Bluetooth is a wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecom vendor Ericsson in 1994, it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems.
Current, the most popular small built-in antenna in mobile phones is the PIFA-type antenna. The PIFA antenna radiator is mounted just above the ground layer, there is PCB plate between the antenna radiation plate and the human brain when using, thus greatly reducing the impact of radiation on the human brain, in addition, PIFA antenna has the advantages the small size, the antenna compact structure is easy to achieve, the appearance grade is not high and antenna production is unanimously good, and so far it is still a mainstream design in the phone built-in antenna on the market. With the further popularization of mobile phones, the user is not limited to the phone’s basic communications functions, but become critical to the appearance of phone and the demand of function. Due to the volume limitations, traditional PIFA antenna solution obviously does not meet the requirements of the antenna RF and also brings greater challenges to the antenna designer.
Design Bluetooth antenna is Inverted F Antenna (IFA) that is a bent monopole antenna, employs a shunt stub for impedance matching. Four parameters variables control the behavior of the structure as shown here.
Feed: The feed is placed from the ground plane to the upper arm of the IFA. The upper arm of the IFA has a length that is roughly a quarter of a wavelength. To the left of the feed , the upper arm is shorted to the ground plane. The feed is closer to the shorting pin than to the open end of the upper arm.
Simulated return of antenna ( using FDTD solver) is shown below . Antenna resonance frequency is 2.4 GHz.
E-Field plot on antenna ( as shown below) shows near field radiation from antenna. This radiation may affect other nearby devices and component in smart phone. EMI/EMC analysis is conducted to cater such kind of radiation.
The polarization of this antenna is vertical, and the radiation pattern is roughly donut shaped, with the axis of the donut in the vertical direction.
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