大动态自动步进增益控制电路的设计与实现

发布时间：2019-03-01 07:56

【摘要】：自动增益控制(AGC,Automatic Gain Control)是无线通信系统的基本电路之一,广泛应用在雷达、卫星导航等接收机中。它的作用是当大动态信号进入到接收机时,通过增益的自动调节使输出功率保持在一个较为稳定的范围内,其目的是实现信号的正常解调。本文在对国内外发展研究状况进行综述的基础上,详细介绍了自动增益控制理论及动态范围、回路建立时间等重要指标。重点对自动增益控制电路内的可变增益放大器、检波器、增益控制电压产生电路进行详尽分析。根据系统要求给出了一种采用自动步进增益控制实现80dB大动态的方法:分别采用30dB、20dB、10dB、20dB四级低噪声放大器通过开关转换控制的方式将所需增益放大器接入到电路,实现了以10dB为步进的0-80dB动态范围,并详细介绍了整体指标分配和方案。本文随后对所给出的方案进行了设计验证。针对70MHz的中频输入信号,利用低噪声放大器将其放大到对数检波器AD8310可检测的功率范围内,检波器输出的直流电压与输入信号电压分贝数成正比。该电压与比较器预设的参考电平比较产生控制信号,用于控制可变增益放大部分的开关以实现-20 dBm~0 dBm的信号输出电平变化。最后,完成了整个自动增益控制电路模块的设计、加工、装配、调试和动态范围测试。对实现样品的实测结果表明,当中心频率为70MHz的信号在从-90 dBm到-10dBm的范围内变化时,检波器输出电压成线性变化,最终实现了输出功率在-14.83dBm~0 dBm范围内变化,噪声系数为5.385dB,最大输出范围内功率呈线性变化。测试结果表明,基本满足预期的指标。最后对在设计和调试过程中所遇到的问题及解决方案进行了总结。该电路还可充分挖掘潜力,使输出功率范围更为小。本设计在自动增益控制的动态范围、步进式实现方式以及解决系统稳定性等方面有一定的意义和应用前景。
[Abstract]:Automatic gain control (AGC,Automatic Gain Control) is one of the basic circuits of wireless communication system, which is widely used in radar, satellite navigation and other receivers. Its function is to keep the output power within a stable range by automatic gain adjustment when the large dynamic signal enters the receiver, the purpose of which is to realize the normal demodulation of the signal. Based on the review of the development at home and abroad, this paper introduces the theory of automatic gain control, the dynamic range, the time of loop establishment and other important indexes in detail. The variable gain amplifier, geophone and gain control voltage generation circuit in the automatic gain control circuit are analyzed in detail. According to the requirements of the system, this paper presents a method to realize the large dynamic of 80dB by automatic step gain control: 30 dB, 20 dB, 10 dB, 20 dB four-stage low noise amplifier is used to connect the required gain amplifier to the circuit by means of switching and switching control. The dynamic range of 0-80dB with 10dB as step-by-step is realized, and the overall index allocation and scheme are introduced in detail. In this paper, the design of the proposed scheme is verified. For the intermediate frequency input signal of 70MHz, the low noise amplifier is used to amplify it to the power range which can be detected by the logarithmic detector AD8310. The output DC voltage of the detector is proportional to the number of decibels of the input signal voltage. The voltage is compared with a reference level preset by the comparator to generate a control signal for controlling most switches of the variable gain amplifier to achieve a signal output level change of-20 dBm~0 dBm. Finally, the design, machining, assembly, debugging and dynamic range testing of the whole automatic gain control circuit module are completed. The experimental results show that the output voltage of the geophone varies linearly from-90 dBm to-10dBm when the center frequency is 70MHz in the range of-90 dBm to-10dBm, and the output power is changed in the range of-14.83dBm~0 dBm. The noise figure is 5.385dB, and the power changes linearly in the maximum output range. The test results show that the expected index is basically met. Finally, the problems and solutions in the process of design and debugging are summarized. The circuit can also fully tap the potential, so that the output power range is smaller. This design has certain significance and application prospect in the dynamic range of automatic gain control, the way of step-by-step realization and the solution to the stability of the system.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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