JPH10232252A - Hologram observation method of three-dimensional wave source distribution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a three-dimensional wave source distribution accurately even when a wave source is close to a hologram observation plane. SOLUTION: Hologram observation is performed by two frequency method (Step 101) and a hologram image is reproduced (Step 102). A three-dimensional wave source is located from a reproduced hologram image (Step 104) and a virtual unit wave source is set at the determined location of wave source and the observed waves are synthesized (Step 105). Subsequently, the hologram image of synthesized observation wave is reproduced (Step 106) and the wave source intensity of an actually measured hologram image is divided by that of the hologram image obtained from the synthesized observation wave thus determining the true complex amplitude of the wave source (Step 107). Such are of the hologram image obtained from the synthesized observation wave as having intensity higher than a specified level is removed from the searching range (Step 108) and the process from step 104 to step 107 is repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for observing a radio wave hologram or a sound wave hologram, and more particularly to a method for measuring a propagation of an electromagnetic wave or a sound wave, in which a reflected wave can be accurately evaluated, and a three-dimensional wave source distribution can be accurately obtained. Observation methods that can be used.

[0002]

2. Description of the Related Art Visualization of an electromagnetic wave source by the technique of a radio hologram using the coherence of an electromagnetic wave has been put into practical use. For example, in order to measure a high-frequency current distribution in an observation target and to reduce unnecessary electromagnetic wave radiation. It is used. A hologram can be similarly obtained using not only radio waves but also sound waves, which is useful for visualizing a sound source distribution and specifying a noise source.

In reproducing a wave source image using a hologram, two-dimensional interference observation is performed to obtain a two-dimensional complex interferogram (complex hologram), and by reproducing the interferogram, a wave source distribution is displayed. More specifically, when analyzing an electromagnetic wave source, a certain observation frequency is set, and a fixed observation antenna and a moving (scanning) antenna are used as wave sensors, and a scanning observation surface is set at a position away from the observation target. Then, while moving the moving antenna in this scanning observation plane, the signals from the observation target are received by both antennas, and when the moving antenna is at each point in the scanning observation plane, the signals from the two antennas at that point are received. The complex interferogram is obtained by obtaining the complex correlation value of the signal. As active observation, a reference wave may be radiated from one antenna and a reference wave may be received by the other antenna, and a complex correlation value between the original reference wave and the received signal may be obtained.

The method using a radio wave hologram or a sound wave hologram can be applied not only to observation of a wave source distribution on a two-dimensional surface but also to measurement of an electric field intensity distribution in a three-dimensional space. Conventionally, for example, under the condition that the Fresnel approximation holds, the method of Aoki (Aoki et al .: “Numerical two-dimensional Fresnel transform method”, IEICE B, Vol. J57-B, No. 8, pp. 511-518, 1
August 974), the distance between the scanning observation surface and the wave source surface is z _s , the size of the scanning observation surface is D × D, and the focal length of the wave source image reproduction is z _b , where z _s ≦ D. _A plurality of reconstructed images are obtained by changing _b, and a three-dimensional wave source distribution is obtained from the plurality of reconstructed images. In this method, there are many restrictions in implementation, such as changing z _b under the condition of z _s ≦ D.

Therefore, the present inventor has disclosed in Japanese Patent Application Laid-Open No. 8-201445.
In the publication No. 9, in a region to which the Fraunhofer approximation applies, if there are two reproduced images observed at different frequencies, there is no need to change the constraint D due to the size D of the scanning observation surface or change z _b, and to obtain a three-dimensional image. It is shown that the source distribution can be estimated. In the method disclosed in Japanese Patent Application Laid-Open No. 8-201459, a two-dimensional interferogram is acquired at two frequencies to reproduce a wave source image at a position where the primary wave source can be seen, and from the scanning observation plane to each reproduced wave source image. In consideration of the propagation delay time, the wave sources are rearranged in a three-dimensional space, and the waves from these rearranged wave sources are re-emitted and combined to estimate the three-dimensional wave intensity. Hereinafter, this method will be described. First, the hologram observation model will be described with reference to FIG.

A hologram observation plane 301 is set on an xy plane (z = 0) including the origin O, and the hologram observation plane 301 is set.
At the position z _s away from the wave source in the z-axis direction.
Suppose that exists. The position vector of the observation point on the hologram observation surface 301 and the position vector of the current source on the wave source

[0007]

[Outside 1] Then the current source

[0008]

[Outside 2] Electric field generated at the observation point

[0009]

[Outside 3] Is the Dyadic Green function of 3D free space

[0010]

[Outside 4] Using,

[0011]

(Equation 1) It is expressed as Here, let the vector effective length of the receiving antenna be l _e , and the distance r between the observation point and the current source is the observation frequency f
For a wavelength λ (= c / f: c is the speed of light) corresponding to
Assuming that r≫λ, the received voltage at the antenna is g, as a constant,

[0012]

(Equation 2) Is represented by Therefore, the received voltage at the observation point is

[0013]

(Equation 3) It is. Vh and Vv, respectively, a horizontal polarization antenna received voltage and the vertical polarization antenna reception voltage, l ^h _e and l ^v _e, respectively, in a horizontal polarization antenna vector effective length and the vertical polarization antenna vector effective length is there.

[0014]

(Equation 4) Then, equation (1.3) becomes

[0015]

(Equation 5) Will be represented.

FIG. 8 is a view for explaining a mirror image observation model to which the above-described hologram observation model is applied. A primary source current J ₀ (x ₀ , y ₀ , z ₀ ) is located at a point 402 in front of the hologram observation surface 401 (z = 0) (positive direction of the z-axis).
It is assumed that the reflection surface 403 is arranged so as to be parallel to the z axis and the y axis. Observation electric field E _p in the observation point p on the hologram observation plane _{401 (x a, y a)} , a mirror image point 904 of the point 402 by the reflecting surface 403 when viewed from the observation point p, when present in Kagamizoten 404 The visible mirror image source current is J (x _s ,
y _s , z _s ). The distance between the origin O and the point 402 is r ₀ ,
The distance from the observation point p to the mirror image point 404 is r ′, and the distance from the origin O to the mirror image point 404 is

[0017]

[Outside 5] And

By the Fraunhofer approximation,

[0019]

(Equation 6) As

[0020]

(Equation 7) Holds. _{However, u = k 0 x s /} z s, v = k 0 y s /
z _s and k ₀ are wave numbers in free space, and μ ₀ is magnetic permeability in vacuum. From equations (2.1) and (2.3), the propagation delay time is

[0021]

(Equation 8) Becomes Therefore, from hologram observation

[0022]

(Equation 9) Is obtained.

Now, two frequencies of angular frequencies ω ₁ and ω ₂ (ω ₁ ≠
Assume that a reproduced image is obtained at ω ₂ ).

[0024]

(Equation 10) Then

[0025]

[Equation 11] further

[0026]

(Equation 12) Holds. Therefore, the received electric field at any point in the three-dimensional space is

[0027]

(Equation 13) Will be represented. That is, by reproducing the wave source images at the two frequencies, the wave intensity in the three-dimensional space can be estimated, and the three-dimensional distribution of the wave can be known.

However, the above-mentioned Japanese Patent Application Laid-Open No. 8-201
In the case of the conventional method described in Japanese Patent No. 459, an error caused by an error in the vector effective length of the receiving antenna or the three-dimensional dyadic Green function may not be ignored. This error becomes larger as the distance between the hologram observation surface and the wave source point becomes shorter, and the wave source point becomes z as viewed from the observation surface.
The larger the angle with the axis, the larger. That is, in the above-described conventional method, since strict probe correction is not performed and the Fraunhofer approximation is used, a large error may occur particularly in the estimated amplitude of the wave source close to the observation surface. FIG. 9A is a diagram showing the reproduction amplitude of the wave source according to the conventional method, and FIG. 9B is a diagram showing the reproduction amplitude when only the directivity (considering the effective vector length) of the antenna is compensated. In FIGS. 9A and 9B, the level is 1.0.
The closer to, the more accurate the observations are made. As is apparent from these figures, according to the above-described conventional method, an observation error of about 10 dB occurs in estimating the wave source distribution in the three-dimensional space.
An error of about dB remains.

[0029]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hologram observation method capable of accurately estimating a wave source distribution in a three-dimensional space even when the wave source is close to a hologram observation surface. To provide.

[0030]

According to the present invention, there is provided a hologram observing method for estimating a three-dimensional wave source distribution by hologram observation.
A first step of performing hologram observation at different frequencies as described above and reproducing an image of a hologram at each frequency, and a second step of selecting a wave source to be extracted from a wave source image in the reproduced image as an area. A third step of obtaining the three-dimensional coordinates of the selected wave source in the area, and synthesizing the observation wave assuming that the virtual unit wave source is located at the three-dimensional coordinates obtained in the third step, and reproducing the hologram image from the synthesis result And a fifth step of obtaining a true source intensity from a ratio between the intensity in the image reproduced in the fourth step and the actual intensity of the source selected in the second step. .

In the present invention, a region having an intensity equal to or more than a predetermined value in the image reproduced in the fourth step is excluded from the area selected in the second step, and the third step and the fourth step are performed.
And the fifth step are desirably repeated.

In the fourth step, it is preferable to combine the observation waves with, for example, the directivity of an antenna used for hologram observation and the spread in a reproduced image.

In the present invention, the observation wave is, for example, an observation electric field observed on a hologram observation surface when observing a radio wave hologram, and is observed when an acoustic hologram is observed. It is a sound field. The virtual unit wave source is a virtual wave source whose intensity is a predetermined value (preferably, the predetermined value is 1 for easy calculation), and performs observation of a radio hologram. If so, it means a virtual unit current source or the like.

In the present invention, assuming that the virtual unit wave source is located at the three-dimensional wave source position obtained by the hologram observation, the observation wave is synthesized to obtain a hologram image, and the hologram image is actually measured by the intensity of the hologram image by the virtual unit wave source. By normalizing the other source intensity, the true source amplitude is obtained. Further, by repeatedly performing an operation excluding an area in which the intensity is equal to or more than a predetermined value in the reproduced image obtained from the virtual unit wave source, it is possible to prevent the extraction of the pseudo wave source due to the spread of the image, and to more accurately obtain the wave source amplitude and Wave source distribution can be obtained.

[0035]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a hologram observation device to which a hologram observation method according to one embodiment of the present invention is applied. Here, a case in which a radio hologram is observed to obtain a three-dimensional wave source distribution will be described.

This hologram observation apparatus is for observing a hologram of an unmodulated wave, and has an xy plane (z = 0).
And a hologram observation surface 12 disposed therein. The size of the hologram observation surface 12 is, for example, 58 cm square, and the scanning antenna 13 for observing both the vertical (V) and horizontal (H) polarization components is scanned on the hologram observation surface 12 by a scanning mechanism (not shown). Move in 9 mm increments.
In addition to the scanning antenna 13 on the hologram observation surface 13, a fixed antenna 14 that does not move is arranged. Incidentally, to represent the position of the scanning antenna 13 of the on the hologram observation plane 12 at (x _a, y _a).

The reception signal of the vertical polarization component and the horizontal polarization component from the scanning antenna 13 is input to the changeover switch 15, and one of the vertical component and the horizontal component is selected and input to the spectrum analyzer 16. On the other hand, a signal received from the fixed antenna 17 is input to another spectrum analyzer 17. These spectrum analyzers 16 and 17 pass only the components of the desired frequency band in the signals received from the scanning antenna 13 and the fixed antenna 14, respectively (for example, the bandwidth BW = 1 kHz).
And an intermediate frequency IF (for example, 21.4 MH
z) for frequency conversion. For example,
Such spectrum analyzers 16 and 17 can be realized by operating in a zero-span mode with the phase locked to the reference frequency signal f _req using a spectrum analyzer R3271 of Advantest or the like. R327 of Advantest Co., Ltd. as a spectrum analyzer
In the case where 1 is used, since a reference frequency source of 10 MHz is actually built in, one spectrum analyzer 16 is used.
In this case, a signal from a reference frequency source built in the above-mentioned is used as the above-mentioned reference frequency signal f _req , and this reference frequency signal f _req may be supplied to the other spectrum analyzer 17.

Mixers 18 and 19 are provided on the output sides of the spectrum analyzers 16 and 17, respectively. The mixers 18 and 19 are supplied with a local oscillation frequency of, for example, 22.4 MHz from a local oscillator 20. Thus, the signal of the intermediate frequency IF is frequency-converted into a signal of, for example, about 1 MHz. The local oscillator 20 operates with the phase locked to the reference frequency f _req . On the output side of each of the mixers 18 and 19, low-pass filters (LPFs) 21 and 22 for removing unnecessary high-frequency components from the outputs of the mixers 18 and 19 are provided, respectively. These are input to the Fourier transform units 23 and 24, respectively.
The Fourier transform units 23 and 24 include low-pass filters 21 and 2
2 is subjected to complex discrete Fourier transform, and a clock signal having a frequency of, for example, 10.24 MHz is supplied from a clock oscillator 25 as a sampling clock. The clock oscillator 25 also has the reference frequency f
It operates with phase locked to _req . By these two Fourier transform units 23 and 24, a two-channel synthetic Fourier integration (SFI) is performed.
n) will be performed.

The Fourier corresponding to the scanning antenna 13
The output from the conversion unit 23 is S_m(x_a, y _a, f_s) And (f_sIs
Frequency), the Fourier transform corresponding to the fixed antenna 14
The output from the conversion unit 24 is S_r(f_s), The complex hologram
Mu C (x_a, y_a)

[0040]

[Equation 14] Is represented by

When a modulated wave is used, a hologram observation device having the configuration shown in FIG. 2 can be used.
The hologram observation device shown in FIG. 2 includes a hologram observation surface 31 arranged in the xy plane. The size of the hologram observation surface 31 is, for example, 58 cm square,
A scanning antenna 33 for observing both (V) and horizontal (H) polarization components moves on the hologram observation surface 31 at intervals of, for example, 9 mm by a scanning mechanism (not shown). In addition to the scanning antenna 33, a fixed antenna 34 and a radiation antenna 35 are arranged. The radiation antenna 35 is connected to a signal source 36. These fixed antennas 3
4. The radiation antenna 35 and the signal source 36 are used to obtain a reference wave for hologram observation. By the changeover switch 37, one of the received signal of the fixed antenna 34 and the signal from the signal source 36 is changed. , And a reference wave signal.

The received signal of the vertical polarization component and the horizontal polarization component from the scanning antenna 33 is input to the changeover switch 38, one of the vertical component and the horizontal component is selected, and is input to the spectrum analyzer 39. The changeover switch 3 output from the fixed antenna 34 and the signal source 36
The reference wave signal selected by 7 is input to another spectrum analyzer 40. These spectrum analyzers 39 and 40 are respectively provided with a scanning antenna 33.
Only the components of the desired frequency band out of the received signal and the reference wave signal from the receiver (for example, bandwidth BW _s = 20 k)
Hz) and an intermediate frequency IF (for example, 21.
4 MHz), for example, a spectrum analyzer R3 manufactured by Advantest Corporation.
271 and the like, and the operation is performed in the zero span mode with the phase locked to the reference frequency signal f _req . Here, assuming that the spectrum analyzer 40 has a built-in reference frequency source of, for example, 10 MHz,
A signal from a reference frequency source incorporated in the spectrum analyzer 40 is used as the above-mentioned reference frequency signal f _req , and the other spectrum analyzer 39 is supplied with the reference frequency signal f _req .

Mixers 41 and 42 are provided on the output sides of the spectrum analyzers 39 and 40, respectively. The mixers 41 and 42 are supplied with local oscillation frequencies of, for example, 6 MHz and 7 MHz from the local oscillators 43 and 44 respectively, and convert the signals into different frequencies having a frequency difference of about 1 MHz, for example, signals of about 15.4 MHz and 14.4 MHz, respectively. The signal of the intermediate frequency IF from each of the spectrum analyzers 39 and 40 is frequency-converted. Local oscillator 43,4
4 operates in phase locked to the reference frequency f _req . The output side of the mixer 41, in order to take out only a signal of a predetermined frequency component from the output of the mixer 41, respectively, a band-pass filter for example bandwidth BW _s of about 20 KHz (BPF) 45, 46 , Respectively, and a multiplier 47 to which the outputs of the band-pass filters 45 and 46 are input together. An output from the multiplier 47 is output to a band-pass filter 48 (for example, a center frequency f _o).
= 1 MHz, bandwidth BW _c = 1 kHz), and the SFI vector detector 49 together with the reference frequency signal f _req.
To enter. SFI vector detector 49, synthesis Fourier integral performs vector detection of the input signal (output of multiplier 47), complex hologram C (x _a, y _a) represented by the following equation and outputs the.

[0044]

(Equation 15) _{Here, Sm (x a, y a} , f) is the received signal of the scanning antenna 33, S _r (f) is a reference wave signal. Actually, the multiplication in the integral equation in equation (4) is performed by the multiplier 47,
By performing the vector detection by the FI vector detector 49, the real component and the imaginary component of the complex hologram are obtained as the cosine component and the sine component extracted by the SFI vector detector 49, respectively.

The complex hologram calculated in this way is input to the personal computer 50 and stored. The personal computer 50, the position of the scanning antenna 33 of the in the hologram observation plane 31 (x _a, y _a) and also controls the.

FIG. 3 is a block diagram showing an example of the configuration of the SFI vector detector 49.

The digital synthesizer 61 which reference frequency signal f _ref is input is provided, the digital synthesizer 61, as shown, the reference frequency signal f _ref
, A digital signal whose numerical value changes with time in a stepwise manner is generated. This digital signal is supplied to one sine wave memory 6
4 and to the other sine wave memory 65 via the digital adder 63. In the digital adder 63, phase data corresponding to the amount of phase advance is added. The sine wave memories 64 and 65 store the value of the sine wave at each time obtained by equally dividing one cycle of the sine wave, and the value changes in synchronization with the clock at a fixed increment. By providing a digital signal, a digital signal whose value changes corresponding to a sine wave is output. Sine wave memory 64,6
5 are provided with analog / digital multipliers 66 and 67 for multiplying the digital signal and the analog signal, respectively.
65 outputs are analog-digital multipliers 66 and 6 respectively.
Enter 7

The input signal input from the multiplier 47 (see FIG. 2) to the SFI vector detector 49 via the band-pass filter 48 is input to the analog-side multipliers 66 and 67 via the band-pass filter 62. It is supplied to the terminal. Outputs of the analog / digital multipliers 66 and 67 are input to analog / digital converters (A / D converters) 70 and 71 via integrators 68 and 69, respectively.
Then, the output of each of the analog-to-digital converters 70 and 71 is input to the arithmetic unit 72, and the vector detection result is calculated.

[0049] Finally, by using the digital synthesizer 61 and the sine wave memory 64 and 65, the occurrence of any frequency where the phase to the reference frequency signal f _ref is locked sine wave as a reference signal at the SFI vector detector 49 Let me. Then, each analog-digital multiplier 66,
The reference numeral 67 multiplies the input signal by a reference signal of, for example, 1 MHz thus synthesized from the reference frequency signal f _ref , and the multiplication result is integrated by the integrators 68 and 69. Therefore, by setting the phase data to be added by the digital adder 63 to a value corresponding to the phase shift amount π / 4, a cosine component and a sine component are extracted from the input signal at a frequency of 1 MHz, and vector detection is performed. It has been done.

Now, a procedure for performing the observation method of the present invention using the above-described hologram observation apparatus will be described. FIG. 4 is a flowchart showing the processing procedure.

First, two hologram observation devices are used.
Frequency (e.g., 10 GHz and 10.005 GHz)
A hologram is observed (step 101). The above formula
Observed dual-frequency hologram using (2.5) to (2.10)
From the reconstructed image, I (u, v), x _s(u, v), y_s(u, v),
z_s(u, v) is calculated (step 102). And
In the (u, v) image space,
Marking to indicate that it is a search target (image extraction
A rear map is set) (step 103).

Next, among the images to be searched by the image extraction area map, the image I giving the maximum level
(u _m , v _m ), and the source coordinates (x _s ′, y _s ′,
z _s ') is obtained (step 104). That is,

[0053]

Equation 16] _{x s' = x s (u} m, v m), y s' = y s (u m, v m), z s' = z s (u m, v m) to. Then, the coordinate _{(x s', y s'} , z s') a virtual unit current sources are arranged as a virtual unit wave source, the above-mentioned equation (1.1)
The observation electric field is synthesized by using (1.6) (step 10).
5). By using the equations (1.1) to (1.6), the influence of the spread of the reproduced image and the directivity of the receiving antenna is considered. Next, the hologram image corresponding to the observation electric field synthesized in step 105 is reproduced by equation (2.5), and is set to P (u, v) (step 106).

Subsequently, a temporary wave placed at the same position as the true wave source
From the comparison between the reconstructed intensity of the hypothetical unit wave source and the observed reconstructed image, the true
The wave source intensity is obtained (step 107). That is,
(x_s', y _s', z_s') Is the complex amplitude of the true source at I (u_m,
v_m) / P (u_m, v_m). Find true source strength
Then, the value of P (u, v) in the synthesized hologram is predicted.
Search for areas above a certain level (image extraction limit)
And exclude the searched area from the image extraction area map.
(Step 108). This is a pseudo
This is for preventing the extraction of the wave source. At step 108
Is generally true after executing the processing up to step 107.
The region corresponding to the source for which the complex amplitude of
When searching for the next source, the image of the source
Prevents the effect of glue.

Thereafter, it is determined whether the termination condition is satisfied (step 109). If the end condition is not satisfied, the process returns to step 104 to repeat the above-described processing. If the end condition is satisfied, a list of the extracted complex amplitudes and the coordinates of the true wave source is output (step 104). 110), and the process ends. As the end condition in step 109, any appropriate condition can be adopted. For example, when a predetermined number or more of wave sources are extracted,
Image size of the extraction area drops below a certain percentage compared to the entire, or extraction target level I (u _m, v _m) is equal to or less than a predetermined value (for example above image extraction limit of), such as Conditions can be used.

FIG. 5A shows a result of simulating a wave source amplitude measurement error when the method according to the present embodiment is used. Here, the size of the hologram observation plane 12 and 57cm square, the observation frequency f _s and 10 GHz, showing a wave source amplitude measurement error in case of performing a two-frequency holographic observations and y _s = 1 m. In the conventional case [Fig. 9 (a),
It can be seen that the error is significantly reduced according to the present embodiment as compared with the reproduction amplitude of (b)].

FIG. 5B shows the result of actually observing the floor reflection coefficient by the two-frequency hologram method of this embodiment. Here, it is assumed that the light is incident on the floor surface in the TE mode, and the complex refractive index of the floor surface reflection is 2.55-j0.0.
04. The size of the hologram observation surface was 57 cm square, the observation frequency was 10 GHz, the dipole antenna serving as a wave source was arranged at a position 1 m above the floor, and x _s = 0.4.
m, z _s = 3.0 to 5.4 m, and the ratio between the mirror image source intensity and the primary source intensity was observed. According to the method of the present embodiment,
It can be seen that there is almost no difference between the calculated value and the measured value.

Further, regarding the frequency difference Δf between the two frequencies used in the two-frequency hologram observation and the distance measurement error,
It was studied by computer simulation. The position of the primary wave source is x _o = y ₀ = 0, z ₀ = 5 m, z _s = 8 m, the size of the hologram observation surface is 57 cm square, and the observation frequency is f _s.
Was set to 10 GHz and the S / N (signal noise ratio) was set to 8 dB. As an error in the distance R _s to the origin O and the mirror image wave sources, FIG 6 Results (a), shown in (b). FIG. 6A shows the result when Δf is set to 5 MHz, and FIG. 6B shows the result when Δf is set to 20 MHz. Under the condition of S / N = 8 dB, if Δf = 5 MHz, the distance range is ± 30 m, the error range is 40 cm, and Δf = 2
If the frequency is 0 MHz, the range is ± 7.5 m and the error range is 10c.
m.

As described above, by using the two-frequency hologram observation, as shown by the actual measurement values and the simulation examples, the frequency difference between the two frequencies used for the observation can be obtained even under the condition that the observation includes noise. If .DELTA.f and the observation distance range are appropriately selected, extremely good distance measurement accuracy can be obtained. The present invention compensates for various observation errors by using such high ranging accuracy of dual-frequency hologram observation. The vector effective length of the probe antenna can be accurately obtained by using the moment method, and the transfer function between the observation surface and the wave source point can be accurately obtained by using a three-dimensional dyadic Green's function.

Therefore, in the present invention, the formulas (2.1) to (2.10)
Is used to estimate the position of the wave source, and equations (1.1) to (1.6) are used to estimate the observed value for the unit current.
The result of image reconstruction using (5) is compared with the image reconstruction result of actual observation. By performing such a comparison, it is possible to obtain the true wave source complex amplitude. According to the method of the present invention, as compared with the conventional method whose results are shown in FIG.
As shown in FIG. 5A, the error is increased from the conventional 10 dB.
It is improved to less than 0.5 dB.

In the embodiment described above, step 1
When the observation electric field is synthesized at 05, the equations (1.1) to (1.6)
, The directivity of the antenna and the spread of the reproduced image are considered. The present invention is not limited to this. For example, approximation can be made by treating only the effective vector length in the direction of the wave source viewed from the center of the hologram observation plane (treating the directivity for each wave source into a constant). It is.

Although the present invention has been described with reference to the case of observing a radio wave hologram as an example, it is needless to say that the present invention can be applied to observation of a wave source distribution by another kind of wave, for example, an acoustic hologram. .

[0063]

As described above, according to the present invention, an observation wave (observation electric field, etc.) is synthesized by arranging a virtual unit wave source at a wave source position extracted from an observed hologram image, and a reproduced image based on the synthesis result is obtained. Is compared with the actually measured reproduced image, there is an effect that a true wave source complex amplitude can be obtained. In addition, by repeatedly performing an operation excluding an area in which the intensity is equal to or more than a predetermined value in a reproduced image obtained by synthesizing the observed waves, it is possible to prevent a pseudo wave source from being extracted due to the spread of the image, and to more accurately obtain the wave source amplitude and the like. Wave source distribution can be obtained.

In the analysis of the propagation of electromagnetic waves, it is indispensable to grasp complex multiplex waves for each frequency to be used in order to guarantee wireless communication quality and prevent electromagnetic wave interference problems. According to the present invention, prevention of the above-described trouble and quality assurance are realized by collectively and accurately evaluating a plurality of reflection points and reflection coefficients that cause multiple waves.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a configuration of an observation device used for performing a hologram observation method according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of another configuration of the observation device.

FIG. 3 is a block diagram illustrating an example of a configuration of an SFI vector detector.

FIG. 4 is a flowchart showing a procedure of a hologram observation method according to one embodiment of the present invention.

5A is a diagram showing a result of simulating a wave source amplitude measurement error by the method of the present invention, and FIG. 5B is a diagram showing a result of actually observing a floor reflection coefficient.

FIGS. 6A and 6B are diagrams showing simulation results of a relationship between a frequency difference and a distance measurement error.

FIG. 7 is a diagram illustrating a hologram observation model.

FIG. 8 is a diagram illustrating a mirror image observation model.

FIG. 9A is a diagram illustrating a reproduction amplitude of a wave source according to a conventional method, and FIG. 9B is a diagram illustrating a reproduction amplitude when only the directivity (considering an effective vector length) of an antenna is compensated.

[Explanation of symbols]

 12,31 Hologram observation surface 13,33 Scanning antenna 14,34 Fixed antenna 15,37,38 Changeover switch 16,17,39,40 Spectrum analyzer 18,19,41,42 Mixer 20,43,44 Local oscillator 21,22 Low-pass filter 23,24 Fourier transform unit 25 clock oscillator 35 radiation antenna 36 signal source 45,46,48 band-pass filter 47 multiplier 49 SFI vector detector 50 personal computer 101-110 step

Claims (3)

[Claims] In a hologram observation method for estimating a three-dimensional wave source distribution by hologram observation, a first step of observing holograms at two or more different frequencies and reproducing an image of a hologram at each frequency is provided. A second step of selecting a wave source to be extracted from the wave source image in the image as an area, a third step of obtaining three-dimensional coordinates of the selected wave source in the area, and a third step of obtaining the three-dimensional coordinates in the third step. A fourth step of synthesizing observation waves assuming that a virtual unit wave source is present in the dimensional coordinates, and reproducing a hologram image from the synthesis result; and the intensity in the image reproduced in the fourth step and the second step.
A hologram observing method for a three-dimensional wave source distribution, comprising: obtaining a true wave source intensity from a ratio of the actual wave source selected in the step to the actual intensity. 2. The method according to claim 3, wherein an area whose intensity is equal to or more than a predetermined value in the image reproduced in the fourth step is excluded from the area selected in the second step.
2. The method of observing a hologram of a three-dimensional wave source distribution according to claim 1, wherein the steps (a) and (b) are repeated. 3. The three-dimensional wave source distribution according to claim 1, wherein in the fourth step, observation waves are synthesized in consideration of directivity of a sensor used for hologram observation and spread in a reproduced image. Hologram observation method.