一种双频段射频能量获取系统

发布时间：2018-06-18 16:04

本文选题：射频整流器 + 能量获取　；参考：《西安电子科技大学》2015年硕士论文

【摘要】：能量获取电路在代替电池作为电源供电方面具有广泛的应用前景。如何高效地获取环境中的能量已经成为人们研究的一个热点。能量获取电路可以应用于无线传感器节点网络(WSN)中,提高其使用寿命,降低制造成本。同时,能量获取电路还可以应用于可穿戴设备中,提高可穿戴设备的续航以及使用寿命。射频(RF)能量由于具有分布范围广泛,稳定的特点,已经被用于射频识别(RFID)芯片中。相对于其它形式的能量获取,RF能量获取是一个难点。本文根据环境中射频能量的分布特点,设计了一个双频段能量获取系统。该能量获取系统可以获取环境中900MHz频段和2.4GHz频段的射频能量,并将其转换为可用的直流电压给后级电路供电。相对于以往的单一频段的RF能量获取,该双频段能量获取可以增加获得的输入功率,提高了RF能量的利用效率。本文还详细地介绍了传统的阈值自补偿整流器的结构以及优缺点。在传统的阈值自补偿整流器的基础之上,本文将利用PMOS(P型场效应晶体管)源极和衬底之间的微弱正偏去降低晶体管的阈值电压,通过将阈值自补偿结构和衬底偏置效应结合起来,整个RF-DC(射频—直流转换)电路在低输入功率下的性能得到了极大的提升。为了进一步研究如何设计RF-DC电路的参数,本文还分别研究了晶体管的宽长比,整流器的级数,补偿阶数,以及阻抗匹配网络的增益对整个RF-DC电路性能的影响。并且给出了粗略估算射频整流器输出电压的表达式。同时根据各个频段的带宽的特点,对双频段的RF-DC电路的性能进行了单独的优化。为了降低整个RF能量获取在充电阶段的功耗,本文使用无电阻结构的带隙基准源以及偏置电流源,这大大降低了整体的功耗以及芯片的面积以及充电阶段整个电路的功耗。同时本文还提出了一种新型的电压检测电路,该电压检测电路在充电阶段只有一个低功耗比较器消耗能量,使用这个低功耗比较器检测电压的上升,而另一个高速比较器只有在电压的下降阶段才正常工作,通过使用低功耗的基准电路,偏置电路,电压检测电路,该RF能量获取在充电阶段的功耗降低到了97nA。为了提高芯片的集成度,本文还使用了DFC(Damping-Factor-Compensation)补偿的无电容LDO(低压差线性稳压器),该LDO通过使用DFC补偿,将主极点移到第一级的输出,不需要利用输出电容的ESR(等效串联电阻)零点就可以达到稳定。通过对整个RF能量获取系统进行仿真,整个RF能量获取在900MHz频率处的最低输入功率可以低达-20dBm。
[Abstract]:Energy acquisition circuit has a wide application prospect in replacing battery as power supply. How to obtain energy efficiently has become a hot topic. Energy acquisition circuit can be used in wireless sensor node network (WSNs) to improve its service life and reduce manufacturing cost. At the same time, the energy acquisition circuit can be used in wearable devices to improve the life of wearable devices. RF energy has been used in RFID chip because of its wide range and stable distribution. Compared with other forms of energy acquisition, RF energy acquisition is a difficulty. According to the characteristics of RF energy distribution in the environment, a dual band energy acquisition system is designed in this paper. The energy acquisition system can obtain the RF energy of 900MHz and 2.4GHz bands in the environment, and convert it to the available DC voltage to supply the back stage circuit. Compared with the previous RF energy acquisition in a single frequency band, the dual-band energy acquisition can increase the input power and improve the efficiency of RF energy utilization. The structure, advantages and disadvantages of the traditional threshold self-compensation rectifier are also introduced in detail. Based on the traditional threshold self-compensation rectifier, the threshold voltage of the transistor is reduced by using the weak positive bias between the source pole and the substrate of the PMOSP-type field-effect transistor. By combining the threshold self-compensation structure with the substrate bias effect, the performance of the whole RF-DC (radio-frequency DC) circuit at low input power is greatly improved. In order to further study how to design the parameters of RF-DC circuits, the effects of the aspect ratio of transistors, the series of rectifiers, the order of compensation and the gain of impedance matching network on the performance of the whole RF-DC circuit are also studied in this paper. An expression for estimating the output voltage of RF rectifier is given. At the same time, according to the bandwidth characteristics of each band, the performance of dual band RF-DC circuit is optimized separately. In order to reduce the power consumption of the whole RF energy acquisition during the charging stage, a resistive structure bandgap reference source and a bias current source are used in this paper, which greatly reduces the overall power consumption, the area of the chip and the power consumption of the whole circuit during the charging phase. At the same time, a new type of voltage detection circuit is proposed, which consumes only one low power comparator in the charging stage, and uses this low power comparator to detect the rise of voltage. The other high speed comparator only works normally at the voltage drop stage. By using a low power reference circuit, a bias circuit, and a voltage detection circuit, the RF energy acquisition power consumption is reduced to 97 na during the charging phase. In order to improve the integration of the chip, this paper also uses DFCN Damping-Factor-Compensation (DFCN) compensated capacitive LDO (low Voltage difference Linear regulator), which moves the main pole to the first stage output by using DFC compensation. The ESRs (equivalent series resistance) zeros of the output capacitance are not needed to achieve stability. Through the simulation of the whole RF energy acquisition system, the minimum input power of the whole RF energy acquisition at 900MHz frequency can be as low as -20dBm.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM619

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