摘 要
隨著社會(huì)生產(chǎn)力的發(fā)展，人們迫切地要求在遠(yuǎn)距離隨時(shí)隨地迅速而準(zhǔn)確地傳送信息。于是，無線通信技術(shù)得到了迅猛的發(fā)展，技術(shù)也越來越成熟。而高頻放大器是上述通信系統(tǒng)和其它電子系統(tǒng)必不可少的一部分。如在發(fā)射設(shè)備中，就要用高頻功率放大器將信號(hào)放大到所需的發(fā)射功率；在接收設(shè)備中，就要高頻小信號(hào)放大器將非常微弱的信號(hào)放大。由此可知，高頻放大器在通信系統(tǒng)中起著非常重要的作用，于是人們對(duì)它的要求也越來越高。
該題目的基本要求是：3dB通頻帶為10kHz～6MHz；基本增益為40dB，可步進(jìn)調(diào)節(jié)，步進(jìn)間隔為6dB；可預(yù)置增益值，并顯示；最大輸出電壓≥3V；輸入阻抗≥1kΩ；負(fù)載電阻為600Ω；單端輸入、單端輸出。此要求并不難，有多種方案可以實(shí)現(xiàn)，如：①采用場(chǎng)效應(yīng)管作增益控制，高電壓輸出的集成運(yùn)放作功率放大，高速ADC對(duì)電壓進(jìn)行采樣并計(jì)算有效值；②采用可編程放大器作增益控制，分立元件實(shí)現(xiàn)功率放大，用集成真有效值變換芯片測(cè)有效值輸出；③利用可編程增益放大器作增益控制，分立元件實(shí)現(xiàn)功率放大，用二極管包絡(luò)檢波法進(jìn)行峰值檢波計(jì)算有效值等等。
我們選用了第三種方案進(jìn)行設(shè)計(jì)。本設(shè)計(jì)也就是一個(gè)寬帶放大器，利用可變?cè)鲆鎸拵Х糯笃鰽D603來提高增益和擴(kuò)大AGC控制范圍，通過軟件補(bǔ)償減小增益調(diào)節(jié)的步進(jìn)間隔和提高準(zhǔn)確度。輸入部分采用高速電壓反饋運(yùn)放OPA642作跟隨器提高輸入阻抗，并且在不影響性能的條件下給輸入部分加了保護(hù)電路。使用了多種抗干擾措施以減少噪聲并抑制高頻自激。功率輸出部分采用分立元件制作。整個(gè)系統(tǒng)通頻帶為1KHz～20MHz，最小增益0dB，最大增益80dB。增益步進(jìn)為1dB，60dB以下預(yù)置增益與實(shí)際增益誤差小于1dB。不失真輸出電壓有效值可達(dá)9.5V，輸出4.5～5.5V時(shí)，AGC控制范圍為66dB。
關(guān)鍵詞：高頻 寬帶 放大器 高頻放大器 寬帶放大器






Design of High Frequency Amplifier Circuit


Abstract：Along with the development of the social productivity, people request urgently at long-distance leave at any time and anywhere and quickly but deliver the information accurately. Hence, the lead-in correspondence technique got the fast development, the technique is more and more maturing .But the high frequency amplifier is an above correspondence system with other electronics system a part of the essential to have. Such as in shot equipments, will use the high frequency amplifier power enlarger enlarge the signal to a blast-off for needing power; In receive equipments, will the small signal in high frequency amplifier enlarger enlarge the very weak signal. As it describes, the high frequency amplifier is very important in correspond system .hence people to it of the request is higher and higher.
This design in fact is a wideband amplifier, making use of wideband amplifier of AD603 which gain can be changed to increase the gain and extend the AGC control scope .Also through software compensate to decrease the gain of changeable step partition with increases accurate degree. Input part adoption high frequency electric voltage feedback carries of OPA642 to follow behind the machine increases importation resistance, and at term that do not affect the function descend added the importation part to protect the electric circuit. Use various methods to reduce yawp and repress the high frequency from arouse. Power output part adoption cell devices to make. The whole wideband covered from 15MHZ to 20MHz, the least gain is 0 dB, biggest gain is 80 dB. The step of gain is 1 dB. The prepare settle gain compares to the actual gain is smaller 0.2dB when under 60 dB. Do not distortion the voltage valid value can amount to 9.5 Vs, when output covers 4.5 to 5.5 V, AGC control scope is 66 dB.
Key words: High frequency Wideband Amplifier High frequency amplifier
Wideband amplifier



目 錄
1 前言 .................................................................... 1
1.1 放大器的發(fā)展 .......................................................... 1
1.2 放大器的分類 .......................................................... 1
1.3 放大器的主要技術(shù)指標(biāo) .................................................. 2
1.4 本設(shè)計(jì)指標(biāo)要求 ........................................................ 3
2 方案論證與比較 .......................................................... 3
2.1 增益控制部分 .......................................................... 3
2.2 功率輸出部分 .......................................................... 5
2.3 測(cè)量有效值部分 ........................................................ 5
2.4 自動(dòng)增益控制 .......................................................... 6
2.5 系統(tǒng)整體框圖 .......................................................... 6
3 理論分析與參數(shù)計(jì)算 ...................................................... 6
3.1 AD603簡(jiǎn)介 .............................................................6
3.1.1 AD603的主要特點(diǎn) .....................................................6
3.1.2 AD603的工作原理 .....................................................7
3.1.3 AD603應(yīng)用要點(diǎn) .......................................................8
3.2 電壓控制增益的原理 .................................................... 8
3.3 AGC的介紹 .............................................................8
3.3.1 AGC的工..