JP3286970B2 - Radio source visualization device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for, for example, measurement of EMC (Electro Magnetic Compatibility) and radio wave sensing, that is, pattern analysis of reflection, refraction, absorption, etc., for visualizing the position of a radio wave source. The present invention relates to a source visualization device.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional radio source visualization apparatus.
The object to be measured 11 including the radio wave generation source that cannot be measured in close contact with the object to be measured 11 is separated by a distance z from the object to be measured 11 in parallel with the object to be measured 11 by the search coil 12 for linear scanning.
Alternatively, two-dimensional scanning is performed manually or automatically, and the output of the search coil 12 is converted into a digital signal by the AD converter 15.
To obtain the distribution map of the received radio wave intensity by taking it into the control display 14 composed of a personal computer.

[0003]

That is, in the prior art, the received radio wave intensity distribution is obtained by scanning the observation surface by using a radio wave intensity meter or a combination of a search coil and a spectrum analyzer. However, the radio wave incident on the electric field strength meter from the radio wave source includes not only a direct wave but also a reflected wave from a ceiling or a floor, and the presence of the reflected wave cannot be known.

When a plurality of radio sources exist, interference occurs between the plurality of radio waves. Therefore, even if the interval l between the radio sources is larger than the wavelength λ of the radio wave of the radio source, the DUT 11, ie, the radio source, When the distance z from the observation surface 13 is larger than the radio wave wavelength λ, an image of the radio wave source cannot be obtained. Further, since a plurality of radio wave fronts are synthesized, the distance l between the radio wave sources is
Even when the distance is smaller or the distance z is smaller than the wavelength of the radio wave, the separation of the image of the radio source cannot be performed if the interval l between the radio sources is smaller than the distance z.

Further, when the intensity of the radio wave generated from the radio wave source fluctuates while scanning the radio wave intensity meter, there is a disadvantage that the obtained radio wave image is distorted.

[0006]

According to the first aspect of the present invention, a fixed antenna is provided near an observation surface, and the observation surface is moved by combining a vertically polarized wave receiving antenna and a horizontally polarized wave receiving antenna. Then, respective output ratios of the vertically polarized wave receiving antenna and the horizontally polarized wave receiving antenna to the fixed antenna are obtained. Reconstruction of a passive hologram image is performed by performing convolution integration of these ratios with the spatial propagation function at each reception point. Thus, a radio source image, that is, a radio source distribution is obtained from the observation image.

According to the second aspect of the present invention, the observation surface is scanned with the vertically polarized wave receiving antenna and the horizontally polarized wave receiving antenna as a set, and the arc tangent of the ratio of the output amplitude at each measurement receiving position of both antennas is obtained. The Laplacian of the synthesized radio wave incident angle, that is, the second-order spatial differentiation, is performed, and the radio wave source distribution is obtained by using this as an image.

Further, according to the first or second aspect of the present invention, the phase angle of each output of the vertical polarization receiving antenna and the horizontal polarization receiving antenna at each measurement point is calculated, and the situation distribution of the phase angle difference is obtained. The distribution of the ratio of the direct wave and the reflected wave is determined. Further, according to the first or second aspect of the present invention, two passive hologram images are formed by changing the frequency, and the phase difference at the same point (position) of the two images is obtained for the vertical polarization component and the horizontal polarization component. Thus, the delay time of the reflected wave with respect to the direct wave is obtained.

[0009]

FIG. 1 shows an embodiment of the present invention. A fixed antenna 21 is provided near the observation surface 13. A pair of a horizontally polarized wave receiving antenna 22 and a vertically polarized wave receiving antenna 23 is provided so that each point on the observation surface 13 can be moved and scanned. That is, the antennas 22 and 23 are mobile antennas, and the observation surface 1 is
3 is scanned, and the reception electric field strength at each point is measured. The reception outputs of these antennas 21, 22, 23 are respectively passed through band-pass filters 24, 25, 26 to extract only the desired band, and further amplifiers 27, 2 respectively.
The amplified output is converted by a signal from a local oscillator 30 in mixers 31, 32, and 33, respectively.
The filtered outputs are passed through discrete Fourier transformers 37, 38, and 39, respectively, and are subjected to discrete Fourier transforms. The resulting Fourier transforms S _R , S _H , and S _V
Are supplied to the control calculation display section 41, respectively.

The control calculation display section 41 includes a mobile antenna 22,
23 are simultaneously moved and each point of the observation surface 13 is sequentially moved to scan the observation surface 13, and signals obtained at each point, that is, the observation surface 13
Of the discrete Fourier transform S _R (x, y), S _H (x, y), and S _V (x, y) at the coordinate position (x, y) of the fixed antenna output S _R (x, y) ), The output Fourier transform S of the horizontally polarized receiving antenna 22
_H (x, y) of the ratio h _H (x, y) and the output Fourier transform S _V (x, y) of the vertically polarized receive antenna 23 of the ratio h
Calculate _V (x, y).

H _V (x, y) = S _V (x, y) / S _R (x, y) h _H (x, y) = S _H (x, y) / S _R (x, y) (1) The state of the reception output ratio on the measurement surface 13 represents a passive hologram, that is, a spatial phase distribution with respect to the output of the fixed antenna, in other words, a correlation spectrum in which the output of the fixed antenna and the output of the moving antenna interfere with each other.

The difference θ _HV (x, y) between the phase angle of the ratio h _H (x, y) and the phase angle of h _V (x, y) with respect to the fixed antenna output at each point is determined at each measurement point (x ,
y) is calculated. θ _HV (x, y) = ∠h _H (x, y) −∠h _V (x, y) (2) The phase angle difference θ _HV (x, y) is a direct wave and a reflection on the observation surface 13. It will show the distribution of the proportion of the presence of waves. That is, it is possible to know the presence or absence of the reflected wave, and it is possible to know which part has a large amount of the reflected wave.

Further, by calculating an arc tangent of a ratio of the amplitude of the output of the mobile antenna to the output of the fixed antenna at each point (x, y), the incident angle θ of the synthesized radio wave is obtained.
Get the state of _{H / V} (x, y). θ _{H / V} (x, y) = tan ⁻¹ ({ _{h H} (x, y)} / {h _V (x, y)}) (3) Also, the intensity M of the output ratio with respect to the fixed antenna at each point.
(X, y) is obtained.

M (x, y) = {({ _{h H} (x, y)} ² + {h _V (x, y)} ² ) (4) Thus, the radio field intensity at each point (x, y) Understand
The radio wave intensity distribution on the observation surface 13 can be known.
Further, the incident angle θ of the synthesized radio wave at each point to obtain the radio wave source image
Laplacian of _{H / V} (x, y), that is, spatial second derivative Δ
Find θ _{H / V} (x, y). In this case, each Laplacian value is weighted by the radio wave intensity distribution obtained by the equation (4),
Θ with respect to the radio source image where the received electric field strength is small
It is desirable to reduce the influence of noise by reducing the Laplacian value of _{H / V} (x, y).

Further, when the radio wave source interval l is larger than the radio wave wavelength λ, or when the distance z between the radio wave source and the observation surface is the radio wave wavelength λ
If it is larger, a radio interference image is formed, so that the ratio h _V (x, y) of the ratio of the output of the mobile antenna to the output of the fixed antenna is obtained.
And hologram reproduction operation is performed on h _H (x, y) to obtain I _V (x, y) and I _H (x, y). I (X ′, Y ′) = {[h (x, y) × {exp (−j2πR / λ)} / R] dxdy R = {z ² + (xx ′) ² + (yy) ') ² Ｉ The I of the result of performing the hologram reconstruction operation
_v (x, y) and I _H (x, y) are expressed by equations (2), (3),
The phase angle difference, the combined incident angle, the intensity, and the like are obtained by using instead of h _V (x, y) and h _H (x, y) in the equation (4).

In the above description, the measured h _V (x,
y), h _H (x, y) and calculated Δθ _{H / V} (x, y)
If the data contains a lot of noise, a two-dimensional spatial low-pass filter may be applied to each of them by arithmetic processing. That is, the two-dimensional spatial low-pass filter operation on f (x, y) is expressed by the following equation. F (x, y) = {f} (x, y) × sin (λ ⁻¹ × R) λ ⁻¹ · R｝ d _x , d _y R = (√ ｛(xx ′) ² + (y −y ′) ² ｝) × 2π λ is the value obtained by dividing the speed of light by the spatial cut-off frequency. Here, the value at each point of Δθ _{H / V} (x, y) is obtained. Radio source image is z>
In terms of what can be obtained with l, the direction and intensity of a radio wave incident on one point on the observation surface are vector sums of radio waves radiated from a plurality of radio sources. Therefore, as the distance z between the observation surface and the radio wave source increases with respect to the distance l between the radio wave sources, the wave front of the synthesized radio wave changes more smoothly, and the separation of the radio wave sources becomes more difficult. However, at the position where the direction of the radio wave source is perpendicular to the observation surface, that is, at the position where the perpendicular is lowered from the radio wave source to the observation surface, the incident angle of the synthesized radio wave is inflected regardless of the distance z between them, That is, the viewing direction of the angle is reversed. Therefore, the peak of the second derivative Δθ _{H / V} (x, y) in the direction of movement of the antenna at the angle of incidence of the synthesized radio wave gives the position of the radio wave source viewed perpendicularly from the observation surface.

This relationship is shown in FIGS. 2 and 3 where the combined amplitude of the output of the receiving antenna when the distance between the radio sources is 3.3 meters and the moving antennas 22 and 23 are moved along the observation plane 10 by 10 meters. The curve 42 shows the incident angle of the synthesized radio wave as a curve 43 and the Laplacian thereof as a curve 44. 2A shows a case where the distance z between the radio wave source and the observation surface is 1 meter, FIG. 2B shows a case where z is 3 meters, FIG. 3A shows a case where z is 6 meters, and FIG. 3B shows a case where z is 12 meters. From these curves, if z is smaller than the radio source interval l, as shown in FIG. 2A, the intensity distribution 42, the incident angle distribution 43, and the Laplacian distribution 44 also have large peaks at the radio source position, and the radio source image can be easily obtained. You can ask. However, as shown in FIG. 2B, it is difficult to obtain a radio source image based on the intensity distribution 42 when z and l are substantially close to each other, but the incident angle distribution 43 and its Laplacian distribution 44
Can still obtain enough radio source images. As shown in FIG. 3A, when z is about twice as large as the radio source interval, it is difficult to know the image by the distribution 43 of the incident angle, but in the Laplacian distribution 44, the radio source can be known by a clear peak. . Further, as shown in FIG. 3B, the peak value of the Laplacian distribution 44 of the incident angle becomes small even if the distance z becomes considerably large with respect to the radio source interval, but the peak is clearly detected and the position of the radio source is known. be able to.

As described above, even if a hologram is reconstructed and its intensity distribution or Laplacian distribution of the incident angle is obtained, it is difficult to separate whether the hologram is obtained by a direct wave or a reflected wave. It is. In order to know whether the radio wave source is obtained by a direct wave or a reflected wave, if the distribution state of the phase angle difference obtained by the equation (2) is obtained, it can be distinguished by this.

The oscillation frequency f of the oscillator 30₀Change it
For each, a passive hologram image, that is, h in equation (1)_V
(X, y), h_HThe distribution state of (x, y) is
By calculating the phase difference of the raw image,
It is possible to determine the delay time. That is, the frequency f₁To
I obtained from_Vf₁(X, y) and frequency f_TwoAsked by
I_Vf_TwoThe phase difference from (x, y) is obtained, and I
_Hf₁(X, y) and I _Hf_TwoFind the phase difference of (x, y)
You. By doing so, the horizontal polarization component
The way of reflection is different from that of vertical polarization component.
The delay of the reflected wave with respect to the wave can be known.

In the above, the discrete Fourier transformer 3
A fast Fourier transformer may be used instead of 7, 38, and 39. Further, as the moving antennas, three antennas for detecting three-directional components instead of the two-directional components of the vertical polarization component and the horizontal polarization component may be used. In addition, in order to obtain one radio source image, the measurement can be performed twice while changing the angle of the observation surface with respect to the radio source to obtain a radio image three-dimensionally. The outputs of the mobile antennas 22 and 23 may be switched and supplied to one spectrum analyzer.

According to the second aspect of the present invention, the fixed antenna 21 is omitted, and the Fourier transforms S _V (x, y) and S _H (x, y) of the outputs of the mobile antennas 22 and 23 are expressed by the following equations (2), respectively. H _V (x,
y), h _H (x, y) are used in place of the above to perform the above. Next, the measurement data is shown. When the measurement frequency is 200 MHz and the observation area is 20 cm × 18 cm at a radio source interval 1 = 10 cm, the situation of the intensity distribution obtained by Expression (4) and the Laplacian of the incident angle is z
Is changed to 5, 10, 15, 20, 25, 30, and 35 cm, respectively, and the distribution of the size values is shown in FIG. 4 corresponding to the observation plane. In this case as well, the two radio sources that could not be separated from the combined amplitude can be clearly separated into two hatched areas by the Laplacian of the incident angle. In particular, even when z is larger than 1, there are two hatched areas. You can see what you can do. In addition, in both the Laplacian of the synthetic amplitude and the Laplacian of the incident angle, the pattern moves to the left as the distance z increases, which is considered to be due to a balance shift between the observation plane and the radio wave plane. It can also be seen that reflected wave images from the floor and ceiling can be confirmed in the incident angle Laplacian image.

[0022]

As described above, according to the present invention, even if the radio wave source interval 1 is larger than the radio wave wavelength λ and the distance z of the observation surface is larger than the radio wave wavelength λ or if they are smaller than the wavelength, In any case where the distance z between observation surfaces is larger than the radio source interval 1, a radio wave image can be obtained by obtaining the Laplacian of the incident angle. Further, the direct wave and the reflected wave can be distinguished by obtaining the distribution of the difference in the output phase angle between each vertically polarized wave receiving antenna and the horizontally polarized wave receiving antenna. Further, even if the output of the radio wave source fluctuates, the output of the mobile antenna is normalized by the output of the fixed antenna according to the first aspect of the present invention, so that the radio wave image is not affected and there is no possibility of distortion.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an intensity distribution, an incident angle distribution, and its Laplacian distribution.

FIG. 3 is a diagram showing an intensity distribution, an incident angle distribution, and its Laplacian distribution.

FIG. 4 is a diagram showing a two-dimensional image of intensity and a two-dimensional image of Laplacian at various distances from a radio wave source to an observation surface.

FIG. 5 is a diagram showing a conventional radio wave image observation device.

Claims (4)

(57) [Claims] 1. A fixed antenna placed near an observation plane, a vertically polarized reception antenna and a horizontally polarized reception antenna movable on the observation plane, and an output of the vertically polarized reception antenna with respect to an output of the fixed antenna. A radio source visualization apparatus comprising: means for obtaining a ratio and an output ratio of the horizontal polarized wave receiving antenna; and means for performing a reproduction operation of a passive hologram image with respect to both of these ratios. 2. A vertically polarized wave receiving antenna and a horizontally polarized wave receiving antenna movably provided on an observation plane, and an arc tangent of an amplitude ratio of an output from both antennas at the same position in the observation plane. A radio wave source visualization device comprising: means for calculating an incident angle of a synthetic radio wave by calculating; and means for calculating a Laplacian of the incident angle to obtain a Laplacian image on the observation surface. 3. A means for calculating the distribution of the phase angle of the output of the vertical polarization receiving antenna and the phase angle of the output of the horizontal polarization receiving antenna at the same point on the observation plane. The radio wave source visualizing device according to claim 1 or 2. 4. The apparatus according to claim 1, further comprising means for forming two complex passive hologram reconstructed images at different frequencies, obtaining a phase difference between the two images, and obtaining the phase difference image. Radio source visualization device.