Phase shifter

Abstract

This phase shifter is provided with a body part and a moving plate as constituents of a waveguide. A cross section perpendicular to the direction of the tube axis of the waveguide has a rectangular shape having a first side and a second side shorter than the first side. The moving plate forms an inner surface of the waveguide perpendicular to the first side, and is movable relative to the body part in a direction parallel to the first side. A phase difference of the phase shifter is determined according to the position of the moving plate with respect to the body part in a direction parallel to the first side.

Description

phase shifter

[0001] The present invention relates to a waveguide phase shifter.

[0002] Patent Document 1 discloses a transmission waveguide having a constricted portion. The constricted portion of the transmission waveguide has a major axis dimension that is narrower than the other portions of the transmission waveguide. This allows the wavelength within the transmission waveguide to be changed at the constricted portion, thereby adjusting the propagation phase at the output portion of the transmission waveguide.

[0003] Japanese Utility Model Application Laid-Open Publication No. 4-123602

[0004] The constricted portion of the transmission waveguide disclosed in Patent Document 1 has a simple structure and functions as a phase shifter. However, the phase difference of the phase shifter formed by the constricted portion of the transmission waveguide, i.e., the amount by which the phase shifter changes the phase of the transmission wave, is not variable. In other words, the phase difference of the phase shifter formed by the constricted portion of the transmission waveguide cannot be changed by external control.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a waveguide type phase shifter that has a simple structure and is capable of varying the phase difference.

[0006] The phase shifter of the present invention is a phase shifter comprising a main body and a movable plate that constitute a waveguide, wherein a cross section perpendicular to the direction of the tube axis of the waveguide has a rectangular shape having a first side and a second side that is shorter than the first side, the movable plate forms the inner surface of the waveguide that is perpendicular to the first side, and is movable relative to the main body in a direction parallel to the first side, and the phase difference of the phase shifter is determined depending on the position of the movable plate relative to the main body in the direction parallel to the first side.

[0007] According to the present invention, a waveguide type phase shifter with a simple structure and variable phase difference can be realized.

[0008] FIG. 1 is a perspective view of the appearance of a phase shifter according to an embodiment. FIG. 2 is a side view of the phase shifter according to an embodiment. FIGS. 3A and 3B are cross-sectional views of the phase shifter according to an embodiment. FIG. 4 is a perspective view showing an end of a moving plate in the direction of the waveguide axis. FIG. 5 is a diagram showing an example of frequency characteristics of the amplitude of S parameters S11 and S21 of the phase shifter. FIG. 6 is a diagram showing an example of frequency characteristics of the phase of S parameter S21 of the phase shifter. FIG. 7 is a diagram showing an example of the intensity of an electric field excited in the phase shifter. FIG. 8 is a diagram showing an example of the intensity of an electric field excited in the phase shifter. FIG. 9 is a diagram showing an example of change in the phase of S parameter S21 of the phase shifter according to change in Δa. FIG. 10 is a diagram showing an example of change in the amplitude of S parameter S21 of the phase shifter according to change in Δa. FIG. 11 is a diagram showing an example of change in the amplitude of S parameter S11 of the phase shifter according to change in Δa.

[0009] Fig. 1 is a perspective view of the appearance of a phase shifter according to an embodiment. Fig. 2 is a side view of the phase shifter according to an embodiment. Fig. 3(A) and Fig. 3(B) are cross-sectional views of the phase shifter according to an embodiment. Fig. 3(A) shows a cross section parallel to the xz plane. Fig. 3(B) shows a cross section parallel to the xy plane.

[0010] The phase shifter comprises a main body 1 and a moving plate 2. The main body 1 and the moving plate 2 constitute a waveguide 3. A cross section of the waveguide 3 perpendicular to the direction of its tube axis 33 has the shape of a rectangle having a first side 31 and a second side 32 that is shorter than the first side 31. The moving plate 2 forms the inner surface of the waveguide 3 perpendicular to the first side 31, and is movable relative to the main body 1 in a direction parallel to the first side 31. The phase difference of the phase shifter, i.e., the amount by which the phase shifter changes the phase of the transmission wave, is determined according to the position of the moving plate 2 relative to the main body 1 in the direction parallel to the first side 31, as will be described later.

[0011] In this specification, the x direction is taken as a direction parallel to the first side 31 , the y direction is taken as a direction parallel to the second side 32 , and the z direction is taken as a direction of the tube axis 33 .

[0012] The main body 1 is generally in the form of a hollow rectangular parallelepiped, and has a top 11, a bottom 12, a front portion 13, a rear portion 14, and side portions 15 and 16. The main body 1 further has flanged open ends 17 at the front portion 13 and the rear portion 14.

[0013] The phase shifter is not necessarily arranged so that the direction from the top 11 to the bottom 12 faces vertically downward, but may be arranged in any direction relative to the vertical direction.

[0014] 3A and 3B, the movable plate 2 is disposed in the internal space of the main body 1. A main surface 21 of the movable plate 2 is parallel to the main surfaces of the top portion 11 and the bottom portion 12. An end surface 22 of the movable plate 2 substantially abuts or is close to the front portion 13, the rear portion 14, and the side portions 15 and 16.

[0015] As shown in Fig. 1, the main body 1 is formed, for example, by joining a metal plate member 18 that constitutes the bottom 12 to a metal member 19 that constitutes the other parts with screws. As shown in Fig. 3(A), the movable plate 2 is formed, for example, by joining two metal plate members 23 and 24 with screws 25. However, the main body 1 and the movable plate 2 may be formed by other methods.

[0016] As shown in FIGS. 3A and 3B , the waveguide 3 is more specifically composed of the upper portion 11 of the main body 1, the side portions 15 and 16 of the main body 1, and the movable plate 2. The waveguide 3 has a first port 36 and a second port 37 at both ends in the direction of the tube axis 33. The length of the first side 31 of the waveguide 3 changes with the movement of the movable plate 2. The length of the first side 31 of the waveguide 3 is expressed as a + Δa, where a represents the standard length of the first side 31. Δa represents the difference between the length of the first side 31 and the standard length of the first side 31 and is a positive value. The second side 32 of the waveguide 3 is shorter than the first side 31 of the waveguide 3, regardless of the movement of the movable plate 2. The length from the first port 36 to the second port 37 of the waveguide 3 is expressed as L. The waveguide 3 is designed to excite only a transmission wave in TE10 mode at the operating frequency.

[0017] 1, 2, and 3A, the phase shifter further includes an adjustment screw 41 attached to the moving plate 2 and protruding outside the main body 1. The position of the moving plate 2 is adjusted, for example, by turning a nut (not shown) attached to the adjustment screw 41 to move the adjustment screw 41 relative to the main body 1. However, the position of the moving plate 2 may be adjusted by other methods. Also, the position of the moving plate 2 may be automatically adjusted by electronic control, for example, by turning a nut attached to the adjustment screw 41 using a servo motor.

[0018] 4 is a perspective view showing the end of the moving plate in the direction of the tube axis of the waveguide. As shown in FIGS. 3A and 4, the phase shifter further includes a metallic elastic member 42 provided at the end of the moving plate 2 in the direction of the tube axis 33 so as to contact the inner surface of the main body 1. The elastic member 42 is fitted into a recess formed in the end surface 22 of the moving plate 2 and protrudes slightly from the end surface 22 of the moving plate 2. The elastic member 42 fills the gap between the main body 1 and the moving plate 2, preventing the electromagnetic field in the waveguide 3 from leaking out of the waveguide 3.

[0019] Next, a description will be given of the relationship between the position of the moving plate 2 relative to the main body 1 and the phase difference of the phase shifter. The phase difference of the phase shifter is expressed by the following formula.

[0020]

[0021] Here, Δφ represents the phase difference of the phase shifter. g (α) represents the guide wavelength of the TE10 mode of the waveguide 3 when the length of the first side 31 of the waveguide 3 is α. c (α) represents the cutoff wavelength of the TE10 mode of the waveguide 3 when the length of the first side 31 of the waveguide 3 is α. f represents the operating frequency. ε and μ represent the permittivity and permeability of the medium in the waveguide 3, respectively.

[0022] Therefore, 2πL / λ g (a) is equal to the difference in phase between the transmission wave at the first port 36 of the waveguide 3 and the transmission wave at the second port 37 of the waveguide 3 when the length of the first side 31 of the waveguide 3 is equal to the standard length. g(a+Δa) is equal to the difference between the phase of the transmission wave at the first port 36 of the waveguide 3 and the phase of the transmission wave at the second port 37 of the waveguide 3. Therefore, the right-hand side of the first equation above is equal to the change in the phase of the transmission wave output from the phase shifter relative to the phase of the transmission wave output from the phase shifter when the length of the first side 31 of the waveguide 3 is equal to the standard length, and therefore equal to the phase difference of the phase shifter.

[0023] In this way, the phase difference of the phase shifter is determined according to Δa, and therefore according to the position of the moving plate 2 relative to the main body 1 .

[0024] The range of Δa that can be taken is determined by the condition for exciting only the transmission wave of the TE10 mode for the frequency used, i.e., the condition that λ is lower than the cutoff wavelength of the lowest TE10 mode and higher than the cutoff wavelength of the next lowest mode, regardless of changes in Δa, and is 0<Δa<a.

[0025] 5 is a diagram showing an example of the frequency characteristics of the amplitudes of the S parameters S11 and S21 of a phase shifter. In the range of 25 GHz to 30 GHz, the amplitude of the S parameter S11 (ratio of reflected to incident) is less than -10 dB. In the range of 23 GHz to 30 GHz, the amplitude of the S parameter S21 (ratio of transmitted to incident) is in the range of -1.49 dB to -0.89 dB. In this way, the reflection in the phase shifter is kept low, and the insertion loss of the phase shifter is also kept low.

[0026] 6 is a diagram showing an example of the frequency characteristic of the phase of the S parameter S21 of the phase shifter. In the range of 23 GHz to 30 GHz, the frequency characteristic of the phase of the S parameter S21 has excellent linearity. Therefore, the frequency characteristic of the phase difference of the phase shifter also has excellent linearity.

[0027] 7 and 8 are diagrams showing examples of the intensity of the electric field excited in the phase shifter. FIGS. 7 and 8 show cross sections of the phase shifter parallel to the xz plane. As shown in region 51 in FIGS. 3A and 7, a transmission wave is excited in the waveguide 3. As shown in region 52 in FIGS. 3A and 7, the electromagnetic field hardly leaks outside the waveguide 3. As shown in region 53 in FIGS. 3A and 8, even near the first port 36 of the waveguide 3, the elastic member 42 blocks the gap between the main body 1 and the moving plate 2, so the electromagnetic field hardly leaks from the gap between the main body 1 and the moving plate 2. Although not shown in the figures, even near the second port 37 of the waveguide 3, the electromagnetic field hardly leaks from the gap between the main body 1 and the moving plate 2.

[0028] Fig. 9 is a diagram showing an example of a change in the phase of the S parameter S21 of the phase shifter in response to a change in Δa. By looking at the change in the phase of the S parameter S21 of the phase shifter (the ratio of the transmitted component to the incident component), it is possible to know the change in the phase difference of the phase shifter. Fig. 10 is a diagram showing an example of a change in the amplitude of the S parameter S21 of the phase shifter in response to a change in Δa. Fig. 11 is a diagram showing an example of a change in the amplitude of the S parameter S11 of the phase shifter in response to a change in Δa. Figs. 9 to 11 show characteristics when the operating frequency is 28 GHz.

[0029] As shown in FIG. 9, when Δa changes from 0 mm to 1.8 mm, the phase of the S parameter S21 changes by 360 degrees. When Δa changes from 0 mm to 3 mm, the phase of the S parameter S21 changes by 420 degrees. Therefore, the phase difference of the phase shifter is variable over a range of 360 degrees or more, particularly within a range of 420 degrees. As shown in FIG. 10, the amplitude of the S parameter S21 is maintained greater than −0.2 dB. In other words, the insertion loss of the phase shifter is maintained less than 0.2 dB. As shown in FIG. 11, the amplitude of the S parameter S11 is maintained approximately less than −15 dB. In this way, even when Δa changes, the reflection in the phase shifter is kept low, and the insertion loss of the phase shifter is also kept low.

[0030] This phase shifter is used in products such as microwave or millimeter-wave components, automatic matching boxes, microwave heating devices, and phased arrays. In the case of automatic matching boxes, the phase shifter is used for impedance matching by adjusting the phase of the reflection coefficient. In the case of microwave heating devices, the phase shifter is used for impedance matching according to the load that changes depending on the heated object. In the case of phased arrays, the phase shifter is used to adjust the excitation phase of each antenna element.

[0031] According to this embodiment, the phase shifter includes a main body 1 and a movable plate 2 that constitute a waveguide 3. The movable plate 2 is movable relative to the main body 1 in a direction parallel to a first side 31 of the waveguide 3. When the movable plate 2 moves, the in-guide wavelength of the transmission wave excited in the waveguide 3 changes, and the difference between the phase of the transmission wave at the first port 36 of the waveguide 3 and the phase of the transmission wave at the second port 37 of the waveguide 3 changes. As a result, the phase difference of the phase shifter is determined according to the position of the movable plate 2 relative to the main body 1 in the direction parallel to the first side 31. Therefore, a waveguide-type phase shifter with a simple structure and variable phase difference can be realized.

[0032] Conventional semiconductor phase shifters are composed of integrated circuits formed on a semiconductor substrate, and therefore have low power resistance of only a few mW. Therefore, semiconductor phase shifters are not suitable for shifting the phase of high-power transmission waves of several kW, and in particular cannot be directly connected to magnetrons that generate high-power microwaves. Furthermore, because semiconductor phase shifters are composed of integrated circuits as described above, they have a large insertion loss. This also makes semiconductor phase shifters unsuitable for power transmission.

[0033] On the other hand, conventional waveguide phase shifters usually have a smaller insertion loss than conventional semiconductor phase shifters, but still have an insertion loss of about 0.3 dB. Furthermore, conventional waveguide phase shifters have a narrow phase shift width, usually only 180°. Therefore, to shift the phase of a transmission wave by a value greater than the phase shift width of the phase shifter, multiple phase shifters must be connected in series. In addition, conventional waveguide phase shifters have a complex structure and are unable to quickly change their phase difference.

[0034] In contrast to such conventional phase shifters, the present phase shifter is of a waveguide type and has high power durability.

[0035] Furthermore, the present phase shifter can maintain an insertion loss of less than 0.2 dB, as shown in Fig. 10. That is, the present phase shifter can maintain an insertion loss smaller than not only conventional semiconductor phase shifters but also conventional waveguide phase shifters.

[0036] 9, this phase shifter has a phase shift width of 360 degrees, so that it is possible to provide any phase difference with just this one phase shifter.

[0037] As described above, the phase shifter is mainly composed of the main body 1 and the movable plate 2 that is movable relative to the main body 1, and has a simple structure.

[0038] Furthermore, in this phase shifter, the phase difference is changed by moving the movable plate 2 relative to the main body 1, so that the phase difference can be changed easily and quickly.

[0039] This phase shifter also includes a metallic elastic member 42 provided at the end of the moving plate 2 in the direction of the tube axis 33 so as to be in contact with the inner surface of the main body 1. Therefore, the elastic member 42 effectively closes the gap between the main body 1 and the moving plate 2 near the first port 36 and the second port 37 of the waveguide 3. This makes it possible to prevent the electromagnetic field excited in the waveguide 3 from leaking from the gap between the main body 1 and the moving plate 2.

[0040] As described above, the phase shifter of the present invention has many excellent advantages and is particularly suitable for phase shifting of high-power microwaves or millimeter waves.

[0041] The above description of the embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications that are equivalent to the scope of the claims and fall within the scope thereof.

[0042] 1: Main body 2: Moving plate 3: Waveguide 11: Upper part 12: Bottom part 13: Front part 14: Rear part 15: Side part 16: Side part 17: Open end 18: Plate member 19: Member 21: Main surface 22: End face 23: Plate member 24: Plate member 25: Screw 31: First side 32: Second side 33: Tube axis 36: First port 37: Second port 41: Adjusting screw 42: Elastic member

Claims

1. A phase shifter comprising a main body and a movable plate that constitute a waveguide, wherein a cross section perpendicular to the direction of the waveguide axis has a rectangular shape with a first side and a second side that is shorter than the first side, wherein the movable plate forms the inner surface of the waveguide that is perpendicular to the first side and is movable relative to the main body in a direction parallel to the first side, and wherein the phase difference of the phase shifter is determined depending on the position of the movable plate relative to the main body in the direction parallel to the first side.

2. A phase shifter according to claim 1, further comprising a metallic elastic member provided at an end of said moving plate in the direction of said tube axis so as to come into contact with the inner surface of said main body.

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