Active polyphase filter with transconductor cross-coupling of filter sections
US6441682B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 22, 2000 |
| Grant date | Aug 27, 2002 |
| Priority date | — |
| Expiry date | Nov 22, 2020 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H2011/0494
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The invention is an improved implementation of an active-RC polyphase band-pass filter with transconductor cross-coupling between filter sections. The polyphase filter has first to fourth inputs, first to fourth outputs, two filter sections, and a block of transconductor pairs. The four input signals to the polyphase filter succeed one another in phase by 90 degrees. The two filter sections have reactances comprised of active balanced operational amplifiers with matched capacitors in their feedback loops. The block of transconductor pairs is coupled between corresponding reactances of each filter. The transconductance of each transconductor pair is set as the product of a desired radian center frequency and the capacitance of the corresponding matched capacitors. In the preferred embodiment, the transconductors are Gm cells and the transconductance of at least one Gm cell is field adjustable. The filter sections of the preferred embodiment can be a pair of low-pass third-order active-RC gaussian filters or a pair of low-pass sixth-order active-RC gaussian filters.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.