Phase shifter and phased array

Abstract

This phase shifter 10 comprises an input terminal T1, a variable phase shifter 12, a distributor 14, a mixer 15, an LPF 16, and an output terminal T2. The variable phase shifter 12 is configured to change a phase of a first electric signal input to the input terminal T1 by a phase rotation amount corresponding to a phase shift adjustment voltage Vp. The distributor 14 is configured to distribute the first electric signal having the phase changed by the variable phase shifter 12 to the output terminal T2 and the mixer. The mixer 15 is configured to output, as a third electric signal, an electric signal obtained by multiplying the first electric signal distributed by the distributor 14 with a second electric signal which is the same electric signal as the first electric signal supplied from another phase shifter but having the phase rotated by the other phase shifter, to the LPF 16. The LPF 16 is configured to remove an AC component from the third electric signal from the mixer 15 and output a fourth electric signal after the removal.

Description

Phase Shifters and Phased Arrays

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

[0002] Phase shifters that rotate (i.e., shift) the phase of an input electrical signal as it propagates are known. Known phase shifters include fixed phase shifters, which have a fixed amount of phase rotation, and variable phase shifters, which change the amount of phase rotation depending on an external operation amount (Non-Patent Document 1).

[0003] Amit S. Nagra et al., “Monolithic GaAs Phase Shifter Circuit with Low Insertion Loss and Continuous 0-360 Phase Shift at 20 GHz,” IEEE Microwave and Guided Wave Letters, vol. 9, no. 1, pp. 31-33, Jan. 1999.

[0004] A variable phase shifter uses a variable capacitance element such as a transistor and / or a diode. The manipulated variable (phase adjustment voltage Vp, described below) supplied to the variable phase shifter controls the amount of phase rotation by changing the capacitance value of the variable capacitance element. When multiple variable phase shifters with the same physical configuration are provided, ideally, the amount of phase rotation corresponding to the same manipulated variable is the same among the multiple variable phase shifters. However, in reality, variations in the characteristics of the variable capacitance elements due to manufacturing processes or ambient temperature changes can cause variations in the amount of phase rotation even when the same manipulated variable is input to each variable phase shifter.

[0005] An object of the present invention is to compensate for variations in the amount of phase rotation of a variable phase shifter.

[0006] In order to solve the above problem, a phase shifter according to the present invention rotates the phase of a first electrical signal, and includes an input terminal, a variable phase shifter, a divider, a mixer, a low-pass filter, and an output terminal, wherein the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by an amount of phase rotation corresponding to an operation amount, the divider is configured to distribute the first electrical signal, the phase of which has been changed by the variable phase shifter, to the output terminal and the mixer, the mixer is configured to multiply the first electrical signal distributed by the divider by a second electrical signal, which is supplied from a phase shifter different from the variable phase shifter and is the same as the first electrical signal but has had its phase rotated by the other phase shifter, and to output the obtained electrical signal to the low-pass filter as a third electrical signal, and the low-pass filter is configured to remove AC components from the third electrical signal from the mixer, and to output a fourth electrical signal after the AC component removal.

[0007] A phased array according to the present invention is a phased array comprising a plurality of phase shifters that rotate the phase of a first electrical signal supplied to an antenna, and a control circuit that controls the plurality of phase shifters, wherein each of the plurality of phase shifters comprises an input terminal, a variable phase shifter, a divider, a mixer, a low-pass filter, and an output terminal, wherein the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by a phase rotation amount corresponding to an operation amount, and the divider is configured to distribute the first electrical signal whose phase has been changed by the variable phase shifter to the output terminal and the mixer, and the mixer mixes the first electrical signal distributed by the divider with the first electrical signal supplied from another phase shifter different from the variable phase shifter. The control circuit is configured to multiply the first electrical signal by a second electrical signal which is the same electrical signal but has had its phase rotated by the other phase shifter, and output the obtained electrical signal to the low-pass filter as a third electrical signal, and the low-pass filter is configured to remove AC components from the third electrical signal from the mixer and output a fourth electrical signal after the removal, and the control circuit changes the manipulated variable for each of the plurality of phase shifters to obtain the manipulated variable when the value of the fourth electrical signal becomes a value indicating that the phase difference between the first electrical signal and the second electrical signal is 0, obtains the difference between the manipulated variable and a reference manipulated variable as a correction value, and supplies the manipulated variable corrected based on the correction value to the variable phase shifter when controlling the phase of the first electrical signal to be output from the output terminal.

[0008] According to the present invention, variations in the amount of phase rotation of a variable phase shifter can be compensated for.

[0009] FIG. 1 is a schematic configuration diagram of a variable phase shifter according to a first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a variable phase shifter according to the first embodiment of the present invention. FIG. 3 is a graph showing characteristics of the variable phase shifter according to the first embodiment of the present invention. FIG. 4 is a schematic configuration diagram of a phased array according to the first embodiment of the present invention. FIG. 5 is a graph for explaining characteristic variations of the variable phase shifter according to the first embodiment of the present invention. FIG. 6 is a schematic configuration diagram of a phase shifter according to the first embodiment of the present invention. FIG. 7 is a schematic configuration diagram of a phased array according to the first embodiment of the present invention. FIG. 8 is a graph showing the relationship between the output of an LPF and Δθ. FIG. 9 is a flowchart of setting processing. FIG. 10 is a diagram showing an example of the configuration of a correction voltage table. FIG. 11 is a flowchart of correction processing. FIG. 12 is a diagram showing an example of the configuration of a phase shifter according to the first embodiment of the present invention. FIG. 13 is a diagram showing an example of the configuration of a phase shifter according to the first embodiment of the present invention. FIG. 14 is a diagram showing an example of the configuration of a phase shifter according to the first embodiment of the present invention. FIG. 15 is a diagram showing an example of the configuration of a phase shifter according to the first embodiment of the present invention. Fig. 16 is a configuration diagram of an example of a phase shifter according to a first embodiment of the present invention. Fig. 17 is a configuration diagram of an example of a phase shifter according to the first embodiment of the present invention. Fig. 18 is a configuration diagram of an example of a phase shifter according to the first embodiment of the present invention. Fig. 19 is a schematic configuration diagram of a phased array according to a second embodiment of the present invention.

[0010] Hereinafter, an embodiment of the present invention and its modifications will be described with reference to the drawings.

[0011] First Embodiment First, the structure of a variable phase shifter used in a phase shifter according to this embodiment will be described. FIG. 1 shows an example of the configuration of a variable phase shifter 12 configured as a delay line phase shifter. As shown in FIG. 1, the variable phase shifter 12 includes an input terminal Tin, an output terminal Tout, a plurality of unit transmission lines L connected in series between them, and a transistor Tr connected to a node N connecting adjacent unit transmission lines L. The gate G of each transistor Tr is connected to the corresponding node N. The source S and drain D of the transistor Tr are grounded. The variable phase shifter 12 further includes a control terminal Tc to which a phase adjustment voltage Vp is input as a manipulation variable for controlling the amount of phase rotation by the variable phase shifter 12, and a plurality of resistors R connected to the control terminal Tc and each node N. With this configuration, by changing the phase adjustment voltage Vp applied to the variable phase shifter 12, the capacitance value of the transistor Tr forming a variable capacitance can be changed, thereby controlling the amount of phase rotation θ of an electrical signal propagating between the input terminal Tin and the output terminal Tout.

[0012] The variable phase shifter 12 may be configured as a reflective phase shifter as shown in Fig. 2. A reflective phase shifter has a configuration in which an input terminal Tin and an output terminal Tout are provided at the coupled port of a coupler, and two transistors Tr are connected to two isolation terminals Ti of the coupler, respectively. In a reflective phase shifter, the capacitance value of each transistor Tr changes depending on voltages Vp1 and Vp2, which are phase adjustment voltages Vp input to control terminals Tc1 and Tc2, respectively, and this change changes the amount of phase rotation θ between the input and output.

[0013] The variable phase shifter 12 may have other configurations. A diode may be used instead of the transistor Tr. The variable phase shifter 12 may be configured to change the phase rotation amount θ in accordance with an operation amount (here, a phase adjustment voltage Vp) from a control circuit, for example.

[0014] The phase rotation θ of the variable phase shifter 12 varies with respect to the phase adjustment voltage Vp according to the characteristics shown by the solid line in the graph of FIG. 3. That is, when Vp is small, the phase rotation θ of the electrical signal passing through the variable phase shifter hardly changes, but when Vp exceeds the voltage threshold Vth, the phase rotation θ begins to vary monotonically (e.g., almost linearly) with respect to Vp. When Vp exceeds a certain value, the phase rotation θ no longer changes. In the variable phase shifter, the desired phase rotation θ can be obtained by setting Vp to an appropriate value within the range in which the phase rotation varies.

[0015] The variable phase shifters 12 use variable capacitance elements such as transistors or diodes. However, variations in the characteristics of the variable capacitance elements due to the manufacturing process or changes in ambient temperature, particularly variations in the voltage threshold Vth, result in variations in the amount of phase rotation θ even if the same phase adjustment voltage Vp is applied to each of the variable phase shifters 12 (see, for example, the dashed and solid line graphs in FIG. 3).

[0016] The above-described variations become a problem, for example, when multiple variable phase shifters 12 having the same structure are used. An example of an apparatus having multiple variable phase shifters 12 is a phased array 900 as shown in FIG. 4 . The phased array 900 includes multiple antenna units U, each of which includes a wireless communication front end FE including a variable phase shifter 12. The phased array 900 controls the phase of each electromagnetic wave radiated from each of the multiple antennas AN by controlling the phase rotation amount θ of each variable phase shifter 12, thereby controlling the beam shape of the electromagnetic waves (particularly, the emission direction of the electromagnetic waves). However, due to the variations among the variable phase shifters 12, even if an appropriate phase adjustment voltage Vp is input to each variable phase shifter 12, variations in the phase rotation amount θ relative to Vp can cause a problem of a deviation in beam direction from the desired beam shape and / or the generation of side lobes (see beam B indicated by the dashed line in FIG. 4 ).

[0017] In this embodiment, the variation in the phase rotation amount θ caused by the variation in the characteristics of the variable capacitance element is compensated for. The principle of this compensation will be explained below.

[0018] The most direct method for the above correction is to measure the phase shift characteristics of all variable phase shifters 12 in advance, thereby enabling the voltage Vp to be applied to each variable phase shifter 12 to be determined individually. However, this method is not practical. This method is particularly unrealistic when dealing with electrical signals in high frequency bands, such as millimeter waves or higher, where the phase cannot be directly measured (especially the broadband THz wave (electromagnetic waves from 300 GHz to 30 THz) band, which is expected to be applied to ultra-high-speed wireless communications such as next-generation wireless communications (beyond 5G)). Furthermore, even if direct measurement were possible, it is not easy to measure the phase rotation θ that occurs in the variable phase shifter 12 that is integrated with other circuits, as in a real phased array. Therefore, a new method to resolve the above-mentioned inconvenience is needed.

[0019] The principle of this embodiment will be explained below. First, let us consider an ideal variable phase shifter 12, for example, a phase shifter 12 whose relationship between the phase adjustment voltage Vp and the phase rotation amount θ is known theoretically or experimentally as the reference phase shifter 12ref. The characteristic variation ΔVp of the variable phase shifter 12X to be corrected is expressed by the following equation (1) which gives the phase rotation amount φ to the variable phase shifter 12X and the reference phase shifter 12ref (see also FIG. 5 ). Here, Vpx is the value of the phase adjustment voltage Vp at which the phase rotation amount θ=φ in the variable phase shifter 12X. Vpref is the value of the phase adjustment voltage Vp at which the phase rotation amount θ=φ in the reference phase shifter 12ref. ΔVp=Vpx-Vpref (1)

[0020] From equation (1), the voltage value Vpx for obtaining the phase rotation amount φ in the variable phase shifter 12X equal to that of the reference phase shifter 12ref can be obtained from the following equation (2): Vpx=Vpref+ΔVp (2)

[0021] From the above, first, some method is used to find the phase adjustment voltage Vpx that provides the phase rotation amount φ for each of all the variable phase shifters 12. Then, the phase adjustment voltage Vpref required to obtain the phase rotation amount φ of the reference phase shifter 12ref is obtained, and the correction voltage ΔVp for each of the variable phase shifters 12X can be obtained using the above equation (1).

[0022] Here, because variations in the characteristics of the individual variable phase shifters 12 are due to differences in the voltage threshold Vth, the correction voltage ΔVp calculated by equation (1) can be used within a range in which the phase rotation θ changes monotonically. Therefore, for example, if the correction voltage ΔVp is calculated for each variable phase shifter 12X, the phase adjustment voltage Vp to be input to that variable phase shifter 12X can be calculated by adding ΔVp to Vp corresponding to the desired phase rotation θ of the reference phase shifter 12ref.

[0023] Next, a specific method for obtaining the phase adjustment voltage Vpx when the plurality of variable phase shifters 12 have the phase rotation amount φ will be described through an explanation of the variable phase shifters 12 shown in FIG. 6 and the phased array 100 shown in FIG. 7.

[0024] 7 , the phased array 100 includes a plurality of antenna units 110 and a control circuit 120. Each of the plurality of antenna units 110 includes an antenna 111 and a wireless communication front end 112 including a phase shifter 10. The control circuit 120 controls each of the wireless communication front ends 112. In particular, the control circuit 120 controls each of the phase shifters 10 to control the phase of each electromagnetic wave radiated from each of the plurality of antennas 111, thereby controlling the beam shape of the electromagnetic waves (in particular, the emission direction of the electromagnetic waves).

[0025] Each phase shifter 10 of the phased array 100 is configured with the same elements and has the same structure. In particular, the fixed phase shifters and variable phase shifters have the same structure among the phase shifters 10. As shown in FIG. 6 , each phase shifter 10 includes an input terminal T1, an output terminal T2, a divider 11, a variable phase shifter 12, a fixed phase shifter 13, a divider 14, a mixer 15, and an LPF (low-pass filter) 16.

[0026] A modulated electrical signal representing data to be transmitted and received via wireless communication is input to input terminal T1. Input terminal T1 is connected to the input terminal of distributor 11, and two output terminals of distributor 11 are connected to the input terminals of variable phase shifter 12 and fixed phase shifter 13, respectively. With this connection, the electrical signal input to input terminal T1 is input to distributor 11. Distributor 11 distributes the input electrical signal to variable phase shifter 12 and fixed phase shifter 13.

[0027] The variable phase shifter 12 connected to the divider 11 rotates (changes) the phase of the electrical signal from the divider 11 in accordance with a phase adjustment voltage Vp (operation amount) from the control circuit 120. The output terminal of the variable phase shifter 12 is connected to the input terminal of the divider 14, and the electrical signal whose phase has been rotated by the variable phase shifter 12 is input to the divider 14.

[0028] The fixed phase shifter 13 connected to the distributor 11 is configured to rotate the phase of the electrical signal from the distributor 11 by a constant amount of rotation. The fixed phase shifter 13 is formed, for example, by a delay line such as a coaxial cable. Since the fixed phase shifter 13 does not use a variable capacitance element such as a transistor or a diode, the amount of phase rotation of the electrical signal is constant, i.e., fixed. The output terminal of the fixed phase shifter 13 is connected to one of the two input terminals of the mixer 15. Therefore, the electrical signal whose phase has been rotated by the fixed phase shifter 13 is input to the mixer 15.

[0029] The two output terminals of the distributor 14 are connected to the other of the two input terminals of the mixer 15 and to the output terminal T2. With this connection, the distributor 14 distributes the electrical signal whose phase has been rotated by the variable phase shifter 12 to the mixer 15 and the output terminal T2.

[0030] The electrical signal output to the output terminal T2 is an electrical signal whose phase has been rotated by the variable phase shifter 12, and is output from the output terminal T2 to the outside of the phase shifter 10. In other words, the phase shifter 10 rotates the phase of the electrical signal input to the input terminal T1 by the variable phase shifter 12, and outputs the phase-rotated electrical signal from the output terminal T2.

[0031] The mixer 15 multiplies the electrical signal from the variable phase shifter 12 and the electrical signal from the fixed phase shifter 13, which are input to its two input terminals. The output terminal of the mixer 15 is connected to the input terminal of the LPF 16, and the electrical signal multiplied by the mixer 15 is output to the LPF 16.

[0032] The LPF 16 is configured to remove AC components from the electrical signal output from the mixer 15. The output terminal of the LPF 16 is connected to the input terminal of the control circuit 120, and the electrical signal from which the AC components have been removed by the LPF 16, i.e., the electrical signal with a DC component, is input to the control circuit 120.

[0033] In the phase shifter 10 described above, an input electrical signal is distributed by the distributor 11 to the variable phase shifter 12 and the fixed phase shifter 13. Here, the fixed phase shifter 13 can be realized using passive elements such as transmission lines, and does not have variable capacitance elements that cause characteristic variations in transistors or diodes, etc. Therefore, when multiple fixed phase shifters 13 are manufactured with the same configuration, characteristic variations do not occur, unlike the variable phase shifter 12 (even if there is characteristic variation, it is so small that it can be ignored). The phase rotation amount of the fixed phase shifter 13 is known at the time of manufacture, so the phase rotation amount = θknown.

[0034] Of the signals input to mixer 15, the signal that has passed through variable phase shifter 12 is expressed as cos(ωt+θ(Vp)), and the signal that has passed through fixed phase shifter 13 is expressed as cos(ωt+θknown). Here, θ(Vp) is the amount of phase rotation according to the input phase adjustment voltage Vp. Therefore, the magnitude (voltage) of the output signal of mixer 15 is the value obtained by multiplying the value of the following equation (3) by a predetermined coefficient. cos(ωt+θ(Vp))·cos(ωt+θknown)=[cos(2ωt+θ(Vp)+θknown)−cos(θ(Vp)−θknown)] / 2 ... (3)

[0035] The right-hand side of equation (3) consists of cos(2ωt+θ(Vp)+θknown), that is, an AC component of frequency 2ωt, and a DC component of cos(θ(Vp)-θknown). The output signal of mixer 15 is input to LPF 16, which is located downstream of mixer 15, where the AC component is removed and only the DC component is output to control circuit 120. For this reason, the magnitude of the electrical signal output by LPF 16 is proportional to the value of equation (4) below. cos(θ(Vp)-θknown) / 2 ... (4)

[0036] By using the above (4), it is possible to find the phase adjustment voltage Vpx when the amount of phase rotation of the variable phase shifter 12 becomes φ. This point will be described in detail below.

[0037] First, θknown is the amount of phase rotation of the fixed phase shifter 13, and as described above, this amount of phase rotation can be treated as having no variation among multiple fixed phase shifters 13 of the same structure. Therefore, θknown is common among multiple phase shifters 10. Therefore, if θ(Vp) = θknown, the amount of phase rotation of the variable phase shifters 12 of each of the multiple phase shifters 10 can be made common, and θknown can be set to the above-mentioned φ.

[0038] Furthermore, since the amount of phase rotation of the variable phase shifter 12 is at most 2π, 0≦θ(Vp)≦2π. In this case, the range within which the phase part Δθ=θ(Vp)−θknown moves is the range of the following equation (5): −θknown≦Δθ≦2π−θknown (5)

[0039] 8 shows the relationship between equation (4) and the range of Δθ, which indicates that Δθ moves only one cycle of the cosine curve. Therefore, equation (4) here takes a maximum value only when θ(Vp)=θknown, that is, at the single point where Δθ=0. Note that Δθ=0 also indicates that the phase difference between the electrical signal output by variable phase shifter 12 and the electrical signal output by fixed phase shifter 13 is 0.

[0040] Based on the above, the phase adjustment voltage Vp is varied to change the value of equation (4), and the output signal of LPF 16, which is proportional to equation (4), is monitored to determine the phase adjustment voltage Vp at which the output signal is maximized, i.e., θ(Vp) = θknown. This phase adjustment voltage Vp at which θ(Vp) = θknown (=φ) becomes the phase adjustment voltage Vpx. Once the phase adjustment voltage Vpx is determined, ΔVp for each phase shifter 10 based on the reference phase adjustment voltage Vpref can also be determined, as described above.

[0041] The above operation uses a mixer, a circuit consisting of transistors or diodes (described in detail below). At first glance, this appears to be contrary to the spirit of this embodiment. In other words, this embodiment aims to compensate for the phase shifter 10, whose characteristics vary due to variations in transistors or diodes. However, the use of the mixer 15, which also has characteristic variations, as a means of compensation must be verified for its legitimacy. While the mixer 15 varies, the resulting variation is in the output value of the LPF 16 (more precisely, the amount of mixer conversion gain multiplied as a coefficient by the value of Equation (4)), not in the mixer's inherent "multiplication" function itself. In other words, there is no variation in the tendency for Equation (4) to reach its maximum value when Δθ = 0. Therefore, the above technique is effective as a means of correcting the variation in the variable phase shifter 12.

[0042] The phase adjustment voltage Vpx of the variable phase shifter 12 of each phase shifter 10 is derived by the control circuit 120 shown in Fig. 7. The control circuit 120 includes various computers such as a microcomputer, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and the like.

[0043] When performing various settings such as initial settings, the control circuit 120 performs the setting process shown in Fig. 9. In this process, the control circuit 120 controls each of the multiple phase shifters 10 individually to derive the phase adjustment voltage Vpx for each phase shifter 10.

[0044] Specifically, the control circuit 120 first varies the phase adjustment voltage Vp for each of the phase shifters 10 (variable phase shifters 12) to derive, for each phase shifter 10, the phase adjustment voltage Vp at which the output signal of the LPF 16 reaches a maximum value (step S11). This phase adjustment voltage Vp is the phase adjustment voltage Vpx.

[0045] After deriving the phase adjustment voltage Vpx for each phase shifter 10, the control circuit 120 subtracts Vpx from the phase adjustment voltage Vpref (the phase adjustment voltage Vp applied to the reference phase shifter 12ref, with the amount of phase rotation θknown=φ), which is set as a known value in advance, for each phase shifter 10 (step S12). In this way, the control circuit 120 derives the correction voltage ΔVp for each phase shifter 10.

[0046] The control circuit 120 generates and stores a correction voltage table indicating the correspondence between the phase shifter ID for identifying the phase shifter 10 and the correction voltage ΔVp of that phase shifter 10, based on the correction voltage ΔVp derived for each phase shifter 10 (step S13). An example of the configuration of such a correction voltage table is shown in Fig. 10. In the correction voltage table shown in Fig. 10, the correction voltage ΔVp is associated with each phase shifter ID.

[0047] The control circuit 120 is assumed to hold reference phase shifter data (e.g., a function or a table) indicating the relationship between the phase adjustment voltage Vp and the phase rotation amount θ at the reference phase shifter 12ref. This reference phase shifter data may be supplied to the control circuit 120 from an external source. The reference phase shifter 12ref may be an ideal variable phase shifter 12 that does not suffer from the above-mentioned variations, and the reference phase shifter data is derived by calculation, experiment, or the like. The reference phase shifter 12ref may be any phase shifter 12. In this case, the reference phase shifter data is derived by experiment, or the like.

[0048] When the phased array 100 forms a beam shape of emitted (incident) electromagnetic waves (that is, when the phased array 100 is in operation after various settings have been made), the phase rotation amount θ for each phase shifter 10, i.e., for each variable phase shifter 12, is input to the control circuit 120 from a device external to the phased array 100. For example, multiple sets of information, each including a phase shifter ID and the phase rotation amount θ associated with the phase shifter ID, are supplied to the control circuit 120.

[0049] When the control circuit 120 receives the information, it performs the correction process shown in FIG. 11 for each phase shifter ID. In this process, the control circuit 120 first obtains a phase adjustment voltage Vp corresponding to the phase rotation amount θ input from an external device or the like using the reference phase shifter data (step S21). The control circuit 120 then references a correction voltage table to obtain a correction voltage ΔVp corresponding to the phase shifter ID being processed (step S22). The control circuit 120 adds the correction voltage ΔVp to the obtained phase adjustment voltage Vp to derive the corrected phase adjustment voltage Vp to be actually input to the variable phase shifter 12 of the phase shifter 10 identified by the phase shifter ID being processed (step S23). The control circuit 120 then inputs the corrected phase adjustment voltage Vp to the variable phase shifter 12 at a desired timing (step S24).

[0050] By the above-described processing, variations in the amount of phase rotation θ of the variable phase shifter 12 are compensated for, and a highly accurate beamform is achieved by the phased array 100. Note that multiple sets of information, each including a phase shifter ID and a phase adjustment voltage Vp associated with the phase shifter ID, may be supplied to the control circuit 120. In such a case, reference phase shifter data is not necessary, and the control circuit 120 may correct the supplied phase adjustment voltage Vp with a correction voltage ΔVp.

[0051] Next, a specific example of the configuration of the phase shifter 10 will be described.

[0052] 12 and 13, the dividers 11 and 14 of the phase shifter 10 may be directional couplers. A directional coupler can be used for the dividers 11 and 14 because it has the property of being able to divide an input electrical signal into a through port and a coupled port.

[0053] In the example of FIG. 12 , the divider 11 includes transmission lines 11A, 11B, and a resistor 11C. The input port of the transmission line 11A is connected to the input terminal T1, and the output port of the transmission line 11A is connected to the input terminal of the variable phase shifter 12. The coupled port of the transmission line 11B is connected to the input terminal of the fixed phase shifter 13. The isolated port of the transmission line 11B is grounded via a resistor 11C. The divider 14 includes transmission lines 14A, 14B, and a resistor 14C. The input port of the transmission line 14A is connected to the output terminal of the variable phase shifter 12, and the output port of the transmission line 14A is connected to the output terminal T2. The coupled port of the transmission line 14B is connected to the input terminal of the mixer 15. The isolated port of the transmission line 14B is grounded via a resistor 14C.

[0054] The example in Fig. 13 differs from the example in Fig. 12 in the destination of connection of the distributor 11. The input port of the transmission line 11A is connected to the input terminal T1, while the output port of the transmission line 11A is connected to the input terminal of the fixed phase shifter 13. The coupled port of the transmission line 11B is connected to the input terminal of the variable phase shifter 12. The isolated port of the transmission line 11B is grounded via a resistor 11C.

[0055] In the example of FIG. 12 , the path of the electrical signal passing through the variable phase shifter 12 and input to the mixer 15 and the path of the electrical signal passing through the fixed phase shifter 13 and input to the mixer 15 pass through the coupled port of the directional coupler the same number of times. On the other hand, in the example of FIG. 13 , the number of times is different. The electrical signal input to the directional coupler experiences different phase rotations when output to the output port and when output to the coupled port (typically, the coupled port side is delayed by 90 degrees relative to the output port side). For this reason, the configuration of FIG. 12 is the one to which the discussion of the above equations (3) to (5) can be applied as is. However, even in the configuration of FIG. 13 , if the phase difference between the coupled port and the output port of the directional coupler is known in advance, the discussion of the above equations (3) to (5) can be applied by correcting for this phase difference. The coupling coefficient of the directional coupler and its physical configuration (e.g., the length, width, and gap of the transmission line) are optional design factors.

[0056] Wilkinson couplers may be used as the dividers 11 and 14, as shown in Figure 14. A Wilkinson coupler is a coupler that can output an input electrical signal with the same phase difference and a certain division ratio. The division ratio (coupling coefficient) of the Wilkinson coupler and its physical configuration are design considerations.

[0057] The configuration of the divider is arbitrary, and the divider may be configured with a simpler branch circuit, a resistive division circuit, or the like.

[0058] As shown in FIG. 15 , a diode may be used as the mixer 15. Alternatively, as shown in FIG. 16 , a gate injection mixer using a field-effect transistor (or a base injection mixer using a bipolar transistor) may be employed as the mixer 15. In the example of FIG. 16 , a transistor, which is a three-terminal device, is used as a two-terminal device similar to a diode, so the configurations of FIGS. 15 and 16 are essentially the same circuit. While this configuration is very simple, it does not provide isolation of signals input to the diode or transistor (due to being input to the same terminal). This can lead to problems, such as a signal passing through the upstream divider 11 sneaking into the downstream divider 14, being reflected again by the downstream divider 14, and being re-input to the mixer 15. Typically, the reflections at the dividers 11 and 14 are not significant, so this re-input signal to the mixer 15 rarely causes problems. However, if the reflection is significant and the level of the re-input signal is high, the re-input signal will be superimposed on the two original input signals, causing the phase difference Δθ to deviate from the desired value, resulting in an inaccurate calculation of the correction voltage ΔVp. To resolve this issue, a mixer (such as a source-injected mixer, drain-injected mixer, or the resistive mixer described in Japanese Patent No. 6835761) can be used, as shown in Figure 17, in which the signals from the variable phase shifter 12 and the fixed phase shifter 13 are input to different ports of the transistor. Since such a transistor has sufficient isolation (approximately 20-30 dB) between its terminals, the signal passing through the upstream divider 11 will not be transmitted to the downstream divider 14, thereby eliminating the aforementioned re-input signal problem. While Figures 15-17 illustrate the use of directional couplers in the dividers 11 and 14, the same discussion applies regardless of the type of branching circuit used.

[0059] When the phased array 100 is configured as a transmitter, the wireless communication front end 112 includes a power amplifier after the phase shifter 10. When the phased array 100 is configured as a receiver, the wireless communication front end 112 includes a low-noise amplifier before the phase shifter 10. These amplifiers may also have characteristic variations similar to those of the variable capacitance element of the variable phase shifter 12. Therefore, as shown in FIG. 18 , an amplifier 19 such as a power amplifier or a low-noise amplifier may be included in the phase shifter 10 and placed between the divider 11 and the divider 14, particularly between the variable phase shifter 12 and the divider 14. This allows the phase variations of the circuit in which the variable phase shifter 12 and the amplifier 19 are connected in series to be corrected using the same process as described above. The amplifier 19 amplifies the signal from the preceding divider 11, variable phase shifter 12, or divider 14, depending on its placement. The amplifier 19 may be controlled by a control circuit 120.

[0060] 19 differs in that the electrical signal input to the mixer 15 is not a signal from a fixed phase shifter, but is a variable phase shifter 12 of another phase shifter 210. Hereinafter, the second embodiment will be described, but elements similar to those in the first embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0061] The phased array 200 includes a plurality of antenna units U. Each antenna unit U has the same structure and includes a phase shifter 210 and an antenna 111. The phase shifter 210 includes an input terminal T1, a variable phase shifter 12, an amplifier 19, distributors 214A and 214B, a mixer 15, an LPF 16, and an output terminal T2.

[0062] The input terminal T1 is connected to the input terminal of the variable phase shifter 12. The output terminal of the variable phase shifter 12 is connected to the input terminal of an amplifier 19 such as a power amplifier or a low-noise amplifier. The output terminal of the amplifier 19 is connected to the input terminal of the divider 214A. One of the two output terminals of the divider 214A is connected to the input terminal of the divider 214B. The other of the two output terminals of the divider 214A is connected to the mixer 15 of another phase shifter 210.

[0063] One of the two output terminals of the distributor 214B is connected to one of the two input terminals of the mixer 15, and the other is connected to the output terminal T2, which is connected to the antenna 111. The other of the two input terminals of the mixer 15 is connected to the output terminal of the distributor 214A of the other phase shifter 210.

[0064] The control circuit 120 varies the phase adjustment voltage Vp input to the variable phase shifter 12 of the second phase shifter 210 while inputting a fixed phase adjustment voltage Vp to the variable phase shifter 12 of the first phase shifter 210. As in the above embodiment, the control circuit 120 derives the latter phase adjustment voltage Vp when the output of the LPF 16 reaches its maximum (Δθ = 0). At this time, the same electrical signal is input to the first and second phase shifters 210. The correction voltage ΔVp is derived from the difference between the phase adjustment voltage Vp (Vpref) of the first variable phase shifter 12 and the phase adjustment voltage Vp (Vpx) of the second variable phase shifter 12. This derivation of the correction voltage ΔVp is performed sequentially, for example, for the second and third phase shifters 210, the third and fourth phase shifters 210, and so on. This derives the correction voltage ΔVp for the adjacent phase shifter 210. The control circuit 120 uses one predetermined variable phase shifter 12 (e.g., the variable phase shifter 12 of the first phase shifter 210) of all the variable phase shifters 12 as the reference phase shifter 12ref, and performs correction on the other variable phase shifters 12 with the correction voltage ΔVp calculated above. The relationship between the phase adjustment voltage Vp of the variable phase shifter 12ref and the amount of phase rotation θ may be identified and set by any method, such as experimentation. Furthermore, if control of the amount of phase rotation is achieved by controlling the relative amount of phase rotation between multiple variable phase shifters 12, the reference phase shifter 12ref may be unnecessary.

[0065] According to this configuration, there is no need to provide a fixed phase shifter for each phase shifter 210, and therefore the problem of tight circuit area caused by fixed phase shifters can be more effectively alleviated as the array scale of the phased array 200 increases. Also, in this embodiment, the amplifier 19, such as a power amplifier or a low-noise amplifier, is included in the phase shifter 210 and is disposed between the variable phase shifter 12 and the distributor 14, so that phase variations in the circuit in which the variable phase shifter 12 and the amplifier 19 are connected in series can be corrected.

[0066] Although not shown, the amplifier 19 may be arranged before or after the phase shifter 210. The dividers 214A and 214B may be replaced with a single divider that divides an electrical signal in three directions. Furthermore, the phase shifter 10 of the first embodiment may be used in place of any one or more phase shifters 210, and the correction voltage ΔVp of the variable phase shifter 12 of this phase shifter 10 may be used as a correction voltage for the reference phase shifter 12ref.

[0067] (Effects of the Embodiment) As described above, the phase shifter 10 (or 210) is configured as a phase shifter that rotates the phase of an input first electrical signal (such as a modulated electrical signal), and includes an input terminal T1, a variable phase shifter 12, a distributor 14 (or 214A and 214B), a mixer 15, an LPF 16, and an output terminal T2. The variable phase shifter 12 is configured to change the phase of the first electrical signal input to the input terminal T1 by an amount of phase rotation corresponding to an operation amount (phase shift adjustment voltage Vp). The distributor 14 (or 214A and 214B) is configured to distribute the first electrical signal, the phase of which has been changed by the variable phase shifter 12, to the output terminal T2 and the mixer. The mixer 15 is configured to multiply the first electrical signal distributed by the distributor 14 by a second electrical signal, which is the same as the first electrical signal supplied from another phase shifter (a phase shifter other than the variable phase shifter 12) but whose phase has been rotated by the other phase shifter, and output the resulting electrical signal as a third electrical signal to the LPF 16. The LPF 16 is configured to remove AC components from the third electrical signal from the mixer 15 and output a fourth electrical signal after the AC components have been removed. With this configuration, the control circuit 120 can change the manipulated variable (Vp) to obtain the manipulated variable (Vpx) when the value of the fourth electrical signal indicates that the phase difference between the first electrical signal and the second electrical signal is zero. The control circuit 120 can also obtain the difference between this manipulated variable (Vpx) and a reference manipulated variable (Vpref) as a correction value (ΔVp). Then, when controlling the phase of the first electrical signal output from the output terminal T2, the control circuit 120 can supply a manipulated variable corrected based on the correction value (ΔVp) to the variable phase shifter 12. In this way, in this embodiment, variations in the amount of phase rotation of the variable phase shifter 12 can be compensated for.

[0068] In particular, the phase shifter 10 of the first embodiment further includes a fixed phase shifter 13 as the other phase shifter, and a preceding stage divider 11 provided preceding the variable phase shifter 12 and the fixed phase shifter 13, and this divider 11 is configured to distribute the first electrical signal input to the input terminal T1 to the variable phase shifter 12 and the fixed phase shifter 13. With this configuration, it is possible to effectively compensate for variations in the amount of phase rotation of the variable phase shifter 12 based on the characteristics of the fixed phase shifter 13.

[0069] The other phase shifter is the variable phase shifter 12 used together with the phase shifter 10 or 210. This eliminates the need for the fixed phase shifter 13 and the like, thereby reducing the circuit area of ​​the phase shifter.

[0070] Furthermore, in the phased array 100 or 200 having a plurality of phase shifters 10 or 210, the control circuit 120 changes the manipulated variable (Vp) to obtain the manipulated variable (Vpx) when the value of the fourth electrical signal becomes a value indicating that the phase difference between the first electrical signal and the second electrical signal is zero, and obtains the difference between the obtained manipulated variable (Vpx) and a reference manipulated variable (Vpref) as a correction value (ΔVp). Furthermore, when controlling the phase of the first electrical signal output from the output terminal T2, the control circuit 120 supplies the manipulated variable corrected based on the correction value (ΔVp) to the variable phase shifter 12. In this way, in this embodiment, it is possible to operate the variable phase shifter 12 while compensating for variations in the amount of phase rotation of the variable phase shifter 12.

[0071] The present invention is not limited to the above-described embodiments and modifications. For example, the present invention includes various modifications to the above-described embodiments and modifications that can be understood by a person skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the above-described embodiments and modifications can be combined as appropriate within a range that does not cause contradictions. In addition, any of the above-described configurations can be deleted.

[0072] (Additional Note) The following describes exemplary configurations of the above-described embodiments and modifications disclosed in this specification. (Supplementary Note 1) A phase shifter that rotates the phase of a first electrical signal, comprising: an input terminal, a variable phase shifter, a divider, a mixer, a low-pass filter, and an output terminal; the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by a phase rotation amount corresponding to an operation amount; the divider is configured to distribute the first electrical signal, the phase of which has been changed by the variable phase shifter, to the output terminal and the mixer; the mixer is configured to multiply the first electrical signal distributed by the divider by a second electrical signal, which is the same as the first electrical signal but is supplied from a phase shifter different from the variable phase shifter and has its phase rotated by the other phase shifter, and to output the obtained electrical signal to the low-pass filter as a third electrical signal; and the low-pass filter is configured to remove AC components from the third electrical signal from the mixer, and to output a fourth electrical signal after the AC component removal. (Supplementary Note 2) The phase shifter according to Supplementary Note 1, further comprising: a fixed phase shifter which is the other phase shifter; and a pre-stage divider provided in a stage preceding the variable phase shifter and the fixed phase shifter, wherein the pre-stage divider is configured to divide the first electrical signal input to the input terminal to the variable phase shifter and the fixed phase shifter. (Supplementary Note 3) The phase shifter according to Supplementary Note 1, wherein the other phase shifter is another variable phase shifter used together with the phase shifter according to claim 1. (Supplementary Note 4) The phase shifter according to any of Supplements 1 to 3, further comprising an amplifier arranged between the variable phase shifter and the divider.(Supplementary Note 5) A phased array comprising: a plurality of phase shifters that rotate the phase of a first electrical signal supplied to an antenna; and a control circuit that controls the plurality of phase shifters, wherein each of the plurality of phase shifters comprises an input terminal, a variable phase shifter, a distributor, a mixer, a low-pass filter, and an output terminal, wherein the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by a phase rotation amount corresponding to an operation amount, the distributor is configured to distribute the first electrical signal whose phase has been changed by the variable phase shifter to the output terminal and the mixer, and the mixer is configured to multiply the first electrical signal distributed by the distributor by a second electrical signal that is the same as the first electrical signal but whose phase has been rotated by the other phase shifter, and to output the obtained electrical signal to the low-pass filter as a third electrical signal, the low-pass filter is configured to remove AC components from the third electrical signal from the mixer and output a fourth electrical signal after the AC component removal; and the control circuit, for each of the plurality of phase shifters, changes the manipulated variable to obtain the manipulated variable when the value of the fourth electrical signal becomes a value indicating that the phase difference between the first electrical signal and the second electrical signal is 0, obtains a difference between the manipulated variable and a reference manipulated variable as a correction value, and supplies the manipulated variable corrected based on the correction value to the variable phase shifter when controlling the phase of the first electrical signal output from the output terminal. (Supplementary Note 6) The phase shifter according to Supplementary Note 5, wherein at least one of the plurality of phase shifters further comprises: a fixed phase shifter which is the other phase shifter; and a pre-stage distributor provided in a stage preceding the variable phase shifter and the fixed phase shifter, wherein the pre-stage distributor is configured to distribute the first electrical signal input to the input terminal to the variable phase shifter and the fixed phase shifter, and the reference operation amount is preset as an operation amount for the reference variable phase shifter when the phase rotation amount of the reference variable phase shifter preset as a reference is set as the phase rotation amount of the fixed phase shifter.(Supplementary Note 7) The phase shifter according to Supplementary Note 5 or 6, wherein the other phase shifter in a first phase shifter among the plurality of phase shifters is the variable phase shifter included in a second phase shifter (such as a phase shifter arranged adjacent to the first phase shifter) different from the first phase shifter among the plurality of phase shifters, the control circuit applies a fixed manipulated variable to the other phase shifter, and the reference manipulated variable is the fixed manipulated variable. (Supplementary Note 8) The phase shifter according to any of Supplementary Notes 5 to 7, wherein the control circuit acquires the manipulated variable when the value of the fourth electrical signal is maximum as the manipulated variable when the phase difference becomes a value indicating 0. (Supplementary Note 9) Each divider including the pre-stage divider may include a directional coupler or a Wilkinson coupler. Also, the mixer may include a diode or a transistor.

[0073] 10...phase shifter, 11...distributor, 11A to 11B...transmission line, 11C...resistor, 12...variable phase shifter, 12ref...reference phase shifter, 12ref...variable phase shifter, 12X...variable phase shifter, 13...fixed phase shifter, 14...distributor, 14A...transmission line, 14B...transmission line, 14C...resistor, 15...mixer, 19...amplifier, 100...phased array, 110...antenna unit, 111...antenna, 112...wireless communication front end, 1 20...control circuit, 200...phased array, 210...phase shifter, 214A...distributor, 214B...distributor, 900...phased array, AN...antenna, B...beam, FE...wireless communication front end, T1...input terminal, T2...output terminal, Tc...control terminal, Tc1...control terminal, Tc2...control terminal, Ti...isolation terminal, Tin...input terminal, Tout...output terminal, Tr...transistor, U...antenna unit.

Claims

1. A phase shifter that rotates the phase of a first electrical signal, comprising: an input terminal, a variable phase shifter, a divider, a mixer, a low-pass filter, and an output terminal; the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by an amount of phase rotation corresponding to an operation amount; the divider is configured to distribute the first electrical signal, the phase of which has been changed by the variable phase shifter, to the output terminal and the mixer; the mixer is configured to multiply the first electrical signal distributed by the divider by a second electrical signal, which is the same as the first electrical signal but is supplied from a phase shifter different from the variable phase shifter and has its phase rotated by the other phase shifter, and output the resulting electrical signal to the low-pass filter as a third electrical signal; and the low-pass filter is configured to remove AC components from the third electrical signal from the mixer, and output a fourth electrical signal after the AC components have been removed.

2. The phase shifter according to claim 1, further comprising: a fixed phase shifter which is the other phase shifter; and a pre-stage divider provided in a stage preceding the variable phase shifter and the fixed phase shifter, wherein the pre-stage divider is configured to distribute the first electrical signal input to the input terminal to the variable phase shifter and the fixed phase shifter.

3. The phase shifter according to claim 1, wherein the other phase shifter is another variable phase shifter used together with the phase shifter according to claim 1.

4. A phased array comprising a plurality of phase shifters that rotate the phase of a first electrical signal supplied to an antenna, and a control circuit that controls the plurality of phase shifters, wherein each of the plurality of phase shifters comprises an input terminal, a variable phase shifter, a distributor, a mixer, a low-pass filter, and an output terminal, wherein the variable phase shifter is configured to change the phase of the first electrical signal input to the input terminal by a phase rotation amount corresponding to an operation amount, the distributor is configured to distribute the first electrical signal whose phase has been changed by the variable phase shifter to the output terminal and the mixer, and the mixer is configured to multiply the first electrical signal distributed by the distributor by a second electrical signal that is the same as the first electrical signal but whose phase has been rotated by the other phase shifter, and to output the resulting electrical signal to the low-pass filter as a third electrical signal, the low-pass filter is configured to remove AC components from the third electrical signal from the mixer and output a fourth electrical signal after the AC component removal; and the control circuit, for each of the plurality of phase shifters, changes the manipulated variable to obtain the manipulated variable when the value of the fourth electrical signal becomes a value indicating that the phase difference between the first electrical signal and the second electrical signal is 0, obtains a difference between the manipulated variable and a reference manipulated variable as a correction value, and supplies the manipulated variable corrected based on the correction value to the variable phase shifter when controlling the phase of the first electrical signal output from the output terminal.

5. The phase shifter according to claim 4, wherein each of the plurality of phase shifters further comprises an amplifier disposed between the variable phase shifter and the divider.

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