| Antenna is an important part of the wireless communication system.Related design techniques to improve the performance of antennas have also been proposed and improved with the rapid development of communication systems.Microstrip antennas are widely used in portable wireless communication systems because of the low profile,light weight,low cost and easy to process and integrate with system.Many communication systems use wideband antennas or two independent antennas to meet the receiving and transmitting frequency and bandwidth.Broadband antennas can generate interference frequencies,while dual antennas will increase the cost of antennas.These problems can be solved by dual-frequency antenna technology,which can not only improve the utilization rate of spectrum resources,but also ensure the working efficiency of the antenna.Based on the relevant researches and discussions on the miniaturized dual-frequency microstrip antenna,three miniaturized dual-frequency antennas applied in different fields are designed and realized by HFSS software in this thesis.The specific research contents are as follows:The first antenna's radiating unit uses a split ring resonators structure to achieve miniaturization of the antenna.At the same time,a rectangular parasitic patch is loaded on the back of the dielectric substrate to achieve the dual-frequency characteristics of the antenna.The corresponding capacitive reactance is introduced at the input impedance of the antenna by etching one U-shaped slotline on the feed line,which resonates with the inductive reactance at the feed line.Finally,a new resonant frequency is generated and expands the bandwidth of the antenna.The measured results demonstrate that the proposed antenna can operate from 5.8 to 11.0 GHz and 14.5 to21.5 GHz with the maximum gain of 4.23 dBi.Good agreement between the measured results and the simulated ones are observed.The total antenna size is 0.69?0×0.55?0×0.02?0(?0 is the free space wavelength at 8.4 GHz).The antenna can work in ultra-wideband and Ku-band.The second antenna radiating unit consists of two microstrip lines of different lengths and a rectangular patch.The curved and long branch microstrip line generates a frequency point of 2.4 GHz.while the short branch microstrip line generates a frequency point of 5.5 GHz.The coupling between the rectangular patch and the microstrip line improves the impedance matching performance of the high frequency resonance point.The actual measurement results show that the antenna's low-frequency operating frequency range is 2.47-2.53 GHz,and the maximum low-frequency gain is1.12 dBi;the high-frequency operating frequency range is 5.16-6.66 GHz,and the high-frequency maximum gain is 3.42 dBi;The compact physical size of the antenna is0.23?0×0.21?0×0.01?0(?0 is the free space wavelength at 2.5 GHz).The antenna can effectively work in the WLAN band.The third antenna achieved a dual-frequency effect by adding a rectangular patch and an L-shaped patch to one side of the ground,and at the same time,a rectangular slot was etched on the antenna radiating unit to improve the return loss of the antenna at high-frequency.The actual measurement results demonstrate that the antenna can effectively work in two frequency bands of 3.0-4.85 GHz and 6.4-6.83 GHz.The maximum gain of the antenna in the low-frequency band is 2.74 dBi,and the maximum gain of the high-frequency band is 4.19 dBi.The overall antenna size is 0.35?0×0.32?0×0.01?0(?0 is the free space wavelength at 3.92 GHz),which can be effectively used in the WiMAX band. |
PDF Full Text Request