Design and realization of dual-band power amplifier based on balanced structure
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摘要: 并发式双波段功率放大器一直是5G通信技术研究的热点之一. 当双频激励信号同时出现时,传统的双波段功放会由于双频信号所产生的调制效应导致阻抗匹配恶化,甚至出现失配的情况. 针对以上问题,文中提出的功放利用平衡结构,优化其匹配特性,将阻抗失配所产生的反射分量通过双频耦合器消除,从而很大程度上改善调制效应所导致的失配问题,改善输出、输入端口的驻波情况,提升功放的性能以及稳定性,基于上述方法设计了一款能够同时在GSM900和TD-LTE频段工作的功率放大器. 在本文首先基于π型阻抗变换结构,设计了一款并发双波段3 dB定向耦合器,此外为避免出现双频阻抗变换器计算繁琐和空间布局困难的情况,在支路放大电路采用π型和T型结合的双频阻抗变换器,经过理论推导和仿真,可实现任意频率的两个不同阻抗变换,最终实现了工作在GSM900和TD-LTE频段的平衡式并发双波段功率放大器. 本设计基于ADS仿真平台,选用GaN晶体管CGH40010F进行设计仿真,并以Rogers4350b板材制作实物. 实测结果显示,在900 MHz和2.6 GHz两个频段上匹配良好,与传统并发双波段功放相比较,本文提出的功放结构能够显著优化匹配性能,驻波系数有明显降低,饱和输出功率为44.6 dBm和43.3 dBm,相比于单管功放的饱和输出功率提升了一倍,两个工作频段上功率附加效率(power added efficiency, PAE)分别为62%和64%,实测与仿真差距较小,具有较好的一致性. 通过分析与测试,该功放结构能够很好地适应无线通信系统的发展需求.Abstract: Dual-band power amplifiers have been one of the hot spots in 5G research. When dual-band excitation signals appear at the same time, the traditional dual-band power amplifier will deteriorate the impedance matching due to the modulation effect produced by the dual-frequency signal, even mismatch occurring. For the problems mentioned above, the power amplifier proposed in this article uses a balanced structure , continuously optimizing its matching degree, and the reflection component caused by impedance mismatch is eliminated by dual frequency coupler, thereby the impedance mismatch caused by modulation effect can be improved largely. Firstly, this paper is based on π-type impedance transform structure , which design a concurrent dual-band 3dB directional coupler. In addition ,in order to avoid the cumbersome calculation of the dual-frequency impedance converter and difficult space layout, the branch amplifier circuit adopts a dual-frequency impedance converter model combining π-type and T-type. Through theoretical derivation and simulation of power amplifier, this structure can realize different impedance transformations at any frequency. Finally, the power amplifier can be applied in both GSM900 and TD-LTE at the same time. The design is based on the ADS simulation platform, and the GaN transistor CGH40010F is selected for the design simulation. Meanwhile, the Rogers 4350 b sheet is used to make a material object. The measured results show that it can match with 900 MHz and 2.6 GHz frequency bands very well, compared with traditional concurrent dual band power amplifier, the power amplifier structure proposed in this paper can optimize the matching performance significantly, and the VSWR has been reduced effectively. Saturated output power is 44.6 dBm and 43.3 dBm.Compared with the single power amplifier, the saturated output power has doubled. The PAE on the two working frequency bands is 62% and 64%, respectively, where is a small gap between actual measurement and simulation, which has good consistency. By analysis and test, the power amplifier can adapt to the development needs of wireless communication systems well .
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Key words:
- balanced structure /
- dual-band coupler /
- dual-band impedance transformation /
- high power output /
- VSWR /
- GaN
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表 1 晶体管最佳输入/输出阻抗
Tab. 1 Transistor optimum input/output impedance
工作频率 最佳源阻抗 最佳负载阻抗 900 MHz 7.1+10.2j 25+23j 2.6 GHz 5.6–3.3j 13.2+12.3j -
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