JP2010041089A - Microstrip antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstrip antenna capable of performing impedance matching easily, while suppressing an unnecessary cross-polarized component. <P>SOLUTION: A feeding strip line 12 is connected to a prescribed position (feeding point 14) between the center and an edge at the long side of a rectangular radiation antenna element 11. Then, a stub 13 is provided in the feeding strip line 12. The feeding point 14 in the rectangular radiation antenna element 11 is located at a position of low impedance in the radiation antenna element 11, and to which the feeding strip line 12 having the stub 13 is connected, thus matching impedance easily along with utilizing the matching function owing to the stub 13. Also, the radiation antenna element 11 having narrow width can be achieved without any manufacturing constraints, thus suppressing the level of the cross-polarized component lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microstrip antenna using a dielectric substrate.

  A microstrip antenna made of a strip conductor formed on a dielectric substrate is thin, low-cost, and has excellent productivity. For example, it can be used in automobiles such as collision prevention systems and ACC (Adaptive Cruise Control) systems. Widely used as a transmission / reception antenna for various radio wave sensors including radar.

As a basic example of a strip conductor constituting a microstrip antenna, a shape in which a feed line having a predetermined width is connected to one end of a rectangular radiation antenna element is known.
However, if the feed line is connected to one end of the square radiation antenna element in this way, power is fed to a point with high impedance in the radiation antenna element, so the line width of the feed line is determined in advance. If it is, it becomes very difficult to achieve impedance matching.

  Therefore, in the microstrip antenna having the above-described configuration, in order to reduce the impedance of the feeding point, an antenna in which a notch is formed in a portion to which the feeding line in the radiating antenna element is connected is known (for example, non-patent) Reference 1).

  FIG. 15 shows a microstrip antenna 100 described in Non-Patent Document 1 (however, only the strip conductor in FIG. 15). A microstrip antenna 100 shown in FIG. 15 is formed by connecting a feed line 102 to a substantially square radiating antenna element 101. Two notches 103 and 104 are formed at the connection site of the feed line 102 in the radiating antenna element 101 so as to sandwich the feed line 102, respectively.

With such a configuration, the radiation antenna element 101 can be fed with a low impedance (for example, 50Ω), so that impedance matching between the feed line 102 and the radiation antenna element 101 can be achieved.
Hiroyuki Arai, “New Antenna Engineering-Antenna Technology in the Age of Mobile Communications”, General Electronic Publishing Company, April 9, 1996, p. 62-63

  However, since the microstrip antenna 100 shown in FIG. 15 has such a shape that the cuts 103 and 104 exist on both sides of the feed line 102, the width Wo of the radiating antenna element 101 becomes wide, and the microstrip antenna 100 There is a problem that it is difficult to reduce the size.

  That is, since the microstrip antenna 100 needs to form the cuts 103 and 104 on both sides of the feed line 102, the element width Wo is at least about 5 times the line width of the feed line 102 at the limit of the etching process at the time of manufacture. It is necessary to ensure. Therefore, the element width Wo of the microstrip antenna 100 must be increased, and there is a limit to downsizing the entire microstrip antenna 100.

  Moreover, when the element width Wo of the radiating antenna element 101 is wide, the high frequency current flowing in the width direction increases in addition to the high frequency current flowing in the length direction of the radiating antenna element 101. That is, when a radio wave in the length direction of the radiating antenna element 101 is a main polarized wave, the radio wave is easily radiated in a direction intersecting with the main polarized wave. Therefore, there has been a problem that the radiation level of the cross polarized wave, which is the radio wave in the intersecting direction, is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a microstrip antenna that can easily perform impedance matching while suppressing unnecessary cross polarization components.

  In order to solve the above-mentioned problems, an invention according to claim 1 is a microstrip antenna having 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 includes a feed strip line arranged in a line, a radiating antenna element formed in a rectangular shape and having the end of the feed strip line connected to the long side thereof, and a predetermined in the feed strip line. And a stub connected to the position.

  In the microstrip antenna configured as described above, the radiation antenna element has a rectangular shape, and a feeding strip line is connected to the long side thereof. In the rectangular radiating antenna element, since the impedance on the long side is relatively low, a point where the impedance of the radiating antenna element is low can be set as a feeding point by connecting a feeding strip line to the long side.

  In addition, since the radiating antenna element has a rectangular shape, a radiating antenna element having a smaller width can be realized without being restricted in manufacturing. And while keeping the width | variety of a radiation antenna element small in that way, it becomes easy to take impedance matching by providing the stub for matching to the feed strip line while making the long side into the feed point.

  Therefore, according to the microstrip antenna of the first aspect, it is possible to easily perform impedance matching while suppressing the width of the radiating antenna element to be small and suppressing unnecessary cross polarization components.

  The invention according to claim 2 is the microstrip antenna according to claim 1, wherein, on the long side of the radiating antenna element, there is a predetermined area excluding the center and both ends between the center of the long side and both ends. The feeding strip line is connected to the position.

  In the rectangular radiating antenna element, the impedance at the center on the long side is almost zero, and conversely, the end on the long side is high in impedance. Therefore, impedance matching can be more easily achieved by connecting the feeding strip line at a predetermined position between the long side and the central portion and the end portion.

  It should be noted that the specific position to be connected may be appropriately determined in consideration of the impedance of the feed strip line and the like so as to be matched with these. For example, if the characteristic impedance of the feed strip line is 50Ω, the radiation antenna element The feeding strip line can be connected to a point having an impedance of 50Ω on the long side.

  The invention according to claim 3 is the microstrip antenna according to claim 1 or 2, wherein the stub has a direction of a radiated electric field from the stub generated by a current flowing through the stub. It is connected to the feeding strip line so that it is in the same direction as.

  Since the microstrip antenna of the present invention has a configuration in which a stub is connected to the feeding strip line, naturally a current also flows through this stub, and a radio wave is also radiated from the stub by this current. Although the radiation from the stub is a minute amount compared to the radiation amount from the radiation antenna element, it basically affects the radiation from the radiation antenna element and is therefore not very preferable.

  Therefore, the radiation antenna element and the stub are arranged so that the radiation field from the stub and the radiation field from the radiation antenna element are in the same direction in order to effectively use the radiation from the stub, which is originally unnecessary. is there. In other words, the stub is positively functioned not only for matching but also as a radiating element that radiates radio waves.

  Therefore, according to the microstrip antenna according to claim 3 configured as described above, the radiation from the stub is effectively used together with the radiation from the radiation antenna element, so that the radiation electric field from the radiation antenna element is adversely affected. Thus, the radiation efficiency of the entire antenna can be improved.

  A fourth aspect of the present invention is the microstrip antenna according to the third aspect, wherein the radiating antenna element and the stub are arranged so that their longitudinal directions are parallel to each other. With such a configuration, the direction of the current flowing through the radiating antenna element and the stub is the same direction, so the direction of the radiating electric field is also the same direction.

  The invention according to claim 5 is the microstrip antenna according to claim 3, wherein the field radiation edge line of the radiation antenna element and the field radiation edge line of the stub exist on the same straight line. Thus, it becomes possible to implement | achieve a microstrip antenna with a favorable reflective characteristic by making each electric field radiation | emission edge line on the same straight line. The field emission edge line is a part of the outline of each of the radiation antenna element and the stub and is a side orthogonal to the direction of the radiating electric field.

  A sixth aspect of the present invention is the microstrip antenna according to any one of the first to fifth aspects, wherein the strip conductor has a main feeding strip line arranged in a line shape separately from the feeding strip line. The feeding strip line is projected from the side of the main feeding strip line.

  That is, in the microstrip antenna according to claim 6, a part of the input power propagating in the main feeding strip line is radiated through the feeding trip line provided so as to project from the side of the main feeding strip line. It couple | bonds with an antenna element and is radiated | emitted from this radiation | emission antenna element.

  According to the microstrip antenna configured as described above, a stub is provided in the feed strip line extending from the main feed strip line, and the end of the feed strip line is at the long side of the radiating antenna element (low impedance). Therefore, impedance matching with the main feeding strip line can be easily achieved. Therefore, it is possible to control the coupling amount (the ratio of the power propagating (coupling) to the radiation antenna element side with respect to the input power) from the main feeding strip line to the radiation antenna element in a wide range while keeping the reflection amount low. And a microstrip antenna having desired characteristics can be realized.

Preferred embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
(1) Whole structure of microstrip antenna First, the structure of the microstrip antenna 1 of this embodiment is demonstrated using FIG. FIG. 1A is a plan view of the microstrip antenna 1, and FIG. 1B is a sectional view taken along line XX of FIG.

  As shown in FIG. 1, a microstrip antenna 1 according to the present embodiment has a strip conductor formed on a dielectric substrate 2 having a conductor ground plate 3 formed on the back surface. As shown in FIG. 1A, the strip conductor on the dielectric substrate 2 includes a feeding strip line 12 arranged in a line and a rectangular radiation antenna element connected to the end of the feeding strip line 12. 11 and a stub 13 connected to a predetermined position in the longitudinal direction of the feeding strip line 12.

  The length of the radiating antenna element 11 is, for example, about half (λg / 2) of the wavelength λg of the radio wave propagating through the strip conductor at the operating frequency (76.5 GHz in this example) (hereinafter simply referred to as “intra-tube wavelength”).

  The radiating antenna element 11 is formed in a rectangular shape whose length is longer than the width, and a feeding strip line 12 is connected to a predetermined feeding point 14 on the long side thereof. The feeding point 14 is set at a predetermined position between the center (position corresponding to the center point 15) and the end on the long side of the radiating antenna element 11.

  In the rectangular radiating antenna element 11, the impedance on the long side is generally lower than that on the short side. On the long side, the center portion has substantially zero impedance, and conversely, the end portion on the long side has high impedance. For this reason, a predetermined position between the center portion and the end portion on the long side (except for the center and the end portion) is set as the feeding point 14, and the feeding strip line 12 is connected here, thereby making impedance matching easy. Become. Specifically, for example, if the characteristic impedance on the side of the feeding strip line 12 is 50Ω, the feeding strip line 12 can be connected to a point having an impedance of 50Ω on the long side of the radiating antenna element 11.

  As described above, in the microstrip antenna 1 of the present embodiment, the radiation antenna element 11 is formed in a rectangular shape, and the feeding stripline 12 can be directly connected to the long side (position with low impedance). Unlike the strip antenna 100 (see FIG. 15), it is not necessary to form a cut in the connection portion between the radiating antenna element and the feed line for matching. Therefore, the width of the radiating antenna element 11 can be kept small. Since the width of the element can be suppressed to be small, current components other than the current flowing in the main polarization direction (longitudinal direction) can be suppressed to a low level. Therefore, the generation level of cross polarization from the radiating antenna element 11 can be further increased. It becomes possible to suppress to a low level.

  The radiating antenna element 11 is arranged so that its longitudinal direction is parallel to the longitudinal direction of the stub 13. The microstrip antenna 1 of the present embodiment has a configuration in which the matching stub 13 is connected to the feeding strip line 12, so that a current flows through the stub 13 as a matter of course, and a radio wave is also radiated from the stub 13 by this current. The Although the radiation from the stub 13 is a minute amount compared to the radiation amount from the radiation antenna element 11, it basically affects the radiation from the radiation antenna element 11. Radiant component.

  However, if the direction of the radiated electric field from the stub 13 is matched with the direction of the radiated electric field from the radiating antenna element 11, the radiation from the stub 13 can be effectively used as an effective radiation component.

  Therefore, in the present embodiment, in order to effectively use radiation from the stub 13 that is originally unnecessary, the radiation antenna element 11 is set so that the radiation electric field from the stub 13 and the radiation electric field from the radiation antenna element 11 are in the same direction. And the stub 13 are arranged in parallel. If both are arranged in parallel, the current (main polarization component) flowing in both is in the same direction, so the direction of the radiation electric field from both is also in the same direction. Thereby, the stub 13 can be actively functioned not only for matching but also as a radiating element that radiates radio waves.

  Further, in the microstrip antenna 1 of the present embodiment, the field radiation edge line 11a that is one side of the contour edge line of the radiation antenna element 11 and the field radiation edge line 13a of the stub 13 are present on the same straight line. It is configured.

(2) Characteristics of Microstrip Antenna Next, characteristics (reflection characteristics and transmission characteristics) of the microstrip antenna 1 will be described with reference to FIGS. In this example, as a measurement model for obtaining various characteristics of the microstrip antenna 1, as shown in FIG. 2, a main feeding strip line 16 is provided separately from the microstrip antenna 1, and the main feeding strip line 16 side is provided. The input end of the feed strip line 12 of the microstrip antenna 1 was connected to the side. Then, each characteristic in the microstrip antenna 1 when electric power was input from the input end (right side in FIG. 2) of the main feeding stripline 16 was examined.

  As dimensional parameters to be determined in designing the microstrip antenna 1, as shown in FIG. 2, the length Le and width We of the radiating antenna element 11, the length Ls and width Ws of the stub 13, and the feeding strip The length Lk and width Wk of the line 12, the arrangement interval Ps in the width direction of the radiation antenna element 11 and the stub 13, the element width W of the entire microstrip antenna 1 (= We + Ws + Ps), the center point 15 of the radiation antenna element 11 and the radiation There is a distance d (distance in the longitudinal direction of the radiating antenna element 11) between the antenna element 11 and the feeding point 14. By appropriately designing each of these dimension parameters, a microstrip antenna having desired characteristics can be realized.

  The power input from the input end of the main feed strip line 16 is radiated by a part of the propagation power coupled to the microstrip antenna 1 connected to the side of the main feed strip line 16.

  FIG. 3 shows a microstrip when the microstrip antenna 1 with each dimension parameter appropriately set is connected to the side of the main feed stripline 16 as shown in FIG. It is a figure which shows an example of the reflective characteristic in the antenna 1, and a permeation | transmission characteristic. In this example, the element width W is 1 [mm] among the dimension parameters.

As shown in FIG. 3, the transmission characteristic (transmission coefficient S21) includes the operating frequency (76.5 GHz), and as a whole, the transmission characteristic is good (less loss).
The reflection characteristic (reflection coefficient S11) is greatly reduced by the resonance of the microstrip antenna 1 at the operating frequency (76.5 GHz). That is, the microstrip antenna 1 having a very small amount of reflection at the operating frequency is realized. This is because the microstrip antenna 1 has a configuration in which a stub 13 is provided on the feed strip line 12 and the feed strip line 12 is connected to a predetermined position between the center and the end on the long side of the radiation antenna element 11. This is because impedance matching can be easily achieved, and hence the amount of reflection can be suppressed to a very low level.

(3) Relationship between Dimensions and Reflection Characteristics of Microstrip Antenna Next, the relationship between dimension parameters and characteristics in the microstrip antenna 1 of the present embodiment will be described with reference to FIGS. FIG. 4 is a diagram showing a change in reflection characteristics (reflection coefficient S11) when the element length Le of the radiation antenna element 11 in the microstrip antenna 1 shown in FIG. 2 is changed. FIG. FIG. 6 is a diagram showing a change in reflection characteristics (reflection coefficient S11) when the stub length Ls of the stub 13 in the strip antenna 1 is changed. FIG. 6 shows the radiation antenna element 11 and the stub 13 in the microstrip antenna 1. It is a figure which shows the change of a reflective characteristic (reflection coefficient S11) when changing the space | interval Ps.

  As shown in FIG. 4, when the element length Le is changed, the resonance frequency is changed and S11 is also increased or decreased as a whole. In this example, the optimum element length Le for the operating frequency (76.5 GHz) is 1.29 [mm] that resonates at this 76.5 GHz (that is, S11 is the lowest). The value of S11 also rises as it shifts to the lower side. When it is longer than 1.29 [mm], the resonance frequency is shifted to a higher one, although only S11 is smaller.

  On the other hand, when the stub length Ls is changed, as shown in FIG. 5, the resonance frequency is changed and S11 is also increased or decreased as a whole. That is, in this example, the optimum stub length Ls with respect to the operating frequency is 0.73 [mm] which resonates at this operating frequency, and when shorter than this, the resonant frequency shifts higher and S11 also increases overall. To do. When it is longer than 0.73 [mm], the resonance frequency is shifted to a lower side, although only S11 is smaller.

  When the distance Ps between the radiating antenna element 11 and the stub 13 is changed, as shown in FIG. 6, although the resonance frequency hardly changes, the minimum value of S11 changes. Therefore, in FIG. 6, it can be said that Ps = 0.1 [mm] when S11 is minimum is the optimum value.

(4) Effects of the First Embodiment According to the microstrip antenna 1 of the present embodiment described above, the feed strip line 12 is connected to the long side of the rectangular radiation antenna element 11, and this feed strip line is further connected. 12 is connected to a stub 13 for impedance matching. Therefore, the radiation antenna element 11 having a smaller width can be realized without being restricted in manufacturing. Since the radiation antenna element 11 having a small width can be realized, the cross polarization component can be suppressed to a low level.

  Further, while keeping the width of the radiating antenna element 11 small in this way, the impedance matching is easily achieved by setting the feeding point 14 on the long side and providing the matching stub 13 on the feeding strip line 12. be able to.

  Further, since the radiating antenna element 11 and the stub 13 are arranged so that their longitudinal directions are parallel to each other, radiation from the stub 13 that is originally unnecessary can be effectively combined with radiation from the radiating antenna element 11. Can be used. That is, the stub 13 can be actively functioned not only for matching but also as a radiating element that radiates radio waves. Therefore, the radiation efficiency as the whole antenna can be improved.

  Further, since the field radiation edge line 11a of the radiation antenna element 11 and the field radiation edge line 13a of the stub 13 are arranged on the same straight line, a microstrip antenna with better reflection characteristics is realized. .

  Further, as one of the usage forms of the microstrip antenna 1, as shown in FIG. 2, a configuration in which the main feeding strip line 16 is provided and the microstrip antenna 1 is connected to the side thereof can be adopted. In such a configuration, impedance matching between the main feeding stripline 16 and the microstrip antenna 1 can be easily achieved. Therefore, the amount of coupling coupled from the main feeding stripline 16 to the microstrip antenna 1 is reduced by the amount of reflection. It can be controlled over a wide range while keeping it low.

[Second Embodiment]
In the first embodiment, the microstrip antenna 1 having the configuration as shown in FIGS. 1 and 2 has been described. However, this is an example of the embodiment of the present invention, for example, as shown in FIG. It can also be configured. Hereinafter, the microstrip antenna 20 of this embodiment shown in FIG. 7 will be described.

(1) Configuration of Microstrip Antenna As shown in FIG. 7, the microstrip antenna 20 of the present embodiment has a rectangular radiation antenna element 21 connected to the end of the feed stripline 22 and a predetermined feed stripline 22. The stub 23 is connected to the position.

  The feeding strip line 22 has a substantially L shape bent at an angle of about 90 degrees. A stub 23 is extended from the bent portion of the feeding strip line 22. That is, the stub 23 has a configuration in which the stub 23 is extended from the front end of the line portion before bending in the feeding strip line 22 in the same direction as the longitudinal direction of the line portion before bending.

The length of the radiating antenna element 21 connected to the end of the feed strip line 22 is about half of the guide wavelength λg (λg / 2).
The radiating antenna element 21 is formed in a rectangular shape whose length is longer than the width, and a feeding strip line 22 is connected to a predetermined feeding point 24 on the long side thereof. The feeding point 24 is set at a predetermined position between the center and the end on the long side of the radiating antenna element 21.

  The radiating antenna element 21 is arranged so that its longitudinal direction is parallel to the longitudinal direction of the stub 23. Therefore, as in the first embodiment, radiation from the stub 23 is also effectively used as an effective radiation component.

  Furthermore, the microstrip antenna 20 of the present embodiment is also configured such that the field radiation edge line 21a of the radiation antenna element 21 and the field radiation edge line 23a of the stub 23 exist on the same straight line.

(2) Characteristics of Microstrip Antenna Next, characteristics (reflection characteristics and transmission characteristics) of the microstrip antenna 20 of the present embodiment will be described with reference to FIGS. Also in this example, as a measurement model for obtaining various characteristics of the microstrip antenna 20, a main feeding strip line 26 is provided separately from the microstrip antenna 20, as shown in FIG. A structure in which the input end of the feeding strip line 22 of the microstrip antenna 20 is connected to the side is configured. In this example, the radiating antenna element 21 and the stub 23 are connected so as to be inclined at an angle of about 45 degrees with respect to the longitudinal direction of the main feeding strip line 26. Then, each characteristic in the microstrip antenna 20 when electric power was input from the input end of the main feeding stripline 26 was examined. Note that the dimensional parameters to be determined in designing the microstrip antenna 20 are as shown in FIG. 8, and are the same as those in the first embodiment.

  FIG. 9 shows a microstrip when a microstrip antenna 20 with each dimension parameter appropriately set is connected to the side of the main feed strip line 26 as shown in FIG. 8 and electric power is input to the main feed strip line 26. It is a figure which shows an example of the reflective characteristic in the antenna 20, and a permeation | transmission characteristic. In this example, the element width W is 1 [mm] among the dimension parameters.

  As shown in FIG. 9, the transmission characteristic (transmission coefficient S21) includes the operating frequency (76.5 GHz) as in the first embodiment (see FIG. 3), and has good overall characteristics (low loss). It has become.

  As in the first embodiment, the reflection characteristic (reflection coefficient S11) is also greatly reduced by the resonance of the microstrip antenna 20 at the operating frequency (76.5 GHz). In addition, the minimum value is about -31.7 dB in the first embodiment, but is suppressed to a lower value of -40 dB or less in the present embodiment.

(3) Relationship Between Size and Characteristics of Microstrip Antenna Next, the relationship between size parameters and characteristics in the microstrip antenna 20 of the present embodiment will be described with reference to FIGS. 10 and 11. FIG. 10 is a diagram showing a change in the reflection characteristic (reflection coefficient S11) when the element length Le of the radiation antenna element 21 in the microstrip antenna 20 shown in FIG. 8 is changed. It is a figure which shows the change of a reflective characteristic (reflection coefficient S11) when the stub length Ls of the stub 23 in the strip antenna 20 is changed.

  As shown in FIG. 10, when the element length Le is changed, the resonance frequency changes although the tendency of the overall change of S11 with respect to the frequency is the same. In this example, the optimum element length Le for the operating frequency (76.5 GHz) is 1.28 [mm] that resonates at this 76.5 GHz (that is, S11 is the lowest). It shifts to the lower side, and when it is shorter than this, the resonance frequency is shifted to the higher side.

  On the other hand, when the stub length Ls is changed, as shown in FIG. 11, the resonance frequency changes and S11 also increases or decreases as a whole. That is, in this example, the optimum stub length Ls with respect to the operating frequency is 0.67 [mm] that resonates at this operating frequency, and when longer than this, the resonant frequency shifts to the lower side and S11 also increases overall. However, if it is shorter than this, the resonance frequency shifts to a higher one, and S11 also increases as a whole.

(4) Relative Relationship between Radiation Antenna Element and Each Field Radiation Edge Line of Stub Next, regarding the relationship between the stub length Ls and the characteristics in the microstrip antenna 20 of the present embodiment, particularly, the field radiation edge line 23a of the stub 23 A change in characteristics due to a difference in relative relationship between the radiating antenna element 21 and the electric field radiation edge line 21a of the radiating antenna element 21 will be described with reference to FIGS.

  As described above, the characteristics of the microstrip antenna 20 according to the present embodiment vary depending on the element length Le of the radiating antenna element 21 and the stub length Le of the stub 23. If the radiating edge line 21a and the electric field radiating edge line 23a of the stub 23 are set so as to exist on the same straight line, the characteristics such as the coupling amount and the reflection characteristic are improved.

  12 and 13 show the reflection characteristics when the stub length Ls is changed in the structure of the microstrip antenna 20 in which the best characteristics can be obtained when both the field emission edge lines 21a and 23a are on the same straight line. (FIG. 12) and a transmission characteristic (FIG. 13) are shown. 12 and 13, the “optimum value” of the stub length Ls means the stub length when the field radiation edge lines 21a and 23a of both the radiating antenna element and the stub are on the same straight line.

  As shown in FIG. 12, when the stub length Ls is an optimum value, resonance occurs at the operating frequency, and the reflection coefficient S11 is the smallest. When the stub length Ls is increased from this optimum value, the resonance frequency is shifted to a lower side and S11 is also increased as a whole. Further, when the stub length Ls is shorter than the optimum value, the resonance frequency is shifted to a higher side and S11 is also increased as a whole.

  On the other hand, as shown in FIG. 13, the transmission characteristic (transmission coefficient S21) does not change so much in the operating frequency even when the stub length Ls is changed, and a slight difference is seen in a band lower than the operating frequency. It is.

(5) Effects of the Second Embodiment Also by the microstrip antenna 20 of the present embodiment described above, the feed strip line 22 is connected to the long side of the rectangular radiation antenna element 21, and the feed strip line 22 is further connected. The stub 23 is connected to the impedance matching. Therefore, the radiation antenna element 21 having a smaller width (that is, having a small cross-polarized component) can be realized without being restricted by manufacturing.

  Further, while keeping the width of the radiating antenna element 21 small as described above, the impedance matching can be easily achieved by setting the feeding point 24 on the long side and providing the matching stub 23 on the feeding strip line 22. be able to. Therefore, it is possible to realize the microstrip antenna 20 having various characteristics such as reflection characteristics and transmission characteristics.

  Also in the present embodiment, since the radiation antenna element 21 and the stub 23 are arranged so that their longitudinal directions are parallel to each other, radiation from the stub 23 that is originally unnecessary is radiated from the radiation antenna element 21. The radiation efficiency from the antenna can be effectively utilized, and the radiation efficiency of the entire antenna can be improved.

  Further, since the field radiation edge line 21a of the radiation antenna element 21 and the field radiation edge line 23a of the stub 23 are arranged on the same straight line, the microstrip antenna 20 with better reflection characteristics is realized. Yes.

[Other Embodiments]
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

  In the first embodiment and the second embodiment, the microstrip antennas 1 and 20 having the configuration shown in FIGS. 1 and 7 have been described, respectively, but this is an example of the embodiment of the present invention, and rectangular. As long as the feeding strip line is connected to the long side of the shaped radiating antenna element and the stub is connected to the feeding strip line, various configurations can be adopted.

  For example, a microstrip antenna 30 as shown in FIG. 14 may be configured. As is apparent from the microstrip antenna 30 shown in FIG. 14 in comparison with the microstrip antenna 1 according to the first embodiment shown in FIG. Are connected so as to be inclined at an angle (except for 0 degree and 90 degrees). Even with the microstrip antenna 30 having such a configuration, the same effects as those of the microstrip antennas 1 and 20 of the above-described embodiments can be obtained.

It is a figure showing the structure of the microstrip antenna of 1st Embodiment, (a) is a top view, (b) is XX sectional drawing of (a). It is a top view showing the structure by which the microstrip antenna was connected to the main electric power feeding strip line of 1st Embodiment. It is a figure which shows the reflective characteristic and the permeation | transmission characteristic in the microstrip antenna of 1st Embodiment. It is a figure which shows the relationship between the length Le of a radiation antenna element and reflection characteristics in the microstrip antenna of 1st Embodiment. It is a figure which shows the relationship between stub length Ls and reflection characteristics in the microstrip antenna of 1st Embodiment. It is a figure which shows the relationship between the space | interval Ps of a radiation antenna element and a stub, and reflection characteristics in the microstrip antenna of 1st Embodiment. It is a top view showing the structure (only the part of a conductor strip) of the microstrip antenna of 2nd Embodiment. It is a top view showing the structure by which the microstrip antenna was connected to the main electric power feeding strip line of 2nd Embodiment. It is a figure which shows the reflective characteristic and the permeation | transmission characteristic in the microstrip antenna of 2nd Embodiment. It is a figure which shows the relationship between the length Le of a radiation antenna element and reflection characteristics in the microstrip antenna of 2nd Embodiment. It is a figure which shows the relationship between stub length Ls and reflection characteristics in the microstrip antenna of 2nd Embodiment. It is a figure which shows the relationship between the relative relationship and reflection characteristic of the electric field radiation | emission edge line of both a radiation antenna element and a stub in the microstrip antenna of 2nd Embodiment. It is a figure which shows the relationship between the relative relationship of the electric field radiation | emission edge line of both a radiation antenna element and a stub, and the transmission characteristic in the microstrip antenna of 2nd Embodiment. It is a top view showing the other structural example of a microstrip antenna. It is a figure which shows the structure of the conventional microstrip antenna.

Explanation of symbols

1, 20, 30 ... microstrip antenna, 3 ... ground plate, 11, 21, 31 ... radiation antenna element, 11a, 21a ... field radiation edge line, 12, 22, 32 ... Feed strip line, 13, 23, 33 ... stub, 13a, 23a ... Field emission edge line, 14, 24 ... Feed point, 15, 25 ... Center point, 16, 26 ... Main Feed strip line

Claims (6)

A microstrip antenna having 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 is
A feeding strip line arranged in a line;
A radiating antenna element formed in a rectangular shape and having the long side thereof connected to the end of the feeding strip line;
A stub connected to a predetermined position in the feed stripline;
A microstrip antenna comprising: The microstrip antenna according to claim 1,
The microstrip, wherein the feeding strip line is connected to a predetermined position on the long side of the radiating antenna element between the both ends of the long side and excluding the center and both ends. antenna. The microstrip antenna according to claim 1 or 2,
The stub is connected to the feed strip line so that a direction of a radiated electric field from the stub generated by a current flowing through the stub is the same as a direction of a radiated electric field from the radiating antenna element. A microstrip antenna. The microstrip antenna according to claim 3,
The radiation antenna element and the stub are arranged so that their longitudinal directions are parallel to each other. The microstrip antenna according to claim 3,
The field emission edge line of the said radiation antenna element and the field emission edge line of the said stub are comprised so that it may exist on the same straight line. The microstrip antenna characterized by the above-mentioned. The microstrip antenna according to any one of claims 1 to 5,
The strip conductor has a main feeding strip line arranged in a line, separately from the feeding strip line,
The microstrip antenna, wherein the feed stripline is projected from a side of the main feed stripline.