Electrical transmission or interconnection systems – Nonlinear reactor systems – Parametrons
Patent
1992-06-05
1994-02-22
Sikes, William L.
Electrical transmission or interconnection systems
Nonlinear reactor systems
Parametrons
307271, 328 15, 328167, H03B 500
Patent
active
052890597
ABSTRACT:
A switched capacitor decimator circuit (20) is shown to be useful in a cellular telephone that operates in accordance with a subaudible signalling protocol. The switched capacitor decimator circuit has an input node for inputting a received signal that includes a subaudible signalling component and an interfering voice component. The switched capacitor decimator circuit further has an output node for outputting a signal having an amplified subaudible signalling component and voice component. The circuit includes an operational amplifier (22) having an input and an output and a characteristic DC offset voltage. A first capacitance (Cint) is switchably coupled, at a rate equal to a first frequency, between the input and the output of the operational amplifier. A second capacitance (Cin) is coupled between the input node and the input of the operational amplifier. A gain (G) of the circuit is given by Ncin/Cint, where n is a ratio of the first frequency to a second, lower frequency. The circuit further includes circuitry (C3, C4) for DC offset compensating the switched capacitor decimator circuit such that the DC offset voltage of the operational amplifier appears at the output node amplified only with a gain of unity.
REFERENCES:
patent: 4331894 (1982-05-01), Gregorian et al.
patent: 4754226 (1988-06-01), Lusignan et al.
patent: 4841263 (1989-06-01), Mulawka et al.
patent: 4894620 (1990-01-01), Nagaraj
"Integrated Switched-Capacitor Low-Pass Filter with Combined Anti-Aliasing Decimation Filter for Low Frequencies", IEEE J. Solid-State Circuits, vol. 17, pp. 1024-1028, Dec. 1982, D. von Grunigen et al.
"Improved Offset-Compensation Schemes for Switched-Capacitor Circuits", K. Haug et al., ISCAS 1984, pp. 1054-1057.
"Spike-Free Switched-Capacitor Circuits" by Matsumoto et al., Electronics Letters 9th, vol. 23, No. 8, (Apr. 1987).
Robert Gregorian et al., "Switched-Capacitor Circuit Design", Proceedings of IEEE, vol. 71, No. 8, Aug. 1983, pp. 941-966.
Nokia Mobile Phones Ltd.
Riley Shawn
Sikes William L.
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