Research On Broadband Loaded Antenna

With the rapid developments of wireless communication technology,the technical requirements for antennas,which are an important part of a communication system,are getting higher and higher.At present,the antennas in the wireless communications are becoming increasingly broadband and miniaturized.In a practical application,the parameters of traditional antennas are often difficult to meet the application requirements.Resistance loading is widely used in antenna design as a means to achieve antenna miniaturization and broaden antenna bandwidth.Monopole antennas are widely used due to their omni-directional radiation,simple structure,and easy installation.However,as the operating frequency decreases,the size of the monopole antenna should also increase,which greatly limits its application.It is of great significance to apply resistance loading technology to the design of monopole antenna and to design broadband monopole antenna with small size.(1)A planar rectangular monopole antenna is proposed.A wide impedance bandwidth is achieved by using the grounding resistance loading circuit,the unloaded prototype antenna operates from 6.95 GHz to 10.85 GHz,with a relative bandwidth of 43 %.After resistance loading,the working frequency is 2.8 GHz to 15.7 GHz,and the horizontal radiation omni-directionality is good.In this operating frequency band,the radiation efficiency is greater than 10%,and the validity of the loading method is verified by physical test.The size of the antenna is very small,the total size is 25 mm × 21 mm,which is convenient for application in various equipment.(2)An ungrounded loop resistor loaded monopole antenna is proposed,which solves the problem of low radiation efficiency caused by grounded load resistance,extending the operating frequency of U-shaped microstrip monopole antenna from 2.87 GHz-4.39 GHz(relative bandwidth 41.8%)to 2.6 GHz-17.84 GHz.The physical test verifies the effectiveness of the technical scheme,and the antenna radiation efficiency is greater than 60 % in the whole working frequency.(3)Based on the single-side loop loaded U-shaped planar monopole antenna structure,a double-side loop loaded antenna is designed,and the working bandwidth is extended to 2.74 GHz to 19.12 GHz.At the same time,the principle of current radiation cancellation in the double-side loop is used to improve the high frequency gain of more than 8 GHz.In the frequency band with extremely low gain at 11.5 GHz,the gain increases from 1.1 dBi to 2.7dBi.The three resistive loaded monopole antennas designed in this thesis are all planar structures,which are convenient for integration with the system.By using the resistance loading method,the three antennas are all broadbandized,and the problem that the radiation efficiency of the resistance loading antenna drops too fast is solved.Compared with the working frequency,the miniaturization is realized.