MATCHING CIRCUIT FOR LOW NOISE AMPLIFIER AND LOW NOISE AMPLIFIER COMPRISING SUCH A CIRCUIT

Abstract

An impedance matching circuit be connected to a non-linear impedance including a superconductor, includes a first terminal designated first connection port to be connected to a first connector of the non-linear impedance, a second terminal designated second connection port to be connected to a second connector of the non-linear impedance, a third terminal designated input/output terminal to receive the signal to amplify and a fourth terminal designated supply terminal to be connected to a polarisation source and configured so that a voltage V is applied between the first connection port and the second connection port. The circuit further includes a plurality of passive electrical components.

Claims

1. An impedance matching circuit intended to be connected to a non-linear impedance comprising a superconductor, said circuit comprising: a first terminal designated first connection port configured to be connected to a first connector of the non-linear impedance; a second terminal designated second connection port configured to be connected to a second connector of the non-linear impedance; a third terminal designated input/output terminal configured to receive a signal to amplify with a gain in power G and a pass band BW; a fourth terminal designated supply terminal configured to be connected to a polarisation source and configured so that a voltage V is applied between the first connection port and the second connection port, and a plurality of passive electrical components configured such that the impedance Z(f) between the first connection port and the second connection port for a signal of frequency f has a real part Re(Z(f)) such that: Re(Z(f.sub.s))>0 with f.sub.s a first frequency designated frequency of the signal; Re(Z(f.sub.i))>0 with f.sub.i a second frequency designated idler frequency; $Re (Z (0)) < \frac{h}{4 .Math. .Math. e^{2}} .Math. \frac{f_{p}}{G .Math. BW}$ with f.sub.p a third frequency designated pump frequency; $Re (Z (f_{p} + f_{s})) < \frac{f_{p} + f_{s}}{f_{i}} .Math. Re (Z (f_{i}));$ the pump frequency being chosen such that nf.sub.p=f.sub.s+f.sub.i with n an integer belonging to [1, +] and the idler frequency being chosen such that $f_{i} > \frac{k_{B} .Math. T}{h}$ with T the temperature of the circuit, k.sub.B Boltzmann's constant and h Planck's constant.

2. The circuit according to claim 1, wherein $Re (Z (f_{p} + f_{s})) < \frac{Re (Z (f_{i}))}{10} .$

3. The circuit according to claim 1, wherein $Re (Z (0)) < \frac{h}{4 .Math. .Math. e^{2}} .Math. \frac{1}{10 .Math. .Math. G} .$

4. The circuit according to claim 1, wherein $Re (Z (f_{p})) < \frac{4 .Math. .Math. e^{2}}{h} .Math. BW .Math. \frac{f_{p}}{f_{s} .Math. f_{i}} .Math. Re (Z (f_{s})) .Math. Re (Z (f_{i})) .$

5. The circuit according to claim 1, wherein the input/output terminal is intended to be connected to an impedance of value Z.sub.0 and $Re (Z (f_{s})) < 2 .Math. \frac{{.Math. Z_{trans} (f_{s}) .Math.}^{2}}{Z_{0}}$ with Z.sub.trans(f.sub.s) the voltage at the level of the input/output terminal when a unit current of frequency f.sub.s is applied between the first connection port and the second connection port.

6. The circuit according to claim 1, wherein $Re (Z (f_{p} + f_{s})) < \frac{f_{p} + f_{i}}{f_{s}} .Math. Re (Z (f_{s})) .$

7. The circuit according to claim 1, wherein $f_{i} > 4 .Math. \frac{k_{B} .Math. T}{h} .$

8. The circuit according to claim 1, wherein n=1.

9. The circuit according to claim 1, wherein $\max .Math. {Re (Z (f_{s})), Re (Z (f_{i}))} < \frac{h}{4 .Math. .Math. e^{2}} .$

10. The circuit according to claim 1, wherein the plurality of passive electrical components comprises: a first waveguide segment of which a first end is connected to the supply terminal through an inductance and to the input/output terminal through a first capacitance and a second end is connected to the first connection port; a second waveguide segment of which a first end is connected to earth through a second capacitance and a second end is connected to the first connection port; a third waveguide segment of which a first end is connected to an infinite impedance and a second end is connected to the first connection port; and wherein the second connection port is connected to earth.

11. A reflection amplifier comprising an impedance matching circuit according to claim 1, a polarisation source connected to the supply terminal, a non-linear impedance comprising a superconductor, said non-linear impedance comprising a first connector and a second connector, the first connector of the impedance being connected to the first connection port of the matching circuit, the second connector of the impedance being connected to the second connection port of the matching circuit, wherein the voltage applied between the first connection terminal and the second connection terminal by means of the voltage source is chosen such that $f_{p} = \frac{2 .Math. .Math. eV}{h}$ with 2e the electric charge of a Cooper pair and h Planck's constant.

12. The amplifier according to claim 11, wherein the superconductor material of the non-linear impedance is chosen such that $f_{s} < \frac{2 .Math. .Math.}{h}$ with the superconductor gap of the superconductor.

13. The amplifier according to claim 11, wherein the non-linear impedance comprises a Josephson junction.

14. The amplifier according to claim 13, wherein the Josephson junction is of Superconductor/Insulator/Superconductor type.

15. The amplifier according to claim 11, wherein the non-linear superconducting impedance comprises a SQUID.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0069] The figures are presented for indicative purposes and in no way limit the invention.

[0070] FIG. 1 shows an amplifier with Josephson junction according to the prior art.

[0071] FIG. 2 shows a matching circuit according to a first embodiment of a first aspect of the invention.

[0072] FIG. 3 shows a graph presenting the real part of the impedance as a function of the frequency of a matching circuit according to a first embodiment of a first aspect of the invention.

[0073] FIG. 4 shows a graph presenting the real part of the impedance as a function of the frequency of a matching circuit according to a first alternative of a first embodiment of a first aspect of the invention.

[0074] FIG. 5 shows a graph presenting the real part of the impedance as a function of the frequency of a matching circuit according to a second alternative of a first embodiment of a first aspect of the invention.

[0075] FIG. 6 shows a matching circuit according to a second embodiment of a first aspect of the invention.

[0076] FIG. 7 shows a graph presenting the real part of the impedance as a function of the frequency of a matching circuit according to a second embodiment of a first aspect of the invention.

[0077] FIG. 8 shows a matching circuit according to a third embodiment of a first aspect of the invention.

[0078] FIG. 9 shows a graph presenting the real part of the impedance as a function of the frequency of a matching circuit according to a third embodiment of a first aspect of the invention.

[0079] FIG. 10 shows an amplifier with Josephson junction according to an embodiment of a second aspect of the invention.

DETAILED DESCRIPTION

[0080] Unless stated otherwise, a same element appearing in the different figures has a single reference. All the following embodiments have been conceived in the case where the input/output terminal ES is intended to be connected or is connected to an impedance line Z.sub.0 equal to 50.

[0081] A matching circuit intended to be connected to a non-linear impedance L comprising a superconductor according to a first embodiment of a first aspect of the invention is illustrated in FIG. 2. The matching circuit comprises a first terminal designated first connection port J1 intended to be connected to a first connector B1 of the non-linear impedance L, a second terminal designated second connection port J2 intended to be connected to a second connector B2 of the non-linear impedance L, a third terminal designated input/output terminal ES intended to receive the signal to amplify, the amplification taking place with a gain in power G and over a pass band BW, and a fourth terminal designated supply terminal TA intended to be connected to a polarisation source ST and configured so that a voltage V is applied between the first connection port J1 and the second connection port J2.

[0082] The matching circuit also comprises a plurality of passive electrical components (T.sub.1, T.sub.2, T.sub.3, C.sub.1, C.sub.2, L.sub.1) configured such that the impedance Z(f) between the first connection port J1 and the second connection port J2 for a signal of frequency f has a real part Re(Z(f)) such that: [0083] Re(Z(f.sub.s))>0 with f.sub.s a first frequency designated signal frequency; [0084] Re(Z(f.sub.i))>0 with f.sub.i a second frequency designated idler frequency;

[00029] $Re (Z (0)) < \frac{h}{4 .Math. .Math. e^{2}} .Math. \frac{f_{p}}{G .Math. BW}$

with f.sub.p a third frequency designated pump frequency;

[00030] $- Re (Z (f_{p} + f_{s})) < \frac{f_{p} + f_{s}}{f_{i}} .Math. Re (Z (f_{i})) .$

[0085] Moreover, the pump frequency is chosen such that nf.sub.p=f.sub.s+f.sub.i with n an integer belonging to [1, +] and the idler frequency is chosen such that

[00031] $f_{i} > \frac{k_{B} .Math. T}{h}$

with T the temperature of the circuit, k.sub.B Boltzmann's constant and h Planck's constant. As has been specified beforehand, the signal frequencies f.sub.p+f.sub.s and f.sub.pf.sub.s are here treated differently. This difference is explained by the fact that the inventors use a quantum interpretation that gives a very different sense to the bands f.sub.p+f.sub.s and f.sub.pf.sub.s: [0086] the band f.sub.pf.sub.s is due to a process where each Cooper pair that tunnels through the junction gives one photon at the frequency f.sub.s and one photon at the frequency f.sub.pf.sub.s which amplifies the signal at the frequency f.sub.s (stimulated emission effect) and gives rise to a noise with a half-photon hf.sub.s (spontaneous emission effect) added; [0087] the band f.sub.p+f.sub.s is due to a process where each Cooper pair is frequency shifted from the frequency f.sub.s to the frequency f.sub.p+f.sub.s by absorbing the energy of a Cooper pair that tunnels, which leads to the absorption of the signal at the frequency f.sub.s without adding noise.

[0088] If the two processes have the same intensity, the process associated with the frequency f.sub.p+f.sub.s results in the loss of half of the incident signal and only the other half may be amplified, which is equivalent to reducing the gain in power twofold. In addition, the noise is increased twofold to pass from a half-photon hf/2 to a photon hf. Thus, if the band f.sub.p+f.sub.s may be greatly reduced by minimising the impedance at the frequency f.sub.p+f.sub.s as the invention proposes, it is possible to tend towards the optimal noise.

[0089] In the embodiment illustrated in FIG. 2, a part of the passive electrical elements is realised using waveguide segments (or CPW for CoPlanar Waveguide). The latter may be made from a superconductor material in order to minimise losses by Joule effect and thus thermal noise at the level of the circuit. As a reminder, a CPW of impedance Z.sub.0 and of length l terminating by an impedance Z.sub.L has an impedance Z.sub.in measured at the input of the CPW given by

[00032] $Z_{in} = \frac{Z_{L} + j .Math. .Math. Z_{0} .Math. \tan (.Math. .Math. l)}{Z_{0} + j .Math. .Math. Z_{L} .Math. \tan (.Math. .Math. l)} .Math. Z_{0}$

where is the propagation constant. The impedance of the waveguide segments is thus easy to control through their dimensions which makes their use very beneficial. However, it is also possible to use passive electrical elements such as capacitances or inductances, for example when the dimensional requirements are not compatible with the use of waveguide segments.

[0090] More particularly, the matching circuit illustrated in FIG. 2 comprises a first waveguide segment T.sub.1 of which a first end is connected to the supply terminal TA through an inductance L.sub.1 and to the input/output terminal ES through a first capacitance C.sub.1 and a second end is connected to the first connection port J1. As will be seen hereafter, this first waveguide segment T.sub.1 makes it possible to transform the impedance so as to favour a wide frequency band or an optimal noise as a function of the envisaged applications.

[0091] The circuit also comprises a second waveguide segment T.sub.2 of which a first end is connected to earth through a second capacitance C.sub.2 and a second end is connected to the first connection port J1. The second capacitance is chosen so as to behave in short-circuit at the frequencies f.sub.i, f.sub.s and f.sub.p.

[0092] In addition, the circuit comprises a third waveguide segment T.sub.3 of which a first end is connected to an infinite impedance (that is to say an open circuit) and of which a second end is connected to the first connection port J1. Finally, the second connection port J2 is connected to earth.

[0093] In a first exemplary embodiment, f.sub.p=12 GHz and f.sub.s=f.sub.i=6 GHz are chosen. The first waveguide segment T.sub.1 has a length

[00033] $l = \frac{_{s}}{4},$

with .sub.s the wavelength associated with the frequency f.sub.s and an impedance Z.sub.1 equal to 50. The second waveguide segment T.sub.2 has a length

[00034] $l = \frac{_{p}}{2},$

with .sub.p the wavelength associated with the frequency f.sub.p and an impedance Z.sub.2 equal to 150. This CPW thus makes it possible to produce antiresonances of the impedance between the first connection port J1 and the second connection port J2 at the frequencies kf.sub.p with k[1, +] and has a frequency close to the zero frequency, but makes it possible to apply a DC voltage at the level of the connection port J1. In other words, the real part of the impedance Re(Z(f)) is zero at these frequencies. The third waveguide segment T.sub.3 has a length

[00035] $l = \frac{_{p + s}}{4},$

with .sub.p+s the wavelength associated with the frequency f.sub.p+f.sub.s, and an impedance Z.sub.3 equal to 150. This CPW thus makes it possible to produce antiresonances at the frequencies k(f.sub.p+f.sub.s) with k an uneven number and k[1, +]. Indeed, when the frequency is equal to k(f.sub.p+f.sub.s) with k an uneven number and k[1, +], the impedance measured at the level of the first connection port J1 is equal to

[00036] $\frac{Z_{3}^{2}}{Z_{L}},$

Z.sub.L being the terminal impedance of the waveguide segment. Yet, in the case of the third waveguide segment T.sub.3, Z.sub.L=+ and thus the impedance measured at the level of the first connection port J1 is zero.

[0094] The real part of the impedance as a function of the frequency of this particular embodiment is illustrated in FIG. 3. The impedance is zero for the pump f.sub.p, signal plus pump f.sub.s+f.sub.p, idler plus pump f.sub.p+f.sub.i frequencies as well as the first harmonic of the pump frequency 2f.sub.p. Moreover, the impedance indeed has a high impedance (thus non zero) at the frequencies f.sub.s and f.sub.i. More particularly, the measured impedance has a local maximum at the frequencies f.sub.s and f.sub.i. The structure of FIG. 2 thus meets all the aforementioned conditions.

[0095] In an alternative of this first exemplary embodiment, the impedance Z.sub.1 of the first waveguide T.sub.1 is chosen equal to 150. The real part of the impedance as a function of the frequency of this exemplary embodiment is illustrated in FIG. 4. It may be noted that if resonances appear at the same frequencies as previously, the peaks associated with these resonances are higher and narrower. In other words, it is possible to modify the gain and the pass band of an amplifier comprising such a circuit by modifying the value of the impedance Z.sub.1 of the first waveguide T.sub.1. In the first exemplary embodiment, the value of this impedance makes it possible to obtain a wide pass band around the signal frequency f.sub.s with nevertheless a narrow minimum at the frequency f.sub.p+f.sub.s and thus a narrower range of frequencies where the noise is optimal. In the alternative of this first exemplary embodiment, the pass band around the signal frequency f.sub.s is reduced but makes it possible to obtain a wider minimum at the frequency f.sub.p+f.sub.s and thus a wider range of frequencies where the noise is optimal.

[0096] In a third exemplary embodiment, f.sub.s=6 GHz, f.sub.i=16.8 GHz and f.sub.p=22.8 GHz are chosen. In this third exemplary embodiment, the first waveguide segment T.sub.1 has a length

[00037] $l = \frac{_{1}}{4},$

with .sub.1 the wavelength associated with the frequency f.sub.1=7.25 GHz and an impedance Z.sub.1 equal to 150. The second waveguide segment T.sub.2 has a length

[00038] $l = \frac{_{2}}{2},$

with .sub.2 the wavelength associated with the frequency f.sub.2=14.5 GHz and an impedance Z.sub.2 equal to 150. The third waveguide segment T.sub.3 has a length

[00039] $l = \frac{_{3}}{4},$

with .sub.3 the wavelength associated with the frequency f.sub.3=21.5 GHz and an impedance Z.sub.2 equal to 150. The real part of the impedance as a function of the frequency of this particular embodiment is illustrated in FIG. 5. In this exemplary embodiment, it is clearly apparent that the frequency of the signal to amplify f.sub.s may be different from the idler frequency f.sub.i and beneficially lower than the idler frequency.

[0097] To optimise both the pass band BW at the signal frequency f.sub.s and the width of the range of frequencies where the noise is optimal, a second embodiment of a first aspect of the invention is illustrated in FIG. 6.

[0098] In this embodiment, the matching circuit comprises a first waveguide segment T.sub.1 of which a first end is connected at the terminal to the input/output terminal ES and a second end is connected to a first end of a second waveguide T.sub.2 and to a first end of a third waveguide T.sub.3. The second ends of the second waveguide T.sub.2 and third waveguide T.sub.3 are for their part each connected to an infinite impedance (that is to say an open circuit). The second waveguide segment T.sub.2 is moreover coupled in a capacitive manner to a fourth waveguide T.sub.2 and the third waveguide segment T.sub.3 is moreover coupled in a capacitive manner to a fifth waveguide T.sub.3 so as to form a coupler. A first end of the fourth waveguide T.sub.2 is connected to earth through a capacitance C.sub.2 and to the supply terminal TA. A second end of the fourth waveguide T.sub.2 is connected to the first connection port J1. A first end of the fifth waveguide T.sub.3 is connected to an infinite impedance (that is to say an open circuit). A second end of the fifth waveguide T.sub.3 is connected to the first connection port J1. The second connection port J2 is for its part connected to earth.

[0099] Unlike the first aforementioned embodiment, the first waveguide segment T.sub.1 makes it possible to transform the impedance so as to favour a wide frequency band without compromising the optimal noise.

[0100] In an exemplary embodiment, f.sub.p=12 GHz and f.sub.s=f.sub.i=6 GHz are chosen. In this exemplary embodiment, the first waveguide segment T1 has a length

[00040] $l = \frac{_{s}}{3.28}$

with .sub.s the wavelength associated with the signal frequency f.sub.s and an impedance Z.sub.1 equal to 42.5. The second waveguide segment T.sub.2 and the fourth waveguide segment T.sub.2 have a length

[00041] $l = \frac{_{p}}{3}$

with .sub.p the wavelength associated with the frequency f.sub.p and an even impedance Z.sub.2P equal to 90 and an uneven impedance Z.sub.2I equal to 9 (these two impedances are due to coupling between the second waveguide segment T.sub.2 and the fourth waveguide segment T.sub.2). Moreover, the third waveguide segment T.sub.3 and the fifth waveguide segment T.sub.3 have a length

[00042] $l = \frac{_{p}}{6}$

with .sub.p the wavelength associated with the frequency f.sub.p and an even impedance Z.sub.3P equal to 90 and an uneven impedance Z.sub.3I equal to 9 (these two impedances are due to coupling between the third waveguide segment and the fifth waveguide segment).

[0101] The amplitude of the real part of the impedance as a function of the frequency obtained with this exemplary embodiment is illustrated in FIG. 7. As previously, the impedance indeed has a high impedance (thus non zero) at the frequencies f.sub.s and f.sub.i. More particularly, the impedance has a high impedance plateau several GHz wide around the signal f.sub.s and idler f.sub.i frequencies. In other words, an amplifier comprising such a circuit will have a wide frequency band around the signal frequency f.sub.s in which the signal will be amplified. In the same way, the impedance is substantially equal to zero for the frequencies f.sub.p and f.sub.p+f.sub.s as well as at low frequencies. The impedance obtained with this structure thus meets the previously established criteria, namely a noise less than 1 photon and makes it possible moreover to separate the DC part of the circuit from the AC part.

[0102] A third embodiment of a matching circuit according to a first aspect of the invention is illustrated in FIG. 8. In this embodiment, the first connection port J1 is connected to the input/output terminal ES through a fourth capacitance C.sub.4. The first connection port J1 is also connected to earth through a first capacitance C.sub.1 and to the supply terminal TA through an inductance L.sub.1. The circuit also comprises a first waveguide segment T.sub.1 of which a first end is connected to an infinite impedance (that is to say an open circuit) and of which a second end is connected to earth through a resistance R. The circuit also comprises a second waveguide segment T.sub.2 of which a first end is at an infinite impedance (that is to say an open circuit) and of which a second end is connected to the second connection port J2 through a second capacitance C.sub.2. The circuit further comprises a third waveguide segment T.sub.3 of which one end is connected to an infinite impedance (that is to say to an open circuit) and of which a second end is connected to the second connection port J2 through a third capacitance C.sub.3. The circuit also comprises a fourth waveguide segment T.sub.1 of which a first end is connected to earth and of which a second end is connected to the second connection port J2. In addition, the first waveguide segment T.sub.1 is coupled in a capacitive manner to the fourth waveguide T.sub.1.

[0103] In an exemplary embodiment, f.sub.p=300 GHz, f.sub.i=290 GHz and f.sub.s=10 GHz are chosen. In this exemplary embodiment, the first waveguide segment T.sub.1 and the fourth waveguide segment T.sub.1 have a length

[00043] $l = \frac{_{1}}{4}$

with .sub.1 the wavelength associated with the frequency f.sub.1=310 GHz, an even impedance Z.sub.1P equal to 25 and an uneven impedance Z.sub.1I equal to 20 (these two impedances are due to coupling between the first waveguide segment and the fourth waveguide segment).

[0104] The second waveguide segment T.sub.2 has a length

[00044] $l = \frac{_{2}}{2}$

with .sub.2 the wavelength associated with the frequency f.sub.2=320 GHz and an impedance Z.sub.2 equal to 50. In addition, the second capacitance C.sub.2 has an impedance of 1 fF. Thus the association of the second waveguide segment T.sub.2 and the second capacitance C.sub.2 makes it possible to obtain an antiresonance at f.sub.p+f.sub.s (that is to say 310 GHz).

[0105] The third waveguide segment T.sub.3 has a length

[00045] $l = \frac{_{3}}{2}$

with .sub.3 the wavelength associated with the frequency f.sub.3=304.6 GHz and an impedance Z.sub.3 equal to 50. In addition, the third capacitance C.sub.3 has an impedance of 0.5 fF. Thus the association of the third waveguide segment T.sub.3 and the third capacitance C.sub.3 makes it possible to obtain an antiresonance at f.sub.p (that is to say 300 GHz).

[0106] Moreover, the first capacitance C.sub.1 has an impedance of 100 fF, the fourth capacitance C.sub.4 has an impedance of 100 pF, the inductance L.sub.1 has an impedance of 100 nH and the resistance R has an impedance of 5. In this exemplary embodiment, the fourth capacitance C.sub.4 and the inductance L.sub.1 make it possible to control the low cut-off frequency (around 80 MHz). It is also possible to choose impedance values for these elements one hundred times lower to centre the pass band around 10 GHz. The amplitude of the real part of the impedance as a function of the frequency obtained with this exemplary embodiment is illustrated in FIG. 9.

[0107] The three preceding embodiments demonstrate through four examples how to obtain a matching circuit having the necessary characteristics to obtain a low noise amplifier. It is thus possible, from a matching circuit according to a first aspect of the invention, to produce a low noise amplifier. Such an amplifier is illustrated in FIG. 10.

[0108] This amplifier comprises a non-linear impedance in the form of a Josephson junction L. The superconductor material of the junction is chosen such that

[00046] $f_{s} < \frac{2 .Math. .Math.}{h}$

with the superconductor gap of the superconductor material. In order to voltage polarise the impedance of the junction, the amplifier also comprises a polarisation source, here in the form of a voltage source ST. The latter is connected by means of the T connection so as to apply a voltage V to the connectors of the Josephson junction L. The presence of this T connection makes it possible to ensure that the high frequency signals come from or are sent to the input/output port ES whereas the low frequency signals come from or are sent to the supply terminal TA.

[0109] In an exemplary embodiment, a matching circuit is chosen according to the first exemplary embodiment, in other words, f.sub.p=12 GHz and f.sub.s=f.sub.i=6 GHz are chosen. The polarisation source is configured to apply a voltage

[00047] $V = 12 .Math. .Math. GHz \frac{h}{2 .Math. .Math. e}$

in order to supply the energy necessary to the Cooper pairs of the junction to generate photons at the signal frequency f.sub.s and at the idler frequency f.sub.i. For these frequencies, the material may be chosen from all superconductors such as for example aluminium. For higher frequencies (several hundreds of GHz), it will be beneficial to choose for example niobium nitride which has a superconductor gap better suited to these high frequencies.

[0110] In this exemplary embodiment, the non-linear impedance is constituted of a Josephson junction. The use of a Josephson junction provides a benefit in terms of manufacture, such a junction being easy to obtain. On the other hand, when a large number of devices are manufactured, it may be difficult to have good homogeneity in the properties of the different Josephson junctions notably in terms of critical current. Yet, in the amplifier according to an embodiment of the invention, the gain is directly dependent on the critical current. In other words, when a Josephson junction is used as non-linear impedance, the amplification gain can vary from one amplifier to the next.

[0111] In order to overcome this drawback, in a second embodiment of a second aspect of the invention, a SQUID (Superconducting Quantum Interference Device) is thus beneficially used. As a reminder, a SQUID comes in the form of a superconducting loop comprising two Josephson Junctions. The critical current of such a structure may be modulated by varying the magnetic flux going through the loop by means of a magnetic field. It is thus possible to adjust in-situ the critical current of the SQUID and thus the gain of the amplifier using such a SQUID. A magnetic field may for example be applied by means of an electric line close to the SQUID and in which a current flows.

MATCHING CIRCUIT FOR LOW NOISE AMPLIFIER AND LOW NOISE AMPLIFIER COMPRISING SUCH A CIRCUIT

Inventors

Cpc classification

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H03F3/19

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H03F7/00

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H03F2200/387

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H03F2200/294

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H03F1/56

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H03F1/565

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H03F19/00

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H03F3/608

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H03F1/56

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Abstract

Claims

Description