Modulators – Amplitude modulator – Nonlinear device controlled by modulating signal
Patent
1982-06-28
1985-03-26
LaRoche, Eugene R.
Modulators
Amplitude modulator
Nonlinear device controlled by modulating signal
332 9R, 332 45, 332 48, 329163, 329192, H03C 102, H03K 700
Patent
active
045076251
ABSTRACT:
A first embodiment of an integrable switched capacitor modulator comprises a differential input operational amplifier A1 having a virtual ground potential impressed on its inverting input terminal; capacitors C1, C2 and C3; and switch means operative for alternately (1) charging C1 with an input voltage while connecting C2 and C3 in series with A1 and across it, respectively, for causing it to produce an inverted version of the input voltage, and (2) discharging C2 and C3 while connecting the sample of the input voltage on C1 across A1 for causing it to output a non-inverted sample of the input voltage. The modulated output signal from A1 is preferably bandpass filtered to eliminate baseband spectral components fed through A1 when C2 is connected in series with the input terminal thereof. In a second embodiment which is insensitive to feedthrough and which requires only two capacitors C1 and C4, the switch means alternately (1) charges C1 with the input voltage while connecting a prior sample of the input voltage on C4 across A1 for causing it to output an inverted sample of the input voltage, and (2) charges C4 with the input signal while connecting the sample of the input voltage on C1across A1 in the opposite polarity for causing it to output a non-inverted sample of the input voltage. This embodiment has particular advantage as a demodulator since the built-in sample-and-hold function provides low pass filtering of the output signal of A1.
REFERENCES:
patent: 3482174 (1969-12-01), James
patent: 3944852 (1976-03-01), Gilbert
patent: 4375625 (1983-03-01), Lee
Martin K., "Switched Capacitor Building Blocks for Adaptive Systems", IEEE Transactions on Circuits and Systems, vol. CAS-S-28, No. 6, Jun. 1981, pp. 576-584.
Zomorrodi, M., "Switched Capacitor Quadrature N-Path Filters", Midwest Symposium on Circuits and Systems, Jun. 1981, pp. 682-686.
Chang C. et al., "Switched Capacitor Modem for Amplitude Modulation", IEEE International Symposium on Circuits and Systems Proceedings Rome, Italy, May 10, 1982, pp. 557-560.
Taub, H. et al., Principles of Communication Systems, McGraw Hill Book Co. 1971, pp. 102-104.
Chang Chieh
Lee Man S.
Cannon Russell A.
GTE Communications Systems Corporation
LaRoche Eugene R.
Mis D. C.
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