A method for realizing shortwave broadband phased array antenna based on log-periodic antenna

Abstract

The present invention discloses a method for realizing a shortwave broadband phased array antenna based on a logarithmic periodic antenna, comprising: arranging a plurality of logarithmic periodic dipole antennas in a straight line at uniform intervals to obtain a logarithmic periodic dipole antenna linear array; in the logarithmic periodic dipole antenna linear array, at least reducing the length of the longest oscillator in each logarithmic periodic dipole antenna projected in the direction of the collective line. The present invention improves the beam scanning bandwidth of the logarithmic periodic dipole antenna linear array by reducing the lateral length of the longest oscillator in the logarithmic periodic dipole antenna.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and more specifically, to a method for realizing a shortwave broadband phased array antenna based on a logarithmic periodic antenna. Background Art

[0002] Shortwave refers to electromagnetic waves with a frequency range of 3 to 30 MHz. Since it can be transmitted over long distances through reflection from the ionosphere, it is widely used for long-distance communications and target detection. However, due to changes in the ionosphere, shortwave radio systems usually need to use broadband antennas to adapt to changes in the ionosphere in order to achieve communications or target detection. After years of development, many researchers have adopted various means to achieve broadband shortwave antennas. Among them, the log-periodic dipole antenna is an influential broadband antenna, and it has a very wide range of applications in all radio frequency bands.

[0003] A single shortwave log-periodic dipole antenna can cover the entire shortwave frequency band by selecting appropriate scaling factors and spacing factors. It usually has a horizontal beam width of several tens of degrees to cover a certain sector. Although the log-periodic dipole antenna is composed of multiple oscillators, not all oscillators contribute to radiation at any operating frequency. Only some oscillators in the radiation zone (the area where the arrays with a length of about half the operating wavelength are located) play a major role in radiation, so its directivity cannot be very strong. The directivity coefficient or antenna gain is usually only about 10dBi, which belongs to the category of medium-gain antennas. When the log-periodic dipole antenna is fixed, its beam coverage range is also fixed. In order to achieve longer-distance communication and detection of targets in different directions, phased array technology is usually required.

[0004] However, when using phased array technology, how to form an array of conventional log-periodic dipole antennas, how to expand the bandwidth after the array is formed without the appearance of grating lobes and without overlapping of array elements, and how to make necessary limitations on various antenna structure parameters after the array are all technical problems that need to be solved urgently. Summary of the invention

[0005] In response to at least one of the technical problems faced by the above-mentioned prior art, the present invention proposes a method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna, so as to solve the technical problem of how to array conventional log-periodic dipole antennas and expand the beam scanning bandwidth without the occurrence of grating lobes and without overlap of array elements.

[0006] To achieve the above object, the present invention provides a method for realizing a shortwave broadband phased array antenna based on a logarithmic periodic antenna, comprising:

[0007] Arrange a plurality of logarithmic periodic dipole antennas in a straight line at even intervals to obtain a logarithmic periodic dipole antenna linear array;

[0008] In the linear array of logarithmic periodic dipole antennas, at least the length of the projection of the longest oscillator in each logarithmic periodic dipole antenna in the direction of the collective line is reduced.

[0009] Further, reducing the length of the longest oscillator in the logarithmic periodic dipole antenna projected in the direction of the collective line specifically includes:

[0010] The two arms of the longest oscillator in the log-periodic dipole antenna are bent in the same normal direction of the collective line, and it is ensured that the length of the two arms of the longest oscillator after bending in the direction of the collective line is not less than the length of the projection of any other oscillator in the log-periodic dipole antenna in the direction of the collective line, so as to obtain a V-shaped oscillator log-periodic antenna linear array.

[0011] Furthermore, on the basis of bending the two arms of the longest oscillator in the log-periodic dipole antenna toward the same normal direction where the collective line is located, a section of top load is bent at the ends of the two arms toward the same normal direction respectively to obtain a VT-type oscillator log-periodic antenna linear array.

[0012] Furthermore, the constraint condition expression that the linear array of logarithmic periodic dipole antennas does not have grating lobes and the array elements do not overlap in structure is:

[0013]

[0014] Among them, K 1 =1.01-0.519τ, K 1 is the low-frequency cutoff coefficient, τ is the length change proportional factor, θ 0 is the maximum scanning angle, M is the number of array elements, B c is the beam scanning bandwidth of the linear array of log-periodic dipole antennas.

[0015] Furthermore, the constraint condition expression that the VT-type dipole log-periodic antenna linear array does not have grating lobes and the array elements do not overlap in structure is:

[0016]

[0017] Among them, Θ 1 is the angle between the two arms of the longest oscillator in the logarithmic periodic dipole antenna and the normal after being bent in the same normal direction where the collection line is located, k is the top load length ratio coefficient, B VT is the beam scanning bandwidth of the VT-type dipole log-periodic antenna linear array.

[0018] Furthermore, the beam scanning bandwidth of the VT-type dipole logarithmic periodic antenna linear array is the beam scanning bandwidth of the logarithmic periodic dipole antenna linear array. times.

[0019] Furthermore, the constraint condition expression for ensuring that the length of the two arms of the longest oscillator after bending in the direction of the collective line is not less than the length of the projection of any other oscillator in the logarithmic periodic dipole antenna in the direction of the collective line is:

[0020]

[0021] Among them, τ Θ is the bending angle change proportional factor, Θ i is the angle between the i-th oscillator and the collection line starting from the end of the longest oscillator.

[0022] Furthermore, the constraint condition expression of the top load length ratio coefficient k is:

[0023]

[0024] Furthermore, the constraint condition expression for preventing the two arms of the oscillator from bending in the opposite direction in the same normal direction of the collection line is:

[0025]

[0026] Among them, N V is the number of vibrators that need to be bent, and floor is the rounding function.

[0027] Furthermore, the maximum bending angle change proportional factor when all vibrators are bent is calculated as follows:

[0028]

[0029] Among them, τ Θ_max is the proportional factor of the maximum bending angle change when all oscillators are bent.

[0030] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0031] (1) The present invention improves the beam scanning bandwidth of the linear array of logarithmic periodic dipole antennas by reducing the lateral length of the longest oscillator in the logarithmic periodic dipole antenna.

[0032] (2) The present invention proposes a VT-type dipole log-periodic antenna linear array array method to expand the beam scanning bandwidth of the log-periodic dipole antenna linear array without the occurrence of grating lobes and without overlap of array elements.

[0033] (3) The present invention redefines the structural parameters of the VT-type vibrator log-periodic antenna linear array, introduces a bending angle change proportional factor, analyzes the working bandwidth of the VT-type vibrator log-periodic antenna linear array under different structural parameters, and makes necessary restrictions on various antenna structural parameters, thereby filling the research gap in this technical field. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a structural schematic diagram of a logarithmic periodic dipole antenna in the prior art;

[0036] Figure 2 A schematic diagram of the structure of a uniform linear array composed of logarithmic periodic dipole antennas provided in an embodiment of the present invention;

[0037] Figure 3 A functional relationship diagram of beam scanning bandwidth-maximum scanning angle provided in an embodiment of the present invention (the scale factor is 0.86);

[0038] Figure 4 A functional relationship diagram of beam scanning bandwidth-length change proportional factor provided in an embodiment of the present invention (the number of array elements is 16);

[0039] Figure 5 A schematic diagram of the evolution of bending a linear dipole of a conventional logarithmic periodic dipole antenna into a VT-type dipole provided in an embodiment of the present invention;

[0040] Figure 6 A schematic diagram of the structure of a VT-type dipole log-periodic antenna provided in an embodiment of the present invention;

[0041] Figure 7 A schematic diagram of the structure of a uniform linear array composed of a VT-type dipole log-periodic antenna provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] The terms "including" or "having" and any variations thereof in the specification, claims or drawings of the present application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products or devices.

[0044] There are many ways to form an antenna array. However, for several short-wave log-periodic dipole antennas, the simplest and most effective way is to arrange them at equal intervals into a uniform linear array. However, for a uniform linear array, the selection of the array element spacing is very important. Too large a spacing will lead to the appearance of grating lobes, and too small a spacing will lead to serious coupling between array elements, thereby reducing the broadband characteristics of the antenna array. From the design principle of the log-periodic dipole antenna, it can be seen that it is composed of several linear oscillators in a certain proportion. The longest oscillator is usually half of the working wavelength corresponding to the lowest operating frequency of the log-periodic dipole antenna, and the shortest oscillator is usually half of the working wavelength corresponding to its highest operating frequency.

[0045] In order to avoid the appearance of grating lobes, the spacing between array elements in a linear array is usually half the wavelength corresponding to the highest operating frequency. However, for a linear array composed of horizontal logarithmic periodic dipole antennas with a wide bandwidth, if they are arranged according to this spacing, the structures between the array elements may overlap. Therefore, a linear array composed of horizontally erected short-wave logarithmic periodic dipole antennas will inevitably have bandwidth limitations.

[0046] This paper analyzes in detail the bandwidth limitation of a uniform linear array composed of horizontally mounted logarithmic periodic dipole antennas, and proposes a VT-LPDA unit to improve the beam scanning bandwidth. The structural parameters of the VT-type LPDA are redefined, and the bending angle change proportional factor is introduced. The working bandwidth of the VT-type LPDA under different structural parameters is analyzed, and necessary restrictions are made on various antenna structural parameters, thus filling the research gap in this technical field.

[0047] like Figure 1 As shown in the figure, the Log-Periodic Dipole Antenna (LPDA) is composed of several parallel symmetrical oscillators, and the structure of each pair of oscillators changes according to a certain ratio. Each oscillator is connected to a pair of two-wire transmission lines, called a collection line, and is fed through the collection line. A balanced-unbalanced transformer is usually used to realize the feeding of the symmetrical oscillator unit with a coaxial cable. The feed source is connected to one end of the shortest oscillator, and the two adjacent oscillators are cross-fed. By short-circuiting the line terminal of the collection line or adding a matching load, the terminal reflection can be reduced, thereby improving its low-frequency standing wave characteristics.

[0048] The structure of the log-periodic dipole antenna is shown below: Figure 1 As shown, it consists of N parallel symmetrical oscillators. The total length of the i-th oscillator is l i (i=1,...,N), the radius of the vibrator cross section is a i , its distance from the virtual vertex O is R i ,d i Represents the distance between the ith oscillator and the i+1th oscillator. Usually the structure of the logarithmic periodic dipole antenna satisfies the following relationship:

[0049]

[0050]

[0051]

[0052] τ, σ and α are usually called length change proportional factor, spacing factor and virtual vertex angle. They satisfy the following relationship:

[0053]

[0054] Generally, the number of oscillators N in a log-periodic dipole antenna is related to the required working bandwidth and gain factor. The higher the gain, the more oscillators are required, and the larger the length change proportional factor is. It is usually determined by the following formula:

[0055] N=1+log(B(1.1+7.7*(1-τ) 2 cot(α))) / log(1 / τ) (5)

[0056]

[0057] f H 、f L represent the highest and lowest operating frequencies of the log-periodic dipole antenna, respectively, and λ H , L They represent the wavelengths corresponding to the highest operating frequency and the lowest operating frequency respectively, and B represents the beam scanning bandwidth of the antenna array under the premise of avoiding the appearance of grating lobes and avoiding structural overlap in the array formation process, which is referred to as the beam scanning bandwidth for short.

[0058] The length of the dipole in the logarithmic periodic dipole antenna is also related to the operating frequency range of the designed antenna. The truncation factor K is often used in engineering. 1 and K 2 To determine the length of the longest and shortest oscillators. Among them, the length of the longest oscillator is l max =K 1 λ L, the length of the shortest oscillator is l min =K 2 λ H . K 1 and K 2 They are respectively called the low-frequency truncation coefficient and the high-frequency truncation coefficient, and their sizes depend on the length change proportional factor and the interval factor. The specific calculation formula is as follows.

[0059] K 1 =1.01-0.519τ (7)

[0060] K 2 =7.1τ 3 -21.3τ 2 +21.98τ-7.3+σ(21.82-66τ+61.12τ 2 -18.29τ 3 ) (8)

[0061] Since the log-periodic dipole antenna has a wide working bandwidth, it is usually used in the shortwave band for medium and long-distance communications. It can obtain a wide working bandwidth through a plurality of symmetrical oscillator structures, but for a certain working frequency, only part of the oscillators near the resonant length play a radiating role. Therefore, the log-periodic dipole antenna is a medium-gain antenna. In order to improve the directivity of the antenna system, this embodiment uses log-periodic dipole antennas to form a linear array. At the same time, by changing the phase of the antenna unit, a certain beam scanning capability can be obtained. However, since the spacing between antenna array elements has a great influence on the array performance, too large a spacing will lead to the appearance of grating lobes, while too small a spacing will lead to insufficient directivity and relatively strong mutual coupling, thereby causing the impedance characteristics to deteriorate. In other words, the bandwidth of the antenna array with scanning capability composed of log-periodic dipole antennas will be greatly limited, especially when it is installed horizontally.

[0062] like Figure 2 As shown in the figure, a uniform linear array is formed by M (M is the number of array elements) logarithmic periodic dipole antennas spaced d apart. Assume that the operating frequency range of the logarithmic periodic dipole antenna is [f L ,f H ],f L and f H is the minimum operating frequency and the maximum operating frequency. For phased array antennas, the suppression of grating lobes must be considered during the design process. Usually, in order to avoid the appearance of grating lobes during beam scanning, the spacing of antenna units must satisfy the following relationship:

[0063]

[0064] Among them, θ 0 is the maximum scanning angle, such as Figure 2shown.

[0065] For a linear array composed of a horizontally erected short-wave logarithmic periodic dipole array, since the antenna unit needs to achieve a wider working bandwidth, the longest dipole will be relatively long. Therefore, in the process of forming the array, the structural overlap between the logarithmic periodic antennas should be avoided. According to the previous introduction, the longest dipole and the shortest dipole are equal to K 1 λ L and K 2 λ H In order to avoid structural overlap during the array formation process, the spacing between antenna elements should be greater than K 1 λ L .

[0066] In order to make the working bandwidth of the antenna array wide enough, the spacing between antenna elements should be large enough. However, too large a spacing will cause grating lobes to appear at the high end of the frequency. Combined with formula (9), in order to avoid the appearance of grating lobes and avoid structural overlap during the array formation process, the spacing between antenna elements should satisfy the following relationship:

[0067]

[0068] Substituting the low-frequency cutoff coefficient formula (7) into formula (10), we can further deduce that the uniform linear array composed of logarithmic periodic dipole antennas has a maximum scanning angle of θ 0 In the case of no grating lobes and no overlap in structure, the beam scanning bandwidth of the antenna satisfies the following relationship:

[0069]

[0070] Among them, B c is the beam scanning bandwidth of the linear array of log-periodic dipole antennas.

[0071] Figure 3 and Figure 4 The maximum beam scanning bandwidth achieved by a uniform linear array composed of horizontal log-periodic antennas is given as a function of the number of array elements, the maximum scanning angle, and the length change proportional factor. The directivity of a single log-periodic antenna mainly depends on the length change proportional factor. The larger the length change proportional factor, the more oscillators there are, the more oscillators contribute to the radiation area, and the stronger the directivity. Usually, according to different system requirements, the value range of the proportional factor is [0.8, 0.96]. From Figure 3 It can be found that the beam scanning bandwidth of the uniform linear array composed of logarithmic periodic dipole antennas decreases rapidly with the increase of the maximum scanning angle. Increasing the number of array elements can increase the beam scanning bandwidth to a certain extent. Figure 4It can be found that when the number of array elements is fixed (M=16), the beam scanning bandwidth of the uniform linear array increases with the increase of the length change proportional factor, and the smaller the maximum scanning angle, the more obvious the effect of increasing the length change proportional factor on improving the beam scanning bandwidth.

[0072] Through the above analysis, it is found that the beam scanning bandwidth at a certain scanning angle can be increased by changing the number of array elements and the length proportional factor. Nevertheless, the maximum working bandwidth of the linear array composed of horizontally mounted logarithmic periodic dipole antennas will not exceed 2 from the perspective of no grating lobes. The working bandwidth of conventional logarithmic periodic dipole antenna units will mostly exceed 2:1, so the linear array cannot better exert its ultra-wideband characteristics.

[0073] From the above analysis, we can see that the fundamental limitation of the narrow beam scanning bandwidth of the linear array composed of horizontal logarithmic periodic dipole antennas lies in the lateral length of the longest oscillator, that is, the length of the projection of the longest oscillator in the direction of the collection line, that is, Figure 2 The longest oscillator K 1 λ L The length of the orthographic projection on the vertical plane of the collection line. Therefore, reducing the lateral length of the longest oscillator becomes the only means to expand the beam scanning bandwidth of the linear array composed of horizontal logarithmic periodic dipole antennas. In order to ensure that the lowest resonant frequency remains unchanged and the actual physical length of the longest oscillator remains constant, this embodiment proposes to change the conventional linear symmetrical oscillator unit (i.e., straight dipole) into a VT-type oscillator unit (VT-dipole), such as Figure 5 VT-dipole can be obtained by bending the two arms of a conventional dipole oscillator toward the normal direction of the oscillator and adding a certain length of top load to both ends of the oscillator. The total length of VT-dipole is still K 1 λ L For ease of analysis, assume that the top load length of the VT-dipole is kλ L , k is the top load length ratio coefficient, Θ 1 is the angle between the longest vibrator bending part and the vibrator normal. At this time, the lateral length of the longest vibrator is (K 1 λ L -2kλ L )sinΘ 1 .

[0074] According to the previous analysis, in order to make the uniform linear array composed of M logarithmic periodic antennas based on VT-type oscillator units have a maximum scanning angle of θ 0 There should be no grating lobes and the array elements should not overlap in structure. The spacing between the array elements should satisfy the following equation:

[0075]

[0076] Furthermore, a uniform linear array composed of M logarithmic periodic antennas based on VT-type dipole units (such as Figure 7 As shown) at the maximum scanning angle θ 0 The beam scanning bandwidth when there is no grating lobe and the array elements do not overlap in structure satisfies the following relationship:

[0077]

[0078] Among them, B VT is the beam scanning bandwidth of the VT-type dipole log-periodic antenna linear array. From formula (13), it can be found that when the maximum scanning angle θ of the phased array antenna is 0 When the number of array elements M is fixed and determined, the bending angle θ of the longest oscillator in the logarithmic periodic antenna based on the VT-type oscillator unit can be 1 The beam scanning bandwidth of the linear array of antennas can be improved by using the top load length ratio coefficient k. The beam scanning bandwidth of the linear array of logarithmic periodic antennas with the oscillator unit improved to VT type can theoretically be increased to the beam scanning bandwidth of the linear array composed of conventional logarithmic periodic dipole antennas. times, which can actually be obtained by dividing the right side of formula (13) by the right side of formula (11) For the convenience of description, the logarithmic periodic antenna based on the VT-type dipole unit is represented by VT-LPDA.

[0079] The above analysis of the LPDA beam scanning bandwidth is based on the perspective that no grating lobes appear during the antenna array scanning process, and a VT-LPDA antenna unit is proposed by bending and adding top loads. Through analysis, it is found that the uniform linear array composed of M VT-LPDA antenna units has a maximum scanning angle of θ. 0 When the beam scanning bandwidth is achievable, it will theoretically be higher than that of a linear array composed of conventional log-periodic antennas. Obviously, the improvement of scanning bandwidth obtained by VT-LPDA antenna unit is similar to Θ 1 , k have a great relationship, different Θ 1 , k will obtain different beam scanning bandwidths. The above only conducts theoretical analysis from the perspective of beam scanning bandwidth, however 1 The change of , k will lead to the change of antenna structure, which will inevitably cause the change of antenna impedance bandwidth or gain. Therefore, it is necessary to make further parameter description of VT-LPDA antenna unit.

[0080] According to the working principle of the log-periodic antenna, the main reason why the log-periodic antenna can have a wide working bandwidth is that the structural parameters all meet the change of the length change proportional factor. In order to ensure the proportional change of the log-periodic antenna structure while reducing the lateral size, all the oscillators or at least one or more oscillators that are prone to structural overlap are bent. Define the angle between the i-th oscillator and the collection line as Θ i , and the angles between adjacent oscillators and the collection line also satisfy the structural proportional changes. The numbers are counted from the longest oscillator, l i is the total length of the main oscillator, S i is the length of the additional vibrator (top load), such as Figure 6 As shown, the structural proportional relationship is specifically

[0081] In the process of analysis, in order not to change the length of the vibrator, the bending length is expressed by a proportional coefficient, so that the bending angle of the longest vibrator and the top load satisfy the following relationship:

[0082] d / sinΘ 1 +2kλ L =K 1 λ L (14)

[0083] That is to say, the total physical length and lateral size of the longest oscillator are kept constant. The total length is the longest working wavelength multiplied by the low-frequency cutoff coefficient, and the lateral size d is the maximum spacing without grating lobes in the array formation process. Based on the above relationship, the relationship between the bending angle of the longest oscillator and the additional branches can be obtained:

[0084]

[0085] From the above formula, we can find that the introduction of additional branches can effectively reduce the degree of bending of the oscillator toward the collection line. The longer the additional branches are, the larger the angle between the longest oscillator and the collection line is. When the length of the additional branches is small, the θ of the first oscillator is 1 will be smaller, so that the longest oscillator of the first root does not overlap in structure. In the extreme case of k = 0, that is, when there is no top load, the VT-type oscillator unit is actually a V-type oscillator unit. 1 will be the smallest. However, according to the definition of the physical structure of VT-LPDA, the angle θ between the second oscillator and the collective line 2 All of them change according to the proportional factor. When the working bandwidth is wide, the proportional change of the angle cannot guarantee that the second oscillator will not overlap. To avoid the above situation, there are two ways to deal with it. One is to make the bending angle of all oscillators the same (that is, Θ i =Θ i+1), the other is to define a bending angle change proportional factor τ for the bending angle change of each oscillator Θ .

[0086]

[0087] In order to prevent similar situations from happening, the following relationship should be satisfied between adjacent bending angles:

[0088] l i+1 sin(θ i / τ Θ )≤l i sin(θ i ) (17)

[0089] Formula (17) actually means that the length of the two arms of the longest oscillator after bending in the direction of the collection line is not less than the length of any other oscillator in the logarithmic periodic dipole antenna in the direction of the collection line. Obviously, Further introduction Therefore, when the bending angle of the longest oscillator is 1 After the length change proportional factor τ is determined, the bending angle Θ can be calculated according to the above formula i The changing scale factor can solve the problem of overlapping during the array formation process.

[0090] Through analysis, bending the oscillator and adding additional branches at both ends can effectively expand the working bandwidth of the horizontal logarithmic periodic antenna to form a linear array. It can be concluded that the larger k is, the larger the extended bandwidth is. When in the extreme case of k = 0, that is, when there is no top load, the above multiple becomes Therefore, the ratio (k>0, that is, there must be a top load), so the introduction of the VT type vibrator unit will inevitably increase the beam scanning bandwidth.

[0091] According to formula (15), It can be further deduced that:

[0092]

[0093] Available sin(θ 1 )≤τ, from formula (15) we can further obtain:

[0094]

[0095] We can further obtain:

[0096]

[0097] Substituting the right side of formula (9) into formula (20), we can obtain

[0098]

[0099] From formula (21), it can be found that the length proportional coefficient of the additional branch is within a certain range. When the maximum scanning angle and the number of array elements are fixed, the range is related to the beam scanning bandwidth and the length variation proportional factor of the VT-type dipole logarithmic periodic antenna linear array. That is to say, when the number of antenna elements M and the maximum scanning angle θ of the antenna array are fixed, the length proportional coefficient of the additional branch is within a certain range. 0 After being fixed, the value range of the additional branch length proportional coefficient k can be determined according to the beam scanning bandwidth and the length change proportional factor of the antenna unit.

[0100] The angle between the transmission line and the oscillator is used to define and calculate the oscillator. When the bending angle changes by a proportional factor τ Θ In order to ensure that there are no grating lobes and the array elements do not overlap, when the angle changes too much to a certain extent, the angle between the oscillator and the transmission line will be greater than 90°. At this time, the oscillator will bend in the opposite direction. To avoid this situation, the number of oscillators that need to be bent can be calculated according to different bending angle change proportional factors:

[0101]

[0102] Among them, N V is the number of vibrators that need to be bent, and floor is the rounding function. From formula (22), it can be found that the smaller the bending angle change proportional factor, the more vibrators need to be bent. Conversely, the larger the bending angle change proportional factor, the fewer vibrators need to be bent. When all vibrators are bent, the maximum bending angle change proportional factor under different loading lengths can be calculated.

[0103]

[0104] Among them, τ Θ_max is the maximum bending angle change proportional factor when all vibrators are bent, that is, the maximum value of the bending angle change proportional factors when all vibrators are bent. Through the above analysis, the number of vibrators that need to be bent under the maximum bending angle change proportional factor and different bending angle change proportional factors can be determined.

[0105] Those skilled in the art will appreciate that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, and all of these combinations and / or combinations fall within the scope of the present disclosure.

[0106] Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims

1. A method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna. It is characterized in that include: Arrange a plurality of logarithmic periodic dipole antennas in a straight line at even intervals to obtain a logarithmic periodic dipole antenna linear array; In the linear array of logarithmic periodic dipole antennas, at least the length of the projection of the longest oscillator in each logarithmic periodic dipole antenna in the direction of the collective line is reduced; Reducing the length of the longest oscillator in the logarithmic periodic dipole antenna projected in the direction of the collective line specifically includes: The two arms of the longest vibrator in the log-periodic dipole antenna are bent in the same normal direction where the collective line is located, and it is ensured that the length of the two arms of the longest vibrator after bending in the direction of the collective line is not less than the length of the other vibrators in the log-periodic dipole antenna in the direction of the collective line, so as to obtain a V-type vibrator log-periodic antenna linear array; on the basis of bending the two arms of the longest vibrator in the log-periodic dipole antenna in the same normal direction where the collective line is located, a section of top load is bent at the ends of the two arms in the same normal direction, so as to obtain a VT-type vibrator log-periodic antenna linear array; The constraint expression that the VT-type dipole log-periodic antenna linear array does not have grating lobes and the array elements do not overlap in structure is: Among them, K 1 =1.01-0.519τ, K 1 is the low frequency cutoff coefficient, θ 0 is the maximum scanning angle, M is the number of array elements, Θ 1 is the angle between the two arms of the longest oscillator in the logarithmic periodic dipole antenna and the normal after being bent in the same normal direction where the collection line is located, k is the top load length ratio coefficient, B VT is the beam scanning bandwidth of the VT-type dipole log-periodic antenna linear array.

2. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 1, It is characterized in that The constraint expression for the linear array of logarithmic periodic dipole antennas to have no grating lobes and no overlap of array elements in structure is: Among them, B c is the beam scanning bandwidth of the linear array of log-periodic dipole antennas.

3. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 2, It is characterized in that The beam scanning bandwidth of the VT-type dipole logarithmic periodic antenna linear array is the beam scanning bandwidth of the logarithmic periodic dipole antenna linear array. times.

4. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 1, It is characterized in that The constraint expression to ensure that the length of the two arms of the longest oscillator after bending in the direction of the collective line is not less than the length of the projection of any other oscillator in the logarithmic periodic dipole antenna in the direction of the collective line is: Among them, τ is the length change proportional factor, τ Θ is the bending angle change proportional factor, Θ i is the angle between the i-th oscillator and the collection line starting from the end of the longest oscillator.

5. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 1, It is characterized in that The constraint expression of the top load length ratio coefficient k is: Where τ is the length change proportional factor.

6. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 4, It is characterized in that The constraint expression to prevent the two arms of the oscillator from bending in the opposite direction in the same normal direction of the collection line is: Among them, N V is the number of vibrators that need to be bent, and floor is the rounding function.

7. The method for realizing a shortwave broadband phased array antenna based on a log-periodic antenna as claimed in claim 6, It is characterized in that The calculation formula of the maximum bending angle change proportional factor when all vibrators are bent is: Among them, τ Θ_max is the proportional factor of the maximum bending angle change when all oscillators are bent.

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