CN113300123A - Array antenna gain enhancement technology based on mutual coupling matching method - Google Patents

Abstract

The present patent proposes a method for improving the performance of an array antenna by using mutual coupling. The equivalent network method is utilized to analyze the relationship between the mutual impedance and the scattering matrix of the array antenna, the mutual coupling and the antenna gain. Resulting in the situation where the gain of the array antenna remains unchanged. Increasing the coupling element S in the coupling matrix_mn(m ≠ n), the reflection coefficient S_nnThe conclusion must be dropped. The array antenna system is regarded as a multi-port network, and the characteristics of the array antenna scattering matrix are deduced from the relationship between mutual coupling and gain under the condition of certain loss. Mutual coupling between one unit and other units is enhanced, reflection loss of the unit can be reduced, standing-wave ratio is reduced, and performance of the antenna is improved.

Description

Array antenna gain enhancement technology based on mutual coupling matching method

Technical Field

The invention belongs to the technical field of array antennas, and particularly relates to an array antenna gain enhancement technology based on a mutual coupling matching method.

Background

Conventional theory holds that mutual coupling causes a portion of the energy fed into one antenna to be absorbed by other antenna elements, resulting in a significant reduction in the performance of the entire array. The reception efficiency of the overall antenna system is also reduced due to the known mutual coupling, which is the reciprocal of the signals transmitted and received by the antenna in the electromagnetic field.

Therefore, effective ways to remove coupling between array elements are always sought. But coupling, as a physical phenomenon that necessarily exists, cannot be completely eliminated, and it exists more or less between array elements. It is therefore necessary to explore the feasibility of exploiting the effects of coupling to improve antenna performance.

The invention regards the array antenna system as a multi-port network, and derives the characteristics of the scattering matrix of the array antenna from the relationship between mutual coupling and gain: under the condition of certain loss. Mutual coupling between one unit and other units is enhanced, reflection loss of the unit can be reduced, standing-wave ratio is reduced, and performance of the antenna is improved. And then the coupling between the units is enhanced by loading a dielectric plate on the top of the circular array antenna and printing a copper wire on the center of the upper surface of the circular array antenna.

On the premise of meeting the design requirements of antenna gain and directional diagram, the invention properly enhances the coupling between the antenna units, can reduce the structural size of the antenna and change the resonance point of the antenna, thereby improving the standing wave performance of the antenna and increasing the bandwidth. The method provides a new idea for antenna design.

Disclosure of Invention

The problem to be solved by the invention is to utilize the influence of coupling to improve the antenna performance. The invention regards the array antenna system as a multi-port network, and derives the characteristics of the scattering matrix of the array antenna from the relationship between mutual coupling and gain: under the condition of certain loss. Mutual coupling between one unit and other units is enhanced, reflection loss of the unit can be reduced, standing-wave ratio is reduced, and performance of the antenna is improved.

The antenna array may be equivalent to a multiport network:

the N ports in the network are equivalent to N antenna elements and the impedance matrix of the antenna can be expressed as

Wherein Z_nnIs the coefficient of self-resistance, Z_mnIs the coefficient of mutual reactance. And is

The coupling matrix S of the array antenna can be expressed as:

wherein Z₀Is a diagonal matrix. Typically the elements of the diagonal matrix line are all 50 omega. "+" indicates a conjugate position.

Then a is set_nAnd b_nRespectively incident wave and reflected wave of array antenna, and a is obtained by making antenna equivalent to linear multiport network_nAnd b_nAre each an N x 1 matrix of vectors.

The reflection coefficient of the mth unit in the array antenna is:

wherein R is_mIs the reflection coefficient.

When the m-th cell transmits, the coupled energy is:

input power of the array antenna is

And b_n＝Sa_n. The input power of the antenna can be expressed as

The output power of the transmitter is

Wherein b is_sThe incident wave of the power supply end is an N multiplied by 1 matrix. The normalized directional diagram of the array antenna after mutual coupling can be expressed as

Wherein D is a diagonal matrix, the diagonal elements being the matrix (I-S)⁺S) square root of diagonal elements.

And normalizing the array factors of the directional diagram of the array antenna under the ideal condition. With a transmit power of 1, the efficiency of the unit can be expressed as:

where 0 < e < 1, the gain of the array antenna is:

wherein

Is the directional coefficient of one antenna element lobe. As can be seen from equation (11), for a given element of the array antenna, N and

is determined. The gain is proportional to. Considering here the symmetry of a circular array antenna, then there is S_mn＝S_nm(m≠n)，S_mm＝S_nnAt a certain frequency, discussion is given that | S is decreased when the e value increases_mn|(m≠n)

Value or | S_nn| value, or decreasing S simultaneously_mn|、|S_nnL may satisfy this requirement. ② when the e value is not changed, increasing S_mnIf m is not equal to n, then S_nnThe | will necessarily decrease. ③ when the value of e becomes smaller, then decrease | S_nnValue, | increasing S_mnL (m ≠ n), or increasing | S simultaneously_nn|、|S_mnL may satisfy this requirement.

In conclusion, due to the adoption of the technical scheme, the invention has the beneficial effects that:

at a certain frequency, removing coupling can increase the gain of the antenna and improve the efficiency of the antenna. Secondly, under the condition of unchanging gain, the mutual coupling between the antennas is properly increased, so that the standing wave of the antennas can be improved. And thirdly, when the mutual coupling is too large, the gain is affected even if the standing wave is reduced.

Drawings

FIG. 1 is a schematic top view of a circular quinary array antenna

FIG. 2 is a graph showing S parameter comparison of different circular lines

Detailed description of the preferred embodiments

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.

Referring to fig. 1, a small circular antenna array is designed, which is composed of five disc-loaded monopole antennas. While the center distance between array elements is suitably reduced in order to increase the scan angle in the array. The transmission mode adopts sum and difference beams. The physical space between the front and back ends of the array antenna elements is less than 1/2 wavelengths, ensuring that the weakest part of the transmission is exactly opposite the strongest part.

In order to enhance the coupling between the units, a dielectric plate with the dielectric constant of 2.7 and the thickness of 1.5mm is loaded on the top of the antenna, copper wires are printed on the dielectric plate, and the coupling between the units is enhanced through surface waves. By loading on top of the antenna and printing copper lines on it, the copper lines are located in the center of the circular array. The printed copper wire mainly adopts a closed circular ring mode. The size of the coupling is changed by changing the length and width or shape of the line.

Fig. 2 shows the S-parameter and the sum and difference curves for different outer diameters with a width of 1.5 mm. It can be seen that as the outer diameter increases, the coupling between the cells also increases. As the degree of coupling increases, the resonant frequency becomes lower. The standing wave characteristics are also getting better.

The analysis shows that the size of the printed copper wire is properly adjusted, the coupling is enhanced, the low-end standing wave can be effectively reduced under the condition that the gain of the antenna is ensured to be constant and the directional diagram is not distorted, and the performance of the antenna is improved. Thus demonstrating the effectiveness of the process of the present invention.

While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.

Claims (5)

1. An array antenna gain enhancement technology based on a mutual coupling matching method is characterized by comprising the following steps:

the antenna array may be equivalent to a multiport network:

the N ports in the network are equivalent to N antenna elements and the impedance matrix of the antenna can be expressed as

Wherein Z_nnIs the coefficient of self-resistance, Z_mnIs the coefficient of mutual reactance. And is

The coupling matrix S of the array antenna can be expressed as:

wherein Z₀Is a diagonal matrix. Generally diagonal to the lattice lineThe elements are all 50 omega. "+" indicates conjugate placement;

then a is set_nAnd b_nRespectively incident wave and reflected wave of array antenna, and a is obtained by making antenna equivalent to linear multiport network_nAnd b_nVector matrices that are each nx 1;

the reflection coefficient of the mth unit in the array antenna is:

wherein R is_mIs the reflection coefficient;

when the m-th cell transmits, the coupled energy is:

the input power of the array antenna is:

and b_n＝Sa_n. The input power of the antenna can be expressed as

The output power of the transmitter is

Wherein b is_sThe incident wave of the power supply end is an N multiplied by 1 matrix. The normalized directional diagram of the array antenna after mutual coupling can be expressed as

Wherein D is a diagonal matrix, the diagonal elements being the matrix (I-S)⁺S) square root of diagonal elements.

To reason forThe array antenna under the ideal condition normalizes the array factors of the directional diagram. With a transmit power of 1, the efficiency of the unit can be expressed as:

where 0 < e < 1, the gain of the array antenna is:

。

2. the method of claim 1, for a given element of the array antenna, N and

is determined, due to the symmetry of the circular array antenna, then there is S_mn＝S_nm(m≠n)，S_mm＝S_nn。

3. The method of claim 2, wherein | S is decreased as e increases_mnA value of | m ≠ n or | S_nnValue of | or decreasing | S simultaneously_mn|、|S_nnL may satisfy this requirement.

4. The method of claim 2, wherein | S is increased when e is constant_mnIf m is not equal to n, then S_nnThe | will necessarily decrease.

5. The method of claim 2, wherein if e becomes smaller, then | S is decreased_nnValue, | S is increased_mnL (m ≠ n), or increasing | S simultaneously_nn|、|S_mnL may satisfy this requirement.

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