Hac Antenna Module Study

Mobile communications business has experienced enormous growth in recent years. Located at the radio front of the portable phone, the antenna is mainly responsible for receiving and transmitting eletromagnetic wave. With the introduction of digital cellular-phones, hearing-aid users have complained they experienced a severe buzzing noise caused by the interaction between digital cellular phones and hearing aids. The mobile phone manufacturers, network service providers, hearing aid manufacturers and certain related organizations have been seeking a solution for the interference issue. American National Standards Institute established new laws and regulations for Hearing Aid Compatibility.The compatibility problem of Wireless devices and hearing aid has also become a new research topic.In this dissertation , we focus on the causes of the interference and an understanding of the problem. We also present a method to reduce near-field electromagnetic energy around a cellular phone, mitigating the interference between cellular phones and hearing aids. The theoretical investigation of both the radiation mechanisms and fundamental limits on small-electric antennas suggested that a dipole antenna, such as a half-wave dipole antenna, could add a metal shield to reduce the near-field.The present dissertation relates to antenna module designs and more particularly, to a multi-band HAC compatible antenna module, which has a metal shield mounted therein around the built-in antenna for resonant coupling with the antenna to lower electromagnetic interference and to provide HAC characteristic. It is one object of the present antenna to provide a multi-band HAC compatible antenna module, which is mounted with a metal shield to provide excellent HAC characteristic, showing 3dB-4dB HAC improvement in GSM850 and GSM900, and 1dB HAC improvement in DCS and PCS bands. When compared with a reference antenna without metal shield.Finally, the dissertation also provides anthor antenna design solutions. A special hearing aid-compatible handset antenna which has dual-patch and double-layer structure is placeed at the bottom of phone. When compared with a reference PIFA antenna at the same place, the special antenna approach to reduce the near-field strength was demonstrated through both simulations and measurements. Simulations showed that the peak electric and magnetic near-field amplitudes were respectively 3.5dBV/m and 4.3dBA/m lower for the present antenna compared to a normal PIFA antenna in PCS band (1850MHz-1990MHz).The research work presented in this dissertation provides an effective solution for a hearing aid compatible handset antenna, particularly for Bar-type Phone, as well as an efficient method for analyzing near-field of handset antennas...