JP5664183B2 - Variable directional antenna device - Google Patents

Description

  The present invention relates to a variable directivity antenna device, and more particularly to a technique for setting the directivity of an antenna.

  An apparatus that detects the direction of arrival of radio waves from a wireless terminal by changing the directivity of a variable directivity antenna is known (for example, Patent Document 1). The apparatus of Patent Document 1 includes an array antenna whose directivity changes as a variable directivity antenna by changing reactance values of variable reactance elements respectively connected to a plurality of non-excitation elements. Then, while changing the directivity of the array antenna, a radio signal whose arrival direction is unknown is received, and the radio wave arrival direction is detected based on the power value of the unknown radio signal for each directivity.

Japanese Patent No. 3836080

  In the thing of patent document 1, the arrangement environment is not considered in the reactance value for setting the directivity of an array antenna. However, when a fixed type device is considered, the device may be placed at a position where a wall that reflects radio waves is close to the antenna, or at a position where such a wall does not exist. May be arranged.

  Even if there is a wall that reflects radio waves around the variable directional antenna, if the same reactance value set as when there is no wall is used, there is no influence from the wall due to the influence of the reflection from the wall. A strong side lobe may occur at an angle where no occurrence occurs. Then, due to the presence of the side lobes, there is a possibility that the existence direction of the wireless terminal is erroneously detected.

  On the other hand, even if there is no wall that reflects radio waves around the variable directional antenna, even if the same reactance value set as that in the case where a wall exists is used, appropriate directivity cannot be obtained.

  The present invention has been made based on this situation, and an object of the present invention is to provide a variable directional antenna device capable of obtaining good directivity regardless of the influence of surrounding walls. It is in.

In order to achieve the object, the first , third, and fourth aspects of the invention include an array antenna whose directivity changes by changing the reactance value of the variable reactance element. In addition, the storage unit stores reactance value sets each composed of reactance values corresponding to the variable reactance elements for each directivity, and the reactance value set depends on the influence of the wall for each directivity. In order to obtain good directivity, a plurality of sets corresponding to a plurality of installation environments having different distances to the wall are stored. Then, the reactance value setting unit selects one set from the plurality of reactance value sets stored in the storage unit and sets the reactance value. Therefore, it is possible to select a reactance value set according to the distance to the wall in the environment where it is actually installed, so that good directivity can be obtained regardless of the influence of surrounding walls.

In addition, according to the first aspect of the present invention, the storage unit includes, for each directivity, a reactance value set when the wall exists at a distance affecting the directivity and a reactance when the wall does not exist at the affected distance. A value set is stored. In addition, a wall determination unit that determines whether or not a wall exists at a distance that affects directivity is provided. The reactance value setting unit sets a reactance value set according to the determination result of the wall determination unit. Therefore, a reactance value set corresponding to the influence of the wall can be automatically set. In addition, by providing the wall determination unit in this way, it is determined whether or not a wall that reflects radio waves and affects directivity is determined, not whether or not there is a wall that can be visually recognized by humans. Therefore, there is also an advantage that the reactance value set can be set more appropriately.

Unlike the invention according to claim 1 , the reactance value set may be set by manual operation. In this case, an operator performs an operation for instructing the reactance value setting unit to set which reactance value set, and the reactance value setting unit is configured to react the reactance value based on the instruction from the operation unit. Set the value set.

In the invention according to claim 2, in a state in which the reactance value set is set so that the main lobe faces in the wall detection direction set in advance as the direction in which the presence or absence of the wall is detected, the transmission power transmitted from the array antenna, A power ratio calculation unit for calculating a power ratio with the received power received by the array antenna is provided. When a wall actually exists in the wall detection direction, the received power increases due to reflection by the wall, and when there is no wall, the received power decreases. Therefore, the value of the power ratio between the transmission power and the reception power differs greatly depending on whether or not there is a wall. Therefore, the wall determination unit can determine whether a wall exists at a distance that affects directivity based on the power ratio calculated by the power ratio calculation unit.

In the invention according to claim 3 , the storage unit stores three or more reactance value sets respectively corresponding to installation environments having different distances to the wall for each directivity. In addition, the first power ratio calculation unit sets a transmission power to be transmitted from the array antenna in a state where a reactance value set in which the main lobe faces in the wall detection direction set in advance as the direction in which the presence or absence of the wall is detected, and A first power ratio, which is a power ratio with the received power received by the array antenna, is calculated. In addition, the second power ratio calculation unit sets the transmission power transmitted from the array antenna and the array antenna in a state where the reactance value set in which the main lobe faces in a direction shifted by a predetermined angle with respect to the wall detection direction is set by the array antenna. A second power ratio, which is a power ratio with the received power received, is calculated.

  Since the received power becomes weaker as the distance to the wall increases, the power ratio between the transmitted power and the received power tends to change according to the distance to the wall. However, this power ratio does not simply change according to the distance to the wall, but has a periodicity based on the wavelength period. Therefore, the distance to the wall cannot be accurately calculated with only one power ratio. However, in the present invention, the power ratio difference calculation means calculates the power ratio difference that is the difference between the first power ratio and the second power ratio. Since the two power ratios both include periodic fluctuations based on the same wavelength period, the power ratio difference has less periodic fluctuations based on the wavelength period. Thus, the power ratio difference corresponds to the distance to the wall. Further, the relationship between the power ratio difference and the distance to the wall can be determined in advance based on experiments, and the relationship between the distance to the wall and the reactance value set can also be stored in advance. .

  Accordingly, the reactance value setting unit sets the reactance value set from the previously stored relationship in which the reactance value set is determined in advance based on the power ratio difference and the actual power ratio difference. In this way, a reactance value set according to the distance to the wall can be set, so that good directivity can be obtained regardless of the influence of the wall.

  The previously stored relationship in which the reactance value set is determined in advance based on the power ratio difference is not limited to the relationship in which the power ratio difference and the reactance value set directly correspond to each other, and the relationship between the power ratio difference and the distance to the wall. The relationship between the distance to the wall and the reactance value set may be two relationships.

In the invention according to claim 4 , the storage unit stores three or more reactance value sets respectively corresponding to installation environments having different distances to the wall for each directivity. In addition, the transmission control unit changes the transmission frequency to a plurality of values in each transmission frequency in a state where a reactance value set in which the main lobe faces in the wall detection direction set in advance as the direction in which the presence or absence of the wall is detected is set. A signal is transmitted from the array antenna. The power ratio calculation unit calculates a power ratio that is a ratio between the transmission power transmitted from the array antenna and the reception power received by the array antenna at each transmission frequency .

  The wavelength also changes due to the change in the transmission frequency, and the wavelength portion reflected on the wall changes due to the change in wavelength. For this reason, the received power changes due to the change in frequency, and the power ratio between the transmission power and the received power also changes due to the change in the received power. Further, the distance to the wall also affects the wavelength portion reflected on the wall. Therefore, the change tendency of the power ratio with respect to the change of the transmission frequency shows a different change tendency depending on the distance to the wall.

  Therefore, the reactance value setting unit is configured so that the reactance value set is determined based on the change tendency of the power ratio with respect to the change of the transmission frequency, and the change tendency of the power ratio actually calculated by the power ratio calculation unit with respect to the transmission frequency. Based on the above, a reactance value set is set. In this way, a reactance value set according to the distance to the wall can be set, so that good directivity can be obtained regardless of the influence of the wall.

It is a block diagram of the radio | wireless terminal direction detection apparatus of 1st Embodiment. It is a figure which defines the direction of directivity in a 1st embodiment. It is a flowchart which shows the wall judgment process which the variable reactance control part 61 performs. It is a figure which shows the relationship between the reactance value set and the directivity in an actual installation environment. It is a figure which shows the structure of the direction detection computer 6 in 2nd Embodiment. It is a figure which shows the relationship between the back direction which is the directivity from which a 1st power ratio is calculated, and the direction which shifted | deviated 30 degrees from the back which is the directivity direction from which a 2nd power ratio is calculated. It is a figure which shows an example of the relationship between the distance to a wall, and a power ratio difference. It is a figure which shows the structure of the direction detection computer 6 in 3rd Embodiment. It is the figure which showed notionally the relationship between the distance to the wall of a back surface, and a power ratio about three frequencies (2300, 2400, 2500 MHz). It is a figure which shows the change tendency of the power ratio with respect to the change of a transmission frequency in three distances (61 mm, 91.5 mm, 122 mm).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a wireless terminal direction finding device according to the first embodiment. This wireless terminal direction finding device has a function as a variable directivity antenna device of the present invention, and directivity of an array antenna 1 is shown. Is received, a radio signal from a radio terminal (not shown) (for example, a radio tag) is received, and the arrival direction of the radio signal is estimated.

  As shown in FIG. 1, the wireless terminal direction finding device includes an array antenna 1, a transmitter 3, a circulator 4, a power detection circuit 5, and a direction finding computer 6.

  The array antenna 1 includes one excitation element 10 and six non-excitation elements 11 to 16 provided at equal intervals on a circumference centered on the excitation element 10. Each of these is a straight bar shape, and the length thereof is, for example, about λ / 4.

  The excitation element 10 and the non-excitation elements 11 to 16 are provided on the ground conductor 17 so as to be insulated from the ground conductor 17. The ground conductor 17 has a sufficiently large area (for example, radius λ / 2) with respect to the excitation element 10 and the non-excitation elements 11 to 16.

  The feeding point of the excitation element 10 is connected to the transmitter 3 and the circulator 4 via the coaxial cable 19. Variable reactance circuits 18A to 18F are connected to the non-excitation elements 11 to 16, respectively. The variable reactance circuit 18 is the same circuit as that generally used in an electronically controlled waveguide array antenna apparatus. For example, a variable reactance element (for example, a variable reactance element) whose reactance value changes when a bias voltage is applied. A circuit including a capacitor diode). This circuit is connected to the ground conductor 17 at a high frequency, and the reactance value is electronically changed by a variable reactance control unit 61 (to be described later) of the direction detection computer 6. By changing the reactance value, the directivity of the array antenna 1 changes.

  The transmitter 3 is connected to the direction finding computer 6 and the circulator 4. The transmitter 3 includes a modulation unit and an amplification unit inside (not shown), modulates and amplifies a signal supplied from the direction detection computer 6, and outputs a signal having a predetermined power. The signal output from the transmitter 3 is supplied to the excitation element 10 via the circulator 4 and the coaxial cable 19 and is transmitted from the excitation element 10 as a radio signal.

  The circulator 4 guides the signal from the transmitter 3 to the array antenna 1 and guides the signal from the array antenna 1 to the power detection circuit 5. The power detection circuit 5 is a circuit that detects the magnitude (power value) of the received signal received by the array antenna 1 and supplied via the circulator 4. As the power detection circuit 5, various known circuits for detecting the power of the radio signal can be used. For example, the power detection circuit 5 has a circuit configuration including a diode detector. A power value signal indicating the power value detected by the power detection circuit 5 is supplied to the direction detection computer 6 via an AD conversion circuit (not shown).

  The direction detection computer 6 includes a CPU, a ROM, a RAM, and the like (all not shown), and the CPU detects a direction by executing a program stored in the ROM while using a temporary storage function of the RAM. The computer 6 functions as a variable reactance control unit 61, a communication control unit 62, and a direction detection unit 63. In addition, the direction detection computer 6 includes a storage unit 65.

  The storage unit 65 is a nonvolatile memory such as an EEPROM, and stores a plurality of reactance value sets including reactance values respectively corresponding to the variable reactance elements provided in the variable reactance circuits 18A to 18F. The plurality of reactance value sets respectively correspond to a plurality of directions in which the directivity of the array antenna 1 is directed within the direction detection range in which the direction detection of the wireless terminal is performed. In the present embodiment, the direction detection range is a range of 180 ° from 90 ° to 270 °, and the direction in which the directivity of the array antenna 1 is directed is a direction for each step angle of 30 ° from 90 ° to 270 °. It is. That is, a reactance value set that stores directivity in the directions of 90 °, 120 °, 150 °, 180 °, 210 °, 240 °, and 270 ° is stored.

  Further, for each directivity, the reactance value set stores a set when there is a wall on the back surface and a set when there is no wall on the back surface. FIG. 2 is a diagram for determining the direction of directivity in the first embodiment. In the present embodiment, the back means the 0 ° direction shown in FIG. In FIG. 2, circles whose numbers are shown indicate the excitation element 10 or the non-excitation elements 11 to 16.

  The direction of 0 ° is the center of the range where direction detection is not performed, and is a direction determined by the arrangement of the array antenna 1 in a housing (not shown) of the present apparatus. Further, the storage unit 65 also stores a reactance value set for directing directivity in the back direction. The reactance values in these reactance value sets are all determined based on experiments.

  The variable reactance control unit 61 performs a wall determination process for determining whether there is a wall on the back surface. Therefore, the variable reactance control unit 61 functions as a wall determination unit in the claims. Whether or not there is a wall on the back does not consider the distance to infinity but determines whether the wall exists at a distance that affects directivity. The details of the wall determination process will be described later with reference to FIG. The variable reactance control unit 61 also performs reactance value setting processing when detecting the direction of the wireless terminal. In this reactance value setting process, based on the determination result of whether or not there is a wall on the back surface, a set when there is a wall on the back surface from among a plurality of reactance value sets stored in the storage unit 65, or Choose one of the sets when there is no wall on the back. Then, the directivity is sequentially changed for each step angle within the direction detection range. Since the reactance value setting process is performed, the variable reactance control unit 61 also functions as a reactance setting unit in the claims.

  The communication control unit 62 controls the transmitter 3 and causes the transmitter 3 to transmit a signal having a predetermined transmission power according to an instruction from the variable reactance control unit 61. The direction detection unit 63 sequentially acquires the directivity of the array antenna 1 from the variable reactance control unit 61 and the power value from the power detection circuit 5 when the variable reactance control unit 61 performs the reactance value setting process. . And based on them, the power value for every directivity is determined, and the directivity direction which showed the maximum power value is determined to the direction where a radio | wireless terminal exists.

  FIG. 3 is a flowchart showing wall determination processing executed by the variable reactance control unit 61. The process shown in FIG. 3 is started by a process start instruction operation by the user, for example. The array antenna 1 is fixed at a predetermined installation position, and the wall determination process is executed only once when installed at the installation position.

  In FIG. 3, in step S1, directivity is directed in the back direction. More specifically, a reactance value set for directing directivity in the back direction is acquired from the storage unit 65, and a reactance value included in the acquired reactance value set is set for each variable reactance element.

  In subsequent step S2, the communication control unit 62 is instructed to transmit a signal having a predetermined power from the transmitter 3. In subsequent step S3, the received power detected by the power detection circuit 5 is acquired. In step S4, a power ratio (reception power / transmission power) between the transmission power transmitted in step S2 and the reception power acquired in step S3 is calculated. Since the power ratio is calculated in step S4, the variable reactance control unit 61 also functions as a power ratio calculation unit.

  In a succeeding step S5, it is determined whether or not the power ratio calculated in the step S4 is larger than a preset threshold value X. When there is a wall in the rear direction, the received power increases due to reflection by the wall. Therefore, when there is a wall in the back direction, the power ratio becomes large. The threshold value X is set in advance based on experiments so that the power ratio that varies depending on the presence or absence of walls can be distinguished. Therefore, when step S5 is affirmative determination, it determines with a wall in a back surface in step S6. In the subsequent step S7, it is determined that the reactance value set when there is a wall on the back is selected as the reactance value set.

  On the other hand, when step S5 is negative determination, it progresses to step S8 and determines that there is no wall in a back surface. In step S9, it is determined that the reactance value set when there is no wall on the back is selected as the reactance value set.

  FIG. 4 is a diagram showing the relationship between the reactance value set and the directivity in the actual installation environment. More specifically, FIG. 4 shows the actual installation environment for each of the case of using the reactance value set when there is no wall in the rear direction and the case of using the reactance value set when there is a wall in the rear direction. FIG. 5 is a diagram showing the result of simulating directivity when there is a wall in the back direction and when there is no wall in the back direction. FIG. 4 shows a case where a reactance value set for directing directivity in the 270 ° direction is used.

  Specific values of the reactance value set are determined based on experiments, and an outline of the reactance value will be described below. The reactance value set for directing the directivity in the direction of 270 ° is the reactance value of each of the two non-excited elements 11, 14, 15, and 16 centering on the direction in which the directivity is to be directed, in the case where there is no wall. Is set to a small value (for example, 0.5 pF) to behave as a director. On the other hand, the reactance value for the remaining non-excited elements 12 and 13 is set to a large value (for example, 20 pF) to behave as a reflector. In addition, in the case where there is a wall, in addition to the non-exciting elements 12 and 13, the non-exciting elements 11 and 14 in the direction perpendicular to the wall also behave as reflectors.

  When the reactance value for the wallless is used, and the actual installation environment has no wall, as shown in FIG. It has become. However, when there is a wall 70 in the back direction, even if the same reactance value is used, as shown in FIG. 5B, due to the influence of reflection from the wall, the direction is 180 ° (front direction of the wall). A large side lobe is produced.

  When the reactance value for the wall is used and the wall 70 exists even in the actual installation environment, the main lobe is oriented in the direction of about 270 ° as shown in FIG. The directivity is good. However, when there is no wall in the back direction, even if the same reactance value is used, the beam width becomes large as shown in FIG.

  Therefore, in the first embodiment described above, the reactance value set is stored in the storage unit 65, and two types corresponding to the case where there is a wall on the back surface and the case where there is no wall are stored for each directivity. Then, the variable reactance control unit 61 actually determines whether or not there is a wall in the back direction, and according to the determination result of the presence or absence of the wall from the two types of reactance value sets stored in the storage unit 65. Select a reactance value set. Thus, since the reactance value set is selected depending on whether or not there is a wall in the back direction in the environment where it is actually installed, good directivity can be obtained regardless of the presence or absence of the back wall. It becomes like this.

  In the first embodiment, the variable reactance control unit 61 determines whether or not there is a wall in the back direction, and the reactance value is set according to the determination result. That is, the reactance value set according to the presence or absence of walls is automatically set. Therefore, since it is determined whether there is a wall that reflects radio waves and affects directivity, not whether or not there is a wall that can be visually recognized by humans, it is possible to select an appropriate reactance value set. it can.

  Next, a second embodiment will be described. The second embodiment differs from the first embodiment in the function of the variable reactance control unit 61 of the direction detection computer 6 and the storage content of the storage unit 65, and the other configurations are the same as those in the first embodiment.

  FIG. 5 is a diagram showing a configuration of the direction detection computer 6 in the second embodiment. Also in the second embodiment, the storage unit 65 stores reactance value sets respectively corresponding to a plurality of directions in which the directivity of the array antenna 1 is directed within the direction detection range in which the direction detection of the wireless terminal is performed. However, in the second embodiment, for each directivity, reactance value sets respectively corresponding to three or more installation environments having different distances to the back wall are stored. The storage unit 65 also stores a reactance value set for directing directivity in the back direction, a reactance value set in which directivity is directed in a direction shifted by 30 ° from the back surface, and the distance to the wall and power The relationship with the ratio difference is also stored. The relationship between the distance to the wall and the power ratio difference will be described in detail later.

  The variable reactance control unit 61 includes a first power ratio calculation unit 611, a second power ratio calculation unit 612, a power ratio difference calculation unit 613, and a reactance value setting unit 614. The reactance value setting unit 614 detects the distance to the back wall, and selects a reactance value set corresponding to the distance to the back wall from the plurality of reactance value sets stored in the storage unit 65.

  In the process of detecting the distance to the back wall, first, a reactance value having directivity in the back direction which is the wall detection direction is set. Then, the communication controller 62 is instructed to transmit a signal having a predetermined power from the transmitter 3. Also, the first power ratio calculation unit 611 is caused to calculate the first power ratio.

  The first power ratio calculation unit 611 acquires received power from the power detection circuit 5 based on an instruction from the reactance value setting unit 614, and the first power ratio (received power / transmitted power) is calculated from the received power and the transmitted power. Is calculated. Then, the calculated first power ratio is sent to the power ratio difference calculation unit 613.

  Furthermore, the reactance value setting unit 614 sets a reactance value that has directivity in a direction shifted by 30 ° from the back surface. Then, the communication controller 62 is instructed to transmit a signal having a predetermined power from the transmitter 3. Further, the second power ratio calculation unit 612 is caused to calculate the second power ratio.

  The second power ratio calculation unit 612 acquires received power from the power detection circuit 5 based on an instruction from the reactance value setting unit 614, and a second power ratio (received power / transmitted power) is obtained from the received power and the transmitted power. Is calculated. Then, the calculated second power ratio is sent to the power ratio difference calculation unit 613.

  The power ratio difference calculation unit 613 calculates a power ratio difference that is a difference between the first power ratio and the second power ratio. Then, the calculated power ratio difference is sent to the reactance value setting unit 614. Here, this power ratio difference will be described.

  FIG. 6 is a diagram showing the relationship between the back direction, which is the directivity in which the first power ratio is calculated, and the direction shifted by 30 ° from the back, which is the directivity direction, in which the second power ratio is calculated. As can be seen from FIG. 6, the distance to the wall is longer in the direction shifted by 30 ° from the back direction than in the back direction. Therefore, the received power is lower than that in the rear direction. Moreover, the power ratio (reception power / transmission power in this embodiment) also decreases due to a decrease in reception power. However, the power ratio does not simply decrease according to the distance to the wall, but there is periodicity based on the wavelength period as shown in FIG. Therefore, the distance to the wall cannot be accurately calculated only by the first power ratio.

  However, not only the first power ratio but also the second power ratio has periodicity based on the wavelength period. Therefore, the power ratio difference, which is the difference between them, has less periodic fluctuation based on the wavelength period. Moreover, since the distance to the wall in the directivity when calculating the first power ratio is different from the distance to the wall in the directivity when calculating the second power ratio, the power ratio difference is The value changes to reflect the distance. In addition, by performing an experiment for calculating the first power ratio and the second power ratio by variously changing the distance to the wall, the relationship between the distance to the wall and the power ratio difference can be determined in advance. . The storage unit 65 stores in advance this relationship, that is, the relationship between the distance to the wall and the power ratio difference.

  The reactance value setting unit 614 acquires the relationship between the distance to the wall and the power ratio difference from the storage unit 65, and from the acquired relationship and the power ratio difference calculated by the power ratio difference calculation unit 613 to the wall. Determine the distance.

  FIG. 7 is a diagram illustrating an example of the relationship between the distance to the wall and the power ratio difference. As shown in FIG. 7, the power ratio difference decreases almost monotonously as the distance increases. Here, if the power ratio difference calculated by the power ratio difference calculation unit 613 is about 1.05 as shown in FIG. 7, the distance to the wall is about 70 mm from the relationship shown in FIG. It can be estimated that there is. Therefore, the reactance value setting unit 614 is based on a plurality of reactance value sets stored in the storage unit 65, that is, from the reactance value sets respectively corresponding to three or more installation environments having different distances to the back wall. A reactance value set closest to the estimated distance is selected.

  As described above, according to the second embodiment described above, since the reactance value set is selected according to the distance to the wall in the environment where it is actually installed, good directivity is achieved regardless of the influence of the wall in the back direction. Be able to get.

  Next, a third embodiment will be described. The third embodiment is different from the above-described embodiment in that the transmitter 3 is configured to have a variable transmission frequency, and the functions of the variable reactance control unit 61 and the communication control unit 62 of the direction detection computer 6, and The storage content of the storage unit 65 is also different from the above-described embodiment. Other configurations are the same as those of the above-described embodiment.

  FIG. 8 is a diagram showing a configuration of the direction detection computer 6 in the third embodiment. In the third embodiment, as in the second embodiment, the storage unit 65 stores reactance value sets respectively corresponding to three or more installation environments having different distances to the back wall for each directivity. ing. The storage unit 65 also stores a reactance value set for directing directivity in the back direction, and further stores the relationship between the transmission frequency and the power ratio. The relationship between the transmission frequency and the power ratio will be described in detail later.

  The variable reactance control unit 61 includes a power ratio calculation unit 615 and a reactance value setting unit 616. The reactance value setting unit 616 detects the distance to the back wall, and selects a reactance value set corresponding to the distance to the back wall from the plurality of reactance value sets stored in the storage unit 65. This is the same as the second embodiment. However, the process for detecting the distance to the back wall is different from the second embodiment.

  In the process of detecting the distance to the back wall, a reactance value with directivity on the back is set. Then, the transmitter 3 is instructed to transmit a signal having a predetermined power while changing the transmission frequency from the transmitter 3. Further, the power ratio calculation unit 615 calculates the power ratio.

  Based on an instruction from the reactance value setting unit 616, the communication control unit 62 causes the transmitter 3 to transmit a signal having a predetermined power while changing the transmission frequency. In the third embodiment, the communication control unit 62 corresponds to the transmission control unit in the claims.

  Based on an instruction from the reactance value setting unit 616, the power ratio calculation unit 615 acquires the transmission frequency and transmission power from the transmitter 3 and acquires the reception power from the power detection circuit 5. Then, a power ratio (reception power / transmission power) between transmission power and reception power is calculated for each transmission frequency, and the calculated power ratio is output to reactance value setting unit 616.

  Here, the relationship between the power ratio and the transmission frequency will be described. FIG. 9 is a diagram conceptually showing the relationship between the distance to the back wall and the power ratio for three frequencies (2300, 2400, 2500 MHz).

  As shown in the figure, at any transmission frequency, the power ratio has a periodic variation based on the wavelength period. However, if the distance to the wall and the wavelength are determined, the wavelength portion reflected on the wall is also determined, and consequently, the power ratio is also determined. Therefore, the change tendency of the power ratio when the transmission frequency is changed at a certain distance can be determined in advance based on experiments.

  For example, in the example of FIG. 9, when the distance to the wall is 61 mm, the power ratio at the transmission frequency of 2300 MHz is the smallest, then the power ratio at the 2400 MHz is small, and the power ratio at the 2500 MHz is the largest. I understand.

  FIG. 10 is a diagram showing the change tendency of the power ratio with respect to the change of the transmission frequency at three distances (61 mm, 91.5 mm, and 122 mm). In the example of FIG. 10, when the distance is 61 mm, the power ratio increases as the transmission frequency increases, but the slope of the increase is relatively small. At a distance of 91.5 mm, the power ratio is the largest when the transmission frequency is 2400 MHz. At a distance of 122 mm, the power ratio increases as the transmission frequency increases, and the slope of the increase is relatively large. The storage unit 65 stores the relationship between the transmission frequency and the power ratio as illustrated in FIG.

  The reactance value setting unit 616 acquires the relationship between the transmission frequency and the power ratio from the storage unit 65, and acquires the power ratio at each transmission frequency from the power ratio calculation unit 615. And among the several change tendency contained in the relationship acquired from the memory | storage part 65, the thing nearest to the change tendency with respect to the transmission frequency of the power ratio acquired from the power ratio calculation part 615 is determined, and the determined change tendency shows Estimate the distance to the wall. Furthermore, from the reactance value sets stored in the storage unit 65, that is, from the reactance value sets respectively corresponding to three or more installation environments having different distances to the back wall, the distance estimated as described above is used. Select the closest reactance value set.

  As described above, also in the third embodiment described above, since the reactance value set is selected according to the distance to the wall in the environment where it is actually installed, good directivity is obtained regardless of the influence of the wall in the back direction. Will be able to.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also contained in the technical scope of this invention, and also the summary other than the following is also included. Various modifications can be made without departing from the scope.

  For example, in the above-described embodiment, the power ratio is reception power / transmission power, but the denominator and numerator may be interchanged. In the second embodiment, the directivity is set in the direction deviated from the back direction by 30 ° as the direction deviated from the back direction. However, the directivity may be set in a direction other than 30 °. However, when the distance is too close to the back direction, the power ratio difference is small, and when the deviation angle from the back direction is large, reflection from the wall is small and the second power ratio is small. Therefore, the vicinity of 30 ° is appropriate.

  In the third embodiment, four or more types of transmission frequencies may be used, and the distance for storing the relationship between the transmission frequency and the power ratio may be four or more.

DESCRIPTION OF SYMBOLS 1: Array antenna, 3: Transmitter, 4: Circulator, 5: Power detection circuit, 6: Direction detection computer, 10: Excitation element, 11-16: Non-excitation element, 17: Ground conductor, 18: Variable reactance circuit, 19: Coaxial cable 61: Variable reactance control unit (wall judgment unit, reactance value setting unit, power ratio calculation unit) 62: Communication control unit (transmission control unit) 63: Direction detection unit 65: Storage unit 70 : Wall, 611: first power ratio calculation unit, 612: second power ratio calculation unit, 613: power ratio difference calculation unit, 614: variable reactance setting unit, 615: power ratio calculation unit, 616: reactance value setting unit

Claims (4)

An excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined interval from the excitation element, and a plurality of variable reactance elements respectively connected to the non-excitation elements, An array antenna whose directivity changes as the reactance values of a plurality of variable reactance elements change;
A reactance value set consisting of reactance values corresponding to each variable reactance element can be used for multiple installation environments with different distances to the wall in order to obtain good directivity regardless of the influence of the wall for each directivity. A storage unit for storing a plurality of sets,
One reactance value set from the reactance value set of multiple sets stored in the storage unit, seen including a reactance value setting unit that sets the variable reactance element,
In the storage unit, for each directivity, a reactance value set when the wall exists at a distance that affects directivity and a reactance value set when the wall does not exist at a distance that affects the directivity are stored,
A wall determination unit for determining whether or not the wall exists at a distance that affects directivity;
The reactance value setting unit sets a reactance value set according to a determination result of the wall determination unit . In claim 1 ,
With a reactance value set in which the main lobe faces in the wall detection direction set in advance as a direction for detecting the presence or absence of a wall, transmission power transmitted from the array antenna, and reception power received by the array antenna A power ratio calculation unit for calculating the power ratio of
The wall determining unit determines whether or not a wall exists at a distance that affects directivity based on the power ratio calculated by the power ratio calculating unit. An excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined interval from the excitation element, and a plurality of variable reactance elements respectively connected to the non-excitation elements, An array antenna whose directivity changes as the reactance values of a plurality of variable reactance elements change;
A reactance value set consisting of reactance values corresponding to each variable reactance element can be used for multiple installation environments with different distances to the wall in order to obtain good directivity regardless of the influence of the wall for each directivity. A storage unit for storing a plurality of sets,
A reactance value setting unit that sets one reactance value set from a plurality of reactance value sets stored in the storage unit to the variable reactance element ;
In the storage unit, for each directivity, three or more reactance value sets corresponding to installation environments with different distances to the wall are stored.
With a reactance value set in which the main lobe faces in the wall detection direction set in advance as a direction for detecting the presence or absence of a wall, transmission power transmitted from the array antenna, and reception power received by the array antenna A first power ratio calculation unit that calculates a first power ratio that is a power ratio of
A power ratio between transmission power transmitted from the array antenna and reception power received by the array antenna in a state where a reactance value set in which a main lobe faces in a direction shifted by a predetermined angle with respect to the wall detection direction is set. A second power ratio calculation unit for calculating a second power ratio,
A power ratio difference calculator that calculates a power ratio difference that is a difference between the first power ratio calculated by the first power ratio calculator and the second power ratio calculated by the second power ratio calculator;
The reactance value setting unit sets a reactance value set based on a previously stored relationship in which a reactance value set is determined based on a power ratio difference and a power ratio difference actually calculated by the power ratio difference calculation unit. A variable directional antenna device characterized by that. An excitation element for receiving a radio signal, a plurality of non-excitation elements provided at a predetermined interval from the excitation element, and a plurality of variable reactance elements respectively connected to the non-excitation elements, An array antenna whose directivity changes as the reactance values of a plurality of variable reactance elements change;
A reactance value set consisting of reactance values corresponding to each variable reactance element can be used for multiple installation environments with different distances to the wall in order to obtain good directivity regardless of the influence of the wall for each directivity. A storage unit for storing a plurality of sets,
A reactance value setting unit that sets one reactance value set from a plurality of reactance value sets stored in the storage unit to the variable reactance element ;
In the storage unit, for each directivity, three or more reactance value sets corresponding to installation environments with different distances to the wall are stored.
With the reactance value set in which the main lobe faces in the wall detection direction set in advance as the direction to detect the presence or absence of walls, the transmission frequency is changed to multiple, and signals are transmitted from the array antenna at each transmission frequency. A transmission control unit,
A power ratio calculation unit that calculates a power ratio that is a ratio of transmission power transmitted from the array antenna and reception power received by the array antenna at each transmission frequency;
The reactance value setting unit includes a pre-stored relationship in which a reactance value set is determined based on a change tendency of a power ratio with respect to a change in transmission frequency, and a change tendency of the power ratio actually calculated by the power ratio calculation unit with respect to the transmission frequency. A variable directivity antenna device, wherein a reactance value set is set based on

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