WO2002016962A1

WO2002016962A1 - Electromagnetic wave radar antenna manufacturing method and electromagnetic wave radar antenna

Info

Publication number: WO2002016962A1
Application number: PCT/JP2001/003055
Authority: WO
Inventors: Masahiro Fujiwara
Original assignee: Cos Co., Ltd.
Priority date: 2000-08-23
Filing date: 2001-04-09
Publication date: 2002-02-28
Also published as: AU2001293353A1; JP2002076739A

Abstract

A lightweight, low-cost electromagnetic wave radar antenna is provided which enables a precise measurement by adjusting the frequency of an electromagnetic wave radiated from the antenna to an object frequency, while reducing unwanted radiated components. An electromagnetic wave radar antenna (AT) comprises an antenna board (1) having a transmitting antenna element (11) receptive of an impulse outputted from a transmitting unit for radiating an electromagnetic wave; and a hollow, rectangular shield case (2) overlying one surface of the antenna board (1); wherein the dimensions of the antenna board (1) and shield case (2) are so determined as to be in a predetermined relationship with each other in accordance with the wavelength of an object frequency so as to cause the electromagnetic wave of the object frequency to be radiated from the transmitting antenna element (11).

Description

Description Electromagnetic wave radar antenna manufacturing method Electromagnetic wave radar antenna

The present invention relates to a method for 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 non-shattering exploration of underground objects and the like. Background art

An electromagnetic wave probe has been developed that radiates electromagnetic waves from an antenna and receives and analyzes reflected waves from an object to perform exploration.It is used for landmine exploration, buried object exploration, or partial exploration of pillars in buildings, etc. Have been.

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. However, in a conventional electromagnetic wave probe, when an electromagnetic wave radiated from a transmitting antenna is observed by a spectrum analyzer, as shown in a frequency spectrum diagram of FIG. 10, the electromagnetic wave includes an extremely wide band frequency component. That is, even if the products have the same specifications, the output frequency components fluctuate due to the very small component constants of the transmission circuit, errors in the antenna shape, or wiring arrangements, and as a result, disordered broadband electromagnetic waves are transmitted. The frequency and output level of the radiated electromagnetic waves varied from product to product.

Therefore, when the electromagnetic wave radiated from the transmitting antenna is captured by the receiving antenna and amplified by the receiving unit (not shown) having a predetermined frequency bandwidth, as shown in FIG. 11, a predetermined attenuation waveform close to the original sine wave is obtained. A very distorted waveform with the frequency components of the band superimposed Was presenting.

As described above, the frequency radiated from the transmitting antenna and the radiation level vary for each spacecraft and it is not possible to narrow down to a specific frequency. Therefore, the optimum receiving frequency (center frequency) and receiving bandwidth must be set for each device one by one. In some cases, the receiving frequency (center frequency) f0 of the spacecrafts may fluctuate by as much as 100 MHz.

When the reflected wave reflected by the object is demodulated as shown in Fig. 12, unnecessary frequency components are superimposed on the entire received wave to give a distortion, similar to the received waveform shown in Fig. 10, and the signal-to-noise ratio ( (S / N ratio) was extremely deteriorated. For this reason, for example, when the base point (start point) of the received waveform is calibrated at the first peak point P, the peak point becomes unclear due to 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 results was poor.

In addition, due to 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 may be covered with a thick shield case. However, measures had to be taken to cover the housing. For example, the standard product of a conventional antenna alone (measurement depth 1.5 m) weighs more than 1 Okgf in order to give priority to suppression of unnecessary radiation, and is intended for portability and portability. In addition, it was difficult to apply the system to the equipment and the cost increased.

The present invention, proposed in view of such circumstances, adjusts the frequency of electromagnetic waves radiated from an antenna to a target frequency and reduces unnecessary radiation components, thereby making it possible to easily perform accurate measurement. The purpose of the present invention is to provide a lightweight, inexpensive electromagnetic radar antenna that can be manufactured, and at the same time, to provide a method of manufacturing the electromagnetic radar antenna. Disclosure of the invention

The present invention proposed to achieve the above object is a method for manufacturing an electromagnetic wave radar antenna, in which a transmitting antenna element that receives an inpulse output from a transmitting unit and radiates an electromagnetic wave is attached to a shield case. That is, a step of setting the dimensions of the transmission antenna element and the shield case in relation to the wavelength of the target frequency so that the frequency of the electromagnetic wave radiated from the transmission antenna element matches the target frequency, Forming the transmission 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 the dimensional relationship of the present invention for radiating the target frequency is proposed. Therefore, the frequency is naturally different from the frequency determined by the adjustment of the receiving side as in the conventional antenna.

In the electromagnetic wave radar antenna according to the present invention, an electromagnetic wave having a target frequency within a band of approximately 300 MHz to 3 GHz is intermittently radiated by feeding an impulse to the transmitting antenna element. When analyzing the radiated frequency component in such an ultra-high frequency band, it is impossible to discuss the transmission antenna element alone, and the integrated structure consisting of the shield case, the feeder line, etc., that includes the transmission antenna element and is distributed around the transmission antenna element is distributed. It is necessary to analyze equivalently as a constant circuit.

However, the inductance component and capacitance component of such a distributed constant circuit fluctuate due to slight differences in the shape and material of the antenna element and shield case, etc. Increase. In addition, it is difficult to analyze an equivalent distributed constant circuit because the electromagnetic wave itself is a transient phenomenon that is excited not by a repetitive signal but by an impulse.

Therefore, the present inventors have made various changes in the shape of the antenna element and the shape of the shield case to make the frequency component of the electromagnetic wave radiated from the transmitting antenna coincide with the target frequency and to reduce the frequency component outside the target as much as possible. Consideration was added. As a result, It has been found that unnecessary radiation can be reduced while increasing the output level of the target frequency by providing a predetermined relationship between the shape and dimensions of the 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.However, a configuration is adopted in which the impulse is applied without applying a bias. It is also possible to do so.

According to the electromagnetic wave radar antenna of the present invention, since unnecessary radiation components are extremely low, measures for unnecessary radiation for complying with the regulations of the Radio Law can be minor. In other words, it is not necessary to take measures against unnecessary radiation by dogs, 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 alone can be reduced to about 1Z10 as compared with the conventional one, so that the antenna can be suitably used for an exploration machine that requires portability and portability. Also, 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 signal components 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 receiving base point using the initial peak point of the received waveform can be performed accurately. Also, 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, it is easy to process changes in frequency (period) over time of the entire received wave including the reflected wave. It is possible to accurately determine the physical properties of an object through which electromagnetic waves pass.

This enables accurate measurement regardless of the user, and enables exploration of objects and formations that could not be performed conventionally, such as discrimination of water leakage, etc. The purpose of use is expanded regardless of use.

In brief, the principle of physical property discrimination is that the relative permittivity of an object through which an electromagnetic wave passes is proportional to the square of (light speed / electromagnetic wave propagation speed). By calculating the speed (period of the electromagnetic wave) of the electromagnetic wave passing through the object from the received wave and calculating the relative permittivity of the passing object, the physical properties are determined and the object is identified based on the obtained relative permittivity. Can be performed.

According to the electromagnetic wave radar antenna of the present invention, of the impulse components fed to the transmitting antenna element, the electromagnetic wave component of the target frequency is enhanced, and the electromagnetic wave component of the frequency other than the target is attenuated. In this case, the output level of subharmonic components and harmonic components, such as 1/2 or 2 times the target frequency, increases in addition to the target frequency due to the resonance characteristics of the distributed constant circuit corresponding to the transmitting antenna element and the shield case. I do.

Therefore, it is possible to adopt a configuration 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 grounding conductor, and the shield case, that is, a material for conducting current with little power loss. As such a conductive material, copper, aluminum, an aluminum alloy, or the like is preferable in consideration of conductivity, mechanical strength, workability, economy, and the like.

Further, 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 ゃ transmitting antenna element.

The transmitting antenna element preferably has a structure in which a conductor foil is provided on a substrate such as phenol resin or epoxy resin.For example, a transmitting 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 modes such as a structure for supporting the space by using a hologram.

An electromagnetic wave radar antenna according to the present invention includes: an antenna substrate having a transmission antenna element that receives an impulse output from a transmission unit and radiates an electromagnetic wave; It is reasonable to adopt a configuration that includes a hollow-shaped shield case that covers the surface on the side where the communication antenna element is provided.

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 has a rectangular ground conductive foil made of conductive foil having a predetermined width so as to surround the transmitting antenna element. They can be arranged in a loop 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 approximately 1/2 of the target frequency. It is better to set the wavelength.

On the other hand, the dimensions of the shield case in a direction perpendicular to the direction in which the opposing isosceles triangle (regular triangle) elements of the transmitting antenna element are arranged are set to be substantially the same length as the wavelength of the target frequency, and the depth of the shield case The dimensions are set to an integral multiple of approximately four wavelengths of the target frequency.

Of these dimensional relationships, if the depth of the shield case is changed to 1Z4 wavelength, 2Z4 wavelength, 3Z4 wavelength, 1 wavelength of the target frequency, the output level of the target frequency will change. It was found to have a peak near a certain depth dimension. This is because the stored energy (resonant energy) of the transmission antenna element, the shape of the shield case, and the shape of the ground conductor at a given depth dimension for the wavelength of the target frequency is determined by a distributed constant circuit composed of an integrated structure. It is considered that this is the maximum for the target frequency. Thereby, the optimum radiation level can be obtained by appropriately changing the depth dimension.

The present inventors have made a plurality of prototypes of transmission antennas having the same target frequency according to the above dimensional relationship, and have determined the purpose of electromagnetic waves radiated from each antenna regardless of variations in wiring layout such as a feed line. It was also found that there was almost no frequency difference and the reproducibility was excellent. This eliminates variations in the target frequency for each device, This eliminates the need to adjust the receiver for each device, simplifies the circuit configuration, stabilizes it, and facilitates manufacturing.

The frequency of the electromagnetic wave radiated from the transmitting antenna of the present invention is a specific frequency (target frequency) between about 300 MHz and 3 GHz as described above, 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 thickness increases. Therefore, for the antenna shape of the present invention, the dimensions calculated by the above-described design method can be used as they are, but the thickness of the shield case or the conductor of the transmitting antenna element is not larger than the calculated dimensions. It is desirable to correct according to the thickness of the foil. In other words, when using a shield case with a small material thickness, it is possible to easily adjust to the target frequency by increasing the correction value compared to using a thick shield case.

In the present invention, it is desirable to provide a suppression resistor for suppressing the 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 further improves the S / N ratio of the received wave.

In the present invention, an electromagnetic wave absorbing material is disposed inside a shield case so as to absorb and attenuate an electromagnetic wave component having a specific polarization plane among electromagnetic wave components excited inside a shield case including a transmitting antenna element. be able to.

The present inventors consider that the direction of the electric field in the electromagnetic wave radiated from the transmitting antenna element is the direction in which the opposing isosceles triangle (regular triangle) element is arranged (the direction in which the pair of conductive pins oppose). We have found that a certain electromagnetic wave component contains 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, The S / N ratio of the received wave can be further improved.

As the electromagnetic wave absorbing material, it is possible to use a general-purpose material in which a conductive electromagnetic wave reflecting material is attached 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 of the present invention, the transmitting antenna element and the receiving antenna element may be formed as separate bodies, but may also 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 grounding conductor, and the shield case is formed between the transmitting antenna element and the receiving antenna element. A configuration including a shield partition for shielding the coupling can be provided. Here, the left-right direction is a direction orthogonal to the direction in which the pair of conductive wires face each other.

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. Further, as a result of the action of the electromagnetic wave absorbing material, the direction of the electric field of the electromagnetic wave radiated from the transmitting antenna element becomes the right and left direction, that is, the direction from the transmitting antenna element to the receiving antenna element, and the received signal strength and SZN The ratio is improved. BRIEF DESCRIPTION OF THE FIGURES

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

Fig. 3 shows the antenna board shown in Fig. 1 attached to the shield case shown in Fig. 2. (A) is a top view, (b) is a cross-sectional view taken along the line AA of (a), and (c) is a cross-sectional view taken along the line BB of (a).

FIG. 4 is an exploded perspective view showing an assembled state when the constituent members are placed in the shield case shown in FIG. 2 and the antenna substrate shown in FIG. 1 is mounted.

FIG. 5 is a schematic explanatory diagram showing a waveform of a signal fed to the transmission antenna.

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

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

FIG. 8 is a waveform diagram of a received signal of an electromagnetic wave radiated from the electromagnetic wave radar antenna. FIG. 9 is a waveform diagram of a received signal of a reflected wave radiated from an electromagnetic wave radar antenna and reflected by an object.

FIG. 10 is a frequency spectrum diagram obtained by observing an electromagnetic wave radiated from a conventional electromagnetic wave exploration device 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. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a design procedure of the electromagnetic wave radar antenna according to the embodiment of the present invention will be described with reference to the drawings. In the following description, the frequency (target frequency) of the electromagnetic wave to be radiated is: f. And that wavelength is the person. And

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

2 (a) is a top view of the shield case 2, (b) is a cross-sectional view taken along the line A-A of (a), and FIG. is there. The antenna substrate 1 is formed by integrally integrating a transmitting antenna T and a receiving antenna R having the same shape. The design procedure of this embodiment has the following steps (1) to (4).

(1) The shape of the antenna element 10 is an equilateral triangle, and the side length L is the target frequency: e. Set to 1/2 of the wavelength input of ₀ .

(2) Let F be the width of the ground conductor 13 provided around the transmitting antenna および and the receiving antenna R. However, the width F is set to a value smaller than LZ2.

F <1/2

(3) Set the width 2 W of the antenna substrate 1 to twice the wavelength;

2 W = 2 Λο

On the other hand, the vertical length of the antenna substrate 1 is set to Η, and the vertical length Η 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.

Η> 2 -V "3 + 2 F

(4) Insert the wavelength D at the depth D of the shield case 2. Set to an integral multiple of 1/4 of.

D = (λο / 4) xn + where n = 1, 2, 3, 4 · · · ·

a: Correction coefficient

The correction coefficient 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 is a coefficient that depends particularly on the thickness of the shield case 2.

In the present embodiment, when the thickness t of the shield case 2 made of aluminum is 1.2 mm, the correction coefficient is set to 1 mm.

The width and length of the shield case 2 are the same as those of the antenna substrate 1.

Thus, 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 wavelengths; Set in relation to. Then, in each of the transmitting antenna T and the receiving antenna R, the antenna element 10 and the grounding conductor 13 are arranged on the antenna substrate 1 so as to be symmetrical in the front-rear direction and the left-right direction. In the above description, the design procedure of the dimensions of the main parts of the antenna substrate 1 and the shield case 2 has been described.Hereinafter, an embodiment according to the electromagnetic wave radar antenna of the present invention made according to this design procedure will be described with reference to the drawings. Further details will be described.

As shown in FIG. 1, the antenna substrate 1 has a rectangular shape with a vertical length of H and a width of 2 W (= 2λ ₀ ), and a transmitting antenna Τ and a receiving antenna R of the same shape are symmetrically integrated left and right on the same substrate. It is the structure arranged in. Therefore, in describing the antenna substrate 1, the transmitting antenna で, which is half the size, will be described. The antenna substrate 1 is formed by etching and removing 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 Τ is an antenna element 10 made of an equilateral triangular copper foil with a side length L at the center of a substrate 12 having a vertical length Η and a width W (= λο). Are opposed to each other to form a transmission antenna element 11. A ground conductor (copper foil) 13 having a width F is provided in a rectangular loop along the side edge of the substrate 12 so as to surround the transmitting antenna element 11 so as to be symmetrical in the front-rear and left-right directions. A small gap is provided between the tops 10 & and 10 a of the antenna elements 10 and 10 to insulate them, and a feeder described later is soldered to the tops 10 a and 10 a.

The length L of one side of the antenna element 10 is 1/2 of the width W of the substrate 12, that is, 1/2 of the wavelength ₀ , and the top 1 Ob, 10 b and the top 10 c of the antenna element 10 are set. , 10c are soldered with a suppression resistor 14 between the ground conductor 13 for suppressing the parasitic vibration.

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 conductivity when the ground conductor 12 is mounted on a shield case described later, the width F is larger than the width of the shield case mounting bent surface. To make it wider.

The vertical length H of the transmitting antenna T is not particularly limited, but is set to be longer than the total length of the transmitting antenna element 11 in the vertical direction plus twice the width F of the ground conductor 13. The opening 15 provided on the grounding conductor 13 is a screw insertion hole 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 with a thickness t of 1.2 mm, and is formed in a rectangular box shape with a height H, a width 2W (= 2Λο), and a depth D. 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.

Depth D is the target frequency f. Wavelength λ. Respect, an integral multiple of Z4, Sokuchi, tut ₀ 4, 2 input. / 4, 3 / 4, 4 people. / 4, · ·-ηλο / 4 (η is an integer), which is the length of the target frequency f. The dimension of the depth D can be set to any length so that the output level becomes maximum.

In the center of the shield case 2, a shield plate (shield bulkhead) made of aluminum is used to reduce electromagnetic coupling between the transmitting antenna T and the receiving antenna R over the entire length in the vertical direction. The shield plate 21 divides the shield case 2 into a transmission side T1 and a reception side R1.

In this embodiment, a shield plate 21 having a thickness t1 of 2 mm is used. The screw hole 22 is for inserting a screw for fixing the antenna substrate 1.

Fig. 3 (a) is a top view showing the electromagnetic wave radar antenna AT, that is, the antenna board 1 attached to the shield case 2, and Fig. 3 (b) is a cross-sectional view taken along the line A-A of (a). Figure (c) is a cross-sectional view taken along the line BB of (a).

The antenna substrate 1 is attached and fixed to the screw holes 22 of the shield case 2 using three screws 23 so that the surface on which the transmitting antenna element 11 and the ground conductor 13 are provided faces downward. As a result, the ground conductor 13 of the antenna substrate 1 is fixed in a state of being in conductive contact with the bent portion 20 and the shield plate 21. When mounted in this way, the transmitting antenna T of the antenna board 1 is positioned so as to cover the opening of the transmitting side Τ1 of the shield case 2, and the receiving antenna R of the antenna board 1 is connected to the receiving side R 1 of the shield case 2. It is located so as to cover the opening. That is, in the antenna A A, 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, the transmission / reception unit, the electromagnetic wave absorbing material, the power supply line, and the like are incorporated at the same time before the antenna substrate 1 is fixed to the shield case 2.

Next, a procedure for assembling these members will be described with reference to an exploded perspective view of FIG. As shown in FIG. 4, the transmission case 40 and the reception unit 50 and the electromagnetic wave absorbers 30 and 30 are provided on the transmission side T 1 and the reception side R 1 shielded by the shield plate 21 in the shield case 2. The antenna board 1 is stored and fixed so as to cover the antenna board 1. To the transmitting antenna T and the receiving antenna: R of the antenna substrate 1, feed lines 16 and 17 are connected to the tops 10a and 10a of the antenna element 10, respectively. That is, a coaxial cable is used for the feeder line 16, the core wire is soldered to the top 10a of one antenna element 10 and the top 10a of the antenna element 10 to which the shield wire faces. Soldered to a. The other end of the feeder line 16 is provided with a high-frequency bin connector 16a. By connecting this pin connector 16a to the connector 40a on the transmission unit 40 side, the transmission unit 40a is provided. Supply DC bias and impulse to the transmitting antenna element 1 1 from. The transmitting unit 40 is provided with a connector 4 Ob, and receives power and control signals from a signal processing unit (not shown) provided separately by connecting the connector 41.

Similarly, a coaxial cable is also used for the feeder line 17, the core wire is soldered to the top 10 a of one antenna element 10, and the shield wire is connected to the top 10 a of the antenna element 10 facing the antenna element 10. Soldered. Also, a high-frequency pin connector 17a is provided at the other end of the feeder line 17, and by connecting this pin connector 17a to the connector 50a on the receiving unit 50 side, the receiving antenna R Received signal captured Is transmitted to the reception unit 50 side. The receiving unit 50 is provided with a connector 50b. By connecting the connector 51, power is supplied from a separately provided signal processing unit (not shown), and a receiving signal and a trigger signal are provided. And so on.

The shield case 2 is provided with openings 2 a and 2 b, 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 according to the present invention is reduced in weight by mounting the antenna substrate 1 on the shield case 2 made of thin aluminum and housing the transmission unit 40 and the reception unit 50 inside. It has a structure that is extremely lightweight compared to conventional antennas that give priority to measures against unnecessary radiation.

In addition, due to the resonant structure of the antenna substrate 1 and the shield case 2, signal coupling failure (natural wave detection failure) is eliminated, and stable transmission and reception can be performed.

FIG. 5 shows a signal transmitted from the transmission unit 40 to the transmission antenna element 11 via the feeder line 16 with time on the horizontal axis and voltage level on the vertical axis. In the present embodiment, a DC bias is applied so that the core of the power supply line 16 has a 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, an electromagnetic wave is radiated from the antenna substrate 1 including the shield case 2 by applying an impulse S between the antenna elements 10 at predetermined intervals To via the feeder line 16.

By applying a DC bias, the transmission unit 40 can apply a pulse to the transmission antenna element 11 by controlling and driving the DC bias voltage in an impulse form, 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 material 30. The electromagnetic wave absorber 30 is a general-purpose thing made by sticking a conductive radio wave reflective material to a foam material, and effectively attenuates by utilizing the attenuation at the time of reflection by the reflective material. It exhibits a large attenuation characteristic with respect to electromagnetic waves of a specific polarization plane depending on the direction. In this embodiment, as shown in FIG. 6 (a), the polarization component Eo having an electric field in the width W direction of the shield case 2 is not absorbed, and the shield case 2 is shown as a broken line in FIG. 6 (b). The electromagnetic wave absorber 30 is disposed so as to attenuate the polarization component E1 having an electric field in the longitudinal H direction to the polarization component EV indicated by a solid line. That is, since the electromagnetic wave having the polarization component E1 in the longitudinal H direction of the shield case 2 contains some unnecessary frequency components different from the target frequency fo, it is necessary to absorb and remove the unnecessary frequency components. Unnecessary radiation is further reduced.

FIG. 7 shows the result of measuring the electromagnetic wave radiated from the transmitting antenna T of the electromagnetic wave radar antenna AT of the present embodiment and captured by the receiving antenna R with a frequency spectrum analyzer. Target frequency: f. It can be seen that the component of (1) protrudes and other unnecessary frequency components are effectively attenuated. In addition, since the frequency components radiated at a high level are discrete, the receiving unit side appropriately selects the receiving bandwidth to obtain, for example, the target frequency f. Different from f.周波数 2 frequencies, or 2 f. It is also possible to perform necessary measurement processing by receiving the frequency of

FIG. 8 is a waveform diagram in which the reception unit 50 amplifies the reflection wave of the electromagnetic wave radiated from the electromagnetic wave radar antenna AT of the present embodiment at the antenna substrate 1 and receives and amplifies the reflected wave. As can be seen from the figure, the target frequency f because the unnecessary frequency components are extremely reduced. It exhibits an approximately sinusoidal, distortion-free attenuation waveform based on, and is accurately demodulated down to minute amplitudes.

FIG. 9 shows a reception waveform of a reflected wave of an electromagnetic wave radiated from the electromagnetic wave radar antenna AT of the present embodiment by an object. Since the received signal does not have unnecessary frequency components superimposed on it as in the waveform of Fig. 8, it has an excellent S / N ratio and can clearly distinguish the base point, end point, and periodic fluctuation of the reflected wave RT. Peak point (1st (Peak point or second peak point, etc.) P can be easily determined, and accurate calibration and measurement can be performed.

ADVANTAGE OF THE INVENTION According to this invention, the frequency component of the electromagnetic wave radiated | emitted from a transmission antenna can be matched with a target frequency by a simple design method, and an unnecessary frequency component can be reduced. As a result, unnecessary radiation measures for complying with the regulations of the Radio Law can be made small, and the antenna itself can be made extremely lightweight and low-cost, which is suitable for portable equipment.

Also, since the SZN ratio of the received signal is improved, the circuit configuration is simple and stable, and the calibration of the receiving base point can be performed accurately.Moreover, it is possible to accurately determine the physical properties of the object through which the electromagnetic wave passes. It is possible to greatly expand the application of electromagnetic wave exploration for industrial use and consumer use.

Claims

Claims: A method for manufacturing an electromagnetic wave radar antenna, comprising: attaching a transmission antenna element that receives an impulse output from a transmission unit and radiates an electromagnetic wave to a shield case,

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 in dimensions.

An antenna substrate having a transmitting antenna element for emitting an electromagnetic wave in response to an impulse output from a transmitting 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 that the transmission antenna element emits an electromagnetic wave of the target frequency. Radar antenna. 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 includes a ground conductor made of conductive foil so as to surround the transmitting antenna element. It is arranged in a square loop so that it is symmetrical around

3. The electromagnetic wave radar antenna according to claim 2, wherein a length of a base or a side of the isosceles triangle of the transmitting antenna element is set to approximately 波長 wavelength of a target frequency.

The dimension of the shield case in a direction orthogonal to the direction in which the opposed isosceles triangles of the transmitting antenna element are arranged is set to be substantially the same length as the wavelength of the target frequency, and the depth dimension of the shield case is 1/4 of target frequency 3. The electromagnetic wave radar antenna according to claim 2, wherein the length is set to an integral multiple of the wavelength.

5. The electromagnetic wave radar antenna according to claim 4, wherein the dimensions of the shield case are corrected in accordance with an effective length in which electromagnetic waves of a target frequency are distributed on the shield case and the antenna substrate.

3. The electromagnetic wave radar 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 transmission antenna element of the antenna substrate and a ground conductor.

Among the electromagnetic wave components excited inside the shield case including the transmitting antenna element, the electromagnetic wave is absorbed inside the shield case so as to absorb and attenuate the electromagnetic wave component in which the direction of the electric field is opposite to the pair of conductive wires. 3. The electromagnetic wave radar antenna according to claim 2, wherein a material is provided.

A transmitting antenna element and a receiving antenna element having the same shape as the element are formed on the antenna substrate symmetrically, and the shield case shields electromagnetic coupling between the transmitting antenna element and the receiving antenna element. 8. The electromagnetic wave radar antenna according to claim 7, wherein a shield partition wall is provided, and the left-right direction is orthogonal to a direction in which the pair of conductive wires face each other.