Quadrature amplitude modulator using switched capacitor filter
US4777453A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 1, 1987 |
| Grant date | Oct 11, 1988 |
| Priority date | — |
| Expiry date | May 1, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/36
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A switched capacitor circuit implements a base band, finite impulse response filter (BBF) and balanced modulator with a single operational amplifier. The analog modulator has particular application in voice band modem applications and requires little or no microprocessor code space. Simplified sine and cosine functions are implemented in a pair of base band filters such that the output of only one base band filter is required at any one time. In this manner, a single operational amplifier may be utilized to implement the analog modulator/base band filter of the present invention. The use of switched capacitor technology and a single operational amplifier results in less silicon area dedicated to the analog modulator than for corresponding digital modulators.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.