Integrated electric filter with adjustable RC parameters
US4785253A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 21, 1987 |
| Grant date | Nov 15, 1988 |
| Priority date | — |
| Expiry date | Apr 21, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03J3/24
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An integrated electrical filter includes resistors (R10-12) and capacitors (C10-12). The capacitors are controllable in value by means of a control circuit (100-109) and are formed by a binary weighted array of capacitor elements which are selectively connectable in parallel. A controlled oscillator (103) or a controlled phase shifting network (113) includes a capacitor of the same form as the filter capacitors. The oscillator (103) or phase shifter (113) form part of a phase locked loop (101, 104, 105, 107) which produces a digital code as its control signal at the output of an up/down counter (107). This digital code is latched in a register (109) to provide a control signal for the filter capacitors and also is used directly to control the capacitor(s) in the controlled oscillator or phase shifter.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.