CN1564375A - Method of controlling double-frequency microband antenna resonance frequency - Google Patents

Abstract

A method for controlling the resonant frequency of a dual-band microstrip antenna. Used in the field of wireless communication technology. The U-shaped slit of the present invention is relatively narrow. In the range of 0.003 wavelength, the U-shaped slit is close to the radiation side of the antenna, and the two arms are parallel to the current flow direction. The dual frequency of the antenna is realized by loading the U-shaped slit and the H-shaped patch shape. work and simple control over frequency. In the present invention, the dual-frequency operation of the antenna and the simple control of the frequency are realized through the U-shaped slot loading and the H-shaped patch shape, and the size of the antenna can be further reduced at the same time, and has the following advantages: the two frequency bands of the antenna can be easily Convenient adjustment shortens the design cycle; because the H-shaped profile is used, the current path on the surface of the antenna is elongated, thereby reducing the low-order resonance frequency of the antenna. The purpose of reducing the size of the antenna is achieved.

Description

Method of Controlling Resonant Frequency of Dual-band Microstrip Antenna

technical field

The invention relates to a method for controlling the resonant frequency of an antenna, in particular to a method for controlling the resonant frequency of a dual-frequency microstrip antenna. Used in the field of wireless communication technology.

Background technique

The rapid development of modern wireless communication technology has higher and higher requirements for antennas. Microstrip antennas have been researched and applied more and more because of their advantages of low profile, light weight, low cost and easy fabrication. The communication system working in two or more frequency bands at the same time is an important direction for the development of wireless communication, so dual-band (or multi-band) microstrip antennas have become a hot research and use of microstrip antennas in recent years. In order to make the microstrip antenna dual-frequency work, it can usually be realized by the following methods: multi-patch, slot loading, and lumped element loading (including short-circuit pins). The latter two methods are collectively referred to as resistance loading. Both multi-patch and lumped component loading will complicate the structure of the antenna, while slot loading, as a simple loading method, can realize dual-frequency on a single-layer microstrip antenna, and the production is relatively simple, and it is easy to integrate with microwave circuits integrated. The shape of the slot used to generate the dual-frequency effect can be rectangular, U-shaped, etc. By changing the parameters of the slot, the change of high frequency and low frequency can be realized, and a certain range of frequency ratio can be realized to meet the requirements of different communication systems. However, it is difficult to precisely control the two resonant frequencies during the design process, because these two frequencies often affect each other. Modifying a certain parameter of the antenna will change both resonances. For the designer, it will take many attempts to get a relatively accurate resonance frequency. This repeated debugging process makes the design cycle longer and increases the design cost.

After literature search, it was found that "A dual-band patch antenna with two U-shaped slots, Microwave Optical Technology Letters" (A dual-band patch antenna with two U-shaped slots, Microwave Optical Technology Letters) published in Microwave and Optical Technology Letters , 2000, 26(2): 73-75.), this paper proposes a method of loading a U-shaped slot on a rectangular patch to realize the dual-frequency operation of the antenna, and by changing the parameters of the slot, the two resonant frequencies can be controlled control. However, in this method, the change of the gap parameters will cause the two resonance frequencies to change at the same time, which is time-consuming and laborious for the design work.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, and propose a method for controlling the resonant frequency of a dual-frequency microstrip antenna. By changing the corresponding parameters, it can easily realize the separate adjustment of the high-frequency and low-frequency resonant frequencies. , and a wide range of frequency ratios is obtained. Applying this method to the design and debugging of dual-frequency rectangular microstrip antenna can greatly speed up the design speed and reduce the design cost.

The present invention is achieved through the following technical solutions, the U-shaped slot is relatively narrow, generally in the range of 0.003 wavelength, the U-shaped slot is close to the radiation side of the antenna, the two arms are parallel to the current flow direction, and the U-shaped slot is loaded and the H-shaped The shape of the patch is used to realize the dual-frequency operation of the antenna and the simple control of the frequency.

The inventive method is further defined below:

By changing the arm length of the U-shaped gap, the high-order resonance frequency is changed. When the arm length is lengthened, the resonance frequency decreases, and vice versa.

By removing two equal-sized and mutually symmetrical rectangular blocks on the non-radiating side of the rectangular patch, the path length of the current can be elongated.

The size of the low-order resonance frequency is controlled by changing the size of the middle part of the H-shaped patch. When the middle part becomes narrower, the resonance frequency drops, and vice versa.

The size of the resonance frequency is affected by independent parameters, that is, the high-order resonance frequency is affected by the U-shaped gap, and the low-order resonance frequency is affected by the size of the middle part of the H-shape, and the changes of these two parameters have very little influence on each other , that is, can be adjusted independently. Therefore, the determination of the resonant frequency becomes precise and easy to control.

In the present invention, the dual-frequency operation of the antenna and the simple control of the frequency are realized through the U-shaped slot loading and the H-shaped patch shape, and at the same time, the size of the antenna can be further reduced. Compared with the prior art, the inventive method has the following advantages:

1) The two frequency bands of the antenna can be easily adjusted. Because the influence between the antenna parameters that determine the two available resonant frequency bands is very small, the purpose of separately determining the two resonant frequencies can be achieved by adjusting them separately, which shortens the design cycle.

2) The size of the antenna is greatly reduced. Because the H-shaped profile is adopted, the current path on the surface of the antenna is elongated, thereby reducing the low-order resonance frequency of the antenna. The purpose of reducing the size of the antenna is achieved.

Description of drawings

Fig. 1 is a schematic diagram of the specific application of the rectangular patch of the present invention

Fig. 2 is a schematic diagram of the changes of f ₁₀ , f ₃₀ and f ₃₀ /f ₁₀ when L _m = 8mm is fixed in the embodiment

Fig. 3 is a schematic diagram of the variation of f ₁₀ , f ₃₀ and f ₃₀ /f ₁₀ when d=18mm is fixed in the embodiment

Detailed ways

As shown in the figure, combined with the content of the present invention, taking the rectangular microstrip antenna with coaxial feeding as an example, we can further understand the technical solution of the present invention. This method is also applicable to the antenna fed through the side microstrip. details as follows:

1. The size of the rectangular microstrip antenna is W×L, where the side corresponding to W is the radiation side of the antenna, and L is the current length of the basic resonance mode. Two rectangles are removed from the side L, so that the middle part of the antenna becomes d ×s, the antenna becomes H-shaped. The H-shaped antenna lengthens the current path of the original rectangular patch antenna and reduces the resonant frequency of the antenna, which can greatly reduce the size of the antenna. When the overall size of the antenna is fixed, the resonant frequency of the antenna can be changed by changing the size of d when no slot is added.

2. At the place close to the two radiation sides of the patch, add two U-shaped gaps symmetrically, the width of which is W _s , the length of the gap is 2L _m + L _s , the length of the two arms is L _m , and the short The length in the side direction is L _s , and the distance between the slot and the upper and lower borders of the patch is d ₁ , and the distance between the left and right borders is d ₂ , and the two U-shaped slots are equal in size and symmetrical about the longitudinal axis of the antenna. Adding two rectangular or U-shaped slots near the radiation side of a conventional rectangular antenna can produce a dual-frequency effect, which mainly uses the TM ₁₀ and TM ₃₀ resonance modes of the antenna, because the radiation pattern of TM ₂₀ has a relatively large null, while the radiation characteristics of the TM ₁₀ and TM ₃₀ are similar. The dielectric constant of the medium used in the microstrip antenna is ε _r and the thickness is h.

3. Since the U-shaped slot near the radiation side of the patch has little effect on the current distribution of the TM ₁₀ mode, f ₁₀ mainly depends on the geometric shape of the original H-shaped antenna, so f ₁₀ can be changed by changing the size of d instead The current distribution of TM ₃₀ mode is relatively less affected by the size of d, while its current near the U-shaped gap is relatively concentrated, and is relatively greatly affected by L _m , so f ₃₀ can be changed by changing the size of L _m . In this way, the antenna designer can adjust f ₁₀ and f ₃₀ separately by changing only one parameter of the antenna, thereby avoiding the disadvantage that the two frequencies often affect each other and are difficult to adjust and control in other dual-frequency antenna designs, making The design of the dual-band antenna is more convenient and faster.

Concrete embodiments are provided below:

The specific parameters are as follows: W=42mm, L=70mm, W _s =d ₁ =d ₂ =1mm, s=34mm, L _s =38mm, d=21mm, L _m =8mm, d _f =6.5mm, ε _r = 2.8, h=2mm, fix one value in L _m and d respectively, and then change the other, you can get different frequencies and frequency ratios, the results are shown in Figure 2, the length of fixed L _m is equal to 8mm, d from 10mm changes to 42mm. In Fig. 3, the fixed length of d is equal to 18mm, and L _m changes from 2mm to 10mm. At the same time, other parameters of the antenna are: W=42mm, L=70mm, W _s =d ₁ =d ₂ =1mm, s= 34mm, L _s =38mm, ε _r =2.8, h=2mm, while changing the above parameters, the size of df, that is, the position of the feed point needs to be changed for impedance matching, but the feed point should be kept on the transverse axis. Through actual measurement, it is found that better impedance matching can be obtained between 1 mm and several mm from the center point of the patch. It can be seen from the figure that by fixing L _m = 8mm and changing d, the frequency ratio can be obtained as 1.845-1.998. At the same time, it can be found that f ₃₀ has little change compared with f ₁₀ ; by fixing d = 18mm and changing L _m , the frequency ratio can be obtained It is 1.88-2.296, at this time f ₃₀ varies a lot and f ₁₀ is basically constant. That is, the two resonant frequencies of the antenna can be controlled by changing the arm length of the U-shaped slot and the size of the middle part of the H-shaped patch. In the actual design process, the designer can adjust d and L _m at the same time when designing the antenna, because the influence of the two on the corresponding frequency is almost independent, which brings great flexibility to the design and debugging.

Claims (5)

1. A method for controlling the resonant frequency of a dual-frequency microstrip antenna, characterized in that the U-shaped slit is relatively narrow, and in the range of 0.003 wavelengths, the U-shaped slit is close to the radiation edge of the antenna, and the two arms are parallel to the current flow direction. The U-shaped slot loading and the H-shaped patch shape realize the dual-frequency operation of the antenna and simple control of the frequency. 2. The method for controlling the resonant frequency of a dual-frequency microstrip antenna according to claim 1, wherein the high-order resonant frequency is changed by changing the arm length of the U-shaped slit, and when the arm length is lengthened, the resonant frequency decreases, and vice versa raised. 3. The method for controlling the resonant frequency of a dual-band microstrip antenna according to claim 1, characterized in that, by removing two equal and symmetrical rectangular blocks on the non-radiating side of the rectangular patch, the length of the current is elongated. path length. 4. The method for controlling the resonant frequency of a dual-band microstrip antenna according to claim 1, wherein the size of the middle part of the H-shaped patch is changed to control the size of the low-order resonant frequency, when the middle part becomes narrower , the resonant frequency decreases, and vice versa. 5. The method for controlling the resonant frequency of a dual-frequency microstrip antenna according to claim 1, 2 or 4, wherein the resonant frequency is affected by independent parameters, and the high-order resonant frequency is affected by the U-shaped gap. The low order is affected by the size of the middle part of the H shape, and the changes of these two parameters have very little influence on each other, so they can be adjusted independently.

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