| 摘要 |
1,124,275. Frequency discriminators. RADIO CORPORATION OF AMERICA. 24 Aug., 1965 [14 Sept., 1964], No. 36410/65. Heading H3A. [Also in Division H1] A frequency discriminator may include an integrated circuit chip 10 wherein the capacitors 68, 70 and 72 are reverse-biased diodes, and is characterized in that the time constant of load resistances 54 and 56 with capacitors 68 and 70 is of the same order as the period of the carrier wave. The short time constant reduces the harmonic content and reduces the load on transformer 36, as a result of which the waveform at the transformer is more nearly a sine wave. The load on the transformer may be further reduced by including further rectifiers 100 and 102 between rectifiers 50 and 52 and their associated load resistances, Fig. 5 (not shown). The capacitance in the discriminator load circuit may be increased by connecting two further diodes 90 and 92, Fig. 3 (not shown) in parallel with 68 and 70, the cathodes of these diodes being connected respectively to earth and to a positive 2 volt supply. The capacitance of diodes 90 and 92 is nearly twice that of diodes 68 and 70 due to the additional capacitance between their cathodes and the substrate of the integrated circuit. The similarly poled diodes 68 and 70 of Fig. 1 may be replaced by oppositely poled diodes 96 and 98, Fig. 4 (not shown). One of the diodes 98 then exhibits increased capacitance, for equal junction areas, and the junction areas are varied to compensate for this and for the different capacitances to earth exhibited by the anode of rectifier 50 and the cathode of rectifier 52. The method of construction of the integrated circuit is similar to that described in Specification 1,124,274. |
