Housings for two duplexers installed in a dual polarized dual band antenna and method of assembling the same

Abstract

Housing for two duplexers installed in a dual polarized dual band antenna. The invention provides a housing for two frequency selective devices, comprising a split strip conductor arranged inside the housing, the split strip conductor forming a series section of a transmission line and an open stub in parallel to the series section, the housing comprising a piece of metal profile comprising two cavities; each cavity has a polygonal shape in cross section and comprises wide walls and narrow walls; the cavities comprise at least two regions in which the distance between the wide walls differs by at least 20% and one narrow wall is at least 20% shorter than the other narrow walls forming the cavity; the section of the split strip conductor forming the open stub is arranged in a region in which the distance between the wide walls is larger compared to the other regions; wherein the narrow walls comprise openings in which ends of the split strip conductor forming the ports of the frequency selective devices are arranged; wherein the cavities have a common wide wall comprising a step arranged at a boundary between regions having different distances between the wide walls of the regions.

Description

Technical Field

[0001] This invention relates to frequency selection devices, such as filters and duplexers, which consist of conductors disposed within a conductive housing. Background Technology

[0002] Many different designs of filters and other frequency selection devices have been developed to improve their frequency characteristics and reduce size. Stripline filters manufactured using conventional printed circuit board technology are inexpensive to produce, but their insertion loss is too high when the passband and stopband are separated by narrow frequency bands. Therefore, it is necessary to house the metal strip conductors within a conductive housing to reduce insertion loss. Passband filters comprising a main transmission line and an open stub connected in parallel with the main line are best suited for manufacturing because they can be produced by stamping. Patents US 5015976, US 5192297, and US 5291161 describe several improvements to such filters, but known designs cannot be used when the passband and stopband are separated by narrow frequency bands because the impedance of some of the striplines forming the open stub is too high, and the metal strips are too narrow to be produced by stamping. Therefore, filters providing passbands and stopbands separated by narrow frequency bands incorporate cavity resonators as described in many patent applications, such as US 3448412, US 6735766, EP2928011 A1, EP 3104452 A1, and EP 3179552 A1. The production cost of such filters is significantly higher than that of filters containing striplines because the fabrication of cavity resonators is more complex than that of striplines.

[0003] Because the modern wireless communication industry uses a large number of antennas for base stations, it is necessary to simplify the structure and reduce the production cost of duplexers. A duplexer provides a narrow boundary band between two passbands and is used as part of a dual-band antenna, which generates a beam with bipolar electromagnetic waves. Summary of the Invention

[0004] The object of this invention is to provide a housing for two frequency selection devices mounted within a base station antenna, providing a narrow boundary band between the passband and stopband. Simultaneously, the frequency selection devices offer low levels of passive intermodulation and low manufacturing costs.

[0005] The purpose of this invention is to overcome the shortcomings of known frequency selection devices and provide a simple housing for mounting two frequency selection devices inside an antenna, which provide a narrow boundary band between the passband and the stopband.

[0006] For example, in order to reduce the production cost of duplexers that operate in the 600-6000MHz frequency band used in modern mobile communications and provide 1-5% boundary band between two passbands.

[0007] Modern base station dual-band antennas generate beams of electromagnetic waves with bipolarization, and contain beamforming networks for each beam. Therefore, antennas operating in two frequency bands contain pairs of duplexers.

[0008] Antennas that independently provide variable beam direction in two frequency bands contain pairs of duplexers connected to each radiating element, which provides bipolar electromagnetic waves. Duplexers providing a narrow boundary band between two passbands are very large; therefore, antennas containing multiple duplexers require a large radome to house them. Consequently, it is necessary to reduce the size and manufacturing cost of duplexers.

[0009] To achieve the objectives of this invention, a specially shaped housing for two duplexers is provided. The housing has the shape of a metal profile and contains two cavities for branching strip conductors, which form a series portion of a transmission line and an open stub connected in parallel with the series portion. Each cavity has a polygonal cross-section, including wide walls and narrow walls. The cavity contains at least two regions where the distance between the wide walls differs by at least 20%, and one narrow wall is at least 20% shorter than the other narrow walls forming the cavity. The cavity has a common wide wall comprising a step disposed at a boundary located between regions where the wide walls of the regions have different distances.

[0010] The housing for two duplexers according to the invention is smaller in size than two housings for a single duplexer, and the duplexers contain the same branched strip conductors, thus reducing the manufacturing cost of the two duplexers. The size of the radome can also be reduced using the housing provided by the invention.

[0011] The branch strip conductor forming the open stub is located in a region where the distance between the wide walls is greater than in other regions. The narrow walls contain openings where the ends of the branch strip conductor forming the duplexer's ports are positioned. The branch strip conductor forming the duplexer is made of a single piece of metal, isolated from the housing, and connected only at its ends to the inner conductor of a coaxial cable connected to the duplexer's ports. The branch strip conductor is supported by a foam dielectric substrate and secured to it by dielectric leads.

[0012] The open stub has a higher impedance than the series section, and is located in a portion of the housing where the distance between the wide walls is greater. The series section, with lower impedance, is located in another portion of the housing where the distance between the wide walls is smaller. This structure reduces the difference in width between the branches of the strip conductor and creates a narrow attenuation band near the attenuation pole. Therefore, the duplexer can provide a narrow boundary band between the passbands. Using an open stub with a flat, helical shape can further increase its width. The duplexer according to the invention dramatically increases the insertion loss from the passband and provides a 1-5% boundary band between the two passbands.

[0013] The duplexer provided by this invention does not contain any metal parts in contact with each other because the branched strip conductor is made of a single piece of metal and is isolated from the tubular conductive housing, which is also made of a single piece of metal. Therefore, the housing of known duplexers has a cover pressed together by screws and a short-circuit stub pressed or welded to the conductive housing. Compared to known duplexers that include a housing, this simple structure of the duplexer of this invention provides a lower level of passive intermodulation and lower manufacturing costs.

[0014] The branched strip conductor is formed as a single piece of metal through stamping and supported by a foam dielectric substrate, allowing for very small manufacturing tolerances. Therefore, the duplexer provided by this invention is manufactured without a tuning process and does not include tuning screws. As a result, its production cost is lower than that of known duplexers that provide low insertion loss. Attached Figure Description

[0015] Some relevant embodiments of the present invention are shown in the figures:

[0016] Figure 1a and 1b A top view of a stripline of a first-class passband filter is shown, which includes a mainline and an open stub as described in US 5291161 (Prior Art), and the frequency characteristics of its insertion loss increase sharply in the frequency band above the passband.

[0017] Figure 2a and 2b A top view of a stripline of a second-class passband filter is shown, which includes a mainline and an open stub as described in US 5291161 (Prior Art), and whose frequency characteristics of insertion loss increase sharply in the frequency band below the passband.

[0018] Figure 3 This is a schematic diagram of a duplexer with four open stubs according to the present invention.

[0019] Figure 4 The frequency characteristics S11, S21, and S31 of the duplexer are shown, and its schematic diagram is as follows. Figure 3 As shown, the transmission length Ln and impedance Zn are given in Table 1.

[0020] Figure 5 This is a side view of a first embodiment of the housing for two duplexers according to the present invention.

[0021] Figure 6 This is a top view of the branched strip conductors that form a duplexer with strip lines from Table 1.

[0022] Figure 7 This is a perspective view of a component that includes branched strip conductors disposed between four foam dielectric substrates.

[0023] Figure 8 This is a perspective view showing the housing of a first embodiment of a duplexer according to the present invention, with a coaxial cable connected to the port of the duplexer.

[0024] Figure 9 yes Figure 5-8 The analog frequency characteristics S11, S21, and S31 of the duplexer are shown.

[0025] Figure 10 The analog frequency characteristics S11, S21, and S31 of the second embodiment of the duplexer are given. This duplexer has... Figure 3 The schematic diagram shown has the transmission length Ln and impedance Zn as shown in Table 2.

[0026] Figure 11 This is a perspective view of a second embodiment of the housing for two duplexers according to the present invention.

[0027] Figure 12 This is a top view of the branched strip conductor of a second embodiment of a duplexer.

[0028] Figure 13 It shows having, for example Figure 12 The frequency characteristics S11, S21, and S31 of the duplexer of the branched strip conductor are shown. Detailed Implementation

[0029] It should be understood that the present invention is not limited to the specific forms disclosed in the above drawings. The present invention is intended to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention as defined in the appended claims.

[0030] The purpose of this invention is to reduce the production cost and insertion loss of duplexers that provide 1-5% separation between the passband and stopband for modern mobile communications.

[0031] Figure 1a and Figure 2aThe stripline of the known filter shown consists of a main strip conductor and an open stub connected in parallel with the main strip conductor, which connects the input and output ports of the filter. Filters with this structure can have their insertion loss frequency characteristics shaped as follows: Figure 1b As shown, it increases sharply in the frequency band above the passband, such as... Figure 2b As shown, it increases sharply in the frequency band below the passband.

[0032] By calculating and optimizing different schematics, the optimal structure for a duplexer separating the 1710-1830 MHz and 1885-2025 MHz passbands was found. As a result, the selected... Figure 3 The schematic diagram shown is designed to provide ideal matching in the passband and isolation between passbands. Table 1 contains the transmission line length Ln and impedance Zn, providing, for example... Figure 4 The calculated frequency characteristics are shown. This duplexer provides S11 = -25 dB in the 1710–1830 and 1885–2025 MHz passbands with a passband spacing of 26.5 dB. Each filter of the duplexer contains two open stubs connected in parallel with the series portion of the strip conductor.

[0033] The passband is separated by a 55MHz boundary band, which is 3% of the mid-frequency of the boundary band. Table 1 contains the transmission line length Ln and impedance Zn forming the duplexer, providing... Figure 4 The frequency characteristics are shown. The third row of Table 1 contains the width of the strip conductor, forming a frequency response as shown. Figure 3 The schematic diagram shows the components. The strip conductor is 0.5 mm thick and is placed inside the housing. There is a 7 mm gap between the wide walls of the housing. The strip conductor is between foam dielectric substrates with a dielectric constant of 1.06. Calculate the width Wn of the strip conductor.

[0034] Table 1

[0035] N1 N2 N3 N4 N5 N6 N7 N8 N9 N10 N11 L,mm 36.11 6.91 39.59 10.37 37.74 9.75 65.6 41.09 71.02 42.85 27.04 Z, Ohm 35.86 105.77 240 104.53 231.23 81.6 39.02 232.33 54.25 78.35 20.19 W,mm 12.96 2.12 - 2.19 0.01 3.74 11.63 0.01 8.01 4.04 25.85 <![CDATA[W n ,mm]]> 10.89 1.72 0.01 1.77 0.02 3.09 9.76 0.02 6.16 6.16 21.79

[0036] Calculations for a duplexer with a 3% boundary band show that the impedances of the transmission lines differ by almost a factor of 12, making certain sections of the branched strip conductor too narrow to manufacture. A known method to increase the strip conductor width is to increase the distance between the walls, but this would also increase other sections of the branched strip conductor. As a result, a duplexer with such a wide strip conductor would be too large. Therefore, known design methods are not suitable for duplexers providing a narrow boundary band between two passbands. Thus, a new method has been found to reduce the size of both duplexers, thereby providing... Figure 4 The frequency characteristics are shown.

[0037] To achieve the objectives of this invention, a specially shaped housing for two duplexers is provided. For example... Figure 5The housing shown has the shape of a metal profile 1, which contains identical cavities 2a and 2b for forming branched strip conductors of a duplexer. Each cavity has a polygonal cross-section consisting of narrow and wide walls, including steps at the boundaries between regions with varying distances between their wide walls. Cavity 2a consists of regions 3a and 4a, with wide walls spaced 6 mm and 10 mm apart, respectively. Short narrow walls 5a and 5b are 6 mm long, while other narrow walls 6a and 6b are 10 mm long. Cavities 2a and 2b share a common wide wall 7, comprising portions 7a and 7b and a step 7c, which is located at the boundary between regions 3a and 4a, with varying distances between their wide walls. Open stubs N3, N5, N8, and N10 are located in region 4a, with their wide walls spaced 10 mm apart. The remaining portions of the branched strip conductors are located in region 3a, with their wide walls spaced 6 mm apart. Due to this configuration of the outer casing and branched strip conductors, the width differences in certain sections become significantly smaller. The last row of Table 1 contains the calculated width Wn of the branched strip conductor sections. The width of the widest section N11 decreases from 25.5 mm to 21.79 mm, and the width of the open stub increases by approximately 25%.

[0038] The housing for two duplexers according to the invention has a smaller size than two housings for a single duplexer, both of which contain the same branched strip conductors, because the wide region 4b of cavity 2b is disposed opposite to the narrow region 3a of cavity 2a, and the narrow region 3b is disposed opposite to the wide region 4a. The provided housing includes a common wide wall comprising a step 7c, and the cost of manufacturing the housing provided by the invention is lower than the cost of manufacturing two housings for a single duplexer.

[0039] To further increase the width of the strip conductor forming the open stub, it is made into a flat helical shape. This shape allows for the formation of an open stub with the impedances shown in Table 1 from a strip conductor with a width of not less than 1.4 mm. The 1.4 mm wide strip conductor can be manufactured by stamping together with the other parts of the branched strip conductor, thus making the manufacture of this duplexer inexpensive.

[0040] Figure 6A top view of the branch strip conductors of the duplexer is shown. The dimensions of the branch strip conductors were optimized to compensate for discontinuities at certain interconnections. All open stubs are positioned in a region with a 10mm gap between the wide walls. Open stubs N3, N5, and N8 have a flat helical shape to further increase their width. Open stub N10 has a curved shape to reduce the size of the duplexer. The remaining portions of the branch strip conductors are positioned in a region with a 6mm gap between the wide walls and also have a curved shape to reduce the size of the duplexer. Hole 9 is used for dielectric pins that secure the branch strip conductors 8 to the dielectric foam substrate.

[0041] Figure 7 This is a perspective view of an assembly including branched strip conductors 8 disposed between four foam dielectric substrates 10a-10d. The branched strip conductors 8 are secured to the foam dielectric substrates via dielectric pins 11 passing through holes 9. The dielectric foam substrates 10a-10d contain holes 12a-12c, which are disposed opposite to open stubs N3, N5, N8, and N10. Holes 12a-12c reduce the frequency characteristics of the duplexer's dependence on the characteristics of the foam dielectric substrates, thus reducing the dependence of the frequency characteristics on manufacturing tolerances.

[0042] Figure 8 It is a perspective view showing the housing of a first embodiment of a duplexer according to the present invention, with its coaxial cables 20a-20c connected to the ports of the duplexer. Figure 7 The two components shown are disposed in cavities 2a and 2b within the housing 1. The ends 8a-8c of the branch strip conductor 8 are correspondingly placed in openings 13a-13c. Coaxial cables 20a-20c are mounted into the longitudinal cavity 16 through openings 14a-14d, with the inner conductors 17a-17c of the coaxial cables correspondingly soldered to the ends 8a-8c of the branch strip conductor 8. The outer conductors 18a-18c of the coaxial cables 20a-20c are disposed within the longitudinal cavity 16. A portion of the coaxial cable 20a disposed between openings 13a and 14a is soldered to portion 21a. Solder penetrates into the longitudinal cavity 16 through the longitudinal slit 15. Openings 13a and 14a partially separate portion 21a from the rest of the narrow wall 5a, preventing heat from diffusing from portion 21a during the soldering of the outer conductor 18a to portion 21a. Therefore, the soldering process requires less heating. Protective tubes 19a-19c cover the outer conductors 18a-18c and provide support near the soldered ends to prevent the outer conductors 18a-18c from breaking under vibration. Furthermore, the protective tubes 19a-19c separate the unsoldered portions of the outer conductors 18a-18c from the housing 1 and prevent them from contacting the two metal components. Therefore, the duplexer according to the invention provides a low level of passive intermodulation.

[0043] Figure 9 Showing Figure 5-8 The analog frequency characteristics S11, S21, and S31 of the duplexer are shown. This duplexer provides S11 = -21 dB in the 1710-1830 and 1885-2025 MHz passbands, with an insertion loss S21 of less than 0.3 dB and a passband spacing of 27.5 dB. Therefore, the duplexer housed within the casing of this invention has a simple design and provides ideal frequency characteristics.

[0044] Calculation has Figure 3 The schematic diagram shows a second embodiment of the duplexer to provide a passband separation of 824-880 and 900-960 MHz. The passband is separated by a 55 MHz boundary band, which is 2.2% of the boundary band intermediate frequency. Table 2 contains the transmission line length Ln and impedance Zn, providing information such as... Figure 10 The frequency characteristics are shown. This duplexer provides S11 = -24dB in the passbands of 824-880 and 900-960MHz, with a passband spacing of 26dB. A strip conductor with a thickness of 0.5mm is disposed between foam dielectric substrates with a dielectric constant of 1.06, which are housed within a housing. The housing walls are spaced 7mm apart. Calculate the width Wn of the strip conductor.

[0045] Table 2

[0046]

[0047] The calculation results shown in the third row of Table 2 indicate that the open stubs N8 and N10 of the branched strip conductor with Z greater than 300 Ohm are too narrow to be manufactured.

[0048] Compared to the impedance of the first embodiment, the open stub of the second embodiment of the duplexer has a higher impedance because the boundary band of the second embodiment is narrower. Therefore, it is necessary to increase the distance between the wide walls in the region where the open stub is located to increase the width of its strip conductor.

[0049] When open stubs N3, N5, N8 and N10 are set in a region with a distance of 16 mm between the wide walls, and the series connection is set in a region with a distance of 6 mm between the wide walls, the last row of Table 2 contains the calculated width Wn of the branch strip conductor.

[0050] A perspective view of a second embodiment of the housing for two duplexers according to the present invention is shown below. Figure 11 As shown.

[0051] like Figure 11 The housing shown has the shape of a metal profile 22, which contains the same cavities 23a and 23b for forming branched strip conductors of a duplexer.

[0052] Each cavity has a cross-section with a polygonal shape consisting of narrow and wide walls, including steps at the boundaries between regions whose wide walls are spaced at different distances.

[0053] Cavity 23a is composed of regions 24a and 25a, with distances of 6 mm and 16 mm between their wide walls, respectively. Short narrow walls 26a and 16b are 6 mm long, while other narrow walls 27a and 27b are 16 mm long. Cavities 23a and 23b share a common wide wall 28, which includes portions 28a and 28b and a step 28c. The step is located at the boundary between regions 24a and 25a, and the distances between the wide walls of regions 24a and 25a are different. Open stub conductors N3, N5, N8, and N10 are located in region 25a where the distance between the wide walls is 16 mm. The remaining portions of the branched strip conductors are located in region 24a where the distance between the wide walls is 6 mm.

[0054] The calculated width of the open stub was still too narrow, so the open stub was made into a flat spiral shape to increase its width.

[0055] Figure 12 This is a top view of the branch strip conductor of a second embodiment of the duplexer. Open stubs N3, N8, and N10 have a flat helical shape. Open stub N5 has a curved shape to reduce the size of the duplexer. Other portions of the branch strip conductor are disposed in areas with a 6mm distance between the wide walls and have curved shapes to reduce the size of the duplexer. Holes 30 are used for dielectric leads to secure the branch strip conductor 29 to the dielectric foam substrate. The dimensions of the branch strip conductors are optimized to compensate for the effects of discontinuities at certain interconnections.

[0056] Figure 13 yes Figure 11 and Figure 12 The duplexer is shown with analog frequency characteristics S11, S21, and S31. The duplexer provides S11 = -20 dB in the 824-880 and 900-960 MHz passbands, with an insertion loss S21 less than 0.3 dB and a passband spacing of 26.5 dB. Therefore, the duplexer housed within the enclosure of this invention has a simple design and provides ideal frequency characteristics. Thus, the provided duplexer can be used with many dual-polarized antennas that operate on two frequency bands separated by narrow boundary bands. Other frequency selection devices can also be manufactured using the enclosure according to the invention.

[0057] Branched strip conductors can also be manufactured using conventional printed circuit board (PCB) technology, which provides very narrow strip conductor widths and forms open stubs with high impedance.

Claims

1. A housing for two frequency selective devices comprising a split strip conductor arranged inside the housing, the split strip conductor forming a series section of a transmission line and an open stub in parallel with the series section, the housing comprising a piece of metal profile comprising two cavities for forming the split strip conductor of the two frequency selective devices; wherein each cavity comprising a split strip conductor has a polygonal shape in cross section, the cross section comprising wide walls and narrow walls; wherein the cavities comprise at least two regions in which the distance between the wide walls differs by at least 20% and one narrow wall is at least 20% shorter than the other narrow walls forming the cavity; wherein the section of the split strip conductor forming the open stub is arranged in a region in which the distance between the wide walls is larger than in the other regions; wherein the narrow walls comprise openings in which the ends of the split strip conductor forming the ports of the frequency selective devices are arranged; wherein the cavities have a common wide wall comprising a step arranged at a boundary between regions having different distances between the wide walls.

2. The housing of claim 1, wherein The frequency selective devices are diplexers.

3. The housing of claim 1, wherein The frequency selective devices are passband filters.

4. The housing of claim 1, wherein The frequency selective devices are stopband filters.

5. The enclosure of claim 1, wherein, The housing comprises a circular longitudinal channel along the narrow wall having the openings.

6. The housing of claim 5, wherein, The circular longitudinal channel comprises a longitudinal slit.

7. Two frequency selective devices, characterized in that, The housing of any of claims 1-6, the split strip conductor forming the frequency selective devices is a monolithic piece of metal isolated from the housing and is connected to the inner conductor of a coaxial cable only through its ends at the ports of the frequency selective devices.

8. The two frequency selective devices of claim 7, wherein, The split strip conductor is arranged between foam dielectric substrates perpendicular to the narrow walls of the housing.

9. The two frequency selective devices of claim 8, wherein, The foam dielectric substrates comprise holes arranged opposite to the sections of the split strip conductor forming the open stub.

10. The two frequency selective devices of claim 8, wherein, The split strip conductor is fixed to the foam dielectric substrates by dielectric pins.

11. The two frequency selective devices of claim 7, wherein, The split strip conductor is formed on the surface of two dielectric substrates inside the two cavities of the housing by printed circuit board technology.

12. Assembly method, characterized in that, Applicable to the two frequency selective devices of any of claims 7-11, comprising the steps of: mounting a coaxial cable in the circular longitudinal channel and soldering its outer conductor to the conductive housing narrow wall close to the openings; assembling the split strip conductor and the foam dielectric substrates into an assembly with dielectric pins, mounting the assembly in the conductive housing so that the ends of the split strip conductor are arranged opposite to the openings in the narrow wall; moving the assembly towards the openings in the narrow wall, providing direct contact between the ends of the split strip conductor and the inner conductor of the coaxial cable; soldering the ends of the split strip conductor to the inner conductor of the coaxial cable.

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