KR20130064972A - Gain enhancement and size reduction for lpda antennas - Google Patents

Abstract

PURPOSE: An LPDA antenna with reduced size and improved gain is provided to maintain a frequency bandwidth of a prior LPDA antenna and to improve gain by widening an active area, by using a compact wideband single device. CONSTITUTION: One end of a compact wideband single device has a polygonal shape so that the flow of a current has multiple paths. The polygonal shape of the single device shape is constituted with a shape where current flow has multiple paths.

Description

Gain enhancement and size reduction for LPDA antennas

The present invention relates to an LPDA antenna with improved size reduction and gain, and more specifically, a meander technique is applied to reduce the size by about 25% compared to the conventional LPDA antenna. In order to satisfy the same frequency bandwidth as the LPDA antenna and to minimize the gain reduction, a method of widening the active area is proposed, and the size is improved by increasing the frequency bandwidth of each single device by applying an additional branch line. The present invention relates to an LPDA antenna with reduced and improved gain.

In general, a logarithmic dipole array (LPDA) antenna is used in many applications such as direction detection radar, broadcast communication, and EMI / EMC test, which require broadband and directivity due to its wideband characteristics and high directivity. The LPDA antenna is a form proposed by Isbell, which is a series feed array of dipoles whose length is increased by the logarithmic period ratio (τ) at the feed point of the vertex using parallel lines. The length, spacing, and feeding interval of the dipole elements are determined according to the frequency band, the scaling factor τ and the spacing constant σ. The LPDA antenna was first interpreted by Carrel in 1960. In Carrel's analysis, the LPDA antenna is equivalent to the network model, and the dipole and feeder lines are represented using the impedance matrix and the admittance matrix, respectively. The mutual impedance between the dipole components is the electromotive force method.

Since then, the structure of the antenna and the shape change of the device for improving the characteristics of the LPDA antenna is also studied, and the characteristics and design methods according to the structure are well known.

FIG. 1 shows an LPDA antenna structure, which shows a log-periodic dipole array (LPDA).

The relationship between the elements and the intervals is determined by the design parameters, the scaling constant τ and the spacing constant σ. The logarithmic cycle ratio τ is defined as

는 엘피디에이(LPDA) 안테나의 Vertual Apex로부터 k 번째 소자까지의 거리,

는 k 번째 소자의 길이,

는 k 번째 소자의 반경,

는 소자 사이의 간격으로

이다.here,

Is the distance from the Vertual Apex of the LPDA antenna to the kth element,

Is the length of the k th element,

Is the radius of the kth element,

Is the spacing between

to be.

는

인 관계를 가지므로resonant frequency of the kth element

The

As we have relationship

to be.

Radiation in this LPDA antenna occurs in each half-wave dipole element, or active region, resonating at a particular signal frequency. The half apex angle α and the spacing constant σ of the LPDA antenna are given as follows.

, 최고동작주파수를

라고 할 때 그림 3-4 의 가장 긴 다이폴

과 가장 짧은 다이폴

은 다음과 같이 쓸 수 있다.The lowest operating frequency of the LPDA antenna

, The highest operating frequency

Is the longest dipole in Figure 3-4

And the shortest dipole

Can be written as

과

는 각각 과

에 대응되는 동작파장이며

과

는 다음과 같은 실험적으로 주어진다.here,

and

Respectively and

The operating wavelength corresponding to

and

Is given experimentally as

> 0.5 이고

<0.5 이다.In this case, generally

> 0.5

<0.5.

The number N of devices in a given frequency band can be obtained from the following equation.

In addition, the axial length of the antenna in the LPDA antenna is given as follows.

,

와 간격정수 σ 및 대수주기비 τ가가 주어지면 안테나의 구조가 결정된다.Frequency band used from above

,

Given the interval constant σ and the logarithmic period ratio τ, the structure of the antenna is determined.

In order to have good standing wave characteristics and high gain, the LPDA antenna increases the number and size of antenna elements by selecting a large value of the logarithmic period ratio τ and the interval constant σ. As the size of the antenna increases, many researches have been made on the miniaturization of the antenna to reduce the size due to the limited space in the radar and the embedded application. However, as the size of the antenna is reduced, the total area of the antenna is reduced, and accordingly, the performance of the antenna is deteriorated. As a result, many existing studies show that the performance is reduced by reducing the size of the antenna.

In addition, most LPDA antennas are designed with Optimum σ, but LPDA antennas are used at low frequency and have a maximum antenna size of λ _fmin / 2. As it becomes larger, much research has been conducted to reduce the size according to the miniaturization trend.

Therefore, it is necessary to reduce the gain reduction by widening the activation area, and to develop an antenna in which the gain reduction is minimized compared to the conventional LPDA antenna.

In order to solve the above problems, the present invention maintains the frequency bandwidth and widens the active area of an existing LPDA antenna by improving the gain by using a small (30% reduction in length of dipole) wideband single device. The purpose of the present invention is to provide an LPDA antenna with reduced size and improved gain.

In addition, the present invention is designed with τ = 0.86, σ = 0.16, input impedance is 100 Ω, compared to the conventional LPDA antenna, the length of a single device is 30%, the overall size is about 25% Its purpose is to provide an LDP antenna with reduced size and improved gain, while maintaining the same frequency bandwidth while maintaining the same frequency bandwidth, and having a similar gain of 8 dBi.

The present invention is an LPDA antenna having a reduced overall size (25% to 30% of the area), and the frequency of an existing LPDA antenna using a small (30% of the length of a dipole device) broadband single device. In order to maintain the bandwidth and widen the active area to improve the gain, the small broadband single device has a multipath in which the current flows in a polygonal shape at one end.

"또는 "

"로 전류 흐름이 다중경로가 발생할 수 있는 형상이다.The polygonal shape of the single element shape is "

"or "

Furnace current flow is a shape where multipath can occur.

The LPDA antenna with improved size reduction and gain is composed of a single device having a wider bandwidth despite the size reduction (30% of the dipole device length) of the single device.

According to the present invention, it can be seen that the gain is improved compared to the LPDA antenna researched in the same size, and the gain similar to that of the existing LPDA antenna can be obtained.

According to the present invention, τ = 0.86 and σ = 0.16 are designed, and the input impedance is designed to be 100 Ω, and the length of a single device is 30% and the overall size is about 25%, compared to a conventional LPDA antenna. While maintaining the same frequency bandwidth while shrinking, the gain is similar at 8 dBi.

1 is a diagram showing the structure of an LPDA antenna according to the related art.
2 is a graph showing that the phase of the current corresponding to the active region can be seen to see a difference of +90 mA from the peak toward the long dipole element according to the present invention.
3 is a diagram showing that the directivity increases as the value of σ increases according to the present invention.
4 is a structural diagram of an LPDA antenna designed with τ = 0.86 and σ = 0.16 having the same bandwidth and an LPDA antenna designed with τ = 0.94 and σ = 0.16 according to the present invention.
5 is a view showing the effect of increasing the number of dipole elements in accordance with the present invention.
FIG. 6 is a current distribution diagram of the LPDA antenna of FIG. 5. FIG.
FIG. 7 is a view showing 3D radiation patterns of 8 elements of LPDA antenna and 18 elements of LPDA antenna according to the present invention. FIG.
FIG. 8 is a diagram comparing the structure of a conventional LPDA antenna and a proposed LPDA antenna. FIG.
9 is a structure of a single element in the LPDA antenna according to the present invention.
10 is a view showing a structural change of a single device according to the present invention.
11 is a view showing that the length of H is reduced by about 30% compared to the dipole device of the conventional LPDA antenna.
12 is a single element current distribution diagram of 850 MHz, 950 MHz and 1200 MHz in accordance with the present invention.
13 shows the return loss of a proposed LPDA antenna in which a bandwidth-enhanced dipole device is applied to an LPDA antenna.
FIG. 14 is a diagram showing current distribution and simulation values of voltage and current distribution at each frequency 1200 MHz. FIG.
Figure 15 shows that the activation area is widened and the directivity is improved according to the present invention.
16 shows that the present invention has a higher directivity than the existing research method.
17 is a real picture of an LPDA antenna according to an embodiment of the present invention.
18 is a structure of an LPDA antenna according to an embodiment of the present invention.
19 is a detailed structure of a single device in an LPDA antenna according to an embodiment of the present invention.
20 is a return loss of a matching circuit according to an embodiment of the present invention; (a) Return loss of simulated matching circuit (b) Return loss of measured matching circuit
Figure 21 is insertion loss of the coaxial cable according to an embodiment of the present invention
22 is a comparison of the return loss between the simulated conventional LPDA antenna and the proposed LPDA antenna according to an embodiment of the present invention.
23 is a comparison of the measured return loss between the conventional LPDA antenna and the proposed LPDA antenna according to an embodiment of the present invention.
Figure 24 is a comparison of the gain of the conventional LPDA antenna and the proposed LPDA antenna simulated according to an embodiment of the present invention
Figure 25 is a comparison of the measured conventional LPDA antenna and the proposed LPDA antenna according to an embodiment of the present invention
FIG. 26 is an E-plane radiation pattern (@ 1600 MHz) of a conventional LPDA antenna measured according to an embodiment of the present invention.
27 is an E-plane radiation pattern (@ 1600MHz) of the proposed LPDA antenna measured according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

The present invention is an LPDA antenna having a reduced overall size (25% to 30% of the area), and the frequency of an existing LPDA antenna using a small (30% of the length of a dipole device) broadband single device. In order to maintain the bandwidth and widen the active area to improve the gain, the small broadband single device has a multipath in which the current flows in a polygonal shape at one end.

For example, the present invention utilizes a technique that maintains the frequency bandwidth and widens the active area of an existing LPDA antenna by using a small (30% reduction in dipole device length) wideband single device to improve gain. In addition, one end of the wideband single element is formed into a sphere.

The radiation mechanism of the LPDA antenna according to the present invention is radiation of dipole elements of similar length to the front and rear of a dipole element having a length corresponding to each frequency, and the region is called an active region.

In other words, the present invention uses a technique for maintaining the frequency bandwidth and widening the active area of the existing LPDA antenna by using a small (30% reduction in the length of the dipole device) wideband single device to improve the gain. The small broadband single element is formed by rotating one end.

"또는 "

"로 전류 흐름이 다중경로가 발생할 수 있는 형상이다.Specifically, the polygonal shape of the single element shape is "

"or "

Furnace current flow is a shape where multipath can occur.

In addition, the LPDA antenna having improved size reduction and gain is composed of a single device having a wider bandwidth despite the size reduction of the single device (30% of the dipole device length).

For example, as shown in FIG. 2, it can be seen that the phase of the current corresponding to the active region has a difference of +90 mA from the peak toward the long dipole element.

It can also be seen that the voltage abruptly attenuates and the magnitude of the current increases in the activation region, which means radiation in the activation region.

The shape of the active region may be regarded as a dipole linear array of N elements having a phase difference of +90 dB. However, in the case of linear arrays, the spacing between elements becomes an important factor. In the case of LPDA antennas, the spacing is determined by the spacing constant σ.

Thus, as shown in the graph of FIG. 3, the directivity increases as the value of σ increases. However, above the point of optimum σ, the directivity falls again, because the larger spacing causes the offset of the radiation field due to the phase.

4 is a structural diagram of an LPDA antenna designed with τ = 0.86 and σ = 0.16 having the same bandwidth and an LPDA antenna designed with τ = 0.94 and σ = 0.16.

The LPDA antenna of FIG. 4 (b) has eight dipole elements in case of (a) and eighteen dipole elements in case of (b) to satisfy the same bandwidth as shown in FIG. 4 (a). have.

5, it can be seen that matching is better as the number of dipole elements increases. This is because by increasing the number of dipole elements, the regions included in each dipole element are more combined.

FIG. 6 is a diagram illustrating a current distribution diagram of an LPDA antenna in FIG. 5 and showing a difference between activation regions according to a value of τ. FIG.

Therefore, in order to increase the activation area, as shown in FIG. 4 (b), the value of τ should be set to a relatively large value to gradually reduce the size of the dipole.

As shown in FIG. 6, it can be seen that the current distribution region of the dipole device is wider than that of FIG. 6 (a). Thus, when looking at the directivity of Fig. 7, the directivity of the wider active area (b) is stronger. However, the directivity is improved by widening the active area, but the antenna size is increased accordingly. In the case of the antenna in Figure 4 shows a difference in size corresponding to about 2.3 times.

All dipole elements of FIG. 11 have a height of 113 mm, and the length of H is reduced by about 30% compared to the dipole elements of the conventional LPDA antenna.

As you go from Case 1 to Case 4, you can see that the frequency decreases and the bandwidth widens.

By inserting additional structures from Case 1 into Case 2, a single resonance can be made double resonant to increase the bandwidth and to resonate at lower frequencies.

Another additional structure was inserted from Case 2 to Case 3 to create triple resonances to increase bandwidth and lower frequencies. Finally, a translator structure is inserted to match the resonant frequency with the existing LPDA antenna.

In the return loss of FIG. 11, the dipole elements are close to each other, so the point of triple resonance is not seen, but the triple resonance can be confirmed when the higher-order resonance is confirmed.

12 is a current distribution diagram of 850 MHz, 950 MHz, and 1200 MHz. As mentioned above, the dipole elements are in close proximity, so the current distribution for triple resonance is hardly seen, but this can also be confirmed at the higher resonance point.

FIG. 13 shows a return loss of a proposed LPDA antenna in which a small bandwidth wideband single device having an improved bandwidth is applied to an LPDA antenna.

Although the size reduction and gain improvement of the LDP antenna according to the present invention reduce the length H of the dipole element by 30%, the Meander technique is applied to satisfy the electrical length to equalize the bandwidth.

The proposed LPDA antenna has an active area widened by a dipole device having a wide bandwidth and can be confirmed by a current distribution diagram.

Fig. 14 shows current distributions and simulation values of voltage and current distributions at a frequency of 1200 MHz.

As shown in the figure, it can be seen that the region in which voltage and current flow is wider due to the dipole device having a wide bandwidth. This shows that the activation area is widened and the directivity is improved by FIG. 15.

In addition, as shown in Figure 16 it can be confirmed that has a higher directivity than the existing research method.

Optimized antenna proposal

In accordance with an embodiment of the present invention, a method for reducing the gain of reducing the size of an LPDA antenna is proposed, and the following optimized size reduction and gain are improved to explain the basic principle and design method. We propose a LPDA antenna.

In addition, the present invention proposes a technique for minimizing gain reduction by widening the active area by increasing the bandwidth of each single dipole element of the LPDA antenna.

As shown in Figs. 17 to 27, the magnitudes of the currents of the elements of the proposed LPDA antenna and the conventional LPDA antenna designed with values of τ = 0.86 and σ = 0.16 through EM simulation The activation region was confirmed by comparing the magnitude of the voltage, and the activation region of the proposed LPDA antenna was found to be wider.

 As a result, the present invention can confirm that the gain is improved compared to the LPDA antenna studied previously, which has been reduced to the same size, and similar to the gain of the LPDA antenna.

Since the proposed antenna is designed to be 100 Ω, the impedance matching circuit is implemented, and the design of the broadband balun due to the dipole element is required, so the 100 Ω coaxial cable is used.

 Considering the loss from the matching circuit and the coaxial cable, the experimental results show similar trends, and the experimental error can be reduced by simultaneously measuring the conventional LPDA antenna and the proposed LPDA antenna. As a result of the measurement, it is confirmed that the return loss and the gain of the LPDA antenna and the LPLP antenna are similar.

That is, the present invention can be applied to many applications having a limited size by maintaining performance despite the reduction of the size of the LPDA antenna.

Specifically, the LPDA antenna was fabricated and measured using the method described above.

FIG. 17 shows the actual manufactured cross-sectional real picture of the proposed antenna, and FIG. 18 shows the overall structural diagram of the proposed antenna. 19 shows a detailed structure and size of the first dipole device in the LPDA antenna. After the first dipole device, it will be reduced by the value of τ.

In the case of the proposed LPDA antenna, the characteristic impedance is designed as 100Ω. Thus, we designed a 10-stage Binomial matching circuit to include broadband. In FIG. 20, it is a reflection loss result of the matching circuit (a) and the actually manufactured matching circuit (b) of the simulation. In addition, a coaxial line is required to feed the antenna, which serves as a balun of the antenna. 21 is a diagram showing the loss of the coaxial line. FIG. 22 and the like show simulation return loss results when a conventional LPDA antenna and a proposed LPDA antenna are connected to a matching circuit.

FIG. 23 is a comparison of the measured return loss of the conventional LPDA antenna and the proposed LPDA antenna according to an embodiment of the present invention, and FIG. 24 is simulated according to an embodiment of the present invention. A gain comparison between a conventional LPDA antenna and a proposed LPDA antenna is shown. FIG. 25 is a diagram illustrating a measured conventional LPDA antenna and a proposed LPD antenna according to an embodiment of the present invention. LPDA) is a gain comparison of the antenna, Figure 26 is the measured E-plane radiation pattern (@ 1600MHz) of the conventional LPDA antenna according to an embodiment of the present invention, Figure 27 is an embodiment of the present invention The measured E-plane radiation pattern of the proposed LPDA antenna (@ 1600MHz) according to

Claims (3)

LPDA antenna with reduced overall size (25% to 30% of its area), maintaining the frequency bandwidth of existing LPDA antennas using a small (30% of dipole element length) wideband single device And a technique for improving gain by widening an active region, and the small broadband single device has a polygonal shape at one end of which a multi-path flow of current has a size reduction and gain enhanced LPDA (LPDA). ) antenna. The method of claim 1,
Polygonal shape of the single element shape,
"

"or "

"LPDA antennas with improved size reduction and gain, characterized in that the furnace current flow is shaped to multipath. The method of claim 1,
The LPDA antenna with improved size reduction and gain,
Despite the size reduction of the single device (30% of the length of the dipole device), it is composed of a single device having a wider bandwidth, and satisfies the same frequency bandwidth as the LPDA antenna of the conventional dipole device. LPD antenna with improved size reduction and gain.

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