發(fā)布時(shí)間：2019-03-01 07:56

【摘要】：自動(dòng)增益控制(AGC,Automatic Gain Control)是無(wú)線通信系統(tǒng)的基本電路之一,廣泛應(yīng)用在雷達(dá)、衛(wèi)星導(dǎo)航等接收機(jī)中。它的作用是當(dāng)大動(dòng)態(tài)信號(hào)進(jìn)入到接收機(jī)時(shí),通過(guò)增益的自動(dòng)調(diào)節(jié)使輸出功率保持在一個(gè)較為穩(wěn)定的范圍內(nèi),其目的是實(shí)現(xiàn)信號(hào)的正常解調(diào)。本文在對(duì)國(guó)內(nèi)外發(fā)展研究狀況進(jìn)行綜述的基礎(chǔ)上,詳細(xì)介紹了自動(dòng)增益控制理論及動(dòng)態(tài)范圍、回路建立時(shí)間等重要指標(biāo)。重點(diǎn)對(duì)自動(dòng)增益控制電路內(nèi)的可變?cè)鲆娣糯笃�、檢波器、增益控制電壓產(chǎn)生電路進(jìn)行詳盡分析。根據(jù)系統(tǒng)要求給出了一種采用自動(dòng)步進(jìn)增益控制實(shí)現(xiàn)80dB大動(dòng)態(tài)的方法:分別采用30dB、20dB、10dB、20dB四級(jí)低噪聲放大器通過(guò)開關(guān)轉(zhuǎn)換控制的方式將所需增益放大器接入到電路,實(shí)現(xiàn)了以10dB為步進(jìn)的0-80dB動(dòng)態(tài)范圍,并詳細(xì)介紹了整體指標(biāo)分配和方案。本文隨后對(duì)所給出的方案進(jìn)行了設(shè)計(jì)驗(yàn)證。針對(duì)70MHz的中頻輸入信號(hào),利用低噪聲放大器將其放大到對(duì)數(shù)檢波器AD8310可檢測(cè)的功率范圍內(nèi),檢波器輸出的直流電壓與輸入信號(hào)電壓分貝數(shù)成正比。該電壓與比較器預(yù)設(shè)的參考電平比較產(chǎn)生控制信號(hào),用于控制可變?cè)鲆娣糯蟛糠值拈_關(guān)以實(shí)現(xiàn)-20 dBm~0 dBm的信號(hào)輸出電平變化。最后,完成了整個(gè)自動(dòng)增益控制電路模塊的設(shè)計(jì)、加工、裝配、調(diào)試和動(dòng)態(tài)范圍測(cè)試。對(duì)實(shí)現(xiàn)樣品的實(shí)測(cè)結(jié)果表明,當(dāng)中心頻率為70MHz的信號(hào)在從-90 dBm到-10dBm的范圍內(nèi)變化時(shí),檢波器輸出電壓成線性變化,最終實(shí)現(xiàn)了輸出功率在-14.83dBm~0 dBm范圍內(nèi)變化,噪聲系數(shù)為5.385dB,最大輸出范圍內(nèi)功率呈線性變化。測(cè)試結(jié)果表明,基本滿足預(yù)期的指標(biāo)。最后對(duì)在設(shè)計(jì)和調(diào)試過(guò)程中所遇到的問(wèn)題及解決方案進(jìn)行了總結(jié)。該電路還可充分挖掘潛力,使輸出功率范圍更為小。本設(shè)計(jì)在自動(dòng)增益控制的動(dòng)態(tài)范圍、步進(jìn)式實(shí)現(xiàn)方式以及解決系統(tǒng)穩(wěn)定性等方面有一定的意義和應(yīng)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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN92

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