Patent GB-1427549-A (GB)
Title: Parametron
IPC: H03K19/195
Filed: 1973-05-18
Abstract: 1427549 Superconductive parametric circuits INTERNATIONAL BUSINESS MACHINES CORP 18 May 1973 [30 June 1972] 23716/73 Heading H3X A parametron comprises a Josephson tunneling device which is tuned by a D.C. magnetic field and is pumped at a frequency 2w by an A.C. magnetic field, the resulting parametric oscillation of frequency w having a phase 0 or # determined by the phase of an A.C. signal of frequency w which couples with the device and may itself be derived from a Josephson device. Each Josephson device comprises a base electrode, which may be a ground plane, and a counter electrode, a tunnel barrier being located between the electrodes, Fig. 1 (not shown). Lead or a similar superconducting electrode material is used and an oxide of the base electrode provides a suitable tunnel barrier. The pumping, bias and signal fields are applied by current in adjacently positioned conductors. Interconnected parametrons.-A two-stage system is shown in Fig. 3 in which first and second stages are formed by parametrons P1, P2 and parametron P3, respectively, located on a ground plane 26. The two stages are made operative in sequence with a period of overlap for signal transfer by tuning resulting from sequential activation of either the D.C. bias on lines 32, 34 or the A.C. pumping at frequency 2w on lines 28, 30. When rendered operative, the first stage parametrons P1 and P2 respectively oscillate with a phase determined by the majority phase 0 or # of A.C. signal inputs 54, and this phase is transmitted to parametron P3 by lines 36, 38. The second stage parametron responds to the majority phase of the signals in lines 36, 38 and in an 0 phase reference line, the same signal frequency w being used throughout. Fig. 5 shows constructional details of two coupled stages on a common ground plane 26 used as base electrodes for parametrons P1- P3, each parametron including a tunnel barrier 42, 44 and counter electrodes 46, 48. The parametrons are coupled by a line 36 and are overlaid by insulation 50, 52 supporting pump conductors 28, 30 and bias conductors 32, 34. Superconductive quantum interference parametrons, two Josephson tunneling devices J1, J2, Fig. 6, are coupled together by a superconducting line 56 and ground plane 58. D.C. bias and A.C. pump conductors 64, 66 are adjacently located. In this arrangement no flux can be trapped in the superconductive loop joining the tunnel junctions, with the result that the parametron formed by the paired junctions is not restricted to a pumping frequency of twice the signal frequency. Conversion of D.C. signals to A.C. signals of characteristic phase. Two parametrons P1, P2, Fig. 8, are pumped in common and have respective 0 and # phase A.C. input signals, their outputs being isolated by resistors 77A, 77B. 'For an 0 phase output to obtain at terminal A, parametron P1 is brought into resonance by a D.C. pulse representing a digit 0 applied to a bias conductor 70. Similarly for a # phase output, parametron P2 is brought into resonance by a digit 1 D.C. pulse in bias conductor 72. Conversion of A.C. signals of characteristic phase to D.C. signals. In this case a Josephson junction device J1, Fig. 9, functioning as a resonant circuit but not as a parametron is used, 0 or # phase signal inputs being applied to input lines 78, 80. If both signals are of opposite phase they mutually cancel and the junction remains in a superconductive state. All the current from a D.C. source 84 then passes through the junction and none through a superconductive transmission line 82 terminated by a matching impedance Z 0 . Alternatively if both signals are of the same phase, the device J1 is switched to its resistive state and a pulse from the D.C. source 84 is diverted into the transmission line which may control other Josephson devices such as J2. Signal coupling to Josephson tunneling devices. Capacitive coupling is shown in Fig. 10 in which input lines 78, 80 of a resonant device J1 are spaced by an insulating layer 98, e.g. of SiO, from the counter electrode 96. In this arrangement the characteristic phase signals are developed in the input lines by parametrons P1, P2. Alternatively inductive coupling may be used, Fig. 11, in which a single tunnel barrier 104 is formed in a superconducting loop 106. A control conductor 88 and the input lines are supported by insulation 112 in spaced relationship to the Josephson junction. Interconnection of chips supporting Josephson devices performing memory and logic functions. A plurality of parallel output paths Fig. 13, of first chip circuits 118A are coupled to a similar plurality of input paths of second chip circuits 118B over a common line 120, the parallel paths being segregated in the line by the use of different characterizing frequencies F 1 -F n . Each sending path includes two parametrons Pla and P1b, P2a and P2b... PNa and PNb, the two parametrons in a path being respectively allotted to the digits 0 and 1 from A.C. information circuits A, B ... N and producing respective A.C. outputs of 0 and # phase having a frequency F 1 -F n  characteristic of the path. Each receiving path comprises a parametron P1...PN tuned to respond to the characteristic frequency of that path. Instead of common line 120 the two circuit chips may be capacitively coupled, a capacitor terminating plate being provided on each chip, Fig. 14 (not shown).