METHODS FOR REDUCING NEAR-FIELD RADIATION AND SPECIFIC ABSORPTION RATE (SAR) VALUES IN COMMUNICATIONS DEVICES

摘要

A method is provided for reducing near-field radiation and specific absorption rate (SAR) values in a communications device. The communications device includes a multimode antenna structure transmitting and receiving electromagnetic signals and circuitry for processing signals communicated to and from the antenna structure. The antenna structure includes: a plurality of antenna ports operatively coupled to the circuitry; a plurality of antenna elements, each operatively coupled to a different one of the antenna ports; and one or more connecting elements electrically connecting the antenna elements at a location on each antenna element that is spaced apart from an antenna port coupled thereto to form a single radiating structure and such that electrical currents on one antenna element flow to a connected neighboring antenna element and generally bypass the antenna port coupled to the neighboring antenna element, the electrical currents flowing through the one antenna element and the neighboring antenna element being generally equal in magnitude, such that an antenna mode excited by one antenna port is generally electrically isolated from a mode excited by another antenna port at a given desired signal frequency range and the antenna structure generates diverse antenna patterns. The method includes adjusting the relative phase between signals fed to neighboring antenna ports of the antenna structure such that a signal fed to the one antenna port has a different phase than a signal fed to the neighboring antenna port to provide antenna pattern control and to increase gain in a selected direction toward a receive point. The method features using a transmit power lower than the transmit power used in a non-pattern control operation of the antenna structure such that the communications device obtains generally equivalent wireless link performance with the receive point using reduced transmit power compared to the non- pattern control operation, thereby reducing the specific absorption rate.