CN102354794A - Omnidirectional cylindrical dipole antenna for underground earth-probing radars - Google Patents

Abstract

The invention belongs to the omnidirectional cylindrical dipole antenna for underground geological detection radar, including: a monopole antenna tubular cylinder and a conical antenna head, which are arranged between the antenna head and the antenna section and between the antenna sections. The loading resistance in the seat hole of the end face and the corresponding pressure spring, the internode fixing sleeve, the support tube, the monopole antenna composed of the nut sleeve, the connection fixing sleeve, and the coaxial cable. The invention loads resistance between the antenna head and the antenna section and between the antenna sections to change the current distribution on the surface of the antenna, which not only improves the performance of the antenna, but also simplifies the production process. Working with the borehole radar under certain conditions, the obtained waveform is neat, the main-sub-ratio is obvious, the tail is small, and the waveform is stable; therefore, the antenna has good comprehensive performance, simple structure, small diameter, and low production cost. It can be used in low frequency bands and Under the condition of large bandwidth, it is matched with the borehole radar, which effectively improves the performance, detection range and efficiency of the borehole radar.

Description

An omnidirectional cylindrical dipole antenna for underground geological detection radar

technical field

The invention belongs to a dipole antenna used in conjunction with a detection radar, in particular to a broadband low-frequency omnidirectional cylindrical dipole antenna used in geological drilling wells in conjunction with a geological detection radar and loaded with resistance; the antenna can be used through Geological drilling wells work deep underground, and are used in conjunction with geological detection radar for geological environment investigation and resource exploration.

Background technique

Ground-penetrating radar is an efficient shallow geophysical detection technology. It transmits high-frequency pulsed electromagnetic waves, uses the difference in the electrical parameters of the underground medium, and analyzes and infers the structure and material of the underground medium according to the characteristics of the amplitude and phase of the echo. feature. The geophysical methods generally adopted by geological radar are carried out on the surface of the ground or the surface of the object to be measured. However, due to the complex structure of the underground or the interior of the object to be measured, it is difficult to accurately infer the geological or object to be measured only by the data obtained from these methods. To measure resource characteristics, orientation and other information, the application of borehole radar for deeper downhole detection has become a necessary means. As the core component of the borehole radar imaging system, the antenna directly affects the detection range and accuracy of the radar. In order to obtain waveforms that are easy to identify and have good fidelity, the antenna needs to have a wide bandwidth; at the same time, the lower the operating frequency of the antenna, the longer the propagation distance in the rock and soil, and the larger the radar detection range, but if the bandwidth is narrow, the waveform It is prone to distortion, so low-frequency antennas become an ideal choice when the bandwidth is sufficient. In the patent document with the publication number CN101908669A and the name "Four-Branch Multi-Frequency Cylindrical Dipole Antenna", an antenna mainly composed of the first, second, third, and fourth branches, exposed copper area, and feed source is disclosed . The exposed copper area is a hollow copper rod (tube), and the feed source is a thin solid copper rod; the first and second branches are located under the third and fourth branches; the feed source passes through the circuits on the third and fourth branches and the three 1. The four branches are connected; the exposed copper area is connected with the first and second branches through the circuit on the first and second branches, and the exposed copper area is also connected with the top of the first branch and the lower end of the second branch. Since the feed source is connected to the third and fourth branches at the same time, the third and fourth branches are in parallel structure; the exposed copper area is connected to the first and second branches at the same time, so the first and second branches are also in a parallel structure. The working frequency of the antenna is between 700M and 2500M, the working frequency is high and the bandwidth is only 50-60M, and the circuit is connected to the four branches correspondingly, so that the feed source and each branch can be better matched, which is helpful for the antenna Bandwidth expansion; however, the fourth branch adopts a helical structure, which increases the length of the antenna and also brings a part of the inductance effect. In addition, although the increase in the number of branches can increase the bandwidth to a certain extent, but at the same time The fluctuation (range) of S11 (antenna feed point voltage reflection coefficient) within its bandwidth is also very large, that is, the radiated energy at each frequency has a large difference, which will cause distortion of the time-domain waveform of antenna radiation, and cannot be used with pulse radar ; In addition, the antenna is an active antenna with a complex structure, and it is difficult to be used in conjunction with the borehole radar.

Contents of the invention

The object of the present invention is to aim at the defects existing in the background technology, research and design a kind of omnidirectional cylindrical dipole antenna for underground geological detection radar, to simplify the antenna structure, reduce the production cost, and can work with the low frequency band and sufficient bandwidth condition The supporting work of the geological borehole radar is to improve the detection range in the rock-soil medium; so as to achieve the purpose of simple antenna structure and effectively improve the performance, detection range and efficiency of the geological radar.

The solution of the present invention is to adopt metal cylinders as each antenna section in two (root) tubular monopole antenna cylinders in the dipole antenna of the present invention; the antenna head then adopts a tapered head with a central hole, And set at the inner ends of the two monopole antenna cylinders, the front faces of the two conical heads are perpendicular to the antenna axis (center line), and the rear part is a cylindrical body with the same diameter as the antenna section; between the antenna sections and the antenna A group of seat holes are respectively provided on the two ends between the section and the antenna head in the axial direction, which are used to install the loading resistor; when assembling, each antenna section and antenna head in a (root) monopole antenna body are placed in sequence. On the (inner) support tube, and in the seat hole between the antenna sections and the front antenna section and the antenna head, a pressure spring, a resistor and an inter-segment fixing sleeve are installed to connect the antenna sections and the antenna head in series and pass through The nut sleeve is fixed to form a tubular monopole antenna; finally, the antenna heads of the two (roots) monopole antennas are fastened together axially through the connecting fixing sleeve at intervals, and the coaxial cable is passed through a single The support pipe of the pole antenna cylinder and the inner hole of the central hole of the antenna head are penetrated, and the center line and the outer (layer) wire of the coaxial cable are respectively fastened and connected with the two antenna heads. Therefore, the omnidirectional cylindrical dipole antenna of the present invention comprises two (roots) monopole antennas and connection fixing sleeves respectively containing the monopole antenna cylinder and the antenna head, (for connecting the feed source) with The key is that each monopole antenna cylinder is a tubular cylinder formed by connecting tubular antenna sections in series, and the two antenna heads are conical heads with a central hole in the front and a cylindrical body in the rear. Conical antenna heads, each conical antenna head is respectively arranged at the inner end of the two monopole antenna tubular cylinders, and a support tube is also arranged in the two monopole antenna tubular cylinders and the antenna head. Between the head and the antenna sections and on the two ends of the antenna sections along the axial direction, there are respectively a set of seat holes for installing the loading resistors, and each set of loading resistors and corresponding pressure springs are respectively embedded in the corresponding seat holes , and the adjacent two ends are isolated from each other; between the antenna section and the antenna head, between the antenna sections, together with the loading resistor and the pressure spring, are connected in series on the support tube through the corresponding inter-section fixing sleeve and fixed by the nut sleeve , to form a (root) monopole antenna; finally, the two monopole antenna heads are fixed axially opposite each other by connecting the fixing sleeve, and the center line and outer (layer) wire of the coaxial cable are connected with the two monopole antennas respectively. After the conical antenna head of the pole antenna is fixedly connected, it is led out through the inner cavity of any support tube.

Between the antenna head and the antenna section and on the two end surfaces between the antenna sections, there are respectively a set of seat holes for installing the loading resistor in the axial direction. The number of each set of seat holes is 3-6, adjacent to each other. The corresponding two seat holes on the end face are located on the same axis. The two monopole antennas containing the monopole antenna tubular cylinder and the antenna head, wherein each monopole antenna includes 1 antenna head and a monopole composed of 5-9 tubular antenna sections antenna. Described monopole antenna, when each monopole antenna adopts 1 antenna head and 7 antenna joints, the resistance resistance loaded between the antenna head and the antenna joints is 4-6 ohms, and the resistance between the antenna joints is 4-6 ohms. The resistance value of the loaded resistance is 8-10 ohms, 14-18 ohms, 28-32 ohms, 44-52 ohms, 65-75 ohms, 90-110 ohms from the inside to the outside. The resistors loaded between the antenna sections are parallel resistors. The connecting and fixing sleeve includes a cylindrical hole arranged in the middle of the inner cavity of the connecting and fixing sleeve, and taper holes respectively arranged at both ends of the cylindrical hole and the two ends of the connecting and fixing sleeve.

The invention adopts the method of loading resistance between the antenna head and the antenna section of two (root) monopole antennas and between each antenna section to change the current distribution on the surface of the antenna without filling the medium, and effectively improves the performance of the antenna. The performance simplifies the production process at the same time, so that it can work with the geological drilling radar under the condition of low frequency band and sufficient bandwidth, and detect a longer distance in the rock and soil medium, and a wider range can be obtained through a single drilling hole Geological and resource information, thereby greatly improving radar detection efficiency and detection range in rock-soil media; the omnidirectional cylindrical dipole antenna of the present invention can be used with geological drilling under the condition that the center frequency is about 100M and the bandwidth is ≥ 120M. Radar supporting work, the radiation waveform obtained is neat, the main-sub-ratio is obvious, and the tail is very small. When the rock permittivity and conductivity change, its waveform is also relatively stable; thus the omnidirectional cylindrical dipole antenna of the present invention has an antenna The comprehensive performance is good, the structure is simple, the diameter is small, and the production cost is low. It can work with the geological drilling radar under the condition of low frequency band and sufficient bandwidth, and can effectively improve the performance, detection range and efficiency of the geological radar.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the S11 (antenna feed point voltage reflection coefficient) curve coordinate diagram of emulation operation of the embodiment of the present invention;

Fig. 3 is a time-domain electric field waveform diagram (coordinate diagram) of antenna radiation in simulation operation according to a specific embodiment of the present invention.

In the figure: 1. (tubular) antenna section, 2. support tube, 3. intersegmental fixing sleeve, 4. loading resistor, 5. pressure spring, 6. antenna head, 6-1. (antenna head) center hole, 7. Connect the fixed sleeve, 8-1. The center line of the coaxial cable, 8-2. The outer (layer) wire of the coaxial cable, 9. The nut sleeve.

Detailed ways

In this embodiment, the length of each (root) monopole antenna (that is, the length of half the vibrator of the antenna) is 1065mm, and the omnidirectional cylindrical dipole antenna for underground geological detection radar including 7 antenna sections 1 and one antenna head 6 is Example: The axial length of each antenna head 6 is 50mm, of which the length of the conical head is 30mm, the diameter of the upper bottom is Φ20mm, the diameter of the lower bottom is Φ40mm, the diameter of the center hole is Φ8mm, the inner and outer diameters of the rear cylindrical shape are Φ30mm and Φ40mm respectively, and the material is Stainless steel; the axial length of each tube-shaped antenna section 1 is 140 mm, the inner and outer diameters are Φ30 mm and Φ40 mm, and the material is also stainless steel; the rear end surface of the antenna head 6 and the adjacent end surfaces of each antenna section 1 are spaced at 90° Set 4 seat holes with a diameter of Φ3mm and a depth of 7.5mm for installing the loading resistor 4; two support tubes 2, each 1035mm long, with inner and outer diameters of Φ20mm and Φ30mm, made of plastic; each loading resistor 4 The length is 10mm, and the diameter is Φ2.5mm. In this embodiment, four resistors are respectively arranged along the axial direction between the antenna head 6 and the antenna section 1 and on the two ends of each antenna section 1, wherein: the antenna head 6 The resistance values of the four resistors between the antenna section 1 are 20Ω respectively, and then the resistance values of each group (4) of resistors are set on the two ends of each antenna section 1 in the order from the inside to the outside. They are respectively 36Ω, 64Ω, 120Ω, 192Ω, 280Ω, 400Ω; the inner and outer diameters of the intersegmental fixed sleeve 3 are Φ30mm and Φ50mm respectively, the axial length of the outer ring part is 15mm, and the part embedded between the two end faces is axially The thickness is 5mm, and the material is insulating plastic, and 4 through holes with a diameter of Φ3mm are arranged at intervals of 90° to fix the loading resistor 4; the pressure spring 5 has a diameter of Φ2.5mm and a length of 10mm (the length after compression is 5mm); The fixed sleeve 7 has an axial length of 104mm, an outer diameter of Φ50mm, an inner diameter of Φ20mm in the middle, and a length of 40mm. The inner diameter of the tapered hole matched with the tapered head at both ends is Φ20mm, and the outer diameter is Φ40mm; 1. The inter-segment fixing sleeve 3 and the pressure spring 5 are placed on the support tube 2 successively as required, and after the pressure spring 5 and each loading resistor 4 are loaded in sequence, each antenna section and the support tube 2 are fixed and assembled into a single unit with nut sleeves. pole antenna; then the ends of the coaxial cable center line 8-1 and the coaxial cable outer (layer) conductor 8-2 are respectively fixed with the antenna heads 6 on the two monopole antennas, and finally the two monopole The antenna heads 6 on the antenna are respectively inserted into the tapered holes at both ends of the fixing sleeve 7 and fixed by bonding, that is, the omnidirectional cylindrical dipole antenna for underground geological detection radar in this embodiment is produced.

The antenna is installed in a pvc tube with an outer diameter of 90mm and an inner diameter of 76.6. It is excited by a first-order Gaussian pulse with a center frequency of 100M, a bandwidth of 120M, and a bottom width of 10ns. The simulation is performed under a rock background with a dielectric constant of 8. Among them: Figure 2 , Accompanying drawing 3 promptly is respectively the S11 (antenna feed point voltage reflection coefficient) curve diagram (coordinate diagram) and the time-domain electric field wave diagram (coordinate diagram) of antenna radiation of the obtained omnidirectional cylindrical dipole antenna simulation operation of the present embodiment ). It can be seen that:

The S11 curve (see Figure 2) is very flat, the fluctuation in the frequency range of 40M-500M is only 2.5dB, and the fluctuation in the range of 40M-200M is only 1.24dB;

However, the electric field waveform radiated by the antenna (see Figure 3) is neat, the main-to-subsidiary ratio is obvious (the ratio is 1.78), and the tail after 10 ns of the main peak is less than 1/30 of the main peak, so the waveform is easy to identify.

Claims (5)

1. a down-hole earth-probing radar is with omnidirectional's cylindricality dipole antenna; Comprise two monopole antennas that contain monopole antenna cylinder and aerial head respectively and be connected fixed cover; Coaxial cable; It is characterized in that each monopole antenna cylinder is the tubular cylinder that adopts each tubulose antenna section to be in series; Two aerial heads are the conical head of anterior band centre bore; And the rear portion is the conical antenna head of cylindrical body; Each conical antenna head is located at the inner of two tubular cylinders of monopole antenna respectively; In two tubular cylinders of monopole antenna and aerial head, also be provided with a stay pipe; To being respectively equipped with one group of seat hole that is used to install loading resistor, each organizes loading resistor and corresponding compression spring is embedded in respectively in the corresponding seat hole at direct-axis between aerial head and the antenna section and on the both ends of the surface between each antenna section; And adjacent both ends of the surface are isolated each other; All be series on the stay pipe and successively between antenna section and the aerial head, between each antenna section, together with loading resistor and compression spring and fix, to form a monopole antenna through nut sleeve through corresponding internode fixed cover; Through connecting fixed cover two monopole antenna heads axially are fixed into one in opposite directions at last, and the center line of coaxial cable is fixedly connected the back respectively, draws through arbitrary stay pipe inner chamber with the conical antenna head of two monopole antennas with outer conductor.

2. press the said down-hole of claim 1 earth-probing radar with omnidirectional's cylindricality dipole antenna; It is characterized in that said at direct-axis between aerial head and the antenna section and on the both ends of the surface between each antenna section to being respectively equipped with one group of seat hole that is used to install loading resistor, every group of seat hole count is that each two corresponding seat hole is positioned on the same axis on 3-6, adjacent both ends face.

3. press the said down-hole of claim 1 earth-probing radar with omnidirectional's cylindricality dipole antenna, it is characterized in that said two monopole antennas, wherein each monopole antenna comprises 1 aerial head and the monopole antenna of being made up of 5-9 tubulose antenna section.

4. press claim 1 or 3 said down-hole earth-probing radars with omnidirectional's cylindricality dipole antenna; It is characterized in that said monopole antenna; The resistance that when each monopole antenna adopts 1 aerial head and 7 antenna sections, between aerial head and the antenna section, is loaded is 4-6 ohm; The resistance that is loaded between each antenna section is followed successively by 8-10 ohm, 14-18 ohm, 28-32 ohm, 44-52 ohm, 65-75 ohm, 90-110 ohm from the inside to the outside, reaches the resistance that is loaded between each antenna section between above aerial head and the antenna section and is the parallel resistance value.

5. press the said down-hole of claim 1 earth-probing radar with omnidirectional's cylindricality dipole antenna; It is characterized in that said connection fixed cover comprises the cylindrical hole of being located at connection fixed cover inner chamber middle part, and be divided into these cylindrical hole two ends to the taper hole that connects the fixed cover both ends of the surface.

Images