Phase shifter

Abstract

In a variable-reactance element (3) of a phase shifter (1), inductors (L1 to L4) are connected in parallel to capacitors (C1 to C4). First switches (Q11 to Q14) connect or disconnect the capacitors (C1 to C4) and a 90-degree hybrid coupler (2). Second switches (Q21 to Q24) connect or disconnect the inductors (L1 to L4) and the 90-degree hybrid coupler (2). A control unit (4) can switch between a first state in which at least one of the capacitors (C1 to C4) is in a connected state and all of the inductors (L1 to L4) are in a disconnected state, and a second state in which all of the capacitors (C1 to C4) are in a disconnected state and at least one of the inductors (L1 to L4) is in a connected state.

Description

phase shifter

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

[0002] A phase shifter for use in a microwave circuit is known, which uses a variable reactance element, such as a variable capacitor, a varicap, or a varactor diode (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 09-074325

[0004] When a phase shifter is used at a high frequency, the phase width becomes small and loss can become large. Therefore, in order to reduce the loss of the phase shifter, a variable capacitor with a larger variable range of reactance (½πfc) is required.

[0005] However, the variable reactance range of the variable capacitor is limited to the plus side relative to a phase shift of 0° (no phase shift), so the variable range of the phase of the phase shifter cannot be made sufficiently wide.

[0006] An object of the present invention is to provide a phase shifter with a wide variable phase range.

[0007] A phase shifter according to the present invention includes a 90-degree hybrid coupler, a first reactive element, a second reactive element, and a controller. The 90-degree hybrid coupler has an input terminal, an output terminal, a first reflecting terminal, and a second reflecting terminal. The first reactive element is connected to the first reflecting terminal. The second reactive element is connected to the second reflecting terminal. The controller controls the first reactive element and the second reactive element. Each of the first reactive element and the second reactive element includes at least one capacitor, at least one inductor, a first switch, and a second switch. The at least one inductor is connected in parallel with the at least one capacitor. The at least one first switch connects or disconnects the at least one capacitor to or from the 90-degree hybrid coupler. The at least one second switch connects or disconnects the at least one inductor to or from the 90-degree hybrid coupler. The controller is capable of controlling the at least one first switch and the at least one second switch. The control unit is capable of switching between a first state in which at least one capacitor is connected and all of the at least one inductor is disconnected, and a second state in which all of the at least one capacitor is disconnected and at least one inductor is connected. The control unit transfers a signal input to the input terminal and outputs it from the output terminal.

[0008] The phase shifter according to the present invention has a wide variable phase range.

[0009] FIG. 1 is a circuit diagram of a phase shifter according to a first embodiment. FIG. 2 is a circuit diagram of a first variable reactance element or a second variable reactance element of the phase shifter. FIG. 3 is a graph showing a change in phase shift amount with respect to a change in normalized characteristic impedance in the first variable reactance element or the second variable reactance element. FIG. 4 is a graph showing the magnitudes of S11 and S21 of the capacitor of the first variable reactance element or the second variable reactance element in the phase shifter according to a second embodiment. FIG. 5 is a graph showing the magnitudes of S11 and S21 of the inductor of the first variable reactance element or the second variable reactance element. FIG. 6 is an equivalent circuit diagram of a variable inductor in the phase shifter according to a third embodiment. FIG. 7 is a graph showing changes in the real part and the imaginary part of the complex permeability of the inductor with respect to frequency in the phase shifter according to a fourth embodiment. FIG. 8 is a circuit diagram of a phase shifter according to a fifth embodiment.

[0010] A first embodiment of the present invention will be described below with reference to the accompanying drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0011] 1. First Embodiment (1) Schematic Configuration of Phase Shifter A phase shifter 1 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram of the phase shifter according to the first embodiment. The phase shifter 1 is a device that shifts the phase of an RF output signal relative to an RF input signal.

[0012] The phase shifter 1 mainly includes a 90-degree hybrid coupler 2, a pair of variable reactance elements 3 (3A, 3B), and a control unit 4.

[0013] The 90-degree hybrid coupler 2 has an input terminal RF_IN, an output terminal RF_OUT, a first reflection terminal 7_OUT, a second reflection terminal 8_OUT, and a characteristic impedance Z ０ The first line 5 and the second line 6 are quarter wavelength lines of ０The 90-degree hybrid coupler 2 includes a third line 7 and a fourth line 8, which are quarter-wavelength lines of √√2. One end of the first line 5 is connected to the input terminal RF_IN, and the other end of the first line 5 is connected to the output terminal RF_OUT. One end of the second line 6 is connected to the first reflection terminal 7_OUT, and the other end of the second line 6 is connected to the second reflection terminal 8_OUT. One end of the third line 7 is connected to the input terminal RF_IN, and the other end of the third line 7 is connected to the first reflection terminal 7_OUT. One end of the fourth line 8 is connected to the output terminal RF_OUT, and the other end of the fourth line 8 is connected to the second reflection terminal 8_OUT. The 90-degree hybrid coupler 2 is a circuit that divides and combines RF input signals.

[0014] The first variable reactance element 3A and the second variable reactance element 3B are elements whose reactance changes. The first variable reactance element 3A and the second variable reactance element 3B of the variable reactance element 3 are connected to the first reflection terminal 7_OUT and the second reflection terminal 8_OUT, respectively.

[0015] In the 90-degree hybrid coupler 2, an RF signal input from the input terminal RF_IN is divided by the first line 5, the second line 6, the third line 7, and the fourth line 8 and transmitted to the first reflection terminal 7_OUT and the second reflection terminal 8_OUT. Since the first reflection terminal 7_OUT and the second reflection terminal 8_OUT are terminated by the variable reactance elements 3 (3A, 3B), the transmitted signal is reflected with a phase change that depends on the reactance of the variable reactance elements 3 (3A, 3B). The reflected signals are recombined by the first line 5, the second line 6, the third line 7, and the fourth line 8 and output from the output terminal RF_OUT. At this time, the output signal undergoes a phase change that depends on the reactance of the variable reactance element 3 (3A, 3B), and by changing the reactance of the variable reactance element 3 (3A, 3B), it operates as a phase shift circuit.

[0016] (2) Variable Reactance Element The first variable reactance element 3A and the second variable reactance element 3B have the same structure, and therefore, hereinafter, both will be described as the variable reactance element 3.

[0017] The variable reactance element 3 will be described with reference to Fig. 2. Fig. 2 is a circuit diagram of the first variable reactance element or the second variable reactance element of the phase shifter.

[0018] As shown in FIG. 2 , the variable reactance element 3 is connected to a ground G. The ground G refers to a reference conductive part having a reference potential or the reference potential itself. The reference potential is, for example, 0 V (zero volts). The reference conductive part may be formed using a conductor such as a metal.

[0019] The variable reactance element 3 has a plurality of (four in this embodiment) variable capacitors 11 (first to fourth variable capacitors 11A to 11D) connected in parallel, and a plurality of (four in this embodiment) variable inductors 12 (first to fourth variable inductors 12A to 12D).

[0020] The first variable capacitor 11A has a first switch Q11 and a capacitor C1 connected in series. The second variable capacitor 11B has a first switch Q12 and a capacitor C2 connected in series. The third variable capacitor 11C has a first switch Q13 and a capacitor C3 connected in series. The fourth variable capacitor 11D has a first switch Q14 and a capacitor C4 connected in series. The capacitances of the capacitors C1 to C4 are different from one another and increase in the order of capacitors C1, C2, C3, and C4. The first switches Q11 to Q14 are, for example, switching elements such as FETs (Field Effect Transistors). The first switches Q11 to Q14 can be switched between two states, on or off, independently of one another. This allows the variable capacitor 11 to be switched between two values: a first value which is the capacitance of the capacitors C1 to C4 (a state in which at least one of the first switches Q11 to Q14 is on, thereby connecting the variable capacitor 11 to the 90-degree hybrid coupler 2), or a second value in which the capacitance is 0 (a state in which the first switches Q11 to Q14 are off, thereby disconnecting the variable capacitor 11 from the 90-degree hybrid coupler 2).

[0021] The first variable inductor 12A has a second switch Q21 and an inductor L1 connected in series. The second variable inductor 12B has a second switch Q22 and an inductor L2 connected in series. The third variable inductor 12C has a second switch Q23 and an inductor L3 connected in series. The fourth variable inductor 12D has a second switch Q24 and an inductor L4 connected in series. The inductances of the inductors L1 to L4 are different from one another and increase in the order of L1, L2, L3, and L4. The second switches Q21 to Q24 are, for example, switching elements such as FETs (Field Effect Transistors). The second switches Q21 to Q24 can be switched between two states, on or off, independently of one another. As a result, the variable inductor 12 can be switched between two values: a first value which is the inductance of inductors L1 to L4 (a state in which at least one of the second switches Q21 to Q24 is on and the variable inductor 12 is connected to the 90-degree hybrid coupler 2), and a second value in which the inductance is 0 (a state in which all of the second switches Q21 to Q24 are off and the variable inductor 12 is disconnected from the 90-degree hybrid coupler 2).

[0022] (3) Control Configuration The control unit 4 changes the gate voltages applied to the first switches Q11 to Q14 and the second switches Q21 to Q24, thereby switching the first switches Q11 to Q14 and the second switches Q21 to Q24 between two states: on and off. As a result, the variable reactance element 3 switches the impedance with respect to the RF signal. As a result, the reflection coefficients seen from the first reflection terminal 7_OUT and the second reflection terminal 8_OUT change, causing the phase shifter 1 to change the phase of the RF signal.

[0023] The control unit 4 is a computer system having a processor (e.g., a CPU), a storage device (e.g., a ROM, a RAM, a HDD, an SSD, etc.), and various interfaces (e.g., an A / D converter, a D / A converter, a communication interface, etc.) The control unit 4 performs various control operations by executing programs stored in the storage device (corresponding to part or all of the storage area of ​​the storage device).

[0024] (4) Operation (4-1) Switching Between Connection and Disconnection of Variable Capacitor and Variable Inductor The state switching operation of the variable reactance element 3 by the control unit 4 will be described. When a gate voltage is applied to the first switches Q11 to Q14 and the second switches Q21 to Q24 in response to a command from the control unit 4 (when the gate voltage reaches or exceeds the threshold voltage level), the variable capacitor 11 and the variable inductor 12 enter a connected state. When the gate voltage to the first switches Q11 to Q14 and the second switches Q21 to Q24 is released in response to a command from the control unit 4 (when the gate voltage falls below the threshold voltage level), the variable capacitor 11 and the variable inductor 12 enter a disconnected state.

[0025] (4-2) State Switching of Variable Reactance Elements The change in the amount of phase shift when the state of the variable reactance element 3 (3A, 3B) is switched will be described using Figures 2 and 3. Figure 3 is a graph showing the change in the amount of phase shift with respect to the change in normalized characteristic impedance in the first variable reactance element or the second variable reactance element. In Figure 3, as an example, L is in the range of 0.06 nH to 28 nH (e.g., L1 = 0.06 nH, L4 = 28 nH in Figure 2), C is 0.1 pF to 22 pF (e.g., C1 = 0.1 pF, C4 = 22 pF), and the frequency is 5.8 GHz.

[0026] The control unit 4 can switch the variable reactance element 3 between the following three states. In the first state (capacitance state), only one of the first to fourth variable capacitors 11A to 11D is connected, and all of the first to fourth variable inductors 12A to 12D are disconnected. In this case, the reactance of one of the capacitors C1, C2, C3, and C4 that is connected becomes the reactance of the variable reactance element 3. If a state in which there is no phase shift is defined as a phase shift amount of 0°, then in this case the phase shift amount is positive.

[0027] In the second state (inductance state), all of the first to fourth variable capacitors 11A to 11D are disconnected, and one of the first to fourth variable inductors 12A to 12D is connected. In this case, the reactance of one of the inductors L1, L2, L3, and L4 that is connected becomes the reactance of the variable reactance element 3. If a state in which there is no phase shift is defined as a phase shift amount of 0°, then in this case the phase shift amount becomes negative.

[0028] In the third state (state without phase shift control), all of the first to fourth variable capacitors 11A to 11D are in a disconnected state, and all of the first to fourth variable inductors 12A to 12D are in a disconnected state. In this state, no phase shift control is performed.

[0029] In this embodiment, by using the variable reactance element 3 (3A, 3B) as described above, the susceptance can be changed from −∞ to ∞, at which point the phase change amount of the phase shifter 1 is 360 degrees. That is, by using the first to fourth variable capacitors 11A to 11D and the first to fourth variable inductors 12A to 12D, each having a finite variable width, it is possible to realize a phase shift circuit that provides a phase change amount of 360 degrees in one stage.

[0030] 3, the capacitances of the capacitors C1 to C4 and the inductors L1 to L4 are all set to values ​​that do not achieve a phase shift of 0° or a predetermined range around 0°, that is, −5° to +5°. As a result, resonance of the phase shifter 1 around 0° can be suppressed, and loss can be reduced.

[0031] (5) Effects A number of effects of this embodiment will be described below. These effects may be obtained individually or in combination.

[0032] As described above, the capacitor and the inductor are selectively connected. Specifically, when setting the phase shift amount, only one capacitor or one inductor is selected. Between the first state in which the capacitor is connected and the second state in which the inductor is connected, the phase can be shifted to the opposite side of the 0° phase shift amount. In other words, not only the capacitance but also the inductance can be varied, and the reactance can be varied over a wide range from capacitive (½πfc) to inductive (2πfL). Therefore, the variable range of the reactance (½πfc + 2πfL) can be widened. As a result, a low-loss, high-frequency (RF) phase shifter with a large phase shift range can be realized, for example, a 360° phase shift can be achieved.

[0033] In the variable reactance element 3 (3A, 3B), the first to fourth variable capacitors 11A to 11D and the first to fourth variable inductors 12A to 12D are configured in a single stage. In other words, the first to fourth variable capacitors 11A to 11D and the first to fourth variable inductors 12A to 12D are not connected in series with other variable reactance elements but are connected to ground G. As a result, the phase shifter 1 has low loss and can be reduced in size. In the past, it was not possible to perform a 360° phase shift without using, for example, a multi-stage configuration or a configuration using resonance. This resulted in problems such as increased loss and large size in the phase shifter.

[0034] 2. Second Embodiment A second embodiment will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a graph showing the magnitudes of S11 and S21 of the capacitor of the first variable reactance element or the second variable reactance element in a phase shifter according to the second embodiment. Fig. 5 is a graph showing the magnitudes of S11 and S21 of the inductor of the first variable reactance element or the second variable reactance element.

[0035] FIG. 4 shows the changes in S11 (reflection coefficient) and S21 (transmission coefficient) with respect to the capacitance of the capacitors in phase shifter 1. As is clear from the figure, the S parameters of capacitors C1 to C4 are such that S21 > S11. This relationship is maintained even if the capacitance of capacitors C1 to C4 changes. By maintaining this relationship, the phase shifter can achieve a more appropriate phase shift. The difference between S21 and S11 is preferably in the range of 80 to 95 degrees, and more preferably in the range of 85 to 95 degrees.

[0036] FIG. 5 shows the changes in S11 and S21 with respect to the inductance of the inductors. In the S parameters of inductors L1 to L2, S11>S21. Even if the capacitance of inductors L1 to L4 changes, the relationship S11>S21 is maintained. By maintaining this relationship, the phase shifter can achieve a more appropriate phase shift amount. The difference between S11 and S21 is preferably in the range of 80 to 95 degrees, and more preferably in the range of 85 to 95 degrees. With the above configuration, a wide phase width of the phase shifter 1 can be ensured.

[0037] 3. Third Embodiment A third embodiment will be described with reference to Fig. 6. Fig. 6 is an equivalent circuit diagram of a variable inductor in a phase shifter according to the third embodiment.

[0038] 6 shows the first variable inductor 12A. Specifically, the second switch Q21 is shown in an equivalent circuit, and is made up of a resistance R and a parasitic capacitance C.

[0039] In this embodiment, when the second switch Q21 is in a connected state, a current flows on the second switch Q21 side of the inductor L5, and no current or a small amount of current flows on the side of the inductor L5 opposite the second switch Q21.

[0040] The current flowing on the side of the inductor L1 opposite to the second switch Q21 is preferably 0 to 50%, and more preferably 1 to 10%, of the current flowing on the second switch Q21 side of the inductor L1.

[0041] As a result, the loss of the inductor L1 can be reduced, and as a result, the loss as a reflective phase shifter can be reduced. Therefore, the inductor can be made smaller. Note that the above configuration can also be applied to the second to fourth variable inductors 12B to 12D.

[0042] 4. Fourth Embodiment A fourth embodiment will be described with reference to Fig. 7. Fig. 7 is a graph showing changes in the real and imaginary parts of the complex permeability of an inductor with respect to frequency in a phase shifter according to the fourth embodiment. Note that the fourth embodiment is based on the configuration and operation of the first, second, or third embodiment, with other configuration limitations.

[0043] FIG. 7 shows the change in the real part (μ') and imaginary part (μ'') of the complex permeability of the inductance with respect to the change in frequency. As is clear from the figure, in the low frequency region, there is a first frequency region 101 where the real part is larger than the imaginary part. In the high frequency region, there is a second frequency region 102 where the imaginary part is larger than the real part.

[0044] As shown in Figure 7, the self-resonant frequency SRF of the inductor of the phase shifter 1 is outside the drive frequency range A. The drive frequency range A is a frequency range between 0.9 x (c / λ) and 1.1 x (c / λ). c is the speed of light, measured in m / second. λ is measured in m. The center frequency of the drive frequency range A is (c / λ). Therefore, in the drive frequency range A, an ideal impedance state can be achieved in the phase shifter 1, and loss is stably reduced.

[0045] Furthermore, at least one of the real part and imaginary part of the complex permeability of the inductor is set so that the amount of change is 10% or less in the drive frequency region A. Therefore, an ideal impedance state can be achieved in a reflective phase shifter, and loss is stably reduced in the drive frequency region A.

[0046] Furthermore, in the second frequency domain 102, the imaginary part of the complex permeability has at least a part that is greater than the maximum value of the real part of the complex permeability in the first frequency domain 101. As a result, it is possible to suppress a decrease in the amount of phase shift at high frequencies of 3 GHz or higher.

[0047] 5. Fifth Embodiment In the first embodiment, the variable reactance element includes a plurality of variable capacitors and a plurality of variable inductors. However, the variable reactance element may include one variable capacitor and one variable inductor, and the two may be selected alternatively.

[0048] Such an example will be described as a fifth embodiment with reference to Fig. 8. Fig. 8 is a circuit diagram of a phase shifter according to the fifth embodiment.

[0049] As shown in FIG. 8, a variable reactance element 3E has one variable capacitor 11E and one variable inductor 12E connected in parallel.

[0050] The variable capacitor 11E includes a first switch Q15 and a capacitor C5 connected in series to each other.

[0051] The variable inductor 12E has a second switch Q25 and an inductor L5 connected in series with each other.

[0052] The control unit can switch the variable reactance element 3E between the following three states. In the first state (capacitance state), the variable capacitor 11E is connected and the variable inductor 12E is disconnected. In this state, the reactance of the variable capacitor 11E becomes the reactance of the variable reactance element 3E. If the state without phase shift is defined as a phase shift amount of 0°, in this case the phase shift amount is positive.

[0053] In the second state (inductance state), the variable capacitor 11E is disconnected and the variable inductor 12E is connected. In this case, the reactance of the variable inductor 12E becomes the reactance of the variable reactance element 3E. If a state without phase shift is defined as a phase shift amount of 0°, in this case the phase shift amount becomes negative.

[0054] In the third state (state without phase shift control), the variable capacitor 11E is off and the variable inductor 12E is off, and in this state, no phase shift control is performed.

[0055] 6. Sixth Embodiment In the first to fifth embodiments, among the plurality of capacitors and the plurality of inductors, only one capacitor or only one inductor is in a connected state.

[0056] In other embodiments, multiple capacitors may be connected or multiple inductors may be connected, in which case the multiple capacitors may include two or more capacitors with the same capacitance, or the multiple inductors may include two or more inductors with the same inductance.

[0057] In this embodiment, by connecting a plurality of capacitors simultaneously, it is possible to perform a fine phase shift by combining them. Also, in this embodiment, by connecting a plurality of inductors simultaneously, it is possible to perform a fine phase shift by combining them.

[0058] 7. Modifications Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes and modifications are possible.

[0059] The number of variable capacitors and variable inductors of the variable reactance elements is not limited to that in the above embodiment.

[0060] The number of variable capacitors and the number of variable inductors may be different.

[0061] REFERENCE SIGNS LIST 1 Phase shifter 2 90-degree hybrid coupler 3 Variable reactance element 3A First variable reactance element 3B Second variable reactance element 11 Variable capacitor 11A First variable inductor 11B Second variable inductor 11C Third variable inductor 11D Fourth variable inductor 12 Variable inductor 12A First variable inductor 12B Second variable inductor 12C Third variable inductor 12D Fourth variable inductor Q1 First switch Q2 Second switch

Claims

1. A 90-degree hybrid coupler having an input terminal, an output terminal, a first reflecting terminal, and a second reflecting terminal; a first variable reactance element connected to the first reflecting terminal; a second variable reactance element connected to the second reflecting terminal; and a control unit that controls the first variable reactance element and the second variable reactance element, wherein each of the first variable reactance element and the second variable reactance element has: at least one capacitor; at least one inductor connected in parallel to the at least one capacitor; at least one first switch that connects or disconnects the at least one capacitor and the 90-degree hybrid coupler; and at least one second switch that connects or disconnects the at least one inductor and the 90-degree hybrid coupler, and the control unit a phase shifter, the phase shifter being capable of controlling the at least one first switch and the at least one second switch, and capable of switching between a first state in which the at least one capacitor is connected and all of the at least one inductor is disconnected, and a second state in which all of the at least one capacitor is disconnected and the at least one inductor is connected; and shifting a signal input to the input terminal and outputting it from the output terminal.

2. The phase shifter according to claim 1, wherein the control unit connects only one of the at least one capacitor in the first state, and the control unit connects only one of the at least one inductor in the second state.

3. The phase shifter according to claim 1 or 2, wherein each of the first variable reactance element and the second variable reactance element is connected to ground.

4. A phase shifter according to any one of claims 1 to 3, wherein the S parameters of the at least one capacitor satisfy S21 (transmission coefficient) > S11 (reflection coefficient), and the S parameters of the at least one inductor satisfy S11 (reflection coefficient) > S21 (transmission coefficient).

5. The phase shifter according to any one of claims 1 to 4, wherein the 90-degree hybrid coupler comprises: a first line having a line length of λ / 4 and a characteristic impedance of Z0 connected between the input terminal and the output terminal; a second line having a line length of λ / 4 and a characteristic impedance of Z0 connected between the first reflection terminal and the second reflection terminal; a third line having a line length of λ / 4 and a characteristic impedance of Z0 / √2 connected between the input terminal and the first reflection terminal; and a fourth line having a line length of λ / 4 and a characteristic impedance of Z0 / √2 connected between the output terminal and the second reflection terminal; and wherein the self-resonant frequency of the at least one inductor is outside the frequency range of 0.9 × (c / λ) or more and 1.1 × (c / λ) or less.

6. A phase shifter according to any one of claims 1 to 5, wherein at least one of the real part and imaginary part of the complex permeability of said at least one inductor is set so that the amount of change is 10% or less in the frequency range of 0.9 × (c / λ) or more and 1.1 × (c / λ) or less.

7. A phase shifter according to claim 6, wherein in a first frequency range, the value of the imaginary part of the complex permeability of the at least one inductor is smaller than the value of the real part, and in a second frequency range higher than the first frequency range, at least a portion of the imaginary part of the complex permeability of the at least one inductor has a value greater than the maximum value of the real part of the complex permeability in the first frequency range.

8. A phase shifter according to any one of claims 1 to 7, wherein, when the second switch is on, a current flows through the at least one inductor on the second switch side, and no current or a very small amount of current flows through the at least one inductor on the side opposite the second switch.

9. A phase shifter according to any one of claims 1 to 8, wherein the capacitance of said at least one capacitor and the inductance of said at least one inductor are set to values ​​that do not cause the phase shift of said signal to fall within 0° or a predetermined range around 0°.

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