JP2002076739A - Manufacturing method for electromagnetic wave radar antenna and electromagnetic wave radar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighter and inexpensive electromagnetic wave radar antenna capable of conducting accurate measurement, by tuning the frequency of electromagnetic waves radiated from the antenna to the target frequency and reducing spurious radiation components. SOLUTION: An electromagnetic wave radar antenna AT is equipped with an antenna substrate 1 that has a transmission antenna element 11, which radiates electromagnetic waves receiving pulses outputted from a transmission unit, and a hollow square-shaped shield case 2 that covers the surface of a part of the substrate 1. The dimension of the antenna substrate 1 and the shield case 2 is made to meet the predetermined relation so that electromagnetic waves of a desired frequency are radiated from the transmission antenna element 11, according to the wavelength of the target frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electromagnetic wave radar antenna and an electromagnetic wave radar antenna, and more particularly, to a method suitable for an electromagnetic wave exploration machine for nondestructively exploring underground objects and the like.

[0002]

2. Description of the Related Art Electromagnetic wave probes have been developed that radiate electromagnetic waves from antennas and receive and analyze reflected waves from objects to conduct exploration, and have conducted exploration of land mines, buried objects, and internal exploration of pillars in buildings. It is used for such purposes.
Such an electromagnetic wave probe determines the distance to an object based on the time required from the emission of the electromagnetic wave to the reception of the reflected wave, and determines the physical properties of the object based on the speed of the electromagnetic wave passing through the object. Non-destructive measurement of the object to be searched.

[0003]

However, when a conventional electromagnetic wave exploration device observes an electromagnetic wave radiated from a transmitting antenna with a spectrum analyzer, as shown in a frequency spectrum diagram of FIG. Met. That is, even if the products have the same specifications, the frequency components output due to the very small component constants of the transmission circuit, errors in the antenna shape, or wiring layout will fluctuate, and as a result, disordered broadband electromagnetic waves will be transmitted from the transmission antenna. It radiated, and the frequency and output level of the radiated electromagnetic wave varied for each product.

Therefore, when an electromagnetic wave radiated from a transmitting antenna is captured by a receiving antenna and amplified by a receiving section (not shown) having a predetermined frequency bandwidth, as shown in FIG. The frequency component of the predetermined band was superimposed and displayed a very distorted waveform. As described above, since the frequency radiated from the transmitting antenna and the radiation level vary from one probe to another and cannot be narrowed down to a specific frequency, the optimum receiving frequency (center frequency) and the receiving bandwidth must be set for each device one by one. It takes time and effort, and the receiving frequency (center frequency) fo between the spacecrafts
In some cases, variations as high as 100 MHz may occur.

When a reflected wave reflected by an object is demodulated as shown in FIG. 12, unnecessary frequency components are superimposed on the entire received wave to cause distortion, as in the received waveform shown in FIG. (S / N ratio) was extremely deteriorated. Therefore, for example, the base point (start point) of the received waveform is set to the first peak point P
When the calibration is performed by using the method described above, the peak point becomes unclear due to the distortion, and accurate calibration is difficult. In addition, the reflected wave component RT was buried in the noise component due to the deterioration of the S / N ratio, and the base point and the period became unclear, and the reliability of the measurement result was poor.

Further, in accordance with the regulations of the Radio Law, unnecessary radiation components other than the target frequency among the radiated electromagnetic wave components must be reduced to a specified value or less, and the surroundings other than the radiation opening of the antenna are covered with a thick shield case. Or a measure to cover the housing. For example, a standard product (measuring depth 1.
5m), to prioritize suppression of unnecessary radiation,
It weighs as much as 0 kg or more, which makes it difficult to apply to equipment intended for portability and portability, and also increases the cost.

The present invention, proposed in view of such circumstances, adjusts the frequency of an electromagnetic wave radiated from an antenna to a target frequency and reduces unnecessary radiation components, thereby facilitating accurate measurement. It is an object of the present invention to provide a lightweight and inexpensive electromagnetic wave radar antenna, and to provide a method of manufacturing this electromagnetic wave radar antenna.

[0008]

According to the present invention, there is provided an electromagnetic wave radar antenna comprising a transmitting antenna element for receiving an impulse output from a transmitting unit and radiating an electromagnetic wave to a shield case. It is a manufacturing method of. That is, a step of setting the dimensions of the transmission antenna element and the shield case in association with the wavelength of the target frequency so that the frequency of the electromagnetic wave radiated from the transmission antenna element matches the target frequency, and Forming the transmitting antenna element and the shield case with the specified dimensions.

Here, the target frequency in the present invention is a frequency determined in advance when designing an electromagnetic wave radar antenna, and a dimensional relationship of the present invention is proposed to radiate the target frequency. Therefore, the frequency is naturally different from the frequency determined by the adjustment on the receiving side as in the conventional antenna.

In the electromagnetic wave radar antenna according to the present invention, an electromagnetic wave of a target frequency in a band of approximately 300 MHz to 3 GHz is intermittently radiated by feeding an impulse to a transmitting antenna element. In analyzing the radiated frequency component in such an ultra-high frequency band, it cannot be discussed by the transmission antenna element alone, and a shield case arranged around the transmission antenna element is included,
It is necessary to equivalently analyze an integrated structure including a feeder line as a distributed constant circuit. However, the inductance component and the capacitance component of such a distributed constant circuit fluctuate due to slight differences in the shape and material of the antenna element, the shield case, and the like. In addition, the stray capacity due to a feed line or the like increases, and thus the fluctuating factors increase. . Also, it is difficult to analyze an equivalent distributed constant circuit because the electromagnetic wave itself is a transient phenomenon excited by an impulse instead of a repetitive signal.

Therefore, the present inventors made the frequency component of the electromagnetic wave radiated from the transmitting antenna coincide with the target frequency,
In addition, various studies have been made on the shape of the antenna element and the shape of the shield case in order to minimize unintended frequency components. As a result, it has been found that unnecessary radiation is reduced while increasing the output level of the target frequency by giving a predetermined relationship to the shape and dimensions of the transmitting antenna element and the shield case. In other words, a distributed constant circuit having an integral structure capable of amplifying the electromagnetic wave component of the target frequency and attenuating the electromagnetic wave component of the frequency other than the target was successfully formed by giving a predetermined relationship to the dimensions and shape. When applying an impulse to the transmitting antenna, a stable high output can be obtained by applying a DC bias to the transmitting antenna element in advance, but the impulse is applied without applying a bias. It is also possible.

According to the electromagnetic wave radar antenna of the present invention,
Since the unnecessary radiation component is extremely low, measures for the unnecessary radiation for complying with the regulations of the Radio Law are minor. That is, it is not necessary to take a large measure against unnecessary radiation such as increasing the thickness of the shield case or covering the outside of the shield case with a thicker housing. As a result, the cost can be reduced, and the weight of the antenna unit is reduced by a factor of 1/1 compared with the conventional case.
It can be reduced to about 0 and can be suitably used for an exploration machine that requires portability and portability.

Further, since the unnecessary radiation component is small, the signal-to-noise ratio (S / N ratio) of the received signal is improved. As a result, it is not necessary to use a high-gain logarithmic amplifier or the like to separate and extract a signal component close to the noise level. Become simple and stable.

Furthermore, since the S / N ratio of the received signal is high and the distortion of the received signal is reduced, the calibration of the reception base point using the initial peak point of the reception waveform can be performed accurately. Further, since the S / N ratio of the received signal is high and the small signal is not lost by being buried in the noise component, the frequency (period) change according to the time lapse of the entire received wave including the reflected wave can be easily processed and output. In addition, it is possible to accurately determine the physical properties of an object through which an electromagnetic wave passes. As a result, accurate measurement can be performed regardless of the user, and it is possible to detect objects and formations that could not be performed conventionally, such as discrimination of water leakage, etc., expanding the purpose of use regardless of industrial or consumer use Is done. In brief, the principle of the physical property determination is that the relative permittivity of an object through which an electromagnetic wave passes is proportional to the square of (velocity of light / speed of electromagnetic wave propagation). Thus, the velocity (period of the electromagnetic wave) of the electromagnetic wave passing through the object is calculated from the received wave, and the relative permittivity of the passing object is obtained, whereby the physical properties are determined and the object is specified based on the obtained relative permittivity. It becomes possible.

According to the electromagnetic wave radar antenna of the present invention,
The electromagnetic wave component of the target frequency among the impulse components fed to the transmission antenna element is enhanced, and the electromagnetic wave component of the frequency other than the target is attenuated. In this case, due to the resonance of the distributed constant circuit corresponding to the transmitting antenna element and the shield case, the output level of a subharmonic component or a harmonic component such as 1/2 or 2 times the target frequency other than the target frequency increases. I do. Therefore, a configuration may be adopted in which the signal processing is performed by setting the frequency bandwidth so that the receiving unit selectively receives only one of these frequency components.

It is desirable to use a conductive material for the transmitting antenna element, the ground conductor, and the shield case, that is, a material intended to guide a current with little power loss.
Such conductive materials have conductivity, mechanical strength, workability,
Copper, aluminum, an aluminum alloy or the like is preferable in consideration of economy and the like. Also, a conductor formed by applying a conductive paint or the like to the surface of a non-conductive material can be used for the shield case or the transmitting antenna element. The transmission antenna element preferably has a structure in which a conductor foil is provided on a substrate such as a phenol resin or an epoxy resin.For example, a transmission antenna element made of a copper plate or the like is provided with an insulator near the opening side of the shield case. It is possible to adopt various aspects such as a structure that is used to support the space.

An electromagnetic wave radar antenna according to the present invention has an antenna substrate having a transmission antenna element for receiving an impulse output from a transmission unit and radiating an electromagnetic wave, and a hollow covering a surface of the substrate on which the transmission antenna element is provided. It is reasonable to adopt a configuration including a rectangular shield case.

The transmitting antenna element is formed on an antenna substrate with a pair of isosceles triangular conductive foils facing each other in a bow tie shape, and the substrate is a ground conductor made of conductive foil having a predetermined width so as to surround the transmitting antenna element. The foils can be formed in a rectangular loop shape so as to be symmetrical in the front-rear and left-right directions. In addition, the length of the base or side of the isosceles triangle of the transmitting antenna element can be set to approximately 波長 wavelength of the target frequency. Here, the isosceles triangle includes an equilateral triangle, and particularly preferably, the transmitting antenna element is formed of a pair of equilateral triangular conductive foils, and the side length of the equilateral triangle is set to be approximately 波長 wavelength of the target frequency. It is good to set. on the other hand,
An isosceles triangle (a regular triangle) facing the transmitting antenna element
The dimensions of the shield case in a direction orthogonal to the direction in which the elements are arranged are set to be approximately the same length as the wavelength of the target frequency, and the depth dimension of the shield case is set to a length that is an integral multiple of approximately 波長 wavelength of the target frequency. It is set to.

Among these dimensional relationships, the depth dimension of the shield case is set to １ ／ wavelength, ／ wavelength,
It has been found that, when the wavelength is changed like ／ wavelength, 1 wavelength,..., The output level of the target frequency has a peak near a specific depth dimension. This is because the stored energy (resonant energy) by the distributed constant circuit having the integrated structure of the shape of the transmitting antenna element, the shape of the shield case, and the shape of the ground conductor with respect to the wavelength of the target frequency at a predetermined depth dimension Is considered to be the largest for Thereby, the optimum radiation level can be obtained by appropriately changing the depth dimension.

The present inventors have prototyped a plurality of transmitting antennas having the same target frequency in accordance with the above dimensional relationship.
It was also found that there was almost no difference between the target frequencies of the electromagnetic waves radiated from the respective antennas, and the reproducibility was excellent, irrespective of the variation in the layout of the wiring such as the feed line. This eliminates variations in the target frequency for each device,
The trouble of adjusting the receiving unit for each device is not required, and the circuit configuration is simplified and stable, and the manufacturing becomes easy.

The frequency of the electromagnetic wave radiated from the transmitting antenna of the present invention ranges from approximately 300 MHz to 3
It is a specific frequency (target frequency) between GHz and belongs to the microwave band. Therefore, for example, when aluminum or the like is used as the shield case, the thickness of the material affects the distribution constant. The inductance component when the electromagnetic wave is distributed in the shield case increases as the material thickness decreases and decreases as the material thickness increases. For this reason, it is desirable that the antenna shape of the present invention be dimensionally corrected according to the thickness of the shield case or the thickness of the conductor foil of the transmitting antenna element. In other words, when a shield case having a small material thickness is used, it is possible to easily adjust to a target frequency by increasing the correction value as compared with a case using a thick shield case.

In the present invention, it is desirable to provide a suppression resistor for suppressing parasitic radiation of electromagnetic wave components other than the target frequency between the transmitting antenna element of the antenna substrate and the ground conductor. By appropriately setting the value of the suppression resistor, it is possible to effectively reduce the output level of the frequency band other than the target while suppressing the decrease in the output level of the target frequency. This allows
The S / N ratio in the received wave is further improved.

In the present invention, an electromagnetic wave absorbing material is disposed inside the shield case so as to absorb and attenuate an electromagnetic wave component having a specific polarization plane among electromagnetic wave components excited inside the shield case including the transmitting antenna element. It can be. The present inventors have found that, out of electromagnetic waves radiated from the transmitting antenna element, an electric field component (polarization plane) in a direction in which the opposed isosceles triangle (regular triangle) element is arranged.
It has been found that an electromagnetic wave having a relatively large number of unintended frequency components. Therefore, by attenuating the electromagnetic wave component having the polarization plane with the electromagnetic wave absorbing material, the radiated electromagnetic wave of the frequency component other than the intended purpose can be further reduced, and the S / N ratio of the received wave can be further improved. Can be. As the electromagnetic wave absorbing material, it is possible to use a general-purpose material in which a conductive radio wave reflecting material is adhered to a foam material or the like, and it is possible to effectively attenuate and absorb by utilizing the attenuation at the time of reflection.

In the electromagnetic wave radar antenna according to the present invention, the transmitting antenna element and the receiving antenna element may be formed separately, but may be formed integrally. That is, the transmitting antenna element and the receiving antenna element having the same shape as the element are formed symmetrically on the antenna substrate, including the ground conductor, and the shield case is used for electromagnetic coupling between the transmitting antenna element and the receiving antenna element. And a structure having a shield partition for shielding the air. According to this integrated electromagnetic wave radar antenna, electromagnetic shielding between the transmitting antenna and the receiving antenna is reduced by the shield partition provided in the shield case, so that the transmitting and receiving antenna can be reduced in size and weight while maintaining the above characteristics. It can be easily manufactured and is suitable for equipment that requires carrying.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The design procedure of an electromagnetic wave radar antenna according to an embodiment of the present invention will be described below with reference to the drawings. However, the frequency (target frequency) of the electromagnetic wave to be radiated is fo and the wavelength is λo. FIG. 1 is a top view showing an antenna substrate 1 according to the electromagnetic wave radar antenna of the present invention, FIG. 2A is a top view of a shield case 2 thereof,
FIG. 2B is a sectional view taken along the line AA in FIG. 2A, and FIG. 2C is a sectional view taken along the line BB in FIG. In addition, the antenna substrate 1
Is an integrated transmission antenna T and reception antenna R having the same shape. The shape of the antenna element 10 is a regular triangle, and the side length L is set to １ ／ of the wavelength λo of the target frequency fo. L = λo
/ 2 Let F be the width of the ground conductor 13 provided around the transmitting antenna T and the receiving antenna R. However, the width F is L /
Set to a value smaller than 2. The width 2W of the antenna substrate 1 is set to twice the wavelength λo. 2W = 2λo On the other hand, the vertical length of the antenna substrate 1 is set to H, and the vertical length H is set to be longer than the total length of the opposing antenna elements 10 and 10 plus twice the width F of the ground conductor 13. H> 2 (√3) + 2F The depth D of the shield case 2 is set to an integral multiple of １ ／ of the wavelength λo. D = (λo / 4) × n + α where n = 1, 2,
3, 4... Α: correction coefficient The correction coefficient α is a value determined according to the thickness t of the shield case 2 and the thickness of the copper foil of the antenna element 10 and the ground conductor 13, and in particular, the thickness of the shield case 2. Is a coefficient that depends on In the present embodiment, when the thickness t of the shield case 2 using aluminum is 1.2 mm, the correction coefficient α is set to 1 mm. The width and length of the shield case 2 are the same as those of the antenna substrate 1.

As described above, the side length L of the antenna element 10
The width F of the ground conductor 13, the horizontal length 2W, the vertical length H, and the depth D of the antenna substrate 1 are set in relation to the wavelength λo. In each of the transmitting antenna T and the receiving antenna R, the antenna element 10 and the ground conductor 13 are connected to the antenna substrate 1.
It is configured to be symmetrically arranged on the upper and lower sides.

[0027]

In the above description, the procedure for designing the dimensions of the main parts of the antenna substrate 1 and the shield case 2 has been described.
Hereinafter, an embodiment of the electromagnetic wave radar antenna of the present invention made in accordance with this design procedure will be described in more detail with reference to the drawings.

As shown in FIG. 1, the antenna substrate 1 has a rectangular shape having a length H and a width 2W (= 2λo), and a transmitting antenna T and a receiving antenna R having the same shape are integrally symmetrical on the same substrate. It is the structure arranged in. Therefore, in describing the antenna substrate 1, the transmitting antenna T which is half the size will be described. The antenna substrate 1 is formed by etching away unnecessary portions of the copper foil on the surface of the substrate 12 made of glass epoxy resin except for the transmitting antenna element 11 and the ground conductor 13 by etching.

The transmitting antenna T has a vertical length H and a horizontal width W (= λ
The transmitting antenna element 11 is formed in the center of the substrate 12 of (o) with the antenna elements 10 and 10 made of equilateral triangular copper foil having one side length L and the tops 10a and 10a facing each other in a bow tie shape. . A ground conductor (copper foil) 13 having a width F is provided in a square loop shape along the side edge of the substrate 12 so as to surround the transmission antenna element 11, and has a symmetric shape in the front-rear and left-right directions. The tops 10a, 10a of the antenna elements 10, 10
a is provided with a slight gap therebetween, and a power supply line described later is soldered to the tops 10a.

The length L of one side of the antenna element 10 is
2, which is half the width W of the antenna element 2, that is, half the wavelength λo, and suppresses parasitic vibration between the tops 10b, 10b and the tops 10c, 10c of the antenna element 10 and the ground conductor 13. Resistance 14 is soldered. The width F of the ground conductor 12 is not particularly limited as long as the symmetry of the arrangement on the substrate 12 is maintained. However, in consideration of the conductivity when the ground conductor 12 is mounted on the shield case described later, the width F is larger than the width of the bent bent surface of the shield case. To make it wider.
The vertical length H of the transmitting antenna T is not particularly limited,
The length is set to be longer than the sum of the total length of the transmitting antenna element 11 in the vertical direction and twice the width F of the ground conductor 13. still,
An opening 15 provided on the ground conductor 13 is a screw insertion port for attaching and fixing the antenna substrate 1 to the shield case 2 as described later.

As shown in FIG. 2, the shield case 2 is made of aluminum having a thickness t of 1.2 mm, and is formed in a rectangular box shape having a height H, a width 2W (= 2λo) and a depth D. The opening is provided with a bent portion 20 having a width F ′ over the entire periphery of the opening side edge. The ground conductor 13 of the antenna substrate 1 is attached and fixed to the bent portion 20 in a conductive contact state. The width F ′ of the bent portion 20 is set to be smaller than the width F of the ground conductor 13. I have.

The depth D is an integral multiple of λo / 4 with respect to the wavelength λo of the target frequency fo, that is, λo / 4, 2λo /
4, 3λo / 4, λo..., And the dimension of the depth D can be set to any length so that the output level of the target frequency fo is maximized. it can. A shield plate (shield partition) 21 made of aluminum for reducing electromagnetic coupling between the transmitting antenna T and the receiving antenna R is provided in the center of the shield case 2 over the entire length in the vertical direction. The shield case 21 allows the shield case 2 to be
1 and the receiving side R1. In this embodiment, a shield plate 21 having a thickness t1 of 2 mm is used. The screw holes 22 are for inserting screws for fixing the antenna substrate 1.

FIG. 3A shows an electromagnetic wave radar antenna A.
T, that is, a top view showing a state in which the antenna substrate 1 is attached to the shield case 2, FIG. 2B is a sectional view taken along the line AA in FIG. 2A, and FIG. FIG. 4 shows a cross-sectional view taken along arrow -B. The screw hole 22 of the shield case 2 is formed by using the three screws 23 so that the surface on which the transmitting antenna element 11 and the ground conductor 13 are provided faces downward.
Attach and fix to. As a result, the ground conductor 13 of the antenna substrate 1 is fixed in conductive contact with the bent portion 20 and the shield plate 21. When mounted in this manner, the transmitting antenna T of the antenna substrate 1 is positioned so as to cover the opening of the transmitting side T1 of the shield case 2, and the receiving antenna R of the antenna substrate 1 is connected to the receiving side R of the shield case 2.
1 so as to cover the opening. That is, in the antenna AT, the electromagnetic wave excited by the antenna substrate 1 including the shield case 2 is transmitted through the antenna substrate 1 itself and radiated forward.

In this embodiment, before the antenna substrate 1 is fixed to the shield case 2, the transmission / reception unit, the electromagnetic wave absorbing material, the feed line, and the like are incorporated at the same time. Hereinafter, a procedure for assembling these members will be described with reference to an exploded perspective view of FIG.

As shown in FIG. 4, the shield case 2 accommodates the transmission unit 40 and the reception unit 50 and the electromagnetic wave absorbers 30 and 30 on the transmission side T1 and the reception side R1 shielded by the shield plate 21, respectively. The substrate 1 is attached and fixed so as to cover.

The transmitting antenna T and the receiving antenna R of the antenna substrate 1 have the tops 10a, 1
The power supply line 16 and the power supply line 17 are connected to 0a.
That is, a coaxial cable is used for the feed line 16, and the core wire is soldered to the top 10 a of the one antenna element 10 and the shield wire is soldered to the top 10 a of the antenna element 10 facing the antenna 10. The other end of the feed line 16 is provided with a high frequency pin connector 16a. By connecting the pin connector 16a to the connector 40a on the transmitting unit 40 side, the DC bias and the impulse are transmitted from the transmitting unit 40 to the transmitting antenna element 11. Supply power. The transmitting unit 40 is provided with a connector 40b, and receives power and a control signal from a signal processing unit (not shown) provided separately by connecting the connector 41.

Similarly, a coaxial cable is also used for the feed line 17, and the core wire is soldered to the top 10 a of the one antenna element 10 and the shield wire is soldered to the top 10 a of the antenna element 10 facing the antenna 10. I have. A high frequency pin connector 17a is also provided at the other end of the power supply line 17, and by connecting this pin connector 17a to the connector 50a on the receiving unit 50 side, a received signal captured by the receiving antenna R can be received by the receiving unit 50. To the side. The receiving unit 50 is provided with a connector 50b. By connecting the connector 51, power is supplied from a signal processing unit (not shown) provided separately, and a receiving signal, a trigger signal, and the like are transmitted. The shield case 2 is provided with openings 2a and 2b, and is connected to the control unit side through wires derived from the transmission unit 40 and the reception unit 50.

As described above, the electromagnetic wave radar antenna AT of the present invention is a shield case 2 made of thin aluminum.
The antenna substrate 1 is attached to the
In addition, the antenna has a light weight structure in which only the receiving unit 50 is housed, and is extremely lightweight as compared with a conventional antenna in which measures against unnecessary radiation are prioritized. In addition, a signal coupling failure (natural wave detection failure) is eliminated by the structure having a resonating property composed of the antenna substrate 1 and the shield case 2, and
Stable transmission and reception can be performed.

FIG. 5 is a diagram showing the configuration of the power supply line 16 from the transmission unit 40.
Is a signal transmitted to the transmitting antenna element 11 via the horizontal axis, with the horizontal axis representing time and the vertical axis representing voltage level.
In the present embodiment, a DC bias is applied so that the core wire of the power supply line 16 has the voltage Vd with respect to the shield line. That is, a DC bias current is applied via the antenna element 10, the suppression resistor 14, and the ground conductor 13 facing each other. In this state, the impulse S
Is applied between the antenna elements 10 at predetermined intervals To, so that the antenna substrate 1 including the shield case 2 is
Radiates electromagnetic waves. By applying the DC bias, the transmitting unit 40 can apply an impulse to the transmitting antenna element 11 by controlling and driving the DC bias voltage in the form of an impulse, thereby simplifying the circuit configuration.

FIG. 6 schematically shows a state in which a specific electromagnetic wave component radiated from the transmitting antenna T is absorbed by the electromagnetic wave absorbing member 30. The electromagnetic wave absorbing material 30 is a general-purpose material in which a conductive radio wave reflecting material is attached to a foam material. The electromagnetic wave absorbing material 30 is effectively attenuated by utilizing attenuation at the time of reflection by the reflecting material. Accordingly, it exhibits a large attenuation characteristic with respect to an electromagnetic wave having a specific polarization plane.

In this embodiment, as shown in FIG. 6A, a polarization component Eo having an electric field in the width W direction of the shield case 2 is provided.
The electromagnetic wave absorbing member 30 is not absorbed, but attenuates the polarization component E1 having an electric field in the longitudinal H direction of the shield case 2 to the polarization component E1 'shown by the solid line as shown by the broken line in FIG. I have arranged. That is, the electromagnetic wave having the polarization component E1 in the longitudinal H direction of the shield case 2 includes the target frequency fo.
Since unnecessary frequency components different from the above are included to some extent, unnecessary radiation components are absorbed and removed to further reduce unnecessary radiation.

FIG. 7 shows the result of measuring the electromagnetic wave radiated from the transmitting antenna T of the electromagnetic wave radar antenna AT of this embodiment and captured by the receiving antenna R with a frequency spectrum analyzer, and shows the result shown in FIG. In comparison, it can be seen that the component of the target frequency fo protrudes, and other unnecessary frequency components are effectively attenuated. In addition, since the frequency components radiated at a high level are discrete, by appropriately selecting the reception bandwidth on the receiving unit side, for example, a frequency of fo / 2 different from the target frequency fo, or 2fo It is also possible to receive the frequency and perform necessary measurement processing.

FIG. 8 is a waveform diagram in which the reception unit 50 receives and amplifies the reflected wave of the electromagnetic wave radiated from the electromagnetic wave radar antenna AT of this embodiment on the antenna substrate 1.
As can be seen from the figure, since unnecessary frequency components are extremely reduced, an approximately sinusoidal distortion-free attenuation waveform based on the target frequency fo is exhibited, and demodulation is performed accurately down to a very small amplitude.

FIG. 9 shows a reception waveform of an electromagnetic wave radiated from the electromagnetic wave radar antenna AT of the present embodiment and reflected by an object. Since the received signal has no unnecessary frequency components superimposed thereon as in the waveform of FIG. 8, the S / N ratio is excellent, and the base point, the end point, and the period variation of the reflected wave RT can be clearly distinguished. It is easy to determine the point (the first peak point or the second peak point) P,
It is possible to perform accurate calibration and measurement.

[0045]

According to the present invention, the frequency component of the electromagnetic wave radiated from the transmitting antenna can be made coincident with the target frequency by a simple design method, and unnecessary frequency components can be reduced. Accordingly, measures against unnecessary radiation for complying with the regulations of the Radio Law can be made light, and the antenna itself can be made extremely lightweight and low in cost, which is suitable for portable equipment. Also,
Since the S / N ratio of the received signal is improved, the circuit configuration is simple and stable, the calibration of the receiving base point can be performed accurately, and the physical properties of the object through which the electromagnetic wave passes can be determined accurately, thus enabling industrial use. It is possible to greatly expand the application of electromagnetic wave exploration regardless of whether it is for civil use.

[Brief description of the drawings]

FIG. 1 is a top view of an antenna substrate of an electromagnetic wave radar antenna according to an embodiment of the present invention.

2A is a top view of a shield case of the electromagnetic wave radar antenna according to the embodiment of the present invention, FIG. 2B is a cross-sectional view taken along line AA of FIG. 2A, and FIG. FIG.

3A is a top view showing a state in which the antenna board shown in FIG. 1 is attached to the shield case shown in FIG. 2, and FIG.
Is a cross-sectional view taken along the line AA of (a), and (c) is a BB line of (a).
It is arrow sectional drawing.

FIG. 4 puts necessary members in the shield case shown in FIG. 2,
FIG. 2 is an exploded perspective view showing an assembled state when the antenna substrate shown in FIG. 1 is attached.

FIG. 5 is an explanatory diagram illustrating a signal waveform supplied to a transmission antenna.

FIG. 6 is a schematic diagram showing a state in which unnecessary electromagnetic waves radiated from the electromagnetic wave radar antenna shown in FIG. 4 are absorbed and attenuated.

FIG. 7 is a frequency spectrum diagram obtained by observing an electromagnetic wave radiated from the electromagnetic wave radar antenna shown in FIG. 4 with a frequency spectrum analyzer.

8 is a reception waveform diagram of an electromagnetic wave radiated from the electromagnetic wave radar antenna shown in FIG.

9 is a reception waveform diagram of a reflected wave radiated from the electromagnetic wave radar antenna shown in FIG. 4 and reflected by an object.

FIG. 10 is a frequency spectrum diagram obtained by observing an electromagnetic wave radiated from a conventional electromagnetic wave probe with a frequency spectrum analyzer.

FIG. 11 is a reception waveform diagram of an electromagnetic wave radiated from a conventional electromagnetic wave probe.

FIG. 12 is a reception waveform diagram of a reflected wave radiated from a conventional electromagnetic wave probe and reflected by an object.

[Explanation of symbols]

 AT Electromagnetic wave radar antenna 1 Antenna substrate 11 Transmitting antenna element 13 Ground conductor 14 Suppression resistor 2 Shield case 21 Shield partition 30 Electromagnetic wave absorber 40 Transmitting unit D Depth dimension of shield case S Impulse fo Target frequency λo Target frequency wavelength

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01Q 15/24 H01Q 15/24

Claims (8)

[Claims] 1. A method of manufacturing an electromagnetic wave radar antenna, comprising: attaching a transmission antenna element that radiates an electromagnetic wave in response to an impulse output from a transmission unit to a shield case, wherein a frequency of the electromagnetic wave radiated from the transmission antenna element is provided. Setting the dimensions of the transmitting antenna element and the shield case in relation to the wavelength of the target frequency so as to match the target frequency, and forming the transmitting antenna element and the shield case with the set dimensions. And a method for manufacturing an electromagnetic wave radar antenna. 2. An electromagnetic wave radar antenna comprising: an antenna substrate having a transmission antenna element for radiating an electromagnetic wave in response to an impulse output from a transmission unit; and a hollow shield case covering one surface of the substrate. The dimensions of the antenna substrate and the shield case are set in a predetermined relationship according to the wavelength of the target frequency so as to radiate an electromagnetic wave of a target frequency from the transmitting antenna element. Electromagnetic wave radar antenna. 3. The transmitting antenna element is formed on the antenna substrate with a pair of isosceles triangular conductive foils facing each other in a bow tie shape, and the substrate is formed of conductive foil so as to surround the transmitting antenna element. The conductors are arranged in a square loop so as to be symmetrical in the front-rear and left-right directions, and the length of the base or side of the isosceles triangle of the transmitting antenna element is set to approximately 波長 wavelength of the target frequency. The electromagnetic wave radar antenna according to claim 2, wherein: 4. The size of the shield case in a direction orthogonal to the direction in which the opposing isosceles triangular elements of the transmitting antenna element are arranged is set to be substantially the same length as the wavelength of the target frequency, and the shield case is provided. The electromagnetic wave radar antenna according to claim 2, wherein a depth dimension of the electromagnetic wave radar antenna is set to a length that is an integral multiple of substantially 波長 wavelength of the target frequency. 5. The electromagnetic wave radar antenna according to claim 4, wherein dimensions of the shield case are corrected according to an effective length of the electromagnetic wave of a target frequency distributed on the shield case and the antenna substrate. 6. The antenna according to claim 2, wherein a suppression resistor for suppressing a parasitic radiation of an electromagnetic wave component other than a target frequency is provided between the transmitting antenna element of the antenna substrate and a ground conductor. An electromagnetic wave radar antenna according to the item. 7. An electromagnetic wave absorbing material is arranged inside the shield case so as to absorb and attenuate an electromagnetic wave component having a specific polarization plane among electromagnetic wave components excited inside the shield case including the transmission antenna element. The electromagnetic wave radar antenna according to any one of claims 2 to 6, wherein: 8. A transmitting antenna element and a receiving antenna element having the same shape as the transmitting antenna element are formed on the antenna substrate in a symmetrical manner, and the shield case includes an electromagnetic wave between the transmitting antenna element and the receiving antenna element. The electromagnetic wave radar antenna according to any one of claims 2 to 7, further comprising a shield partition for shielding coupling.