Welding-free octave broadband omnidirectional antenna

Abstract

The invention discloses a welding-free octave broadband omnidirectional antenna, and belongs to the technical field of antennas. The antenna comprises an upper-layer metal cylinder, an upper-layer conical part, a lower-layer metal cylinder, a lower-layer conical part, a middle-layer metal cylinder, a customized cable assembly, a base, a medium supporting block, a metal connecting part, a medium supporting cylinder, a medium ring, an antenna housing outer cylinder, an antenna housing cap and the like. The bandwidth of the antenna is effectively expanded to be within the octave, omnidirectional radiation of the broadband of 330 MHz to 660 MHz is achieved, the antenna is integrally assembled without welding, and the antenna is good in directional diagram consistency and small in out-of-roundness in the working frequency band. The welding-free octave broadband omnidirectional antenna has the advantages of being compact in structure, low in cost, wide in frequency band, easy to produce in batches, easy to integrate with an antenna housing or other carrier platforms and the like, a welding-free feeding mode is adopted, labor and time cost is greatly saved, and antenna assembling efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and in particular to a welding-free octave-band broadband omnidirectional antenna. Background Art

[0002] In the field of UAV measurement and control, the antenna is required to have the ability to radiate and receive in different directions at low elevation angles. Therefore, omnidirectional antennas are often the best choice. Omnidirectional antennas have full coverage in the horizontal plane and appear as beams with a certain width in the vertical plane.

[0003] Omnidirectional antennas are generally classified into three types: horizontally polarized, vertically polarized, and circularly polarized. These include helical antennas, waveguide slot antennas, monopole antennas, and dipole antennas. With the advancement of modern communication technology, antennas are increasingly required to have wide bandwidths and be smaller and smaller. This effectively reduces the overall RCS of the platform, increases platform maneuverability, and improves antenna concealment. Furthermore, antenna installation space limitations often place even higher demands on the antenna.

[0004] When omnidirectional antennas use ultra-wideband technology, they usually have to take into account the resonant lengths of different frequency bands at the same time, making it difficult to reduce the antenna size and even making it larger. However, electrically small antenna technology usually narrows the antenna's operating frequency band. Therefore, there is a contradiction in simultaneously solving the problems of broadbandization and miniaturization of omnidirectional antennas. Therefore, broadbandization and miniaturization are currently issues that need to be urgently addressed. Summary of the Invention

[0005] In view of this, the present invention provides a solderless octave broadband omnidirectional antenna. The antenna of the present invention has the characteristics of compact structure, low cost, wide bandwidth, easy mass production, no soldering, easy integration with antenna cover or other carrier platform, etc. The antenna direction within the working frequency band is Figure 1 Good consistency.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A welding-free octave-band broadband omnidirectional antenna, comprising an antenna cover outer tube 12, a dipole antenna, a dielectric support block 8 and a dielectric support tube 10 arranged inside the antenna cover outer tube;

[0008] The dipole antenna comprises an upper metal cylinder 1, an upper conical member 2, a lower conical member 4, and a lower metal cylinder 3, which are arranged in sequence from top to bottom. The metal cylinder is a hollow cylinder, and the conical member is a stepped hollow cone. The two conical members are symmetrically arranged, and the upper conical member 2 and the lower conical member are connected to the upper metal cylinder and the lower metal cylinder, respectively.

[0009] The dielectric support cylinder 10 is located between the upper and lower conical members, and its two ends are connected to the corresponding conical members respectively; the outer side of the dielectric straight cylinder is sheathed with a middle metal cylinder 5, and the upper metal cylinder 1 and the lower metal cylinder do not touch the middle metal cylinder;

[0010] The lower metal cylinder 3 is connected to the base 7 through the dielectric support block 8; the cable assembly 6 is installed on the lower surface of the base, and the SMP type plug on its top passes through the dielectric support block 8, the lower metal cylinder 3 and the lower conical part in sequence and is connected to the upper conical part.

[0011] Furthermore, one end of the upper tapered member is connected to the upper metal cylinder, and the other end is provided with an SMP-type card hole, which matches the SMP-type plug end of the cable assembly.

[0012] Furthermore, one end of the lower conical part is connected to the lower metal cylinder, and the other end has a threaded buckle inside, which is used to match the threaded metal part of the customized cable assembly; the cable assembly passes through the interior of the lower metal cylinder and the lower conical part, and the outer conductor of the cable assembly is fixedly contacted with the lower conical part through the threaded buckle; the inner core of the cable assembly is inserted into the upper conical part through an SMP-type plug.

[0013] Furthermore, a radome cap is provided on the top of the radome, and the base serves as the bottom plate of the radome, and the three constitute a closed space; the radome is made of a hollow cylindrical fiberglass material.

[0014] Furthermore, the radome and the base are threadedly connected.

[0015] Furthermore, the SMP type plug is located at the end of the inner conductor of the cable assembly; the threaded metal part and the metal limiter are both installed on the cable assembly, the threaded metal part is connected to the outer conductor of the cable assembly, and the metal limiter is installed on one side of the threaded metal part.

[0016] Furthermore, it also includes two dielectric rings; the dielectric rings are both sleeved on the middle metal cylinder and used to clamp the middle metal cylinder on the dielectric support cylinder.

[0017] The beneficial effects of the above technical solution of the present invention are:

[0018] The present invention solves the technical problem that it is difficult for ground-based UHF band omnidirectional antennas to achieve wide bandwidth under the condition of limited antenna diameter. Through a customized cable assembly and a special form of dipole antenna, the antenna bandwidth is effectively expanded to within the octave, achieving omnidirectional radiation of a wide frequency band of 330MHz to 660MHz. The overall assembly of the antenna is solder-free, and the antenna direction is fixed within the working frequency band. Figure 1The solderless octave broadband omnidirectional antenna of the present invention has the characteristics of compact structure, low cost, wide bandwidth, easy mass production, and easy integration with radomes or other carrier platforms. It also adopts a solderless feeding method, which greatly saves manpower and time costs and improves antenna assembly efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the antenna structure according to an embodiment of the present invention;

[0020] Figure 2 for Figure 1 Structural schematic diagram and structural cross-section of the middle and upper cone parts;

[0021] Figure 3 for Figure 1 Structural schematic diagram and structural cross-section of the middle and lower cone parts;

[0022] Figure 4 for Figure 1 Schematic diagram of the structure of the customized cable assembly;

[0023] Figure 5 for Figure 1 Schematic diagram of the structure of the medium support tube;

[0024] Figure 6 for Figure 1 Schematic diagram of the structure of the medium ring;

[0025] Figure 7 for Figure 1 Schematic diagram of the structure of the medium support block;

[0026] Figure 8 for Figure 1 The structure and size parameter drawing of the middle base;

[0027] Figure 9 yes Figure 8 A side sectional view of

[0028] Figure 10 This is a curve diagram of the antenna voltage standing wave ratio calculated according to an embodiment of the present invention.

[0029] Figure 11 These are the directional patterns of the four frequencies of 330 MHz, 360 MHz, 580 MHz, and 660 MHz within the antenna bandwidth calculated in an embodiment of the present invention.

[0030] In the figure: 1-upper metal cylinder 2-upper conical part 3-lower metal cylinder 4-lower conical part 5-middle metal cylinder 6-customized cable assembly 7-base 8-dielectric support block 9-metal connector 10-dielectric support tube 11-dielectric ring 12-radome outer tube 13-radome cover DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] A solder-free octave-band broadband omnidirectional antenna, comprising a dipole antenna, a customized cable assembly, a dielectric support block, a dielectric support tube, a dielectric ring, a radome and other components;

[0033] The dipole antenna comprises an upper metal cylinder, an upper conical member, a lower metal cylinder, a lower conical member and a middle metal cylinder, wherein the upper metal cylinder and the lower metal cylinder are hollow cylindrical; the upper conical member and the lower conical member are stepped hollow cones, and the upper conical member and the lower conical member are connected to the upper metal cylinder and the lower metal cylinder respectively; the middle metal cylinder is located in the middle of the dipole antenna, and its outer surface does not contact the upper metal cylinder and the lower metal cylinder; the upper conical member and the lower conical member are stepped hollow cones, and the upper conical member and the lower conical member are connected to the upper metal cylinder and the lower metal cylinder respectively; the middle metal cylinder is located in the middle of the dipole antenna, and its outer surface does not contact the upper metal cylinder and the lower metal cylinder; the upper conical member An SMP-type card hole is provided on the end of the conical part, which just matches the SMP-type plug end of the custom cable assembly; the end of the lower conical part is internally provided with a threaded buckle, which just matches the threaded metal part of the custom cable assembly; the custom cable assembly passes through the lower metal cylinder and the interior of the lower conical part, and the outer skin of the custom cable assembly is fixedly contacted with the lower conical part through the threaded buckle; the inner core of the custom cable assembly is inserted into the end of the upper conical part through the SMP-type plug and fixedly contacts it.

[0034] The base is on the bottom plate of the antenna cover and forms a confined space with the antenna cover; the dipole antenna and the dielectric support block, dielectric support tube, and dielectric ring are all located in the confined space, wherein the bottom of the dielectric support block is fixed to the base; the dipole antenna is fixed to the upper surface of the dielectric support block; one end of the customized cable assembly is located in the confined space, its outer conductor is connected to the lower tapered part, and the inner conductor passes through the lower tapered part, the dielectric support tube, and the dielectric ring to be connected to the upper tapered part; the other end of the customized cable assembly passes through the dielectric support block and is connected to the base.

[0035] Furthermore, the radome is composed of a radome outer tube and a radome cover cap, and the radome outer tube is threadedly connected to the base.

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] A welding-free octave-band broadband omnidirectional antenna comprises an upper metal cylinder, an upper conical part, a lower metal cylinder, a lower conical part, a middle metal cylinder, a customized cable assembly, a base, a dielectric support block, a metal connector, a dielectric support tube, a dielectric ring, a radome outer tube, and a radome cover cap.

[0038] The upper metal cylinder, the upper conical part, the lower metal cylinder, the lower conical part and the middle metal cylinder constitute the main body of the dipole antenna.

[0039] The dielectric support block, dielectric support tube and dielectric ring mainly play the role of dielectric support.

[0040] The radome outer tube and the radome cover cap form the radome, and the dipole antenna is placed inside the radome.

[0041] The upper metal cylinder and the lower metal cylinder are placed in parallel, on a straight line, are hollow, and have the same diameter and length.

[0042] The upper conical part and the lower conical part are stepped hollow cones, and the upper conical part and the lower conical part are respectively connected to the upper metal cylinder and the lower metal cylinder; the middle metal cylinder is also hollow, with the same diameter as the upper metal cylinder and the lower metal cylinder, and is located in the middle position of the dipole antenna, and the outer surface does not contact the upper metal cylinder and the lower metal cylinder.

[0043] Solder-free feeding method: The customized cable assembly passes through the lower metal cylinder and the interior of the lower cone, and the metal outer threaded metal parts of the customized cable assembly's 50Ω coaxial feeder are inserted into the threaded holes of the lower cone through threaded buckles for fixed contact; the inner core of the 50Ω coaxial feeder of the customized cable assembly is inserted into the end of the upper cone through an SMP-type plug for fixed contact with it, thereby achieving solder-free feeding of the antenna. The customized cable assembly can be in cable form or connector form.

[0044] The middle metal cylinder is used for impedance matching, and its length is used to adjust the voltage standing wave ratio of the antenna to achieve optimal impedance matching.

[0045] The antenna cover is made of a hollow cylindrical fiberglass reinforced plastic material, and can also be a cylindrical or other shaped dielectric cover.

[0046] The working process of the overall solder-free assembly of the antenna is as follows:

[0047] The first step is to pass the customized cable assembly 6 through the lower end of the base 7, and the bottom of the customized cable assembly 6 is fixed to the base 7 by screws; the second step is to pass the dielectric support block 8 through the top of the customized cable assembly 6 and make close contact with the base 7; the third step is to fix the lower metal cylinder 3 and the lower conical part 4 together through the metal connector 9, and pass it through the top of the customized cable assembly 6, and the bottom of the lower metal cylinder 3 is inserted into and seated on the top of the dielectric support block 8, making close contact with it, and the lower conical part 4, the lower metal cylinder 3, the dielectric support block 8 and the base 7 are firmly fixed through the threaded hole on the lower conical part 4 and the threaded metal part 6-2 on the customized cable assembly 6; the fourth step is to pass the dielectric support tube 10 through the top of the customized cable assembly 6 and make close contact with the lower conical part 4. The fifth step is to put the middle metal cylinder 5 on the dielectric support cylinder 10, and the two are in close contact; the sixth step is to put the dielectric ring 11 on the dielectric support cylinder 10 and make contact with the middle metal cylinder 5; the seventh step is to fix the upper metal cylinder 1 and the upper cone 2 together through the metal connector 9, and pass it through the top of the custom cable assembly 6 so that the SMP plug of the custom cable assembly 6 is inserted into the end of the upper cone 2 and makes contact with the dielectric ring 11, and fix it with screws; the eighth step is to install the antenna cover outer cylinder from top to bottom and fix it with the base 7 through threads; the ninth step is to install the antenna cover cap 13 on the top, making contact with the upper metal cylinder 1. Finally, the antenna cover cap 13 is coated with epoxy resin to form a sealed antenna cover with the antenna cover outer cylinder 12. Figure 1 shown.

[0048] To sum up: In this technical solution, the principle and structure of the solderless feeding and assembly of the antenna are simple and reliable. The effective cooperation between the SMP-type plug 6-1 and the threaded metal part 6-2 on the customized cable assembly 6 and the ends of the upper cone 2 and the lower cone 4 is utilized to realize the solderless feeding function of the antenna, and it can be highly organically integrated with various platforms, significantly improving the assembly efficiency level of the equipment. It has broad application prospects in the fields of information communication and countermeasures, especially in military fields such as special communications.

[0049] The following is a more specific embodiment:

[0050] Reference Figures 1 to 9 This embodiment includes an upper metal cylinder 1, an upper conical part 2, a lower metal cylinder 3, a lower conical part 4, a middle metal cylinder 5, a customized cable assembly 6, a base 7, a dielectric support block 8, a metal connector 9, a dielectric support tube 10, a dielectric ring 11, an antenna cover outer tube 12, and an antenna cover cap 13.

[0051] The customized cable assembly 6 includes an SMP type plug 6-1, a threaded metal part 6-2, and a metal stopper 6-3. Figure 4 shown.

[0052] The upper metal cylinder 1, the upper conical member 2, the lower metal cylinder 3, the lower conical member 4 and the middle metal cylinder 5 constitute the main structural part of the dipole antenna.

[0053] The dielectric support block 8, dielectric support tube 10 and dielectric ring 11 mainly play the role of dielectric support.

[0054] The radome outer tube 12 and the radome cover 13 form a radome, and the dipole antenna is placed inside the radome.

[0055] The base 7 is mounted on the bottom of the radome outer tube 12 . The bottom of the radome outer tube 12 is threaded. The base 7 is fixed to the radome outer tube 12 through threaded holes and screws.

[0056] The dielectric support block 8 has a small hole in the center for passing the customized cable assembly 6. The dielectric support block 8 can be stuck in the base 7 to fix and support the lower metal cylinder 3. Figure 7 shown.

[0057] The metal outer threaded metal part 6-2 of the 50Ω coaxial feeder of the customized cable assembly 6 is inserted into the threaded hole at the end of the lower tapered part 4 through the threaded buckle and is fixedly contacted with it; the inner core of the 50Ω coaxial feeder of the customized cable assembly 6 is inserted into the end of the upper tapered part 2 through the SMP type plug 6-1 and is fixedly contacted with it, as shown in FIG. Figure 1 and Figure 4 shown.

[0058] Figure 1 This is a structural diagram of a welding-free octave broadband omnidirectional antenna of the present invention. The present invention proposes a structural diagram of a welding-free octave broadband omnidirectional antenna, including an upper metal cylinder 1, an upper conical part 2, a lower metal cylinder 3, a lower conical part 4, a middle metal cylinder 5, a customized cable assembly 6, a base 7, a dielectric support block 8, a metal connector 9, a dielectric support tube 10, a dielectric ring 11, an antenna cover outer tube 12, and an antenna cover cap 13.

[0059] In this embodiment, if Figure 2 and Figure 3 They are schematic structural diagrams of the upper conical part 2 and the lower conical part 4, both of which are made of metal, with a maximum diameter of 28 mm, a minimum diameter of 10 mm, a length of 36.9 mm, a stepped appearance, and a hollow interior.

[0060] In this embodiment, the upper metal cylinder 1 and the lower metal cylinder 3 are both made of metal, with a wall thickness of 1 mm and a length of 110 mm, which is slightly less than a quarter wavelength of the high frequency.

[0061] In this embodiment, the middle metal cylinder 5 is made of metal, has a wall thickness of 1 mm and a length of 63 mm. The middle metal cylinder 5 is nested on the dielectric support cylinder 10 and does not contact the upper metal cylinder 1 and the lower metal cylinder 3. It is mainly used for impedance matching. The voltage standing wave ratio of the antenna is adjusted by its length to achieve optimal impedance matching.

[0062] In this embodiment, if Figure 5 and Figure 6 The following are schematic diagrams of the dielectric support tube 10 and dielectric ring 11, both made of nylon. The dielectric support tube 10 has a maximum diameter of 30 mm, a minimum diameter of 25 mm, and a length of 80.6 mm. It has a stepped appearance and a hollow interior. The dielectric ring 11 has a maximum diameter of 30 mm, a minimum diameter of 25 mm, and a length of 8.8 mm. It is annular and works in conjunction with the dielectric support tube 10 to secure and nest the middle metal cylinder 5.

[0063] In this embodiment, if Figure 7 This is a schematic diagram of the structure of dielectric support block 8. Made of nylon, dielectric support block 8 has a maximum diameter of 33mm, a minimum diameter of 28mm, and a length of 20.2mm. It has a serrated appearance and is hollow inside. Dielectric support block 8 fits snugly inside base 7, primarily securing and supporting the underlying metal cylinder 3.

[0064] In this embodiment, if Figure 8 and Figure 9 This is a diagram of the structure and size parameters of the base 7, which is made of metal and has mounting holes on it, mainly used for external structural connection.

[0065] In this embodiment, the wire cover outer tube 12 is made of fiberglass, has a wall thickness of 2 mm, a length of 318 mm, and a diameter of 44 mm. Its upper end is connected to the antenna cover cap 13, and its lower end is connected to the base 7 through metal screws.

[0066] In this embodiment, the lengths of the upper metal cylinder 1 and the lower metal cylinder 3 are related to the impedance and standing wave of the antenna device, and can be adjusted by parameter optimization. The obtained voltage standing wave ratio is shown in the figure below. Figure 10 It can be seen that the VSWR of the antenna is less than 2.0 in the frequency bandwidth of 330MHz to 660MHz, and the bandwidth reaches an octave, realizing a broadband design.

[0067] In this embodiment, see Figure 11 , which are the directional patterns of the antenna at 330MHz, 360MHz, 580MHz, and 660MHz. It can be seen that the operating frequency coverage range of the antenna is 330MHz to 660MHz, and the gain in the entire bandwidth is greater than 2.0dBi. The directional pattern can achieve good omnidirectional characteristics within the bandwidth.

[0068] It is worth mentioning that in the above embodiment, if the diameter of the antenna dipole becomes larger, the working bandwidth of the antenna will also become wider.

[0069] The working process of the overall solder-free assembly of the antenna is as follows:

[0070] The first step is to pass the customized cable assembly 6 through the lower end of the base 7, and the bottom of the customized cable assembly 6 is fixed to the base 7 by screws; the second step is to pass the dielectric support block 8 through the top of the customized cable assembly 6 and make close contact with the base 7; the third step is to fix the lower metal cylinder 3 and the lower conical member 4 together through the metal connector 9, and pass it through the top of the customized cable assembly 6, and the bottom of the lower metal cylinder 3 is inserted into and seated on the top of the dielectric support block 8, making close contact with it, and the lower conical member 4, the lower metal cylinder 3, the dielectric support block 8 and the base 7 are firmly fixed through the threaded hole on the lower conical member 4 and the threaded metal member 6-2 on the customized cable assembly 6; the fourth step is to pass the dielectric support tube 10 through the top of the customized cable assembly 6 and make close contact with the lower conical member 4 Tightly contact with screws; Step 5, put the middle metal cylinder 5 on the dielectric support cylinder 10, and the two are in close contact; Step 6, put the dielectric ring 11 on the dielectric support cylinder 10, and make contact with the middle metal cylinder 5; Step 7, fix the upper metal cylinder 1 and the upper cone 2 together through the metal connector 9, pass it through the top of the custom cable assembly 6, so that the SMP plug of the custom cable assembly 6 is inserted into the end of the upper cone 2 and makes contact with the dielectric ring 11, and fix it with screws; Step 8, install the antenna cover outer cylinder from top to bottom and fix it with the base 7 through threads; Step 9, install the antenna cover cap 13 at the top, making contact with the upper metal cylinder 1, and finally coat the antenna cover cap 13 with epoxy resin to form a sealed antenna cover with the antenna cover outer cylinder. Figure 1 shown.

[0071] Some of the techniques not described in detail in the present invention belong to those skilled in the art.

[0072] The above are only preferred embodiments of the present invention, which are intended to further illustrate the present invention rather than to limit it. Any simple replacement based on the contents disclosed in the above text and drawings is within the scope of protection of this patent.

Claims

1. A welding-free octave-band broadband omnidirectional antenna, comprising a radome outer tube (12), characterized in that: The device also includes a dipole antenna, a dielectric support block (8) and a dielectric support tube (10) located inside the outer tube of the antenna cover; The dipole antenna comprises an upper metal cylinder (1), an upper conical member (2), a lower conical member (4) and a lower metal cylinder (3) arranged in sequence from top to bottom; the metal cylinder is a hollow cylindrical shape, and the conical member is a stepped hollow conical shape; the two conical members are symmetrically arranged, and the upper conical member (2) and the lower conical member are respectively connected to the upper metal cylinder and the lower metal cylinder; The dielectric support cylinder (10) is located between the upper conical member and the lower conical member, and its two ends are respectively connected to the corresponding conical members; a middle metal cylinder (5) is sleeved on the outer side of the dielectric straight cylinder, and the upper metal cylinder (1) and the lower metal cylinder do not contact the middle metal cylinder; The lower metal cylinder (3) is connected to the base (7) via a dielectric support block (8); the cable assembly (6) is installed on the lower surface of the base, and the SMP-type plug on the top thereof passes through the dielectric support block (8), the lower metal cylinder (3) and the lower conical member in sequence and is connected to the upper conical member.

2. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: One end of the upper tapered piece is connected to the upper metal cylinder, and the other end is provided with an SMP type card hole, which matches the SMP type plug end of the cable assembly.

3. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: One end of the lower conical part is connected to the lower metal cylinder, and the other end has a threaded buckle inside, which is used to match the threaded metal part of the customized cable assembly; the cable assembly passes through the interior of the lower metal cylinder and the lower conical part, and the outer conductor of the cable assembly is fixedly contacted with the lower conical part through the threaded buckle; the inner core of the cable assembly is inserted into the upper conical part through an SMP-type plug.

4. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: The top of the radome is provided with a radome cap, and the base serves as the bottom plate of the radome, and the three form a closed space; the radome is made of hollow cylindrical fiberglass.

5. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: The radome is threadedly connected to the base.

6. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: The SMP type plug is located at the end of the inner conductor of the cable assembly; the threaded metal part and the metal limiter are both installed on the cable assembly, the threaded metal part is connected to the outer conductor of the cable assembly, and the metal limiter is installed on one side of the threaded metal part.

7. The solder-free octave-band broadband omnidirectional antenna according to claim 1, characterized in that: It also includes two dielectric rings; the dielectric rings are both sleeved on the middle metal cylinder and used to clamp the middle metal cylinder on the dielectric support cylinder.

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