Isolator

Abstract

To provide an isolator that is compact, has wide-band operation, and has low power consumption.SOLUTION: In an isolator, a frequency mixer 11 and a frequency mixer 12 are connected in series, a local oscillator 3 is connected to the mixers 11 and 12, and in addition, it is possible to input local signals of the same frequency to the mixers 11 and 12, the frequency of the signal input to the mixer 11 is up-converted by the local signal, and then input to the mixer 12 and down-converted, and a phase delay device 22 can delay the phase of the up-conversion signal of the mixer 11, and a phase shifter 21 converts the phase of the local signal to create a phase difference between the local signals between the mixer 11 and the mixer 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an isolator.

Background Art

[0002] An isolator is a non - reversible circuit element that transmits a traveling wave such as an input signal with low loss and attenuates a backward wave such as a reflected wave. For example, in the field of radio astronomy, isolators are used in devices for detecting weak radio waves (such as microwaves) from the universe. Examples of isolators include those disclosed in the following prior art documents.

Prior Art Documents

Non - Patent Documents

[0003]

Non - Patent Document 1

Non - Patent Document 2

Non - Patent Document 3

Non - Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the field of radio astronomy, improvement of observation efficiency by multi-beaming is aimed at. For isolators for microwaves, miniaturization due to the demand for large-scale integration and an isolation function in a wide band are required. Furthermore, in receivers in the field of radio astronomy, heat generation due to power consumption of a cryogenic low-noise amplifier or the like cannot be ignored. Therefore, for multi-beaming of a receiver using a superconducting element, low power consumption of circuit constituent elements is required. However, the isolator disclosed in Non-Patent Document 1 has a size on the order of several centimeters and is not suitable for large-scale integration. Each of the isolators disclosed in Non-Patent Document 2 and Non-Patent Document 3 has a narrow operating frequency band and a complicated circuit configuration and is not suitable for large-scale integration. The isolator of Non-Patent Document 4 is a unidirectional amplifier and functions as an isolator, but has a problem of high power consumption. These problems are common to fields using superconducting elements such as quantum computers.

[0005] Therefore, an object of the present invention is to provide an isolator that can be miniaturized, can operate in a wide band, and has low power consumption.

Means for Solving the Problems

[0006] To achieve the above object, the isolator of the present invention includes a first frequency mixer, a second frequency mixer, a local oscillator, a phase delay device, and a phase shifter, the first frequency mixer and the second frequency mixer are connected in series, the local oscillator is connected to the first frequency mixer and the second frequency mixer and can input a local signal of the same frequency to the first frequency mixer and the second frequency mixer, a signal to be isolated can be input to the first frequency mixer, the frequency of the signal input to the first frequency mixer is up-converted by the local signal, The frequency of the up-converted signal is input to the second frequency mixer and down-converted, and the down-converted signal is output from the second frequency mixer. The phase shifter can delay the phase of the signal whose frequency has been up-converted by the first frequency mixer. The phase shifter can convert the phase of the local signal to generate a phase difference of the local signal between the first frequency mixer and the second frequency mixer.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide an isolator that can be miniaturized, can operate in a wide band, and has low power consumption. If the isolator of the present invention is used, for example, in the field of radio astronomy, it can contribute to the realization of advanced multi-beaming (e.g., 1000 beams).

Brief Description of the Drawings

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] In the isolator of the present invention, the phase delay amount and the phase difference of the delayed signal are defined by the following relational expression (A) and the following relational expression (B), and the gain of the traveling wave traveling in the traveling direction of the signal is greater than the gain of the backward wave traveling in the direction opposite to the traveling direction. Thus, Φ in the relational expression (A) up 0 (degrees), and Φ in the relational expression (B) LO 0 (degrees) may be settable. Relational expression (A) Φ up (degrees)=Φ up 0 (degrees)+180 (degrees)×n Φ up (degrees): the phase delay amount n: integer Relational expression (B) Φ LO (degrees)=Φ LO 0 (degrees)+180 (degrees)×m Φ LO (degrees): the phase difference m: integer

[0010] In the above aspect, the combination of the Φ up 0 and the Φ LO 0 can be appropriately set depending on, for example, the connection location of the phase shifter (for example, whether it is connected to the first frequency mixer or the second frequency mixer). For example, when the phase shifter is connected to the second frequency mixer and a phase difference is generated in the local signal input to the second frequency mixer with respect to the local signal input to the first frequency mixer as a reference, the Φ up 0 = 45 degrees and the Φ LOWhen Φ is 45 degrees, the gain of the forward wave is maximized and the gain of the backward wave is minimized, and the isolation function is maximized. Conversely, when the phase shifter is connected to the first frequency mixer and generates a phase difference in the local signal input to the first frequency mixer with respect to the local signal input to the second frequency mixer, Φ up 0=45 degrees and the above Φ LO When Φ = 135 degrees, the gain of the forward wave is maximum and the gain of the backward wave is minimum, and the isolation function is maximum. up 0 and the above Φ LO By appropriately setting the combination of Φ 0, it is also possible to reverse the direction of isolation. LO In the case where Φ = 0 degrees and 90 degrees, the gain of the forward wave and the gain of the backward wave are the same, and no isolation occurs. LO The angle 0 may be set to a value other than 0 degrees and 90 degrees.

[0011] In the isolator of the present invention, the first frequency mixer and the second frequency mixer may be SIS quasi-particle mixers using a superconductor-insulator-superconductor (SIS) junction. The SIS quasi-particle mixer operates as a double sideband (DSB) mixer for a local oscillation frequency signal equal to or higher than a gap frequency that is a frequency conversion (eΔVg / h; e is an elementary charge, h is a Planck constant) of a gap voltage width (ΔVg) at a temperature below which the SIS operates as a superconducting element. The SIS quasi-particle mixer can be formed on a substrate, which allows the isolator to be miniaturized. Alternatively, the frequency mixer used in the isolator of the present invention may be, for example, a general microwave frequency mixer that does not use a superconducting element. Examples of mixers other than the SIS quasi-particle mixer include a Josephson mixer and a HEB (hot electron bolometer) mixer. In addition, in the present invention, the SIS quasi-particle mixer may be used from the viewpoint of conversion gain and the like.

[0012] In the above aspect, the isolator of the present invention further includes an applying means, and the applying means can apply a bias voltage to the first frequency mixer (first quasiparticle mixer) and the second frequency mixer (second quasiparticle mixer), and the bias voltage is a bias voltage more suitable for the first frequency mixer than for the second frequency mixer. This may be the case. In this aspect, the same bias voltage may be applied to each of the first quasiparticle mixer and the second quasiparticle mixer, or different bias voltages may be applied. The "bias voltage more suitable for the first frequency mixer than for the second frequency mixer" means, for example, that the gain (Gmix1up) of the forward wave up-converted in the first frequency mixer is greater than the gain (Gmix1down) of the backward wave down-converted (Gmix1up>Gmix1down), and the gain (Gmix2down) of the backward wave down-converted in the second frequency mixer is greater than the gain (Gmix2up) of the forward wave up-converted (Gmix2down>Gmix2up).

[0013] In the aspect including the applying means, the phase retarder and the phase shifter may be optional components. That is, in the aspect including the applying means, the isolator functions even without the phase retarder and the phase shifter. Therefore, in the aspect including the applying means, the phase retarder and the phase shifter may or may not be included in the isolator of the present invention, or either one of them may be included.

[0014] The isolator of the present invention may be such that the first frequency mixer and the second frequency mixer are mounted (or formed) on the same substrate. In this aspect, large-scale integration is possible. In this aspect, in addition to the two frequency mixers, at least one element of the local oscillator, the phase retarder, and the phase shifter may be mounted (or formed) on the same substrate, and the other elements may also be mounted (or formed) on the same substrate.

[0015] In the isolator of the present invention, when a rectangular waveguide having frequency selectivity in the transmission line itself is used as the signal transmission line, the transmission signal can be filtered using the cutoff frequency characteristics of the rectangular waveguide. Further, when a strip line or the like that cannot utilize frequency selectivity is used as the signal transmission line, a filter that selects a predetermined frequency component can be provided for each of the first frequency mixer (upconverter) and the second frequency mixer (downconverter).

[0016] In the isolator of the present invention, the local signal may be input from one of the local transmitters to the first frequency mixer and the second frequency mixer, or the local signal may be input from two or more local transmitters to the first frequency mixer and the second frequency mixer. The local transmitter is not particularly limited, and for example, a Josephson transmitter can be used. The Josephson transmitter operates in the THz band in an extremely low temperature environment and can easily achieve a high degree of integration. In the manufacturing process of the Josephson transmitter, the superconducting film for the SIS quasiparticle mixer and the superconducting film for the Josephson transmitter can be formed of a common film, and as a result, it is possible to form the SIS quasiparticle mixer and the local transmitter on the same substrate. In the present invention, in addition to the Josephson transmitter, there is an FFO transmitter (Flux Flow Oscillator) which is a superconducting element. Further, in the present invention, as the phase shifter and the phase delay device, a device having a phase control circuit can be used. For example, as the phase control circuit, there are a transmission line having phase delay characteristics, a delay element using a distributed multiplier circuit, and a lumped multiplier element such as an inductor. Since the phase shifter only needs to be able to generate a phase difference in the local signals of both the first frequency mixer and the second frequency mixer, if the transmission line, the delay element, or the lumped multiplier element or the like is connected to at least one of the first frequency mixer and the second frequency mixer, it functions as the phase shifter.

[0017] In the isolator of the present invention, the signal may be a microwave, and in this case, the isolator of the present invention is for microwave applications.

[0018] The isolator of the present invention may function as a unidirectional amplifier.

[0019] The superconducting electronic device of the present invention includes the isolator of the present invention. In this aspect, the superconducting electronic device may constitute, for example, part or all of a radio telescope or a quantum computer.

Example

[0020] Based on FIGS. 1 and 2, the operating principle of the isolator of the present invention will be described.

[0021] First, FIG. 1 shows a circuit diagram of the isolator of this embodiment. As shown in FIG. 1, the isolator of this embodiment is composed of two frequency mixers (Mixer1, Mixer2) 11 and 12, two phase control circuits (phase shifter Φ1, phase shifter Φ2) 21 and 22, one divider (Divider) 4, and one local oscillator (LO) 3. The phase control circuit functions as a phase shifter (Φ1) 22 and a phase shifter (Φ2) 21. In FIG. 1, "I", "R", and "L" respectively indicate the intermediate frequency (IF) port, radio frequency (RF) port, and local oscillator (LO) port in the frequency mixers 11 and 12. In the isolator shown in FIG. 1, the frequency fs of the input signal from port 1 (port1) is up-converted to fup = fLO ± fs by the frequency fLO of the local signal input from the local oscillator (LO) 3 in the first frequency mixer (Mixer1) 11, and then down-converted to fs in the second frequency mixer (Mixer2) 12 and output to port 2 (Port2).

[0022] Between two frequency mixers (Mixer1, Mixer2) 11 and 12, they are connected via a phase shifter (Φ1) 22 that delays the phase of the up-converted frequency. A divider (Divider) 4 is connected to the local oscillator (LO) 3. The divider (Divider) 4 is connected to each of the frequency mixers (Mixer1) 11 and the frequency mixer (Mixer2) 12 by two transmission lines. Among the two transmission lines, a phase shifter (Φ2) 21 is arranged on the side of the frequency mixer (Mixer 2) 12. The local signal generated by the local oscillator (LO) 3 is distributed by the divider (Divider) 4, and by the phase shifter (Φ2) 21, when the frequency mixer (Mixer1) 11 is an ideal transmission line and the phase delay is assumed to be 0, with respect to the phase difference Φ2 based on the side of the frequency mixer (Mixer2) 12, it is input to each of the frequency mixers (Mixer1, Mixer2) 11 and 12. Also, between the frequency mixer (Mixer1) 11 and the frequency mixer (Mixer2) 12, a phase difference occurs in the up-converted signal by the phase shifter (Φ1) 22. Note that the present invention is not limited to the configuration of FIG. 1. For example, the phase shifter (Φ2) 21 may be arranged on the side of the first frequency mixer (Mixer1) 11. By adjusting the combination of the phase delay amount Φ2 and the phase difference Φ1, it functions as an isolator.

[0023] In the isolator of FIG. 1, in the traveling wave where an input signal is input from port 1 and an output signal is output from port 2, the frequency of the input signal and the frequency of the output signal are the same. Also, in the isolator of FIG. 1, isolation of the input signal occurs by setting the conditions of the phase difference and the phase delay. In the isolator of the present invention, since a band limiting device is not used, for example, it can operate in a wide band from near direct current to the local oscillation (LO) frequency. In the two frequency mixers of the isolator of the present invention, the mixer that first inputs a signal from the outside is defined as the first frequency mixer, and the mixer that outputs to the outside is defined as the second frequency mixer. Therefore, in the isolator shown in the circuit diagram of FIG. 1, when a signal is input to the frequency mixer (Mixer1) 11 from port 1, the frequency mixer (Mixer1) 11 becomes the first frequency mixer, and the frequency mixer (Mixer2) 12 becomes the second frequency mixer. Conversely, when a signal is input from port 2, the frequency mixer (Mixer2) 12 becomes the first frequency mixer, and the frequency mixer (Mixer1) 11 becomes the second frequency mixer.

[0024] Next, the operating principle of the isolator in FIG. 1 is shown.

[0025] First, the input signal voltage applied to port 1 of the frequency mixer (Mixer1) 11 is represented by Equation 1 below.

[0026]

Equation

[0027] In Equation 1, let V0 = 1. Also, the local oscillation voltages (V LO1 , V LO2 ) applied to the frequency mixers (Mixer1, Mixer2) 11 and 12 can be expressed as shown in Equation 2 below using the phase difference Φ2.

[0028]

Equation

[0029] And, V in Equation 1 in is up-converted by the frequency mixer (Mixer1) 11 in (β) of FIG. 1 and becomes as follows in Equation 3 below. In the right side of the equation of Equation 3 below, the first half condition indicates the signal of the upper side band (USB), and the second half condition indicates the signal of the lower side band (LSB).

[0030]

Equation

[0031] In Equation 3 above, the signal indicated by V up is the up-converted frequency and is delayed by the phase Φ1. And, in FIG. 1(γ), the signal V of Equation 4 below up is obtained.

Equation

[0032] Then, in FIG. 1(δ), the signal V of Equation 4 above up is down-converted by the frequency mixer (Mixer2) 12 as shown in Equation 5 below to the output voltage V 21 and its frequency becomes the same as the input frequency.

Equation

[0033] On the other hand, the output voltage V of the signal (reflected wave) flowing from port 2 to port 1 12 can be derived as shown in Equation 6 below.

Equation

[0034] The mathematical expressions shown in each of the numbers 5 and 6 represent that two output voltages derived from the upper sideband (USB) signal and the lower sideband (LSB) signal are synthesized under different phase conditions, and non-reciprocity or isolation will occur due to the phase relationship set by the phase shifter (Φ1) 22 and the phase shifter (Φ2) 21.

[0035] Next, based on the mathematical expressions shown in each of the numbers 5 and 6, FIG. 2(a) shows the vector diagrams of the sidebands at the positions (α), (β), (γ), and (δ) in FIG. 1. As shown in FIG. 2(a), in the forward wave S21 from port 1 to port 2, the two sidebands are synthesized in the same phase, while in the backward wave S12 from port 2 to port 1, the sidebands are canceled out in the opposite phase. Also, FIG. 2(b) shows the changes in the gains (dB) of the forward wave S21 (dotted line) and the backward wave S12 (solid line) when the phase delay amount (Φ1) is 0, π / 4, π / 2, and 3π / 4 and the phase difference changes from 0 to 360 degrees. As shown in FIG. 2(b), when the phase delay amount (Φ1) is 0 and π / 2, the changes in the gains of the forward wave S21 and the backward wave S12 are the same. However, when the phase delay amount (Φ1) is π / 4 and 3π / 4 respectively, when the phase difference (Φ2) is π / 4 + nπ / 2 (n is an integer of 0 or more), the changes in the gains are in the opposite directions to each other, and it can be seen that the function becomes optimal as an isolator in these cases. For example, when the phase delay amount (Φ1) is 45 degrees (π / 4) and the phase difference (Φ2) is 45 degrees (π / 4), or when the phase delay amount (Φ1) is 135 degrees (3π / 4) and the phase difference (Φ2) is 135 degrees (3π / 4), the gain of the forward wave S21 flowing from port 1 to port 2 becomes maximum, and the gain of the backward wave S12 flowing from port 2 to port 1 becomes minimum. In these cases, the function as an isolator in the direction from port 1 to port 2 becomes the highest. In the isolator of FIG. 1, the direction of the forward wave changes depending on different phase combinations, for example, when Φ1 is 45 degrees and Φ2 is 135 degrees. When the phase delay amount (Φ1) is π / 2 and the phase difference (Φ2) is (n + 1)π / 2 (n: integer), the device shown in the circuit diagram of FIG. 1 functions as a gyrator.

Example

[0036] Next, an example (Example 2) of constructing the isolator of the present invention using commercially available components and devices is shown.

[0037] As the two frequency mixers, frequency mixers with product number ZX05-C42-S+ manufactured by Mini-circuits were used. These frequency mixers cover an RF and LO frequency band of 1.0 to 4.2 GHz and an IF frequency band of DC (near direct current) to 1.5 GHz. Also, as the phase shifter with adjustable phase, a phase shifter with product number PE8244 manufactured by Pasternack was used. By using this phase shifter, a phase delay was generated between each frequency mixer, and a phase difference was generated in the local signal input to each frequency mixer. In addition, a local signal transmitter (product number N5183A manufactured by Agilent), a distributor (product number ZX10-2-42-S+ manufactured by Minicircuit), and two attenuators (product number 18AH-05, 5 dB manufactured by API / Inmet) were used.

[0038] Fig. 3 shows the isolator configured by assembling these components. As shown in Fig. 3, in the isolator of this embodiment, a distributor Divider4 is connected to the local signal transmitter LO3 by a line. The line extending from one side of the distributor 4 is directly connected to one of the frequency mixers (Mixer 1) 11, and the line extending from the other side of the distributor 4 is connected to the phase shifter (TPS Tunable phase shifter) 2, and this phase shifter 2 is connected to the other frequency mixer (Mixer2) 12 by a line. The two frequency mixers 11 and 12 are connected via an attenuation circuit 5. The attenuation circuit 5 is configured by connecting two attenuators (5 dB att) with a connector. The attenuation circuit 5 is for preventing a decrease in the isolation function due to a large reflection coefficient of the frequency mixer.

[0039] Next, the phase delay amount was changed to examine the gains of the forward wave S21 and the backward wave S12. For the measurement of the forward wave S21 and the backward wave S12, a vector network analyzer (VNA, product number E8361C manufactured by Agilent) was used. Also, the measurement was carried out by measuring the intensities (gain dB) of the forward wave S21 and the backward wave 12 in the range of the input / output signal frequency of 0.25 GHz and the local oscillation frequency (LO frequency) of 2.15 to 2.40 GHz. The results are shown in Fig. 4. The numbers (2.15 to 2.40) in the graph of Fig. 4 indicate the LO frequency (GHz). At the LO frequencies of 2.15, 2.30, and 2.40 GHz, the measurement results similar to the calculation in Fig. 2 were shown. Also, the measurement results at the LO frequency of 2.30 GHz clearly showed the function as an isolator. The maximum isolator function occurred at 41.6×π / 180.

[0040] The frequency characteristics of the isolator of this embodiment are shown in Fig. 5. In Fig. 5, S21meas indicates the gain (dB) of the forward wave, S12meas indicates the gain (dB) of the backward wave, and Isolation indicates the gain (dB) of the isolation. In Fig. 5, the top line representing the difference between the forward wave S21meas and the backward wave S12meas represents the isolation, and it can be seen that the minimum part of the isolation is 17 dB. From these facts, as shown in Fig. 5, it was shown that an isolation effect of about 17 dB or more can be obtained over the signal frequency range of 0.01 to 1.50 GHz.

Example

[0041] Fig. 6 shows the circuit diagram of the isolator (Example 3) using an SIS quasiparticle mixer. As shown in Fig. 6, an SIS quasiparticle mixer 11 (SIS Mixer1 Up - conv.) and an SIS quasiparticle mixer 12 (SIS Mixer2 Down - conv.) are connected in series, and a phase - shift delay circuit 22 (Φup) is arranged between the two SIS quasiparticle mixers 11 and 12. The SIS quasiparticle mixers 11 and 12 are W - band (75 - 110 GHz) SIS quasiparticle mixers. Also, from the local oscillator 3, a local signal fLO is input to the SIS quasiparticle mixer 11 via a phase shifter 21, and the local signal fLO is directly input to the SIS quasiparticle mixer 12. In the circuit shown in Fig. 6, the frequency of the signal fs to be isolated is up - converted by the SIS quasiparticle mixer 11 to fup = fLO ± fs, and then down - converted by the SIS quasiparticle mixer 12 to the frequency fs.

[0042] Fig. 7 shows the configuration diagram of the isolator of this embodiment. As shown in Fig. 7, a 4K stage (cryogenic stage) 6 is formed on a cryostat (cryogenic device) 7. On the 4K stage 6, two SIS quasiparticle mixers (SIS Mixer1, SIS Mixer2) 11 and 12 are arranged. Note that 4K represents a cryogenic temperature (for example, a temperature near the boiling point of liquid helium). The SIS quasiparticle mixer 11 is connected to a coupler (Coupler1) 31, the coupler 31 is connected to an attenuator (Att 6dB) 25, the attenuator 25 is connected to a coupler (Coupler2) 32, and the coupler 32 is connected to the SIS quasiparticle mixer 12. Also, outside the 4K stage, a local oscillator (LO) 3 is arranged, and the local oscillator 3 is connected to the coupler 31 via a W - band variable attenuator 231 and a W - band variable phase shifter 24. Also, the local oscillator 3 is connected to the coupler 32 via a W - band variable attenuator 232. The two SIS quasiparticle mixers 11 and 12 are connected to a network analyzer (product number N5225B manufactured by Keysight) 8 arranged outside the 4K stage.

[0043] In the block diagram of FIG. 7, a Gunn transmitter was used for the local transmitter 3, and the frequency LO of the local signal was set to around 90 GHz. The couplers 31 and 32 arranged between the two SIS quasiparticle mixers 11 and 12 are W-band waveguide couplers. The attenuator 25 was inserted to reduce the impedance interference between the two SIS quasiparticle mixers 11 and 12. The variable phase shifter 24 can change the relative phase by about 200 degrees in the W-band.

[0044] In the isolator of this embodiment, by changing the local signal frequency LO with the variable phase shifter 24, the relative phase difference of the local signals input to the two SIS quasiparticle mixers 11 and 12 was changed. Also, in the isolator of this embodiment, by changing the local signal frequency LO, the frequency after upconversion was changed, and the phase Φup of upconversion was relatively changed. Note that the biases of the SIS quasiparticle mixers 11 and 12 were fixed at a voltage of 9.2 mV and a current of 50 μA. These results are shown in the graph of FIG. 8.

[0045] As shown in the graph of FIG. 8, minimum peak values (signal cancellation frequencies) were observed for each of the forward wave S21 and the backward wave S12 due to the change in the local signal frequency LO. Also, it was confirmed that the signal cancellation frequency changed due to the change in the local signal frequency LO. From these results, it was demonstrated that a large isolation effect can be obtained by controlling the phase of the local signal frequency LO and the phase of upconversion in the configuration using the two SIS quasiparticle mixers 11 and 12.

[0046] FIG. 9 shows a graph showing the relationship between voltage (Voltage mV) and current (Current μA) when the local signal frequency LO is 88 GHz in the isolator of this embodiment. As shown in FIG. 9, in the SIS quasiparticle mixer 11, upconversion is optimal at 9.3 mV (the point indicated by the arrow), and in the SIS quasiparticle mixer 12, downconversion is optimal at 10.5 mV (the point indicated by the arrow).

[0047] Fig. 10 shows the results of measuring the insertion losses of the forward wave S21 and the backward wave S12 at signal frequencies from 10 MHz to 10 GHz. As shown in Fig. 10, an isolation effect with an input / output gain of 20 dB or more was confirmed. Also, a positive gain exceeding 0 dB was observed at some signal frequencies (without correction of the attenuator 25).

[0048] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above embodiments. The configuration and conditions of the present invention can be variously changed within the scope of the present invention that can be understood by those skilled in the art.

Industrial Applicability

[0049] According to the present invention, for example, it is possible to provide a microwave isolator that can be integrated by miniaturization, operates over a wide band, and has low power consumption. The isolator of the present invention is useful in various fields where it is necessary to isolate weak electrical signals, such as in the field of radio astronomy and the field of quantum computers.

Explanation of Reference Numerals

[0050] 11 First frequency mixer 12 Second frequency mixer 2 Phase control circuit 21 Phase shifter 22 Phase delay device 24 W-band variable phase shifter 25 Attenuator 231, 231 W-band variable attenuator 3 Local oscillator 31, 32 Coupler 4 Divider 5 Attenuation circuit 6 4K stage 7 Cryostat 8 Network analyzer

Claims

1. comprising a first frequency mixer, a second frequency mixer, a local oscillator, a phase delay device, and a phase shifter, wherein the first frequency mixer and the second frequency mixer are connected in series, the local oscillator is connected to the first frequency mixer and the second frequency mixer, and can input a local signal of the same frequency to the first frequency mixer and the second frequency mixer, a signal to be isolated can be input to the first frequency mixer, the frequency of the signal input to the first frequency mixer is up-converted by the local signal, the frequency of the up-converted signal is input to the second frequency mixer and down-converted, and the signal of the down-converted frequency is output from the second frequency mixer, the phase delay device can delay the phase of the signal whose frequency has been up-converted by the first frequency mixer, the phase shifter can convert the phase of the local signal to generate a phase difference of the local signal between the first frequency mixer and the second frequency mixer, the phase difference is other than 0 degrees and 90 degrees, an isolator.

2. The phase delay amount of the delayed signal is 45 degrees, the phase difference is 45 degrees or 135 degrees, an isolator according to Claim 1.

3. the phase delay amount and the phase difference are defined by the following relational expression (A) and the following relational expression (B), and the gain of the traveling wave traveling in the traveling direction of the signal is greater than the gain of the backward wave traveling in the direction opposite to the traveling direction, so that Φ in the relational expression (A) ｕｐ 0 (degrees), and Φ in the relational expression (B) ＬＯ 0 (degrees) can be set, an isolator according to Claim 1 or 2. Relational expression (A) Φ ｕｐ (degrees) = Φ ｕｐ 0 (degrees) + 180 (degrees) × n Φ ｕｐ (degrees): the phase delay amount n: integer Relational expression (B) Φ ＬＯ (degrees) = Φ ＬＯ 0 (degrees) + 180 (degrees) × m Φ ＬＯ (degrees): the phase difference m: integer

4. A first frequency mixer, a second frequency mixer, a local oscillator, a phase delay device, and a phase shifter, The first frequency mixer and the second frequency mixer are connected in series, The local oscillator is connected to the first frequency mixer and the second frequency mixer, and can input a local signal of the same frequency to the first frequency mixer and the second frequency mixer, A signal to be isolated can be input to the first frequency mixer, The frequency of the signal input to the first frequency mixer is up-converted by the local signal, The frequency of the up-converted signal is input to the second frequency mixer and down-converted, and the signal of the down-converted frequency is output from the second frequency mixer, The phase delay device can delay the phase of the signal whose frequency is up-converted by the first frequency mixer, The phase shifter can convert the phase of the local signal to generate a phase difference of the local signal between the first frequency mixer and the second frequency mixer, The first frequency mixer and the second frequency mixer are an isolator that is a superconductor-insulator-superconductor (SIS) junction-based SIS quasiparticle mixer.

5. Further includes an applying means, The applying means can apply a bias voltage to the first frequency mixer and the second frequency mixer, The bias voltage applied to the first frequency mixer is a bias voltage more suitable for the first frequency mixer than the bias voltage applied to the second frequency mixer. The isolator according to claim 4.

6. The first frequency mixer and the second frequency mixer are mounted on the same substrate. The isolator according to claim 4.

7. The isolator according to claim 4, wherein the signal is a microwave and is for microwave applications.

8. The isolator according to claim 4, which can function as a unidirectional amplifier.

9. A superconducting electronics device including the isolator according to claim 4.

10. The superconducting electronics device according to claim 9, which constitutes part or all of a radio telescope or a quantum computer.

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