Patent GB-1191131-A (GB)
Title: Electrical Circuit Including an Active Element Consisting of a Non-Linear Reactance Element Exhibiting Hysteresis
IPC: H03C5/00
Filed: 1967-04-24
Abstract: 1,191,131. Magnetic and dielectric amplifiers; semi-conductor circuits. HITACHI SEISAKUSHO K.K. 24 April, 1967 [27 April, 1966], No. 18681/67. Headings H3B and H3T. [Also in Divisions G3 and H1] A dielectric or magnetic amplifier or second harmonic modulator has its respective ferroelectric or ferromagnetic material maintained substantially at the Curie temperature by an R.F. heating circuit forming part of the regenerative feedback circuit of an oscillator. Dielectric modulators.-A D.C. or lowfrequency A.C. signal is applied to a heated ferroelectric. capacitor 1 through terminals 2, 3, Fig. 3, and a carrier frequency at terminals 5, 6 is applied in parallel to the same capacitor through a transformer 7 and decoupling capacitor 11. The output signal is obtained at terminals 9, 10 after passing through a decoupling capacitor 12 and a band-pass filter 8 which suppresses the carrier frequency and passes the second harmonic. A residual output due to an offset dielectric flux density/electric field characteristic, Fig. 4b (not shown), is removed by the arrangement shown in Fig. 5a, in which two heated ferroelectric capacitors 15, 16 together with the two parts of a centretapped transformer secondary winding 17 form a bridge circuit, the carrier frequency being applied to the primary winding 18. In a modification, Fig. 5b (not shown), the transformer secondary winding is replaced by two impedances (17), (17a) and the carrier frequency is applied directly to the bridge points 19, 20 shown in Fig. 5a. Dielectric amplifiers.-Heated ferroelectric capacitors 68, Fig. 10a, are connected in series with an A.C. source 69 and a load 70, and are biased by a D.C. source 71 which is connected in series with signal input terminals 72. Decoupling coils 73 are provided. The load may be connected through a bridge rectifier, Fig. 10b (not shown). Magnetic modulators-A carrier frequency source 63, Fig. 9, is coupled to output terminals 66 through windings 60, 62 on a heated ferromagnetic core 59 and an even harmonic band pass filter 64. A D.C. or low-frequency A.C. modulating signal is applied to a winding 61. Magnetic amplifiers.-Decoupled load and control windings 78, 79, Fig. 11, are carried by two heated cores 81, 82. Heating arrangement.-Additional electrodes are provided in the ferroelectric capacitor which are connected to the high-frequency output of an oscillator, Fig. 8, so that dielectric heating is produced. For a ferromagnetic or antiferromagnetic core, heating is effected by radiofrequency energization of an additional winding. As shown, a heated ferroelectric capacitor 40 has its additional electrodes connected in a bridge circuit 35 forming part of the feedback circuit of an oscillator having transistor amplifying stages 44, 45. The other arms of the bridge circuit consist of the centre-tapped secondary winding 42 of a coupling transformer 43 and a capacitor 41. The arrangement is self-regulating, the temperature-and therefore the electrical properties-of the ferroelectric material determining the degree of feedback to the amplifying stages and thus the oscillator output. Ferroelectric capacitor construction.-The dielectric may comprise a sheet of-triglycine sulphate 22, Fig. 6a, prepared by cleaving and with a plurality of electrode pairs 23, 23a forming separate capacitors interconnected as shown for use in the Fig. 5a and Fig. 5b (not shown) embodiments. An alternative connection arrangement is disclosed, Fig. 6b (not shown), which minimizes noise in the external circuit. A further electrode pair is provided for heating of the dielectric, Fig. 7b, the capacitor assembly consisting of an electrode assembly on each of opposite faces of the dielectric 37 formed by an outer heating electrode 38 and inner electrodes 39 defining the two ferroelectric capacitors.