RF phase shifter

Abstract

Provided is an RF phase shifter capable of highly accurate phase control. An RF phase shifter 100 comprises: a phase shifter 110 that receives an input RF signal, generates an output RF signal in which the phase of the input RF signal is changed to a set phase in accordance with a control voltage, and outputs the output RF signal; a phase comparator 120 that generates a phase difference voltage according to a phase difference between the input RF signal and the output RF signal; and an arithmetic processing unit 130 that generates a control voltage according to a voltage difference between the phase difference voltage and a reference voltage according to the set phase.

Description

Technical Field

[0001] The present invention relates to an RF phase shifter.

Background Art

[0002] An RF (radio frequency) phase shifter that generates an output RF signal obtained by changing the phase of an input RF signal to a set phase is known (see, for example, Patent Document 1).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] High-precision phase control is required for such RF phase shifters. As a method for improving the phase control accuracy of an RF phase shifter, fine phase shift control can be considered. However, in conventional RF phase shifters, there is an error of several degrees between the set phase and the output phase, resulting in low phase control accuracy. Therefore, the true value of the output phase is unknown, and it is difficult to ensure the accuracy of phase control.

[0005] Accordingly, an object of the present invention is to provide an RF phase shifter capable of high-precision phase control.

Means for Solving the Problem

[0006] An RF phase shifter according to the present invention includes: a phase shifter that receives an input RF signal, generates an output RF signal obtained by changing the phase of the input RF signal to a set phase in accordance with a control voltage, and outputs the output RF signal; a phase comparator that generates a phase difference voltage corresponding to a phase difference between the input RF signal and the output RF signal; and an arithmetic processing unit that generates the control voltage corresponding to a voltage difference between the phase difference voltage and a reference voltage corresponding to the set phase.

[0007] Another RF phase shifter according to the present invention includes a digital phase shifter that receives an input RF signal, generates an output RF signal by changing the phase of the input RF signal to a set phase according to a digital control signal, and outputs the output RF signal; a phase comparator that generates a phase difference voltage according to the phase difference between the input RF signal and the output RF signal; and an arithmetic processing unit that generates the digital control signal according to the voltage difference between the phase difference voltage and a reference voltage according to the set phase. [Effects of the Invention]

[0008] According to the present invention, high-precision phase control becomes possible in an RF phase shifter. [Brief explanation of the drawing]

[0009] [Figure 1] This is a conceptual diagram showing an RF phase shifter according to this embodiment. [Figure 2] This is a circuit diagram showing an RF phase shifter (analog type) according to the first embodiment. [Figure 3] This is a circuit diagram showing an RF phase shifter (digital type) according to the second embodiment. [Figure 4] Figure 3 is a circuit diagram showing an example of a digital phase shifter in an RF phase shifter. [Figure 5] Figure 3 shows another example of a digital phase shifter in the RF phase shifter. [Figure 6] Figure 4 or Figure 5 shows a circuit diagram illustrating an example of a variable reactance element (digital type) in a phase shifter. [Figure 7] This is a circuit diagram showing another example of a variable reactance element (digital type) in the phase shifter shown in Figure 4 or Figure 5. [Figure 8] This is a circuit diagram showing another example of a variable reactance element (digital type) in the phase shifter shown in Figure 4 or Figure 5. [Modes for carrying out the invention]

[0010] Hereinafter, an example of an embodiment of the present invention will be described with reference to the attached drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0011] [First Embodiment] (RF phase shifter) Figure 1 is a conceptual diagram showing an RF phase shifter according to this embodiment, and Figure 2 is a circuit diagram showing an RF phase shifter according to the first embodiment. The RF phase shifter 100 shown in Figures 1 and 2 comprises an analog phase shifter 110, a phase comparator 120, and an analog arithmetic processing unit 130. Furthermore, as shown in Figure 2, the RF phase shifter 100 may also include branchers 141 and 142.

[0012] The splitter 141 splits the RF signal input to the RF_IN input terminal of the RF phase shifter 100 into the input RF signal for the phase shifter 110 and the input RF signal for the phase comparator 120.

[0013] The splitter 142 splits the output RF signal of the phase shifter 110 into an output RF signal for the phase comparator 120 and an RF signal output from the RF_OUT output terminal of the RF phase shifter 100.

[0014] The phase shifter 110 is an analog phase shifter. The phase shifter 110 receives an input RF signal, generates an output RF signal by changing the phase of the input RF signal to a set phase according to the control voltage, and outputs the output RF signal.

[0015] The phase comparator 120 is a high-precision phase comparator. The phase comparator 120 compares the phase of the input RF signal with the phase of the output RF signal and generates a voltage with a voltage value corresponding to the phase difference between them. This voltage is called the phase difference voltage.

[0016] The arithmetic processing unit 130 is an analog arithmetic processing unit and includes an operational amplifier 132. One input of the operational amplifier 132 is connected to the output of the phase comparator 120. The other input of the operational amplifier 132 is connected to the midpoint between resistors 133 and 134 connected in series between the reference voltage line V_Phase ref and the ground line GND. Furthermore, the output of the operational amplifier 132 is feedback-connected to one input of the operational amplifier 132 via a capacitor 136 in series.

[0017] A phase difference voltage V_Δphase is input to one input of the operational amplifier 132. A reference voltage V_Phase ref, specifically the reference voltage V_Phase ref divided by the resistors 133 and 134, is input to the other input of the operational amplifier 132. The reference voltage V_Phase ref is a voltage corresponding to a set phase of the phase shifter 110, for example, a set phase of an output RF signal.

[0018] With such a configuration, the arithmetic processing unit 130 generates a voltage corresponding to the voltage difference between the phase difference voltage V_Δphase and the reference voltage V_Phase ref. Specifically, as shown in the following formula, the arithmetic processing unit 130 performs integration processing on the differential voltage between the phase difference voltage V_Δphase and the reference voltage V_Phase ref. V_control=∫(V_Δphase-V_Phase ref)dt The arithmetic processing unit 130 feeds this voltage back to the phase shifter 110 as the control voltage V_control.

[0019] As described above, according to the RF phase shifter 100 of the first embodiment, the output phase and the input phase of the phase shifter 110 are compared by the high-precision phase comparator 120, the difference between the phase difference and the set phase difference (V_Phase ref) is integrated and fed back to the phase shifter 110, and the output phase is adjusted to the set phase. This enables high-precision phase control. Furthermore, the output phase of the output RF signal can be stabilized for a long time.

[0020] In particular, since the arithmetic processing unit 130 performs integration processing, high-precision phase control is possible even when the frequency of the phase-shift target signal increases, and the output phase of the output RF signal can be stabilized for a long period of time.

[0021] [Second Embodiment] (RF phase shifter) Figure 1 is a conceptual diagram showing an RF phase shifter according to this embodiment, and Figure 3 is a circuit diagram showing an RF phase shifter according to the second embodiment. The RF phase shifter 100A shown in Figures 1 and 3 differs from the RF phase shifter 100 of the first embodiment shown in Figures 1 and 2 in that it includes a digital phase shifter 110A and a digital arithmetic processing unit 130A instead of an analog phase shifter 110 and an analog arithmetic processing unit 130.

[0022] The phase shifter 110A is a digital phase shifter. The phase shifter 110A receives an input RF signal, generates an output RF signal by changing the phase of the input RF signal to a set phase according to a digital control signal, and outputs the output RF signal.

[0023] The arithmetic processing unit 130A is a digital arithmetic processing unit and is composed of arithmetic processors such as a PU (Processing Unit), DSP (Digital Signal Processor), and FPGA (Field-Programmable Gate Array). The functions of the arithmetic processing unit 130A are realized by executing predetermined software (programs) stored in memory. The functions of the arithmetic processing unit 130A may be realized through the cooperation of hardware and software, or they may be realized by hardware (electronic circuits) alone.

[0024] The input of the arithmetic processing unit 130A is connected to the output of the phase comparator 120, and another input of the arithmetic processing unit 130A is connected to the reference voltage line V_Phase ref. The output of the arithmetic processing unit 130A is connected to the phase shifter 110A.

[0025] The arithmetic processing unit 130A receives a phase difference voltage V_Δphase as its input. The other input to the arithmetic processing unit 130A receives a reference voltage V_Phase ref. The reference voltage V_Phase ref is a voltage corresponding to the set phase of the phase shifter 110A, for example, the set phase of the output RF signal.

[0026] The arithmetic processing unit 130A generates a signal corresponding to the voltage difference between the phase difference voltage V_Δphase and the reference voltage V_Phase ref. Specifically, the arithmetic processing unit 130A performs integration processing on the difference voltage between the phase difference voltage V_Δphase and the reference voltage V_Phase ref, as shown in the following equation. V_control=∫(V_Δphase-V_Phase ref)dt The arithmetic processing unit 130A converts this voltage into a bit code and feeds the converted signal back to the phase shifter 110A as a digital control signal V_control(bit code).

[0027] As explained above, in the RF phase shifter 100A of the second embodiment, the output phase and input phase of the phase shifter 110A are compared by the high-precision phase comparator 120, and the difference between that phase difference and the set phase difference (V_Phase ref) is fed back to the phase shifter 110A to adjust the output phase to the set phase. This enables high-precision phase control. Furthermore, the output phase of the output RF signal can be stabilized for a long period of time.

[0028] In particular, since the arithmetic processing unit 130A performs integration processing, high-precision phase control is possible even when the frequency of the phase-shifted signal increases, and the output phase of the output RF signal can be stabilized for a long period of time.

[0029] (Digital phase shifter) Below, we will describe an example of the digital phase shifter 110A shown in Figure 3. Figure 4 is a circuit diagram showing an example of a phase shifter according to this embodiment, and Figure 5 is a circuit diagram showing another example of a phase shifter according to this embodiment. The phase shifter 10 shown in Figures 4 and 5 can be used as the digital phase shifter 110A shown in Figure 3.

[0030] The phase shifter 10 shown in Figure 4 is a hybrid-coupled high-frequency (RF) phase shifter composed of quarter-wavelength lines 11 and 12 with characteristic impedance Z0 and quarter-wavelength lines 13 and 14 with characteristic impedance Z0 / √2. The phase shifter 10 has one end of line 11 as the input terminal RF_IN and the other end of line 11 as the output terminal RF_OUT. The phase shifter 10 is equipped with variable reactance elements 1(1A, 1B) that terminate the output terminal 13_OUT on the line 13 side and the output terminal 14_OUT on the line 14 side, respectively. Details of the variable reactance elements 1(1A, 1B) will be described later.

[0031] In the phase shifter 10, the RF signal input from the input terminal RF_IN is distributed through hybrid-coupled transmission 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. Since these output terminals 13_OUT and 14_OUT are terminated by variable reactance elements 1 (1A, 1B), the signals transmitted to these output terminals undergo a phase shift dependent on the reactance amount of the variable reactance elements 1 (1A, 1B) and are reflected. The signals reflected at these output terminals 13_OUT and 14_OUT are combined again in the hybrid-coupled transmission lines 11, 12, 13, and 14 and output from the output terminal RF_OUT. In this state, the output signal undergoes a phase shift dependent on the reactance amount of the variable reactance element 1 (1A, 1B), and by changing the reactance amount of the variable reactance element, it operates as a phase shifter.

[0032] In Figure 4, an example is shown in which the variable reactance elements 1(1A,1B) are applied to a hybrid-coupled phase shifter 10. However, as shown in Figure 5, the variable reactance elements 1(1A,1B) may also be applied to a loaded-line type phase shifter 10 composed of a quarter-wavelength transmission line 11 with a characteristic impedance of Z0.

[0033] Thus, by using a high-frequency phase shifter that employs a digital variable reactance element, as described later, the reactance can be broadly varied in both capacitive and inductive ways, making it possible to realize a low-loss, high-frequency (RF) phase shifter with a large phase shift range.

[0034] (Digital variable reactance element) Below, we will describe an example of a variable reactance element shown in Figures 4 and 5. Figure 6 is a circuit diagram showing a digital variable reactance element according to this embodiment. As shown in Figure 6, the digital variable reactance element 1 is an element that digitally varies its reactance. The digital variable reactance element 1 comprises a plurality of digital capacitors 2 and a plurality of digital inductors 4. 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.

[0035] The digital capacitor 2 has a capacitor C1 connected in series with a digital switch (first digital switch) Q. The digital switch Q is not particularly limited, but a switching element such as an FET (Field Effect Transistor) can be used. The digital switch Q can be switched between two states: on and off. As a result, the digital capacitor 2 can switch between two values: a first value which is the capacitance of capacitor C1 (digital switch Q is on), and a second value which is a capacitance of 0 (digital switch Q is off). In other words, the digital capacitor 2 can switch its capacitance digitally.

[0036] The digital inductor 4 has an inductor L1 and a digital switch (second 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 between two states: on and off. As a result, the digital inductor 4 can switch between two values: a first value which is the inductance of inductor L1 (digital switch Q is on), and a second value which is an inductance of 0 (digital switch Q is off). In other words, the digital inductor 4 can switch its inductance digitally.

[0037] The digital resistor 6 has a resistor R1 connected in series with a digital switch Q. 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 between two states: on and off. As a result, the digital resistor 6 can switch between two values: a first value which is the resistance value of resistor R1 (digital switch Q is on), and a second value which is a resistance value of 0 (digital switch Q is off). In other words, the digital resistor 6 can switch its resistance value digitally.

[0038] As a result, the variable reactance element 1 can have its reactance digitally varied by switching the on or off state of each digital switch Q. Furthermore, the variable reactance element 1 can digitally vary its impedance, particularly the impedance to RF signals (high-frequency signals), by switching the on or off state of each digital switch Q.

[0039] This digital variable reactance element 1 allows the reactance of multiple capacitors C1 and multiple inductors L1 to be digitally varied by control of a digital switch Q. Furthermore, the digital variable reactance element 1 allows the impedance of multiple capacitors C1, multiple inductors L1, and resistors R1 to be digitally varied by control of a digital switch Q.

[0040] Furthermore, not only is the capacitance variable, but the inductance is also variable, allowing the reactance to be varied over a wide range, from capacitive (1 / 2πfc) to inductive (2πfL). Therefore, the variable range of reactance (1 / 2πfc + 2πfL) can be widened.

[0041] Furthermore, it does not require the use of multiple variable capacitors or multiple variable inductors, and the control signals for multiple variable capacitors or multiple variable inductors do not become complex.

[0042] Furthermore, it becomes possible to realize a low-loss, high-frequency (RF) phase shifter with a large phase shift range.

[0043] In the embodiment described above, a variable reactance element 1 was illustrated in which each digital capacitor 2 has a capacitor C1 connected in series and a digital switch Q, each digital inductor 4 has an inductor connected in series or in parallel and a digital switch, and a plurality of digital capacitors 2 and a plurality of digital inductors 4 are connected in parallel. However, the present invention is not limited thereto and is applicable to various variable reactance elements in which each digital capacitor has a capacitor connected in series or in parallel and a digital switch, each digital inductor has an inductor connected in series or in parallel and a digital switch, and a plurality of digital capacitors and a plurality of digital inductors are connected in series or in parallel. For example, modified examples 1 and 2 of this embodiment are illustrated below.

[0044] (Digital variable reactance element of modified example 1) Figure 7 is a circuit diagram showing a digital variable reactance element according to Modification 1 of this embodiment. As shown in Figure 7, the digital variable reactance element 1A is an element that digitally varies its reactance. The digital variable reactance element 1A comprises a plurality of digital capacitors 2A and a plurality of digital inductors 4A. The digital variable reactance element 1A may also include a digital resistor 6A. In the digital variable reactance element 1A, the plurality of digital capacitors 2A, the plurality of digital inductors 4A, and the digital resistor 6A are connected in series.

[0045] The digital capacitor 2A has a capacitor C1 connected in series with a digital switch (first digital switch) Q, and a capacitor C2 connected in parallel with the same digital switch Q. Specifically, in the digital capacitor 2A, the series circuit of capacitor C1 and digital switch Q and capacitor C2 are connected in parallel. 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 which is the combined capacitance of capacitors C1 and C2 (digital switch Q is on), and a second value which is the capacitance of capacitor C2 (digital switch Q is off). In other words, the digital capacitor 2A can switch its capacitance digitally.

[0046] The digital inductor 4A has an inductor L1 and a digital switch (second digital switch) Q connected in series, and an inductor L2 and the same digital switch Q connected in parallel. Specifically, in the digital inductor 4A, the series circuit of inductor L1 and digital switch Q and inductor L2 are connected in parallel. The digital switch Q is the same as described above. As a result, the digital inductor 4A can switch between two values: a first value which is the combined inductance of inductors L1 and L2 (digital switch Q is ON), and a second value which is the inductance of inductor L2 (digital switch Q is OFF). In other words, the digital inductor 4A can switch its inductance digitally.

[0047] The digital resistor 6A has a resistor R1 and a digital switch Q connected in parallel. The digital switch Q is the same as described above. As a result, the digital resistor 6A can switch between two values: a first value with a resistance of 0 (digital switch Q is on), and a second value with the resistance of resistor R1 (digital switch Q is off). In other words, the digital resistor 6A can switch its resistance value digitally.

[0048] As a result, the variable reactance element 1A can have its reactance digitally varied by switching the on or off state of each digital switch Q. Furthermore, the variable reactance element 1A can digitally vary its impedance, particularly the impedance to RF signals (high-frequency signals), by switching the on or off state of each digital switch Q.

[0049] The digital variable reactance element 1A of this modified example 1 also has the same advantages as the digital variable reactance element 1 of this embodiment described above.

[0050] (Digital variable reactance element of modified example 2) Figure 8 is a circuit diagram showing a digital variable reactance element according to a modified example 2 of this embodiment. As shown in Figure 8, the digital variable reactance element 1B is an element that digitally varies its reactance. The digital variable reactance element 1B comprises a plurality of the above-described digital capacitors 2A and a plurality of the above-described 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.

[0051] As a result, the variable reactance element 1B can have its reactance digitally varied by switching the on or off state of each digital switch Q. Furthermore, the variable reactance element 1B allows for digital variation of the impedance, particularly the impedance to RF signals (high-frequency signals), by switching the on or off state of each digital switch Q.

[0052] This modified example 2, the digital variable reactance element 1B, also has the same advantages as the digital variable reactance element 1 of this embodiment described above.

[0053] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. Furthermore, the RF phase shifter of the above-described embodiment is applicable to technical fields such as phased arrays, radar, combiners, and communications. [Explanation of symbols]

[0054] 1,1A,1B Digital Variable Reactance Element 2.2A Digital Capacitor 4.4A Digital Inductor 6.6A Digital Resistor C1, C2 Capacitors L1, L2 Inductors R1 resistor Q Digital Switch 10,110,110A phase shifter 100,100A RF phase shifter 120 Phase comparator 130,130A Arithmetic Processing Unit 132 Op-amps 133,134 resistor 136 Capacitors 141,142 Turnout

Claims

1. A digital phase shifter that receives an input RF signal, generates an output RF signal by changing the phase of the input RF signal to a set phase according to a digital control signal, and outputs the output RF signal. A phase comparator that generates a phase difference voltage corresponding to the phase difference between the input RF signal and the output RF signal, A calculation processing unit that generates the digital control signal corresponding to the voltage difference between the phase difference voltage and the reference voltage corresponding to the set phase, Equipped with, The aforementioned digital phase shifter has a digital variable reactance element that digitally varies the reactance, The aforementioned digital variable reactance element comprises a plurality of digital capacitors, a plurality of digital inductors, and a digital resistor. The aforementioned plurality of digital capacitors, the plurality of digital inductors, and the digital resistor are connected in series or in parallel. Each of the aforementioned plurality of digital capacitors has a capacitor connected in series or parallel and a first digital switch, and the first digital switch is switchable between two states: on and off. Each of the aforementioned plurality of digital inductors has an inductor connected in series or in parallel and a second digital switch, and the second digital switch is switchable between two states: on and off. The digital resistor comprises resistors connected in series or parallel and a third digital switch, the third digital switch being switchable between two states: on and off. RF phase shifter.

2. The RF phase shifter according to claim 1, wherein the calculation processing unit performs integration processing of the difference voltage between the phase difference voltage and the reference voltage.

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