A coaxial cavity resonator and electrically tunable bandpass filter

Abstract

The application discloses a coaxial cavity resonator and an electrically tunable band-pass filter, and belongs to the technical field of microwave filters. The coaxial cavity resonator comprises an outer cavity, an inner conductor, a tuning rod and a dielectric support. The inner conductor comprises a fixed part and a sliding part. The fixed part is fixed at the central position of the outer cavity through the dielectric support. The sliding part of the inner conductor is in good elastic conductive contact with the fixed part through a spring leaf. The sliding part of the inner conductor can linearly reciprocate inside the fixed part of the inner conductor. The transmission part of the inner conductor is fixed with the tuning rod through a thread. The tuning rod is a non-metal solid cylinder. The electrically tunable band-pass filter is composed of multiple coaxial cavity resonators, input and output structures and a coupling structure between the electrically tunable resonators. The electrically tunable band-pass filter has a wide tuning stroke, an unchanged absolute bandwidth and strong anti-interference capability.

Description

TECHNICAL FIELD

[0001] The present application relates to a coaxial cavity resonator and electrically tunable band-pass filter, belonging to the technical field of microwave filter. BACKGROUND

[0002] The commonly used coaxial cavity electrically tunable filter is a coaxial cavity resonator with contact between the inner conductor and the cavity. The inner conductor needs to be flexibly up and down to change the resonant frequency of the resonant cavity, and also needs to have good conductive contact with the resonant cavity, which is difficult to process. In addition, as the frequency increases, the tuning stroke becomes smaller and smaller, and the accuracy of the tuning is also improved. The absolute bandwidth of the quarter-wave coaxial cavity electrically tunable filter changes with the frequency, and the absolute bandwidth changes, and the anti-interference ability decreases. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the present application provides a half-wave coaxial cavity resonator and electrically tunable band-pass filter.

[0004] To solve the above technical problems, the technical solution adopted by the present application is: a coaxial cavity resonator, comprising an outer cavity 1, a dielectric support 2, an inner conductor 3, and a tuning rod 6; the outer cavity 1 has a positioning protrusion in the upper part, and a circular hole is opened in the center position of the top; the inner conductor 3 comprises an inner conductor fixed part 4 and an inner conductor sliding part 5; the dielectric support 2 is composed of two parts, symmetric and hollow between the two parts, fixed in a specified position in the outer cavity 1, the inner conductor fixed part 4 is fixed in the hollow position of the dielectric support 2, the inner conductor sliding part 5 is inside the inner conductor fixed part 4, and the inner conductor fixed part is in conductive contact with the inner conductor fixed part through a spring piece 17, the inner conductor sliding part 5 is a metal cylinder, and the tuning rod 6 is fixed together through threads, the low end of the inner conductor sliding part 5 has a chamfer design; the tuning rod 6 is an insulator, which extends out of the cavity through the circular hole in the top of the outer cavity 1; the inner conductor 3, the tuning rod 6 and the outer cavity 1 are the same center axis and are assembled in parallel.

[0005] Among them, the dielectric support 2 has a first positioning groove 7 at the contact position between the periphery and the outer cavity 1, and a positioning groove at the contact position between the inner side and the inner conductor fixed part 4, and the material is polytetrafluoroethylene.

[0006] Among them, the inner conductor fixed part 4 has a positioning protrusion 8, which is fixed in the center of the outer cavity 1 through the dielectric support 2 and has no contact with the outer cavity 1. The inner conductor fixed part 4 is a hollow cylinder, one end of which is designed as a spring piece 17, and the material is beryllium bronze; the inner conductor sliding part 5 is a metal material; the outer surface of the inner conductor fixed part 4 and the inner conductor sliding part 5 is silver plated.

[0007] An electrically tunable band-pass filter is composed of input and output coupling structures 20, four coaxial cavity resonators 15 as claimed in claim 1, inter-cavity coupling holes 18, a limiting plate 11, a limiting switch 12, and a linear motor 9. The four coaxial cavity resonators are arranged in a checkered pattern, and the inter-cavity coupling holes 18 are arranged between the adjacent two cavities to realize coupling, and the two resonators at the two ends have the input and output coupling structures 20; the limiting plate 11 is threadedly fixed with the tuning rod 6 of the resonator, and the center position of the limiting plate 11 is installed on the screw rod 13 of the linear motor through a gap-eliminating nut 19; the linear motor 9 is vertically installed on the motor support plate 10 directly above the cavity; the limiting switch 12 has two upper and lower limiting positions, which are respectively arranged above the cavity and below the linear motor support plate 10, and the two switches are vertically aligned.

[0008] The input and output coupling structures 20 include a socket 14 and a coupling probe 16, the coupling probe 16 is a double-probe special-shaped probe, the two ends of the probe respectively extend to the two ends of the cavity and are parallel to the inner conductor, and the probe is a silver-plated copper wire. The inter-cavity coupling hole 18 is a rectangular hole.

[0009] Thanks to the above technical scheme, the technical progress achieved by the present application is as follows:

[0010] 1. The inner conductor of the coaxial cavity resonator is moved to the center of the resonator cavity, and the inner conductor and the outer cavity are designed in a non-contact manner, so that the internal structure of the cavity is easier to realize.

[0011] 2. The present application is a one-half wavelength coaxial cavity resonator, which increases the tuning distance and reduces the precision requirement in the tuning process of the electrically tunable filter; the electromagnetic field in the resonator cavity is moved to the middle position of the cavity, the absolute bandwidth of the electrically tunable filter is more stable, the tuning frequency range is increased, and the anti-interference ability of the electrically tunable filter is improved. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural schematic view of a coaxial cavity resonator.

[0013] Figure 2 is a sectional view of a coaxial cavity resonator;

[0014] Figure 3 is an outline drawing of an electrically tunable band-pass filter;

[0015] Figure 4 is an internal structure drawing of an electrically tunable band-pass filter. DETAILED DESCRIPTION

[0016] The present application will be further described in detail below with reference to the drawings:

[0017] As Figure 1As shown, a coaxial cavity resonator includes an outer cavity 1, an inner conductor 3, a tuning rod 6, and a dielectric support 2.

[0018] like Figure 2 As shown, the dielectric support 2 consists of two symmetrical and hollow parts, which are fixed in a designated position inside the outer cavity 1. The outer periphery of the dielectric support 2 has a first positioning groove 7 at the contact position with the outer cavity 1, and the inner side has a positioning groove at the contact position with the inner conductor fixing part 4, so as to ensure that the dielectric support 2 is firmly fixed in the outer cavity 1. The dielectric support 2 is made of insulating material polytetrafluoroethylene.

[0019] The inner conductor includes an inner conductor fixing part 4 and an inner conductor sliding part 5. The inner conductor fixing part 4 is a hollow cylinder with a spring 17 at one end, which is integrally designed and made of beryllium bronze. The inner conductor fixing part 4 is fixed in the hollow position of the dielectric support 2. The inner conductor fixing part 4 has a positioning protrusion 8 and is fixed to the center of the outer cavity 1 by the dielectric support 2 without contacting the outer cavity 1. The inner conductor fixing part 4 is firmly fixed in the center of the cavity. When the inner conductor sliding part 5 slides up and down in the inner conductor fixing part 4, the inner conductor fixing part 4 should remain stationary. The inner conductor sliding part 5 is inside the inner conductor fixing part 4 and has good elastic conductive contact with the inner conductor fixing part 4 through the spring 17. The spring 17 is located at the lower end of the inner conductor fixing part, and the end of the spring 17 presses against the outer wall of the inner conductor sliding part and is electrically connected to the inner conductor sliding part.

[0020] The inner conductor sliding part 5 is a metal cylinder, fixed to the tuning rod 6 by threads. The lower end of the inner conductor sliding part 5 has a chamfered design. Under the action of the tuning rod, the length of the inner conductor sliding part 5 extending beyond the inner conductor fixed part 4 changes to tune the resonant frequency of the resonant cavity. The tuning rod 6 is an insulator, extending out of the cavity through a round hole at the top of the outer cavity 1. The inner conductor 3, the tuning rod 6, and the outer cavity 1 are all assembled in parallel along the same central axis. The inner conductor sliding part 5 is made of steel. The inner conductor fixed part 4, the inner conductor sliding part 5, and the outer cavity 1 all need to be silver-plated to reduce the overall loss of the resonant cavity.

[0021] like Figure 4As shown, an electrically tunable band-pass filter is composed of an input and output coupling structure 20, four coaxial cavity resonators 15, inter-cavity coupling holes 18, a limiting plate 11, a limiting switch 12 and a linear motor 9. The four coaxial cavity resonators 15 are arranged in a checkered pattern and are integrally processed, so that the structure is simple in process; the inter-cavity coupling holes 18 are arranged between the adjacent two cavities to realize coupling, the inter-cavity coupling holes 18 are located at the middle position of the cavity wall shared by the adjacent two resonant cavities and correspond to the position of the inner conductor, the inter-cavity coupling holes 18 are rectangular holes, and the coupling value of the two resonant cavities can be changed by changing the size and position of the coupling holes; the two resonators at the two ends have the input and output coupling structure 20; the input and output coupling structure 20 includes a socket 14 and a coupling probe 16 which is a double-probe special-shaped probe, the two ends of the double-probe probe respectively extend to the upper and lower ends of the resonant cavity, and the end part is parallel to the inner conductor, the probe is a silver-plated copper wire, and the input and output coupling strength can be changed by changing the distance between the probe and the inner conductor; the limiting plate 11 is threadedly fixed with the four tuning rods 6 of the resonant cavity, and the center position of the limiting plate 11 is installed on the screw rod 13 of the linear motor through a backlash nut 19; the linear motor 9 is vertically installed on the motor support plate 10 directly above the cavity, the center of the linear motor is vertically aligned with the center of the entire resonant cavity; the limiting switch 12 has two upper and lower limiting switches which are respectively located above and below the cavity and the linear motor support plate 10, and the two switches are vertically aligned; the upper and lower limiting switches ensure that the sliding part of the inner conductor slides within the tuning range, so as to avoid that the sliding part of the inner conductor slides out of the designed range. The outer edge of the resonant cavity has a cover plate 21 to ensure the integrity of the cavity.

[0022] The application drives the tuning rods of the four resonant cavities by one motor, realizes the tuning of the electrically tunable filter under the condition that the tuning stroke is wide and the absolute bandwidth is unchanged, and has simple structure and is easy to realize. The application can be applied to any frequency band by changing the size of the cavity.

Claims

1. A coaxial cavity resonator comprising an outer cavity (1), a dielectric support (2), an inner conductor (3), a tuning rod (6); the outer cavity (1) has a positioning protrusion in the upper part, and a circular hole is opened in the center of the top; characterized in that: The inner conductor (3) comprises an inner conductor fixed part (4) and an inner conductor sliding part (5); the medium support (2) is composed of two parts, which are symmetrical and hollow between the two parts, fixed in a specified position in the outer cavity (1), the inner conductor fixed part (4) is fixed in the hollow position of the medium support (2), the inner conductor sliding part (5) is inside the inner conductor fixed part (4), and the inner conductor fixed part is in conductive contact with the inner conductor fixed part through the spring leaf (17), the inner conductor sliding part (5) is a metal cylinder, which is fixed with the tuning rod (6) through threads, and the bottom end of the inner conductor sliding part (5) has a chamfer structure; the tuning rod (6) is an insulator, and the top end thereof extends out of the cavity through a circular hole at the top of the outer cavity (1); the inner conductor (3), the tuning rod (6) and the outer cavity (1) are the same central axis and are parallelly assembled.

2. A coaxial cavity resonator according to claim 1, characterized in that: The medium support (2) has a first positioning groove (7) at the position where the periphery thereof is in contact with the outer cavity (1), and a positioning protrusion is embedded in the corresponding first positioning groove; the inner side thereof has a second positioning groove at the position where it is in contact with the inner conductor fixed part (4), and the material thereof is polytetrafluoroethylene.

3. A coaxial cavity resonator according to claim 2, wherein: The inner conductor fixed part (4) has a positioning protrusion (8) matched with the second positioning groove on the inner side of the medium support, and the inner conductor fixed part (4) is fixed in the center of the outer cavity (1) through the medium support (2) and is not in contact with the outer cavity (1).

4. A coaxial cavity resonator according to claim 3, wherein: The inner conductor fixed part (4) is a hollow cylinder, which is integrally designed with the spring leaf (17) at one end, and the material thereof is beryllium bronze; the inner conductor sliding part (5) is a metal material.

5. A coaxial cavity resonator according to claim 4, wherein: The spring leaf (17) is located at the lower end of the inner conductor fixed part, the end of the spring leaf (17) is pressed against the outer wall of the inner conductor sliding part, and the spring leaf (17) is electrically connected with the inner conductor sliding part.

6. An electrically tunable bandpass filter characterized by: The input and output coupling structure (20), four coaxial cavity resonators (15) as claimed in claim 1, an inter-cavity coupling hole (18), a limiting plate (11), a limiting switch (12) and a linear motor (9) are composed; the four coaxial cavity resonators (15) are arranged in a checkered pattern, and there is an inter-cavity coupling hole (18) between the two adjacent cavities to realize coupling, and the input and output coupling structure (20) is arranged on any two resonators; the limiting plate (11) is threadedly fixed with the tuning rod (6) of the resonant cavity, and the limiting plate (11) is installed on the screw rod (13) of the linear motor through a backlash elimination nut (19) at the center position; the linear motor (9) is vertically installed on the motor support plate (10) directly above the cavity; the limiting switch (12) has two upper and lower limiting positions, which are respectively located on the upper side of the cavity and the lower side of the linear motor support plate (10), and the two switches are vertically aligned.

7. An electrically tunable bandpass filter according to claim 6, characterized in that: The input and output coupling structure (20) comprises a socket (14) and a coupling probe (16); wherein the coupling probe is a double-probe special-shaped probe, the two ends of the double-probe special-shaped probe respectively extend to the two ends of the cavity, and are both parallel to the inner conductor, and the probe is a silver-plated copper wire.

8. The electrically tunable bandpass filter of claim 6, wherein: The inter-cavity coupling hole (18) is a rectangular hole.

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