The Design Of Directional Antenna For Intelligent Lock Application

As the fast developing of wireless communication, the design of antennas various systems and fields has focused on lots attentions by scientists. To easily use for peole, lock has become more and more intelligent in the recent ten years. The remote control lock has been used in many occasions. The remote control lock were only used in cars and motorcycles because of the high price, and now due to the low costs of production and research it has been applied in rental housing and warehouses, hotels, households, etc. The remote control lock has facilitated our lifes.Firstly, this thesis introduces the surroundings of remote control lock. Secendly, the operation distance in front and back sides for the antenna has been calculated by Friis transmission equation. Finally, according to people’s usage analysis for remote control lock request of antennas, and design three different type antennas as follows:(1)Cavity-backed "L" shaped dipole antenna. When a metal is placed too near to the antenna, the cavity model theory can explain the impact of the antennas radiation. To reduce the size of the metal at the antenna we folded two arms of the dipole antenna. Good performances on return loss, radiation pattern are obtained over 2.4GHz operating bands, and the antenna achieves unidirectional radiation.(2)MIMO patch antennas. Technology of MIMO will be applied to the remote control lock. The use of two of the same size and same position in patch antenna are placed the front and the rear two the iron cavity of the lock. The MIMO antennas solve the problem of multipath effect occurred in a single dipole antenna during propagation.Good performances on return loss, radiation pattern are obviously seen from the simulation results. Beside, the isolation between the two patch antennas reached-60 dB at the center frequency. The high isolation ensures antenna can work alone without the influences from the other.(3)Circularly polarized MIMO antennas. To solve the problem of the linear polarization dipole antenna radiation is not comprehensive range, using the circularly polarized(CP) MIMO antennas can receive the remote singal wherever the direction of remote whe n the remote in the range of radiation,because of the CP antenna can receive any polarized electromagnetic wave. Cutting triangle off at the corners of the patch antennas and slotting a rectangle in the middle of antenna is two ways to achieve circular polarization. CP MIMO antennas also received high isolation. The former way can obtain the good bandwidth of axial ratio on several frequencies,the later way achieved axial ratio less then 3dB in a large angular range.