1. Field of the Invention
This invention relates to a method and apparatus for summing the products of samples of analog signals, to discrete analog signal processing (DASP) systems and, more particularly, to systems employing CCD devices configured for implementing a real-time, fully-analog correlator or convolver.
2. State of the Prior Art
Matrix multiplication of analog signals and, in particular, analog signal correlation, for example, has been performed by such techniques as converting the analog signals to digital signals and performing digital multiplication or correlation. However, such A/D conversion techniques require large amounts of hardware which uses relatively large amounts of space and decreases system reliability.
It is desirable, therefore, to devise a method and apparatus for analog signal matrix multiplication or correlation which does not include A/D conversion.
An application, concurrently filed herewith, and entitled "CMOS Analog Multiplier for CCD Signal Processing" of Lampe, et al., is of interest for its disclosure of a balanced differential conductance-type MOS transistor multiplier using complementary MOS transistors.
Also of interest is U.S. Pat. No. 4,035,329 by Lampe, et al., assigned to the common assignee which discloses an extended correlated doubling sampling system which corrects for errors in components of the system.
Application Ser. No. 625,696, filed Oct. 29, 1975, entitled "A Dual-CCD Real Time, Fully-Analog Correlator", by Lampe, et al., is of interest for its disclosure of a general-purpose fully analog correlator including two CCD channels for processing samples of analog signals and MOSFET multipliers for providing products of the signal samples.