Phase shifter

Abstract

To provide a technique for reducing group delay error. 【Solution means】 A rectangular waveguide having a 0th part to an Nth part (N = 2×n, n is a predetermined integer of 2 or more) through which radio waves propagate, and the (p odd +2) part (p odd is an odd number of 3 or more (N-3) or less) is a part having a width of (p odd +2), and the width of the (p odd +2) is different from the width of the p odd th part, and the (p even +2) part (p even is an even number of 2 or more (N-2) or less) is a part having a width of (p even +2), and the width of the (p even +2) satisfies the relationship of (p even +2)=(p odd +2)+1 and is equal to the width of the (p odd +2). The width of the 0th part is the 0th width, the width of the 1st part is the 1st width different from the 0th width, and the width of the 2nd part is equal to the 1st width, a phase shifter.

Description

Technical Field

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

Background Art

[0002] Technological development related to satellite SAR (Synthetic Aperture Radar) has been progressing, and for example, an antenna equipped with a tournament power supply circuit has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In satellite SAR, in order to improve the resolution, it is necessary to widen the bandwidth of the antenna. However, the difference in electrical length in the tournament power supply circuit becomes a group delay error, which causes signal degradation such as deterioration of gain and radiation pattern as the frequency deviates from the center frequency. Such signal degradation due to group delay error is common not only in satellite SAR but also in antennas used for terrestrial communication such as antennas equipped in smartphones.

[0005] In view of the above circumstances, an object of the present invention is to provide a technique for reducing group delay error.

Means for Solving the Problems

[0006] One aspect of the present invention includes a rectangular waveguide having a 0th part to an Nth part (N = 2 × n, where n is a predetermined integer of 2 or more) through which radio waves propagate. The (p odd +2)th part (p odd is an odd number from 1 to (N - 3)) is a part having the width of the (p odd +2)th part, and the p oddThe width of (+2) is the p-th odd Unlike the width of, the (p even +2) part (p even is an even number between 2 and (N - 2)) is the (p even +2) width part, and the (p even +2) width is (p even +2)=(p odd +2)+1 satisfies the relationship of the (p odd +2) width, and the radio wave is the (q odd -2) part (q odd is an odd number between 3 and N) after propagating, and then propagates within the q odd part, where q odd =1 to q odd =N - 1 is repeated. After propagating within the (N - 1) part, it propagates through the 0th part, and then, after propagating within the q[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​A first explanatory diagram illustrating the second experiment in the embodiment. [Figure 7] A second explanatory diagram illustrating the second experiment in the embodiment. [Figure 8] A third explanatory diagram illustrating the second experiment in the embodiment. [Figure 9] A fourth explanatory diagram illustrating the second experiment in the embodiment. [Figure 10] A first explanatory diagram illustrating the third experiment in the embodiment. [Figure 11] A second explanatory diagram illustrating the third experiment in the embodiment. [Figure 12] A third explanatory diagram illustrating the third experiment in the embodiment. [Modes for carrying out the invention]

[0009] (Embodiment) Figure 1 is an explanatory diagram illustrating a phase shifter 1 of an embodiment. The phase shifter 1 includes a tube 10 through which radio waves propagate. The tube 10 is a rectangular waveguide. Therefore, the cross-sectional shape of the tube 10 perpendicular to the axis of the tube 10 (hereinafter referred to as the "propagation axis") is rectangular. In the example of Figure 1, the direction of the propagation axis is parallel to the direction of the X-axis in Figure 1. As radio waves propagate through the tube 10, the phase of the radio waves changes.

[0010] The tube 10 has at least a 0th section, a 1st section, a 2nd section, a 3rd section, and a 4th section. The 0th section is a part of the tube 10 with a width of the 0th section. The width refers to the length of the long side of the rectangular waveguide. That is, the shape of the cross-section perpendicular to the axis of the rectangular waveguide is rectangular as described above, and the width refers to the length of the long side of this rectangle.

[0011] In the example shown in Figure 1, the radio waves travel through the tube 10, reflecting repeatedly within the tube 10, in the positive direction of the X-axis. Arrow K1 in Figure 1 indicates the propagation direction of radio waves incident on the tube 10, and arrow K2 in Figure 1 indicates the propagation direction of radio waves emitted from the tube 10.

[0012] The first part is a portion of the pipe 10 with a width of the first width. The first width is different from the zero width. The second part is a portion of the pipe 10 with a width of the second width. The second width is equal to the first width.

[0013] The radio waves that enter the tube 10 propagate within the tube 10, first through the first section, then through the zero section, and then through the second section.

[0014] The difference between the 0th width and the 1st width is a predetermined difference based on a predetermined change in the phase of the radio waves that occurs as the radio waves propagate through the tube 10. Therefore, as the radio waves pass through the tube 10, their phase changes by a predetermined amount. An explanation using the mathematical formula for the phase change will be given later.

[0015] In the example in Figure 1, part 100 is an example of part 0, part 101 is an example of part 1, and part 102 is an example of part 2.

[0016] The third section is a part of the pipe 10 with a width of the third width. The third width is different from both the first width and the zero width. The fourth section is a part of the pipe 10 with a width of the fourth width. The fourth width is equal to the third width.

[0017] In the example in Figure 1, part 103 is an example of the third part, and part 104 is an example of the fourth part.

[0018] The radio waves that enter the tube 10 propagate within the tube 10, first through the first section, then through the third section, then through the zero section, then through the fourth section, and finally through the second section.

[0019] <1st part ~ Nth part> Up to this point, we have explained the case where the pipe 10 has five parts, from part 0 to part 4. However, the pipe 10 may also have parts 0 to N (N = 2 × n, where n is a predetermined integer of 2 or more).

[0020] No.(p odd +2) Part (p odd (1 or more and (N-3) or less odd numbers) is a part of tube 10, and the (p odd This is the part with a width of +2). odd The width of (+2) is the p odd It is different in width.

[0021] No.(p even +2) Part (p even (2 or more and (N-2) or less even numbers) is a part of tube 10, and the (p even This is the part with a width of +2). even The width of (+2) is (p even +2)=(p odd The (p)th that satisfies the relationship (+2)+1 odd The width is equal to (+2). Note that the second width is equal to the first width, as mentioned above.

[0022] In this case, the radio waves are (q odd -2) Inside the part (q odd After propagating (an odd number between 1 and N), the q odd The propagation within a region is called q odd =3 to q odd This process is repeated up to N-1, and after propagating within the (N-1)th region, it propagates through the 0th region, and then the qth region. even Within the part (q even After propagating (an even number between 1 and N), the (q even -2) Propagation within a site is called q even = N to q even Repeat until =4

[0023] <Regarding width> By the way, the first width only needs to be different from the zeroth width, and it can be longer or shorter than the zeroth width. So, first, let's explain an example of the relationship that widths zero to N satisfy when the first width is longer than the zeroth width.

[0024] <<An example of a relationship that is satisfied when the first width is longer than the zero width>> The widths from the 0th to the Nth width may, for example, satisfy the conditions for the 1st to the 4th width.

[0025] The first width condition is that the first width is longer than the zeroth width.

[0026] The second width condition is (p odd The width of (+2) is the p odd The condition is that it is shorter than the width of the first element and longer than the width of element 0.

[0027] The third condition is (p even The width of (p +2) is (p even +2)=(p odd The (p)th that satisfies the relationship (+2)+1 odd The condition is that the width is equal to (+2).

[0028] The fourth width condition is that the second width is equal to the first width.

[0029] Next, we will explain an example of a relationship that widths 0 through N satisfy when the first width is shorter than width 0.

[0030] <<An example of a relationship that is satisfied when the first width is shorter than the zero width>> When N is 4 or greater, the widths from the 0th width to the Nth width may satisfy, for example, the conditions for the 5th width to the 8th width.

[0031] The fifth width condition is that the first width is shorter than the zeroth width.

[0032] The sixth condition is the (p odd The width of (+2) is the p odd The condition is that it is longer than the width of the first element and shorter than the width of element 0.

[0033] The seventh condition is the (p even The width of (p +2) is (p even +2)=(p odd The (p)th that satisfies the relationship (+2)+1 odd The condition is that the width is equal to (+2).

[0034] The eighth condition is that the second width is equal to the first width.

[0035] <Regarding the length in the direction of the propagation axis> In the example of FIG. 1, "L" represents the length in the direction of the propagation axis of the 0th part. In the example of FIG. 1, "s" represents the length in the direction of the propagation axis of the 3rd part. As shown in the example of FIG. 1, the length of the 0th part may be longer than the lengths in the direction of the propagation axis of other parts (i.e., the 1st part to the Nth part).

[0036] Note that the lengths in the direction of the propagation axis of the 1st part to the Nth part may all be the same. The lengths in the direction of the propagation axis of the 1st part to the Nth part may be approximately one-fourth of the wavelength λ of the radio wave in the waveguide. g That is, the lengths in the direction of the propagation axis of the 1st part to the Nth part may be approximately the same as (1 / 4)λ. g

[0037] Note that the lengths in the direction of the propagation axis of the 1st part to the Nth part do not necessarily have to be all the same, and some may be different, or all may be different.

[0038] <Explanation using the mathematical formula of the phase change with N = 4 as an example and the effect exerted by the phase shifter 1> Here, taking the case of N = 4 as an example, the mathematical formula is used to explain the more details of the phase change and the effect exerted by the phase shifter 1.

[0039] The width of the 0th part is denoted as a predetermined width d0, the width of the 1st part is denoted as d1, and the width of the 3rd part is denoted as d2. Therefore, the width of the 2nd part is d1, and the width of the 4th part is d2. As described above, let the wavelength of the radio wave in vacuum be λ0. The width of the 3rd part is s as described above. The widths d0, d1, and d2 satisfy either one of the relationships d0 < d1 < d2 or d2 < d1 < d0.

[0040] The in-tube wavelength of the rectangular waveguide is determined according to the width of the waveguide. In view of this, by changing the width d2 and the length L, the passing phase can be arbitrarily changed. The in-tube wavelength λ​g When the length of the long side of the rectangular waveguide is a, it is expressed by the following equation (1).

[0041]

number

[0042] Therefore, the wavelength λ inside the tube at the second location g ' is represented by the following equation (2).

[0043]

number

[0044] Therefore, when N=4, the radio waves propagating through tube 10 undergo a phase change φ represented by the following equation (3). That is, the phase passing through tube 10 is represented by the following equation (3).

[0045]

number

[0046] Therefore, the phase shifter 1 can impart a phase change to the incoming radio waves.

[0047] Equation (3) shows that any phase difference can be obtained by changing L and d2, but the values ​​of L and d2 are predetermined before assembling the phase shifter 1. Therefore, the assembled phase shifter 1 imparts a predetermined phase change to the incident radio wave. However, if the desired phase change is known in advance, a phase shifter 1 that provides a phase change suitable for the purpose can be created depending on the combination of L and d2.

[0048] <Further effects> Length s is the wavelength λ inside the tube. gBy reducing it to approximately one-quarter, reflections in the two-stage step section cancel each other out, resulting in low reflection characteristics. The two-stage step section is the part where the width of the waveguide changes. More specifically, it is a set of a section where the width changes from d0 to d1 (hereinafter referred to as the "first step") and a section where the width changes from d1 to d2 (hereinafter referred to as the "second step"). Therefore, in the example in Figure 1, the boundary between section 100 and section 104 is an example of the first step, and the boundary between section 104 and section 102 is an example of the second step.

[0049] Furthermore, reflection occurs in the section of a waveguide where the width changes. A reflection from a section approximately one-quarter wavelength away from a certain point will have a round-trip reflection of half a wavelength, resulting in a phase reversal. Therefore, reflections from two different sections approximately one-quarter wavelength apart will be in opposite phases and cancel each other out. The round-trip distance of the section of length s is 2s. When s = λ / 4, the phase change is given by φ = 2πL / λ. Substituting L = 2s = λ / 2, we get φ = π, which shows that the phase is reversed. The section of length s is section 103 in Figure 1.

[0050] Furthermore, since tube 10 can be installed in the straight waveguide section of the tournament power supply circuit, it does not take up extra space. In addition, because of its quarter-wavelength step structure, it has low reflection and low loss, so when the phase shifter 1 is used in the tournament power supply circuit, it is possible to minimize the impact on the overall RF performance.

[0051] (Experimental results) This section describes an experiment involving phase shifter 1 and an example of its results. In the experiment, the electromagnetic field was measured using near-field measurements.

[0052] <Experiment 1> Figure 2 is a first explanatory diagram illustrating the first experiment in the embodiment. Figure 2 shows a schematic diagram of the antenna 900. The antenna 900 includes a feed circuit 90. The feed circuit 90 is a tournament feed circuit.

[0053] In the diagram, the circuit indicated by "τ" represents a τ junction (tournament distribution circuit). Therefore, the power supply circuit 90 is D3 M D2A M D2B M D3 P D2A P and D2B P It features six τ junctions.

[0054] In the diagram, the circuit labeled "MAGIC T" is capable of distributing power in three directions. However, one of these three directions is terminated. Therefore, the circuit labeled "MAGIC T" distributes power in two directions.

[0055] The feed circuit 90 is connected to a total of seven sub-arrays: 3M, 2M, 1M, 0, 1P, 2P, and 3P. In other words, the antenna 900 comprises the feed circuit 90 and a total of seven sub-arrays: 3M, 2M, 1M, 0, 1P, 2P, and 3P. Since the feed circuit 90 is connected to a total of seven sub-arrays, the feed circuit 90 supplies power to these seven sub-arrays. Specifically, the power is supplied by an electromagnetic field. Note that the sub-arrays were array antennas consisting of multiple antenna elements.

[0056] "W[-3]" represents the excitation amplitude of sub-array 3M. "W[-2]" represents the excitation amplitude of sub-array 2M. "W[-1]" represents the excitation amplitude of sub-array 1M. "W[0]" represents the excitation amplitude of sub-array 0. "W[1]" represents the excitation amplitude of sub-array 1P. "W[2]" represents the excitation amplitude of sub-array 2P. "W[3]" represents the excitation amplitude of sub-array 3P.

[0057] The τ junction is a waveguide 2-way distribution circuit with one input port and two output ports. The τ junction distributes power to one of the two output ports at a predetermined distribution ratio by changing various dimensions such as the input wall offset, input wall length, output wall offset, and output wall length.

[0058] This section describes the power distribution ratio at each tau junction of Antenna 900. τ Junction D2A M The power distribution ratio of the two outputs is W[-2]:W[-3]. τ Junction D2A P The power distribution ratio of the two outputs is W[-2]:W[-3]. τ Junction D2B M The power distribution ratio of the two outputs is W[-1]:W[0] / 2. τ Junction D2B P The power distribution ratio of the two outputs is W[1]:W[0] / 2. τ Junction D3 M The power distribution ratio of the two outputs is W[-1]+W[0] / 2:W[-2]+W[-3]. τ Junction D3 P The power distribution ratio of the two outputs is W[1]+W[0] / 2:W[2]+W[3].

[0059] In antenna 900, the excitation amplitude of the antenna elements is tapered. Tapering adjusts the radiation pattern, such as suppressing side lobes. Weighting methods such as Taylor distributions and Chebyshev distributions may be used for tapering. Various types of tapering are possible by changing the distribution ratio of the feeding circuit 90 that supplies power to the sub-array. The distribution ratio of the feeding circuit 90 that supplies power to the sub-array is changed by changing the distribution ratio of the two outputs at each tau junction.

[0060] However, the type of tapering to be performed is determined during the design of the antenna 900 and cannot be changed after the antenna 900 is assembled. Therefore, the distribution ratio is also a predetermined value before the antenna 900 is assembled and cannot be changed after the antenna 900 is assembled.

[0061] Figure 3 is a second explanatory diagram illustrating the first experiment in the embodiment. More specifically, Figure 3 is a diagram illustrating the tapering used in the experiment. Figure 3 shows the excitation amplitude of the subarrays when there are 7 subarrays, 10 antenna elements in each subarray, and a sidelobe -20dB Chebyshev distribution is used as weighting.

[0062] The horizontal axis of the graph in Figure 3 represents the spatial position of each sub-array. The vertical axis of the graph in Figure 3 represents the normalized excitation amplitude of each sub-array. In the graph in Figure 3, the black circles represent the excitation amplitude of the antenna elements. The graph in Figure 3 shows guide lines for the excitation amplitude of the sub-arrays.

[0063] Figure 4 is a third explanatory diagram illustrating the first experiment in the embodiment. Figure 4 shows the near-field distribution obtained as a result of near-field measurements performed on the subarray of antenna 900 in Figure 2.

[0064] Figure 4 shows two results, R001 and R002, along with color bars. Result R001 is an example of a near-field measurement result without tapering. Result R002 is an example of a near-field measurement result with tapering. Both near-field measurements were performed at 9.65 GHz.

[0065] Figure 5 is a fourth explanatory diagram illustrating the first experiment in the embodiment. Figure 5 shows the radiation pattern calculated from the results in Figure 4. "Without Tapering" shows the results when tapering is not performed. "With Tapering" shows the results when tapering is performed. Figure 5 shows that with tapering the side lobes are lower compared to without tapering, and a first side lobe level of approximately -20 dB is obtained.

[0066] The dimensional accuracy of machine cutting is approximately 50 μm. Therefore, in the case of large antennas with a total feed path length of several meters, errors in dimensional accuracy can accumulate, leading to deviations from the designed phase value and potentially resulting in significant errors. Furthermore, in the case of deployable satellite antennas, the antenna alignment in orbit deviates from the ideal value due to factors such as assembly angle errors. In addition, in orbit, the temperature difference between the surface heated by sunlight and the surface not exposed to sunlight causes thermal distortion in the antenna, which also leads to alignment deviations. These error factors result in phase errors in the overall excitation distribution of the antenna, leading to a deterioration of the radiation pattern.

[0067] However, incorporating tapering into the design allows for a more error-resistant design that anticipates sidelobe degradation. The resulting antenna is fed by a tournament-fed circuit and satisfies at least the condition that the excitation amplitude of at least some sub-arrays differs from that of others. Such an antenna is more resistant to radiation pattern degradation than an antenna that does not meet this condition. Therefore, this contributes to improving the reliability of performance for satellite-mounted antennas in harsh environmental conditions.

[0068] <Experiment 2> In the first experiment, the effect of tapering the antenna 900 was verified, demonstrating that tapering can suppress side lobes. Next, we present experimental results on a technique for reducing phase errors without necessarily tapering the antenna 900.

[0069] Figure 6 is the first explanatory diagram illustrating the second experiment in the embodiment. Hereafter, components having the same function as antenna 900 will be given the same reference numerals as in Figure 5, and their explanation will be omitted. Figure 6 shows a schematic diagram of antenna 900a, along with the path difference. Antenna 900a differs from antenna 900 in that it has a feed circuit 90a instead of feed circuit 90. Feed circuit 90a differs from feed circuit 90 in that it has a phase shifter 1.

[0070] The phase shifter 1 of the power supply circuit 90a comprises a tube 10 composed of a 0th section, a 1st section, a 2nd section, a 3rd section, and a 4th section, and the tube 10 is a rectangular waveguide that satisfies the 1st to 4th width conditions.

[0071] In the diagram, "d" indicates that there is a path difference d at each location where it is indicated. In the example in Figure 6, for simplicity of explanation, the path difference d is assumed to be the same regardless of the location. "H" indicates the phase shifter 1. As mentioned above, for simplicity of explanation, the path difference d is assumed to be the same regardless of the location, so the phase shifter 1 provided by antenna 900a provides a path difference d regardless of its location.

[0072] Antenna 900a is used as phase shifter 1, A1 M A2 M A3 M A3 P A2 P and A1 P It is equipped with six phase shifters 1. As described above, each one provides a path difference d. The path difference provided by the phase shifter 1 is the value obtained by converting the phase difference provided by the phase shifter 1 into the length of the path.

[0073] This section explains the path difference for each sub-array of antenna 900a when phase shifter 1 is not present. Sub-array 3M is +2d. Sub-array 2M is +1d. Sub-array 1M is 0. Sub-array 0 is +1d. Sub-array 1P is 0. Sub-array 2P is +1d. Sub-array 3P is +2d.

[0074] Thus, without phase shifter 1, the path differences of each subarray are not necessarily the same. However, as can be seen from Figure 6, the path difference becomes +2d in all cases due to the presence of phase shifter 1.

[0075] Figure 7 is a second explanatory diagram illustrating a second experiment in the embodiment. Figure 7 is a diagram that more specifically explains how the phase shifter 1 is used in Figure 6. More specifically, Figure 7 is an explanatory diagram that illustrates an example of the relationship between the tube 10 of the phase shifter 1 and the τ junction. Therefore, Figure 7 can be said to be a diagram that illustrates an example of use when the phase shifter 1 and the distribution circuit are used together.

[0076] In Figure 7, “Pout1” indicates one of the two output ports of the τ junction, and “Pout2” indicates the other. “Pin” indicates the input port of the τ junction. Figure 7 shows that the tube connecting the input port “Pin” and the output port “Pout2” has been replaced with tube 10.

[0077] In the example in Figure 7, there are constraints on the positions of the two output ports, with L1 > L2. Output ports "Pout1" and "Pout2" are connected to a sub-array or the next-stage distribution circuit.

[0078] The following describes the S-parameter pass-through characteristics from input port "Pin" to output port "Pout1". out1、in This is denoted as follows: The pass-through characteristics of the S-parameters from the input port "Pin" to the output port "Pout2" are expressed as S. out2、in This is how it is written.

[0079] Since the output ports "Pout1" and "Pout2" are connected to the sub-array or the distribution circuit in the next stage, within the used bandwidth, the transmission phase arg(S out1、in ) and the transmission phase arg(S out2、in ) must be equal. Note that the definition of the transmission phase arg(S out1、in ) is the argument of the complex number S out1、in , and the definition of the transmission phase arg(S out2、in ) is the argument of the complex number S out2、in .

[0080] Since L1 > L2, without the pipe 10, the transmission phase and group delay characteristics to the output port "Pout1" and the transmission phase and group delay characteristics to the output port "Pout2" will be different. On the other hand, as shown in FIG. 7, when there is a pipe 10 in which dimensions such as L and d2 are designed to predetermined values, the transmission phase <S out2、in is adjusted.

[0081] By the way, when the dispersion characteristics of the straight waveguide section and the pipe 10 are different, it may not be possible to completely match the phases within the frequency band. That is, even if the transmission phases are matched at the center frequency, a phase difference may occur at frequencies other than the center frequency. The technique for reducing this phase difference will be described next. This technique uses the relationship between the transmission phase arg(S out1、in ) and the transmission phase arg(S out2、in ).

[0082] There is an ambiguity of 2kπ (k is an integer) between the transmission phase arg(S out1、in ) and the transmission phase arg(S out2、in ). Therefore, when arg(S out1、in ) - arg(S out2、in ) = 2kπ at the center frequency, there are multiple combinations of L and d2 that satisfy this relationship.

[0083] Therefore, by using a combination of L and d2 that satisfies both the first and second phase conditions, the phase difference occurring at frequencies other than the center frequency is reduced. As a result, an antenna with a broadband and higher phase-frequency characteristic with greater flatness is realized. The first phase condition is that the pass phase at the center frequency matches between output port "Pout1" and output port "Pout2". The second phase condition is that, due to the pass phase characteristics of tube 10, the first phase condition is satisfied, and the pass phase difference between Pout1 and Pout2 at frequencies other than the center frequency is canceled out.

[0084] Figure 8 is a third explanatory diagram illustrating the second experiment in the embodiment. Figure 9 is a fourth explanatory diagram illustrating the second experiment in the embodiment. More specifically, Figure 8 shows the results of an electromagnetic field simulation for antenna 900a without the phase shifter 1, i.e., antenna 900. Figure 9 shows the results of an electromagnetic field simulation for antenna 900a. The results in Figure 8 are used as a comparison to evaluate the results in Figure 9.

[0085] In this analysis, no tapering was applied to either antenna 900a or antenna 900. That is, the excitation amplitude of the subarrays was the same regardless of the subarray in antenna 900a, and the excitation amplitude of the subarrays was the same regardless of the subarray in antenna 900.

[0086] In the analysis, to reduce computational complexity by considering symmetry, the analysis was performed only on sub-array 0, sub-array 1M, sub-array 2M, and sub-array 3M.

[0087] In Figures 8 and 9, the horizontal axis represents frequency and the vertical axis represents phase. In Figures 8 and 9, the graph of “ang_deg(S(2M,D3_im) / S(1M,D3_in))” shows the phase difference between sub-array 2M and sub-array 1M. The graph of “ang_deg(S(1M,D3_im) / S(1M,D3_in))” shows the phase difference between sub-array 1M and sub-array 1M. The graph of “ang_deg(S(3M,D3_im) / S(1M,D3_in))” shows the phase difference between sub-array 3M and sub-array 1M. The graph of “ang_deg(S(0,D3_im) / S(1M,D3_in))” shows the phase difference between sub-array 0 and sub-array 1M.

[0088] The results in Figures 8 and 9 show that the phase variation for antenna 900 is a maximum of 43 degrees within the 600 MHz band, while for antenna 900a it is a maximum of 4.5 degrees.

[0089] Thus, the results in Figures 8 and 9 demonstrate that phase variation can be reduced by the phase shifter 1 even without tapering.

[0090] It is not prohibited to taper the antenna 900a, and tapering is permitted. In this case, it is possible to reduce phase variation and suppress side lobes.

[0091] <Third Experiment> An example of the effect of phase shifter 1 was verified in the third experiment, and will be explained using Figures 10 to 12. In the third experiment, electromagnetic field simulations were performed on the waveguide shown in Figure 10 and the waveguide shown in Figure 11. The waveguides were rectangular waveguides. In Figures 10 to 12, "width" refers to the length of the major axis of the cross-section of the rectangular waveguide. The length of the minor axis was 10.16 mm. The cross-section of the rectangular waveguide is the cross-section of the rectangular waveguide perpendicular to the propagation direction.

[0092] Figure 10 is the first explanatory diagram illustrating the third experiment in the embodiment. Figure 11 is the second explanatory diagram illustrating the third experiment in the embodiment. Figure 12 is the third explanatory diagram illustrating the third experiment in the embodiment. More specifically, Figures 10 and 11 show the waveguides that are the subject of the electromagnetic field simulation analysis in the third experiment, and Figure 12 is an example of the results of the electromagnetic field simulation for those subjects of analysis.

[0093] Waveguide 2 in Figure 10 is a waveguide with a width of 22.86 mm at one end and a width of 19.5 mm at the other end. In the electromagnetic field simulation that analyzes waveguide 2, electromagnetic waves were incident from outside waveguide 2 to the aforementioned end of waveguide 2 (i.e., the end with a width of 22.86 mm).

[0094] Waveguide 2 has three sections: section 201, section 202, and section 203. Section 202 is located between section 201 and section 203. Section 201 has a width of 22.86 mm and a predetermined length. In the electromagnetic field simulation in the third experiment, its length was 20 mm.

[0095] Section 202 is a section with a predetermined width greater than 19.5 mm and less than 22.86 mm, and a length of 11.72 mm. Section 203 is a section with a predetermined width of 19.5 mm and a length greater than or equal to the wavelength. The length of section 203 was 20 mm in the electromagnetic field simulation in the third experiment.

[0096] Waveguide 3 in Figure 11 is a waveguide with a width of 22.86 mm at one end and a width of 19.5 mm at the other end. In the electromagnetic field simulation that analyzes waveguide 3, electromagnetic waves were incident from outside waveguide 3 to the aforementioned end of waveguide 3 (i.e., the end with a width of 22.86 mm).

[0097] Waveguide 3 has three sections: section 301, section 302, and section 303. Section 302 is located between section 301 and section 303. The structure of section 301 is the same as that of section 201. Specifically, section 301 has a width of 22.86 mm, and in the electromagnetic field simulation in the third experiment, which was a section of a predetermined length, it was 20 mm long.

[0098] Part 302 has a width of 22.86 mm on the side adjacent to part 301, the same as the width of part 301, and a width of 19.5 mm on the side adjacent to part 303, the same as the width of part 303. Part 302 is a part whose width changes continuously over a length L from 22.86 mm to 19.5 mm, from the end adjacent to part 301 (i.e., the boundary with part 301) to the end adjacent to part 303 (i.e., the boundary with part 303). The change from 22.86 mm to 19.5 mm is a change with a constant slope. In other words, the width of part 302 is the width that changes from 22.86 mm towards the end adjacent to part 303, with a slope of (22.86 - 19.5) / L.

[0099] L is a variable, and in the third experiment, electromagnetic field simulations were performed under multiple conditions in which L was varied.

[0100] The structure of part 303 is the same as that of part 203. That is, part 303 is a part with a width of 19.5 mm and a predetermined length. The length of part 303 was 20 mm in the electromagnetic field simulation in the third experiment, for example.

[0101] Thus, section 302 is a tapered waveguide, and waveguide 3 is a waveguide in which section 301 and section 303 are connected by a tapered waveguide.

[0102] Furthermore, both ends of section 202 are examples of two-stage stepped sections. More specifically, the boundary between section 202 and section 203 is an example of a first step, and the boundary between section 202 and section 201 is an example of a second step. Therefore, the third experiment was an experiment to compare the stepped sections of the phase shifter 1 with those of a tapered waveguide.

[0103] Figure 12 shows the simulation results of the reflection coefficient of waveguide 2 and the reflection coefficients of waveguide 3 under the conditions of L = 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, and 60 mm. The lower the reflection coefficient, the less reflection, scattering, or absorption. Therefore, when a waveguide with a high transmittance is preferred, a waveguide with a lower reflection coefficient is a more preferred waveguide. On the other hand, when a waveguide with a low transmittance is preferred, a waveguide with a higher reflection coefficient is a more preferred waveguide.

[0104] The horizontal axis of Figure 12 indicates the frequency of the electromagnetic wave incident on the waveguide. Although it is clear from the explanations up to this point, the vertical axis of Figure 12 indicates the reflection coefficient. In the third experiment, simulations were performed for frequencies from 8.8 GHz to 10.2 GHz.

[0105] The results of Figure 12 show that at the design frequency, a reflection coefficient of -35 dB or less is achieved by waveguide 2, while for waveguide 3, a reflection coefficient comparable to that of waveguide 2 cannot be achieved unless L is about 50 to 60 mm or more. The design frequency is specifically 9.3 to 9.9 GHz.

[0106] Thus, the results of Figure 12 show that a waveguide having a step portion has less reflection loss than a phase shifter having a tapered waveguide. Therefore, phase shifter 1 has less loss than a phase shifter having a tapered waveguide.

[0107] Phase shifter 1 configured as described above has a 0th portion, a 1st portion, a 2nd portion, a 3rd portion, and a 4th portion. Therefore, as described in <Explanation using the mathematical formula of the phase change with N = 4 as an example and the effect of phase shifter 1>, a phase can be imparted to the incident radio wave. Therefore, phase shifter 1 can reduce the group delay error.

[0108] (Modified Example) The phase shifter 1 may be used, for example, in satellite SAR, but it does not necessarily have to be used only in satellite SAR; it may also be used in antennas used for ground-based communications, such as the antennas of smartphones.

[0109] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Explanation of Symbols]

[0110] 1...Phase shifter, 100...0th section, 101...1st section, 102...2nd section, 103...3rd section, 104...4th section, 900, 900a...antenna, 90, 90a...power supply circuit, 3M, 2M, 1M, 0, 1P, 2P, 3P...subarray

Claims

1. A rectangular waveguide having sections 0 to N (N = 2 × n, where n is a predetermined integer of 2 or more) through which radio waves propagate, Equipped with, th (p ｏｄｄ +2) Part (p ｏｄｄ (1 or more and (N-3) or less odd numbers) is the (p ｏｄｄ This is the part with a width of +2), th (p ｏｄｄ The width of +2) is p ｏｄｄ Unlike the width, th (p ｅｖｅｎ +2) Part (p ｅｖｅｎ (The even number is 2 or greater and (N-2 or less)) is the (p ｅｖｅｎ This is the part with a width of +2), The width of the (p ｅｖｅｎ +2) is equal to the width of the (p ｅｖｅｎ +2) that satisfies the relationship of (p ｏｄｄ +2)=(p ｏｄｄ +2)+1, The aforementioned radio waves are of the (q ｏｄｄ -2) Inside the part (q ｏｄｄ After propagating an odd number (3 or greater, up to N), the q ｏｄｄ The propagation within a body part is called q ｏｄｄ = From 1 to q ｏｄｄ = Repeat up to N-1, propagating within the (N-1)th part, then propagating through the 0th part, and then the qth part. ｅｖｅｎ Within the part (q ｅｖｅｎ After propagating (an even number between 1 and N), the (q ｅｖｅｎ -2) Propagation within a body part is called q ｅｖｅｎ = From N to q ｅｖｅｎ Repeat up to 4. The width of part 0 is the width of part 0, the width of part 1 is a first width different from the width of part 0, and the width of part 2 is equal to the width of part 1. Phase shifter.

2. The first width is longer than the zero width. (p ｏｄｄ The width of +2) is the aforementioned p ｏｄｄ Shorter than the width of the aforementioned 0, (p ｅｖｅｎ The width of (+2) is (p ｅｖｅｎ +2) = (p ｏｄｄ The aforementioned (p) satisfying the relationship (+2)+1 ｏｄｄ Equal to the width of +2) The phase shifter according to claim 1.

3. The first width is shorter than the zero width. (p ｏｄｄ The width of +2) is the aforementioned p ｏｄｄ The width is longer than the width of the aforementioned zero, (p ｅｖｅｎ The width of (+2) is (p ｅｖｅｎ +2) = (p ｏｄｄ The aforementioned (p) satisfying the relationship (+2)+1 ｏｄｄ Equal to the width of +2) The phase shifter according to claim 1.

4. N = 4, The length of the third portion in the direction of the propagation axis, which is the axis of the rectangular waveguide, is approximately one-quarter of the wavelength of the radio wave in a vacuum. A phase shifter according to any one of claims 1 to 3.

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