Design Of The TD-LTE RF Front-end Antenna And Filter And Low Noise Amplifier

With the rapid development of mobile communication technology,the fourth generation mobile communication system(broadband access and distribution network system)standard(TD-LTE)proposed by China with independent intellectual property rights has been successfully nominated candidate standards of the International Telecommunication Union 4G.The important MIMO technology was introduced in TD-LTE,which has a great impact on the system capacity and transmission rate.As an important part of mobile system,TD-LTE wireless receiver plays an important role in the communication quality of the whole communication system,therefore,it has theoretical significance and practical value to study the RF front-end devices applied in TD-LTE receiving system.The working frequency bands of TD-LTE have been divided into three bands:1880?1900MHz,2300?2390MHz and 2555?2655MHz.If the 2300?2390MHz band is combined with the 2555?2655MHz band,the TD-LTE frequency band can also be viewed as a dual band system consisting of 2300?2655MHz high frequency band and 1880-1900MHz low frequency band.As the bandwidth of high-frequency band is wider,it can also be called broadband system.The RF front end of TD-LTE receiver includes antenna,filter and low noise amplifier,etc.Therefore,this paper research on RF front end components of the TD-LTE,designed two MIMO dual polarization antennas,a tri-band filter and a low noise amplifier for TD-LTE.The main work and achievements of this paper can be summarized as follows:(1)Designed two TD-LTE dielectric resonator antennas.The dielectric resonator has the advantages of small volume,stable performance,high Q value and convenient feeding,so dielectric resonator antenna structure was used to design the two antennas in this paper:? TD-LTE dual frequency dual polarized dielectric resonator antenna.In order to realize the characteristics of dual frequency,combined single mode dielectric resonator with the microstrip antenna,then the high frequency part and broadband characteristers were achieved;"H" shaped slot was used to feed,and let it resonanced in the low frequency part,realized the low frequency characteristics;and the 1/4 wavelength impedance converter and stubs were used to adjust the impedance matching.? TD-LTE high-isolation broadband dual polarized dielectric resonator antenna.The dielectric resonator was excitated by dual mode to realize the broadband function;high-isolation was improved by using the mixed feed mode of probe and aperture coupling;by adding a patch near probe and double impedance converters near aperture to achieve impedance matching.(2)Designed a tri-band filter.Defect structure step impedance resonator was used to design the first frequency band and the second frequency band bandpass filters,the stepped impedance line loaded with short circuit stub was used to design the third band bandpass filter;By using the coupling line feed way to combine three bandpass filters,so as to realize the effect of the tri-band filter.The processing tested results show that the pass bands of the filter are 1880?1900MHz,2300?2390 and 2555?2655MHz,and in the three frequency band,return loss is greater than 15dB,12dB and 10dB,the insertion loss at the center frequency are 1.37dB,2.5dB and 2.8dB,basically meet the design requirements.(3)Designed a broadband low noise amplifier by using Avago ATF54143 transistor.Two impedance converters were used in the input port of the first stage low noise amplifier,broadband and low noise effect was achieved by controlling the Q value;A low-pass filter was designed in the output port of the first stage low noise amplifier,it was used to filter out the high order harmonics.The second levels of low noise amplifier was conjugate matched to achieve high gain,and low-pass filter matching was designed at the output port.Finally,two low-noise amplifiers were cascaded using 50 microstrip lines.The tested results show that the performances of the amplifier are good,the passband is 2300?2655MHz,in the passband,the return loss is more than 10dB,the gain is more than 22dB,and the curve is flat,the noise figure is less than 1dB,realized wideband characteristic and low noise characteristic.