Digital variable reactance element, phase shifter, and impedance matching circuit

Abstract

A digital variable reactance element with variable width is provided. A digital variable reactance element (1) is provided with a plurality of digital capacitors (2) and a plurality of digital inductors (4), the plurality of digital capacitors (2) and the plurality of digital inductors (4) are connected in series or in parallel, and each of the plurality of digital capacitors (2) has a capacitor (C1) and a first digital switch (Q) connected in series or in parallel. The first digital switch (Q) can be switched between an on state and an off state, each of the plurality of digital inductors (4) has an inductor (L1) and a second digital switch (Q) which are connected in series or in parallel, and the second digital switch (Q) can be switched between an on state and an off state.

Description

Technical Field

[0001] The invention relates to a digital variable reactance element, a phase shifter and an impedance matching circuit. Background Art

[0002] For example, a variable reactance element is used in a phase shifter used in a microwave circuit. As such a variable reactance element, a variable capacitor such as a variable capacitor, a voltage-controlled varactor, or a varactor diode is known (see, for example, Patent Document 1).

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 09-074325 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] When the frequency f increases as in a high-frequency phase shifter, the phase shift width of the phase shifter decreases and the loss increases. Therefore, a variable reactance element with a variable width having a larger reactance (1 / 2πfc) is desired.

[0008] In addition, as a variable reactance element, there is a variable inductor. However, conventional variable reactance elements use only one of a variable capacitor and a variable inductor.

[0009] like Figure 8 As shown in the Smith chart, when a capacitor is inserted or the capacitance increases, the reactance (impedance) changes in the direction of the arrow D_C. On the other hand, when an inductor is inserted or the inductance increases, the reactance (impedance) changes in the direction of the arrow D_L. In this way, the change in reactance caused by the variable capacitor and the change in reactance caused by the variable inductor are changes in one direction that are different from each other.

[0010] Therefore, in the case of controlling the variable width of the reactance more widely, it is necessary to use a plurality of variable capacitors or a plurality of variable inductors, and control signals of the plurality of variable capacitors or the plurality of variable inductors are complicated.

[0011] Therefore, an object of the present invention is to provide a digital variable reactance element, a phase shifter, and an impedance matching circuit with a wide variable width.

[0012] Technical solutions to solve problems

[0013] The digital variable reactance element involved in the present invention is a digital variable reactance element that digitally changes reactance, and is provided with a plurality of digital capacitors and a plurality of digital inductors. The plurality of digital capacitors are connected in series or in parallel with the plurality of digital inductors. The plurality of digital capacitors respectively include capacitors connected in series or in parallel and a first digital switch, and the first digital switch can be switched to two states of an on state or an off state. The plurality of digital inductors respectively include an inductor connected in series or in parallel and a second digital switch, and the second digital switch can be switched to two states of an on state or an off state.

[0014] The phase shifter according to the present invention includes the above-mentioned digital variable reactance element, and generates an output signal in which the phase of an input signal is digitally changed.

[0015] The impedance matching circuit according to the present invention includes the above-mentioned digital variable reactance element and matches the characteristic impedance of a connected line.

[0016] Effects of the Invention

[0017] According to the present invention, the variable width of a digital variable reactance element can be expanded. According to the present invention, the phase shift width of a phase shifter can be expanded. According to the present invention, the matching width of an impedance matching circuit can be expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : is a circuit diagram showing a digital variable reactance element according to the present embodiment.

[0019] Figure 2 : is a circuit diagram showing a digital variable reactance element according to Modification 1 of the present embodiment.

[0020] Figure 3 : is a circuit diagram showing a digital variable reactance element according to a second modification of the present embodiment.

[0021] Figure 4 : is a circuit diagram showing an example of the phase shifter according to the present embodiment.

[0022] Figure 5 : is a circuit diagram showing another example of the phase shifter according to the present embodiment.

[0023] Figure 6 It is shown Figure 4 A diagram showing a design of an example of a phase shifter shown.

[0024] Figure 7 : is a circuit diagram showing an example of the impedance matching circuit according to the present embodiment.

[0025] Figure 8is a Smith chart showing an example of reactance characteristics. DETAILED DESCRIPTION

[0026] Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. It should be noted that the same reference numerals are given to the same or corresponding parts in each drawing.

[0027] (Digital variable reactance element of this embodiment)

[0028] Figure 1 FIG. 1 is a circuit diagram showing a digital variable reactance element according to the present embodiment. Figure 1 As shown, the digital variable reactance element 1 is an element that digitally changes reactance. The digital variable reactance element 1 includes a plurality of digital capacitors 2 and a plurality of digital inductors 4. It should be noted that the digital variable reactance element 1 may also include a digital resistor 6. In the digital variable reactance element 1, the plurality of digital capacitors 2, the plurality of digital inductors 4, and the digital resistor 6 are connected in parallel.

[0029] The digital capacitor 2 has a capacitor C1 and a digital switch (first digital switch) Q connected in series. The digital switch Q is not particularly limited, but a switching element such as a FET (Field Effect Transistor) can be used. The digital switch Q can be switched to two states: an on state and an off state. Thus, the digital capacitor 2 can be switched to two values: a first value as the capacitance of the capacitor C1 (the digital switch Q is in the on state) or a second value as the capacitance 0 (the digital switch Q is in the off state). That is, the digital capacitor 2 can digitally switch the capacitance.

[0030] The digital inductor 4 includes an inductor L1 and a digital switch (second digital switch) Q connected in series. The digital switch Q is not particularly limited, but a switch element such as a FET (Field Effect Transistor) can be used. The digital switch Q can be switched to two states: an on state and an off state. Thus, the digital inductor 4 can be switched to two values: a first value as the inductance of the inductor L1 (the digital switch Q is in the on state) or a second value as the inductance 0 (the digital switch Q is in the off state). That is, the digital inductor 4 can digitally switch the inductance.

[0031] The digital resistor 6 has a resistor R1 and a digital switch Q connected in series. The digital switch Q is not particularly limited, but a switching element such as a FET (Field Effect Transistor) can be used. The digital switch Q can be switched to two states: an on state and an off state. Thus, the digital resistor 6 can be switched to two values: a first value as the resistance value of the resistor R1 (the digital switch Q is in the on state) or a second value as the resistance value 0 (the digital switch Q is in the off state). That is, the digital resistor 6 can digitally switch the resistance value.

[0032] Thus, the variable reactance element 1 can digitally change the reactance by switching the on state or the off state of each digital switch Q.

[0033] Furthermore, the variable reactance element 1 can digitally change the impedance, especially the impedance to the RF signal (high frequency signal), by switching the on state or the off state of each digital switch Q.

[0034] As described above, according to the digital variable reactance element 1 of the present embodiment, the reactance generated by the plurality of capacitors C1 and the plurality of inductors L1 can be digitally changed by controlling the digital switch Q. In addition, according to the digital variable reactance element 1, the impedance generated by the plurality of capacitors C1, the plurality of inductors L1, and the resistor R1 can be digitally changed by controlling the digital switch Q.

[0035] In addition, not only capacitance but also inductance can be changed, and reactance can be changed widely from capacitive (1 / 2πfc) to inductive (2πfL). Therefore, the variable width of reactance (1 / 2πfc+2πfL) can be expanded.

[0036] In addition, a plurality of variable capacitors or a plurality of variable inductors are not used, and control signals of the plurality of variable capacitors or the plurality of variable inductors do not become complicated.

[0037] In addition, a high-frequency (RF) phase shifter with low loss and a large phase shift width can be realized.

[0038] In the above-mentioned embodiment, each digital capacitor 2 has a capacitor C1 and a digital switch Q connected in series, each digital inductor 4 has an inductor and a digital switch connected in series or in parallel, and a plurality of digital capacitors 2 are connected in parallel with a plurality of digital inductors 4. However, the present invention is not limited to this, and can be applied to various variable reactance elements in which each digital capacitor has a capacitor and a digital switch connected in series or in parallel, each digital inductor has an inductor and a digital switch connected in series or in parallel, and a plurality of digital capacitors are connected in series or in parallel with a plurality of digital inductors. For example, the following exemplifies Modifications 1 and 2 of the present embodiment.

[0039] (Digital variable reactance element of modification 1)

[0040] Figure 2 FIG. 1 is a circuit diagram showing a digital variable reactance element according to a first variation of the present embodiment. Figure 2 As shown, the digital variable reactance element 1A is an element that digitally changes reactance. The digital variable reactance element 1A includes a plurality of digital capacitors 2A and a plurality of digital inductors 4A. It should be noted that the digital variable reactance element 1A may also include a digital resistor 6A. In the digital variable reactance element 1A, a plurality of digital capacitors 2A, a plurality of digital inductors 4A, and a digital resistor 6A are connected in series.

[0041] The digital capacitor 2A has a capacitor C1 and a digital switch (first digital switch) Q connected in series, and has a capacitor C2 and the digital switch Q connected in parallel. Specifically, in the digital capacitor 2A, the series circuit of the capacitor C1 and the digital switch Q is connected in parallel with the capacitor C2. The digital switch Q is the same as described above. As a result, the digital capacitor 2A can switch between two values: a first value (digital switch Q is in the on state) as the combined capacitance of the capacitor C1 and the capacitor C2, or a second value (digital switch Q is in the off state) as the capacitance of the capacitor C2. That is, the digital capacitor 2A can digitally switch the capacitance.

[0042] The digital inductor 4A includes an inductor L1 and a digital switch (second digital switch) Q connected in series, and an inductor L2 and the digital switch Q connected in parallel. Specifically, in the digital inductor 4A, a series circuit of the inductor L1 and the digital switch Q is connected in parallel to the inductor L2. The digital switch Q is the same as described above. Thus, the digital inductor 4A can switch between two values: a first value (the digital switch Q is in the on state) which is a combined inductance of the inductor L1 and the inductor L2, or a second value (the digital switch Q is in the off state) which is an inductance of the inductor L2. That is, the digital inductor 4A can digitally switch the inductance.

[0043] The digital resistor 6A includes a resistor R1 and a digital switch Q connected in parallel. The digital switch Q is the same as described above. Thus, the digital resistor 6A can switch between two values: a first value of 0 (digital switch Q is in an on state) or a second value of the resistance value of the resistor R1 (digital switch Q is in an off state). That is, the digital resistor 6A can digitally switch the resistance value.

[0044] Thus, the variable reactance element 1A can digitally change the reactance by switching the on state or the off state of each digital switch Q.

[0045] Furthermore, the variable reactance element 1A can digitally change the impedance, in particular, the impedance to the RF signal (high frequency signal), by switching the on state or the off state of each digital switch Q.

[0046] The digital variable reactance element 1A according to the first modification also has the same advantages as the digital variable reactance element 1 according to the present embodiment described above.

[0047] (Digital variable reactance element of modification 2)

[0048] Figure 3 FIG. 4 is a circuit diagram showing a digital variable reactance element according to a second variation of the present embodiment. Figure 3 As shown, the digital variable reactance element 1B is an element that digitally changes reactance. The digital variable reactance element 1B includes a plurality of the above-mentioned digital capacitors 2A and a plurality of the above-mentioned digital inductors 4. In the digital variable reactance element 1B, the plurality of digital capacitors 2A are connected in series, the plurality of digital inductors 4 are connected in parallel, and the series circuit of the digital capacitors 2A and the parallel circuit of the digital inductors 4 are connected in series.

[0049] Thus, the variable reactance element 1B can digitally change the reactance by switching the on state or the off state of each digital switch Q.

[0050] Furthermore, the variable reactance element 1B can digitally change the impedance, in particular, the impedance to the RF signal (high frequency signal), by switching the on state or the off state of each digital switch Q.

[0051] The digital variable reactance element 1B according to the second modification also has the same advantages as the digital variable reactance element 1 according to the present embodiment described above.

[0052] The following describes a phase shifter and an impedance matching circuit as an example of a device to which the digital variable reactance element is applied. It should be noted that the digital variable reactance element of the present embodiment is not limited thereto, and can be applied to various devices that require a change in reactance or impedance, such as a variable load, a detector circuit of MRI (Magnetic Resonance Imaging), a VCO (Voltage Controlled Oscillator), a phase synchronization circuit, and a frequency synthesizer.

[0053] (Phase Shifter of This Embodiment)

[0054] Figure 4 is a circuit diagram showing an example of a phase shifter according to this embodiment. Figure 5 : is a circuit diagram showing another example of the phase shifter according to the present embodiment. Figure 4 The phase shifter 10 shown is a hybrid coupled type high frequency (RF) phase shifter composed of 1 / 4 wavelength lines 11 and 12 with characteristic impedance Z0 and 1 / 4 wavelength lines 13 and 14 with characteristic impedance Z0 / √2. The phase shifter 10 sets one end side of the line 11 as an input terminal RF_IN and the other end side of the line 11 as an output terminal RF_OUT. The phase shifter 10 includes the above-mentioned variable reactance element 1 (1A, 1B) which terminates the output terminal 13_OUT on the line 13 side and the output terminal 14_OUT on the line 14 side, respectively.

[0055] In the phase shifter 10, the RF signal input from the input terminal RF_IN is distributed by the hybrid coupled lines 11, 12, 13, and 14, and transmitted to the output terminal 13_OUT on the line 13 side and the output terminal 14_OUT on the line 14 side. These output terminals 13_OUT and 14_OUT are terminated by the variable reactance element 1 (1A, 1B) described above, so the signals transmitted to these output terminals are reflected by the phase change depending on the reactance of the variable reactance element 1 (1A, 1B). The signals reflected at these output terminals 13_OUT and 14_OUT are synthesized again by the hybrid coupled lines 11, 12, 13, and 14, and output from the output terminal RF_OUT. At this time, the output signal is subjected to the phase change depending on the reactance of the variable reactance element 1 (1A, 1B), and the reactance of the variable reactance element is changed, so that the phase shifter is operated.

[0056] It should be noted that Figure 4An example in which the variable reactance element 1 (1A, 1B) is applied to a hybrid coupled phase shifter 10 is shown. Figure 5 As shown, the variable reactance element 1 ( 1A, 1B) described above may be applied to a loaded line type phase shifter 10 composed of a quarter wavelength line 11 having a characteristic impedance of Z0.

[0057] Figure 6 It is shown Figure 4 FIG. 1 is a diagram showing an example of a phase shifter design. Figure 6 In this paper, the capacitance C of the digital capacitor or the inductance L of the digital inductor is changed, and the network analyzer is used to measure the Figure 4 The phase shift ps of the phase shifter is shown. Figure 6 As shown, a phase shift characteristic of approximately 360° is obtained. Thus, according to the high-frequency phase shifter using the digital variable reactance element of the above-mentioned embodiment, the reactance can be widely changed in both the capacitive and inductive properties, thereby realizing a high-frequency (RF) phase shifter with low loss and a large phase shift width.

[0058] (Matching Circuit of This Embodiment)

[0059] Figure 7 : is a circuit diagram showing an example of the impedance matching circuit according to the present embodiment. Figure 7 The impedance matching circuit 20 shown includes an inductor 21 connected in series between one input terminal RF_IN+ of a pair of input terminals RF_IN+, RF_IN- and one output terminal RF_OUT+ of a pair of output terminals RF_OUT+, RF_OUT-, and the above-mentioned variable reactance element 1 (1A, 1B) connected between the pair of input terminals RF_IN+, RF_IN- and between the pair of output terminals RF_OUT+, RF_OUT-, respectively.

[0060] The impedance matching circuit 20 operates as an impedance matching circuit by changing the impedance amount of the variable reactance element 1 ( 1A, 1B) described above.

[0061] As described above, according to the impedance matching circuit to which the digital variable reactance element of the above-described embodiment is applied, reactance can be widely changed in both capacitive and inductive properties, thereby realizing an impedance matching circuit with low loss and a wide impedance adjustment range.

[0062] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes and deformation|transformation are possible.

[0063] Description of Reference Numerals

[0064] 1, 1A, 1B digital variable reactance element;

[0065] 2. 2A digital capacitor;

[0066] 4. 4A digital inductor;

[0067] 6. 6A digital resistor;

[0068] C1, C2 capacitors;

[0069] L1, L2 inductors;

[0070] R1 resistor;

[0071] Q Digital switch;

[0072] 10 Phase Shifter;

[0073] 20 Impedance matching circuit.

Claims

1. A digital variable reactance element that digitally changes reactance, wherein: The digital variable reactance element includes a plurality of digital capacitors and a plurality of digital inductors. The plurality of digital capacitors are connected in series or in parallel with the plurality of digital inductors, The plurality of digital capacitors each include a capacitor connected in series or in parallel and a first digital switch, wherein the first digital switch can be switched between two states: an on state and an off state. Each of the plurality of digital inductors includes an inductor connected in series or in parallel and a second digital switch that can be switched between two states: an on state and an off state.

2. A phase shifter comprising the digital variable reactance element according to claim 1, The phase shifter generates an output signal that digitally shifts the phase of an input signal.

3. An impedance matching circuit comprising the digital variable reactance element according to claim 1, The impedance matching circuit matches the characteristic impedance of the connected line.

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