Apparatus and method for reducing magnetic fields in radio telephones
US5960346A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 3, 1997 |
| Grant date | Sep 28, 1999 |
| Priority date | — |
| Expiry date | Apr 3, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R2499/11
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A novel method and apparatus are described for reducing the effect that magnetic field emissions from a radio telephone may have on devices sensitive to time-varying magnetic fields. The variance of the magnetic field is smoothed by the addition of a smoothing capacitor having a time constant significantly longer than the TDMA time frame which is connected in parallel with the transmitter. In addition, a counter-balancing magnetic field is generated by a field canceling loop connected in series with the transmitter which causes current to flow in a path approximately opposite from the path the current flows through the battery, in roughly parallel plane. The current flowing through the field canceling loop generates a magnetic field approximately coaxial with, and opposite in polarity from, the magnetic field generated by current flowing through the battery, partially negating the latter. Utilization of the method and apparatus result in a reduction in the effective magnitude of the time-varying magnetic field outside the telephone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.