Log-periodic antenna band elimination filtering method based on frequency band guiding pre-insertion oscillator

Abstract

The invention discloses a log-periodic antenna band elimination filtering method based on a frequency band guiding pre-insertion oscillator, which takes a stop band as a guiding pre-insertion oscillator and combines an oscillator fine tuning technology based on sensitivity analysis and gradient descent to realize rapid design of log-periodic antenna band elimination filtering. Comprising the following steps: determining tau and sigma feasible regions based on a gain contour line; pre-inserting an oscillator at a stop band boundary frequency to obtain a constraint condition of tau; the whole antenna is actually inserted with oscillators by taking the stop band with the number of the virtual oscillators of the stop band as a positive integer as a reference; solving tau and sigma by taking the minimum length of the set line as an objective function in the feasible region; the oscillators with the length within the stop band are removed; and carrying out frequency band adaptation on the non-reference stop band of the multi-stop-band antenna by adopting an oscillator fine tuning technology based on sensitivity analysis and gradient descent. The design thought that a traditional antenna is firstly designed and then filtered is broken through, the stopband is used as a guide to pre-insert the oscillator, the primary frequency band adaptation process is reduced, the antenna design time is greatly saved, and the antenna performance stability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna design, and in particular relates to a band-stop filtering method for a logarithmic periodic antenna based on a frequency band-guided pre-inserted oscillator. Technical Background

[0002] The band group design of traditional log-periodic antennas often relies on software post-processing (such as filtering and digital signal processing), which has problems such as signal processing delay, high algorithm complexity, and dependence on additional hardware. At the same time, the existing antenna band group design method usually designs the antenna body first, then removes the oscillators within the stopband range based on the antenna body, and finally needs to fine-tune the adjacent oscillators to complete the frequency band adaptation. The frequency band adaptation part is extremely time-consuming, and most of them use parametric scanning methods to traverse all parameters for optimization, which is very dependent on high-performance computers. In addition, if the stopband is too narrow, it is necessary to dynamically adjust the proportional factor to achieve narrowband suppression. The introduction of different structural parameters will not only cause the performance of the antenna at the transition oscillator to fluctuate, but also greatly increase the difficulty of manufacturing the actual antenna. Summary of the Invention

[0003] This invention aims to address the technical problems of traditional log-periodic antenna design, such as the large and time-consuming computational complexity of frequency band adaptation, antenna performance fluctuations at the transition element, and complex physical fabrication. This invention enables rapid hardware-level band-stop filter design, making it suitable for scenarios requiring antenna performance stability and design timeliness. The technical solution is as follows:

[0004] (1) According to the antenna gain requirement G target , using the contour lines between the gain, the scale factor τ and the spacing factor σ to obtain the feasible region G of τ and σ target =G(τ,σ);

[0005] (2) Pre-inserting an oscillator at the stopband boundary frequency to obtain the constraint condition of τ;

[0006] (3) Stopband with the number of stopband virtual oscillators as a positive integer As a benchmark, the entire antenna is actually inserted with oscillators, and the longest oscillator length L1 and the number of oscillators N are obtained;

[0007] (4) In the feasible region, the objective function is to minimize the length of the collective line H(τ, σ) and find the optimal combination of τ and σ;

[0008] (5) Remove the oscillator whose length is within the stop band;

[0009] (6) The frequency band adaptation of the non-reference stopband of the multi-stopband antenna is performed using the vibrator fine-tuning technology based on sensitivity analysis and gradient descent.

[0010] Alternatively, assume that the k stopbands are The constraints of τ are obtained by pre-inserting the oscillator at the stopband boundary frequency:

[0011]

[0012] Where n1, n2, ···, n k is the number of virtual oscillators in each stopband, all of which are greater than or equal to 2, and at least one of them is a positive integer.

[0013] Optionally, the number of stopband virtual oscillators is a positive integer (denoted as n x ) stop band As a reference, the entire antenna is actually inserted with the vibrator (if n x There are multiple values, and the oscillators should be inserted based on these stopbands respectively) to obtain the longest oscillator length L1 and the number of oscillators N:

[0014]

[0015] Where, is the reference stopband start frequency The corresponding oscillator length; L max is the longest conventional vibrator length; L min is the conventional shortest oscillator length; it is obtained by the following formula:

[0016]

[0017] Where, f low is the minimum operating frequency; f high is the maximum operating frequency; c is the speed of light.

[0018] Alternatively, within the feasible region, the optimal τ and σ combination is solved by minimizing the set line length H(τ, σ) as the objective function, where the set line length H is:

[0019]

[0020] Optionally, remove the oscillators whose length is within the stopband. For a single stopband antenna, directly remove the oscillators within the reference stopband (excluding the boundary oscillators). The antenna design is now complete. For a multi-stopband antenna, remove the oscillators within the remaining stopbands. Considering the rapid completion of subsequent frequency band adaptation, the length of the removed oscillators is within the interval

[0021] Optionally, the "sensitivity analysis and gradient descent based dipole fine-tuning technology" is used to adapt the non-reference stopband of the multi-stopband antenna to the frequency band, and the long dipole adjacent to the removed dipole is adjusted to change the starting frequency f of the actual stopband. a-s , adjust the short oscillator adjacent to the removed oscillator to change the actual stop band stop frequency f a-e , until the actual stopband matches the target stopband. The specific operations are as follows:

[0022]

[0023] Where i represents the i-th iteration; ΔL long and ΔL short are the length changes of the long and short oscillators respectively; J is the objective function:

[0024] J(ΔL long ,ΔL short )=ω1(f a-s +Δf a-s -fs ) 2 +ω2(f a-e +Δf a-e -fe) 2 ;

[0025] Where ω1 and ω2 are weight coefficients (the default value is 1). If you need to prioritize the start or end frequency, you can adjust the weight; Δf a-s With Δf a-e are the changes in the actual stopband start and end frequencies, and the frequency shift is inversely proportional to the change in the oscillator length (narrowband approximation):

[0026]

[0027] S is the sensitivity matrix of the oscillator length to frequency:

[0028]

[0029] is the objective function gradient:

[0030]

[0031] α is the learning rate (initial value 0.1, dynamically adjusted according to the objective function J):

[0032]

[0033] Note: The iteration termination condition is that the objective function J < ∈ (e.g. ∈ = 100MHz 2 ) or reaches the maximum number of iterations (such as 10). BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of the design method provided by the present invention.

[0035] Figure 2 This is the feasible domain of structural parameters provided by the present invention.

[0036] Figure 3 This is the standing wave ratio of the antenna after stopband 2 filtering provided by the present invention.

[0037] Figure 4 This is the standing wave ratio of the antenna when the stop band 1 provided by the present invention is not frequency-band adapted.

[0038] Figure 5 The final antenna standing wave ratio provided by the present invention.

[0039] Figure 6 This is the final antenna standing wave ratio of the comparison method provided by the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] The present invention pre-inserts the band-stop vibrator through target stop-band guidance, and then reversely derives the antenna parameters, so that a single stop-band does not need to fine-tune the vibrator for frequency band adaptation. Even for multi-stop-band antennas, the frequency band adaptation process of one stop-band can be reduced; further, a vibrator fine-tuning technology based on sensitivity analysis and gradient descent is proposed to optimize the vibrator length to adapt to the remaining stop-bands, greatly reducing the computer's calculation amount and calculation time; at the same time, since multiple structural parameters are not used, fluctuations in antenna performance at the transition vibrator are avoided, and the convenience of actual antenna manufacturing is improved.

[0042] Taking the logarithmic periodic antenna for partial discharge detection in substations as an example, the design has the following technical indicators:

[0043] Operating frequency: 0.3~3GHz; Band filter frequency band: operator communication interference 0.79~0.96GHz and wireless transmission interference 2.35~2.5GHz; Standing wave ratio: VSWR≤5 in the effective operating frequency band, much greater than 5 in the band filter frequency band; Gain: Gtarget=6dB.

[0044] The present invention provides a band-stop filtering method for a logarithmic periodic antenna based on a band-guided pre-inserted dipole. Figure 1 As shown, the following steps are included:

[0045] (1) According to the antenna gain requirement G target , using the contour lines between the gain, the scale factor τ and the spacing factor σ to obtain the feasible region G of τ and σ target =G(τ,σ);

[0046] In the embodiment of the present invention, according to the antenna gain requirement G target =6dB, and the feasible region G of τ and σ is obtained by using the contour lines between the gain, the proportional factor τ and the spacing factor σ.target =G(τ,σ), such as Figure 2 As shown, it is upward compatible based on the gain, but not downward compatible.

[0047] (2) Pre-inserting an oscillator at the stopband boundary frequency to obtain the constraint condition of τ;

[0048] Assume that the k stop bands are The constraints of τ are obtained by pre-inserting the oscillator at the stopband boundary frequency:

[0049]

[0050] Where n1, n2, ···, n k is the number of virtual oscillators in each stopband, all of which are greater than or equal to 2, and at least one of them is a positive integer.

[0051] In the embodiment of the present invention, the two stopbands are [0.79, 0.96] and [2.35, 2.5], respectively, as shown in the technical indicators. By pre-inserting an oscillator at the stopband boundary frequency, the constraint condition of τ is obtained:

[0052]

[0053] In the formula, the number of virtual oscillators in each stopband n1, n2 ≥ 2, and at least one of them is a positive integer. It is not difficult to deduce that n1 = 3.16n2 by combining the above formulas. The values of n1, n2 and τ are shown in Table 1. It can be found that only the third case is satisfied in the feasible region, and at this time τ is also uniquely determined to be 0.9695.

[0054] Table 1 Values of n1, n2 and τ

[0055]

[0056] (3) Stopband with the number of stopband virtual oscillators as a positive integer As a benchmark, the entire antenna is actually inserted with oscillators, and the longest oscillator length L1 and the number of oscillators N are obtained;

[0057] The stopband is a positive integer with the number of stopband virtual oscillators The whole antenna is actually inserted with the oscillator as the reference, and the number of virtual oscillators is recorded as n x , if n x There are multiple values. The oscillators should be inserted based on these stopbands to obtain the longest oscillator length L1 and the number of oscillators N. Their expressions are:

[0058]

[0059] Where, is the reference stopband start frequency The corresponding oscillator length; l maxis the longest conventional vibrator length; L min is the conventional shortest oscillator length; it is obtained by the following formula:

[0060]

[0061] Where, f low is the minimum operating frequency; f high is the maximum operating frequency; c is the speed of light.

[0062] In the embodiment of the present invention, the entire antenna is actually inserted with the dipoles based on the stopband [2.35, 2.5] where the number of virtual dipoles in the stopband is a positive integer (n2=2), and the longest dipole length L1 and the number of dipoles N are obtained:

[0063]

[0064] (4) In the feasible region, the objective function is to minimize the length of the collective line H(τ, σ) and find the optimal combination of τ and σ;

[0065] In the embodiment of the present invention, the length H of the collective line is:

[0066]

[0067] It is not difficult to find that at this time the length of the collective line H is only related to σ. The smaller σ is, the smaller H is, so σ = 0.075 is taken.

[0068] (5) Remove the oscillators whose length is within the stopband. For single-stopband antenna, directly remove the oscillators within the reference stopband, and the antenna design is completed. For multi-stopband antenna, remove the oscillators within the remaining stopbands (excluding boundary oscillators) to quickly complete the subsequent frequency band adaptation. The length of the removed oscillators belongs to the interval

[0069] In the example of the present invention, if the requirement is a single-stopband antenna with only one stopband [2.35, 2.5], the oscillators in the reference stopband are directly removed (excluding the boundary oscillators). At this point, the single-stopband antenna has been designed and there is no need to fine-tune the oscillators, which greatly shortens the antenna production time. At this time, the antenna standing wave is Figure 3 As shown; this embodiment requires a dual-stopband antenna, and the oscillator in the first stopband needs to be removed. Considering the rapid completion of subsequent frequency band adaptation, the length of the removed oscillator belongs to the interval (0.1587, 0.187). After removal, the antenna standing wave ratio image is as follows Figure 4 shown.

[0070] Considering the space limitation, Table 2 only shows the situation of the removed oscillator and its adjacent oscillators.

[0071] Table 2 Oscillator length and presence / absence at stopband

[0072]

[0073] (6) Adopting the dipole fine-tuning technology based on sensitivity analysis and gradient descent to perform frequency band adaptation on the non-reference stopband (i.e., stopband 1) of the multi-stopband antenna;

[0074] In the present invention, the long vibrator (the vibrator with a length of 0.1887 m in step 5) adjacent to the removed vibrator is adjusted to change the starting frequency f of the actual stop band. a-s , adjust the short oscillator adjacent to the removed oscillator (the oscillator with a length of 0.1567m in step 5) to change the actual stopband end frequency f a-e , until the actual stopband matches the target stopband. The specific operations are as follows:

[0075]

[0076] Where i represents the i-th iteration; ΔL long and ΔL short are the length changes of the long and short oscillators respectively; J is the objective function:

[0077] j(ΔL long ,ΔL short )=ω1(f a-s +Δf a-s -0.79) 2 +ω2(f a-e +Δf a-e -0.96) 2 ;

[0078] Where ω1 and ω2 are weight coefficients (the default value is 1). If you need to prioritize the start or end frequency, you can adjust the weight; Δf a-s With Δf a-e are the changes in the actual stopband start and end frequencies, and the frequency shift is inversely proportional to the change in the oscillator length (narrowband approximation):

[0079]

[0080] S is the sensitivity matrix of the oscillator length to frequency:

[0081]

[0082] is the objective function gradient:

[0083]

[0084] α is the learning rate (initial value 0.1, dynamically adjusted according to the objective function J):

[0085]

[0086] Finally, after 3 iterations, we get the fine-tuning result. The long oscillator increases by 0.0012m, the short oscillator decreases by 0.0005m, and the antenna standing wave is as follows: Figure 5 As shown, the frequency band adaptation has been fully completed.

[0087] In order to demonstrate the superiority of this patent, it is compared with another patent, a logarithmic periodic antenna interference hardware suppression method based on dynamic adjustment of the proportional factor. This method uses multiple proportional factors, first designs the antenna and then removes the oscillator. The final standing wave is as follows: Figure 6 As shown in the figure, it can be seen that the frequency band adaptation of this method is not accurate enough, and the use of multiple proportional factors causes the antenna standing wave ratio at the transition oscillator to fluctuate, resulting in unstable performance. Therefore, the design process of the method proposed in this patent is both fast and convenient, as well as accurate and stable, making it very suitable for applications that require antenna design timeliness and stability.

Claims

1. A band-stop filtering method for a logarithmic periodic antenna based on a band-guided pre-inserted dipole, characterized in that: The steps include: (1) According to the antenna gain requirement G target , using the contour lines between the gain, the scale factor τ and the spacing factor σ to obtain the feasible region G of τ and σ target =G(τ,σ); (2) Pre-inserting an oscillator at the stopband boundary frequency to obtain the constraint condition of τ; (3) Stopband with the number of stopband virtual oscillators as a positive integer As a benchmark, the entire antenna is actually inserted with oscillators, and the longest oscillator length L1 and the number of oscillators N are obtained; (4) In the feasible region, the objective function is to minimize the length of the collective line H(τ, σ) and find the optimal combination of τ and σ; (5) Remove the oscillator whose length is within the stop band; (6) The frequency band adaptation of the non-reference stopband of the multi-stopband antenna is performed using the vibrator fine-tuning technology based on sensitivity analysis and gradient descent.

2. The design method according to claim 1, characterized in that: Assume that the k stop bands are The constraints of τ are obtained by pre-inserting the oscillator at the stopband boundary frequency: Where n1, n2, ···, n k is the number of virtual oscillators in each stopband, all of which are greater than or equal to 2, and at least one of them is a positive integer.

3. The design method according to claim 1, characterized in that: The stopband is a positive integer with the number of stopband virtual oscillators The whole antenna is actually inserted with the oscillator as the reference, and the number of virtual oscillators is recorded as n x , if n x There are multiple values. The oscillators should be inserted based on these stopbands to obtain the longest oscillator length L1 and the number of oscillators N. Their expressions are: Where, is the reference stopband start frequency The corresponding oscillator length; L max is the longest conventional vibrator length; L min is the conventional shortest oscillator length; they are obtained by the following formulas: Where, f low is the minimum operating frequency; f high is the maximum operating frequency; c is the speed of light.

4. The design method according to claim 1, characterized in that: Remove the oscillators whose length is within the stopband. For single-stopband antenna, directly remove the oscillators within the reference stopband. At this point, the antenna design is completed. For multi-stopband antenna, remove the oscillators within the remaining stopbands. Considering the rapid completion of subsequent frequency band adaptation, the length of the removed oscillators belongs to the interval 5. The design method according to claim 1, characterized in that: The oscillator fine-tuning technology based on sensitivity analysis and gradient descent is used to adapt the non-reference stopband of the multi-stopband antenna to the frequency band. The long oscillator adjacent to the removed oscillator is adjusted to change the starting frequency f of the actual stopband. a-s ; Adjust the short oscillator adjacent to the removed oscillator to change the actual stopband stop frequency f a-e , until the actual stopband matches the target stopband. The specific operations are as follows: Where i represents the i-th iteration; ΔL long and ΔL short are the length changes of the long and short oscillators respectively; J is the objective function; S is the sensitivity matrix of the oscillator length to the frequency; α is the learning rate.

6. The design method according to claim 5, characterized in that: Also includes: The objective function is obtained as follows: J(ΔL long ,ΔL short )=ω1(f a-s +Δf a-s -f s ) 2 +ω2(f a-e +Δf a-e -f e ) 2 ; Where ω1 and ω2 are weight coefficients, which are set to 1. If the starting or ending frequency needs to be controlled first, the weight should be adjusted; Δf a-s With Δf a-e are the changes in the actual stopband start and end frequencies, respectively. The frequency shift is inversely proportional to the change in the oscillator length, which is a narrowband approximation. The expression is:

7. The design method according to claim 5, characterized in that: Also includes: The sensitivity matrix S of the oscillator length to frequency is obtained by the following formula:

8. The design method according to claim 5, characterized in that: Also includes: The initial value of the learning rate α is 0.1, and it is dynamically adjusted according to the change of the objective function J:

Images