Patent GB-1227854-A (GB)
IPC: G11C11/20
Filed: 1968-03-12
Abstract: 1,227,854. Parametrically-excited resonators. MELBOURNE, UNIVERSITY OF. 12 March, 1968, No. 11974/68. Heading H3B. A parametrically-excited resonator has a first stable state in which subharmonic oscillation is produced, and a second stable state in which subharmonic oscillation is suppressed, the state in which the resonator operates being dependent on a momentary rise (for the first state) or fall (for the second state) of the A.C. excitation voltage, this voltage normally having a steady value at an intermediate level sufficient to maintain, but not to change, a given stable state. A basic resonator is shown in Fig. 2 and comprises an inductor L, a non-linear capacitance diode D, a by-pass capacitor C for the diode bias voltage B1, B2 and an excitation voltage source G. The excitation voltage is applied across a resistor R, as shown, or through a transformer L 1 , Fig. 3, which also forms the inductor L. A further resonator, Fig. 6, has the excitation voltage applied through a coupling capacitor C 1  to the inductor. This arrangement includes a modulator which temporarily increases or reduces the excitation voltage applied to the resonator in accordance with the polarity of applied information pulses. Operation is shown in Fig. 7 in which the modulator output voltage (the forcing signal) is increased or decreased from a normal intermediate level for the duration of positive or negative information pulses, respectively. Each brief change of forcing signal which is opposite in amplitude to the previous change establishes a new stable condition of subharmonic oscillation, or absence of subharmonic oscillation, as the case may be. As an alternative the bias voltage may be altered to change the stable state, Fig. 10 (not shown). A matrix store is shown in Fig. 8 in which resonators 1, 1 to 2, 2 are capacitatively coupled to row and column lines X 1 , X 2 , Y 1 , Y 2 , all energized by forcing signals. To change the state of a resonator, the amplitude of the forcing signal applied to both the associated lines must be changed, the variation of forcing signal in any one line being itself insufficient to effect a change. In a modification, Fig. 9 (not shown), the resonators are inductively coupled to the lines. An alternative matrix store is shown in Fig. 13, in which a constant voltage forcing signal is applied to all the resonators, and a change of state is produced in a selected resonator by a momentary diode bias change. A positive pulse on a selected row line X 1 -X 2  and a coincident negative pulse on a selected column line Y 1 -Y 3  switches the resonator associated with both lines from the first to the second state. Restoration to the first state is effected by applying two coincident pulses as before but each of the reverse polarity. The state of a resonator is detected either by including subharmonic detectors in the column lines of a matrix, Fig. 14 (not shown), or by monitoring the bias level. A further method is to sample on a line S, Fig. 15, the frequency of the signal gated out (excitation frequency or subharmonic frequency), the gating circuit comprising a gating diode controlled by a pulse applied to a terminal I. As an alternative, Fig. 16 (not shown), the gating diode may be controlled by coincidently pulsing two wires (Ix), (Iy) coupled to the diode. A further read-out arrangement is shown in Fig. 17 in which a read-out parametric resonator H 2  is connected to a storage resonator H 1 , the resonator H 2  producing a subharmonic output in response to appropriate coincidence signals on wires Ix, I Y  in its bias circuit only if the storage resonator H 1  is itself producing a subharmonic output (state 1). Thus the subharmonic output of H 1  is the excitation frequency of H 2 . The use of read-out parametric resonators may be applied to inductive and capacitive coupled matrices, Figs. 18 and 19 (not shown).