Multi-band multi-gain anti-interference log-periodic antenna theoretical design method

Abstract

The invention discloses a multi-band multi-gain anti-interference log-periodic antenna theoretical design method. The method mainly comprises the following steps: determining a scale factor tau and an interval factor sigma of each band through different gain requirements; calculating oscillator initial lengths corresponding to frequencies at two ends of all frequency bands; determining the number of oscillators in all frequency bands and the actual length according to the initial length, and giving a general expression of the length of the oscillators; calculating the interval and the radius of the oscillator by a general expression; the corresponding oscillator length range is calculated according to the frequencies at the two ends of the interference frequency band, the oscillators actually located in the range are removed, and the optimal length is obtained by performing logarithmic segmentation processing on the adjacent oscillators. The invention discloses a theoretical design method of a multi-band multi-gain anti-interference log-periodic antenna, which can meet the requirements of different bands and different gains of a single log-periodic antenna, reduce the longitudinal length of the antenna, facilitate the miniaturization of the antenna, inhibit interference signals and improve the detection accuracy of the antenna.

Description

Technical Field

[0001] The invention belongs to the field of partial discharge detection of electric power equipment, and in particular relates to a theoretical design method of a multi-band multi-gain anti-interference logarithmic periodic antenna. Background Art

[0002] With the development of ultra-high voltage power transmission, electrical equipment faces a more severe electric field environment, which puts forward higher requirements on the insulation level of power equipment. According to statistics, partial discharge is the main cause of aging and failure of insulation materials of high-voltage power equipment. Partial discharge detection of power equipment can prevent insulation accidents in advance, thereby ensuring the safe and stable operation of equipment. Partial discharge detection mainly relies on various physical phenomena generated by the discharge process, such as ultrasound, electromagnetic waves, light, heat, etc. Ultra-high frequency (UHF) detection of partial discharge has attracted more and more attention in modern high-voltage power systems due to its rich signals, ability to avoid external interference, no contact with equipment and simple methods. The logarithmic periodic antenna is one of the antennas with non-frequency-variable characteristics, but most of the current research on this antenna focuses on the miniaturization and wide bandwidth of the antenna, and less consideration is given to different gain requirements and the influence of interference signals. Based on the existing antenna, research on antennas that can achieve multi-band and multi-gain with a single antenna and can resist interference will help improve the application range and signal detection accuracy of the antenna, and also help reduce the longitudinal length of the logarithmic periodic antenna. Summary of the invention

[0003] In order to solve the technical problems raised by the above background technology, the present invention provides a theoretical design method for a multi-band multi-gain anti-interference logarithmic periodic antenna. It can meet the requirements of different gains in different frequency bands of a single logarithmic periodic antenna, reduce the longitudinal length of the antenna to a certain extent, and is conducive to the miniaturization of the antenna. At the same time, it can also suppress interference signals and improve the detection accuracy of the antenna.

[0004] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0005] A multi-band multi-gain anti-interference logarithmic periodic antenna theoretical design method comprises the following steps:

[0006] (1) Determine the proportional factor τ and spacing factor σ of each frequency band according to different gain requirements;

[0007] (2) Calculate the initial length of the oscillator corresponding to the frequencies at both ends of all frequency bands;

[0008] (3) Determine the number of oscillators and actual lengths of all frequency bands based on the initial length;

[0009] (4) Arrange the general expression of the oscillator length;

[0010] (5) Determine the vibrator spacing and radius;

[0011] (6) Calculate the corresponding oscillator length range according to the frequencies at both ends of the interference frequency band;

[0012] (7) Make corresponding treatment according to different situations of vibrator length;

[0013] (8) Fine-tune the oscillator adjacent to the interference frequency band;

[0014] (9) Similarly, repeat steps (6) to (8) to achieve suppression of multiple interference frequency bands.

[0015] The beneficial effects brought by adopting the above technical solution are:

[0016] The present invention is a new method for theoretically designing logarithmic periodic antennas that divides the logarithmic periodic antenna elements into zones and performs multi-band, multi-gain and anti-interference from local to overall. The present invention can effectively solve the problem of single gain and weak anti-interference ability of logarithmic periodic antennas. In addition, the present invention has the characteristics of being formulated, generalized, designed on demand, and having strong versatility. The present invention is widely applicable, and it has been verified that changing gain requirements and interference frequency bands will not affect the accuracy of the antenna designed by the present invention. The present invention can accurately meet the requirements of multi-band, multi-gain and anti-interference of a single antenna, which is beneficial to the miniaturization of the antenna and the accuracy of signal detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the present invention;

[0018] Figure 2 is a schematic diagram of the antenna structure;

[0019] Figure 3 This is the flow chart of the logarithmic partitioning method;

[0020] Figure 4 is a voltage standing wave ratio diagram of an embodiment of the present invention;

[0021] Figure 5 is a gain diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Combine the following Figure 2 The present invention is described in further detail.

[0023] The present invention proposes a single-pole grounding fault protection method for a DC distribution network grounded by a clamping resistor. Figure 1 As shown, the following steps are included:

[0024] (1) It is stipulated that there are m frequency bands with different gain requirements, and the frequency bands from low to high are f1~f2, f2~f3, ..., f m ~f m+1According to the gain requirements, refer to the relationship curve between gain, proportional factor τ, and interval factor σ to determine the τ value of each frequency band (τ1, τ2, ..., τ m ), σ value (σ1, σ2,…,σ m );

[0025] (2) Calculate the initial length of the oscillator corresponding to the m+1 frequencies:

[0026]

[0027] In the formula, is the frequency f n The corresponding initial length of the oscillator; is the frequency f n Corresponding wavelength; K n is the cut-off constant.

[0028] (3) Determine the number of oscillators and the actual length of the oscillators in all frequency bands, starting from the shortest oscillator and counting forward in sequence (from high frequency band to low frequency band, one oscillator is shared by every two adjacent frequency bands). The formula for the number of oscillators and the actual length of each oscillator in the mth frequency band is as follows:

[0029]

[0030] By analogy, the formulas for the number of oscillators in the first m-1 frequency bands and the actual length of each oscillator are as follows:

[0031]

[0032] In the formula, S n is the number of oscillators in the nth frequency band; L (n,k) is the length of the kth oscillator in the nth frequency band.

[0033] (4) Number all the oscillators from long to short as 1, 2, ..., N. Then the length of any oscillator is L i The general expression of is as follows:

[0034]

[0035] In the formula, p is the pth frequency band; q is the qth oscillator in the frequency band; N is the total number of all oscillators, which can be obtained from the following formula, and S0 is specified as 0:

[0036]

[0037]

[0038] (5) Determine the vibrator spacing d i and radius r i , the formula is as follows:

[0039] d i =2σL i =2σ p L (p,q)

[0040]

[0041] Wherein, the constant t∈[50,200] is selected according to the convenience of actual manufacturing of the oscillator.

[0042] (6) According to the interference frequency band (f α ~f β ) is used to calculate the corresponding oscillator length range M, and the formula is as follows:

[0043]

[0044] (7) Take appropriate measures according to the length of the vibrator:

[0045] Case 1: If there is L i , L i+1 ,...,L i+z ∈M, then these oscillators are eliminated;

[0046] Case 2: If L does not exist i ∈M, that is No processing is done.

[0047] (8) Fine-tune the oscillator adjacent to the interference frequency band:

[0048] For case 1, L i-1 Adjust to L i-1 * , L i+z+1 Adjust to L i+z+1 * ;

[0049] For case 2, L i Increase to L i * , L i+1 Reduced to L i+1 * .

[0050] Determine L using the logarithmic segmentation method i-1 * , L i+z+1 * , L i * and L i+1 * , L i-1 * and L i *pass Figure 3 The left flow chart shows that L i+z+1 * and L i+1 * pass Figure 3 The flow chart on the right side is used to obtain the values, and the corresponding intervals can be input. L i+1 * ∈[τ p L i+1 ,L i+1 ], p in each interval can be obtained by step (4).

[0051] (9) Similarly, repeat steps (6) to (8) to achieve suppression of multiple interference frequency bands.

[0052] The present invention is illustrated below by way of examples.

[0053] Design requirements: The antenna detection range is 0.3~3GHz, the gain requirement at 0.3~1.5GHz is 6dB, and the gain requirement at 1.5~3GHz is 8dB. It has anti-interference effect on interference signals at 0.8~1GHz and 2.4~2.5GHz.

[0054] (1) According to the design requirements, the antenna has two frequency bands, 0.3-1.5 GHz and 1.5-3 GHz, i.e. f1 = 0.3 GHz, f2 = 1.5 GHz, and f3 = 3 GHz. By referring to the corresponding curves between gain and τ and σ with the gain requirements of 6 dB and 8 dB, τ1 = 0.88, σ1 = 0.07, τ2 = 0.94, and σ2 = 0.08 are determined.

[0055] (2) Calculate the initial length of the vibrator corresponding to these three frequencies (units are all millimeters):

[0056]

[0057] (3) Determine the number of oscillators and their actual lengths in all frequency bands, starting from the shortest oscillator. Start calculating forward in sequence. Calculate the number of oscillators in the second frequency band and the actual length of each oscillator:

[0058]

[0059] <![CDATA[L (2 ,1)]]> <![CDATA[L (2,2) ]]> <![CDATA[L (2,3) ]]> <![CDATA[L (2,4) ]]> <![CDATA[L (2,5) ]]> <![CDATA[L (2,6) ]]> <![CDATA[L (2,7) ]]> <![CDATA[L (2,8) ]]> <![CDATA[L (2,9) ]]> 108.5 102.0 95.9 90.1 84.7 79.6 74.9 70.4 66.1 <![CDATA[L (2,10) ]]> <![CDATA[L (2,11) ]]> <![CDATA[L (2,12) ]]> <![CDATA[L (2,13) ]]> <![CDATA[L (2,14) ]]> <![CDATA[L (2,15) ]]> <![CDATA[L (2,16) ]]> <![CDATA[L (2,17) ]]> <![CDATA[L (2,18) ]]> 62.2 58.4 54.9 51.6 48.5 45.6 42.9 40.3 37.9

[0060] By analogy, the number of oscillators in the first frequency band and the actual length of each oscillator are:

[0061]

[0062] <![CDATA[L (1,1) ]]> <![CDATA[L (1,2) ]]> <![CDATA[L (1,3) ]]> <![CDATA[L (1 ,4)]]> <![CDATA[L (1,5) ]]> <![CDATA[L (1,6) ]]> <![CDATA[L (1,7) ]]> <![CDATA[L (1,8) ]]> <![CDATA[L (1,9) ]]> <![CDATA[L (1,10) ]]> <![CDATA[L (1,11) ]]> <![CDATA[L (1,12) ]]> <![CDATA[L (1,13) ]]> <![CDATA[L (1,14) ]]> 571.7 503.1 442.7 389.6 342.8 301.7 265.5 233.6 205.6 180.9 159.2 140.1 123.3 108.5

[0063] (4) All the oscillators are numbered from long to short as 1, 2, ..., 31. Then the length of any oscillator is L i The general expression of is:

[0064]

[0065] Where p is the pth frequency band; q is the qth oscillator in the frequency band, which can be obtained from the following formula (assuming S0 = 0):

[0066]

[0067] (5) Take t = 100, and set L i Substitute the vibrator spacing d into i and radius r i The calculation formula for .

[0068] (6) Calculate the corresponding oscillator length range M based on the upper and lower limit frequencies of the interference frequency band (0.8-1 GHz):

[0069] M = [150,187.5]

[0070] (7) This belongs to case 1, and there is L 10 , L 11 ∈M, remove these two oscillators.

[0071] (8) Adjust L9 to L9 * , L 12 Adjust to L 12 * , Determine L9 using the logarithmic segmentation method * and L 12 * , L9 * pass Figure 3 The left flow chart shows that L 12 * pass Figure 3 The flow chart on the right side is obtained, and the intervals to which they belong are finally obtained. * =196.0,L 12 * =140.1 (i.e. L 12 No changes required).

[0072] (9) Similarly, repeat steps (6) to (8) to achieve the suppression of the interference frequency band 2.4 to 2.5 GHz. The final processing is to eliminate L 23 , L 22 Adjust to L 22 * =63.2, L 24Adjust to L 24 * =58.4 (i.e. L 24 No changes required).

[0073] The final VSWR and gain of the antenna are as follows: Figure 4 and Figure 5 As shown. Figure 4 It can be seen that the voltage standing wave ratio (VSWR) of the antenna in the two interference frequency bands (0.8-1GHz and 2.4-2.5GHz) has increased significantly, which is much higher than the normal level, and can effectively reduce the reception of interference signals; Figure 5 It can be seen that the antenna gain is generally higher than 6dB in the range of 0.3-1.5GHz and significantly higher than 8dB in the range of 1.5-3GHz. In addition, the antenna gain increases significantly near 1.5GHz, which effectively demonstrates the effectiveness of this method.

Claims

1. A theoretical design method for a multi-band, multi-gain, anti-interference log-periodic antenna, characterized by: The steps include: (1) Determine the proportional factor τ and spacing factor σ of each frequency band according to different gain requirements; (2) Calculate the initial length of the oscillator corresponding to the frequencies at both ends of all frequency bands; (3) Determine the number of oscillators and actual lengths of all frequency bands based on the initial length; (4) Arrange the general expression of the oscillator length; (5) Determine the vibrator spacing and radius; (6) Calculate the corresponding oscillator length range according to the frequencies at both ends of the interference frequency band; (7) Make corresponding treatment according to different situations of vibrator length; (8) Use the logarithmic division method to adjust the oscillator adjacent to the interference frequency band; (9) Similarly, repeat steps (6) to (8) to achieve suppression of multiple interference frequency bands.

2. The method for theoretically designing a multi-band, multi-gain, anti-interference log-periodic antenna according to claim 1, characterized in that: In step (2), the initial length of the oscillator corresponding to the frequencies at both ends of all frequency bands is calculated; The initial length of the oscillator corresponding to the m+1 frequencies is calculated by the following formula: In the formula, is the frequency f n The corresponding initial length of the oscillator; K n is the cut-off constant; is the frequency f n The corresponding wavelength.

3. The method for theoretically designing a multi-band, multi-gain, anti-interference log-periodic antenna according to claim 1, characterized in that: In step (3), the number of oscillators and the actual lengths of all frequency bands are determined according to the initial length; Starting from the shortest oscillator, we count forward from the high frequency band to the low frequency band. Every two adjacent frequency bands share one oscillator. The formula for the number of oscillators in the mth frequency band and the actual length of each oscillator is as follows: By analogy, the formulas for the number of oscillators in the first m-1 frequency bands and the actual length of each oscillator are as follows: In the formula, S n is the number of oscillators in the nth frequency band; L (n,k) is the length of the kth oscillator in the nth frequency band.

4. The method for theoretically designing a multi-band, multi-gain, anti-interference log-periodic antenna according to claim 1, characterized in that: In step (4), a general expression for the oscillator length is formulated; Number all the oscillators from long to short as 1, 2, ..., N. Then the length of any oscillator is L. i The general expression of is as follows: In the formula, p is the pth frequency band; q is the qth oscillator in the frequency band; N is the total number of all oscillators, which can be obtained from the following formula, and S0 is specified as 0:

5. The method for theoretically designing a multi-band, multi-gain, anti-interference log-periodic antenna according to claim 1, characterized in that: In step (7), corresponding processing is performed according to different situations of the vibrator length: Case 1: If there is L i , L i+1 ,...,L i+z ∈M, then these oscillators are eliminated; Case 2: If L does not exist i ∈M, that is No processing is done; Where M is the corresponding oscillator length range calculated based on the frequencies at both ends of the interference frequency band.

6. The method for theoretically designing a multi-band, multi-gain, anti-interference log-periodic antenna according to claim 1, characterized in that: In step (8), fine-tune the oscillator adjacent to the interference frequency band: For case 1, L i-1 Adjust to L i+z+1 Adjust to For case 2, L i Increase to L i+1 Reduced to Li +1 * ∈[τ p L i+1 , L i+1 ]; Determine L using the logarithmic segmentation method i-1 * , L i+z+1 * , L i * and L i+1 * , the implementation steps of the logarithmic segmentation method are as follows: ① The left and right endpoints of the interval to be evaluated x are specified as a and b; ② Order ③If the suppression requirement is met or the error is less than 20%, output x at this time; if the suppression is excessive, set b = x and repeat steps ②③; if the suppression is insufficient, set a = x and repeat steps ②③; The p in the interval to be evaluated can be obtained by step (4), and L i+z+1 * and L i+1 * , swap "b=x" and "a=x" in step 3.

Images