| With the development of communication technology,the modulation mode of signal is becoming more and more complicated,which results in the increase of system's transmission bandwidth and the peak ratio of the signal.Compared with other types of power amplifiers,Doherty power amplifier has the characteristic of high linearity and good efficiency improvement on the peak ratio signals,which has made it becomes the main type of high efficiency power amplifiers applied in 5G communication base stations.However,considering the ?/4 impedance line and the multi-section microstrip line used in matching networks,the traditional Doherty power amplifier usually works in narrow band and has an excessive circuit size.It is not conducive to the pursuit of broadband and miniaturization of 5G communication system.Focus on improving the two shortcomings mentioned,this thesis studies the CRLH-TL circuits and its applications in Doherty power amplifier.Firstly,this thesis analyzes CRLH-TL unit circuit as power amplifier matching circuit,derives the equivalent circuit of the CRLH-TL unit microstrip form,and completes the design of continuous power amplifier based on CRLH-TL unit circuit.Secondly,the limiting factors of Doherty power amplifier are studied,and the design of dual-band Doherty power amplifier based on CRLH-TL unit circuit is completed.Finally,the simplified circuit structure of CRLH-TL unit in broadband matching network is studied,and the design of a broadband miniaturized Doherty amplifier is completed.The above studies work demonstrates that CRLH-TL can be applied to the matching circuit design of dual-frequency or broadband Doherty amplifier,expand the bandwidth characteristics and reduce the overall size in terms of the circuit characteristics of CRLH-TL itself,the bandwidth limiting factors of Doherty amplifiers and the matching circuit of Doherty amplifiers.The specific contents of this thesis are as follows:(1)Researches on CRLH-TL unit circuit as power amplifier matching circuit.Based on the circuit characteristics of CRLH-TL units,the circuit composed of different CRLH-TL units is analyzed,and the dual-frequency and broadband characteristics of the power amplifier matching circuit are studied.At the same time,the microstrip circuit equivalent to the CRLH-TL unit circuit is derived,which proves the feasibility of the application of the CRLH-TL unit circuit in the power amplifier matching circuit.(2)Researches on broadband impedance matching network design of power amplifier based on CRLH-TL cell circuit.Analyzes the process of power amplifier design,a design method of a broadband impedance matching network based on a CRLH-TL unit circuit is proposed,and a broadband power amplifier is completed and tested in kind.The experimental data shows that when the operating frequency is 1.7~3.1GHz,the power added efficiency in the frequency band is 44.2%~53%,the gain is 10.2~11.2dB,the flatness and gain flatness of the power added efficiency are 4.4% and 0.5dB.(3)Researches on dual frequency design of CRLH-TL unit circuit based Doherty amplifier.Through the dual-band characteristics of dual-band transmission line and CRLH-TL unit circuits,the CRLH-TL unit circuit is used to the output matching circuit of the carrier amplifier and peak amplifier in Doherty power amplifier.Meanwhile,the ?/4 impedance line is replaced with a dual-frequency transmission line.A dual-band Doherty power amplifier working at 2.6GHz and 3.5GHz is designed,the measured results show that the maximum output power in the dual-band are 43.3dBm and 43.2dBm,the efficiency of back-off 6dB are 47.8% and 46.6%,the gain are 11.4dB and 8.8dB,respectively.Achieve the goal of designing dual-band high-efficiency power amplifiers on 5G mid-band.(4)Researches on the design of broadband characteristics of the Doherty amplifier based on CRLH-TL unit circuit.Based on the design of the broadband power amplifier design of the CRLH-TL unit circuit,the broadband matching network structure of the CRLH-TL unit is further optimized,and this circuit structure is used to the broadband Doherty power amplifier.A broadband Doherty power amplifier working at 3.3~4.2GHz is designed,the measured results show that the maximum output power in the frequency band is 42.8~44dBm,the efficiency of back-off 6dB is 36.8%~45.2% and the gain is 7.8~9.4dB.Achieve the goal of designing broadband high-efficiency power amplifiers on 5G mid-band. |
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