面向新一代高速无线局域网的高性能射频发射机

发布时间：2018-05-31 18:04

本文选题：超外差发射机 + 矢量幅度误差　；参考：《东南大学》2017年硕士论文

【摘要】：随着移动互联网的兴起,以及智能终端设备的快速发展,无线数据流量传输需求呈现爆炸式增长。WLAN系统可以在一些热门无线通信领域快捷方便地提供高速的数据传输速率。未来无线局域网系统的发展需要在更高的数据传输速率、更大的用户容量、充分的接入与组网灵活性、全面的覆盖范围以及更优的用户体验等方面继续努力。在高速无线局域网的众多标准中,IEEE 802.11ac标准正逐渐发展成为行业主流标准,IEEE 802.11ax也将预计于2019年颁布,一些新的关键技术的应用对提升网络数据传输速率起到了至关重要的作用,包括更高阶的调制方案、更宽的信道带宽、发射波束成形以及MU-MIMO等。相应地,WLAN系统对所需要的射频硬件平台所提出的性能要求要更甚从前。本文基于IEEE 802.11ac以及IEEE 802.11ax标准的物理层主要技术指标要求,设计并实现工作于5～6GHz频带、可支持甚高吞吐量(VHT)的8 × 8 MIMO射频硬件系统,着重于射频发射机以及射频本振的设计与实现。首先,通过链路预算仿真确定了发射机系统方案。然后对发射机系统中各功能子模块包括运算放大器、调制器、中频增益控制电路、上变频模块、功放电路以及本振驱动器等进行了分析与设计。逐一测试了各单元子电路的相关参数,以验证系统设计的合理性。另外,本文还单独对射频本振锁相环电路进行了设计、实现与测试。在发射机以及锁相环电路设计的过程中,着重分析并评估了各单元电路的相关技术指标对发射机的EVM性能的影响。本文最终实现的整个发射机系统工作于5～6GHz频段内,采用超外差结构。发射机系统可支持最大信道带宽80MHz,最大符号速率80Msps,最高阶调制1024-QAM,最大可输出功率20dBm。对发射机各项指标展开测试,实测结果表明,对于每一个工作频点,边带抑制优于-45dB,增益平坦度约0.3dB(在80MHz带宽内),在输出功率20dBm时的△IMD3达到46dB,ACPR以及杂散性能均良好。在本文最后,对发射机EVM展开全面的综合的测试。结果显示对于符号速率为10Msps以及80Msps的256-QAM单载波调制信号,调制精度EVM分别优于0.7%和0.9%。对于符合IEEE 802.11ac标准的OFDM信号,当输出功率达10dBm的时候,其EVM(以dB值表示)优于-40dB。最后,施加1024-QAM单载波调制信号于发射机,可观察到符号速率为10Msps、40Msps以及80Msps时的发射机EVM分别能达到0.489%、0.793%以及0.787%。测试结果表明发射机具有良好的性能,能够为新一代无线局域网搭建理想的硬件实验平台。
[Abstract]:With the rise of mobile Internet and the rapid development of intelligent terminal devices, the demand for wireless data traffic transmission is explosive. WLAN system can quickly and conveniently provide high-speed data transmission rate in some popular wireless communication fields. In the future, the development of WLAN system needs more efforts in higher data transmission rate, greater user capacity, full access and networking flexibility, comprehensive coverage and better user experience. Among the many standards of high speed wireless local area network, 802.11ac standard is gradually developing into the mainstream standard in the industry. IEEE 802.11ax is also expected to be promulgated in 2019. The application of some new key technologies plays an important role in improving the data transmission rate of the network. These include higher-order modulation schemes, wider channel bandwidth, transmit beamforming and MU-MIMO. Accordingly, WLAN systems require much higher performance requirements for RF hardware platforms. Based on the main technical requirements of physical layer of IEEE 802.11ac and IEEE 802.11ax standard, this paper designs and implements an 8 脳 8 MIMO RF hardware system which works in the 5~6GHz band and can support very high throughput VHTs. The design and implementation of RF transmitter and RF local oscillator are emphasized. Firstly, the transmitter system scheme is determined by link budget simulation. Then, the functional sub-modules of transmitter system including operational amplifier, modulator, if gain control circuit, up-conversion module, power amplifier circuit and local oscillator driver are analyzed and designed. The relative parameters of each unit sub-circuit are tested one by one to verify the rationality of the system design. In addition, the RF local oscillator PLL circuit is designed, implemented and tested separately. In the design of transmitter and PLL circuit, the influence of relevant technical parameters of each unit circuit on the EVM performance of transmitter is analyzed and evaluated. The transmitter system, which is implemented in this paper, works in the 5~6GHz band and adopts the superheterodyne structure. The transmitter system can support the maximum channel bandwidth of 80MHz, the maximum symbol rate of 80Msps, the highest order modulation of 1024-QAM, and the maximum output power of 20dBm. The experimental results show that the sideband suppression is better than -45 dB, the gain flatness is about 0.3 dB (in 80MHz bandwidth, the IMD3 reaches 46dB / ACPR and the spurious performance is good when the output power is 20dBm). At the end of this paper, the transmitter EVM is tested comprehensively and synthetically. The results show that the modulation accuracy of 256-QAM single carrier modulation signal with symbol rate of 10Msps and 80Msps is better than 0.7% and 0.9% respectively. For the OFDM signal in accordance with the IEEE 802.11ac standard, when the output power is up to 10dBm, the EVM (expressed in dB) is better than -40 dB. Finally, when the 1024-QAM single carrier modulation signal is applied to the transmitter, it can be observed that the transmitter EVM can reach 0.4890.793% and 0.7877when the symbol rate is 10msps / 40Msps and 80Msps respectively. The test results show that the transmitter has good performance and can set up an ideal hardware experimental platform for the new generation WLAN.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN925.93

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