GB1170353A - Angle-Modulated Wave Demodulating System - Google Patents

Abstract

1,170,353. Frequency discriminators. RADIO CORPORATION OF AMERICA. 22 Feb., 1967 [28 Feb., 1966], No. 8585/67. Heading H3A. A frequency discriminator of the type described in Specification 1,124,275 and suitable for construction as an integrated circuit chip 10, is characterized in that means are provided for maintaining the output potential at the junction of resistances 54 and 56 at the same potential as the tertiary winding 44 of the discriminator transformer under zero signal conditions. In Fig. 1 the junction is connected by a resistance 80 to terminal 76 which is connected to the same + 2 volt supply as winding 44. In a modification, Fig. 3 (not shown), this resistance (86) has a variable tapping connected to the output circuit and forming a volume control. In another modification, Fig. 4 (not shown), the terminal 46 is connected to a feedback voltage from the audio output stage instead of to the + 2 volt supply. In a further modification, Fig. 5 (not shown), the + 2 volt supply is connected to the junction of resistances 54 and 56, and the junction of winding 44 with resistance 80 (96 in Fig. 5) is connected to the base of the output transistor. In another modification, Fig. 6 (not shown), resistances 54 and 56 are connected by equal resistances to a 4-volt supply and to earth respectively, the winding 44 supplying the output to transistor 58. In another arrangement, Fig. 7 (not shown), the rectifiers 50 and 52 are shunted by parallel resistances, and in a further arrangement, Fig. 8 (not shown), the junction of resistances 54 and 56 is connected to the + 2 volt supply, and the junction of a further pair of resistances (104 and 106) in parallel with resistances 54 and 56 is connected to the base of transistor 58.