Multi-frequency antenna and frequency-selective phase-shifting device thereof

Abstract

The present invention provides a frequency-selective phase-shifting device, in which a phase-shifting gear is fixedly provided on a transmission screw of a frequency-selective mechanism, and the transmission screw is driven to move along its axial direction by an active gear, so that the phase-shifting gear can move to the position of any one of the phase-shifting racks corresponding to a plurality of frequency bands arranged in parallel and mesh with it, that is, the phase-shifting rack corresponding to an antenna of a certain frequency band is selected; in addition, the transmission screw is simultaneously driven by the driving gear of the phase-shifting mechanism and the active gear of the frequency-selective mechanism to rotate only in the circumferential direction, so that the phase-shifting gear drives the phase-shifting rack meshed with it to move, so as to perform a phase adjustment operation on the antenna of the frequency band corresponding to the phase-shifting rack. Therefore, the purpose of controlling the phase shifting of antenna frequency band signals corresponding to a plurality of phase-shifting racks is achieved. The present invention also provides a multi-frequency antenna including the above-mentioned frequency-selective phase-shifting device.

Description

Technical Field

[0001] The invention belongs to the technical field of mobile communications, and in particular relates to a multi-frequency antenna and a frequency selection and phase shifting device thereof. Background Art

[0002] As the number of mobile communication terminal users continues to increase, the demand for network capacity of sites in mobile cellular networks is increasing. At the same time, it is required to minimize the interference between different sites or even between different sectors of the same site, that is, to maximize network capacity and minimize interference. To achieve this goal, it is usually achieved by adjusting the downtilt angle of the antenna beam on the site.

[0003] Among the two ways to adjust the beam downtilt angle, mechanical downtilt and electronic downtilt, electronic downtilt has obvious advantages and is the current mainstream and future development trend. The control of electrical downtilt angle is mainly divided into two categories: internal and external, among which internal control is the current and future mainstream.

[0004] However, the motor used to drive the phase shifter in the traditional transmission device still corresponds to the transmission mechanism of the phase shifter one by one, the number of motors has not been reduced, and the number of driving circuits and motors in the control module has not been reduced. If the frequency band of the antenna continues to increase, the transmission system structure will become more complex and bulky, affecting the reliability of the multi-frequency antenna.

[0005] The applicant has implemented relevant technical solutions to the above problems, but there is still room for improvement in terms of stable control and simple operation. In particular, for the situation of controlling multiple devices with one device, there is still much room for improvement in the relevant structure. Summary of the invention

[0006] The first object of the present invention is to provide a frequency-selective phase-shifting device with stable control and simple operation.

[0007] Another object of the present invention is to provide a multi-frequency antenna.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] The present invention provides a frequency-selective phase-shifting device, comprising phase-shifting racks corresponding to a plurality of frequency bands arranged side by side, a frequency-selecting mechanism that is controlled by a driving torque to select a phase-shifting rack of one of the frequency bands, and a phase-shifting mechanism that is controlled by a driving torque to perform phase-shifting control on the selected phase-shifting rack, wherein the frequency-selecting mechanism comprises a transmission screw that is axially arranged parallel to the arrangement direction of the plurality of phase-shifting racks, a driving gear that is screwed with the transmission screw, and a phase-shifting gear that is fixed on the transmission screw, wherein the driving gear is used to drive the transmission screw to move linearly along the arrangement direction, so that the transmission screw drives the phase-shifting gear to mesh with the phase-shifting rack of any frequency band;

[0010] The phase shifting mechanism comprises a driving gear sleeved on the transmission screw, and the driving gear is used to drive the transmission screw to rotate circumferentially, so that the phase shifting gear drives the phase shifting rack meshing with the phase shifting gear to move.

[0011] Furthermore, the transmission screw is provided with at least one anti-rotation groove, the anti-rotation groove is arranged through the transmission screw in the axial direction, and the inner hole of the driving gear is provided with matching locking teeth corresponding to the anti-rotation groove.

[0012] Furthermore, the cross section of the anti-rotation groove is in an arc segment shape, a regular polygon shape, or an irregular polygon shape, and the shape of the cross section of the latch tooth corresponds to the shape of the cross section of the anti-rotation groove.

[0013] Furthermore, the central axis of the phase-shifting gear coincides with the central axis of the transmission screw, and the phase-shifting gear is fixedly sleeved on the transmission screw.

[0014] Furthermore, the phase-shifting gear and the transmission screw are integrally formed.

[0015] Furthermore, the frequency selection mechanism further includes a first motor, which drives the driving gear to rotate through a first gear train, and the phase shifting mechanism further includes a second motor, which drives the driving gear to rotate through a second gear train.

[0016] Furthermore, the frequency-selective phase-shifting device further comprises a support base, and the support base is used to support the phase-shifting rack, the frequency-selective mechanism and the phase-shifting mechanism.

[0017] Furthermore, support frames are respectively provided on both ends of the phase-shift rack in the length direction, and a channel for the phase-shift rack to move is formed between the two support frames.

[0018] Furthermore, the frequency-selective phase-shifting device is provided with two rows of phase-shifting racks, and the two rows of phase-shifting racks are arranged on both sides of the axial direction of the transmission screw, and the two rows of phase-shifting racks are arranged in a staggered manner.

[0019] The present invention also provides a multi-frequency antenna, comprising a plurality of phase shifting components corresponding to a plurality of frequency bands, characterized in that it comprises the above-mentioned frequency-selective phase shifting device, each of the phase shifting components has a corresponding phase shifting rack in the frequency-selective phase shifting device and is arranged in linkage with the phase shifting rack.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] The present invention provides a frequency selection phase shifting device, in which a phase shifting gear is fixedly arranged on a transmission screw in a frequency selection mechanism, and the transmission screw is driven by an active gear to move along its axial direction, so that the phase shifting gear can move to any position of phase shifting racks corresponding to a plurality of frequency bands arranged in parallel and mesh with them, that is, the phase shifting rack corresponding to a certain frequency band antenna is selected; in addition, the transmission screw is simultaneously driven by the driving gear of the phase shifting mechanism and the active gear of the frequency selection mechanism to rotate only in the circumferential direction, so that the phase shifting gear drives the phase shifting rack meshed with it to move, so as to perform a phase adjustment operation on the antenna of the frequency band corresponding to the phase shifting rack. Therefore, the purpose of controlling the phase shifting of antenna frequency band signals corresponding to a plurality of phase shifting racks is achieved.

[0022] In addition, the frequency selection and phase shifting device of the present invention has a simple structure, the frequency selection mechanism and the moving mechanism are combined ingeniously and reasonably, the operation is simple, and the phase adjustment is stable.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 This is a schematic diagram of the internal structure of the frequency-selective phase-shifting device provided by the present invention;

[0026] Figure 2a It is a structural schematic diagram of the transmission screw of the present invention;

[0027] Figure 2b It is a schematic diagram of the cross-sectional structure of the transmission screw of the present invention;

[0028] Figure 3 A schematic diagram of a frequency selection state structure of the frequency selection phase shifting device provided by the present invention;

[0029] Figure 4 A schematic diagram of a phase shift state structure of the frequency selection phase shift device provided by the present invention;

[0030] Figure 5 This is a schematic diagram of another frequency selection state structure of the frequency selection phase shifting device provided by the present invention. DETAILED DESCRIPTION

[0031] Embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are only for exemplary purposes and are not intended to limit the scope of protection of the present invention.

[0032] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to". The term "connected" may be directly connected or indirectly connected through intermediate components (elements). The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0033] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish between devices, modules or units, and are not used to limit these devices, modules or units to be different devices, modules or units, nor are they used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0034] The present invention provides an antenna frequency selection and phase shifting device, which is used to realize phase modulation control of any frequency band signal in a multi-frequency antenna. Figure 1 As shown, the frequency-selective phase-shifting device comprises phase-shift racks 1 corresponding to a plurality of frequency bands arranged side by side, a frequency-selective mechanism 2 which is controlled by a driving torque to select a phase-shift rack 1 of one frequency band, and a phase-shifting mechanism 3 which is controlled by a driving torque to perform phase-shifting control on the selected phase-shift rack 1.

[0035] The frequency selection mechanism 2 includes a transmission screw 21 axially arranged parallel to the arrangement direction of the plurality of phase-shifting racks 1 , a driving gear 22 threadedly arranged with the transmission screw 21 , and a phase-shifting gear 23 fixedly mounted on the transmission screw 21 .

[0036] like Figure 2a As shown, the transmission screw 21 is provided with at least one anti-rotation groove 210, and the anti-rotation groove 210 runs from one end of the transmission screw 21 to the other end of the transmission screw 21 along the axial direction of the transmission screw 21. Figure 2b As shown, the cross section of the anti-rotation groove 210 is in the shape of an arc segment, a regular polygon or an irregular polygon. In the embodiment shown in the figure, two anti-rotation grooves 210 are provided, symmetrically arranged on both sides of the central axis of the transmission screw 21. In other embodiments, the anti-rotation groove 210 can also be three or one, not limited to the embodiment shown in the drawings.

[0037] The central axis of the phase-shifting gear 23 coincides with the central axis of the transmission screw 21, and the phase-shifting gear 23 is fixedly sleeved on the transmission screw 21. In this embodiment, there is only one phase-shifting gear 23, and it is fixedly sleeved on the end of the transmission screw 21. The phase-shifting gear 23 and the transmission screw 21 can be integrally formed, or can be fixedly set on one end of the transmission screw 21 as an accessory.

[0038] The driving gear 22 is sleeved on the transmission screw 21. The gear hole of the driving gear 22 is a threaded hole, and the threaded hole cooperates with the transmission screw 21, so that the driving gear 22 and the transmission screw 21 constitute a transmission screw mechanism. When the driving gear 22 rotates circumferentially, it drives the transmission screw 21 not to rotate circumferentially but to move back and forth in a straight line along the arrangement direction of the phase-shift rack 1, so that the phase-shift gear 23 moves between the positions of the phase-shift racks 1 corresponding to each frequency band. And the phase-shift gear 23 can mesh with the phase-shift rack 1 corresponding to any frequency band. When the phase-shift gear 23 moves to the target phase-shift rack 1 and meshes with it, stopping driving the transmission screw 21 can complete the phase-shift gear 23 selecting the phase-shift rack 1 corresponding to the target frequency band antenna.

[0039] The phase shift mechanism 3 includes a driving gear 31 which is sleeved on the transmission screw 21 and arranged at the same end as the driving gear 22. The inner hole of the driving gear 31 is a circular hole, so that the transmission screw 21 passing through the inner hole of the driving gear will not drive the driving gear 31 to move linearly. The inner hole of the driving gear 31 is provided with latching teeth whose number and shape match the anti-rotation groove 210 of the transmission screw 21. When the driving gear 31 is sleeved on the transmission screw 21, the latching teeth of the inner hole of the driving gear 31 are placed in the anti-rotation groove 210 of the transmission screw 21, so that the driving gear 31 and the transmission screw 21 are engaged. When the driving gear 31 is rotated, the transmission screw 21 rotates in the same direction as the driving gear 31. Since the anti-rotation groove 210 passes through from the end of one end of the transmission screw 21 to the other end of the transmission screw 21 along the axial direction of the transmission screw 21, when the driving gear 22 rotates and the driving gear 31 does not rotate, the transmission screw 21 is circumferentially fixed by the anti-rotation groove 210 and the driving gear 31, which ensures that the transmission screw 21 does not rotate circumferentially during the process of linear movement along the arrangement direction of the phase-shift rack 1. When the transmission screw 21 moves linearly, the teeth of the inner hole of the driving gear 31 relatively move from one end of the anti-rotation groove 210 to the other end, so that the teeth of the driving gear 31 will not block the linear movement of the transmission screw 21, and the transmission screw 21 will not drive the driving gear 31 to move linearly.

[0040] The driving gear 31 is also used to drive the transmission screw 21 to rotate circumferentially in the same direction, so that the phase-shifting gear 23 drives the phase-shifting rack 1 meshing therewith to move up and down (the upward or downward mentioned in the present invention are relative directions, which are only convenient for understanding the core of the invention in combination with the drawings, and are not intended to limit the technical solution of the present invention). Specifically, when the phase-shifting gear 23 moves to the target phase-shifting rack 1, the phase-shifting gear 23 meshes with the target phase-shifting rack 1, and the phase-shifting gear 23 needs to make circumferential motion to drive the target phase-shifting rack 1 to move up or down. That is, the transmission screw 21 needs to make circumferential motion while not making axial motion. Since the driving gear 22 and the transmission screw 21 constitute a transmission screw mechanism, when the driving gear 31 drives the transmission screw 21 to make circumferential motion, the driving gear 22 rotates in the same direction, so that the driving gear 22 and the transmission screw 21 rotate in the same direction. Since the driving gear 22 and the transmission screw 21 do not rotate in opposite directions relative to each other, the transmission screw 21 will not move axially relative to the driving gear 22, so the phase-shifting gear 23 can be fixed at the position of the target phase-shifting rack 1 and rotate circumferentially, thereby driving the phase-shifting rack 1 to move accordingly.

[0041] The phase-shift rack 1 is respectively connected to the phase-shift components of the external phase shifters of different frequency bands (not shown in the drawings). Therefore, the rotation direction and the number of revolutions of the phase-shift gear 23 can be controlled to control the movement direction and displacement of the phase-shift rack 1, so as to control the displacement of the phase-shift components of the phase shifter of the corresponding frequency band, thereby achieving the purpose of controlling the phase modulation of the phase shifter of the frequency band.

[0042] The frequency selection mechanism 2 also includes a first motor 24 and a first gear train 25 fixedly connected to the first motor 24. The first gear train 25 includes one or more gears that cooperate with each other to transmit the driving torque of the first motor 24 to the driving gear 22. When the first motor 24 drives the first gear train 25 to rotate, the first gear train 25 drives the driving gear 22 to rotate in the opposite direction, that is, the first motor 24 drives the driving gear 22 to rotate through the first gear train 25.

[0043] The phase shifting mechanism 3 further includes a second motor 32 and a second gear train 33 fixedly connected to the second motor 32. The second gear train 33 includes one or more gears that cooperate with each other to transmit the driving torque of the second motor 32 to the driving gear 31. When the second motor 32 drives the second gear train 33 to rotate, the second gear train 33 drives the driving gear 31 to rotate in the opposite direction, that is, the second motor 32 drives the driving gear 31 to rotate through the second gear train 33.

[0044] Support frames 4 are respectively mounted on both ends of the phase-shift rack 1 in the length direction to support the phase-shift rack 1. At the same time, the phase-shift rack 1 can move back and forth on the support frames 4 along the length direction of the phase-shift rack 1, and a channel for the phase-shift rack 1 to move is formed between the two support frames 4.

[0045] The frequency-selective phase-shifting device further comprises a support base, and the support base is used to support the phase-shifting rack 1 , the frequency-selective mechanism 2 and the phase-shifting mechanism 3 .

[0046] The basic design principle of the frequency-selective phase shifting device is further explained below through an operation embodiment of the frequency-selective phase shifting device.

[0047] refer to Figure 1 , set the position where the phase-shift gear 23 is located outside the first phase-shift rack 1 as the initial state. The initial state is only a reference state for this operation and can be set according to specific circumstances. Set this operation to phase the antenna of the corresponding frequency band of the third phase-shift rack 1, and the phase-shift component serves as the target phase-shift rack 1A for this operation. The forward rotation or reverse rotation mentioned in the present invention is a relative concept and is not intended to limit the core of the invention.

[0048] First, the phase-shifting gear 23 is moved to the position corresponding to the target phase-shifting rack 1A:

[0049] The second motor 32 is not driven, only the first motor 24 is driven to rotate forward, and the driving gear 22 is driven to rotate in the reverse direction through the first gear train 25. The driving gear 22 further drives the transmission screw 21 constituting the transmission screw mechanism to pass through the inner hole of the driving gear 31 to move axially in a straight line. The transmission screw 21 drives the phase shifting gear 23 fixed at its end to move in the same direction until the phase shifting gear 23 meshes with the target phase shifting rack 1A, as shown in FIG. Figure 3 As shown, the driving of the first motor 24 is stopped. This operation step can select the phase shift rack 1 of the corresponding frequency band of the frequency selection phase shifting device, so as to perform phase adjustment on the antenna of the frequency band in the next step.

[0050] Secondly, the target phase-shift rack 1A is phase-controlled:

[0051] According to the needs of phase adjustment, that is, according to whether the target phase-shift rack 1A needs to move up or down, it is decided to drive the second motor 32 to rotate forward or reversely. When the second motor 32 is set to rotate forward, the phase-shift rack 1 moves downward. The second motor 32 is driven to rotate forward, and the driving gear 31 is driven to rotate reversely through the second gear train 33. At the same time, the first motor 24 is driven to rotate forward, and the driving gear 22 is driven to rotate reversely through the first gear train 25, so that the transmission screw 21 and the driving gear 22 rotate reversely at the same time. Therefore, the axial direction of the transmission screw 21 remains stationary and only rotates circumferentially in the reverse direction, thereby driving the phase-shift gear 23 to rotate reversely at the target phase-shift rack 1A, and driving the target phase-shift rack 1A to move downward. When the displacement of the target phase-shift rack 1A moving downward meets the displacement required for the phase adjustment amount of the antenna in the corresponding frequency band, as shown in FIG. Figure 4 As shown, the driving of the first motor 24 and the second motor 32 is stopped at the same time.

[0052] Then, restore the initial state.

[0053] Only the first motor 24 is driven to rotate in the reverse direction, and the transmission screw 21 is driven to drive the phase-shifting gear 23 to gradually disengage from the target phase-shifting rack 1A until it moves to the initial state, and the driving of the first motor 24 is stopped. The phase-shifting gear 23 is disengaged from the target phase-shifting rack 1A and returned to the initial state to avoid unnecessary phase shifting actions of the target phase-shifting rack 1A and other phase-shifting racks 1 due to operational errors or other reasons.

[0054] Of course, before restoring the initial state, if you continue to phase adjust the antennas in other frequency bands, such as Figure 5 As shown, the target phase shifting component is the last phase shifting rack 1B, repeat the above operation, the phase shifting gear 23 moves to the last phase shifting rack 1B, and meshes with it, and the phase shifting rack is moved up or down according to the phase adjustment requirements of the corresponding antenna of the phase shifting rack. It is also possible to restore the frequency selection phase shifting device to the initial state, and then perform the phase shifting operation on the next target phase shifting rack 1B. These operation sequences can be flexibly operated according to specific needs without departing from the core technology of the present invention, and the present invention does not limit this.

[0055] In the embodiment shown in the drawings of the present invention, the multiple phase-shift racks 1 are arranged on the same side of the axial direction of the transmission screw 21. In other embodiments, the frequency-selective phase-shifting device can also be provided with two rows of phase-shift racks 1, which are arranged on both sides of the axial direction of the transmission screw 21. The two rows of phase-shift racks are staggered so that the phase-shifting gear 23 can only mesh with one of the phase-shift racks 1 in one row of the phase-shift racks at a time. The number of phase-shift racks 1 can be set according to the specific requirements of the antenna frequency-selective phase-shifting device, and is not limited here.

[0056] In the above embodiment, the frequency-selective phase-shifting device is provided with only one phase-shifting gear 23. In other embodiments, two phase-shifting gears 23 may be provided on the transmission screw 21. The two phase-shifting gears 23 share the transmission screw 21, and only one phase-shifting gear 23 is meshed with the phase-shifting rack 1 at a time. In this regard, those skilled in the art can flexibly change different embodiments according to the creative spirit of the present invention, and will not be elaborated on.

[0057] The present invention further provides a multi-frequency antenna, comprising a plurality of phase shifting components corresponding to a plurality of frequency bands, and also comprising the above-mentioned frequency-selective phase shifting device, wherein each of the phase shifting components has a corresponding phase shifting rack 1 in the frequency-selective phase shifting device and is arranged in linkage therewith, so that the multi-frequency antenna has the function of phase modulation control of a signal in any frequency band.

[0058] In summary, the present invention optimizes the frequency selection and phase shifting device required for phase modulation, has a simple structure, and can more stably and easily realize the phase modulation control of any frequency band signal in the multi-frequency antenna, meeting the requirements of having a simple and lightweight frequency selection and phase shifting device as the frequency band of the antenna continues to increase, thereby improving the reliability of the multi-frequency antenna.

[0059] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the above features are replaced with the technical features with similar functions invented in the present invention (but not limited to) to form a technical solution.

Claims

1. A frequency-selective phase-shifting device, comprising phase-shifting racks corresponding to a plurality of frequency bands arranged side by side, a frequency-selecting mechanism which is controlled by a driving torque to select a phase-shifting rack of one frequency band, and a phase-shifting mechanism which is controlled by a driving torque to perform phase-shifting control on the selected phase-shifting rack, characterized in that: The frequency selection mechanism comprises a transmission screw axially arranged parallel to the arrangement direction of the plurality of phase-shifting racks, a driving gear threadedly arranged with the transmission screw, and a phase-shifting gear fixed on the transmission screw, wherein the driving gear is used to drive the transmission screw to move linearly along the arrangement direction, so that the transmission screw drives the phase-shifting gear to mesh with the phase-shifting rack of any frequency band; The phase shift mechanism comprises a driving gear sleeved on the transmission screw, the driving gear is used to drive the transmission screw to rotate circumferentially, so that the phase shift gear drives the phase shift rack meshing with it to move; The transmission screw is provided with at least one anti-rotation groove, which is arranged through the transmission screw in the axial direction, and the inner hole of the driving gear is provided with matching locking teeth corresponding to the anti-rotation groove.

2. The frequency-selective phase shifting device according to claim 1, characterized in that: The cross section of the anti-rotation groove is in an arc segment shape, a regular polygon shape, or an irregular polygon shape, and the shape of the cross section of the latch tooth corresponds to the shape of the cross section of the anti-rotation groove.

3. The frequency-selective phase shifting device according to claim 1, characterized in that: The central axis of the phase-shifting gear coincides with the central axis of the transmission screw, and the phase-shifting gear is fixedly sleeved on the transmission screw.

4. The frequency-selective phase shifting device according to claim 3, characterized in that: The phase-shifting gear and the transmission screw are integrally formed.

5. The frequency-selective phase shifting device according to claim 1, characterized in that: The frequency selection mechanism further includes a first motor, which drives the driving gear to rotate through a first gear train. The phase shifting mechanism further includes a second motor, which drives the driving gear to rotate through a second gear train.

6. The frequency-selective phase shifting device according to claim 1, characterized in that: The frequency-selective phase-shifting device further comprises a support base, and the support base is used to support the phase-shifting rack, the frequency-selective mechanism and the phase-shifting mechanism.

7. The frequency-selective phase shifting device according to claim 1 or 6, characterized in that: Support frames are respectively sleeved on both ends of the phase-shifting rack in the length direction, and a channel for the phase-shifting rack to move is formed between the two support frames.

8. The frequency-selective phase shifting device according to claim 1, characterized in that: The frequency-selective phase-shifting device is provided with two rows of phase-shifting racks, which are arranged on both sides of the axial direction of the transmission screw, and the two rows of phase-shifting racks are staggered.

9. A multi-frequency antenna, comprising a plurality of phase shifting components corresponding to a plurality of frequency bands, characterized in that: It comprises the frequency-selective phase-shifting device as claimed in any one of claims 1 to 8, and each of the phase-shifting components has a corresponding phase-shifting rack in the frequency-selective phase-shifting device and is arranged in linkage therewith.

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