A contact spring structure and an adjustable filter

Abstract

The present invention relates to the field of microwave passive circuits, and more particularly to a contact spring structure and a tunable filter. The present invention provides a contact spring structure comprising multiple fingers disposed on a base, wherein one end of the finger is fixed to the base and the other end is suspended in the air. Each of the multiple fingers is provided with a bump on the side facing away from the base. The bumps collectively form a spring contact surface, which increases the contact area when in use. The multiple fingers act as multiple conductive branches, thereby dispersing current density. Furthermore, due to the multiple conductive branches, if any one conductive branch experiences an abnormality, the remaining conductive branches can still operate normally, thereby improving the reliability and effectiveness of the contact spring structure.

Description

Technical Field

[0001] This invention relates to the field of microwave passive circuits, and more particularly to a contact spring structure and an adjustable filter. Background Technology

[0002] In communication systems, when two or more radio frequency signals are transmitted through devices with nonlinear characteristics, intermodulation products (IMPs) are generated in the synthesized signal. When these IMPs fall into the passband of a nearby receiver, they form parasitic interference. Nonlinearity is unavoidable in passive transmission systems; however, when the carrier signal is small, the passive intermodulation interference (PIMI) caused by the passive intermodulation products (PIMPs) generated by nonlinearity is small and goes unnoticed. But when the carrier signal is large, this intermodulation interference becomes more noticeable. PIMPs are typically generated in multi-carrier communication environments, such as shipborne communication systems with shared broadband antenna feeders, terrestrial mobile communication base stations, and satellite ground receiving stations. In particular, shipboard communication systems that require high-power transmission systems and high-sensitivity receiving systems to coexist in a limited space cannot ignore the objectively present PIMI.

[0003] For transceiver multiplexers, multiple adjustable filters are typically connected in parallel to a multi-pass head, which is then connected to the coupling network output. When multiple radio stations transmit simultaneously through multiple adjustable filters, PIMI (Pulse Interference Mode) inevitably occurs, causing the interference signal to be greater than the small signal to be received, resulting in abnormal reception by the multiplexer. To mitigate the impact of PIM, the PIM3 values ​​of all RF devices in the entire RF communication link must be excellent to ensure excellent passive intermodulation for the entire system.

[0004] A filter's function is to allow signals of a specific frequency to pass through while attenuating signals outside that frequency. Some filters, multiplexers, or combiners require high power capacity, low passive intermodulation (NIM), and low loss. In practice, low NIM requires linear metal contact at critical electrical connections. One critical electrical connection in an adjustable filter is between the contact spring and the moving plate assembly. There is one contact point between the contact spring's finger and the moving plate assembly's retaining ring; the NIM level at this point reflects the overall NIM level of the filter. However, in high-power applications, the nonlinear characteristics of the metal connection are amplified. Traditional contact springs are made of brass and have only two fingers, with only two contact points between the contact spring's finger and the moving plate assembly's retaining ring. Figures 1 to 5As shown, the electrical connectivity of the contact points affects the passive intermodulation capability of the filter. In a specific example, due to material limitations, suboptimal structural design, and non-standard manufacturing processes, the filter exhibits poor passive intermodulation, resulting in the following specific problems:

[0005] Traditional contact spring base 3 has only two fingers 1, each finger has a protrusion 2, the protrusion serves as the contact point 4 that contacts the fixed ring of the moving plate assembly. That is, there are only two single-point contacts with the moving plate assembly, the total contact area is small, the current density is concentrated at two points, and because there are few fingers, the passive intermodulation performance of the filter drops sharply when any one finger is abnormal, resulting in low reliability and effectiveness of the contact spring structure. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a contact spring structure and an adjustable filter.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A contact spring structure includes a base and multiple fingers. One end of the multiple fingers is fixed to the base, and the other end of the multiple fingers is suspended in the air. The other end of the multiple fingers has protrusions on its side away from the base, and the multiple protrusions together form a spring contact surface.

[0009] Another technical solution adopted in this invention is:

[0010] An adjustable filter includes a filter cavity, a movable plate shaft is provided inside the filter cavity, a fixed ring is sleeved on the movable plate shaft, and a contact spring structure is also included. The base is provided on the inner side wall of the filter cavity and is spaced apart from the position of the fixed ring. The protrusions on the finger are elastically connected to and fit against the fixed ring.

[0011] The beneficial effects of this invention are as follows:

[0012] This invention provides a contact spring structure with multiple fingers mounted on a base. One end of each finger is fixed to the base, while the other end is suspended. Each finger has a protrusion on its side facing away from the base, forming a spring contact surface. This increases the contact area during use. The multiple fingers act as multiple conductive paths, dispersing the current density. Furthermore, because of these multiple conductive paths, if any one path malfunctions, the others can still operate normally, improving the reliability and effectiveness of the contact spring structure. When this contact spring structure is applied to an adjustable filter, the base is located on the inner wall of the filter cavity and spaced apart from the fixed ring. The protrusions on the fingers are elastically connected to and fitted against the fixed ring. Therefore, if any conductive path malfunctions, the passive intermodulation performance of the filter remains largely unaffected. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the contact spring structure in the background art;

[0014] Figure 2 yes Figure 1 Side view;

[0015] Figure 3 This is a schematic diagram of the assembly structure of the contact spring structure and the fixing ring in the background art;

[0016] Figure 4 This is a schematic diagram of the structure of the tunable filter in the background technology;

[0017] Figure 5 It is the PIM3 value of the tunable filter in the background technology;

[0018] Figure 6 This is a schematic diagram of the contact spring structure of the present invention;

[0019] Figure 7 yes Figure 6 Side view;

[0020] Figure 8 This is a schematic diagram of the assembly structure of the contact spring structure and the fixing ring of the present invention;

[0021] Figure 9 yes Figure 8 A magnified view of a section at point A in the middle;

[0022] Figure 10 This is a schematic diagram of the structure of the tunable filter of the present invention;

[0023] Figure 11 This is the PIM3 value of the adjustable filter of this invention;

[0024] Label Explanation:

[0025] 1. Finger; 2. Raised dot; 3. Base; 4. Contact point; 5. Fixing ring; 6. Moving plate shaft; 7. Metal housing; 8. Finger; 9. Raised dot; 10. Base. Detailed Implementation

[0026] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0027] Please refer to Figures 6 to 11 The present invention provides a contact spring structure, including a base and multiple fingers. One end of the multiple fingers is fixed to the base, and the other end of the multiple fingers is suspended in the air. The other end of the multiple fingers has protrusions on the side facing away from the base, and the multiple protrusions together form a spring contact surface.

[0028] As can be seen from the above description, the beneficial effects of the present invention are as follows:

[0029] This invention provides a contact spring structure with multiple fingers mounted on a base. One end of each finger is fixed to the base, while the other end is suspended. Each finger has a protrusion on its side facing away from the base, and these protrusions together form a spring contact surface. In use, this increases the contact area. The multiple fingers act as multiple conductive paths, thus dispersing the current density. Furthermore, because of these multiple conductive paths, if any one of them malfunctions, the remaining paths can still operate normally, thereby improving the reliability and effectiveness of the contact spring structure.

[0030] Furthermore, the multiple fingers are inclined relative to the plane of the base, and the angles they form with the plane of the base are all equal.

[0031] As can be seen from the above description, the above design can make the elastic deformation of multiple fingers balanced, the overall force is balanced, and the service life is ensured.

[0032] Furthermore, the finger is fan-shaped, and the protrusion is located at the end of the finger corresponding to the fan shape that is furthest from the arc length.

[0033] As can be seen from the above description, the fingers are fan-shaped, which ensures the connection strength with the base, while the multiple protrusions can approach each other to form a spring contact surface.

[0034] Furthermore, the protrusion is hemispherical.

[0035] Furthermore, the surface of the protrusion is coated with a conductive lubricating material.

[0036] As can be seen from the above description, the surface of the protrusion is coated with a conductive lubricating material, which serves three purposes: first, it provides lubrication, further reducing frictional loss between the protrusion and the retaining ring; second, it enhances conductivity and makes the current distribution between the protrusion and the retaining ring more uniform, ensuring low current density and high electrical contact linearity at a single point; and third, it isolates the air and prevents metal oxidation to form an insulating layer.

[0037] Furthermore, one end of each of the multiple fingers is located on the circumference of the same first virtual circle, and the multiple protrusions are located on the circumference of the same second virtual circle.

[0038] Furthermore, each of the fingers is provided with a slotted structure. The slotted structure is a strip-shaped groove extending along the length of the finger, with one end of the strip-shaped groove located at the connection between the finger and the base, and the other end of the strip-shaped groove located at the middle of the finger.

[0039] As described above, the finger has a grooved structure, which allows the pressure between the finger and the retaining ring to be adjusted. The larger the groove, the smaller the pressure. Controlling the pressure within a suitable range can prevent excessive pressure from causing high friction and producing black powder, while also avoiding insufficient pressure from resulting in poor linear contact.

[0040] Furthermore, the base is provided with a through hole, and multiple fingers are arranged around the edge of the through hole.

[0041] As can be seen from the above description, a through hole is provided for the moving shaft to pass through.

[0042] Furthermore, the number of fingers is twelve, with three fingers forming a group, and four groups of fingers arranged at equal intervals around the edge of the through hole.

[0043] An adjustable filter includes a filter cavity, a movable plate shaft is provided inside the filter cavity, a fixed ring is sleeved on the movable plate shaft, and a contact spring structure is also included. The base is provided on the inner side wall of the filter cavity and is spaced apart from the position of the fixed ring. The protrusions on the finger are elastically connected to and fit against the fixed ring.

[0044] As described above, when the contact spring structure is applied to an adjustable filter, the base is located on the inner wall of the filter cavity and is spaced apart from the position of the fixing ring. The protrusions on the fingers are elastically connected to and fit snugly with the fixing ring. When any one of the conductive branches is abnormal, the passive intermodulation performance of the filter can be largely unaffected.

[0045] Please refer to Figures 6 to 11 Embodiment 1 of the present invention is as follows:

[0046] This invention provides a contact spring structure, comprising a base 10 and multiple fingers 7. The base 10 has a circular through hole at its center for a moving shaft to pass through, the radius of which is 7.3 mm. The number of fingers 7 is twelve, arranged in groups of three, with four groups of fingers evenly spaced around the edge of the through hole. This number is six times that of existing contact springs, with each group of three fingers arranged side-by-side along the four corner bisectors of the base. Alternatively, a preferred embodiment may have sixteen or twenty fingers.

[0047] One end of each of the fingers is fixed to the base, while the other end is suspended in the air. That is, the fingers are tilted relative to the plane of the base, and each finger forms an equal angle with the plane of the base. Specifically, the tilt angle is set to 17°.

[0048] Each finger is the same size. The extended lines of the sides of each finger intersect at the center of the circle, and the distance between adjacent fingers is 0.1mm.

[0049] The other ends of the multiple fingers have hemispherical protrusions 9 on their sides facing away from the base, and these protrusions together form a spring contact surface. The fingers are fan-shaped to ensure strong connection with the base, and the protrusions are located at the ends of the fan shape furthest from the arc length. One end of each of the multiple fingers lies on the circumference of the same first virtual circle, and the multiple protrusions lie on the circumference of the same second virtual circle.

[0050] The other end of the finger (i.e., the tip) is bent 2.7mm to align with the retaining ring, and the bent part bulges out a hemisphere with a radius of 1.9mm to seamlessly and elastically connect and fit with the retaining ring 5. The specific values ​​of the above two dimensions are designed according to actual requirements, but the length of the bent part must be greater than the radius of the protrusion 9, and the protrusion 9 must be seamlessly and elastically connected with the retaining ring 5.

[0051] It should be noted that all protrusions are at the same height from the base. Depending on the distance between the fixing ring 5 and the base 10, and the size of the base 10, other angles can be designed, but the protrusion 9 must be seamlessly and elastically connected to the fixing ring 5. The surface of the protrusions is coated with a conductive lubricating material. This serves three purposes: first, it provides lubrication, further reducing frictional loss between the protrusion and the fixing ring; second, it enhances conductivity and makes the current distribution between the protrusion and the fixing ring more uniform, ensuring low current density and high electrical contact linearity at individual points; and third, it isolates the metal from air, preventing metal oxidation and the formation of an insulating layer.

[0052] Each finger is provided with a slotted structure. The slotted structure is a strip-shaped groove extending along the length of the finger, with one end located at the connection between the finger and the base, and the other end located in the middle of the finger. This allows for adjustable pressure between the finger and the retaining ring; the larger the slot, the smaller the pressure. Controlling the pressure within a suitable range prevents excessive pressure leading to high friction and the generation of black powder, while also avoiding insufficient pressure resulting in poor linear contact.

[0053] The fingers are made of beryllium bronze (e.g., QBe2-Y2), a highly elastic, wear-resistant, and highly conductive metallic material. The retaining ring is made of tin bronze (e.g., QSn6.5-0.1-Y), a highly wear-resistant and highly conductive metallic material. The twelve fingers are divided into four groups of three, distributed at the four corners, with a small gap between fingers in the same group. The protrusions are located at the tips of the fingers and are hemispherical. When not installed, as shown... Figure 7 The finger has a designed height h, which is 4mm. When installed on the filter, as follows... Figure 9 There is a gap d between the base and the retaining ring, which is 3mm. After installation, apply an appropriate amount of conductive grease (such as SYN-setral-EK339) to the protrusions and the retaining ring. The symmetrical finger protrusions are 13mm apart.

[0054] It should be noted that the existing contact spring material is brass, which lacks sufficient elasticity and toughness. During installation into the filter, fingers pressing on the contact spring may cause deformation that prevents it from returning to its initial state. This results in poor contact between the protrusions on the finger and the retaining ring of the moving plate assembly, concentrating the current density at a single point and generating a high passive intermodulation level. Furthermore, brass contact springs have insufficient wear resistance. During normal use of the adjustable filter, the rotation of the traditional brass brake plate assembly rubs against the traditional brass contact spring. Over time, the friction wear between the contact spring and the moving plate assembly becomes severe, leading to an uneven contact surface, uneven current density, and passive intermodulation levels. Simultaneously, friction causes waste black powder to fall inside the filter, potentially affecting critical filter parameters such as insertion loss and VSWR.

[0055] Please refer to Figures 6 to 11 Embodiment two of the present invention is as follows:

[0056] Based on the above embodiment one, an adjustable filter is provided, including a filter cavity, which is made of a metal housing 7. A movable plate shaft 6 is provided inside the filter cavity, and a fixing ring 5 is sleeved on the movable plate shaft 6. The fixing ring 5 has an inner diameter of 12mm and an outer diameter of 18mm. It also includes the aforementioned contact spring structure. The base 10 is disposed on the inner side wall of the filter cavity and is spaced apart from the position of the fixing ring 5. The protrusions 9 on the finger 8 are elastically connected to and fitted with the fixing ring 5.

[0057] The base 10 has a hole in the middle for the moving plate shaft 6 to pass through. The fingers 8 are fixed on the inner side of the base 10 facing the cavity, arranged according to a certain pattern, and have a certain raised height; the protrusions 9 are fixed on the top of the fingers 8 and are seamlessly and elastically connected and fitted to the fixing ring 5; the base 10 and the fixing ring 5 have a fixed interval.

[0058] In this embodiment, the contact spring structure is made of beryllium bronze (such as QBe2-Y2), and the retaining ring is made of tin bronze (such as QSn6.5-0.1-Y). The superior elasticity of these materials ensures a seamless and reliable elastic connection and fit between the contact spring protrusions and the retaining ring of the moving plate assembly. The superior wear resistance of these materials reduces wear on the contact spring protrusions caused by friction during the use of the adjustable filter, while also preventing metal debris from falling into the filter and oxidizing to form black powder, thus affecting filter performance. Adding conductive grease (such as SYN-setral-EK339) to the protrusions and retaining ring serves several purposes: first, it provides lubrication, further reducing frictional loss between the protrusions and retaining ring; second, it enhances conductivity and makes the current distribution between the protrusions and retaining ring more uniform, ensuring low current density at individual points and high electrical contact linearity; and third, it isolates the metal from air, preventing metal oxidation and the formation of an insulating layer. Increasing the number of contact spring fingers from 2 to 12 not only greatly improves product reliability but also distributes the current across the 12 fingers, reducing current density and passive intermodulation. In terms of process design, the distance h from the protrusion to the base is a key dimension; all 12 protrusions are of consistent height with a deviation within ±0.3mm.

[0059] In one specific embodiment, the material of the finger 8, the protrusion 9 and the base 10 is beryllium bronze strip QBe2-Y2, or other better materials can be used to ensure that the material of the contact spring is a metal or alloy with high elasticity, high wear resistance and high conductivity.

[0060] from Figure 5 and Figure 11 The comparison shows that using the contact spring structure provided by this invention can make the passive intermodulation of the whole machine more excellent.

[0061] In summary, the contact spring structure provided by this invention features multiple fingers mounted on a base. One end of each finger is fixed to the base, while the other end is suspended. Each finger has a protrusion on its side facing away from the base, forming a spring contact surface. This increases the contact area during use. The multiple fingers act as multiple conductive paths, dispersing the current density. Furthermore, due to the multiple conductive paths, if any one path malfunctions, the others can still operate normally, thus improving the reliability and effectiveness of the contact spring structure. When this contact spring structure is applied to an adjustable filter, the base is located on the inner wall of the filter cavity and spaced apart from the fixed ring. The protrusions on the fingers are elastically connected to and fitted against the fixed ring. Therefore, if any conductive path malfunctions, the passive intermodulation performance of the filter remains largely unaffected.

[0062] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An adjustable filter, comprising a filter cavity, wherein a movable plate shaft is disposed within the filter cavity, and a fixed ring is sleeved on the movable plate shaft, characterized in that, It also includes a contact spring structure, which includes a base and multiple fingers. One end of the multiple fingers is fixed to the base, and the other end of the multiple fingers is suspended in the air. The other end of the multiple fingers has protrusions on the side facing away from the base, and the multiple protrusions together form a spring contact surface. The base is located on the inner wall of the filter cavity and is spaced apart from the position of the fixing ring. The protrusions on the fingers are elastically connected to and fitted with the fixing ring. The fingers are inclined relative to the plane of the base, and each finger makes an equal angle with the plane of the base. The finger is fan-shaped, and the protrusion is located at the end of the finger corresponding to the fan shape that is furthest from the arc length; Each of the fingers is provided with a slotted structure; The base has a through hole, and multiple fingers are arranged around the edge of the through hole; The number of fingers is twelve, with three fingers forming a group, and four groups of fingers are arranged at equal intervals around the edge of the through hole.

2. The tunable filter according to claim 1, characterized in that, The protrusion is hemispherical.

3. The tunable filter according to claim 1 or 2, characterized in that, The surface of the bump is coated with a conductive lubricating material.

4. The tunable filter according to claim 1, characterized in that, One end of each of the fingers is located on the circumference of the same first virtual circle, and the multiple protrusions are located on the circumference of the same second virtual circle.

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