| Now not only in wireless and cable communication, linearization technology in power amplifier has become active. Besides the high data ratio modulation technology application, there are more reasons caused the prosperity in linearization technology.First, upon the requirement of the direct power efficiency, back off method cannot be used in high power amplifier design. the efficiency limit of back off method is 1%～5%.It will caused limited operation period and quite a lot of heat vice production. Besides that in this method high power tube can only output low power. The potential can not be strengthen.Secondly, the application of multicarriers applications in modern communication demand the linearized power amplifier, such as Orthogonal Frequency Division Multiplexing, 802.11(a,b,g) ,High Definition Television and the 4 generation communication . Because the high peak to average ratio in these applications, the nonlinear distorted will worsen the total system functionality. In a word, high efficiency and linearized power amplifier is necessary to satisfy modern communication speciation.A design of linearized WCDMA 35 watts power amplifier is introduced in this paper, combining RF DPD (Digital Predistortion) and Doherty techniques. MRF6P21190 one kind of LDMOS amplifier made by Freescale Company is employed in this design.Firstly setup a Doherty amplifier by this LDMOS amplifier. This step can enhance the total efficiency .Then fabricate the RF DPD circuit before the Doherty amplifier. This step can enhance the ACLR linearity. Combing this two advanced technologies,can generate high efficiency and linear power amplifier. Applying ADS simulation software from Agilent Company, presents that when power amplifier outputs 35 watts, ACLR achieves -55dBC, PAE raises to 27%. This design can not only enhance the performance of WCDMA power amplifier and also good for mass production. Also with higher stability and higher energy efficiency, it is a proper product for 3G WCDMA application. |
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