JP2012195663A - Antenna and frequency adjustment method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna whose center frequency can be easily and quickly changed/adjusted.SOLUTION: An antenna 1 comprises: a magnetic body 2 disposed on at least part of a conductor 3 for the antenna; a permanent magnet 6 for applying a DC magnetic field to the magnetic body 2; and a coil 7 for remagnetization disposed around the permanent magnet 6. A power supply unit 8 for supplying a current for remagnetization is connected to the coil 7. A magnetization control unit 9, which controls the power supply unit 8 to remagnetize the permanent magnet 6 so that the DC magnetic field has a predetermined magnetic field strength, is connected to the power supply unit 8.

Description

  The present invention relates to an antenna capable of frequency adjustment and a frequency adjustment method thereof.

  As represented by mobile phones, the current wireless information communication equipment includes various functions such as receiving 1Seg (registered trademark) broadcasts from terrestrial digital TV broadcasts and Bluetooth (registered trademark) wireless functions, as well as communication and call functions. In order to cope with various services, an antenna and an antenna circuit for each communication frequency are used. In order to reduce the size and increase the functionality of equipment, it is important not only to reduce the size of the components themselves, but also to reduce the number of components. In general, since there is a trade-off relationship between the transmission / reception sensitivity of the antenna and the transmittable / receivable band, it is difficult to increase both at the same time. Furthermore, since portable wireless information communication devices operate on batteries, low power consumption is required.

  For example, Patent Document 1 describes an antenna including a transmission line and variable capacitance means. In this antenna, the capacitance of the variable capacitance means is controlled and tuned to a desired center frequency.

  However, the electric circuit that drives the variable capacitance means has a problem that it always consumes power when in use.

JP 2007-104495 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an antenna and a frequency adjustment method thereof that can change and adjust the center frequency easily and quickly while having low power consumption. .

  The antenna according to claim 1, which has been made to achieve the above object, applies a magnetic body disposed on at least a part of the antenna conductor and a DC magnetic field to the magnetic body. A permanent magnet and a coil for re-magnetizing the permanent magnet are provided.

  An antenna according to a second aspect is the one according to the first aspect, wherein a power supply unit that supplies a current for re-magnetization to the coil, and the DC magnetic field is a predetermined magnetic field by controlling the power supply unit. And a magnetization control unit that re-magnetizes the permanent magnet so as to be strong.

  An antenna according to a third aspect is the one according to the second aspect, wherein the magnetization control unit corresponds to the center frequency based on a frequency setting signal input to set the center frequency. The permanent magnet is re-magnetized to the predetermined magnetic field strength.

  The antenna described in claim 4 is the one described in claim 2 or 3, wherein the magnetization control unit re-magnetizes the permanent magnet to the predetermined magnetic field strength every predetermined period. Features.

  An antenna according to a fifth aspect is the one according to any one of the second to fourth aspects, wherein a temperature sensor that detects a temperature of the permanent magnet is connected to the magnetization control unit. The magnetization control unit re-magnetizes the permanent magnet to the predetermined magnetic field intensity corresponding to the temperature detected by the temperature sensor.

  The antenna described in claim 6 is the antenna according to any one of claims 2 to 5, and a magnetic field strength sensor for detecting a magnetic field strength of the DC magnetic field is connected to the magnetization control unit. The magnetization control unit re-magnetizes the permanent magnet when the magnetic field intensity detected by the magnetic field intensity sensor is not within an allowable range of the desired magnetic field intensity.

  The antenna described in claim 7 is the antenna according to any one of claims 1 to 6, wherein the magnetic body sandwiches or covers at least a part of the antenna conductor. .

  An antenna according to an eighth aspect is the one according to any one of the first to seventh aspects, wherein the magnetic body is attached to a surface of at least a part of the conductor for antenna. Features.

  The method for adjusting the frequency of an antenna according to claim 9 includes a magnetic body disposed on at least a part of the antenna conductor, a permanent magnet for applying a DC magnetic field to the magnetic body, and re-magnetizing the permanent magnet. An antenna frequency adjustment method comprising: a coil for supplying a current for re-magnetization to the coil, and re-attaching the permanent magnet so that the DC magnetic field has a predetermined magnetic field strength corresponding to the frequency. It is magnetized.

  According to a tenth aspect of the present invention, there is provided the antenna frequency adjusting method according to the ninth aspect, wherein the permanent magnet is re-magnetized at the predetermined magnetic field strength every predetermined period.

  An antenna frequency adjusting method according to an eleventh aspect is the one according to the ninth or tenth aspect, wherein the permanent magnet is re-magnetized so that the predetermined magnetic field intensity corresponds to a temperature. Features.

  A frequency adjustment method for an antenna according to a twelfth aspect is the method according to any one of the ninth to eleventh aspects, wherein the permanent magnet is reattached when the predetermined magnetic field strength is not within an allowable range. It is magnetized.

  According to the antenna and the frequency adjusting method of the present invention, a magnetic material is disposed on at least a part of the antenna conductor, and a remagnetization coil is disposed on a permanent magnet that applies a DC magnetic field to the magnetic material. Therefore, the antenna's inductance component can be adjusted by supplying a re-magnetizing current to this coil and setting the magnetic field strength of the permanent magnet to a predetermined magnetic field strength corresponding to the center frequency. can do. Since the permanent magnet can be re-magnetized in a short time electrically, the frequency can be easily and quickly adjusted even in a state where the permanent magnet is disposed in the wireless communication device. Furthermore, since the permanent magnet can be re-magnetized in a short time, the power consumption is small and energy is saved.

  When a power supply unit that supplies a re-magnetization current to the coil and a magnetization control unit that controls the power supply unit are provided, the frequency can be adjusted by supplying the re-magnetization current to the coil. Note that the power supply unit and the magnetization control unit may be arranged integrally with the antenna, or may be arranged in the electric circuit of the wireless communication device.

  The magnetizing control unit re-magnetizes the permanent magnet at a predetermined magnetic field strength at a predetermined cycle, so that the DC magnetic field of the permanent magnet is refreshed at predetermined time intervals. Since it does not become weak and has a constant strength, the center frequency is prevented from shifting with time, and stable performance can be maintained.

  When the magnetization control unit re-magnetizes the permanent magnet based on the frequency setting signal, the center frequency can be controlled. For example, transmission can be performed in a plurality of frequency bands like a mobile phone that can use various wireless systems. Even a wireless device that performs reception can handle a single antenna without using a plurality of antennas.

  When the magnetization control unit re-magnetizes the permanent magnet based on the temperature, it is possible to adjust the frequency shift due to temperature fluctuation.

  When the magnetization control unit re-magnetizes the permanent magnet when the magnetic field strength of the permanent magnet is not within the allowable range, it is possible to adjust a frequency shift due to a change with time.

  When the magnetic body sandwiches or covers the antenna conductor, the variable range of the inductance component of the antenna can be increased, so that the frequency adjustment range can be increased.

  When the magnetic body is attached to at least a part of the surface of the antenna conductor in the form of a film, the antenna is not increased in size and can be reduced as much as possible.

It is a schematic block diagram which shows typically the antenna to which this invention is applied. It is an equivalent circuit diagram of an antenna to which the present invention is applied. It is a magnetization curve explaining the principle of the antenna to which this invention is applied. It is a flowchart for demonstrating the center frequency setting method in the antenna to which this invention is applied. It is a flowchart for demonstrating the setting method of the center frequency corresponding to the temperature change in the antenna to which this invention is applied. It is a flowchart for demonstrating the setting method of the center frequency corresponding to the magnetic field intensity fall in the antenna to which this invention is applied. It is a schematic block diagram which shows typically the modification of the antenna shown in FIG. It is a schematic block diagram which shows typically the other antenna to which this invention is applied. It is an equivalent circuit diagram of another antenna to which the present invention is applied.

  Embodiments of the present invention will be described in detail below, but the scope of the present invention is not limited to these embodiments.

  FIG. 1 shows an example of an antenna to which the present invention is applied. The antenna 1 includes a magnetic body 2, an antenna conductor 3, permanent magnets 6 and 6, coils 7 and 7, a power supply unit 8, a magnetization control unit 9, a magnetic field strength sensor 21, and a temperature sensor 22. In the same figure, the magnetic body 2, the conductor 3, the permanent magnets 6 and 6, and the coils 7 and 7 are shown in an exploded perspective view.

  The magnetic body 2 is a soft magnetic body containing at least one of Fe, Co, Ni, and Gd, and is, for example, a yttrium-iron-garnet (YIG: Yttrium-Iron-Garnet) ferrite single crystal. As an example, the magnetic body 2 is formed in a rectangular thin plate. The magnetic body 2 may be formed in a film shape on a substrate made of ceramic, for example.

  As an example, a loop-shaped antenna conductor 3 is arranged on one plane of the magnetic body 2 (upper side surface in the figure). The antenna conductor 3 may be formed in a film shape with a conductor pattern directly on the magnetic body 2 or on a substrate (not shown) made of ceramic or the like, or may be formed of a metal plate. For example, one end 4a of the antenna conductor 3 is connected to the output of a transmission circuit (not shown), and the other end 4b is connected to the reference potential of the transmission circuit. A capacitor for frequency tuning may be connected between the one end 4a and the other end 4b. In addition, a ground electrode plate (not shown) may be disposed on the magnetic body 2 or another plane (the lower side of the drawing) of the permanent magnet 6 described later. Furthermore, as shown in FIG. 7, the direction (angle) of the antenna conductor 3 may be rotated by 90 degrees. The angle of the antenna conductor 3 is preferably 0 degrees in FIG. 1 or 90 degrees in FIG. 7, but may be arranged at any angle such as 30 degrees or 45 degrees. As described above, the direction of the antenna conductor 3 can be set in any direction corresponding to a desired radiation characteristic (directivity) or the like. Further, permanent magnets 6 are provided on the upper surface side (upper side surface in the figure) and the lower surface side (lower side surface in the figure) of the plate-like magnetic body 2 so as to sandwich the main surface of the magnetic body 2 to which the antenna conductor 3 is attached. , 6 may be arranged.

  The magnetic body 2 may be isotropic and may have uniaxial magnetic anisotropy and multiaxial magnetic anisotropy. Most preferably, it has uniaxial magnetic anisotropy. In this case, the direction of the magnetic field of permanent magnets 6 and 6, which will be described later, is the easy axis of magnetization, and the direction of the plane perpendicular to the direction of magnetic field of permanent magnets 6 and 6 is difficult to magnetize. It is preferably an axis.

  The permanent magnet 6 is a hard magnetic material containing at least one of Fe, Co, Ni, and Gd, and is, for example, a general ferrite magnet. The permanent magnet 6 applies a DC magnetic field to the magnetic body 2. The pair of permanent magnets 6 and 6 are arranged close to or in close contact with the magnetic body 2 at a predetermined interval so as to sandwich the opposing side end surfaces of the plate-like magnetic body 2. As an example, the permanent magnet 6 is formed in a rectangular thin plate having a side end surface having substantially the same shape as the side end surface of the magnetic body 2, and is magnetized in a direction orthogonal to the side end surface. The permanent magnets 6 and 6 are arranged on the magnetic body 2 in a direction in which a magnetic field in the same direction is applied to the magnetic body 2, that is, in a direction in which the permanent magnets 6 and 6 attract each other by magnetic force. The permanent magnet 6 may be formed in a film shape on a substrate made of ceramic, for example, or may be formed in a film shape on the side end surfaces of the magnetic body 2 facing each other.

  The coil 7 is for re-magnetizing the permanent magnet 6, and is disposed on the permanent magnet 6 so that the axis of the coil 7 coincides with the magnetic field direction of the permanent magnet 6. In this case, the coil 7 is wound directly around the permanent magnet 6. The coils 7 and 7 are wound around the permanent magnets 6 and 6 in a direction in which a magnetic field in the same direction is applied to the corresponding permanent magnets 6 and 6, that is, the winding directions are the same. Are electrically connected in series. When the permanent magnet 6 is formed in a film shape on the substrate, the coil 7 may be formed in a pattern so as to wind the permanent magnet 6 on the substrate. The coil 7 is preferably arranged directly on the permanent magnet 6 or at a position in the vicinity of the permanent magnet 6 from the viewpoint of applying a magnetic field, but any position where the magnetic field for re-magnetization can be applied to the permanent magnet 6. Further, it may be arranged at a position away from the permanent magnet 6. As long as the coil 7 can be magnetized to the permanent magnet 6, it does not ask | require a shape and arrangement | positioning.

  The power supply unit 8 supplies a re-magnetization current to the coils 7 and 7, a DC current source 11 that supplies a DC current in the forward direction to the coils 7 and 7, and a DC in the reverse direction to the coils 7 and 7. A direct current source 12 for supplying current and a changeover switch 13 for switching between the direct current sources 11 and 12 connected to the coils 7 and 7 are provided. The power supply unit 8 may be disposed integrally with the coils 7, 7, etc. near the coils 7, 7, or disposed in the electric circuit of the wireless communication device and connected to the coils 7, 7 with an electric cable. May be.

  The DC current sources 11 and 12 are variable DC constant current sources each capable of adjusting the output DC current value by electrical control, and are controlled by the magnetization control unit 9. The DC current sources 11 and 12 may use a known DC power supply or current control circuit, or a capacitor-type capacitor in which a capacitor is charged with a charge corresponding to a current value and the charge is instantaneously discharged. A discharge circuit may be used.

  The changeover switch 13 is a relay or a semiconductor switch that can electrically control the changeover operation, and is controlled by the magnetization control unit 9. The changeover switch 13 is a bidirectional changeover switch with an intermediate point, and has a center electrode 13a and changeover electrodes 13b and 13c. The changeover switch 13 can be controlled to switch the center electrode 13a to either the changeover electrode 13b, the changeover electrode 13c, or the open state. One end of coils 7, 7 connected in series is connected to the center electrode 13 a of the changeover switch 13. The positive electrode of the direct current source 11 is connected to the switching electrode 13 b of the changeover switch 13. Further, the negative electrode of the direct current source 12 is connected to the switching electrode 13 c of the changeover switch 13. The negative electrode of the direct current source 11 and the positive electrode of the direct current source 12 are connected to the other ends of the coils 7 and 7 connected in series.

  The magnetization control unit 9 controls the power supply unit 8 to re-magnetize the permanent magnet 6 so that the DC magnetic field applied to the magnetic body 2 by the permanent magnet 6 has a predetermined magnetic field strength. As an example, the magnetization control unit 9 includes a CPU, a flash ROM, a RAM, an A / D converter, an input / output interface circuit (all not shown), and the like, and operates according to a program stored in the ROM. The magnetization control unit 9 may be configured by combining logic circuits. In addition to the DC current sources 11 and 12 and the changeover switch 13 described above, a magnetic field intensity sensor 21 and a temperature sensor 22 are connected to the magnetization control unit 9. Furthermore, a frequency setting signal is input to the magnetization control unit 9 from, for example, a control circuit (not shown) of a wireless communication device (for example, a mobile phone) on which the antenna 1 is mounted. The magnetization control unit 9 may be disposed integrally with the antenna conductor 3 or the like, or may be disposed in the electric circuit of the wireless communication device. The magnetization control unit 9 may also be used as a control circuit for the wireless communication device. In the case of sharing, an internally generated frequency setting signal is used.

  The magnetic field strength sensor 21 is, for example, a Hall element, a magnetoresistive effect element, a magnetic impedance element, a Faraday element, an orthogonal fluxgate magnetic sensor, or the like. The magnetic field strength sensor 21 is disposed at a position close to the permanent magnet 6, detects the magnetic field strength of the DC magnetic field applied to the magnetic body 2 by the permanent magnet 6, and outputs the detected magnetic field strength to the magnetization control unit 9. The temperature sensor 22 is, for example, a thermocouple or a platinum resistance thermometer, and is disposed directly or in proximity to the permanent magnet 6 to detect the temperature of the permanent magnet 6 and output the detected temperature to the magnetization control unit 9. .

  Next, the operation principle of the antenna 1 will be described.

  FIG. 2 shows an equivalent circuit of the antenna 1. The antenna 1 is represented by an LC parallel resonance circuit of an inductance L and a capacitance C. This LC parallel resonance frequency becomes the center frequency of the antenna. The inductance L is an inductance component of the antenna conductor 3. The capacitance C is a total capacitance of the capacitance component of the antenna conductor 3 or the capacitance component and a capacitor connected to the antenna conductor 3 for tuning.

  Here, the inductance L is affected by the magnetic permeability μ of the magnetic body 2 disposed on the conductor 3. Specifically, when the magnetic permeability μ of the magnetic body 2 changes, the inductance L changes in proportion to the magnitude of the magnetic permeability μ. The magnetic permeability μ of the magnetic body 2 changes in inverse proportion to the magnitude of the DC magnetic field H when the DC magnetic field H applied to the magnetic body 2 changes. Therefore, the inductance L changes in inverse proportion to the magnitude of the DC magnetic field H applied to the magnetic body 2. That is, when the magnitude of the DC magnetic field H is changed, the inductance L changes, and the LC parallel resonance frequency, that is, the center frequency of the antenna 1 changes.

  The magnitude of the DC magnetic field H applied to the magnetic body 2 is proportional to the magnitude of the residual magnetic flux density of the permanent magnets 6 and 6. That is, the DC magnetic field H is large in the case of the so-called strong permanent magnet 6, and the DC magnetic field H is small in the case of the weak permanent magnet 6.

FIG. 3 shows a magnetization curve (BH curve) of the permanent magnet 6. This magnetization curve is a general one. For example, when the permanent magnet 6 is subjected to a large positive magnetic field H ₀ , the permanent magnet 6 is magnetically saturated and becomes the point a of the magnetization curve. When the magnetic field H is weakened to 0 from this state, the magnetization curve passes through the point b, and when the magnetic field H is further strengthened in the reverse direction, the magnetization curve passes through the point c and in the reverse direction when the magnetic field is Hr. Magnetic saturation reaches point d. From this state, when the magnetic field H is increased in the forward direction, the magnetization curve changes from point e (reverse magnetic flux density Br in the reverse direction) to point f to point a. Thus, the magnetization curve draws a hysteresis curve. When the permanent magnet 6 is manufactured, the magnet base material before magnetization having a residual magnetic flux density B of 0 is magnetized by applying a magnetic field of H ₀ or more.

When the inventor applies a magnetic field Hr in the opposite direction to the permanent magnet 6 and subsequently applies the magnetic field H ₁ and then returns the magnetic field to 0, the magnetization curve becomes d point → e point → s ₁ point as shown in FIG. → s is ₂ points, I realized that the permanent magnet 6 is magnetized again in the residual magnetic flux density B _1. Further, when do the same in the magnetic field H _2, magnetization curve becomes point d → e point → t ₁ point → t ₂ points, the permanent magnet 6 is magnetized again in the residual magnetic flux density B _2. That is, by applying a magnetic field Hr in the opposite direction to the permanent magnet 6 and resetting it once, and then applying a magnetic field with a predetermined strength such as the magnetic fields H ₀ , H ₁ , H ₂ , the residual magnetic flux density of the permanent magnet 6 is reduced to B It has been found that it is possible to freely set a desired size such as ₀ , B ₁ and B ₂ . By using this principle, the intensity of the DC magnetic field H of the permanent magnet 6 is appropriately changed and adjusted, the value of the magnetic permeability μ of the magnetic body 2 is adjusted, and the inductance L is set to a desired value from this. Thus, the center frequency of the antenna 1 can be changed and set. In addition, since re-magnetization of the permanent magnet 6 can be performed by electrical control in a short time, the center frequency can be changed and set quickly and easily in a short time.

  As shown in FIG. 1, when the magnetic body 2 is sandwiched between a pair of permanent magnets 6, 6, a direct magnetic field is applied to the magnetic body 2 more uniformly than when only one permanent magnet 6 is disposed. Can be changed stably and accurately. Furthermore, when the magnetic body 2 is sandwiched between a pair of permanent magnets 6 and 6, the variable range of the strength of the DC magnetic field H applied to the magnetic body 2 can be made larger than when only one permanent magnet 6 is disposed. it can. Therefore, since the variable width of the magnetic permeability μ of the magnetic body 2 can be increased, the variable width of the inductance is increased, and the variable width of the center frequency of the antenna 1 can be increased. Note that only one permanent magnet 6 may be arranged on the magnetic body 2 as required.

  In order to set the magnitude of the residual magnetic flux density of the permanent magnet 6, it is necessary to control the magnitude of the magnetic field H, so the slope from the point f to the point a of the magnetization curve is gentle (the slope is small). It is preferable. This is because if the magnetization curve has a steep slope (the slope is large), the residual magnetic flux density B changes greatly only by slightly changing the magnetic field H, so the magnetic field H must be precisely controlled. is there. A strong neodymium permanent magnet or a samarium cobalt permanent magnet has a steep magnetization curve, so that the magnetic field H must be precisely controlled. Strontium-ferrite permanent magnets and barium-ferrite permanent magnets are preferable because the gradient of the magnetization curve is gentle and the magnetic field H can be easily controlled.

  Next, a method for using the antenna 1 will be described.

  First, preparation before using the antenna 1 will be described.

  Prior to use, a current value (hereinafter referred to as a set current value) to be output to the DC current source 11 in order to set the residual magnetic flux density of the permanent magnets 6 and 6 corresponding to each center frequency to be set in advance. The current value (hereinafter referred to as a reset current value) to be output to the DC current source 12 to reset the permanent magnets 6 and 6 and the allowable range of the magnetic field strength when the center frequency is normally set are magnetized. It is stored in the control unit 9. Further, when there is a temperature variation in the center frequency of the antenna 1 or according to necessity, the temperature threshold value for resetting the center frequency, and the optimum current value and magnetic field strength of the DC current sources 11 and 12 at each temperature are set. The allowable range is stored in the magnetization control unit 9 in association with each center frequency and each temperature threshold value. Note that only one current value for resetting the permanent magnet 6 may be stored as long as it is common for each condition.

  These preset current values and the like are determined by selecting optimum values by experimentally repeating the acquisition of the characteristics of the antenna 1 with the residual magnetic flux density of the permanent magnets 6 and 6 changed as a parameter. For example, the current value flowing through the DC current sources 11 and 12 is changed as a parameter, the ambient temperature is changed as a parameter if necessary, and the impedance characteristic of the antenna 1 is acquired by a network analyzer. To determine the optimal current value. The current values obtained in this way may be applied in common to a plurality of manufactured antennas 1, or characteristics are obtained for each individual antenna 1 and the optimum value is applied to each antenna 1. May be. When obtaining an optimum current value or the like for each individual antenna 1, individual manufacturing variations can be eliminated. This completes the preparation before use.

  Next, a method for setting the center frequency of the antenna 1 will be described with reference to FIGS.

  An antenna 1 shown in FIG. 1 is used by being connected to a transmission / reception circuit of a wireless communication device (not shown). When the wireless communication device performs transmission / reception by switching a plurality of frequency bands, a control circuit (not shown) that comprehensively controls the wireless communication device outputs a frequency setting signal for indicating the center frequency to the antenna 1. .

  As shown in the flowchart of FIG. 4, when the frequency setting signal is input (Step S11), the magnetization control unit 9 controls the DC current source 12 to set the center frequency (setting) indicated by the frequency setting signal. In addition to outputting a current at a reset current value corresponding to (frequency), the changeover switch 13 is controlled in conjunction with this, and the center electrode 13a and the changeover electrode 13c are brought into contact with each other for a predetermined time (for example, 10 μsec) (step S12). ). As a result, the coil 7 generates a magnetic field Hr (see FIG. 3) in a direction opposite to the magnetic field direction of the permanent magnet 6, and this magnetic field Hr is applied to the permanent magnet 6 for a predetermined time, and the permanent magnet 6 is magnetically saturated in the reverse direction. The residual magnetic flux density Br is reset and the residual magnetic flux density is reset.

Subsequently, the magnetization controller 9 controls the direct current source 11 to output a current with a set current value corresponding to the center frequency, and controls the changeover switch 13 in conjunction with this to control the center electrode 13a. And the switching electrode 13b are brought into contact with each other for a predetermined time (for example, 10 μsec) (step S13). As a result, for example, a magnetic field H ₁ (see FIG. 3) in the same direction as the magnetic field direction in which the coil 7 re-magnetizes the permanent magnet 6 is generated, and this magnetic field H ₁ is applied to the permanent magnet 6 for a predetermined time. For example, remagnetization is performed to a residual magnetic flux density B ₁ (see FIG. 3) corresponding to the set frequency.

  The predetermined time during which the current is supplied to the coil 7 in steps S12 and S13 is a time necessary for magnetizing the permanent magnet 6, but it may be usually a short time. Therefore, there is almost no power consumption and energy saving.

  Subsequently, the magnetization control unit 9 reads the magnetic field strength detected by the magnetic field strength sensor 21 (step S14), and determines whether or not the magnetic field strength is within the allowable range stored in advance in the magnetization control unit 9. (Step S15). If it is within the allowable range, the frequency setting operation is terminated. If it is not within the allowable range, the process returns to step S12, and the permanent magnet 6 is magnetized again. If it is not within the allowable range, step S13 may be performed by increasing or decreasing the set current value so as to fall within the allowable range.

  The center frequency setting operation is thus completed, and the center frequency of the antenna 1 is set. When a frequency setting signal for changing to a different center frequency is input from the wireless communication device, the center frequency is set again to set the antenna 1 to a different center frequency. If necessary, the magnetization control unit 9 reads the ambient temperature detected by the temperature sensor 22 before performing step S12, and steps with the reset current value and the set current value corresponding to the temperature and the center frequency. S12 and S13 may be performed. Further, when it is not necessary to detect the magnetic field strength, as indicated by a broken line in FIG.

  The magnetization control unit 9 preferably performs this center frequency setting operation at predetermined intervals. This predetermined period is set to a time interval shorter than the time interval at which the residual magnetic flux density of the permanent magnet 6 becomes weaker than the allowable value with time.

  Next, a method for setting a center frequency corresponding to a temperature change will be described with reference to FIGS.

  The antenna 1 is often arranged in a wireless communication device, and the antenna 1 may become high temperature due to heat generated by the transmission amplifier, and the center frequency may deviate from the set frequency. Hereinafter, an operation for restoring such a shift in the center frequency will be described.

  As shown in the flowchart of FIG. 5, the magnetization controller 9 reads the temperature detected by the temperature sensor 22 (see FIG. 1) constantly or intermittently (step S <b> 21), and whether the temperature threshold value stored in advance is exceeded. It is determined whether or not (step S22). This temperature threshold is set to a temperature at which the deviation of the center frequency is not allowed. A plurality of temperature thresholds may be set in stages. Further, the temperature threshold value may be different depending on whether the temperature increases or decreases. The set current value, the reset current value, and the allowable range of the magnetic field strength corresponding to each of the higher temperature side and the lower temperature side than the temperature threshold are stored in the magnetization control unit 9 in advance.

  When it is determined in step S22 that the temperature threshold value has been exceeded, the magnetization control unit 9 controls the DC current source 12 to generate a current with a reset current value corresponding to the detected temperature (and the set frequency at that time). At the same time, the changeover switch 13 is controlled to bring the center electrode 13a and the changeover electrode 13c into contact with each other for a predetermined time (step S23). Thereby, the permanent magnet 6 is reset like step S12 already demonstrated.

  Subsequently, the magnetization control unit 9 controls the DC current source 11 to set a preset current value corresponding to the detected temperature stored in advance, that is, a set current value that can correctly set the center frequency to the set frequency at the detected temperature. In step S24, the current is output and the changeover switch 13 is controlled to bring the center electrode 13a and the changeover electrode 13b into contact with each other for a predetermined time (step S24). Thereby, the permanent magnet 6 is re-magnetized to the residual magnetic flux density B corresponding to the temperature.

  Subsequently, the magnetization control unit 9 performs steps S25 and S26 in the same manner as steps S14 and S15 already described, confirms the magnetic field strength detected by the magnetic field strength sensor 21, and the magnetic field strength is allowable at that temperature. Check if it is within the range, reset if necessary, and return to step S21.

  Thus, the setting operation of the center frequency corresponding to the temperature change is completed, and the center frequency of the antenna 1 shifted by the temperature returns to the setting frequency. The center frequency is reset when the temperature rises above the detection threshold and when it falls below the detection threshold. If it is not necessary to check the magnetic field strength, step S24 may be performed after returning to step S21 as indicated by a broken line in FIG.

  Next, a method for resetting the center frequency corresponding to the decrease in magnetic field strength will be described with reference to FIGS.

  The magnetic field strength of the permanent magnet 6 varies depending on the type of material, but decreases as time passes after magnetization. Hereinafter, an operation for returning the shift of the center frequency due to such a decrease in the magnetic field strength will be described.

  As shown in the flowchart of FIG. 6, the magnetization control unit 9 reads the magnetic field strength detected by the magnetic field strength sensor 21 (see FIG. 1) constantly or intermittently (step S <b> 31) and sets it to the set frequency (and temperature). It is determined whether or not the corresponding magnetic field strength is within an allowable range (step S32). If it is within the allowable range, the process returns to step S31.

  If it is determined in step S32 that the current value is not within the allowable range, the magnetization control unit 9 controls the direct current source 12 to output a current with a reset current value corresponding to the set frequency (and temperature), and the changeover switch. 13 is controlled to bring the center electrode 13a and the switching electrode 13c into contact with each other for a predetermined time (step S33). Thereby, the permanent magnet 6 is reset like step S12 already demonstrated.

  Subsequently, the magnetization control unit 9 controls the direct current source 11 to output a current at a set current value corresponding to the set frequency (and temperature), and controls the changeover switch 13 to control the center electrode 13a and the changeover electrode. 13b is contacted for a predetermined time (step S34). Thereby, the permanent magnet 6 is magnetized to the residual magnetic flux density B corresponding to the set frequency, and the process returns to step S31.

  The center frequency resetting operation corresponding to the decrease in magnetic field intensity is thus completed, and the center frequency of the antenna 1 returns to the set frequency.

  The center frequency setting method shown in FIG. 4, the center frequency setting method corresponding to the temperature change shown in FIG. 5, and the center frequency setting method corresponding to the magnetic field strength reduction shown in FIG. 6 may all be performed. Any one may be selected. When the temperature is not detected, the temperature sensor 22 is unnecessary, and when the magnetic field strength is not detected, the magnetic field strength sensor 21 is unnecessary.

  Next, antennas 1a, 1b, and 1c, which are other examples of the antenna to which the present invention is applied, will be described with reference to FIG. In addition, the same code | symbol is attached | subjected about the same structure as already demonstrated, and detailed description is abbreviate | omitted.

  An antenna 1a shown in a partial cross-sectional view in FIG. 8 (a) is arranged with a conductor 3 sandwiched between a pair of film-like magnetic bodies 2 and 2 on one plane (upper side in the figure) of a permanent magnet 6. is there. A coil 7 is wound around the side surface of the permanent magnet 6. A power supply unit 8 (see FIG. 1) is connected to the coil 7, and a magnetization control unit 9 (see FIG. 1) is connected to the power supply unit 8. The magnetic body 2 may be formed wider than the conductor 3 to cover the conductor 3, or the conductor 3 may be arranged inside one magnetic body 2. Further, both sides of the magnetic bodies 2 and 2 sandwiching the conductor 3 may be sandwiched between a pair of permanent magnets 6 and 6. In this case, the coils 7 and 7 are arranged so as to be paired with the pair of permanent magnets 6 and 6.

  Thus, when the magnetic bodies 2 and 2 are on both sides of the conductor 3, the maximum value of the inductance is larger than when the magnetic body 2 is on only one side, so that the inductance by adjusting the magnetic field strength of the permanent magnet 6 is increased. The variable width of L is increased, and the variable width of the center frequency of the antenna 1 can be increased. Further, when sandwiched between the pair of permanent magnets 6 and 6, the variable width of the magnetic permeability μ of the magnetic bodies 2 and 2 can be increased, so that the variable width of the inductance is increased and the variable width of the center frequency of the antenna 1 is increased. Can be increased.

  An antenna 1 b shown in an exploded perspective view in FIG. 8B includes a magnetic body 2, an antenna conductor 3, permanent magnets 6 and 6, and coils 7 and 7. The magnetic body 2 is formed in a columnar shape, and the antenna conductor 3 is wound around the column in a coil shape. The magnetic body 2 and the antenna conductor 3 are bar antennas. As shown in the figure, columnar permanent magnets 6 and 6 having substantially the same diameter as the magnetic body 2 are arranged at both ends of the magnetic body 2 so as to be close to or in close contact with the magnetic body 2. The permanent magnets 6 and 6 are magnetized in the axial direction, and the directions of the magnetic fields are the same. Coils 7 and 7 are wound around the permanent magnets 6 and 6 in the same winding direction. A power supply unit 8 (see FIG. 1) is connected to the coils 7 and 7, and a magnetization control unit 9 (see FIG. 1) is connected to the power supply unit 8. Separate power supply units 8 and 8 and magnetization control units 9 and 9 may be connected to the coils 7 and 7 in association with each other.

  Thus, even in the case of the antenna 1b having the bar antenna structure, the inductance of the antenna conductor 3 can be adjusted by re-magnetizing the permanent magnets 6 and 6 and adjusting the magnetic field strength, and the center frequency of the antenna 1b can be adjusted. Can be adjusted.

  An antenna 1c shown in a partially enlarged perspective view in FIG. 8C is one in which a part of the antenna conductive wire 3 is covered with a film-like magnetic body 2. As an example, the antenna conductor 3 is made of metal and has a round bar shape. A plate-like permanent magnet 6 is disposed on or close to the magnetic body 2, and a coil 7 is wound around the permanent magnet 6. A power supply unit 8 (see FIG. 1) is connected to the coil 7, and magnetization control units 9 and 9 (see FIG. 1) are connected to the power supply unit 8.

  An equivalent circuit of the antenna 1c is shown in FIG. In the antenna 1c, a portion to which the magnetic body 2 is attached has an inductance L, and a portion to which the magnetic body 2 is not attached has an inductance Lo. In the antenna 1c, an inductance L and an inductance Lo are connected in series, and this inductance (L + Lo) and a capacitance C are connected in parallel to form an LC parallel resonance circuit. The inductance L changes as the magnetic field strength of the permanent magnet 6 changes. Therefore, by re-magnetizing the permanent magnet 6 and adjusting the magnetic field strength, the inductance L of the antenna 1c can be adjusted, and the center frequency of the antenna 1c can be adjusted. The position and range of the antenna conductor 3 on which the magnetic body 2 is arranged are appropriately set according to the frequency width to be varied. Similarly, also in the antennas 1, 1 a, 1 b, the center frequency can be adjusted by arranging the magnetic body 2 on at least a part of the antenna conductor 3 and adjusting the magnetic field strength of the permanent magnet 6.

  The antenna shape (antenna configuration and type) of the antenna conductor 3 is not limited to a loop type or a bar antenna type as long as it has a shape that functions as an antenna. For example, inverted F type, planar type, linear type, whip type, coil type, dipole type, monopole type, comb type antenna, traveling wave antenna such as Yagi / Uda antenna, helical antenna, phase difference feeding antenna, etc. The present invention can be applied to various known antenna shapes. Any antenna that has a magnetic material disposed on at least a part of an antenna conductor and a permanent magnet that applies a DC magnetic field to the magnetic material and at least a re-magnetizing coil is disposed within the scope of the present invention. included.

  Moreover, although the power supply part 8 has the direct current sources 11 and 12 and the current (setting current, reset current) for remagnetizing the permanent magnet 6 has been described as an example of the direct current, the setting current and the reset current are described. May be an instantaneous pulse current or an alternating current such as a sine wave, trapezoidal wave or sawtooth wave. In the case of alternating current, the positive peak value corresponds to the set current value, the negative peak value corresponds to the reset current value, and the power supply unit 8 has one cycle (from negative (reset current) to positive (set current) ( (Alternate cycle) AC current is output.

  1, 1a, 1b, and 1c are antennas, 2 is a magnetic material, 3 is a conductor for an antenna, 4a is one end, 4b is the other end, 6 is a permanent magnet, 7 is a coil, 8 is a power supply, and 9 is magnetized. Control unit, 11 and 12 are direct current sources, 13 is a changeover switch, 13a is a center electrode, 13b and 13c are changeover electrodes, 21 is a magnetic field strength sensor, 22 is a temperature sensor, C is a capacitance, L and Lo are inductances It is.

Claims (12)

  An antenna comprising: a magnetic body disposed on at least a part of an antenna conductor; a permanent magnet that applies a DC magnetic field to the magnetic body; and a coil that re-magnetizes the permanent magnet.   A power supply unit that supplies a re-magnetization current to the coil; and a magnetization control unit that controls the power supply unit to re-magnetize the permanent magnet so that the DC magnetic field has a predetermined magnetic field strength. The antenna according to claim 1.   The magnetizing control unit re-magnetizes the permanent magnet to the predetermined magnetic field strength corresponding to the center frequency based on a frequency setting signal input to set the center frequency. Item 3. The antenna according to Item 2.   The antenna according to claim 2 or 3, wherein the magnetization control unit re-magnetizes the permanent magnet to the predetermined magnetic field strength every predetermined period.   A temperature sensor for detecting the temperature of the permanent magnet is connected to the magnetization control unit, and the magnetization control unit has the permanent magnet at the predetermined magnetic field intensity corresponding to the temperature detected by the temperature sensor. The antenna according to claim 2, wherein the antenna is re-magnetized.   The magnetization control unit is connected to a magnetic field strength sensor that detects the magnetic field strength of the DC magnetic field, and the magnetization control unit detects that the magnetic field strength detected by the magnetic field strength sensor is equal to the desired magnetic field strength. 6. The antenna according to claim 2, wherein the permanent magnet is re-magnetized when it is not within an allowable range.   The antenna according to claim 1, wherein the magnetic body sandwiches or covers at least a part of the antenna conductor.   The antenna according to any one of claims 1 to 7, wherein the magnetic body is attached in a film shape on at least a part of the surface of the antenna conductor.   An antenna frequency adjustment method comprising: a magnetic body disposed on at least a part of an antenna conductor; a permanent magnet that applies a DC magnetic field to the magnetic body; and a coil that re-magnetizes the permanent magnet. A method for adjusting the frequency of an antenna, comprising supplying a current for re-magnetization to the coil and re-magnetizing the permanent magnet so that the DC magnetic field has a predetermined magnetic field strength corresponding to the frequency.   10. The antenna frequency adjusting method according to claim 9, wherein the permanent magnet is re-magnetized at the predetermined magnetic field strength at predetermined intervals.   11. The antenna frequency adjustment method according to claim 9, wherein the permanent magnet is re-magnetized so that the predetermined magnetic field intensity corresponds to temperature.   12. The antenna frequency adjusting method according to claim 9, wherein the permanent magnet is re-magnetized when the predetermined magnetic field strength is not within an allowable range.

Images