is not described herein for brevity, and the beneficial effects of the computer readable storage medium provided in this embodiment are the same as those of the log periodic antenna linear array design method provided in the first embodiment that considers the sidelobe level.
In addition, it should be understood that the foregoing embodiments are merely exemplary illustrations of the present invention, and the technical solutions of the embodiments may be arbitrarily combined and matched without conflict in technical features, contradiction in structure, and departure from the purpose of the present invention.
In the several embodiments provided herein, it should be understood that the disclosed systems, devices, and/or methods may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and the division of the units/modules is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or modules may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units/modules described as separate units may or may not be physically separate, and units/modules may or may not be physically units, may be located in one place, or may be distributed on multiple network units. Some or all of the units/modules may be selected according to actual needs to achieve the purpose of the embodiment.
In addition, each functional unit/module in the embodiments of the present invention may be integrated in one processing unit/module, or each unit/module may exist alone physically, or two or more units/modules may be integrated in one unit/module. The integrated units/modules may be implemented in hardware or in hardware plus software functional units/modules.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A design method of a log periodic antenna linear array considering side lobe level is characterized by comprising the following steps:
acquiring a normalized direction function of the main lobe direction of a uniform linear array formed by a plurality of logarithmic period dipole antenna units, wherein the normalized direction function is influenced by the beam scanning width of the antenna units;
obtaining a corresponding relation between the maximum side lobe level and the beam scanning width according to the normalized direction function, and obtaining a beam width factor corresponding to the target side lobe level according to the corresponding relation;
determining a scale factor and a spacing factor of the corresponding antenna unit according to the beam width factor;
determining antenna array gain according to the scale factor and the interval factor, so as to determine the number of antenna units in the uniform linear array according to the antenna array gain; and
and determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating oscillator parameters of corresponding antenna units according to the highest working frequency, the scale factors and the interval factors to complete the linear array design.
2. The method for designing a log periodic antenna linear array taking into account side lobe levels according to claim 1, wherein the normalized direction function is:
where M is the number of antenna elements, ψ=kd (sin θ -sin θ) 0 ) M is defined as a beam width factor; wherein (1)>
Is the wave constant, d is the antenna unit spacing, theta is the included angle between the main lobe and the normal direction, theta 0 Is the main lobe direction.
3. The method for designing a log periodic antenna linear array taking into account side lobe levels according to claim 2, wherein the obtaining the correspondence between the maximum side lobe level and the beam width factor according to the normalized direction function includes:
the side lobe level is expressed as:
wherein θ 0 Representing the beam scanning direction, θ s Representing the grating lobe angle.
4. The method for designing a log periodic antenna linear array taking into account side lobe levels according to claim 3, wherein said obtaining the beam width factor corresponding to the target side lobe level according to the correspondence relation comprises:
the beam width factor is calculated as:
5. the method for designing a log periodic linear array of antennas taking into account side lobe levels according to claim 1, wherein said determining the number of antenna elements in the uniform linear array according to the antenna array gain comprises:
the antenna array gain is expressed as: g (dB) =g 0 (dB) +10log 10 (M) +Δg, thereby calculating the number of antenna elements M; wherein G is 0 (dB) is the antenna element gain in free space and Δg is the mirror gain of the antenna element.
6. The method for designing a linear array of log periodic antennas taking into account side lobe levels as defined in claim 4, wherein said determining the lowest operating frequency of said uniform linear array according to said normalized direction function comprises:
obtaining an antenna unit interval range which does not have grating lobes and is not overlapped among the antenna units of the uniform linear array according to the normalization direction function;
and determining a corresponding beam scanning bandwidth according to the antenna unit interval range so as to determine the lowest working frequency according to the beam scanning bandwidth and the highest working frequency.
7. The method for designing a log periodic antenna linear array taking into account side lobe levels according to claim 6, wherein said calculating obtains oscillator parameters corresponding to antenna elements, comprising:
calculating to obtain the number of vibrators according to the highest working frequency and the lowest working frequency;
and calculating the length of the longest oscillator and the length of the shortest oscillator according to the scale factors and the interval factors, and calculating the distance between every two adjacent oscillators according to an antenna theory.
8. A log periodic antenna linear array design device considering side lobe level, comprising:
the normalized direction function acquisition module is used for acquiring a normalized direction function of which the main lobe direction of a uniform linear array formed by a plurality of dipole antenna units with logarithmic periods is influenced by the beam scanning width of the antenna units;
the beam width factor obtaining module is used for obtaining the corresponding relation between the maximum sidelobe level and the beam scanning width according to the normalized direction function and obtaining the beam width factor corresponding to the target sidelobe level according to the corresponding relation;
a scale/interval factor determining module, configured to determine a scale factor and an interval factor of a corresponding antenna unit according to the beam width factor;
the antenna unit number determining module is used for determining antenna array gain according to the scale factor and the interval factor so as to determine the number of antenna units in the uniform linear array according to the antenna array gain; and
and the oscillator parameter calculation module is used for determining the lowest working frequency of the uniform linear array according to the normalized direction function, and calculating the oscillator parameters of the corresponding antenna units according to the highest working frequency, the scale factors and the interval factors to complete the linear array design.
9. An electronic device, comprising: a memory and one or more processors coupled to the memory, the memory storing a computer program, the processor configured to execute the computer program to implement the log periodic antenna design method of any of the preceding claims that considers sidelobe levels.
10. A computer-readable storage medium storing computer-executable instructions for performing the log periodic antenna design method taking into account sidelobe levels as claimed in any of the preceding claims.
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