Modulators – Amplitude modulator – Nonlinear device controlled by modulating signal
Patent
1982-06-28
1985-04-09
LaRoche, Eugene R.
Modulators
Amplitude modulator
Nonlinear device controlled by modulating signal
332 9R, 332 45, 332 48, 329163, 329192, H03K 102, H03K 700
Patent
active
045104670
ABSTRACT:
An integrated single-sideband modulator comprises six integrated capacitors C1-C6 and first switch means alternately connecting C1 and C2 as feedback capacitors across a differential input operational amplifier A1. The amplifier has a virtual ground potential on its inverting input terminal for causing it to operate as a voltage source and render the circuit relatively insensitive to parasitic capacitance effects associated with capacitor plates. Second switch means cooperates with A1, C1 and C2 and is responsive to 4-phase clock signals for driving input capacitors C3-C6 so as to convert first and second quadrature-phase input signal voltages into first and second electrical charge flow signals on the inverting input terminal that are a function of products of representations of the first and second voltages in switch state time intervals and associated pulse trains which have a 90.degree. phase difference therebetween and a repetitive pattern such as +1, +1, -1, -1, etc. The amplifier and feedback capacitors combine the charge signals for producing a single-sideband signal on A1's output terminal. This circuit is converted to a balanced modulator by omitting C5 and C6. In an alternate embodiment of a single sideband modulator that requires only a pair of switched capacitors C11 and C12, a 4-phase switch means alternately charges C11 and C12 with associated ones of the quadrature-phase input signal voltages while alternately connecting C12 and C11 as feedback capacitors across A1, the polarity of each capacitors feedback voltage being reversed each time that capacitor is connected across the amplifier. This circuit is operated as a balanced modulator by omitting one of the capacitors.
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 Xactions on Circuits And Systems, vol. CA-S-28, No. 6, Jun. 81, pp. 576-584.
Zamorrodi, 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 Communications Systems" McGraw Hill Book Co., 1971, pp. 102-104.
Chang Chieh
Lee Man S.
Cannon Russell A.
GTE Communication Systems Corporation
LaRoche Eugene R.
Mis D. C.
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