Design Of Compact Antenna And MIMO Antenna For Mobile Terminal

In recent years,the industry of intelligent mobile terminal has developed rapidly,and the functions of handheld mobile terminal increased more.As a result,the space provided for antenna inside the terminal becomes smaller,and the difficulty in antenna design increases.However,the reduction of the antenna size will lead to the varations of some parameters,for example,the bandwidth of the antenna will become narrow.Therefore,design of compact broadband mobile terminal antenna for different frequency bands is of great practical significance.At the same time,in order to meet the requirements of the faster communciation rate,the MIMO system is proposed,which can be formed by disposing multiple antennas in the transmitter and receiver,respectively.The MIMO system can reduce the error rate and increase the channel capacity.Based on the background,three compact antennas for different frequency bands are proposed in the thesis,and two of them are MIMO antennas.The main research contents of the thesis include:1.Compact LTE/WWAN octa-band antenna for handheld mobile terminal.The antenna is composed of a driven branch,a shorting branch and a band-stop matching circuit.By capacitive coupling,embedding a lumped inductor in the shorting branch,and loading a matching circuit,the design of compact broadband antenna is realized,and the size of the antenna is 28.7×12.5 mm~2.The quarter-wave resonant mode of the shorting branch and the resonant mode of the antenna under the action of the matching circuit work together to form a dual-resonance for covering the bands of LTE700/GSM850/900.The quarter-wave resonant mode generated by the driven branch and the higher order resonant mode of the shorting branch also work together to cover the bands of DCS/PCS/UMTS/LTE2300/2500.The measured results show that the-6 dB impedance bandwidth of the antenna can cover the bands of 698-960 MHz and 1710-2690 MHz.The parameters such as the radiation pattern,efficiency and gain also meet the actual requirements.2.10-antenna array for sub-6 GHz MIMO applications.The antenna element is a microstripline-fed T-shaped open-slot antenna,which generates two resonant modes at around 3500 MHz and 5600 MHz.The T-shaped microstrip can adjust the impedance matching and broaden the bandwidth.The methods for improving the isolation of the MIMO antenna are space diversity and polarization diversity.The measured results show that the-6 dB impedance bandwidth of each antenna element can cover the bands of3300-3800 MHz and 4800-5925 MHz,and the isolation between the two adjacent elements is higher than 11 dB.The parameters such as the radiation pattern,efficiency,gain and ECC also meet the actual requirements.3.Dual-element MIMO antenna with high isolation for 2.4/5-GHz WLAN applications.To realize the design of compact broadband antenna,each antenna element adopts the coupled-fed structure so as.The resonant mode generated by the shorting branch in the lower band is used for covering the 2.4-GHz WLAN band.The resonant mode generated by the driven branch and the resonant mode generated by the shorting branch in the upper band work together to cover the 5-GHz WLAN band.To improve the isolation of the MIMO antenna,a hybrid decoupling structure is disposed between the two antenna elements,which includes a protruded ground branch for the 2.4-GHz WLAN band and a narrow slot etched on the ground for the 5-GHz WLAN band.In addition,to reduce the dimension of the protruded ground,two 8.2-nH lumped inductors are embedded in the branches of the protruded ground.The measured results show that the-10 dB impedance bandwidth of the MIMO can cover the bands of 2400-2484 MHz and 5150-5850 MHz,and the isolation between the two antenna elements is higher than 20 dB.The parameters such as the radiation pattern,efficiency,gain and ECC also meet the actual requirements.