Radio wave visualizing method and apparatus

[0002] 1. Field of the Invention

[0003] The present invention relates to an electromagnetic wave measuring apparatus and a method for evaluating and measuring radiation directivity of an electromagnetic wave using the same.

[0004] 2. Description of the Related Art

[0005] Generally, an electromagnetic wave radiated from an antenna or an electromagnetic wave radiated from a device itself are evaluated for its energy and directivity in a method in which a device to be evaluated is placed using a large anechoic chamber and an electromagnetic wave thereof is received and observed at a sufficiently distant position. The reason for using the RF anechoic chamber is to prevent an electromagnetic wave from entering from the outside and to eliminate an effect of a reflected wave upon the measurement. The reason for performing the measurement at a sufficiently distant position is to measure the radiated electromagnetic wave in the far field and to reduce an error caused by a changed sensitivity due to an effect of the device to be evaluated upon a receiving antenna.

[0006] This method, however, involves very large evaluating equipment (for example, 10 m×10 m×10 m in size). Thus, a near field measuring method (Tasuku Teshirogi: “Measurement in Neighborhood Field for Antenna”, Shingakusi, vol.62, no.10, pp.1145-1153, October 1979) has been developed as a method for evaluating an antenna. The near field measuring method includes: (a) plane scanning; (b) cylindrical plane scanning; and (c) spherical scanning. The methods (b) and (c) imply the extreme difficulty of accurately measuring the perimeter of a device to be evaluated and involve a large amount of operation required for correction of a probe antenna and for conversion from a near field to a far field, so that these methods have not been brought into practice widely. Thus, the method (a) has been used generally.

[0007] However, the above-mentioned conventional, (a) plane scanning method, has a disadvantage that it can be adapted only to an antenna with a relatively narrow directivity such as an aperture antenna. The cause thereof is that the method performs conversion from the near field to the far field on the assumption that a source of an electromagnetic wave is planar.

[0008] It is an object of the present invention to provide an electromagnetic wave measuring apparatus capable of accurately estimating radiation directivity from an antenna having a relatively wide directivity or from an antenna integral-type communication device and a method for evaluating and measuring the radiation directivity of an electromagnetic wave.

[0009] The electromagnetic wave measuring apparatus of the present invention comprises a probe scanner movable in the x direction, the y direction, the z direction and a rotating direction; a fixed probe antenna, a relative position of which does not change against a measured object; a control/record and operation/display unit; an interference measuring unit; and a level detector. The probe scanner has a sensor for measuring a three-dimensional shape and a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave attached thereto.

[0010] A method for evaluating and measuring radiation directivity of an electromagnetic wave with an electromagnetic wave measuring apparatus of the present invention has the steps of: measuring and recording an object shape distribution of an antenna integral-type communication device to be observed with a sensor for measuring a three-dimensional shape, and measuring and recording a scanning distribution of interference complex data between a detected signal with a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave and a detected signal with a fixed probe antenna, a relative position of which does not change against a measured object, as a two-dimensional electric field distribution or a two-dimensional magnetic field distribution, based on movement with a predetermined step as a minimum movement unit; displaying the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution in a superimposed state on a screen; specifying a line area and a plane area of the antenna integral-type communication device for the display screen; deriving a complex current distribution of the specified line area and plane area from the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution; deriving directivity from the object shape distribution and the complex current distribution of the line area or the plane area; and displaying the derived directivity.

[0011] The step of deriving a complex current distribution of the specified line area and plane area from the object shape distribution and the two-dimensional electric field distribution or the two-dimensional magnetic field distribution may include performing predetermined weighting for the specified line area and the plane area.

[0012] An electromagnetic wave measuring apparatus of the present invention comprises a probe scanner movable in the x direction, the y direction, the z direction and a rotating direction; a control/record and operation/display unit; and a network analyzer. The probe scanner has a sensor for measuring a three-dimensional shape and a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave attached thereto.

[0013] A method for evaluating and measuring radiation directivity of an electromagnetic wave with an electromagnetic wave measuring apparatus of the present invention has the steps of: measuring and recording an object shape distribution of an antenna to be observed with a sensor for measuring a three-dimensional shape, and measuring and recording a complex transmission characteristic which is a two-dimensional electric field distribution or a two-dimensional magnetic field distribution by adding an RF output signal of a network analyzer to an antenna to be observed, receiving an electromagnetic wave radiated from the antenna with a scanning probe antenna measuring a two-dimensional distribution of an electromagnetic wave and inputting an RF input of the electromagnetic wave to the network analyzer, based on movement with a predetermined step as a minimum movement unit; displaying the object shape distribution and the complex transmission characteristic in a superimposed state on a screen; specifying a line area of the antenna for the display screen; deriving a complex current distribution of the specified line area from the object shape distribution and the complex transmission characteristic; deriving directivity from the object shape distribution and the complex current distribution of the line area; and displaying the derived directivity.

[0014] Therefore, the electromagnetic wave measuring apparatus or the evaluating and measuring method of the electromagnetic wave irradiation directivity with the electromagnetic wave measuring apparatus of the present invention can be used to accurately measure an extreme near field with plane scanning and shape of a device to be evaluated, thereby correctly measuring irradiation directivity from an antenna having a relatively wide directivity or an antenna integral-type communication device.

[0015] Additionally, an electromagnetic wave state in an antenna integral-type communication device such as a portable telephone, which heretofore could not be evaluated without using large measuring equipment such as an RF anechoic chamber, can be evaluated using very compact measuring equipment.

[0016] FIG. 1 is a schematic perspective view showing an electromagnetic wave measuring apparatus which serves asa first embodiment of the present invention;

[0017] FIG. 2 is a diagram showing a data processing sequence for the electromagnetic measuring apparatus which serves as the first embodiment of the present invention;

[0018] FIG. 3 is a diagram which displays an object shape distribution of a portable telephone and an interference complex data distribution which is a two-dimensional field distribution in a superimposed state;

[0019] FIG. 4 is a diagram which displays an object shape distribution of the portable telephone and an interference complex data distribution which is a two-dimensional field distribution in a superimposed state;

[0020] FIG. 5 is a diagram for specifying a line area (for example, a linear portion of the antenna of the portable telephone) and a plane area (for example, a housing portion of the portable telephone) for a display screen;

[0021] FIG. 6 is a diagram for specifying only the line area(for example, the linear portion of the antenna of the portable telephone) for the display screen;

[0022] FIG. 7 is a diagram for specifying only the plane area (for example, the housing portion of the portable telephone) for the display screen;

[0023] FIG. 8 is a diagram showing a radar chart of radiation directivity when the line area (for example, the linear portion of the antenna of the portable telephone) and the plane area (for example, the housing portion of the portable telephone) are specified for the display screen;

[0024] FIG. 9 is a diagram showing a radar chart of radiation directivity when only the line area (for example, the linear portion of antenna of the portable telephone) is specified for the display screen;

[0025] FIG. 10 is a diagram showing a radar chart of radiation directivity when only the plane area (for example, the housing portion of the portable telephone) is specified for the display screen;

[0026] FIG. 11 is a diagram showing a plane distribution of a horizontal component in an electric field at a reproduction height z=60 cm derived from a field distribution measured at a height of x direction movable scanning probe antenna h=1.5 cm;

[0027] FIG. 12 is a diagram showing a plane distribution of a vertical component in an electric field at a reproduction height z=60 cm derived from a field distribution measured at a height of x direction movable scanning probe antenna h=1.5 cm; and

[0028] FIG. 13 is a schematic perspective view showing an electromagnetic wave measuring apparatus which serves as a second embodiment of the present invention.

[0029] Embodiments of the present invention will be hereinafter described with reference to accompanying drawings.

[0030] (First Embodiment of the Present Invention)

[0031] FIG. 1 is a schematic perspective view showing an electromagnetic wave measuring apparatus which serves as a first embodiment of the present invention. The electromagnetic wave measuring apparatus of the first embodiment of the present invention comprises probe scanner 1 having x direction movable probe 1aand y direction movable stage 1b;control/record and operation/display unit 2; interference measuring unit 3; and level detector 4. A sensor for measuring a three-dimensional shape 1csuch as a laser displacement meter and x direction movable scanning probe antenna 1dare attached to X direction movable prove 1a. X direction movable scanning probe antenna 1dis rotatable in φ direction. For interference measuring unit 3, an apparatus disclosed in Japanese Patent Laid-open Publication No.9-133721 may be used.

[0032] Next, description will be made on operation of the electromagnetic wave measuring apparatus serving as the first embodiment of the present invention.

[0033] First, an antenna integral-type communication device to be observed, for example portable telephone 5, is placed on y direction movable stage 1bin a connecting state.

[0034] Next, a fixed probe antenna 6 is placed at a position (on the same y direction movable stage 1b) such that relative positional relationship with portable telephone 5 to be observed is not changed.

[0035] Then, x direction movable scanning probe antenna 1dis used to measure an interference complex data distribution which is a two-dimension field distribution (distribution of an electric field or magnetic field) of portable telephone 5 to be observed. Since the field distribution has directivity, it is required to measure the field distribution separately in two directions of φ=0° and φ=90°, respectively, as expressed by the following equation:

[0036] {dot over (E)}(x,y,φ=0°) and {dot over (E)}(x,y,φ=90°)

[0037] In measuring the field distribution, when a transmission power supply repeats ON/OFF over time as in a TDMA mode or the like, level detector 4 is used to synchronize with a measurement timing. When an average level variation occurs, an amplitude in the interference complex data is corrected with an output value of level detector 4.

[0038] Simultaneously with, or separately from the above-mentioned field distribution measurement, object shape distribution H (x, y) of portable telephone 5 to be observed is measured using a sensor for measuring a three-dimensional shape 1csuch as a laser displacement meter.

[0039] Next, description will be made on a data processing sequence for the electromagnetic wave measuring apparatus serving as the first embodiment of the present invention with reference to FIG. 2.

[0040] First, x direction movable probe 1aand y direction movable stage 1bare moved with dxy step as a minimum movement unit, thereby measuring and recording (S1) object shape distribution H (x, y) of portable telephone to be observed and the interference complex data distribution which is the two-dimension distribution, expressed by the following equation:

[0041] {dot over (E)}(x,y,φ=0°) and {dot over (E)}(x,y,φ=90°)

[0042] Next, the above-mentioned object shape distribution H (x, y) and the interference complex data distribution, expressed by the following equation, are superimposed and displayed (S2) (FIG. 3 and FIG. 4):

[0043] {dot over (E)}(x,y,φ=0°) and {dot over (E)}(x,y,φ=90°)

[0044] In FIG. 3 and FIG. 4,

[0045] minimum movement unit: dxy=3.9 mm

[0046] measurement range: 25 cm×25 cm

[0047] measurement frequency: f=2 GHz

[0048] wavelength of observed radio wave: λ=15 cm and

[0049] height of x direction movable scanning probe antenna: h=1.5 cm.

[0050] Next, a line area (for example, linear portion of antenna 5aof portable telephone 5) and a plane area (for example, housing portion 5bof portable telephone 5) are specified for a display screen (S3) (FIG. 5 to FIG. 7).

[0051] Next, a complex current distribution of the above-mentioned specified line area and the plane area, expressed by the following:

[0052] {dot over (I)}(x,y,φ)

[0053] is derived (S4) from object shape distribution H (x, y) and the interference complex data distribution expressed by the following:

[0054] {dot over (E)}(x,y,φ)

[0055] Assuming that the height of x direction movable scanning probe antenna is h, and the sensitivity of the probe antenna at the measurement frequency is g(f), the following operation is performed, for example.

[0056] In the line area, the following operation is performed:

[0057] {dot over (I)}(x,y,φ)≅{dot over (E)}(x,y,φ)·d_xy·(h−H_(x,y))²/g_(f)  (1)

[0058] In the plane area, the following operation is

[0059] performed:

[0060] {dot over (I)}(x,y,φ)≅{dot over (E)}(x,y,φ)·(d_xy)²·(h−H_(x,y))/g_(f)  (2)

[0061] In an area other than the above-mentioned line area and the plane area, the following is assumed:

[0062] {dot over (I)}(x,y,φ)=0

[0063] In the above-mentioned (1) equation, dxy·(h−H(x,y))²represents weighting for the line area. In the above-mentioned (2) equation, (dxy)²·(h−H(x,y)) represents weighting for the plane area.

[0064] Next, directivity is derived (S5) from object shape distribution H (x, y) and the complex current distribution of the line area or the plane area expressed by the following:

[0065] {dot over (I)}(x,y,φ)

[0066] For example, assuming that λ is a wavelength of the observed radio wave, the following directivity is derived.

[0067] directivity of a horizontal component in a horizontal plane: ${\stackrel{.}{G}}_{\mathrm{HH}\left(\theta \right)}\cong \left(\sum _x\sum _y{\stackrel{.}{I}}_{\left(x,y,\varphi =0°\right)}·e^{j2\pi \left(-x·\sin \theta +H\left(x,y\right)·\cos \theta \right)/\lambda }\right)·\cos \theta$

[0068] directivity of a vertical component in the horizontal plane: ${\stackrel{.}{G}}_{\mathrm{HV}\left(\theta \right)}\cong \left(\sum _x\sum _y{\stackrel{.}{I}}_{\left(x,y,\varphi =0°\right)}·e^{j2\pi \left(-x·\sin \theta +H\left(x,y\right)·\cos \theta \right)/\lambda }\right)$

[0069] directivity of a horizontal component in a vertical plane: ${\stackrel{.}{G}}_{\mathrm{VH}\left(\theta \right)}\cong \left(\sum _x\sum _y{\stackrel{.}{I}}_{\left(x,y,\varphi =0°\right)}·e^{j2\pi \left(-y·\sin \theta +H\left(x,y\right)·\cos \theta \right)/\lambda }\right)$

[0070] directivity of a vertical component in the vertical plane: ${\stackrel{.}{G}}_{\mathrm{VV}\left(\theta \right)}\cong \left(\sum _x\sum _y{\stackrel{.}{I}}_{\left(x,y,\varphi =0°\right)}·e^{j2\pi \left(-x·\sin \theta +H\left(x,y\right)·\cos \theta \right)/\lambda }\right)·\cos \theta$

[0071] Next, the above-mentioned derived directivity for each component, expressed by the following, is displayed (S6) (FIG. 8 to FIG. 10):

[0072] |{dot over (G)}_HH(θ)|, |{dot over (G)}_HV(θ)|, |{dot over (G)}_VH(θ)|, |{dot over (G)}_VV(θ)|

[0073] Next, this procedure returns to S3 (S7) and simulation is made for another combination of a line and plane, for example, when a housing current is absent.

[0074] It should be noted that the equations (1), (2) for deriving the complex current distribution of the line area and the plane area at S4, expressed by the following:

[0075] {dot over (I)}(x,y,φ)

[0076] from object shape distribution H (x, y) and the interference complex data distribution, expressed by the following:

[0077] {dot over (E)}(x,y,φ)

[0078] are approximate expressions and the accuracy thereof may be increased in the following manner.

[0079] Between a current distribution assumed in an arbitrary area, expressed by the following:

[0080] [{dot over (I)}_n]

[0081] and a voltage distribution, expressed by the following:

[0082] [{dot over (V)}_n]

[0083] the following equation holds:

[0084] [{dot over (Z)}_mn][{dot over (I)}_n]=[V_m]

[0085] where the following term:

[0086] [{dot over (Z)}_mn]

[0087] represents a mutual impedance between divided current segments (probe antenna or object to be observed) and self-impedance matrix. The following:

[0088] [{dot over (Z)}_mn]

[0089] can be derived through an analytical or numerical integration (moment methods: R. F.Harrington, “Field Computation by Moment Methods”, IEEE Press, 1993). Thus, it is also possible to derive a correct complex proportion factor between the assumed current distribution area and the probe antenna and use the derived factor.

[0090] While S5 shows a case where particular directivity is derived, directivity for an arbitrary direction expressed by the following may be derived:

[0091] F

[0092] The distribution of a current flowing in arbitrary area V is expressed by the following:

[0093] {dot over (I)}_(p)

[0094] and the directivity with the current can be derived, for a unit direction vector expressed by the following:

[0095] F

[0096] using the following vector effective length:

[0097] le

[0098] with the following equation: $\begin{array}{c}{l}_e\left(F\right)=F\times ({\int }_v\stackrel{.}{I}\left(\rho \right)e^{j2\mathrm{\pi \rho }F/\lambda }dv\times F\\ E_{\left(F\right)}=-\frac{l_2{z}_n}{4\pi }\frac{e^{-j\mathrm{hr}}}{r}{l}_{e\left(F\right)}\end{array}$

[0099] Incidentally, k=2π/λ, Z₀=120π, r=(x²+y²+z²)^½ and:

[0100] F=r·F

[0101] FIG. 11 shows a plane distribution of a horizontal component in an electric field in a reproduction height: z=60 cm derived from the field distribution measured at the height of x direction movable scanning probe antenna: h=1.5 cm.

[0102] FIG. 12 shows a plane distribution of a vertical component in an electric field in a reproduction height: z=60 cm derived from the field distribution measured at the height of x direction movable scanning probe antenna: h=1.5 cm.

[0103] Incidentally, while in the first embodiment of the present invention, probe scanner 1 having x direction movable probe 1aand y direction movable stage 1bis used, the present invention can be implemented with any probe scanner as long as it is movable in the x direction, the y direction, the z direction and a rotating direction.

[0104] (Second Embodiment of the Present Invention)

[0105] FIG. 13 is a schematic perspective view showing an electromagnetic wave measuring apparatus which serves as a second embodiment of the present invention. The electromagnetic wave measuring apparatus of the second embodiment of the present invention comprises probe scanner 1 having x direction movable probe 1aand y direction movable stage 1b;control/record and operation/display unit 2; and network analyzer 7. A sensor for measuring a three-dimensional shape 1csuch as a laser displacement meter and x direction movable probe antenna 1dare attached to X direction movable probe 1a.

[0106] If an object to be observed operates with an external input, network analyzer 7 or the like may beused to measure a complex transmission characteristic, expressed by the following, like the antenna shown in FIG. 13 for example:

[0107] {dot over (E)}_(x,y,φ)

[0108] Incidentally, while in the second embodiment of the present invention, probe scanner 1 having x direction movable probe 1aand y direction movable stage 1bis used, the present invention can be implemented with any probe scanner as long as it is movable in the x direction, the y direction, the z direction and a rotating direction.

[0109] As described above, the present invention has the following effects.

[0110] A first effect is that the electromagnetic wave measuring apparatus or the evaluating and measuring method of the electromagnetic wave irradiation directivity with the electromagnetic wave measuring apparatus of the present invention can be used to accurately measure an extreme near field with plane scanning and shape of a device to be evaluated, thereby correctly measuring irradiation directivity from an antenna having a relatively wide directivity or an antenna integral-type communication device.

[0111] A second effect is that an electromagnetic wave state in an antenna integral-type communication device such as a portable telephone, which could not be evaluated without using large measuring equipment such as an RF anechoic chamber, can be evaluated using very compact measuring equipment.