宽带/多频段高效率混合模式极坐标发射机关键问题研究

Polar transmitter technology is almost the perfect solution to the contradiction between efficiency and linearity, and has broad application prospects in communication systems. But its bandwidth and efficiency are mainly constrained by the bandwidth of switch mode (class-E) power amplifier, the contradictions between slew rate, bandwidth and average efficiency of the envelope channel, as well as signal distortion caused by “feed-through” effect. In order to improve the bandwidth and efficiency of polar transmitter, we proposed a broadband, high-efficiency, hybrid-mode polar transmitter architecture. Firstly, the bandwidth of the class-E amplifier is improved by using continuous operation modes. A multi-frequency matching network and a harmonic suppression network, which is a low-pass filter with outstanding wide stopband performance, are used to realize multi-band class-E power amplifier. Secondly, the contradictions between slew rate, bandwidth and the average efficiency are overcome through the combining-model power supply modulator, which is combined by a switch stage and linear stage. So the bandwidth and overall efficiency of envelope channel are improved. The hybrid-model modulation is studied which is combined with a drive modulation and a drain modulation. The influences of the signal’s hybrid modulation and the amplitude threshold the efficiency of the polar transmitters are also researched, and the signal distortion caused by “feed-through” effect is eliminated. Thirdly, according to the theoretical results, the sample of hybrid-model polar transmitter is fabricated. Subsequently, the test and optimization are also carried out. In the end, a novel polar transmitter with broadband, high efficiency and multi-model is achieved, and its theoretical research system is also established.

极坐标发射机技术几乎完美地解决了效率与线性度之间的矛盾，在通信系统中有着广泛的应用前景。但其带宽和效率却受到开关类（如E类）功率放大器的窄带特性、电源调制器转换速率与效率的矛盾、“feed-through”效应引起的信号失真等因素的制约，限制了其应用推广。本项目针对极坐标发射机的工作带宽和效率问题，提出了宽带/多频段高效率混合模式极坐标发射机结构：采用连续工作模式加二次谐波阻抗匹配的方法，拓宽E类功率放大器的带宽；采用多频点匹配网络加超宽阻带低通滤波技术，实现多频点E类功率放大器。采用开关级和线型级相结合的方式研制混合式电源调制器，解决转换速率、带宽与平均效率之间的矛盾。研究驱动调制和包络调制相结合的混合调制模式，揭示混合调制方式和幅值门限对极坐标效率的影响规律，消除“feed-through”效应引起的信号失真。试制宽带/多频段高效率混合模式极坐标发射机，并构建其理论研究体系。

随着无线通信技术的飞速发展，为了支持高速数据传输和多媒体业务，诸多信号调制和多址方式用来提高频谱效率和可重构性，如正交频分复用(Orthogonal Frequency-division Multiplexing，OFDM)，宽带码分多址(Wideband Code-division Multiple Access，WCDMA)，和多入多出(Multiple-in Multiple-out，MIMO) 。随之带来的是带宽和峰均比的不断增加，而传统的发射机结构为了适应峰均比的增加以及保证线性度，需要采用功率回退技术，这就势必降低了发射机的效率，为了解决发射机线性度与效率之间的矛盾，所提出新型的极坐标发射机结构对于发射机以及无线通信的发展具有重要意义。. 本项目开展了宽带高效率谐波调谐功率放大器研究，采用sequential nested load-pull技术设计宽带高效率功放，在保证高效率的同时，拓展功放带宽，在0.3-3.2GHz频带内，饱和效率61.8%-73.6%，输出功率40.2-42.6 dBm；开展了宽带高效率电源调制器研究，采用开关模式和线性模式相结合的DC-DC降压转换器方案，克服转换效率、带宽与平均效率之间的矛盾，提高了幅度放大通道的带宽和效率；开展了极坐标发射机混合架构研究，采用驱动调制和包络调制相结合的混合调制方式，克服了传统极坐标发射机具有的‘feed-through’效应；开展了幅相分离算法以及脉宽调制方法研究，利用FPGA开发板以及高速DAC开发板实现发射机系统数字处理单元；搭建了混合架构极坐标发射机系统，完成了所研究内容的平台验证。. 本项目系统工作频带覆盖0.3-3.2GHz，适用于QPSK、GSM、EDGE、OFDM等多种调制方式，整体回退效率在47%-55%之间，验证了极坐标发射机的优秀性能。