JP4875533B2 - Waterproof antenna device - Google Patents

Description

  The present invention relates to a waterproof antenna device for detecting earth and sand in flowing water in mountainous rivers, in particular, sweeping sand.

  In the past, as a method of measuring sweeping sand during floods and small and medium floods, it is collected in a container such as a bucket at regular intervals, and the amount and quality of sediment contained in the volume is measured, or instead of a bucket A scavenging sand collector is used that captures the scavenging sand that has flowed in while being divided into stages according to the particle size by a plurality of sorting nets (Patent Document 1).

  Moreover, the method of using a scavenging sand trap apparatus (patent document 2) attached to the whole surface part of the water top of the sabo dam is used.

On the other hand, a method (Non-patent Document 1) for indirectly estimating the amount of sand flow from the number of acoustic pulses generated when the sand sand impacts a metal pipe installed in the slit section of the riverbed or slit sabo dam is proposed. .
Japanese Patent Laid-Open No. 2003-3442 JP 2002-294670 A "Application of hydrosand measurement to hydraulic model experiment" Journal of Sabo Society vol.58 No.2, p.15-25,2005

  According to the above-mentioned conventional technology, the above-mentioned Patent Documents 1 and 2 are mainly performed by direct sampling downstream of the river, and are greatly affected when the temporal sand flow rate changes drastically or when the measurement takes a long time. Requires a lot of effort. In Non-Patent Document 1 described above, the collectability of the detection signal is determined by the size of the metal tube used, so that its application range is narrow and lacks universality. Moreover, since the sweeping sand floating in water does not come into contact with the metal pipe, it is assumed that no signal can be obtained.

  Therefore, it is possible for humans to observe the situation at an appropriate place on the riverbed or sabo levee for a long time without directly collecting the sweeping sand, and it is possible to capture the presence of it regardless of whether it is in contact or non-contact with the sweeping sand. The present applicant has proposed to use a radar as a technique.

  When the radar is used, since the transmission / reception antenna is used in a state of being submerged in water, an antenna device having directivity capable of detecting gravel flowing on the river bed while maintaining waterproofness is required.

  The present invention has been made in view of such a viewpoint, and an object of the present invention is to provide a waterproof antenna device having directivity capable of detecting gravel flowing on a river bed while maintaining waterproofness and easy to handle.

  A first configuration of a waterproof antenna device that realizes the object of the present invention is a non-metallic pipe that is closed at both ends with a watertight structure. A coaxial cable inserted along the axial direction; a conductive plate made of a conductive triangular plate member connected to an insertion tip of the coaxial cable inserted in the waterproof cylinder; and the waterproof A radio wave absorption layer formed on the outer periphery of the coaxial cable inserted in the cylinder, and connecting the apex angle of the conductor plate to the central conductor of the coaxial cable, and the bottom of the conductor plate and the The outer conductor of the coaxial cable is connected via a resistor, and the oblique side of the conductor plate is arranged in the vertical direction.

  According to a second configuration of the waterproof antenna apparatus that realizes the object of the present invention, in the above configuration, a conductive member that reflects a transmission wave from the transmission antenna toward the reception antenna is fixed in the water surface above the waterproof cylinder. It is characterized by being arranged at a distance.

  A third configuration of a waterproof antenna apparatus that achieves the object of the present invention is characterized in that, in each of the above-described configurations, the resistor is connected to two spaced apart portions of the bottom of the conductor plate.

  According to the waterproof antenna device of the present invention, by arranging the waterproof cylinder along the river flow, for example, it is possible to obtain directivity capable of detecting gravel flowing in the river bed with the minimum flow resistance. .

  In particular, by setting the conductor plate to an isosceles triangle, the base and height are about 2 cm and about 3 cm, and the resistor is set to 33Ω, the loss is relatively low when radio waves pass through water. 400 MHz can be obtained with a simple configuration and can be configured compactly.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  1 to 3 show an embodiment of the present invention, FIG. 1 is a block diagram of an impulse radar system, FIG. 2 is a diagram showing a structure of a waterproof antenna shown in FIG. 1, and FIG. It is a flowchart which shows a signal processing.

  In FIG. 1, the controller 11 constituting the transmission / reception unit 1 repeatedly transmits a pulse serving as a transmission trigger for causing the impulse generator 12 to generate an impulse wave (for example, at intervals of 1 μs). The impulse generator 12 is repeatedly triggered by the controller 11, has a maximum power of about 30 dBm, and repeatedly transmits an impulse wave having a pulse width of 0.5 ns to 1 ns to the transmission antenna 21 of the waterproof antenna device 2. To do.

  The transmission antenna 21 of the waterproof antenna device 2 receives an impulse wave from the impulse generator 12, converts this electric signal into a radio wave, and radiates an electromagnetic wave in water. The waterproof antenna device 2 receives the composite wave reflected from the sweeping sand 5 flowing in the water, for example, stone or sand, in addition to the radio wave directly coupled from the radio wave radiated from the transmission antenna 21 by the reception antenna 22. After this is converted into an electrical signal, it is transmitted to the sample and hold circuit 14 via the amplifier 13 constituting the transmission / reception unit 1. In this case, a wave on the water surface may interfere with the composite wave, and in order to alleviate this, the transmitting antenna 21 and the receiving antenna 22 are provided with a wave-preventing conductor 23.

  The sample and hold circuit 14 has a function of capturing a part of one wave of the input signal instantaneously, for example, at 128 ps, and is controlled by a phase shifter 15 controlled by the controller 11 constituting the transmission / reception unit 1. Then, a signal repeatedly input is adjusted after a delay time adjustment, for example, after a time delay of 128 ps, and then detected and transmitted to an A / D converter 17 via a low-pass filter (LPF) 16.

  The A / D converter 17 repeatedly A / D-converts the electrical signal received from the LPF 16 and transmits it to the controller 11.

  The controller 11 stores the digital data received from the A / D converter 17 in an internal memory (not shown) provided therein. The internal memory stores a data amount corresponding to a power of 2 (in this embodiment, 256 detection data, and the unit of detection is hereinafter referred to as BIN) × a plurality of data.

  Here, “the data amount of power of 2” means that the electric signal output from the receiving antenna 22 can be digitally restored by combining them. “Multiple” means the amount of data accumulated for improving the S / N ratio (SNR), and is 100 in this embodiment.

  The controller 11 sucks up the data stored in the internal memory at regular intervals (for example, every 0.1 sec), converts the level via the interface (I / F) 18, and then configures an interface ( I / F) 31.

  The interface (I / F) 31 of the signal processing unit 3 performs level conversion on the data transmitted from the interface (I / F) 18 of the transmission / reception unit 1 and then transmits the data to the calculation unit 33.

  The calculation unit 33 is configured by a DSP (Digital Signal Processor), a general-purpose PC, or the like, and performs signal processing according to the flowchart shown in FIG. 3, and is one-dimensional (A mode: horizontal axis is time axis and vertical axis is amplitude). Mode) or two-dimensional (B mode: for example, the horizontal axis is the number of measurements or the measurement time, and the vertical axis is the delay time of the radio wave propagated from the transmitting antenna to the receiving antenna). And stored in a built-in recording medium (not shown).

  The controller 11 of the transmission / reception unit 1 is equipped with software for controlling the system, and has a function of performing measurement operations such as measurement start and stop.

  The power supply unit 4 that supplies power to the transmission / reception unit 1 and the signal processing unit 3 takes into account that the installation location of the antenna is in the mountains where commercial power cannot be used, for example, a hydroelectric generator 41, a wind power generator 42, a solar battery 43, a secondary battery 44, and the like.

  With reference to FIG. 2, the structure of the transmitting antenna 21 and the receiving antenna 22 of the antenna device 2 will be described.

  In these antennas, a rigid coaxial cable 203 is connected from one end side to a substantially other end in a non-metallic waterproof tube 202 made of a cylindrical vinyl chloride pipe often used for water pipes for waterproofing. Inserted to the side.

  Then, as shown in FIG. 2B, a triangular conductive plate having a base a of about 2 cm and a height b of about 3 cm is provided at the insertion tip of the rigid coaxial cable 203 in order to increase the bandwidth. A wideband monopole antenna is constructed in which a conductor plate 207 is attached, and two 33 Ω resistors 209 are connected to the base angle thereof. Therefore, the conductor plate 207 is supported in the waterproof cylinder 202 without blurring.

  The size of the hypotenuse d obtained by setting the base a of the conductor plate 20 7 formed in an isosceles triangle to about 2 cm and the height b to about 3 cm is set in this way when radio waves pass through water. Furthermore, since the frequency with relatively little loss is in the vicinity of 400 MHz, it is caused by considering the numerical value calculated using Equation (1) and the ease of manufacture.

d = c / (4f√ (εr)) (1)
However, d> √ {(a / 2) ² + b ² }
Here, f is the frequency (= 400 × 10 ⁻⁶ ), εr is the relative dielectric constant of water (= 81), and c is the speed of light (= 3 × 10 ⁸ ). Waterproof members 201 and 204 that prevent water from entering the waterproof cylinder 202 from both ends of the waterproof cylinder 202 are provided at the front end and the rear end of the waterproof cylinder 202. In the present embodiment, the waterproof members 201 and 204 are configured by sticking a waterproof tape to the waterproof cylinder 202. The waterproof members 201 and 204 are configured such that a cap member is screwed into the end of the waterproof cylinder 202, and an O-ring is provided between the waterproof cylinder 202 and the cap member to prevent water from entering the inside. You may make it do.

  At the rear end portion of the waterproof member 204 on the rear end side, a waterproof connector 205 is provided in which the external connector portion is detachably fitted to the internal connector portion to which the rigid coaxial cable 203 is attached. Is fixed integrally with the waterproof member 204 on the rear end side, and a soft coaxial cable 206 is attached to the external connector portion exposed from the waterproof member 204 on the rear end side. Electrical connection with the coaxial cable 206 is made. Although a connector having a waterproof property is used as the connector 205, a waterproof tape may be wound around the connector 205 depending on a change with time, a manufacturing finish, or the like.

  The outer periphery of the coaxial cable 203 is covered with a radio wave absorber 208. The radio wave absorber 208 absorbs current leaking from the conductor portion 207 and suppresses the radio wave generated secondarily. The signal is captured by the conductor portion 207.

  FIG. 2C shows the antenna directivity 10 viewed in the vertical direction, and has a characteristic that allows the conductor portion 207 to efficiently transmit and receive radio waves in the vertical direction.

  In FIG. 3, the operation of the calculation unit 33 shown in FIG.

  In the flowchart shown in FIG. 3, step (abbreviated as S) 1 acquires A-mode data and stores it in a built-in memory.

  In S2, data in A mode (one-dimensional data with the horizontal axis as time and the vertical axis as amplitude) is arranged in the vertical axis direction and data in B mode (two-dimensional data joined to the horizontal axis at every measurement time) is obtained. In creation, the data is stored in the memory until the set number m is reached. In this case, since the number of data points in the A mode is 256 BIN in the memory, 256 BIN × m points of data are stored in the memory.

  In S3, the oldest A-mode data is erased from the memory in order to update the data.

Block diagram of a radar system comprising an antenna device according to the invention It is a figure which shows the antenna apparatus of FIG. 1, (a) is sectional drawing of an antenna, (b) is a figure which shows the connection structure of a conductor and a coaxial cable, (c) is a figure which shows directivity. The flowchart which shows the signal processing in the radar system of FIG.

Explanation of symbols

1: Transmitter / receiver 11: Controller 12: Impulse generator 13: Amplifier 14: Sample hold circuit 15: Phase shifter 16: Low-pass filter (LPF)
17: A / D converter 18: Level converter (I / F)
2: antenna device 21: transmitting antenna 22: receiving antenna 23: conductor for wave protection 201, 204: waterproof member 202: waterproof tube 203: rigid coaxial cable 203a: inner conductor 203b: outer conductor 205: connector 206: flexible coaxial cable 207: Conductor plate 208: Radio wave absorber 209: Resistor 10 Directionality 3: Signal processing unit 31: Level converter (I / F)
32: Controller 33: Calculation unit 34: Display unit 4: Power supply unit 41: Hydroelectric generator 42: Wind power generator 43: Solar battery 44: Secondary battery 5: Sediment sand

Claims (3)

A waterproof cylinder made of a non-metallic pipe whose both ends are blocked by a watertight structure,
A coaxial cable inserted along the axial direction in the waterproof cylinder;
A conductive plate made of a triangular plate member having conductivity connected to the insertion tip of the coaxial cable inserted in the waterproof cylinder;
A radio wave absorption layer formed on the outer periphery of the coaxial cable inserted in the waterproof cylinder,
Have
The apex angle of the conductor plate is connected to the central conductor of the coaxial cable, the bottom side of the conductor plate and the outer conductor of the coaxial cable are connected via a resistor, and the oblique side of the conductor plate is directed vertically. A waterproof antenna device characterized by being arranged.   The waterproof antenna apparatus according to claim 1, wherein a conductor member that reflects a transmission wave from the transmission antenna toward the reception antenna is disposed at a predetermined distance in the water surface above the waterproof cylinder.   3. The waterproof antenna device according to claim 1, wherein the resistor is connected to each of two spaced apart portions of the bottom of the conductor plate. 4.

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