Balanced bridge saw filter
US5508667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 26, 1994 |
| Grant date | Apr 16, 1996 |
| Priority date | — |
| Expiry date | Jul 26, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03H9/6426
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The invention relates to a SAW filter comprising a first and second pair of substantially equivalent SAW transducers electrically coupled to form a bridge circuit. Each of the transducers of the first pair of transducers have a center frequency which is slightly different to the center frequency of each of the transducers of the second pair of transducers. The product of the static capacitance of the first pair is the same as the product of the static capacitance of the second pair. In use, signals input to the filter and having a frequency within the passband of the filter are coupled to the output of the bridge circuit via one or other or both arms of the bridge, as in normal bridge circuit operation. However, out of band signals are blocked since all the transducers are equivalent capacitors having the same capacitance (i.e., static capacitance). Thus, transmission of out of band signals through the filter is inhibited by the balanced nature of the bridge.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.