JP3301750B2 - 4-segment helical antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-segment helical antenna in which a spiral conductor pattern is accurately and easily manufactured on a cylindrical or multistage cylindrical base by photoetching technology. The present invention relates to a four-segment helical antenna capable of preventing a decrease in gain and a deterioration in directivity due to the influence of a reflected wave from a metal base or the like supporting an antenna element.

[0002]

2. Description of the Related Art As an antenna used in a communication system using a geostationary satellite or an orbiting satellite or the like, a four-segment helical antenna has been attracting attention and has been widely used. FIG. 11 is a sectional view showing an example of a conventional four-segment helical antenna used in such a system. The four-segment helical antenna shown in this figure is disposed in a radome 102 attached to a base 101, and a balun 103 attached on the base 101.
And an antenna body 10 provided on the balun 103.
4 and the balun 10 provided below the base 101.
3 is connected to the hybrid circuit (HYB) 105. The antenna body has a mylar member 106 formed in a cylindrical shape as shown in FIG.
06, two antenna elements 107 and 108 wound spirally around the outer periphery of the balun 10.
3 are connected to four terminals. The balun 103 includes the hybrid circuit 105 and the antenna elements 1
The lower end is connected to the hybrid circuit 105 by a coaxial cable or the like penetrating the base 101. The hybrid circuit 105 derives two signals whose phases are shifted from each other by a predetermined angle with respect to signals input and output from a transceiver arranged in the aircraft and supplies the signals to the balun 103. And a process of combining the two received signals output through the interface and supplying the combined signal to the transceiver.

However, the above-mentioned cylindrical four-segment helical antenna has a relatively narrow applicable frequency band as shown in FIGS. 13 (b) and 13 (c), and is used for simultaneous transmission and reception using the same antenna. However, it was difficult to cope with a signal frequency separated by a desired frequency. That is, FIG.
(a), (b), and (c) show the specific dimensions of a conventional single-column four-segment helical antenna and the standing wave ratio (SWR) of the balun viewed from the two input ends of the antenna. This is the result. In this example, the dimensions of the mylar portion are determined as shown in FIG. 7A, and the antenna pattern (the conductor pattern on the peripheral surface of the mylar portion) is used so that 1.53 GHz to 1.56 GHz and 1.63 GHz to 1.66 GHz can be used. ) Is formed. Ideally, the SWRs seen from each of the two input terminals of the balun should have the same characteristics, but generally differ slightly due to manufacturing errors, non-uniform materials, and the like. The overall characteristics of an antenna greatly depend on the above-mentioned SWR, and the limit value of a practically usable SWR is generally 1.
5 (below). From this point of view, in the conventional antenna shown in FIGS.
In 2.2, the SWR is 2.2, and in (c), the SW of 1.63 GHz
R deviates from the desired value of 1.8, indicating that it cannot be put to practical use as it is. As described above, the frequency band of the conventional four-segment helical antenna is generally narrow.

In manufacturing an antenna pattern spirally provided on the peripheral surface of a cylinder or column, a copper foil or the like is cut into a narrow band (ribbon) on a mylar member 106 conventionally formed in a column. The antenna body 1 is formed by using a method of spirally winding the antenna elements 107 and 108 or the like.
Since the 04 was created, it was troublesome to create it, which hindered a reduction in production cost. Further, such a pattern forming method is a complicated operation in which the skill of the operator directly affects the dimensional accuracy of the antenna main body 104, so it is not suitable for mass production, or it is difficult to make the dimensional accuracy uniform. For this reason, the yield of the product is poor, and further, the appearance is deteriorated, and the product value is lowered. Therefore, in order to solve such a problem, a mylar member 1 formed in a columnar shape is used.
It is also conceivable to attach a copper foil on the substrate 06 and etch it. However, it is difficult to form a precise pattern on a curved surface by the current etching technology including the masking technology. In particular, a base (comprising Teflon, plastic, etc.) in which an upper cylindrical portion having a different diameter, such as a four-segment helical antenna according to the present invention described below, and a lower cylindrical portion connected via a tapered portion.
In the case of an antenna in which a four-segment winding antenna pattern is formed on the peripheral surface, the pattern forming operation is more difficult.

[0005] Next, when the four-segment helical antenna is mounted on the body 100 of an aircraft as shown in FIG. 14, the vertical gain of the radiation pattern becomes small as shown in FIG. Moreover, there is a possibility that the directivity characteristics of the entire antenna may be deteriorated. That is, in the radiation pattern shown in the figure, the gain changes with a change in direction. Here, for the sake of simplicity, the maximum value of the gain in the direction is indicated by the outer line, and the minimum value of the gain is indicated by the inner line. Shown by a line. In the gain shown in this figure, the fluctuation width between the inner radiation pattern P1 which is a line connecting the minimum values and the outer radiation pattern P2 which is a line connecting the maximum values of the gains in each direction is large. The overall antenna gain is smaller. It is considered that the cause of the characteristic deterioration is that a part of the radio wave emitted by the antenna main body 104 is reflected by the metal base 101 or the body 100 as shown in FIG. Also,
If radio waves from antenna elements are mixed into a hybrid circuit or balun, these circuits may not function properly, resulting in a decrease in SWR and antenna efficiency, resulting in deterioration of directional characteristics. Become.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent a radio wave from an antenna body from being reflected by an antenna base or an airframe even when a four-segment helical antenna is mounted on an aircraft or the like, thereby improving a radiation pattern. It is an object of the present invention to provide a four-segment helical antenna having a shape close to an ideal and capable of preventing a decrease in directivity.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is to provide a method in which a four-segment helical antenna element and a control circuit connected below the four-segment helical antenna element are provided with a metal. A shield plate formed by laminating a radio wave absorber layer is disposed on an upper surface of the plate, and a lower portion of the 4-segment helical antenna element is supported on the upper surface of the shield plate.
The invention according to claim 2 is characterized in that the four-segment helical antenna element is formed by connecting a plurality of cylindrical bodies having different diameters coaxially and in multiple stages, and forming a conductor pattern on the peripheral surface thereof. I do. The invention according to claim 3 is characterized in that the four-segment helical antenna element has a tapered portion connecting a peripheral surface to a connecting portion of the plurality of cylindrical bodies. According to a fourth aspect of the present invention, the four-segment helical antenna element has a tapered portion formed by cutting off a corner of a tip portion thereof. The invention according to claim 5 is characterized in that the metal plate constituting the shield plate is made of an aluminum or copper substrate, and the radio wave absorber layer is a ferrite layer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a perspective external view showing a first embodiment of a four-segment helical antenna according to the present invention. In the example shown in this figure, a first cylindrical portion 2 having a tapered portion 1 formed by cutting off a corner of a distal end portion, a second cylindrical portion 3 having a diameter larger than the cylindrical portion 2, and these two cylindrical portions 2, 3 is connected to a second tapered portion 4 on the peripheral surface of a mylar member (multi-stage cylindrical body) 5 having the same central axis.
Four conductor patterns 6 spirally like the conventional antenna
Is formed. The features of this embodiment are that two cylindrical portions having different diameters are arranged coaxially and in a vertical positional relationship, and that a tip portion and a tapered portion are provided at the connecting portion between the two cylindrical portions. However, it is possible to increase the bandwidth as compared with the conventional antenna. FIGS. 2A, 2B, and 2C are diagrams showing the measurement results of the first embodiment of the present invention. The upper and lower two cylindrical portions 2 having the shape shown in FIG.
In addition to setting the diameter of each of No. 3 to 20 (mm) and 25 (mm), other dimensions were set as shown in FIG.
The characteristics of the VSWR seen from the two input terminals of the balun of the four-segment helical antenna manufactured with other dimensions determined so that the SWR of 1.56 GHz and 1.63 GHz to 1.66 GHz are 1.5 or less. It is shown. By comparing this figure with the conventional characteristic diagrams of FIGS. 13B and 13C, the effect of improving the characteristics in the present embodiment will be apparent.
That is, in this antenna, in all of FIGS. 2B and 2C, the SWR is 1.5 or less in the desired frequency range. The improvement effect described above is not limited to the shape shown in FIG. For example, FIG. 3 (a) shows an antenna in which the required width is tapered only at the tip, and its characteristics are as shown in (b) and (c). At the highest frequency in FIG. Although there is, it is improved than the conventional one. FIG. 4 (a)
Is an antenna having a shape in which the taper width of the tip portion is increased. In this case, the characteristics shown in FIGS. 4B and 4C are almost the same as in FIG.

FIG. 5 (a) shows that a single cylinder or a cylinder is slightly tapered as a whole. Due to this shape, as shown in FIGS. Characteristic improvement is recognized. The two characteristics shown in (b) and (c) of FIGS. 3, 4 and 5 respectively show the antenna side from each of the two input terminals of the balun connected to the antenna as in the case of FIG. FIG. 9 is a SWR characteristic diagram when the illuminating device is turned on. FIG. 6 shows the gain and the axial ratio characteristics in each embodiment of the four-segment helical antenna of the present invention described above for reference. The characteristics of the conventional single columnar antenna shown in FIGS. 12 and 13 are also shown for easy comparison with the conventional antenna. As is clear from the figure, a significant improvement is also observed in the gain. In the above embodiment, a case where two cylinders or cylinders having different diameters are connected is shown. However, the present invention is not limited to this example, and three or more cylinders or cylinders having different diameters are sequentially formed in the same manner. It is also possible to connect them, or to connect those shown in FIGS. 4 and 5 in multiple stages. Further, other dimensions of the specific numerical values shown in the figure differ depending on the material (dielectric constant and the like) of the antenna base used, and may be appropriately determined so as to tune at a desired frequency.

Next, a method for forming a conductor pattern on the peripheral surface of a cylinder or a cylinder including the above-described four-segment helical antenna will be described in detail. FIG. 7 is an explanatory view of a mask used for carrying out the method of the present invention and a pattern forming method using the mask. The multi-stage cylindrical body made of Teflon whose outer diameter shown in FIG. A case where a spiral antenna pattern is formed on the outer peripheral surface of (antenna base) 61 using a mask 64 is shown. The mask 64 is formed of a bag 65 having an inner surface shape that closely matches the outer peripheral surface of the multi-stage cylindrical body 61. The bag 65 is made of, for example, a transparent and thin resin sheet. The large-diameter bottom surface of the bag body 65 is left open, and the mask mounting is completed only by covering from above the multi-stage cylindrical body 61 as shown in the figure. The bag body 65 has a ground portion 66 formed in a non-transparent shape, and a plurality of transparent portions 67 having a shape corresponding to the antenna pattern to be formed on the outer peripheral surface of the multi-stage cylindrical body 61 are spirally formed on the peripheral surface thereof. It is formed in a shape. When an intersection of the antenna pattern is formed on the top surface of the cylindrical body, it is of course necessary to form a transparent portion 67b corresponding to the shape on the mask top surface corresponding to this portion. One pattern is cut in advance so that the pattern does not touch. Further, the bag body 65 used in the present invention only needs to open at least the lower end in the axial direction, and it does not matter whether or not the upper end in the axial direction is open. The step of depositing a pattern using the mask 64 having the above configuration will be described. First, the surface of the multi-stage cylindrical body 61 made of Teflon is processed into a rough surface using a chemical, and then a metal layer is formed by vapor deposition, plating, or the like. A uniform layer is formed, and a photosensitive agent is uniformly applied on the metal layer in a dark room. Subsequently, a mask 64 is placed over and adhered to the cylindrical body 1 to which the photosensitive agent has been applied. The reason for processing the surface of the multi-stage cylindrical body made of Teflon into a rough surface is to enhance the adhesion to the metal deposited or plated. Next, when the exposure light is uniformly irradiated while rotating the masked multi-stage cylindrical body 61, the photosensitive agent located in the transparent portion 67 having a shape corresponding to the antenna pattern is exposed to light and solidified. During exposure, without rotating the multi-stage cylindrical body,
The exposure light may be emitted from all directions of the fixed multi-stage cylindrical body. Subsequently, the mask 64 is removed, and the unexposed portion of the photosensitive agent is removed by using hypo (sodium thiosulfate) or the like. Then, the metal film located below the removed unexposed portion of the photosensitive agent is removed by an etchant. I do. Finally, the antenna pattern can be obtained by washing the solidified photosensitive agent.

If etching is performed according to this procedure, pattern formation on the multi-stage cylindrical body can be easily and accurately realized, so that mass production is possible and cost can be reduced. Note that the etching method using the mask is particularly effective when applied to pattern formation on a multi-stage cylindrical body, and the above-described etching operation can be easily performed by creating a bag-shaped mask that is in close contact with the shape of the outer peripheral surface. Becomes possible. Therefore, in the claims, the cylindrical body is a concept including a multistage cylindrical body, a polygonal pillar, a conical body, and other cubes in addition to the cylindrical body. As a procedure for manufacturing the bag-shaped mask, a resin sheet in an unfolded state having a non-transparent portion 66 and a transparent portion 67 corresponding to an antenna pattern is cut into a required shape in advance, and this sheet is It is preferable to form the bag 65 by rolling it into a roll. As for the tapered portion of the multi-stage cylinder, a bag having a desired shape can be relatively easily obtained by heating and molding the above bag with a mold having the same shape as the workpiece. As described above, according to the four-segment helical antenna according to the first embodiment of the present invention, the adaptive frequency band can be expanded. For example, simultaneous transmission / reception communication using a channel frequency separated by a required frequency can be performed. This is effective when performing with one antenna. Further, according to the manufacturing method of the present invention, the required conductor pattern can be accurately formed on the peripheral surface of a general cylinder or a cylinder, particularly on the peripheral surface of a multi-stage cylindrical body having a different thickness. This is effective in mass-producing a four-segment helical antenna.

FIG. 8 is a sectional view showing a second embodiment of the present invention, and FIG. 9 is an external perspective view thereof. The four-segment helical antenna device shown in FIG. 1 is designed on the assumption that it is fixed to an airframe (antenna mounting target surface) 71 of an aircraft or the like.
A shield plate 74 supported by the upper end of a support column 73 erected on the base 72; an antenna body (antenna element) 75 fixed on the shield plate 74;
A hybrid circuit (HYB) 76 and a matching circuit 77 connected to the antenna elements 81 and 82 via a balun (not shown) are provided below the base 4 on the base 72. Antenna body (antenna element) 75
Comprises a mylar member 80 and two narrow strip-shaped antenna elements 81 and 82 spirally wound around the mylar member 80.
The lower ends of 1 and 82 are connected to a matching circuit 77 via a balun (not shown) and semi-rigid cables 83 and 84. The shape of the antenna body 75 may be the type shown in FIGS. 1 and 2 (a) as shown, or may be the shape shown in FIGS. 3 (a), 4 (a), and 5 (a). The shape shown in a) may be used. Further, FIG. 12 and FIG.
The conventional straight-type antenna element shown in FIG. The shield plate 74 includes, for example, an aluminum substrate 85 and a radio wave absorber layer 86 such as a ferrite layer laminated on the upper surface of the aluminum substrate 85. As described above, the shield plate 74 is disposed between the antenna main body 75 and the control circuits such as the hybrid circuit 76 and the matching circuit 77, and the radio wave radiated from the antenna main body to the body 71 or the base 72 near the antenna is transmitted. Since the electromagnetic wave is absorbed by the radio wave absorber layer 86, the adverse effect of the reflected radio wave on the radiation characteristics of the antenna can be reduced. Also,
By using a conductive substrate 85 of aluminum or the like, it is also possible to obtain an electric field shielding effect between the antenna body and control circuits such as a hybrid circuit and a matching circuit.

FIG. 10 is a diagram showing the vertical gain of the radiation pattern of the radio wave radiated from the four-segment helical antenna according to the embodiment of the present invention, wherein the lines connecting the minimum values of the gain in each direction are shown. Inner radiation pattern P1 '
15 and the outer radiation pattern P2 ′, which is a line connecting the maximum values of the gains in the respective directions, is smaller, and the entire shape of the radiation pattern is circular due to the circular shape as compared with the case of FIG. It can be seen that the radiation characteristics of the antenna are improved, and the radiation characteristics of the antenna are improved. When a transmission signal is output from the transceiver, the hybrid circuit 7
6, two transmission signals whose phases are shifted by a predetermined angle from this transmission signal are output.
When two received signals are input to 6, the received signals are combined and supplied to the transceiver. A balun (not shown) is a part that converts the balance / unbalance between the hybrid circuit 76 and the antenna body 75.
As described above, when radio waves from the antenna body enter the hybrid circuit 76 and the like, these circuits may not function properly. As a result, the SWR and the antenna efficiency may be reduced, and the directional characteristics may be deteriorated. In the second embodiment of the present invention, the antenna body 7
Since the shield plate 74 is interposed between the circuit board 5 and the circuits 75 and 76, radio waves radiated toward the base or the airframe are absorbed by the shield plate, thereby preventing the above-mentioned problems from occurring. As described above, in the second embodiment of the present invention, the deterioration of the radiation characteristic caused by the reflection of a part of the radio wave radiated from the antenna main body to the base or the body of the antenna or the radio wave Can be prevented from being caused by a part of the control signal being mixed into a control circuit located below the antenna body.

[0014]

As described above, according to the present invention, even when a four-segment helical antenna is mounted on an aircraft or the like, radio waves from the antenna main body are prevented from being reflected by the antenna base or the airframe. It is possible to make the radiation pattern a shape closer to the ideal, and to prevent a decrease in the directivity characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective external view showing an embodiment of a four-segment helical antenna according to the present invention.

FIGS. 2 (a), (b) and (c) are diagrams showing actual measurement results of a specific example of the present invention.

FIGS. 3 (a), (b), and (c) are a diagram showing a configuration diagram and characteristics of an antenna in which a taper having a required width is formed only at a distal end portion.

4 (a), (b) and (c) are a diagram showing a configuration and characteristics of an antenna having a shape in which a taper length at a distal end portion is increased.

FIGS. 5 (a), (b) and (c) are a diagram showing a configuration and characteristics of an antenna in which a single cylinder or a cylinder is slightly tapered as a whole.

FIG. 6 is a diagram illustrating gain and axial ratio characteristics in each example of the four-segment helical antenna according to the present invention.

FIG. 7 is an explanatory view of a mask used for carrying out the method of the present invention and a pattern forming method by vapor deposition or the like using the mask.

FIG. 8 is a sectional view showing one embodiment of a four-segment helical antenna according to the present invention.

9 is an external perspective view of the four-segment helical antenna shown in FIG.

FIG. 10 is a diagram illustrating radiation characteristics of the four-segment helical antenna illustrated in FIG. 8;

FIG. 11 is a cross-sectional view showing an example of a conventional 4-segment helical antenna.

FIG. 12 is an explanatory diagram of a configuration of a conventional 4-segment helical antenna.

FIGS. 13 (a), (b) and (c) show specific dimensions of a conventional single-column four-segment helical antenna and the standing wave ratio when the antenna side is viewed from each of two input ends of the balun (FIG. FIG. 4 is a diagram showing the result of measuring SWR).

FIG. 14 is a cross-sectional view showing an example of a conventionally known four-segment helical antenna.

FIG. 15 is a schematic diagram showing an example of a radiation pattern of the four-segment helical antenna of FIG. 14;

[Explanation of symbols]

1 taper portion, 2 first column portion, 3 second column portion,
4 Second tapered portion, 5 Mylar member, 6 Conductor pattern, 61 Multi-stage cylindrical body, 64 Mask, 65 bag, 6
6 Ground part, 67 Transparent part, 71 Airframe of an aircraft or the like (surface to which antenna is attached), 72 Base, 73 prop, 74 Shield plate, 75 Antenna body, 76 Hybrid circuit (HYB), 77 Matching circuit, 81, 8
2 antenna element, 83, 84 semi-rigid cable, 85 aluminum substrate, 86 radio wave absorber layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01Q 1/52 H01Q 1/52 5/00 5/00 17/00 17/00 21/24 21/24 (56) References Japanese Utility Model Application No. 55-64443 (JP, A) Japanese Utility Model Application No. Sho 61-42112 (JP, U) U.S. Pat. No. 4,169,267 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01Q 11/08 H01Q 1/00-1/52 H01Q 17/00 H01Q 21/24

Claims (5)

(57) [Claims] 1. A shield formed by laminating a radio wave absorber layer on an upper surface of a metal plate between a four-segment helical antenna element and a control circuit connected below the four-segment helical antenna element. A four-segment helical antenna, wherein a plate is arranged and a lower part of a four-segment helical antenna element is supported on an upper surface of the shield plate. 2. The four-segment helical antenna element is formed by connecting a plurality of cylindrical bodies having different diameters coaxially and in multiple stages, and forming a conductor pattern on a peripheral surface thereof. Item 4. A four-segment helical antenna according to item 1. 3. A four-segment winding according to claim 2, wherein the four-segment winding helical antenna element has a tapered portion connecting a peripheral surface to a connecting portion of the plurality of cylindrical bodies. Helical antenna. 4. A four-segment winding helical antenna according to claim 2, wherein the four-segment winding helical antenna element has a tapered portion formed by cutting off a corner of a tip part thereof. 5. The metal plate forming the shield plate is made of an aluminum or copper substrate, and the radio wave absorber layer is
5. The four-segment helical antenna according to claim 1, wherein the helical antenna is a ferrite layer.