RU2293406C2 - Antenna element and its manufacturing process - Google Patents

Abstract

FIELD: antenna engineering.

SUBSTANCE: hemispherical case of antenna element affording extended band of spiral antenna and its serviceability under impact of vibration loads and at temperatures ranging between -60 and +40 °C has wall thickness reducing from base to top and is manufactured by transfer molding method from epoxy molding material followed by making deepened pattern therein for disposing spiral radiator. Gradual variation of wall thickness from work zone in high-frequency band to that in low-frequency band ensures low VSWR level of broadband spiral antenna.

EFFECT: facilitated manufacture, ability of producing identical antenna elements.

3 cl, 2 dwg

Description

The present invention relates to radio engineering and can be used in antenna technology.

The antenna element, which is a hemispherical shaped dielectric casing, is designed for winding a spiral antenna emitter operating in a wide frequency band under the influence of climatic and mechanical factors.

The specified antenna element is the main part of the spiral antenna, which determines its broadband, strength characteristics and the ability to provide radio technical characteristics in operating conditions.

The most important parameters of the antenna element are: dielectric constant, hemisphere wall thickness and the main mechanical and climatic characteristics. In addition, the requirements for the identity of the manufacture of products are imposed on the materials of the antenna element and, if possible, be processed into a given shape without loss of material.

An antenna is known by the type of dielectric material used (patent H 01 Q 1/24 (11) WO 03073554 A1, published September 4, 2003), in which the dielectric core is made of epoxy resin and then emitters are applied to it on a plastic film deposited on top of layer of resin. The disadvantage of an epoxy resin without a filler is brittleness under mechanical stress and insufficient heat resistance. In addition, the presented antenna is narrowband.

Closest to the invention is a spiral antenna of the Transit satellite (Reznikov GB, Aerials of aircraft. - M., Soviet Radio, 1967, p. 355-358). A ball-shaped satellite employs one slotted logarithmic spiral antenna. It consists of two hemispherical slot emitters, each of which is a two-way logarithmic spiral. Slots are cut in the metal shell of the satellite. The satellite’s large dimensions (⌀ 90 cm) make it possible to use the slotted version of a spiral antenna operating in the meter wavelength range (~ 135 MHz). However, in the decimeter and centimeter wave ranges, it is more technologically advanced to use a hemispherical dielectric casing, onto which spiral wire radiators are wound. In this case, the choice of dielectric material and the profile of the wall of the housing requires experimental testing.

The aim of the invention is to increase the frequency broadband of the spiral antenna, as well as ensuring its operability when exposed to vibrational loads in the temperature range of 60 ° C- + 140 ° C, along with improving the manufacturability and identity of the manufacture of dielectric housings.

This goal is achieved by the fact that the hemispherical dielectric housing for a broadband helical antenna is made by injection molding of an epoxy press material having a relatively high dielectric constant. The wall of the dielectric housing is profiled so that in the region of higher frequencies the wall thickness is as thin as possible, but still structurally strong. A smooth change in the wall thickness of the body from the working area in the high frequency region to the working area in the low frequency region provides a low level of VSWR (standing wave voltage coefficient) of a broadband helical antenna.

Figure 1 shows the shape of a hemispherical dielectric casing in the form of a shell having the same thickness. An in-depth pattern is formed mechanically on the outer surface of the housing, in which a spiral antenna emitter is placed.

Figure 2 shows the shape of the inventive hemispherical dielectric housing with a variable wall thickness of an epoxy press material. An in-depth pattern is formed mechanically on the outer surface of the housing, in which a spiral antenna emitter is placed.

The finished press material contains epoxy resin, the filler is micro glass fiber and an accelerator. The press material has good mechanical properties and operating temperature - 60 ° С- + 180 ° С, low water absorption of 0.02%, low coefficient of thermal linear expansion, dielectric constant 4.2-4.45, shrinkage during casting (less than 0, four%). This press material made it possible to manufacture an antenna element for a broadband spiral antenna with an accuracy of 12 degrees. The outer and inner diametrical dimensions of the cases are provided by the mold. An in-depth pattern is formed mechanically on the outer surface of the housing, in which a spiral radiator of a broadband antenna is placed.

Typically, antennas operating in a wide frequency band use materials with a low dielectric constant.

For the experimental work, materials with a low dielectric constant were selected: polyphenylene oxide Arylox 2101, Niplon - 2/3, polysulfone PSF-150-1 and an epoxy press material with a relatively high dielectric constant.

The main properties of the investigated materials are shown in table 1.

Table 1 Indicator Units Arylox 2101 Niplon-2/3 Polysulfone PSF-150-1 Epoxy press material 1. Density kg / m ³ 1060 1380 2200 1670-1710 2. Operating temperature ° C from -60 to +150 from -60 to +250 from -60 to +150 from -60 to +180 3. Impact strength KJ / m ² thirty - 100-125 twenty 4. Breaking stress 60 60-80 72 100-200 - in tension MPa 150-170 - during compression 180-230 - when bending 5. Brinell hardness MPa - 220 1028 200 6. The coefficient of thermal linear expansion ° C ^-1 5.2 × 10 ^-5 3.3 × 10 ^-5 5.2 × 10 ^-5 1.3 × 10 ^-5 7. The dielectric constant at a frequency of 10 Hz - 2.5-2.6 3.5 ± 0.1 2.6-2.8 4.2-4.45 8. The tangent of the dielectric loss angle at a frequency of 10 ⁶ Hz - (4-8) × 10 ^-4 (3,5-5) × 10 ^-3 8 × 10 ^-3 2 × 10 ^-2 9. Electric strength MV / m eighteen eighteen 17-20 thirty 10. Water absorption in 24 hours % 0.02-0.04 0,1-0,11 0.4 0.02 11. Shrinkage % 1.3 - 0.7 0.4 12. The method and temperature of processing ° C Injection molding 320-340 Injection molding 320-350 Injection molding 300-350 Injection molding 140-150

As can be seen from the table, the materials selected for the experiments have good mechanical characteristics, a wide range of operating temperatures, have low water absorption, low coefficient of thermal linear expansion, and the ability to be processed into a given shape without loss of material.

In Fig. 1, hemispherical dielectric housings were made from the above materials, in the grooves of which spiral antenna emitters were laid. Next, antenna blocks were assembled to test the PTX.

However, for antennas with hemispherical dielectric housings made of Arylox 2101 polyphenylene oxide, 2/3 Niplon, PSF-150-1 polysulfone, a decrease in the monotonicity of the radiation patterns and an increase in the level of the back lobes by 2–3 times (up to 18%) were noted. Also a disadvantage of these materials is the high temperature of processing into products.

For antennas with hemispherical dielectric housings made of epoxy press material, verification showed some slight change in radiation patterns. Experimental measurements of the dielectric constant of the epoxy press material in the microwave range showed its value equal to 4.2-4.45. Based on this, it was decided to profile the body wall so that in the region of higher frequencies the wall thickness was as thin as possible, but still structurally strong. A smooth change in the wall thickness of the casing from the working area in the high-frequency region to the working zone in the low-frequency region should provide acceptable radio-technical characteristics of a broadband antenna.

To verify the radio technical characteristics of FIG. 2, hemispherical dielectric bodies with a variable wall thickness were made of epoxy press material. An in-depth pattern was formed mechanically on the outer surface of the case, into which a spiral antenna emitter was placed. Antenna blocks were assembled and verified by RTX.

Experimental measurements on several samples of antennas confirmed the assumption made.

Thus, the dependence of the frequency broadband of a spiral antenna on the wall profile of a hemispherical dielectric body made of epoxy press material having a relatively high dielectric constant has been established and experimentally confirmed.

The radiation patterns of broadband helical antennas with a hemispherical dielectric body with a variable wall thickness of epoxy press material meet the technical requirements of the product.

The remaining parameters of the antennas (KU; KE; VSWR) also met the technical requirements for these antennas.

According to the method of manufacturing the inventive antenna element, the closest technical result achieved is the method of manufacturing a dimensionally stable product (patent H 01 Q 15/16 (11) RU 02230406 C2, published June 10, 2004), which consists in manufacturing the product in one cycle by the thermal compensation method in combination with vacuum molding. The disadvantage of this method is the use of composite materials having the ability to absorb electromagnetic waves, and high complexity.

The aim of the invention is to improve the manufacturability and identity of the manufacture of antenna elements.

This goal is achieved by the fact that the antenna elements are manufactured by injection molding (followed by heat treatment) on a mold, the geometric parameters of the working surface of which are repeated with the required accuracy the external and internal diametrical parameters of the antenna element, and the in-depth pattern, which houses the spiral radiator of the antenna, formed by mechanical means.

To manufacture the antenna housing from an epoxy press material, a mold was designed and manufactured that made it possible to manufacture parts by injection molding. The mold has one central gate, which is a truncated cone with ⌀ 4 mm at the apex and a cone angle of 8-10 °. The inlet gate is located in the center of the hemisphere, which ensures uniform filling of the heated material. To remove air and gases released from the polymer, “molds” are provided in the mold, which are located on the side opposite to the inlet gate. The thickness of the outlet is 0.1-0.15 with a width of 4-5 mm.

A portion of the press material is poured into the gate chamber.

Press Modes:

Press temperature, ° С - 140-150 Specific pressure, MPa - 25-30 Pressure exposure per 1 mm of the thickness of the part, min - 1.5-2 Heat treatment, ° С - 160 Time h - 8

Cases were made with an accuracy of 12 quality. The outer and inner diametrical dimensions of the hemispherical bodies are provided by the mold. An in-depth pattern is formed mechanically on the outer surface of the housing, in which a spiral antenna emitter is placed.

In order to determine the resistance of antennas to climatic and mechanical factors, antenna units were assembled and type tests were carried out:

1. Check the radio characteristics of the antennas under normal conditions for compliance with the technical specifications for the product.

2. Test for the effects of cyclic temperature changes from -60 ° C to + 85 ° C, a total of 3 cycles.

3. Test for exposure to low ambient temperature at -60 ° C - 2 hours.

4. Test for exposure to elevated ambient temperature:

a) at + 85 ° C - 2.5 hours; at + 140 ° С - 3 min;

b) at + 85 ° C - 1.0 hour; at + 100 ° С - 10 min.

5. Strength test when exposed to random broadband vibration.

6. Strength test when exposed to shock single action.

7. Strength test when exposed to multiple impacts.

Type tests and verification of VSWR (standing wave voltage coefficient) of broadband helical antennas wound on the inventive antenna element (hemispherical dielectric body with a variable wall thickness of an epoxy press material) are given in table 2.

Table 2. Name of test type VSWR antenna test parameter Checking antennas under normal conditions 1.8; 2.0 Cold resistance at -60 ° С - 2 h 1.8; 2.0 Cyclic temperature change at -60 ° С - + 85 ° С - 3 cycles 1.7; 2.15 Heat resistance at temperatures: + 85 ° С - 2 hours; + 140 ° C - 3 min 1.7; 2.06 SHSV at X, Y, Z (durability when exposed to random broadband vibration) 1.64; 2.2 Impact test 1.7; 2.2 Testing antennas after testing 1.7; 2.2

Thus, as confirmed by the results of experiments, the task was solved and the required technical result was achieved. The use of the inventive antenna element - a hemispherical dielectric body with a variable wall thickness of epoxy press material for a broadband spiral antenna - has increased its frequency broadband, as well as to ensure operability when exposed to vibrational loads in the temperature range of -60 ° С- + 140 ° С along with improving the manufacturability and identity of the manufacture of antenna elements.

Claims (3)

1. The antenna element, which is a hemispherical shaped dielectric housing for winding a spiral radiator of a broadband antenna, characterized in that it is made with a decrease in the thickness of the wall of the housing from the base to its top. 2. The antenna element according to claim 1, characterized in that it is made of an epoxy press material. 3. A method of manufacturing an antenna element by injection molding followed by heat treatment, characterized in that the antenna element is pressed onto a mold, the geometric parameters of the working surface of which are repeated with the required accuracy the outer and inner diametrical parameters of the antenna element case, and the in-depth drawing, in which houses the helical antenna radiator, is formed mechanically.

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