[雙語翻譯]功率放大器外文翻譯--下一代無線通信的功率放大器設計方法

1、3200 英文單詞， 英文單詞，1.7 萬英文字符，中文 萬英文字符，中文 5200 字文獻出處： 文獻出處：Eswaran U, Ramiah H, Kanesan J. Power amplifier design methodologies for next generation wireless communications[J]. IETE Technical Review, 2014, 31(3): 241-248.Powe

2、r Amplifier Design Methodologies for Next Generation Wireless CommunicationsU. Eswaran, H. Ramiah and J. KanesanAbstractAs wireless communication standard continues to evolve accommodating the demand of high data rate op

3、eration, the design of radio frequency (RF) power amplifier (PA) becomes ever challenging. PAs are required to operate more efficiently while maintaining stringent linearity requirement. In this paper, the design concept

4、s of the PA in addressing these challenges are reviewed. The concepts are divided into two main categories, namely the linearization technique and efficiency enhancement technique. The mandatory attempt in realizing a lo

5、w-cost design is also discussed.Keywords: Power amplifiers, Linearization, Wireless, LTE.1. INTRODUCTIONAs the demand for higher data rate continuously increases, the transition from wideband code division multiple acces

6、s (WCDMA) communication standard to 3rd generation partnership project (3GPP) long-term evolution (LTE) begins to pave through the entrance of realization. LTE employs single carrier frequency division multiple access (S

7、C-FDMA) for uplink and orthogonal frequency division multiple access (OFDMA) for down- link, a multicarrier modulation scheme ensuring spectral efficiency [1]. This modulation scheme is subjected to high peak to average

8、ratio (PAPR). SC-FDMA has a similar performance and complexity respective to OFDMA, in favour of lower PAPR [2]. Typically, the PAPR of SC- FDMA signal is 7 dB whereas OFDMA is 10 dB, heavily depending on the modulation

9、scheme adapted (quadrature phase shift keying [QPSK], 16 quadrature amplitude modulation [QAM], or 64 QAM) [3]. To amplify signals with high PAPR, the power amplifier (PA) needs to operate at a backed-off output power sa

10、tisfying the stringent linearity requirement, specified in terms of adjacent channel leakage ratio (ACLR) and error vector magnitude. The drawback of this conventional technique is in the degradation in PA’s power added

11、efficiency (PAE). The relationship between backed-off output power and efficiency for a multicarrier signal can be appreciated in the following equations [4]:where Pbo and Pmax represent backed-off output power and maxim

12、um output power, respectively. For example, if a PA which has Pmax of 35 dBm is transmitting LTE signal with PAPR of 7 dB, the resultant efficiency at Pbo of 28 dBm is 9.9% and 30% in a respective operation of class A an

13、d class B mode. These values may not be suitable for battery-operated mobile devices.The solution to improve the PAE of LTE PA lies in two techniques, which are the efficiency enhancement technique and linearization tech

14、nique. The efficiency enhancement technique mandates in improving the efficiency of a linear PA, while linearization techniques improves the linearity of an efficient non-linear PA.applying another current source at its

15、output terminal. In other words, an active load pull is done at the output of the PA. This principle can be understood with the aid of Figure 2 and its following equations.In Figure 2, “Aux” represents the auxiliary ampl

16、ifier whereas “Main” represents the main amplifier, if “Aux” is inactive, “Main” will observe a load resistance of RLoad. Instead if “Aux” is active and supplies current Iaux, then the load impedance observed by “Main” i

17、s given by It can be observed from Equation (3) that the source current from the auxiliary amplifier (Iaux) can be manipulated to change the load impedance of the main amplifier to improve the efficiency at backed-off ou

18、tput power. The practical implementation of DPA is shown in Figure 3.The output of the carrier amplifier is connected to the output of the peaking amplifier through an impedance transformer (quarter wave transmission lin

19、e) prior terminating to the load. At P bo,, when the peaking amplifier is OFF, the carrier amplifier tends to observe an output impedance of 2RLoad. As a result to this the efficiency of the PA is relatively high at Pbo.

20、 As the input power increases, the peaking amplifier begins to turn ON and generates its output power as depicted in Figure 4.Figure 3: DPA topologyFigure 4: DPA profileAccordingly, the load impedance of the carrier ampl

21、ifier reduces. At Pmax,, the load impedance seen by both amplifiers is RLoad,, which generates an equal output power of Pmax/2 between the carrier and peaking amplifier.Initial work on DPA in mobile wireless communicatio