JP2007267041A - Microstrip antenna and high frequency sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstrip antenna with a simplified structure where the radiation direction of an electric wave beam is varied and with easy control performance, which is made an antenna for a high frequency sensor for detecting an object located in front of the antenna to detect the position and moving direction of an object existent in a space. <P>SOLUTION: The microstrip antenna comprises a substrate 1; a feed element 2 to which a high frequency signal is fed; and an earth electrode 3 acting as the ground for a high frequency signal, the feed element 2 is disposed at a position facing the earth electrode 3 via the substrate 1. In the microstrip antenna, it further includes a plurality of non-feed elements 4a, 4b disposed at a position facing the earth electrode 3 and excited by the feed element 2; and a plurality of changeover means capable of selecting short circuit states or open states with respect to the earth electrode 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microstrip antenna that transmits microwaves or higher-frequency radio waves, and more particularly to a technique for controlling the radiation direction of an integrated radio wave beam transmitted from a microstrip antenna. The present invention also relates to a high-frequency sensor using a microstrip antenna.

  Conventionally, a power supply element that radiates radio waves by supplying high-frequency signals on a substrate, and is arranged around the power supply element to radiate radio waves by receiving radio waves from the power supply elements without supplying high-frequency signals. Monopole antennas are known. The monopole antenna is equipped with an electrode bar having a quarter wavelength length on a ground plate that acts as a ground for high-frequency signals, and radiates radio waves in a donut shape that is horizontal to the ground plate. The following technologies are known as techniques for changing the direction of radio waves in order to efficiently transmit and receive data. For example, in Patent Documents 1 and 2, one feeding element is arranged in the center and four parasitic elements are arranged in the periphery, and a switching element is arranged in the parasitic element via a reactance element. By switching the connection or release of the switch, the frequency of the parasitic element is changed to make a reflector or a waveguide, and the radiation of the radio wave to the reflector side is stopped, and the radio wave direction is directed to the director side. It is In other words, in order to guide the direction of the radio wave in a predetermined direction, the state of the switch connected to the parasitic element arranged at the symmetrical position with the feeding element sandwiched is changed, and one is a reflector and the other is a waveguide. Yes. A microstrip that emits radio waves from the antenna electrode in the vertical direction by arranging antenna electrodes and ground electrodes on the front and back surfaces of the substrate, respectively, and applying a microwave high-frequency signal between the antenna electrodes and the ground electrode. An antenna is known. The following technologies are known as techniques for controlling the radiation direction of an integrated radio wave beam transmitted from a microstrip antenna. For example, in Patent Document 3, a plurality of antenna electrodes are arranged on a surface of a substrate, and a high-frequency switch is switched to change the length of a high-frequency signal feed line to each antenna electrode. Change the radiation direction of the radio beam. In other words, by changing the lengths of the feed lines to the plurality of antenna electrodes, a phase difference is generated between the radio waves transmitted from the plurality of antenna electrodes, and the integration is performed toward the antenna with a delayed phase. Tilt the direction of the radio wave beam. Patent Document 4 describes a feeding point switching type multi-beam antenna provided with a plurality of feeding elements and a plurality of parasitic elements on a substrate surface. In this multi-beam antenna, all or part of a plurality of power feeding elements can be connected to and opened from a power feeding terminal via a switch, and radio waves with different radiation directions can be obtained by switching the power feeding elements fed by the switch. The beam can be selected.

  Unlike the monopole antenna, radio waves radiated from the microstrip antenna are radiated in the vertical direction with respect to the substrate. Therefore, the presence and the moving direction of the object are detected by the radio signal reflected from the object approaching the antenna. Known as an object detection device. The vertical direction here refers to a direction in which the directivity angle range of the maximum radiation intensity of the integrated radio wave beam is a half-value angle ± 10%. For example, when the half-value angle of the integrated radio wave beam is ± 30 °, it is considered that the radio wave beam is emitted in the vertical direction with respect to the substrate surface when the directivity angle range of the maximum radiation intensity is ± 3 °. In this object detection device, by changing the radiation direction of the integrated radio wave beam from the microstrip antenna as described above, compared to the case where the radiation direction of the integrated radio wave beam is fixed, The position and moving direction of the object can be detected more accurately. For example, by changing the radiation direction of the integrated radio wave beam transmitted from the microstrip antenna to the XY direction and scanning the two-dimensional range, it is arranged on the ceiling of the room, so It can grasp whether there is an object of size, and can obtain information that cannot be detected by a monopole antenna. Applications of the object detection device are diverse, such as target detection in an automatic tracking missile and user detection in a toilet device. In any application, it is very useful to be able to change the radiation direction of the integrated radio beam transmitted from the microstrip antenna. For example, in the case of a user detection device in a toilet device, if the user's position and the approaching user's flow line are detected more accurately, any toilet cleaning device or deodorizer in the simultaneous toilets Proper control of what to do with the device. By the way, the camera may be more suitable for the purpose of accurately grasping the user's condition, but the camera cannot be used in the toilet device. Therefore, it is very important for an object detection device using radio waves to control the radiation direction of an integrated radio wave beam so that the user can be accurately grasped. Incidentally, in Japan, a frequency of 10.525 GHz or 24.15 GHz can be used for the purpose of detecting a human body, and a frequency of 76 GHz can be used for the purpose of preventing a vehicle collision.

JP 2004-128600 A JP 2003-258533 A JP 7-128435 A JP 2003-142919 A

  According to the prior art disclosed in Patent Documents 1 and 2, since the radiation direction of the radio wave beam is horizontal with the substrate, even when the whole body is detected even if the radio beam radiation direction is changed. Must be placed in the central space of the room. Also, for user detection in a toilet bowl or the like, a space is required in the depth direction when an antenna is placed on the wall where the toilet bowl is installed, and it is difficult to secure a construction space compared to a microstrip antenna. In addition, to switch the direction of radio waves, a pair of parasitic elements, centered on the feeding element, must be set as a reflector and a director, so adjustment to change the parasitic element to a predetermined frequency However, since it depends on the accuracy of the switch and the reactance element, if one of them varies, the direction of the radio wave beam cannot be controlled in a predetermined direction. According to the prior art disclosed in Patent Document 4, it is necessary to switch a feed line that transmits a high-frequency signal in order to select a feed element that radiates radio waves in order to change the radiation direction of the radio wave beam. is there. For this reason, the size of the antenna becomes large due to the need to arrange feed elements that only change the direction of the radio wave, the degree of freedom of installation is eliminated, and at the same time the impedance to the microwave signal of a specific frequency to be used is a predetermined appropriate value. It is necessary to use a precisely adjusted high frequency switch, and such a high frequency switch is quite expensive. In particular, when changing the radiation direction of the integrated radio wave beam continuously or in multiple stages, a large number of high-frequency switches are required. However, it is not practical to use many expensive parts for applications such as a user detection device in a toilet device.

  Therefore, an object of the present invention is to provide a microstrip antenna that is simple and small in size and can reliably change the radiation direction of a radio wave beam in a predetermined direction. It is to detect the moving direction and the flow line of an object approaching the system.

  In order to achieve the above object, the invention according to claim 1 is composed of a substrate, a feeding element to which a high-frequency signal is fed, and a ground electrode that acts as a ground for the high-frequency signal, and the ground electrode is interposed through the substrate. In the microstrip antenna in which the feeding element is disposed at a position facing the grounding element, the parasitic element that is disposed at the position facing the grounding electrode and is excited by the feeding element, and the ground electrode is short-circuited or opened. Selectable switching means, and when the parasitic element is selected to be short-circuited or opened with respect to the ground electrode by the switching means, the integrated main beam of the radio wave is in one of the selected states. Radiating from the vertical direction to the horizontal direction with respect to the substrate surface in the other selected state.

  In general, a microstrip antenna is provided with a feeding element that radiates radio waves to the outside when a high-frequency signal is fed, and a parasitic element that radiates radio waves to the outside by receiving signals of the same frequency excited by the feeding element. Then, a delay in timing excited from the positional relationship between the feed element and the parasitic element, that is, a phase delay occurs, and an integrated radio beam of the radio wave radiated from the feed element and the radio wave radiated from the parasitic element The direction of radiation changes. If the feed element and the parasitic element have the same phase, a radio wave beam is radiated in the vertical direction with respect to the substrate surface. If the phase of the feed element is ahead of the phase of the parasitic element, the parasitic element from the vertical direction with respect to the substrate surface. A radio wave beam is radiated to the direction side where is placed. That is, the phase is changed by adjusting the positional relationship between the feeding element and the parasitic element, and the radio wave beam can be changed to a predetermined angle in accordance with the amount of change. The predetermined angle here is an amount that is uniquely determined by the amount of delay in the phase of the radio wave, the distance between the feed element and the parasitic element, and the frequency to be used. Since this phase delay depends on the molding accuracy of the circuit pattern, it is very accurate by using etching, and is set in a predetermined direction on a straight line composed of a parasitic element and a feeding element with good reproducibility. It is possible. In addition, when the switching means connected to the parasitic element is used to select a short circuit or open with the ground electrode, the amount of current excited by the parasitic element can be limited, and as a result, the amount of radio waves radiated from the parasitic element is The proportion of the integrated radio wave constituted by the power feeding element is remarkably reduced, and is governed only by the amount of radio wave radiated from the power feeding element, and the radio wave direction can be set in the vertical direction with respect to the substrate. Therefore, it is not a switch for switching the state of the high-frequency signal supplied to the feed element or setting the parasitic element to a predetermined frequency, but a switching means for limiting the state excited by the parasitic element. Therefore, there is no need to strictly control the amount of loss when short-circuited to the ground electrode, the direction of radio waves can be switched with a simple configuration, and radio waves can be emitted vertically to the board, saving space. The structure can radiate radio waves to an object or human body.

When the parasitic element is selected to be short-circuited or opened with respect to the ground electrode by the switching means, it is radiated in the vertical direction with respect to the substrate surface in one selected state. The vertical direction here refers to a direction in which the directivity direction of the maximum radiation intensity in the main beam of the integrated radio wave is a half-value angle ± 10% of the integrated radio beam.
In the case of a general microstrip antenna, when the number of elements to be fed is one, the half-value angle of the radio wave radiated in the direction perpendicular to the substrate surface is around ± 30 °, and four elements to be fed are arrayed. The half-value angle of the radio wave beam emitted is about ± 20 °, and the half-value angle of the radio beam emitted when 16 elements to be fed are arrayed is about ± 15 °.
When the half-value angle of the radio beam is within ± 10 °, if it is tilted from ± 2 ° to ± 3 ° from the front direction, it will greatly affect the performance of sensing a moving object, but the half-value angle of the radio beam is ± 20 ° to ± Even if it is tilted from ± 2 ° to ± 3 ° from the front at around 30 °, it hardly affects the performance of sensing the moving body. If it is always directed in the front direction, a control circuit for adjusting variation due to manufacturing is required and the operability is complicated, but such adjusting means is not required.

  In order to achieve the above object, a second aspect of the present invention comprises a substrate, a power feeding element to which a high-frequency signal is fed, and a ground electrode that acts as a ground for the high-frequency signal, and the ground electrode is interposed through the substrate. In the microstrip antenna in which the feed element is disposed at a position facing the ground electrode, a plurality of parasitic elements are disposed at positions facing the ground electrode and excited by the feed element; Each of the parasitic elements is arranged at a symmetrical position on the same plane with the feeding element as a center, and all the parasitic elements are arranged by the switching means. When the ground electrode is selected to be short-circuited or opened, the integrated main beam of radio waves is perpendicular to the substrate surface, and at least one of the parasitic elements is the other When different from the selected state of the parasitic element, from the vertical direction to the substrate surface in the horizontal direction, characterized by radiation.

  As described above, a microstrip antenna is used to feed a high-frequency signal to radiate a radio wave to the outside, and a plurality of non-radiation devices that receive a signal of the same frequency excited by the power feeding element and radiate a radio wave to the outside. Since the plurality of parasitic elements are on the same plane with respect to the ground electrode and are in a symmetric position with the feeding element as the center, the parasitic elements in the symmetric position can be opened or closed simultaneously by the switching means. When switching to one of the short-circuits, the amount of current excited from the feed element to the parasitic element is the same as the amount of phase lag, so the amount of phase change on the straight line composed of the parasitic element and the feed element cancels out. Thus, the radiation direction of the integrated radio wave beam is radiated in the vertical direction with respect to the substrate. In addition, if one of the parasitic elements at the symmetrical position is opened or short-circuited to the ground electrode by the switching means and the amount of current excited by the parasitic element is limited, the amount of radio waves radiated from the parasitic element as a result Since the proportion of the integrated radio wave composed of the feeding element and the parasitic element on the other side is significantly reduced, it is governed only by the amount of radio waves radiated from the feeding element and the parasitic element on the other side, The direction of the radio wave is inclined and radiated in a horizontal direction by a predetermined angle corresponding to the amount of phase delay from the vertical direction to the substrate. Therefore, when the switching means connected to each parasitic element is alternately switched between open and short states, the radio wave beam is also symmetrical with respect to the substrate from the vertical direction according to the state, and a pair of parasitic elements. It can be tilted on a straight line composed of feeding elements.

  In order to achieve the above object, the invention according to claim 3 is characterized in that a plurality of the feeding elements are arranged.

  By arranging a plurality of feeding elements, the beam direction can be switched while the radio wave beam is narrowed down, and the detection distance can be extended.

  In order to achieve the above object, a fourth aspect of the present invention includes a substrate, a plurality of power supply elements in which at least one power supply element is supplied with a phase in which a high frequency signal is different from that of other power supply elements, In the microstrip antenna, the plurality of feeding elements are arranged at positions facing the ground electrode via the substrate, the microstrip antenna is arranged at a position facing the ground electrode, A parasitic element excited by a feeding element; and a switching unit that can select a short circuit or an open state with respect to the ground electrode, and the parasitic element is short-circuited or opened with the ground electrode by the switching unit. The main beam of the integrated radio wave from the position where the feeding element whose phase is advanced with respect to the substrate surface in one selected state is arranged. Phase to the late predetermined direction in which the feed elements are disposed is, in the other selected to only a direction inclined a predetermined angle from said predetermined direction, characterized by radiation.

  When a parasitic element is selected to be short-circuited or opened with the ground electrode by the switching means, the phase of the main beam of the integrated radio wave is delayed due to the phase relationship of the arranged feeder elements in one selected state Radiates in a predetermined direction in which the feeding element is arranged, and in the other selected state, radiates in a direction inclined by a predetermined angle from the predetermined direction due to the phase relationship between a plurality of feeding elements and parasitic elements.

  In order to achieve the above object, a fifth aspect of the present invention includes a substrate, a plurality of power supply elements in which at least one power supply element is supplied with a phase in which a high-frequency signal is different from that of other power supply elements, and a ground for a high-frequency signal. In the microstrip antenna, the plurality of feeding elements are arranged at positions facing the ground electrode via the substrate, the microstrip antenna is arranged at a position facing the ground electrode, Each parasitic element includes a parasitic element that is excited by a feeding element, and each parasitic element includes a switching unit that can select a short circuit or an open state, and each parasitic element is centered on a plurality of the feeding elements. When the switching means selects all the parasitic elements to be short-circuited or opened with the ground electrode, the integrated radio wave The in-beam is in a predetermined direction in which the feeding element whose phase is delayed from the position where the feeding element whose phase is advanced with respect to the substrate surface is arranged. When the parasitic element is different from the selected state, the radiation is performed in a direction inclined by a predetermined angle from the predetermined direction.

  When all parasitic elements are selected to be short-circuited or opened with the ground electrode by the switching means, a plurality of integrated main radio wave beams are fed elements whose phases are delayed due to the phase relationship of the arranged feeder elements. When at least one of the parasitic elements is radiated in the arranged predetermined direction and is different from the selected state of the other parasitic elements, it is inclined by a predetermined angle from the predetermined direction due to the phase relationship between the plurality of parasitic elements and the parasitic elements. Radiate in the direction

  In order to achieve the above object, according to a sixth aspect of the present invention, the switching means includes a switch that passes or blocks a high-frequency signal and a reactance element that propagates the high-frequency signal, and one end of the reactance element is the non-reactive element. In a predetermined position of the power feeding element, the other end of the reactance element is connected to the input terminal of the switch, the output terminal of the switch is connected to the ground electrode, and when the switch is applied with a constant DC voltage, The parasitic element and the ground electrode are short-circuited or opened.

  As described above, when the switching means is constituted by a reactance element and a switch, the degree of freedom in installing the switch is improved and the electromagnetic field state generated between the parasitic element and the ground electrode that affects the radiation amount of the radio wave is blocked by the switch. Therefore, the amount of the radio wave beam radiated from the parasitic element can be maintained, and the radiation amount of the radio wave integrated with the feed element can be maintained. In addition, since the switching means performs a constant DC voltage without changing the power applied to the switch, the power supply circuit can be simplified.

  In order to achieve the above object, the invention according to claim 7 is characterized in that the switch is arranged on the same plane as the ground electrode.

  In this way, when a switch that is a part of the switching means is arranged on the ground electrode surface, the portion facing the parasitic element is not cut out by the switch, so an electromagnetic field state generated between the parasitic element and the ground electrode The amount of the radio wave beam radiated from the parasitic element can be maintained without destroying.

  In order to achieve the above object, according to an eighth aspect of the present invention, the reactance element includes a conduction hole disposed inside the substrate, and a thin film line including a distributed constant circuit disposed on or inside the substrate. The one end of the conduction hole and the one end of the thin film line are connected.

  In this way, since no electronic components are used in the reactance element, and the circuit pattern can be formed in the multilayer substrate processing process, there is little variation in the constants of the components and variations due to deviations in the mounting position and rotation direction. Therefore, the amount of current excited on the parasitic element can be set with high accuracy, and the phase amount constituted by the feeder element and the amount of the integrated radio beam can be controlled.

  In order to achieve the above object, the invention according to claim 9 is characterized in that the reactance element has a length of [λg / 4] × n (λg: wavelength on substrate, n: integer).

  When the length of the reactance element is set in this way, the amount of current excited by the parasitic element can be accurately set to “0” by the switch at the site connected to the upper reactance element of the parasitic element. And the direction of the radio wave beam integrated with the feed element can be controlled with high accuracy. Further, even if the length of the reactance element is not strictly set to [λg / 4] × n, the microstrip antenna of the present invention can be provided if ([λg / 4] ± [λg / 8]) × n. It is possible.

  In order to achieve the above object, the invention according to claim 10 is characterized in that one end of the reactance element is connected to a position on the parasitic element which matches the impedance of the thin film line.

  If the impedance of the reactance element and the parasitic element is matched in this way, the high frequency signal between the ground electrode and the parasitic element is not lost when the switch is short-circuited. The amount of current to be transmitted can be reliably limited, and the direction of the radio wave beam integrated with the feed element can be controlled with high accuracy.

  In order to achieve the above object, according to the invention described in claim 11, one end of the reactance element is used from an end side of the parasitic element orthogonal to the excitation direction and an end side of the parasitic element orthogonal to the excitation direction. It is characterized in that it is connected to the part of the parasitic element that is directed to the center of 1/10 wavelength (λg) of the frequency.

Considering generally, the impedance point of 50Ω of the parasitic element is near 0.17λg from the end perpendicular to the excitation direction of the parasitic element, and this point has a large impedance change rate. This means that the radiation state (radiation amount / radiation direction) of radio waves is likely to change. The higher the operating frequency, the more accurate the position accuracy of connecting the reactance elements, which greatly affects the quality variation due to manufacturing. To come. By connecting a reactance element to the part of the parasitic element from the end face of the parasitic element 4 orthogonal to the excitation direction toward the central portion of 1/10 wavelength of the operating frequency, it is less susceptible to manufacturing variations and has stable performance. Obtainable.
In addition, since the impedance of the part of the parasitic element is high impedance, if the impedance of the reactance element is set to a high impedance state, the ground electrode and Since the high-frequency signal between the parasitic elements has almost no reflection or loss, the amount of current excited on the parasitic element can be reliably limited, and the direction of the radio wave beam integrated with the parasitic element can be accurately controlled. Can do.

  In order to achieve the above object, the invention according to claim 12 is characterized in that at least one of the parasitic elements is different in position of the reactance element to be connected from the other parasitic elements.

  When the position of the reactance element is changed with respect to the vibration direction in this way, the degree of freedom of installation is improved. Therefore, when a large number of parasitic elements are arranged around the feeding element, and each is provided with a reactance element and a switch. However, since there is no switch mounting space and a part of the ground electrode facing the parasitic element is not cut out, the electromagnetic field state generated between the parasitic element and the ground electrode can be maintained.

  In order to achieve the above object, the invention according to claim 13 is characterized in that the impedance of the thin film line is 50Ω.

  When the impedance of the thin film line is set to 50Ω in this way, the input impedance of the switch connected to the subsequent stage is generally set to 50Ω, so that the consistency of the connection can be maintained, and when the switch is short-circuited, Since the high-frequency signal between the ground electrode and the parasitic element is not lost, the amount of current excited on the parasitic element can be surely limited, and the direction of the radio wave beam integrated with the feeder element can be accurately controlled. it can.

  In order to achieve the above object, the invention according to claim 14 is characterized in that the feeding element and the parasitic element have the same length of one side in the excitation direction.

  By aligning the excitation direction lengths of the feed element and the parasitic element in this way, the frequency of the radio wave radiated from the parasitic element by the current excited by the feed element matches that of the feed element. Radio waves are integrated without being separated, and the radio wave beam can be varied in a predetermined direction in accordance with short-circuiting or opening of the switching means.

  In order to achieve the above object, a fifteenth aspect of the present invention is a high-frequency sensor comprising the microstrip antenna according to any one of the first to fourteenth aspects.

  When a high-frequency sensor having a microstrip antenna that can change the direction of radio waves is configured in this way, the direction of the radio waves radiated from the sensor is perpendicular to the substrate surface and from the vertical direction to the parasitic element placement direction or the opposite side. Since it can be switched to an inclined state, for example, when it is installed on a wall surface, if the sensor is installed so that it is in the front direction and the downward direction, each height will be recognized even if a human body with a height approaches. If the direction of the radio wave is switched between the front direction and the parallel to the floor surface, it can be determined whether it is a human body or an object approaching the sensor, and a sensor that accurately determines the information necessary for the space is configured. it can. In addition, since the direction of the radio wave radiated from the sensor can be switched from the vertical direction and the vertical direction to the state in which one of the parasitic elements is arranged with respect to the substrate surface, for example, when installed on a wall surface, When the sensor is installed so that it is in the front and vertical directions, it can detect and detect the height even when a human body with a height approaches, or it can detect multiple radio wave directions in parallel to the front direction and the floor surface. In the case of switching, it is possible to determine whether a human body or an object that approaches the sensor or to cross it, and it is possible to configure a sensor that accurately determines information necessary for the space. A microstrip antenna that can easily and simply control the directivity direction of a radio wave beam is useful as a sensor that recognizes the position and moving direction of an object existing in front of the antenna in a two-dimensional or three-dimensional manner.

  According to the present invention, in a microstrip antenna, the radiation direction of a radio wave beam can be reliably changed in a predetermined direction with a simple and small configuration, and the position and moving direction of an object in space can be achieved by using a high frequency sensor antenna. And the flow line of an object approaching the system can be detected.

Hereinafter, embodiments of a microstrip antenna according to the present invention will be described with reference to the drawings.
In the following examples, the thickness of the substrate and the pattern dimensions in the drawings are different from actual shapes for convenience of explanation.
FIG. 1 is a first embodiment of a microstrip antenna according to the present invention, (a) a plan view seen from the front, (b) a plan view seen from the back, and (c) a sectional view taken along line AA ′.

The microstrip antenna shown in FIG. 1 includes an insulating substrate 1, a feed element 2 to which a high-frequency signal is fed, a ground electrode 3 that acts as a ground for the high-frequency signal, and a parasitic element 4 that is excited by the feed element 2. And the parasitic element 4 and the ground electrode 3 are comprised from the switching means which enables selection of a short circuit or an open state. The switching means is disposed in the switch 7 that passes or cuts off the high-frequency signal when a constant DC voltage is applied to the control electrode 8 and in the substrate 1 that propagates the high-frequency signal from a predetermined position of the parasitic element 4 to the switch 7. And a thin film line 6 made of a distributed constant circuit disposed on one surface of the substrate. In this case, a reactance element is formed by connecting one end of the conduction hole 5 and one end of the thin film line 6, and the sum of the length of the through hole 5 (same as the thickness of the substrate) and the thin film line 6 when viewed from above is the reactance element. It becomes the length.
The feeding element 2 and the parasitic element 4 have the same shape, and are arranged on the surface of the substrate 1 facing the ground electrode 3 with the substrate 1 interposed therebetween with a predetermined interval. A switch 7 is disposed on the back surface of the substrate 1 on which the ground electrode 3 is formed. One end of the conduction hole 5 is at a predetermined position of the parasitic element 4, one end of the thin film line 6 is at the other end of the conduction hole 5, and the input end of the switch 7 is at the other end of the thin film line 6. A ground electrode 3 is connected to each output terminal.

The feed element 2 having a microstrip antenna structure (which efficiently radiates radio waves in the front direction of the feed element 2 using electromagnetic coupling with the ground electrode 3) has a half wavelength (λg / 2: λg... Substrate 1) Λ = εr ^1/2 · λg), where λ is the wavelength of the high-frequency signal in the vacuum and the wavelength of the radio wave is λ, and the dielectric constant of the substrate 1 is εr. A feeding point P for feeding a high-frequency signal is provided at a point where the impedance is 50Ω. The position of the feed point P varies depending on the impedance of the transmission line through which a high-frequency signal is propagated from an oscillation circuit (not shown). Generally, the input / output terminals of the oscillation circuit and the detection circuit connected to the antenna are 50Ω. Designed to be consistent.

  The thin film line 6 is a coplanar line composed of a distributed constant circuit and having an impedance of 50Ω. One end of the conduction hole 5 is connected to a position where the impedance of the parasitic element 4 is 50Ω, and the thin film line is connected to the other end of the conduction hole 5. 6 is connected. In the present embodiment, the feeding element 2 and the parasitic element 4 have the same shape, and therefore the connection position of the parasitic element 4 and the conduction hole 5 corresponds to the same position as the feeding point P of the feeding element 2.

The switch 7 can be a high-frequency switch (MMIC) that is a combination of a field effect transistor, a bipolar transistor, a transistor, and the like, and has a high function. In this embodiment, the field effect transistor having the terminal arrangement shown in FIG. 2 is used, the drain terminal is connected to one end of the thin film line 6 with the input terminal as the input terminal, and the ground terminal 3 is connected with the source terminal as the output terminal. A high frequency signal can be passed or blocked by applying a constant DC voltage with the control electrode 8 as a control electrode 8. Although the drain terminal can be used as the output terminal and the source terminal can be used as the input terminal, the antenna of the present invention has a microstrip structure, and therefore, the area (area) where the ground electrode 3 can be formed is considered in consideration of radiation efficiency. Larger is preferable.

FIG. 3 is a graph showing the reflection characteristics at a point where the parasitic element 4 and the conduction hole 5 are connected when the switch 7 is controlled to select between the parasitic element 4 and the ground electrode 3 in a short circuit or open state. .
When the reactance element length L1 determined by the depth of the conduction hole 5 and the length of the thin film line 6 is a half wavelength (λg / 2), the solid line of the graph shown in FIG. It corresponds to when. In the open state, the resonance frequency of the parasitic element 4 is about the same as the operating frequency (about 2 or less when converted to the standing wave ratio), and radio waves are radiated from the parasitic element 4, but in the short-circuit state, there is no The resonance frequency of the feed element 4 changes greatly and deviates from the operating frequency, and radio waves are hardly emitted from the parasitic element 4.
The quarter wavelength (λg / 4) in which the length L1 of the reactance element is shorter than a half wavelength corresponds to the case where the solid line in the graph shown in FIG. 3 is selected as the short circuit state and the broken line as the open state. This is a result opposite to the case when the length L1 of the reactance element is a half wavelength. That is, the resonance frequency of the parasitic element 4 is approximately the same as the operating frequency in the short-circuit state, and radio waves are radiated from the parasitic element 4, but the resonance frequency of the parasitic element 4 changes greatly in the open state. The frequency deviates, and almost no radio wave is radiated from the parasitic element 4.

Therefore, when the length L1 of the reactance element connected to the parasitic element 4 is a half wavelength, the switch 7 is controlled so that the parasitic element 4 and the ground electrode 3 are short-circuited. Is not emitted and the radiation amount of the radio wave from the feed element 2 is overwhelmingly large. Therefore, as shown in FIG. 4A, the main beam of radio waves integrated by the feed element 2 and the parasitic element 4 is Radiated vertically to the surface of the substrate. When the switch 7 is controlled so that the parasitic element 4 and the ground electrode 3 are opened, the radiation amount of the radio wave radiated from the parasitic element 4 corresponds to the radiation amount of the radio wave radiated from the feeder element 2. Since the size cannot be ignored, as shown in FIG. 4B, the main beam of the radio wave integrated by the feed element 2 and the parasitic element 4 has a phase relationship between the feed element 2 and the parasitic element 4 (here, When the phase of the parasitic element 4 is advanced with respect to the feeding element 2), the radiation is radiated from the vertical direction to the horizontal side (right direction in the figure) with respect to the surface of the substrate 1.
When the length L1 of the reactance element is ¼ wavelength, when the switch 7 is controlled to open the space between the parasitic element 4 and the ground electrode 3, as shown in FIG. The main beam of radio waves integrated by the element 4 is radiated in the vertical direction with respect to the surface of the substrate 1. When the switch 7 is controlled so that the parasitic element 4 and the ground electrode 3 are short-circuited, as shown in FIG. 4B, the main beam of the radio wave integrated by the feeder element 2 and the parasitic element 4 is Radiated from the vertical direction to the horizontal direction side (right direction in the figure) with respect to the surface of the substrate 1.

By controlling the switch 7 in this way, the radiation direction of the radio wave beam can be easily changed from the vertical direction to the horizontal direction with respect to the surface of the substrate 1. For this purpose, the connection position and length of the reactance element are appropriately set. Must be set to
The microstrip antenna shown in FIGS. 5A and 5B is similar to the above-described microstrip antenna, in which the feeding element 2 and the parasitic element 4 are provided on the surface of the substrate 1, and the ground electrode 3 is provided on the back surface of the substrate 1, respectively. Although arranged, the thin film line 6 and the switch 7 do not exist. The difference between (a) and (b) is the position of one end of the conduction hole 5 connected to the parasitic element 4. In FIG. 5 (a), the same impedance as that of the feeding point P is 50Ω. In b), one end of the conduction hole 5 is connected to a point near the outer periphery of the parasitic element 4 where the impedance is higher than 50Ω. 5C and 5E are cross-sectional views taken along the line BB ′ of FIG. 5A, and FIGS. 5D and 5F are cross-sectional views taken along the line CC ′ of FIG. 5B.
FIG. 6 is a graph showing the radiation direction of the radio wave beam. CASE 1 is the conduction hole shown in FIG. 5C when the other end of the conduction hole 5 shown in FIG. When the other end of 5 is in an open state with the ground electrode 3, CASE 3 is in the conductive hole shown in FIG. 5E, and when the other end of the conductive hole 5 is in a short circuit state with the ground electrode 3, CASE 4 is in the conductive hole shown in FIG. When the other end of 5 is short-circuited with the ground electrode 3, respectively.

  When CASE1 and CASE2 in which the other end of the conduction hole 5 is in an open state with the ground electrode 3 are compared, the main beam of the radio wave is radiated in the right (+) direction in the figure, but CASE1 is more right in the figure. Although the main beam (main radio wave) is radiated in the (+) direction, it can be seen that the side lobe (unnecessary radio wave) radiated in the left (−) direction in the figure is also increased. Further, when CASE 3 and CASE 4 in which the other end of the conduction hole 5 is short-circuited with the ground electrode 3, the main wave of the radio wave is radiated in the front (0 °) direction in the figure in CASE 4, whereas in CASE 3, It can be seen that the main wave of radio waves is radiated in the left (-) direction in the figure. This occurs due to the difference in the position of one end of the conduction hole 5 connected to the parasitic element 4. Even if the same impedance as the feeding point P is simply short-circuited, the main wave of the radio wave is the front in the figure. This means that it is not radiated in the (0 °) direction, and it is necessary to connect a reactance element having an appropriate length in order to radiate the main beam of radio waves in the front (0 °) direction in the figure.

FIG. 7A shows the radiation shape of the integrated radio wave beam when the length L1 of the reactance element is changed to control the switch 7 so that the parasitic element 4 and the ground electrode 3 are opened. b) shows the radiation shape of the integrated radio wave beam when the parasitic element 4 and the ground electrode 3 are short-circuited.
In the microstrip antenna of the present invention, since the length of the reactance element is set to [λg / 4]) × n (n: integer), the parasitic element 4 and the ground electrode 3 are short-circuited or opened. When the state is selected, the radio wave beam integrated with respect to the substrate surface 1 in either state is emitted in the vertical direction.
The form in which the integrated radio wave beam radiates from the vertical direction to the horizontal direction with respect to the surface of the substrate 1 is radiated as compared with the case where the length L1 of the reactance element is [λg / 4] <L1 <[λg / 2]. The angle can be increased. Compared with when [λg / 2] <L1, the side lobe can be made smaller than the main lobe, and the direction of the moving object can be detected with high accuracy.

The position of the reactance element connected to the parasitic element 4 is 1/10 of the operating frequency from the end of the parasitic element 4 orthogonal to the excitation direction and the end of the parasitic element 4 orthogonal to the excitation direction shown in FIG. It is preferable to connect between the parasitic element 4 and the portion toward the center of the wavelength (λg).
The graph shown in FIG. 9 is a graph showing the change rate of the impedance and the standing wave ratio (VSWR) at the feeding point P of the feeding element 2 when the parasitic element 4 and the ground electrode 3 are switched from the open state to the short-circuit state. is there.
Generally speaking, the 50Ω impedance point of the parasitic element 4 is near 0.17λg from the end face of the parasitic element 4, but the impedance change rate is large at this point. This means that the radiation state (radiation amount / radiation direction) of radio waves is likely to change. The higher the operating frequency, the more accurate the position accuracy of connecting the reactance elements, which greatly affects the quality variation due to manufacturing. To come. The impedance changes between the end of the parasitic element 4 orthogonal to the excitation direction and the portion of the parasitic element 4 from the end of the parasitic element 4 orthogonal to the excitation direction toward the center of 0.15λg of the operating frequency. The ratio is small and suitable as a position to connect the reactance element, but it is also preferable to connect the reactance element to the parasitic element part toward the center of 1 / 10λg, which is less susceptible to manufacturing variations and stable. Performance can be obtained.

As the substrate 1, a glass epoxy substrate with high versatility in which glass cloth is laminated and fixed with an epoxy resin, a high dielectric constant resin substrate in which alumina or titanium powder is mixed, or the like can be used, but if the relative permittivity εr varies greatly, The resonance frequency of the feed element 2 and the parasitic element 4 varies, and the radiation performance of the radio wave beam varies greatly. In order to obtain stable radiation performance, a low dielectric constant resin substrate made of a single material such as fluorine (εr: 2 to 4), a low-temperature fired ceramic substrate mainly composed of glass (εr: 6 to 8), alumina It is preferable to use a substrate having a relatively small variation in relative dielectric constant εr, such as a high-temperature fired ceramic substrate mainly composed of (εr: 8 to 10). Furthermore, considering the manufacturing variation (etching / printing accuracy of the feeding element 2, the parasitic element 4, and the thin film line 6, and the hole machining accuracy at the connection position of the parasitic element 4 and the conduction hole 5), the use frequency is GHz. Since the band is high, it is preferable to use a substrate having a relatively low dielectric constant.
A substrate having a low relative dielectric constant and little variation is often difficult to stack due to the composition structure. However, in the microstrip antenna of the present invention, one end of the conductive hole 5 or the thin film line 6 which is a reactance element is connected to the thin film line 6. Therefore, the switch 7 can be easily arranged on the same surface as the ground electrode 3, and the substrate 1 is formed in a laminated structure to form the ground electrode 2. The surface on which the switch 7 is disposed does not have to be separated.

  In the present embodiment, the parasitic element 4 and the feeding element have the same shape, but need not necessarily be the same. If the resonance frequency of the parasitic element does not change much more than the operating frequency (about 2 or less when converted to the standing wave ratio), the length of one side of the parasitic element parallel to the excitation direction and the direction orthogonal to the excitation direction 1 Can be used even if the length of the side changes slightly.

  In this embodiment, the shape of the conduction hole 5 is a columnar structure, but a cylindrical structure in which the inside is hollow or filled with resin may be used. However, when the frequency is increased, in the case of the cylindrical structure, a non-negligible capacitance component is generated in addition to the reactance component, and thus it is necessary to reduce the diameter (for example, 0.5 mm or less). Naturally, it is difficult to provide the conduction hole 5 only at the point where the impedance of the parasitic element 4 is 50Ω ± 0Ω. Therefore, it is preferable that the size of the conduction hole 5 be as small as possible so that the impedance of the parasitic element 4 includes a point where the impedance is 50Ω.

FIG. 10 is a cross-sectional view showing a first modification of the microstrip antenna shown in the first embodiment.
In the microstrip antenna shown in FIG. 10, a feeding element 2, a parasitic element 4, and a ground electrode 3 are embedded in the substrate 1. The device can be prevented from being damaged due to use or mischief in a poor environment (hot or humid room or area). Moreover, since the feeding element 2 and the parasitic element 4 are arranged three-dimensionally (on different planes), the phase amount changes even if the two-dimensional arrangement distance between the feeding element 2 and the parasitic element 4 is the same. The angle at which the integrated radio beam radiates from the vertical direction to the horizontal direction with respect to the substrate surface 1 can be adjusted.

FIG. 11 is a plan view showing a second embodiment of the microstrip antenna of the present invention.
Hereinafter, description of the same parts as those in the first embodiment will be omitted.
The microstrip antenna shown in FIG. 11 is branched from a feeding point P having an impedance of 50Ω to a transmission line having an impedance of 100Ω, and feeding elements 2a and 2b are connected to both ends thereof so that a high-frequency signal is propagated in the same phase. Yes. Therefore, since the area of the element to be fed increases, the beam direction can be switched and the detection distance can be extended while the radio wave beam is narrowed down.
Further, the impedance of each connection portion to which the transmission lines of the feeding elements 2a and 2b are connected is 100Ω. On the other hand, the conduction hole 5 of the parasitic element 4 is connected to the same 50Ω point as the microstrip antenna of FIG. Thus, the connection position of the parasitic element 4 and the conduction hole 5 does not necessarily have to be at the same position as the feeding point P of the feeding element, and the reactance element is positioned at the position of the parasitic element that substantially matches the impedance of the thin film line 6. It is sufficient that one end is connected.

FIG. 12 shows a third embodiment of the microstrip antenna of the present invention, (a) a plan view seen from the front, and (b) a plan view seen from the back.
The microstrip antenna of FIG. 12 includes an insulating substrate 1, a feed element 2 to which a high-frequency signal is fed, a ground electrode 3 that acts as a ground for the high-frequency signal, and a plurality of parasitic feeds that are excited by the feed element 2. When a constant DC voltage is applied to the control electrodes 8a and 8b as switching means for enabling selection of a short circuit or open state between the elements 4a and 4b, the parasitic elements 4a and 4b, and the ground electrode 3, Switches 7a and 7b to be cut off, conduction holes 5a and 5b arranged inside the substrate 1 as reactance elements for propagating high-frequency signals from predetermined positions of the parasitic elements 4a and 4b to the switches 7a and 7b, The thin film lines 6a and 6b are distributed constant circuits arranged on the surface.
The feeding element 2 and the parasitic elements 4a and 4b have the same shape, and a predetermined interval is provided at a symmetrical position on the same plane around the feeding element 2 on the surface of the substrate 1 facing the ground electrode 3 through the substrate 1. It is arranged. Accordingly, the excitation directions of the parasitic elements 4a and 4b are the same as those of the feeder element 2, and the phases are also substantially the same. Switches 7a and 7b are arranged on the back surface of the substrate 1 on which the ground electrode 3 is formed, and the parasitic elements 4a and 4b and the input ends of the switches 7a and 7b are connected by the conduction holes 5a and 5b and the thin film lines 6a and 6b. The output terminals of the switches 7a and 7b are connected to the ground electrode 3.

In the microstrip antenna shown in FIG. 12, when the length L1 of the reactance element is a half wavelength (λg / 2), the switches 7a and 7b are controlled so that the parasitic elements 4a and 4b and the ground electrode 3 are short-circuited. As shown in FIG. 13A, the main beam of the radio wave integrated by the feeding element 2 and the parasitic elements 4a and 4b emits almost no radio wave from the parasitic elements 4a and 4b. Is radiated in the vertical direction with respect to the surface of the substrate 1. When the switches 7a and 7b are controlled so that the parasitic element 4a and the ground electrode 3 are in an open state and the parasitic element 4b and the ground electrode 3 are short-circuited, as shown in FIG. 2 and the parasitic elements 4a and 4b are integrated into the main beam of the radio wave, and the radiation amount of the radio wave from the parasitic element 4a is not negligible with respect to the radiation amount of the radio wave of the feed element 2. 2 and the parasitic element 4a (a state in which the phase of the parasitic element 4a is advanced with respect to the feeder element 2) radiates from the vertical direction to the horizontal side (right direction in the figure) with respect to the surface of the substrate 1.
When the parasitic element 4a and the ground electrode 3 are short-circuited and the parasitic element 4b and the ground electrode 3 are opened, the main wave of the radio wave integrated by the feeder element 2 and the parasitic elements 4a and 4b is Radiated in the left direction in the figure.
When the length L1 of the reactance element is ¼ wavelength (λg / 4), the radiation state of the radio waves from the parasitic elements 4a and 4b when the parasitic elements 4a and 4b and the ground electrode 3 are short-circuited or opened. If the switches 7a and 7b are controlled in the same way, the radiation direction of the integrated radio wave beam changes in the same way.
Thus, the microstrip antenna of the present invention can easily switch the direction of the radio wave beam symmetrically from the front direction, from the front direction to the left direction, and from the front direction to the right direction.

14A is a plan view seen from the front, and FIG. 14B is a plan view seen from the back, showing a modified example 1 of the microstrip antenna shown in the second embodiment.
In the microstrip antenna shown in FIG. 14, one end of the thin film lines 6c and 6d is connected to the parasitic elements 4a and 4b, and the other end is connected to the conduction holes 5a and 5b. Accordingly, it is not necessary to remove the ground electrode corresponding to the portion immediately below the parasitic elements 5a and 5b, and a decrease in radiation efficiency can be suppressed. In the first modification, the lengths of the thin film lines 6a, 6b, 6c, and 6d are uniform, but the length of the reactance element determined by the thin film lines 6a, 6c and the conduction hole 5a is [λg / 4]. ) × n (n: integer), it can be arbitrarily adjusted.
Further, as in the microstrip antenna shown in FIG. 15, the impedance of the thin film lines 6c and 6d is changed to be higher (the width W1 is made thinner), and the positions of the thin film lines 6c and 6d connected to the parasitic elements 4a and 4b are not changed. If it changes to the point from the outline of feeder element 4a, 4b, the fall of radiation efficiency can be controlled further.

FIG. 16 is a fourth embodiment of the microstrip antenna of the present invention, (a) a plan view seen from the front, and (b) a plan view seen from the back.
There are a plurality of points having the same impedance in the parasitic element at symmetrical positions with respect to the center point of the parasitic element, and not one.
In the microstrip antenna shown in FIG. 16, the conduction holes 5 a and 5 b connected to the parasitic elements 4 a and 4 b are arranged at point-symmetrical positions with respect to the feeding element 2. However, since the conduction holes 5a and 5b are connected at positions where the parasitic elements 4a and 4b have the same impedance, the same operation and effect as the microstrip antenna shown in FIG. 12 can be obtained by controlling the switches 7a and 7b. . Further, it is easy to downsize the substrate 1 by bending the thin film lines 6a and 6b.

17A is a plan view seen from the front, and FIG. 17B is a plan view seen from the back, showing Modification 1 of the microstrip antenna shown in the fourth embodiment.
In the microstrip antenna shown in FIG. 17, the parasitic elements 4 a and 4 b are arranged symmetrically at positions on the extension line corresponding to the excitation direction of the feeder element 2. The excitation directions of the parasitic elements 4a and 4b are the same as those of the feeder element 2. However, since the feeding point P of the feeding element 2 is not located at the center of the feeding element 2, the parasitic elements 4a and 4b are slightly excited. Although different, the radiation amount and phase of radio waves radiated from the parasitic elements 4a and 4b are not extremely shifted. As a means for making the radiation amount and phase of the radio waves radiated from the parasitic elements 4a and 4b the same, the resonance frequency may be shifted by changing the shape of one of the parasitic elements 4a and 4b. Specifically, the length of one side orthogonal to the excitation direction is changed. Since the conduction holes 5a and 5b connected to the parasitic elements 4a and 4b are arranged at symmetrical positions with respect to the feeder element 2, the thin film lines 6a and 6b are formed on the ground electrode 3 corresponding to the position immediately below the feeder element 2. Further, since it is possible to avoid arranging the switches 7a and 7b, the thin film lines 6a and 6b and the switches 7a and 7b can be arranged on the same surface as the ground electrode 3, so that the design can be simplified and the manufacturing cost can be reduced.
Reduction in efficiency can be suppressed.

FIG. 18 is a plan view of a fifth embodiment of the microstrip antenna of the present invention as seen from the front.
The microstrip antenna shown in FIG. 18 is branched from a feeding point P having an impedance of 50Ω to a transmission line having an impedance of 100Ω, and feeding elements 2a and 2b are connected to both ends thereof. However, since the lengths of the transmission lines from the feed point P to the feed elements 2a and 2b are different, the phases of the high-frequency signals propagated to the feed elements 2a and 2b are different. In the present embodiment, the phase of the feed element 2a having a short distance from the feed point P is more advanced than the phase of the feed element 2b.
Accordingly, the switches 7a and 7b (not shown) connected to the parasitic elements 4a and 4b via the conduction holes 5a and 5b are controlled to short-circuit or open the parasitic elements 4a and 4b and the ground electrode 3 (not shown). In this case, the integrated radio wave beam is radiated toward the feeding element 4b whose phase is delayed. Then, by setting one of the parasitic elements and the ground electrode 3 to a short circuit or an open state, a radio wave is radiated in the left or right direction in the figure with the previous direction as a reference. As described above, the direction of the radio wave beam can be easily switched on the basis of the direction deviated from the vertical direction of the substrate surface in advance, and the design is easy.

  The above-described microstrip antenna according to the present invention can be applied to a high-frequency sensor for detecting an object. Such a high-frequency sensor receives a transmitting antenna using a microstrip antenna, a receiving antenna for receiving a reflected wave or transmitted wave from a radio wave object output from the transmitting antenna, and an electric signal from the receiving antenna. And a processing circuit for processing. Here, although the receiving antenna can be provided separately from the transmitting antenna, the transmitting antenna can also be used as the receiving antenna, particularly when a reflected wave is received.

  As mentioned above, although embodiment of this invention was described, this embodiment is only the illustration for description of this invention, and is not the meaning which limits the scope of the present invention only to this embodiment. The present invention can be implemented in various other modes without departing from the gist thereof.

It is the top view and sectional drawing in 1st Embodiment of the microstrip antenna of this invention. It is the schematic which shows the terminal function of a switch similarly. It is a graph explaining a radio wave scanning principle. It is a perspective view explaining a radio wave scanning principle. It is the top view and sectional drawing explaining the radiation | emission direction of the electromagnetic wave by a connection position about the connection of the reactance element and parasitic element which comprise the microstrip antenna of this invention. It is a graph explaining the radiation | emission direction of the electromagnetic wave by a connection position similarly. It is a graph explaining the length of a reactance element similarly. It is a top view explaining the relationship of a connection position similarly. It is a graph explaining the radio | wireless radiation amount by a connection position similarly. It is sectional drawing which shows the modification 1 similarly. It is a top view in 2nd Embodiment of the microstrip antenna of this invention. It is a top view in 3rd Embodiment of the microstrip antenna of this invention. It is a perspective view explaining a radio wave scanning principle. It is a top view which shows the modification 1 similarly. It is a top view which shows the modification 2 similarly. It is a top view in 4th Embodiment of the microstrip antenna of this invention. It is a top view which shows the modification 1 similarly. It is a top view in 5th Embodiment of the microstrip antenna of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2, 2a, 2b Feeding element 3, Ground electrode 4, 4a, 4b Parasitic element 5, 5a, 5b Conduction hole 6, 6a, 6b, 6c, 6d Thin film line 7, 7a, 7b Switch 8, 8a, 8b Control electrode

Claims (15)

A substrate,
A feed element to which a high-frequency signal is fed;
It consists of a ground electrode that acts as a ground for high-frequency signals,
In the microstrip antenna in which the feeding element is disposed at a position facing the ground electrode through the substrate,
A parasitic element disposed at a position facing the ground electrode and excited by the feeding element;
The grounding electrode and a switching means capable of selecting a short circuit or an open state, and
When the parasitic element is selected to be short-circuited or opened with respect to the ground electrode by the switching means, the main beam of the integrated radio wave is selected in the vertical direction with respect to the substrate surface in the selected state. In a state, the microstrip antenna radiates from a vertical direction to a horizontal direction with respect to the substrate surface. A substrate,
A feed element to which a high-frequency signal is fed;
It consists of a ground electrode that acts as a ground for high-frequency signals,
In the microstrip antenna in which the feeding element is disposed at a position facing the ground electrode through the substrate,
A plurality of parasitic elements which are arranged at positions facing the ground electrode and are excited by the feeding elements;
Each parasitic element includes the ground electrode and switching means capable of selecting a short circuit or an open state,
Each parasitic element is arranged at a symmetrical position on the same plane with the feeding element as the center, and is integrated when all the parasitic elements are selected to be shorted or opened with the ground electrode by the switching means. When the main beam of radio waves is perpendicular to the substrate surface and at least one of the parasitic elements is different from the selected state of the other parasitic elements, the radiation is emitted from the vertical direction to the horizontal direction with respect to the substrate surface. A microstrip antenna. The microstrip antenna according to claim 1 or 2, wherein a plurality of the feeding elements are arranged. A substrate,
A plurality of power feeding elements in which at least one power feeding element is fed with a phase in which a high-frequency signal is different from that of other power feeding elements;
It consists of a ground electrode that acts as a ground for high-frequency signals,
In the microstrip antenna in which a plurality of the feeding elements are arranged at positions facing the ground electrode through the substrate,
A parasitic element disposed at a position facing the ground electrode and excited by a plurality of the feeding elements,
The grounding electrode and a switching means capable of selecting a short circuit or an open state, and
When the parasitic element is selected to be short-circuited or opened with respect to the ground electrode by the switching means, the main beam of the integrated radio wave is in phase with respect to the substrate surface in one selected state. The micro beam radiates in a predetermined direction in which the feeding element whose phase is delayed from the position where the element is disposed, and emits in a direction inclined by a predetermined angle from the predetermined direction in the other selected state. Strip antenna. A substrate,
A plurality of power feeding elements in which at least one power feeding element is fed with a phase in which a high-frequency signal is different from that of other power feeding elements;
It consists of a ground electrode that acts as a ground for high-frequency signals,
In the microstrip antenna in which a plurality of the feeding elements are arranged at positions facing the ground electrode through the substrate,
A parasitic element disposed at a position facing the ground electrode and excited by a plurality of the feeding elements,
Each parasitic element includes the ground electrode and switching means capable of selecting a short circuit or an open state,
Each parasitic element is arranged at a symmetrical position on the same plane with a plurality of the feeding elements as the center, and is integrated when all the parasitic elements are selected to be shorted or opened with the ground electrode by the switching means. The main beam of the emitted radio wave radiates in a predetermined direction where the feeding element whose phase is delayed from the position where the feeding element whose phase is advanced with respect to the substrate surface is arranged, and the parasitic element of the parasitic element When at least one of the microstrip antennas radiates in a direction inclined by a predetermined angle from the predetermined direction when at least one of the parasitic elements is different from the selected state. The switching means is
A switch that passes or blocks high-frequency signals;
It consists of a reactance element that propagates high-frequency signals,
One end of the reactance element is connected to a predetermined position of the parasitic element, the other end of the reactance element is connected to an input terminal of the switch, an output terminal of the switch is connected to the ground electrode, and the switch is connected to a certain direct current. 6. The microstrip antenna according to claim 1, wherein when a voltage is applied, the parasitic element and the ground electrode are short-circuited or opened. The microstrip antenna according to claim 6, wherein the switch is disposed on the same plane as the ground electrode. The reactance element is
A conduction hole disposed inside the substrate;
It is composed of a thin film line consisting of a distributed constant circuit arranged on the surface or inside of the substrate,
The microstrip antenna according to claim 6 or 7, wherein one end of the conduction hole and one end of the thin film line are connected. The length of the reactance element is:
9. The microstrip antenna according to claim 6, wherein [λg / 4]) × n (λg: wavelength on substrate, n: integer). 10. The microstrip antenna according to claim 6, wherein one end of the reactance element is connected to a position on the parasitic element that matches an impedance of the thin film line. One end of the reactance element includes an end side of the parasitic element orthogonal to the excitation direction and the parasitic element from the end side of the parasitic element orthogonal to the excitation direction toward a central portion of 1/10 wavelength of the operating frequency. The microstrip antenna according to any one of claims 6 to 9, wherein the microstrip antenna is connected between the first and second parts. The microstrip antenna according to any one of claims 6 to 11, wherein at least one of the parasitic elements is different in position of the reactance element connected to the other parasitic elements. The microstrip antenna according to any one of claims 8 to 12, wherein the impedance of the thin film line is 50Ω. 14. The microstrip antenna according to claim 1, wherein the feed element and the parasitic element have the same length of one side in the excitation direction. A high frequency sensor comprising the microstrip antenna according to claim 1.

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