JP2896493B2 - High frequency power supply for Josephson integrated circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus suitable for supplying power to a Josephson integrated circuit which can generally operate at a high speed of 1 GHz or more.

[0002]

2. Description of the Related Art A Josephson integrated circuit comprising a group of Josephson logic gates built on a substrate chip is also known.
When it is actually installed and operated in a Josephson computer system or the like, it is, of course, necessary to receive power from the power supply as in other active electronic circuits. Characteristically, since the Josephson logic gate normally operates in a latching mode, the power supply current waveform is in principle a unipolar pulsating waveform (however, when falling, it may enter a slightly opposite polarity region. In order not to impair the essential high-speed operation of the gate, a pulsating waveform having a considerably high frequency, for example, a frequency of 1 GHz or more is required. In principle, a simple combination circuit may be a single-phase pulsating power supply, but in a sequential circuit, the power supply current corresponds to a clock signal in a semiconductor logic circuit. In an integrated circuit, a multi-phase pulsating power source having a different phase from each other, basically a two-phase pulsating current power source having a different phase by 180 ° is used.

Further, although the potential reference of each integrated circuit, that is, the ground potential is generally the ground plane potential on the substrate chip on which the integrated circuit is constructed, this type of Josephson integrated circuit which handles a relatively small voltage is used. In such a case, even a slight change in the ground potential or the ground plane potential poses a serious problem, so a so-called balanced power supply method is adopted so that this does not fluctuate, and the phase differs by 180 ° from the high frequency power source provided outside the substrate chip. First and second phase power currents are provided. Then, in order to achieve impedance matching between the power supply side and the driven integrated circuit side,
An impedance conversion transformer is required between the high frequency power source and each integrated circuit.

FIG. 3 shows a typical conventional configuration example of a high-frequency power supply portion in a Josephson integrated device constructed to satisfy such various conditions. The high-frequency power source 11 outputs first-phase and second-phase power supply currents φ1 and φ2 whose phases are different from each other by 180 ° for balanced power supply. The ground plane (simply indicated by a ground symbol in this figure) for establishing the ground potential of the substrate chip 40 on which the board 41 is mounted generally includes power supply currents φ1 and φ from the high-frequency power source 11.
2 are connected via a shielded conductor surrounding the output line. In addition, the high frequency power source 11 provided outside the substrate chip 40 and other external circuits (not shown)
For connection to the circuit mounted on the board
Bonding pads provided along the periphery of the
42 is used as appropriate.

In accordance with the adoption of the balanced power supply system, impedance conversion transformers 50, 50 are provided on the substrate chip 40 for receiving the power supply currents φ1, φ2 of the first phase and the second phase at the primary winding. I have. The waveforms of the power supply currents φ1 and φ2 can be the waveforms shown in FIG. 1 which will be described later with reference to the present invention, and are sinusoidal waveforms 180 ° out of phase with each other.

Conventionally, however, a single input and a push-pull output were used for the impedance conversion transformer 50 described above. In other words, the primary winding of each of the impedance transforming transformers 50 is a single winding, and one end thereof is connected to the output lines of the power supply currents φ1 and φ2 of the respective phases output from the high-frequency power source 11, and the other ends are both ground planes. (Ground). On the other hand, the secondary winding is a series winding having a midpoint, which is also described with reference to the waveforms shown in FIG. 1.
As a result of the DC bias current Ib having a magnitude smaller by dI than the one-side peak value Ia of the secondary output currents iS-1 and iS-2 differing by 180 ° being supplied to the center point of this secondary winding, the secondary output currents iS-
Both 1 and iS-2 have waveforms that are shifted in the predetermined polarity direction (for example, the positive direction as shown) by the magnitude Ib.

The secondary output currents iS-1 and iS-2 thus constructed
Then, a pair of voltage regulators (current clampers) 3
1 and 31, resulting in two-phase pulsating current waveforms iP-1 and iP-2 with the head of the waveform clamped to a predetermined size, that is, 180 ° out of phase with each other. Power is supplied to each of the pair of Josephson integrated circuits 41 formed on the chip 40 as final power supply current.

As described above, the Josephson integrated circuits 41, 41 are themselves an aggregate of at least one or a plurality of known Josephson logic gates, but the present invention relates to the circuit contents. Therefore, illustration and description are omitted. However, in general, the equivalent impedances Zc, Zc of at least one pair of the Josephson integrated circuits 41, 41 of the first and second sets driven by the pulsating currents iP-1, iP-2 of the first and second phases, respectively. Are in principle equal. If this is not the case, it can be handled by changing the impedance ratio that sandwiches the middle point of the secondary winding of the impedance conversion transformer 50.However, the same value is easier to design and manufacture, and the symmetry of operation can be maintained, so the circuit Reliability also increases. Incidentally, since the equivalent impedance Zc of each Josephson integrated circuit 41 is quite low, the impedance conversion transformer 50 is a so-called down converter with respect to the input / output impedance. For example, the winding ratio of the primary winding to the secondary winding is selected to be 4: 1, and the impedance ratio is set to be 16: 1.

In addition, a plurality of voltage regulators 31, 31 inserted in parallel with the winding between each end of the secondary winding of the impedance conversion transformer 50 and the middle point, respectively, are generally provided by a plurality of n Josephs. In this configuration, the voltage at both ends is stabilized to a voltage n · Vg which is n times the gap voltage Vg of one Josephson junction. However, as described above, the secondary output currents iS-1, iS- of the impedance conversion transformers 50, 50 shown in FIG.
2, or its pulsating output current iP-1, iP-2 from each voltage regulator 31, 31, as the final power supply current supplied to each Josephson integrated circuit 41, 41, its falling edge Sometimes, the voltage regulators 31 and 31 are placed in a slightly reverse polarity region (negative region in the case shown) by dI.
Even if the current flowing through the Josephson junction used in the above becomes zero, the phase rotation does not immediately become zero, and if nothing is done, the so-called punch-through phenomenon is likely to occur. This is to avoid this inconvenience by returning to zero. In this case, the magnitude of the current component dI is selected within a value range smaller than the critical current value Ic of the Josephson junction used in each of the voltage regulators 31, 31.

FIG. 4 shows an example of a conventional plane configuration for one transformer that can be used as the impedance conversion transformers 50, 50 shown in FIG. However, the ground plane 53, the secondary winding 52, the insulating layer provided between the superconductor or superconducting line constituting each of the primary winding 51 is omitted for simplicity of the drawing, Only those superconductors or superconducting lines are shown. As is well known, in a Josephson integrated circuit, a so-called microstrip line structure using a ground plane 53 as a ground conductor is adopted as a superconducting line for transmitting a high-frequency power supply current and a high-frequency signal current. However, since the magnetic coupling circuit would not be completed if this structure was provided where the impedance conversion transformer 50 should be provided, an opening 54 was opened in the ground plane 53, and the secondary The primary windings 52 and 51 are formed by patterning. In this case, the secondary winding 52 is the primary winding
It is provided below 51, and is formed in a winding shape for one turn, and a terminal portion to which the DC bias current Ib is supplied is provided at the midpoint thereof.

The primary winding 51 is on the secondary winding 52, and has one end having a first phase power supply current φ1 or a second phase current supplied from the high frequency power source 11 (not shown in FIG. 3; see FIG. 3). Power supply current φ
2 has a spiral pattern that is wound an appropriate number of times from inside to outside, and is grounded by being connected to the ground plane 53 via the ground contact 55 at the innermost end of the spiral. You. In the case shown in the figure, the number of turns of the primary winding 51 is about three turns, and therefore the impedance conversion ratio is also about 9:
It is about 1, but may be lower. Conversely, it is often difficult to increase the ratio to 16: 1 or more due to deterioration of frequency characteristics or the like with the current technology for the reasons described later.

[0012]

However, as shown in FIG. 3, the impedance conversion transformer 50 generally has a so-called hot side with respect to one end connected to the ground of the primary winding. The equivalent inductance Lp is expected up to the other end, and similarly, a floating capacitance Cs exists at the other end with respect to the ground as shown by a virtual line. Therefore, a resonance system is formed by the inductance Lp and the capacitance Cs, and the resonance frequency fr is fr = 1 / {2π (LpCs) ^1/2 } according to a known equation. Therefore, the impedance conversion transformer 50 is limited in its high frequency characteristics by the resonance frequency fr, and can be actually used only in a frequency range equal to or lower than the resonance frequency fr.

Nevertheless, the conventional impedance conversion transformer uses a single input as described above, so that its equivalent inductance Lp is considerably large, and as a result, as is apparent from the above equation, the resonance frequency fr
However, there is a problem that the inherent high-speed performance of a Josephson integrated circuit capable of potentially operating at a high frequency cannot be sufficiently exhibited.

The present invention has been made in view of this point.
To realize high-speed operation of Josephson integrated circuits, raise the resonance frequency fr in the impedance conversion transformer,
It is intended to suppress the deterioration of the high frequency characteristics in the transformer.

[0015]

According to the present invention, in order to achieve the above object, (a) a middle point is provided in a primary winding of an impedance conversion transformer, and (b) a middle point of the primary winding is connected to a Josephson integrated circuit. (C) Connect the output line of the first-phase power supply current that the high-frequency power source outputs according to the balanced power supply method to one end of the primary winding, and Is connected to the output line of the second phase power supply current which is 180 ° out of phase with the first phase power supply current.

From the basic object of the present invention, it can be seen that the application of the present invention can be applied even if the secondary side of the impedance conversion transformer actually drives only a single-phase driven Josephson integrated circuit. It is possible. However, since it is generally necessary to construct a sequential circuit as described at the beginning, in such a case, a middle point is also provided in the secondary winding of the impedance conversion transformer, and the secondary winding is formed in the secondary winding. A DC bias current is supplied to the point, and a voltage regulator is connected in parallel to a winding portion between one end of the secondary winding and the midpoint and a winding portion between the other end and the midpoint. And a Josephson integrated circuit having at least a first set and a second set, from one end of the secondary winding to the first set of Josephson integrated circuits, and from the other end of the secondary winding, a second set of Josephson integrated circuits. The power supply current may be supplied to each of the integrated circuits.

The impedance conversion transformer may be mounted on the same substrate chip as that on which the Josephson integrated circuit is provided, or a chip carrier for supporting the substrate chip on which the Josephson integrated circuit is provided. It may be provided above.

[0018]

FIG. 1 shows a preferred embodiment of the present invention in which the conventional apparatus shown in FIG. 3 is improved. Therefore, the same reference numerals as those in FIG. 3 indicate the same or the same components, and some of them will not be re-reviewed in this section. Conversely, for such components, the above description can be referred to.

An improvement according to the present invention is found in the impedance transformation transformer 20, and particularly also in the configuration on the primary winding side. The primary winding is a series winding having a middle point, and the middle point is connected to a ground plane (indicated by a ground symbol in the figure) provided on the substrate chip 40. One of the two ends of the primary winding is connected to the output line of the first-phase power supply current φ1 of the high-frequency power source 11 provided outside, and the other end is connected to the second phase 180 ° out of phase with the first-phase power supply current φ1. It is connected to the output line of the power supply current φ2. The ground terminal E of the high-frequency power source 11 is connected to the ground plane of the substrate chip 40 via a shielded conductor for shielding the power supply current line, thereby realizing a balanced power supply system.

As described above, the impedance conversion transformer
The 20 primary windings are configured as a so-called push-pull input type,
When currents 180 degrees out of phase with each other are supplied to both ends, the midpoint potential does not change. Therefore, the potential of the ground plane, and hence the ground potential serving as the reference potential of the Josephson integrated circuits 41 mounted on the substrate chip, does not fluctuate. A balanced power feeding system can be adopted by using only 20. Unlike the conventional configuration in which at least two impedance conversion transformers 50 and 50 are required in principle, the space factor is improved, or the design flexibility is greatly increased.

Moreover, in comparison with the conventional impedance conversion transformer 50 on the same scale, in the case of the impedance conversion transformer 20 used in the present invention, the equivalent inductance of the primary winding is, as schematically shown in FIG. Since Lp / 2 and stray capacitance are half Cs / 2 of the previous one,
Their resonant frequency fr is doubled. That is, the high-frequency characteristics of the impedance conversion transformer 20 used in the present invention are greatly improved, and a power supply current having a higher frequency than before can be supplied to the Josephson integrated circuit 41. High speed performance can be fully exhibited.

The circuit configuration on the secondary side of the impedance conversion transformer 20 used in the present invention is different from the conventional configuration.
No special changes are required. In the case of the drawing, the secondary winding of the impedance conversion transformer 20 is also configured as a push-pull output type having a middle point, and the DC bias current Ib from the DC bias current source 12 flows into the middle point. In this case, the one-sided amplitude Ia of the secondary-side output currents iS-1 and iS-2 is reduced because the punch-through phenomenon described above is prevented.
DC bias current to a value slightly smaller than the current value dI
The size of Ib should be chosen so that
Each of the secondary output currents iS-1 and iS-2 having a phase difference of ° slightly enters the negative region when falling.

Voltage regulators 31 and 31 are connected in parallel between the middle point of the secondary winding and each end, but there is no particular need to modify the voltage regulator itself.
For example, four Josephson junctions in units of 2.8 mV Nb / AlOx / Nb junctions are connected in series, so that the clamp voltage value is 11.2 mV. In addition, DC bias current
The above-described current value dI described with respect to Ib is preferably selected to be slightly smaller than the critical current value Ic of the Josephson junction to be used.

The current waveforms iP-1 and iP-2 thus voltage-clamped and thus current-clamped are applied to the first set of Josephson integrated circuits 41 and the second set of Josephson integrated circuits 41, respectively. Each is supplied as a final power supply current, thereby satisfying the two-phase pulsating power supply drive. As described above, it is preferable that the impedances Zc of the pair of Josephson integrated circuits 41, 41 as viewed from the power supply side are equal to each other, but not limited to this. In addition, the primary and secondary winding ratio of the impedance conversion transformer 20 is generally about 4: 1 or less (about 16: 1 or less in terms of impedance ratio). There is room for practical use of transformers with a large turns ratio.

FIG. 2 shows an example of a plan configuration of the impedance conversion transformer 20 used in the present invention. However, the insulating layers between the superconductor layers or the superconductor lines are not shown for simplification of the drawing. The secondary and primary windings 22 and 21 are provided so as to cross the opening 24 formed in the ground plane 23 provided on the substrate chip 40 (FIG. 1), and thereby a magnetic coupling circuit, that is, a transformer portion is constructed. This point is the same as the previous configuration example described with reference to FIG. 4, and is also the same in that an input terminal for the DC bias current Ib is provided at the middle point of the secondary winding 22. The difference is that a ground contact 25 is provided at the midpoint of the primary winding 21 and is grounded here, while the first-phase power supply current φ1 from the high-frequency power source 11 is provided at the beginning of the winding, at the end of the winding. The point at which the second-phase power supply current φ2 is supplied to the inner end portion through a line portion extending below the primary winding 25 via the base contact 26 is provided. However, of course, the number of windings shown is merely an example for explanation, and is a design problem that can be changed according to individual needs.

Although the preferred embodiments of the present invention have been described above, any modifications are possible as long as they conform to the gist of the present invention. Since the present invention basically discloses a device for improving the high-frequency characteristics of an impedance conversion transformer, as described above, the secondary side is, in principle, a two-phase pulsating power-driven Josephson. It is applicable even if it is not an integrated circuit. Even in such a case, it is often desirable to supply power from an externally provided high-frequency power source 11 in accordance with a balanced power supply system at least on the primary side.

Furthermore, since the impedance conversion transformer according to the present invention can be manufactured in a small size, it can be formed on the same substrate chip 40 as the substrate chip 40 on which the Josephson integrated circuit 41 is mounted. There are many. However, this is not a limitation, and in some cases, the substrate chip 40 may be physically supported and provided on a chip carrier (not shown) often used in this type of field.

[0028]

According to the present invention, as a high-frequency power supply apparatus for a Josephson integrated circuit, a balanced impedance feeding system can be realized with a single impedance conversion transformer, and since the high-frequency characteristics are excellent, a driven Josephson integrated circuit is provided. It can be driven while fully exhibiting its original high speed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a preferred embodiment of a high-frequency power supply device for a Josephson integrated circuit according to the present invention.

FIG. 2 is a diagram illustrating a planar configuration of an impedance conversion transformer that can be used in the present invention.

FIG. 3 is a schematic configuration diagram of a typical example of a conventional high-frequency power supply device for a Josephson integrated circuit.

4 is an explanatory diagram relating to a planar configuration of an impedance conversion transformer used in the conventional device shown in FIG.

[Explanation of symbols]

 11 High-frequency power source, 12 DC bias current source, 20 Impedance conversion transformer, 21 primary winding, 22 secondary winding, 23 ground plane, 24 aperture, 25 ground contact, 26 base contact, 31 voltage regulator (current clamper), 40 substrate chips, 41 Josephson integrated circuits.

Claims (4)

(57) [Claims] 1. A power supply current interposed between a high-frequency power source provided outside a substrate chip and a Josephson integrated circuit provided on the substrate chip and output from the high-frequency power source according to a balanced power supply method. A high-frequency power supply for a Josephson integrated circuit having an impedance conversion transformer for impedance matching between the high-frequency power source and the Josephson integrated circuit with respect to the supply of power; Set a midpoint;
After connecting the midpoint of the primary winding to a ground plane provided on a substrate chip on which a Josephson integrated circuit is mounted; an output line of a first phase power supply current output by the high-frequency power source according to the balanced power supply system Is connected to one end of the primary winding, and the other end is connected to an output line of a second phase power supply current 180 degrees out of phase with the first phase power supply current; Power supply. 2. The apparatus of claim 1, wherein said secondary winding of said impedance transforming transformer also has a midpoint;
A DC bias current is supplied to the midpoint of the secondary winding; a winding portion between one end of the secondary winding and the midpoint; and a winding portion between the other end and the midpoint. A voltage regulator is provided in parallel with each of the winding portions of the first winding; the Josephson integrated circuit has at least a first set and a second set; and the first set of Josephson from the one end of the secondary winding. For integrated circuits,
The second set of Josephson integrated circuits being supplied with a supply current to each of the second set of Josephson integrated circuits from the other end of the secondary winding. 3. Apparatus according to claim 1 or 2, wherein:
The impedance conversion transformer is mounted on the same substrate chip as the substrate chip on which the Josephson integrated circuit is provided. 4. The device according to claim 1 or 2, wherein:
The impedance conversion transformer is provided on a chip carrier that supports the substrate chip provided with the Josephson integrated circuit.