Transmit and receive loop antenna
US5602556A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 7, 1995 |
| Grant date | Feb 11, 1997 |
| Priority date | — |
| Expiry date | Jun 7, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01Q21/29
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A transmit and receive loop antenna includes a first loop element coupled to an electrical circuit element for generating near fields and far fields and a shunt loop element surrounding the first loop element such that voltages are induced in the shunt loop element by the fields generated by the first loop element. The shunt loop element is constructed from a continuous loop of conductor to maximize current from the voltages induced in the shunt loop element. The current in the shunt loop element generates fields which largely cancel the fields generated by the first loop element in the far field. Thus, the first loop element and the shunt loop element establish a surveillance zone in an area proximate the loop elements. A second loop element, such as a figure-8 loop element may be placed proximate the first loop element and the shunt loop element for receiving electromagnetic energy radiated by a tag circuit which enters the surveillance zone. The tag circuit inside the surveillance zone may be powered by the emitted electromagnetic field of the first loop element and the shunt loop element.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.