JP4359694B2 - Pulse-driven Josephson waveform generation method and generation circuit - Google Patents
Pulse-driven Josephson waveform generation method and generation circuit Download PDFInfo
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本願発明は、ジョセフソン接合素子アレイを用いたパルス駆動型ジョセフソン波形発生方法及び発生回路に関し、精密計測・標準等の用途に用いるものに関する。 The present invention relates to a pulse-driven Josephson waveform generation method and generation circuit using a Josephson junction element array, and relates to one used for precision measurement and standard applications.
ジョセフソン接合素子をパルス駆動し、任意波形を発生させる方法は米国ＮＩＳＴのグループにより提案されている（下記「非特許文献１」参照）。
また、出力信号と同じ周波数成分を持つ入力電流によりパルス駆動型ジョセフソン波形発生回路を駆動し、１００ｍＶ程度の最大電圧振幅を持つ波形を発生することは実現している（下記「非特許文献２」参照）。
また、単純なキャパシタによりハイパスフィルタを構成し、出力信号の周波数帯域と重畳する周波数成分を減衰させる方式では、小振幅（数桁小さい）波形信号の発生が実現している（下記「非特許文献３」参照）。
A method of generating an arbitrary waveform by driving a Josephson junction element in a pulsed manner has been proposed by a group of NIST (see “Non-Patent Document 1” below).
In addition, it is possible to drive a pulse-driven Josephson waveform generation circuit with an input current having the same frequency component as the output signal to generate a waveform having a maximum voltage amplitude of about 100 mV (see “Non-Patent Document 2” below). "reference).
In addition, in a method in which a high-pass filter is configured with a simple capacitor and a frequency component superimposed on the frequency band of the output signal is attenuated, a small amplitude (several orders of magnitude) waveform signal is generated (see “Non-Patent Document” below). 3 ”).
上記のように出力信号と同じ周波数成分を含む入力電流によりパルス駆動型ジョセフソン波形発生回路を駆動した場合、寄生素子等を通して入力信号の出力への結合があり、これにより出力波形の精度が制限される。
例えば、パルス発生回路とジョセフソン接合アレイとの間の配線ケーブルには分布定数として抵抗成分、誘導性リアクタンス成分および容量性リアクタンス成分が存在する。
入力信号成分が回路に残っていると、その信号成分が誘導性リアクタンス成分および容量性リアクタンス成分に作用し、不要な出力を発生し、望ましい出力信号を得ることができなくなる。
また、上記キャパシタによる周波数分離方式で得られる電圧では、大振幅出力とするための十分な動作マージンが得られず応用範囲が著しく限られている。
When the pulse-driven Josephson waveform generation circuit is driven by an input current that contains the same frequency component as the output signal as described above, there is a coupling to the output of the input signal through a parasitic element, which limits the accuracy of the output waveform. Is done.
For example, a wiring cable between a pulse generation circuit and a Josephson junction array has a resistance component, an inductive reactance component, and a capacitive reactance component as distributed constants.
If the input signal component remains in the circuit, the signal component acts on the inductive reactance component and the capacitive reactance component, generates an unnecessary output, and cannot obtain a desired output signal.
Further, with the voltage obtained by the frequency separation method using the capacitor, a sufficient operation margin for obtaining a large amplitude output cannot be obtained, and the application range is extremely limited.
本発明の目的は、上記問題点に鑑み、ジョセフソン接合素子をパルス駆動し、大出力と精度を同時に実現して任意波形を発生させる波形発生方法および装置を提供するものである。 In view of the above-described problems, an object of the present invention is to provide a waveform generation method and apparatus for generating an arbitrary waveform by driving a Josephson junction element in a pulsed manner, realizing high output and accuracy at the same time.
本発明では、入力バルスとして、従来の波形を上記のような波形、つまり時間軸でみて主として一つの大きな尖頭値を有する波から構成され、かつ波の最大値と最小値の比が大きく、周波数軸でみて出力波形の周波数と重畳しない領域の二つの周波数ｆ１およびｆ２で規定される幅を持つ波形で置き換えることにより、任意信号出力においても波形精度を高めることができる。
換言すると、入力信号（最終的に出力させたい信号）が波形発生回路に残っていると、この入力信号が途中の回路素子に作用して変化した信号が最終的に出力に現れ、欲しい信号のみが出力されなくなる場合が発生する。これをなくすために、周波数スペクトル上で入力信号成分を除いた信号を使って最終出力を得る。具体的には、
In the present invention, as an input pulse, the conventional waveform is composed of a waveform as described above, that is, a wave having one large peak value when viewed on the time axis, and the ratio between the maximum value and the minimum value of the wave is large, By replacing with a waveform having a width defined by two frequencies f1 and f2 in a region that does not overlap with the frequency of the output waveform as seen on the frequency axis, the waveform accuracy can be improved even when outputting an arbitrary signal.
In other words, if the input signal (the signal that you want to output in the end) remains in the waveform generation circuit, the signal that changes when this input signal acts on the circuit elements in the middle will finally appear at the output, and only the desired signal May not be output. In order to eliminate this, a final output is obtained using a signal obtained by removing the input signal component on the frequency spectrum. In particular,
（１）パルス駆動型ジョセフソン波形発生方法は、
パルス駆動型ジョセフソン波形発生回路において、出力する予定の信号を入力し、該信号に基づきパルス列信号を形成し、該パルス列信号により任意波形の信号を発生する方法であって、
前記パルス列信号を構成する基本パルスは、時間軸でみて一つの大きな尖頭値を有する波形を有し、且つ前記波形の最大値と最小値の比が大きくなるように構成し、
前記パルス列信号は、スペクトル特性が周波数軸でみて出力波形の周波数と重畳しない領域を有し、その領域を画成する二つの周波数ｆ１およびｆ２で規定される幅を持つ信号で置き換えることを特長とする。
(1) The pulse-driven Josephson waveform generation method is
In a pulse drive type Josephson waveform generation circuit, a signal to be output is input, a pulse train signal is formed based on the signal, and a signal having an arbitrary waveform is generated by the pulse train signal,
The basic pulse constituting the pulse train signal has a waveform having one large peak value on the time axis, and is configured such that the ratio between the maximum value and the minimum value of the waveform is large,
The pulse train signal has a region in which the spectrum characteristic is not superimposed on the frequency of the output waveform on the frequency axis, and is replaced with a signal having a width defined by two frequencies f1 and f2 that define the region. To do.
（２）上記（１）記載のパルス駆動型ジョセフソン波形発生方法は、
上記置き換える信号の、時間軸でみた尖頭値と最小値の比が少なくとも２倍以上であることを特長とする。
（３）上記（１）記載のパルス駆動型ジョセフソン波形発生方法は、
上記領域を画成する二つの周波数ｆ１およびｆ２のうち、高い周波数ｆ２は低い周波数ｆ１の２倍以上にしたことを特長とする。
（４）上記（１）記載のパルス駆動型ジョセフソン波形発生方法は、
上記領域を画成する二つの周波数ｆ１およびｆ２のうち、低い周波数ｆ１が、前記出力する予定の信号の周波数分布の最大周波数の少なくとも１０倍以上としたことを特長とする。
(2) The pulse-driven Josephson waveform generation method described in (1) above is
The ratio of the peak value and the minimum value on the time axis of the replacement signal is at least twice or more.
(3) The pulse-driven Josephson waveform generation method described in (1) above is
Of the two frequencies f1 and f2 that define the region, the high frequency f2 is more than twice the low frequency f1.
(4) The pulse-driven Josephson waveform generation method described in (1) above is
Of the two frequencies f1 and f2 that define the region, the low frequency f1 is at least 10 times the maximum frequency of the frequency distribution of the signal to be output.
（５）上記（１）記載のパルス駆動型ジョセフソン波形発生方法は、
出力すべき波形データを入力し、
該波形データをデルタシグマ変調して前記波形データの信号周波数スペクトル領域と
スペクトル特性が周波数軸でみて出力波形の周波数と重畳しない領域を有し、前記波形データの２以上の任意倍数の周波数スペクトル領域を含む雑音周波数スペクトル領域を
含む２値パルス列データに変換し、
前記パルス列データを基本パルス波形で置き換えて上限周波数と下限周波数とからなる雑音周波数スペクトル領域特性を有する駆動波形時系列データとし、
前記駆動波形時系列データをアナログ−デジタル変換して駆動電圧として出力し、
前記駆動電圧を線路常数を介して超伝導状態のジョセフソン接合アレイに入力して、前記信号周波数スペクトル領域と雑音周波数スペクトル領域を有する周波数特性の接合アレイ両端電圧を発生させ、
前記ジョセフソン接合アレイの両端電圧をローパスフィルタを介して前記信号周波数スペクトル領域のみを有する出力電圧波形を取り出すことを特徴とするパルス駆動型ジョセフソン波形発生方法。
(5) The pulse-driven Josephson waveform generation method described in (1) above is
Input the waveform data to be output,
A signal frequency spectrum region of the waveform data obtained by delta-sigma modulation of the waveform data and a region in which the spectrum characteristic does not overlap with the frequency of the output waveform as seen on the frequency axis, Is converted into binary pulse train data including a noise frequency spectrum region including
Replacing the pulse train data with a basic pulse waveform and driving waveform time-series data having noise frequency spectrum region characteristics consisting of an upper limit frequency and a lower limit frequency,
The drive waveform time series data is analog-digital converted and output as a drive voltage,
The drive voltage is input to a Josephson junction array in a superconducting state via a line constant to generate a voltage across the junction array having a frequency characteristic having the signal frequency spectrum region and the noise frequency spectrum region,
An output voltage waveform having only the signal frequency spectrum region is extracted from the voltage across the Josephson junction array through a low-pass filter.
（６）パルス駆動型ジョセフソン波形発生回路は、
パルス発生回路と、
複数のジョセフソン接合素子を直列接続したジョセフソン接合アレイ量子化器と、
前記パルス発生回路と前記ジョセフソン接合アレイ量子化器を接続する高周波伝送路と、
前記ジョセフソン接合アレイ量子化器の出力をフィルタを介して取り出す出力回路とからなり、
前記パルス発生回路は、
出力すべき波形データを入力し、該波形データをデルタシグマ変調して前記波形データの信号周波数スペクトル領域と前記波形データの２以上の任意倍数の周波数スペクトルを含む雑音周波数スペクトル領域を含む２値パルス列データに変換するデルタシグマ変調回路と、
この２値パルス列データを基本パルス波形で畳み込み上限周波数と下限周波数とからなる雑音周波数スペクトル領域特性を有する駆動波形時系列データとするパルス波形畳み込み回路と、
この駆動波形時系列データを駆動電圧として出力するデジタルーアナログ変換器とから構成し、
前記ジョセフソン接合アレイ量子化器は、
高周波伝送路を介して入力された前記駆動電圧を前記信号周波数スペクトル領域と雑音周波数スペクトル領域を有する周波数特性の接合アレイ両端電圧として発生させるジョセフソン接合アレイと、
前記ジョセフソン接合アレイの両端電圧の周波数スペクトル特性を信号スペクトル領域のみの特性の出力電圧信号を取り出すローパスフィルタと
からなることを特徴とする。
(6) The pulse-driven Josephson waveform generator circuit
A pulse generation circuit;
A Josephson junction array quantizer in which a plurality of Josephson junction elements are connected in series;
A high-frequency transmission line connecting the pulse generation circuit and the Josephson junction array quantizer;
An output circuit that extracts the output of the Josephson junction array quantizer through a filter;
The pulse generation circuit includes:
The waveform data to be output is input, the waveform data is subjected to delta-sigma modulation, and a binary pulse train including a signal frequency spectrum region of the waveform data and a noise frequency spectrum region including a frequency spectrum of an arbitrary multiple of two or more of the waveform data. Delta-sigma modulation circuit to convert to data,
A pulse waveform convolution circuit which converts this binary pulse train data into a drive waveform time-series data having a noise frequency spectrum domain characteristic composed of a convolution upper limit frequency and a lower limit frequency with a basic pulse waveform;
It consists of a digital-analog converter that outputs this drive waveform time series data as drive voltage,
The Josephson junction array quantizer is
A Josephson junction array for generating the drive voltage input via a high-frequency transmission line as a voltage across the junction array having a frequency characteristic having the signal frequency spectrum region and the noise frequency spectrum region;
The frequency spectrum characteristic of the voltage across the Josephson junction array is composed of a low-pass filter that extracts an output voltage signal having a characteristic only in the signal spectrum region.
本発明は、発生信号波形の精度を高めることができる。
本発明は、出力すべき波形信号を入力し、その波形信号の１倍と２以上の任意倍数の周波数スペクトル特性を有する２値パルス列信号を形成し、その２値パルス列信号を基本パルス波形で置き換えて前記２以上の任意倍数の周波数スペクトル特性のみを有する駆動波形時系列データに変換し、駆動波形時系列データを伝送系を介してジョセフソン接合アレイ量子化器へ入力し、その量子化器でもとの波形信号の１倍と２以上の任意倍数の周波数スペクトル特性を有する電圧信号を再生し、最後にローパスフィルタを介して低域のもとの波形信号の１倍の周波数スペクトル特性を有する電圧信号を出力するので、伝送系をとおす信号を入力波形信号の周波数スペクトル領域ではない高域、即ち、入力波形信号の２以上の任意倍数の周波数スペクトル領域の信号を用いるので、伝送系の分布常数の影響が受けにくくなり、ジョセフソン接合アレイ量子化器を用いた再生時、入力波形信号の１倍の周波数スペクトル領域の信号を再生することができるようになる。
The present invention can improve the accuracy of the generated signal waveform.
The present invention inputs a waveform signal to be output, forms a binary pulse train signal having frequency spectrum characteristics of an arbitrary multiple of 1 and 2 of the waveform signal, and replaces the binary pulse train signal with a basic pulse waveform. To drive waveform time-series data having only frequency spectrum characteristics of an arbitrary multiple of 2 or more, and input the drive waveform time-series data to the Josephson junction array quantizer via the transmission system. A voltage signal having frequency spectrum characteristics of 1 and 2 or more multiples of the waveform signal is reproduced, and finally a voltage having a frequency spectrum characteristic of 1 times that of the original low-frequency waveform signal through a low-pass filter. Since the signal is output, the signal passing through the transmission system is not a frequency spectrum region of the input waveform signal, that is, a frequency spectrum of an arbitrary multiple of two or more of the input waveform signal. The signal in the frequency domain is less affected by the distribution constant of the transmission system, and at the time of reproduction using the Josephson junction array quantizer, it is possible to reproduce a signal in the frequency spectrum domain that is one time the input waveform signal. become able to.
本発明を実施するための最良の形態を図に基づいて詳細に説明する。 The best mode for carrying out the present invention will be described in detail with reference to the drawings.
（ 繰返しパルスに対する応答 ）
本願発明の方法で用いる装置のブロック図を図１に示す。図１は任意波形発生のための装置のブロック構成図である。
装置は、主に、ジョセフソン接合アレイ２とパルス発生回路１と出力回路となる負荷（測定器）３からなる。
ジョセフソン接合アレイ２は、複数のジョセフソン接合素子１４を直列接続したジョセフソン接合アレイ量子化器１０と、そのジョセフソン接合アレイ量子化器１０の一端に接続した終端抵抗１６およびローパスフィルタＬＰＦ１５と、ジョセフソン接合アレイ量子化器１０の他端に接続したローパスフィルタＬＰＦ１３および結合コンデンサ１２からなる。終端抵抗１６は接地される。結合コンデンサ１２にはパルス発生回路１へのケーブル１１が接続される。
パルス発生回路１は、室温に置かれ、下記の式（１）を満たす図２の波形のパルスを発生する。
(Response to repetitive pulse)
A block diagram of an apparatus used in the method of the present invention is shown in FIG. FIG. 1 is a block diagram of an apparatus for generating an arbitrary waveform.
The apparatus mainly includes a Josephson junction array 2, a pulse generation circuit 1, and a load (measuring instrument) 3 serving as an output circuit.
The Josephson junction array 2 includes a Josephson junction array quantizer 10 in which a plurality of Josephson junction elements 14 are connected in series, a termination resistor 16 and a low-pass filter LPF 15 connected to one end of the Josephson junction array quantizer 10. The low-pass filter LPF 13 and the coupling capacitor 12 are connected to the other end of the Josephson junction array quantizer 10. The termination resistor 16 is grounded. A cable 11 to the pulse generation circuit 1 is connected to the coupling capacitor 12.
The pulse generation circuit 1 is placed at room temperature and generates a pulse having the waveform of FIG. 2 that satisfies the following equation (1).
負荷３は、室温に置かれ、十分高いインピーダンスを持つ機器、例えば、測定器である電圧計Ｖから構成される。負荷３のそれぞれの端子は、ローパスフィルタＬＰＦ１３とローパスフィルタＬＰＦ１５に接続される。
図１では、入力パルス信号発生回路１は室温に置かれる。直列ジヨセフソン接合アレイ２は低温で超伝導状態に置かれる。負荷回路３は室温に置かれ、十分高いインピーダンスを持つ。
前記量子化器１０は、分布容量や分布インダクタンスがあるため、信号スペクトル特性において、入力信号成分が残っているとその信号成分が分布容量や分布インダクタンスに作用して、不要な出力を発生し、望ましい出力信号を得ることができない。この問題点を解消するために、本願発明は、本発明の基本パルスとなるパルス波形のパルス信号を用いて、図４の信号処理に裏付けられた任意波形発生方法により解消する。
パルス発生回路１は、図４に示すように、ΔΣ変調回路２１、パルス波形畳み込み回路２２、高周波Ｄ／Ａ変換器２３からなる。パルス発生回路１の動作は後述する。
The load 3 is placed at room temperature and includes a device having a sufficiently high impedance, for example, a voltmeter V that is a measuring instrument. Each terminal of the load 3 is connected to a low pass filter LPF 13 and a low pass filter LPF 15.
In FIG. 1, the input pulse signal generation circuit 1 is placed at room temperature. The series Josephson junction array 2 is placed in a superconducting state at a low temperature. The load circuit 3 is placed at room temperature and has a sufficiently high impedance.
Since the quantizer 10 has a distributed capacity and a distributed inductance, if an input signal component remains in the signal spectrum characteristics, the signal component acts on the distributed capacity and the distributed inductance to generate an unnecessary output, The desired output signal cannot be obtained. In order to solve this problem, the present invention solves this problem by using an arbitrary waveform generation method supported by the signal processing of FIG. 4 using a pulse signal having a pulse waveform which is a basic pulse of the present invention.
As shown in FIG. 4, the pulse generation circuit 1 includes a ΔΣ modulation circuit 21, a pulse waveform convolution circuit 22, and a high frequency D / A converter 23. The operation of the pulse generation circuit 1 will be described later.
まず，課題を解決するための手段の項で述べた条件、即ち、
（１）時間軸でみて主として一つの大きな尖頭値を有する波から構成され、
（２）かつ波の最大値と最小値の比が大きく、
（３）周波数軸でみて出力波形の周波数と重畳しない領域の二つの周波数ｆ１およびｆ２で規定される幅を持つ波形、
の条件を満たすパルス波形として次式１であらわされる波形を用いて、理論的に本方式の有効性を確認した。
(1) It is mainly composed of a wave having one large peak value on the time axis,
(2) And the ratio of the maximum value and minimum value of the wave is large,
(3) a waveform having a width defined by two frequencies f1 and f2 in a region that does not overlap with the frequency of the output waveform as seen on the frequency axis;
Using the waveform represented by the following equation 1 as the pulse waveform satisfying the above condition, the effectiveness of this method was theoretically confirmed.
上記式１は一種のフィルタを構成し、そのｆＨおよびｆＬはパラメータとなる。
式１のパルス信号を時間軸でみた波形を図２に示す。図２は時間軸で表示したパルス波形図である。
図２のパルス波形は、
（１）信号波形の積分値がゼロになるように形成される、即ち、直流分がゼロになる、
（２）電流値ゼロ点を基準にしてみた、正負の最大振幅値の比を大きくする、
（３）低周波を含まない、
（４）ジョセフソン接合素子を動作させることができる、
特性を有する。
Equation 1 above constitutes a kind of filter, and its f H and f L are parameters.
FIG. 2 shows a waveform of the pulse signal of Equation 1 viewed on the time axis. FIG. 2 is a pulse waveform diagram displayed on the time axis.
The pulse waveform in FIG.
(1) The integral value of the signal waveform is formed to be zero, that is, the direct current component is zero.
(2) Increase the ratio of the maximum positive and negative amplitude values with reference to the zero point of the current value.
(3) Does not include low frequencies,
(4) The Josephson junction element can be operated.
Has characteristics.
図２の波形のパルスは周波数ｆＬ以上周波数ｆＨ以下の周波数成分のみを持つようになる。
図２の波形のパルスを単位パルス又は基本パルスとして以下の処理に用いる。
この基本パルスを時間的に連続して発生させた入力パルス列（テストパルス列）信号は図３のようになる。
The waveform of the pulse 2 will have only the following frequency component frequency f L or higher frequency f H.
The pulse having the waveform of FIG. 2 is used as a unit pulse or basic pulse for the following processing.
FIG. 3 shows an input pulse train (test pulse train) signal in which the basic pulses are generated continuously in time.
図３は動作確認に用いた繰返しパルス列信号である。
繰返しパルス列信号のパルス間隔をｆＬ／２の逆数の整数倍としたとき、パルスピーク値が変化しないようになる。ここで本方法が安定に適用できるか否かを決める特性として、入力バルス列の配置として図３（Ａ）、（Ｂ）に示す両配置に対し、外部からアレイヘ流出入する電流Ｉｄｃが変化した時にジョセフソン接合アレイが正しく動作する領域を調べた。
ここで用いたパラメータは下記のようになる。
FIG. 3 shows a repetitive pulse train signal used for operation confirmation.
When the pulse interval of the repetitive pulse train signal is set to an integral multiple of the reciprocal of f L / 2, the pulse peak value does not change. Here, as a characteristic that determines whether or not the present method can be stably applied, the current I dc flowing into and out of the array from the outside changes in both arrangements shown in FIGS. 3A and 3B as the arrangement of the input pulse train. The region where the Josephson junction array operates correctly was investigated.
The parameters used here are as follows.
−ジョセフソン接合アレイ
＊臨界電流ＩＣ＝３ｍＡ
＊特性周波数ｆＣ＝１６ＧＨｚ
＊伝送線路インピーダンス５０Ω
＊接合数１０００
-Josephson Junction Array * Critical current I C = 3 mA
* Characteristic frequency f C = 16 GHz
* Transmission line impedance 50Ω
* Number of junctions 1000
−入力パルス信号
＊上限周波数ｆＨ＝ｆｃ＝１６ＧＨｚ
＊下限周波数ｆＬ＝０．１ｆＨ＝１．６ＧＨｚ
＊パルス周波数ｆｐ＝２ｆＬ＝３．２ＧＨｚ
＊パルスピーク電流Ｉｍａｘ＝２．４１ｃ＝７．２ｍＡ
-Input pulse signal * Upper limit frequency f H = fc = 16 GHz
* Lower limit frequency f L = 0.1 f H = 1.6 GHz
* Pulse frequency f p = 2f L = 3.2GHz
* Pulse peak current I max = 2.41c = 7.2 mA
その結果、正しい出力を得ることができる電流Ｉｄｃは、
−図３のテストパルス列Ａに対して、
−０．３２ＩＣ（−０．９６ｍＡ）＜ＩｄＣ＜０．５８ＩＣ（１．７４ｍＡ）
の範囲で、
−テストパルス列Ｂに対して、
−０．２６ＩＣ（−０．７８ｍＡ）＜ＩｄＣ＜０．２６ＩＣ（０．７８ｍＡ）
の範囲で、
正常動作が確認された。
これにより、パルス列のパターンによらず、ジョセフソン接合の臨界電流の±２６％以上の電流マージンで正常動作することがわかった。したがって本方式による任意波形発生装置は、精密計測への応用が可能な動作マージンを持つと言える。
（ 波形生成例 ）
As a result, the current I dc that can obtain the correct output is
-For test pulse train A in FIG.
−0.32 I C (−0.96 mA) <I dC <0.58 I C (1.74 mA)
In the range
-For test pulse train B,
−0.26 I C (−0.78 mA) <Id C <0.26 I C (0.78 mA)
In the range
Normal operation was confirmed.
As a result, it was found that the device operates normally with a current margin of ± 26% or more of the critical current of the Josephson junction regardless of the pulse train pattern. Therefore, it can be said that the arbitrary waveform generator by this method has an operation margin that can be applied to precision measurement.
(Waveform generation example)
上記パルスを用いて、任意波形を発生するための手順を図４に示す。
図４は本発明の回路装置の各部構成での信号波形およびスペクトルを示す説明図である。
図４中の（ａ）は波形データを２値パルス列データに変換した波形図、（ｂ）は２値パルス列データを駆動波形時系列データに変換した波形図、（ｃ）は駆動波形時系列データをＤ／Ａ変換し、ジュセフソン接合（アレイ）量子化器を通した接合（アレイ）両端電圧波形の波形図を示す。
FIG. 4 shows a procedure for generating an arbitrary waveform using the pulse.
FIG. 4 is an explanatory diagram showing signal waveforms and spectra in the respective components of the circuit device of the present invention.
4A is a waveform diagram obtained by converting waveform data into binary pulse train data, FIG. 4B is a waveform diagram obtained by converting binary pulse train data into drive waveform time series data, and FIG. 4C is drive waveform time series data. Is a waveform diagram of the voltage waveform across the junction (array) through D / A conversion and passing through a Josephson junction (array) quantizer.
ΔΣ（デルタシグマ）変調回路は、例えば、例えばオーバーサンプリングされた入力信号と帰還電圧との差分値を積分する積分器と、その積分値を１ビット量子化してビットストリームを生成・出力する１ビット量子化器と、この１ビット量子化器の出力のレベルに応じて帰還電圧をフィードバックする帰還電圧選択部とにより構成される。
パルス発生回路に任意波形データ（数値データ）、例えば時系列波形（ａ）のアナログ信号を入力すると、該波形（ａ）の信号はΔΣ変調回路２１を介して時系列波形（ｂ）の２値（＋１、−１）パルス列（数値データ）信号に変調される。ΔΣ変調回路２１はアナログ信号をパルスの粗密波に変調する回路である。波形（ａ）の信号スペクトルは、縦軸信号強度、横軸周波数のスペクトル特性（ｆ）において、低い周波数領域に抑え込まれている。
The ΔΣ (delta sigma) modulation circuit is, for example, an integrator that integrates a difference value between an oversampled input signal and a feedback voltage, and 1 bit that generates and outputs a bitstream by quantizing the integrated value by 1 bit. A quantizer and a feedback voltage selector that feeds back a feedback voltage in accordance with the output level of the 1-bit quantizer.
When arbitrary waveform data (numerical data), for example, an analog signal of a time series waveform (a) is input to the pulse generation circuit, the signal of the waveform (a) is binary of the time series waveform (b) via the ΔΣ modulation circuit 21. Modulated to a (+1, -1) pulse train (numerical data) signal. The ΔΣ modulation circuit 21 is a circuit that modulates an analog signal into a pulsed dense wave. The signal spectrum of the waveform (a) is suppressed to a low frequency region in the spectral characteristics (f) of the vertical axis signal intensity and the horizontal axis frequency.
ΔΣ変調後の波形（ｂ）の信号は、スペクトル特性（ｇ）において、信号スペクトル領域と雑音スペクトル領域に分離する。雑音スペクトルは、信号（ａ）の２倍波、４倍波、・・・、２Ｎ倍波（但し、Ｎは自然数）のスペクトル成分を含む。
波形（ｂ）の２値パルス列信号はパルス波形畳み込み回路２２を介して時系列波形（ｃ）に示す駆動波形時系列データ（数値データ）を出力する。パルス波形畳み込み回路２２はフィルタ処理回路で構成する。回路２２のフィルタ処理により、波形（ｂ）のパルス１個ずつは図２に示す基本パルスで置き換え、また、波形（ｂ）の時系列特性は波形（ｃ）におけるパルスの時系列特性により置き換える。
The signal of the waveform (b) after ΔΣ modulation is separated into a signal spectrum region and a noise spectrum region in the spectrum characteristic (g). The noise spectrum includes spectral components of the second harmonic, fourth harmonic,..., 2 N harmonic (where N is a natural number) of the signal (a).
The binary pulse train signal of the waveform (b) outputs drive waveform time series data (numerical data) shown in the time series waveform (c) via the pulse waveform convolution circuit 22. The pulse waveform convolution circuit 22 is configured by a filter processing circuit. By the filtering process of the circuit 22, each pulse of the waveform (b) is replaced with the basic pulse shown in FIG. 2, and the time series characteristics of the waveform (b) are replaced with the time series characteristics of the pulses in the waveform (c).
波形（ｃ）の時系列信号のスペクトル特性は、スペクトル特性（ｈ）における雑音スペクトル領域の上限周波数が前記式（１）のｆＨを表し、下限周波数が（１）のｆＬを表わす。
時系列波形（ａ）の入力信号の成分は、時系列波形（ｃ）のパルス列のパターンに残してある。
The spectral characteristics of the time-series signal waveform (c) represents the f H of the noise spectrum upper frequency above formula region (1) in the spectral properties (h), represents the lower limit frequency of f L (1).
The component of the input signal of the time series waveform (a) is left in the pulse train pattern of the time series waveform (c).
時系列波形（ｃ）の駆動波形時系列データ（数値データ）は、次に、高周波Ｄ／Ａ変換器２３を介して駆動電圧波形を有する信号に変換され、ケーブル１１を介してジョセフソン接合アレイ２に入力される。
前記駆動電圧波形を有する信号は、ジョセフソン接合アレイ２のＪｏｓｅｐｈｓｏｎ接合（アレイ）量子化器１０をとおすことによりその量子化器１０の両端に時系列波形（ｄ）の電圧信号として形成される。
The drive waveform time-series data (numerical data) of the time-series waveform (c) is then converted into a signal having a drive voltage waveform via the high frequency D / A converter 23, and the Josephson junction array via the cable 11. 2 is input.
The signal having the driving voltage waveform is formed as a voltage signal having a time series waveform (d) at both ends of the quantizer 10 by passing through the Josephson junction (array) quantizer 10 of the Josephson junction array 2.
この時系列波形（ｄ）の電圧信号のスペクトル特性は、スペクトル特性（ｉ）の特性となる。即ち、スペクトル特性（ｉ）は前記スペクトル特性（ｇ）を復調した特性となる。
この信号スペクトル領域と雑音スペクトル領域を有するスペクトル特性（ｉ）の接合（アレイ）両端電圧信号をＬＰＦ１３および１５を介して低域信号だけの出力（電圧波形）信号として取り出す。この出力信号は、時系列波形（ｅ）の信号であり、前記時系列波形（ａ）の入力信号を復調した信号となる。また、この出力信号のスペクトル特性は、スペクトル特性図（ｊ）の特性となり、信号スペクトル領域だけの特性となる。
従って、入力信号波形を再現して出力することができることとなる。
The spectral characteristic of the voltage signal of this time series waveform (d) is the characteristic of the spectral characteristic (i). That is, the spectral characteristic (i) is a characteristic obtained by demodulating the spectral characteristic (g).
The voltage signal at both ends of the junction (array) of the spectrum characteristic (i) having the signal spectrum region and the noise spectrum region is taken out as an output (voltage waveform) signal only of the low-frequency signal through the LPFs 13 and 15. This output signal is a signal having a time series waveform (e), and is a signal obtained by demodulating the input signal having the time series waveform (a). Further, the spectrum characteristic of the output signal is the characteristic of the spectrum characteristic diagram (j), and is the characteristic of only the signal spectrum region.
Therefore, the input signal waveform can be reproduced and output.
前記超伝導状態におかれたジョセフソン接合アレイに関しては、下記のような条件で、１０ＭＨｚの正弦波電圧を発生させる数値実験を行なった。
−ジョセフソン接合アレイ
＊臨界電流１Ｃ＝３ｍＡ
＊特性周波数ｆＣ＝２０．４８ＧＨｚ
＊伝送線路インピーダンス５０Ω
＊接合数１０２４
For the Josephson junction array placed in the superconducting state, a numerical experiment was performed to generate a 10 MHz sinusoidal voltage under the following conditions.
-Josephson junction array * Critical current 1 C = 3 mA
* Characteristic frequency f C = 20.48 GHz
* Transmission line impedance 50Ω
* Number of junctions 1024
−入力バルス信号
＊上限周波数ｆＣ＝２０．４８ＧＨｚ
＊下限周波数ｆＣ＝Ｏ．１２５ｆＨ＝２．５６ＧＨｚ
＊パルス周波数加＝２ｆＬ＝５．１２ＧＨｚ
＊パルスピーク電流Ｉｍａｘ＝２．５１ｃ＝７．５ｍＡ
-Input pulse signal * Upper limit frequency f C = 20.48 GHz
* Lower limit frequency f C = O. 125 fH = 2.56 GHz
* Add pulse frequency = 2fL = 5.12GHz
* Pulse peak current Imax = 2.51c = 7.5 mA
−出力電圧波形
＊正弦波
＊周波数：１０．００ＭＨｚ
＊ピーク電圧：５．４２ｍＶ
-Output voltage waveform * Sine wave * Frequency: 10.00MHz
* Peak voltage: 5.42mV
その結果、図４中の（ａ）〜（ｅ）の波形に対応する電力スペクトルとして、それぞれ図５〜図９が得られ、駆動波形として出力信号と同じ周波数成分を含まず、なおかつ大振幅出力が可能であることが確認された。
図５〜９は正弦波発生の数値実験での各部電力スペクトルを示す図である。図中、横軸は周波数（ＭＨｚ）、縦軸は電力強度（ｄＢ）を示す。
１０ＭＨｚの正弦波発生数値実験における、装置各部分での信号波形の電力スペクトルを図５−９に示す。
発生を希望する正弦波のスペクトル図５では、誤差分を除き１０ＭＨｚ成分のみ存在する。この信号波形をΔΣ変調回路に通して得られたパルス列信号のスペクトル図６は１０ＭＨｚ成分に加え、変調により発生したい信号成分が変換された高周波成分を含むものとなる。この波形を、前述のパルス波形畳み込み回路を通すことにより得られた信号の電力スペクトルは、発生させたい信号波形のスペクトル（この場合は１０ＭＨｚ）と重ならない、帯域制限されたものとなる（図７）。この信号を、Ｊｏｓｅｐｈｓｏｎ接合アレイ量子化器に入力し発生された電圧信号のスペクトルは図８となり、図６と同様に １０ＭＨｚ成分と高周波成分を含むものである。これを、低周波通過フィルタ（ＬＰＦ）を通して最終的に得られた信号の電力スペクトル図９においては、１０ＭＨｚ信号は他の成分に比べ７０ｄＢ以上の大きな信号雑音比をもっており、精密信号波形発生装置として機能していることがわかる。
As a result, FIG. 5 to FIG. 9 are obtained as power spectra corresponding to the waveforms (a) to (e) in FIG. 4, respectively, and the drive waveform does not contain the same frequency component as the output signal and has a large amplitude output. Is confirmed to be possible.
5 to 9 are diagrams showing the power spectrum of each part in a numerical experiment of sine wave generation. In the figure, the horizontal axis represents frequency (MHz) and the vertical axis represents power intensity (dB).
FIG. 5-9 shows the power spectrum of the signal waveform at each part of the apparatus in the numerical experiment of 10 MHz sine wave generation.
In the spectrum of a sine wave that is desired to be generated, only a 10 MHz component exists except for an error. The spectrum diagram 6 of the pulse train signal obtained by passing this signal waveform through the ΔΣ modulation circuit includes a high frequency component obtained by converting the signal component desired to be generated by the modulation in addition to the 10 MHz component. The power spectrum of the signal obtained by passing this waveform through the aforementioned pulse waveform convolution circuit is band-limited so as not to overlap with the spectrum of the signal waveform to be generated (in this case, 10 MHz) (FIG. 7). ). The spectrum of the voltage signal generated by inputting this signal to the Josephson array quantizer is shown in FIG. 8 and includes a 10 MHz component and a high frequency component as in FIG. In the power spectrum of the signal finally obtained through the low-frequency pass filter (LPF) in FIG. 9, the 10 MHz signal has a large signal-to-noise ratio of 70 dB or more compared to other components, and as a precise signal waveform generator You can see that it works.
１ 入力バルス信号発生回路
２ 直列ジヨセフソン接合アレイ
３ 負荷回路
１０ Ｊｏｓｅｐｈｓｏｎ接合（アレイ）量子化器
１１ ケーブル
１２ 結合コンデンサ
１３、１５ ＬＰＦ
１４ ジョセフソン接合素子
１６ 終端抵抗
２１ ΔΣ変調回路
２２ パルス波畳み込み回路
２３ 高周波Ｄ／Ａ変換器
1 input pulse signal generation circuit 2 series Josephson junction array 3 load circuit 10 Josephson junction (array) quantizer 11 cable 12 coupling capacitors 13, 15 LPF
14 Josephson Junction Element 16 Termination Resistor 21 ΔΣ Modulation Circuit 22 Pulse Wave Convolution Circuit 23 High Frequency D / A Converter
Claims (6)
前記パルス列信号を構成する基本パルスは、時間軸でみて一つの大きな尖頭値を有する波形を有し、且つ前記波形の最大値と最小値の比が大きくなるように構成し、前記パルス列信号は、スペクトル特性が周波数軸でみて出力波形の周波数と重畳しない領域を有し、その領域を画成する二つの周波数ｆ１およびｆ２で規定される幅を持つ信号で置き換えることを特長とするパルス駆動型ジョセフソン波形発生方法。 In a pulse drive type Josephson waveform generation circuit, a signal to be output is input, a pulse train signal is formed based on the signal, and a signal having an arbitrary waveform is generated by the pulse train signal,
The basic pulse constituting the pulse train signal has a waveform having one large peak value on the time axis, and is configured such that the ratio between the maximum value and the minimum value of the waveform is large, and the pulse train signal is The pulse drive type characterized in that the spectrum characteristic has a region that does not overlap with the frequency of the output waveform as seen on the frequency axis, and is replaced with a signal having a width defined by two frequencies f1 and f2 that define the region. Josephson waveform generation method.
A pulse generation circuit; a Josephson junction array quantizer in which a plurality of Josephson junction elements are connected in series; a high-frequency transmission line connecting the pulse generation circuit and the Josephson junction array quantizer; and the Josephson junction array An output circuit for extracting the output of the quantizer through a filter, and the pulse generation circuit inputs waveform data to be output, delta-sigma modulates the waveform data, and a signal frequency spectrum region of the waveform data A delta-sigma modulation circuit for converting to binary pulse train data including a noise frequency spectrum region including a frequency spectrum of an arbitrary multiple of 2 or more of the waveform data, and convolution of the binary pulse train data with a basic pulse waveform, an upper limit frequency and a lower limit frequency. Drive waveform time-series data with noise frequency spectrum domain characteristics consisting of A pulse waveform convolution circuit and a digital-to-analog converter that outputs the drive waveform time-series data as a drive voltage, and the Josephson junction array quantizer includes the drive voltage input via a high-frequency transmission line. Output as the voltage across the junction array of the frequency characteristic having the signal frequency spectrum region and the noise frequency spectrum region, and the frequency spectrum characteristic of the voltage across the Josephson junction array is output only in the signal spectrum region A pulse-driven Josephson waveform generation circuit comprising a low-pass filter for extracting a voltage signal.
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