| Bluetooth technology is a short-range wireless communication,and it is widely used in the consumer electronics market.Usually the communication system of the Bluetooth headset is composed of antenna,alink control,link management and Bluetooth protocol stack,the antenna is important in the system.The operating frequency and efficiency of the Bluetooth antenna are related to its physical size,large antenna is not suitable in limited physical space.Therefore,Research on small size of Bluetooth antenna has important Practical value.This paper proposes one of design and application method for a small antenna of Bluetooth headsets.Firstly,based on the related principles of electromagnetic field and microstrip antenna,a small antenna was designed by using HFSS simulation software.Secondly,the printed antenna is used in the design and production of a Bluetooth headset hardware system.Finally,the antenna impedance of the Bluetooth headset is debugged,and the performance of the antenna is tested.The performance of the antenna technology is found to meet the basic requirements of Bluetooth technology design in terms of antenna input impedance,bandwidth,standing wave ratio,antenna efficiency,gain,polarization direction and measured distance,etc.Some performance is optimized.The main research work of this paper includes:1)On the design of the printed antenna and the back-end simulation data,the Bluetooth headset structure was properly modeled using the HFSS simulation software.After adjusting and optimizing the parameters of the printed antenna width,spacing,grounding,length,etc.,a small-sized antenna with good performance is designed in a meandering manner.The back-end simulation data shows that the designed antenna has many ideal parameter values required by Bluetooth technology.For example,S11 is-23 d B when the center frequency is 2.44 GHz,the antenna input impedance is close to 50 ohm,the bandwidth is 78 MHz,and the antenna gain is 1.38 d Bi,efficiency is 80%,radiation direction is closed to omnidirectional,etc,there is asmaller size than conventional PIFA antennas.2)In the hardware design of the Bluetooth headset,firstly,the schematic diagram of the Bluetooth headset is designed.Then the PADS Layout software is used to design the circuit board,in the same time,the RF transmission line parameters are calculated by the Si9000 tool,the designed printed antennas is integrated,the design and production of a Bluetooth headset hardware system was completed.3)In the debugging and analysis of the antenna performance,based on the representation of the Smith chart,the variation law of the matcher in the Smith chart is summarized.Then,the vector network analyzer was used to perform impedance matching debugging and testing on the antenna part of the hardware system,and the antenna radiation effect was tested in the dark wave laboratory.The printed antenna has a S11 value of-29 d B at a Bluetooth center frequency of 2440 MHz,a bandwidth of 150 MHz,a maximum gain of-0.78 d Bi,a maximum efficiency of 39.5%,and a forward distance of 15.2m for the whole machine,which meets the performance requirements of a small-structure Bluetooth earphone antenna.Finally,compared with the ceramic antenna prototype that has been produced,the S11 value is-10.5d B at2440 MHz,the bandwidth is 50 MHz,the maximum gain is 0.19 d Bi,the maximum efficiency is 24.3%,and the forward distance of the whole machine is 10.4m.Test results show that the printed antenna has improved a lot in performance.Finally,the small antenna designed for a Bluetooth headset has the following advantages:(1)The physical size of the printed antenna is relatively small,suitable for small structures.(2)The antenna is printed on the circuit board,and no additional cost is required,and the mounting process is omitted.(3)The overall performance of the antenna is not bad,and meets Bluetooth headset antenna requirements. |
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