JP2007053656A - Microstrip array antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstrip array antenna which resolves the issue that the microstrip array antenna causes the rise of a cross-polarization level because of being too thick or the antenna is difficult to manufacture because of being too thin, when realizing a radiating element of the antenna having a large amount of radiation or a radiating element of the antenna having a small amount of radiation in order to achieve a desired directivity. <P>SOLUTION: The microstrip array antenna comprises a linearly arranged feed line and a radiating antenna element connected at about 90° to the feed line and has at least two or more kinds of feed strip line widths. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microstrip array antenna using a dielectric substrate that can be used for various radio wave sensors and communication transmission and reception antennas.

  In recent years, radio sensors using the K band (24 GHz band) as an accident prevention safety device and crime prevention security device have been required for automobiles, road infrastructure, housing, etc., and the development of antennas to be used for this is advancing. It has been. Among various antennas, a microstrip array antenna (hereinafter referred to as “MSAA”) is advantageous in reducing the cost and thickness.

  On the other hand, the microstrip line has a large transmission loss at a high frequency. Therefore, when general MSAA is applied to a high frequency band, there is a problem that a feed loss becomes large and it is difficult to realize a high gain antenna. It was. In view of this, a series-feed microstrip comb line array antenna has been proposed that is difficult to design but has high performance as compared to the parallel feed that is widely used because it is easy to design.

  In order to achieve the directivity required using a series-feed antenna, the amount of radiation from each element is different for each element because of traveling wave excitation, and it is necessary to design each element independently. is there. In the case of a microstrip comb line array antenna, the amount of radiation can be controlled by changing the radiating element width of the antenna.

However, when the amount of radiation is controlled only by the radiating element width of the antenna, there is a problem that the radiation level of cross-polarized waves increases if a thick element is formed to realize large radiation. Further, when a thin element is formed in order to realize small radiation, there is a problem that it is too thin and difficult to manufacture.
JP 2001-44752 A

  The problem to be solved is that when realizing a radiation element with a large radiation amount or a radiation element with a small radiation amount in order to realize a desired directivity, the cross polarization level increases due to being too thick. Or too thin and difficult to manufacture.

A microstrip array antenna according to a first aspect of the present invention is a microstrip array antenna formed of a dielectric substrate having a conductor ground plate formed on the back surface and a strip conductor formed on the dielectric substrate. Are a plurality of rectangular radiating antennas connected and arranged from a side of the feeding strip line arranged in a line and at least one side of both sides of the feeding strip line at a predetermined interval. Each radiating antenna element is a rectangular shape having a different length and width, and is connected so that its longitudinal direction is approximately 90 degrees with the feeding strip line, on one feeding strip line, The microphone according to the second aspect of the present invention, wherein at least one line width conversion structure has two or more feed strip lines having different widths. As for the strip array antenna, the different line widths of the feed strip lines having different widths in the first invention are characterized in that the line widths on the side close to the feed point are thicker than the line width on the side close to the terminal end. .
A microstrip array antenna according to a third aspect of the invention is characterized in that the size of the radiating antenna element according to the first aspect comprises at least two types of radiating antenna elements having different dimensions. It is an array antenna.

Even if the amount of radiation from the radiating element of the antenna is appropriately allocated to each element so as to achieve the desired directivity, the thickness of the radiating element is too thick and the cross-polarization level increases or it can be manufactured too thin. The problem of disappearing can be avoided.
By using a thick feed strip line near the feed point where a small amount of radiation is required and using a thin feed strip line near the end where a large amount of radiation is needed, uniform radiation can be realized over the entire array.
Further, by combining the change in the feed strip line width and the change in the size of the radiating antenna element, it is possible to control the radiation amount more widely and finely and precisely.

The present invention has at least two types of feed strip line widths in a microstrip array antenna composed of a feed line arranged in a line and a radiating antenna element connected to be approximately 90 degrees with the feed line. As a result, the control range of the radiation amount from the element is expanded, and the degree of freedom for directivity formation is increased.
As shown in FIG. 1, the microstrip array antenna of the present invention comprises a dielectric substrate 1 having a conductor ground plate 5 formed on the back surface, and a strip conductor formed on the dielectric substrate. Is a plurality of rectangular strips connected and arranged from the side of the feeding strip line 2 arranged in a line, and at a predetermined interval along at least one side of both sides of the feeding strip line 2. Each radiating antenna element 3 has a rectangular shape with different lengths and widths, and is connected so that its longitudinal direction is approximately 90 degrees with the feeding strip line 2, so that one feeding By having at least one or more line width conversion structures 6 on the strip line, it has two or more types of feed strip line widths. In order to radiate all the residual power, a matching element 4 is connected to the termination.

FIG. 1 shows the structure of a microstrip array antenna, and FIG. 2 shows an enlarged view of one antenna element. The ratio of the radiated power to the input power to each element is called the radiation amount, and the radiation amount distribution with respect to the element number in the longitudinal direction of the main line is shown in FIG. Since the power transmitted through the feed strip line is large on the side close to the feed point, it is necessary to allocate a small amount of radiation to the element with a lower element number. A large radiation amount needs to be assigned to an element with a large element number, and a wide radiation amount control range is required to realize an array.
When the amount of radiation from an element is controlled only by the width of the radiating antenna element according to the conventional method, a very thin element to a very thick element is required. If the element width is too thin, there will be a problem that it becomes impossible to manufacture by substrate etching, and if the element width is too large to be about the same as the length of the element, the direction of the current flowing on the element is only in the longitudinal direction of the element. As a result, there is a problem that the cross polarization level rises and the polarization loss increases.
If the element width is limited to a range where the element width is equal to or less than the element length so that the cross polarization level is within an allowable range from 0.5 mm which is an easily etchable line width, 0.6 mm when the feed strip line width is set to 0.9 mm, % To 30%, and the required radiation amount can be realized only from the third element to the twenty-second element shown in FIG.
Therefore, paying attention to the fact that the amount of radiation is determined by the ratio of the radiation antenna element width to the feed strip line width, the feed strip line width is changed in the middle of the antenna.
FIG. 4 shows the dimensional parameters of the designed radiating antenna element. The line width of the feed strip line from the first element to the second element is 1.2 mm, the line width from the third element to the 10th element is 0.9 mm, and the rest is 0.5 mm. As a result, the control range of radiation was expanded, and all required radiation from 0.4% to 52% shown in Fig. 3 could be realized.
Figure 5 shows the calculated and measured directivity of the designed antenna. As a result of the expansion of the radiation control range, an antenna with a very low side lobe with a side lobe level of -24.3 dB could be realized.

The line width converting structure 6 may be formed between two different radiating antenna elements as shown in FIG. 1, or a step in the middle of the feed strip line as shown in the lower diagram of FIG. It may be formed integrally with the connection portion of the radiating antenna element on the feeding strip line so as not to occur.

  Various radiation characteristics (low side lobe, main radiation (main beam)) required for applications that require small array antennas, such as for short-range sensors for automobiles and subarrays for directivity formation (DBF) by digital signal processing An antenna with direction control) can be realized.

FIG. 1 is an example showing the structure of a microstrip array antenna of the type applicable to the present invention. FIG. 2 is a diagram showing the structure and radiation principle of the unit radiating elements constituting the array antenna of FIG. FIG. 3 is a diagram showing a radiation amount distribution when the present invention is applied to the antenna of FIG. 1 and an antenna with a low sidelobe level is designed. FIG. 4 is a diagram showing dimensional parameters of each radiating antenna element when the present invention is applied to the antenna of FIG. 1 and an antenna with a low sidelobe level is designed. FIG. 5 is a diagram showing calculation results and measurement results of directivity when the present invention is applied to the antenna of FIG. 1 and an antenna with a low sidelobe level is designed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric substrate 2 Feeding strip line 3 Radiation antenna element 4 Matching element 5 Ground plate 6 Line width conversion structure

Claims (3)

In a microstrip array antenna formed from a dielectric substrate having a conductor ground plate formed on the back surface and a strip conductor formed on the dielectric substrate,
The strip conductor has a plurality of rectangular shapes arranged in a line from a feeding strip line arranged in a line and a predetermined interval along at least one side of both sides of the feeding strip line. Each radiating antenna element has a rectangular shape with a different length and width, and is connected so that its longitudinal direction is approximately 90 degrees with the feeding strip line. A microstrip array antenna having two or more different widths of feeding strip lines by means of at least one or more line width conversion structures. 2. The different line widths of the feed strip lines having different widths according to claim 1 are characterized in that the line widths closer to the feed point are wider than the line width closer to the terminal end. Microstrip array antenna. 3. The microstrip array antenna according to claim 1, wherein the radiation antenna element of claim 1 is composed of radiation antenna elements having at least two different dimensions.