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接收機(jī)下變頻器級(jí)聯(lián)噪聲系數(shù)研究
2021年電子技術(shù)應(yīng)用第1期
張廣顯
中國(guó)電子科技集團(tuán)公司第十三研究所,,河北 石家莊050051
摘要: 依據(jù)噪聲系數(shù)定義,,推導(dǎo)出了包含混頻器接收機(jī)的級(jí)聯(lián)噪聲系數(shù)公式,,根據(jù)公式很容易計(jì)算和分析器件噪聲、增益及鏡頻抑制度對(duì)整機(jī)噪聲系數(shù)的影響,。鏡頻抑制濾波器位置要在低噪聲放大器后盡量靠近混頻器,,濾波器前的增益以及濾波器鏡頻抑制度要足夠大,至少大于20 dB,。通過(guò)合理的結(jié)構(gòu)設(shè)計(jì)以及鏡頻抑制后,,二次、三次下變頻接收機(jī)噪聲系數(shù)分別比鏡頻噪聲完全不抑制時(shí)降低接近6 dB,、9 dB,。
中圖分類號(hào): TN85
文獻(xiàn)標(biāo)識(shí)碼: A
DOI:10.16157/j.issn.0258-7998.201068
中文引用格式: 張廣顯. 接收機(jī)下變頻器級(jí)聯(lián)噪聲系數(shù)研究[J].電子技術(shù)應(yīng)用,2021,,47(1):7-10.
英文引用格式: Zhang Guangxian. Study on cascade noise figure of receivers with down converter[J]. Application of Electronic Technique,,2021,47(1):7-10.
Study on cascade noise figure of receivers with down converter
Zhang Guangxian
The 13th Research Institute,,CETC,,Shijiazhuang 050051,China
Abstract: According to the definition of noise figure,,this paper deduces the cascade noise figure formula of receivers with mixers. By using this formula,,it is easy to calculate and analysis the system noise figure affected by the device noise figure, gain and filter image rejection. The position of image rejection filter behind the low noise amplifier needs place as close as to the mixer. The gain before the filter and filter image rejection needs high enough, at least greater than 20 dB. Through the proper design and image rejection, the noise figure of the receiver which has two-stages, three-stages frequency conversion will decrease close to 6 dB and 9 dB, than when the image noise do not be rejected at all.
Key words : receiver;cascade;noise figure,;mixer,;image rejection

0 引言

    接收機(jī)廣泛應(yīng)用于廣播、電視,、雷達(dá)等系統(tǒng)中[1-2],,隨著通信頻率的提高,為了便于濾除雜波,,一般需要多次下變頻才能得到可以解調(diào)的中頻頻率,。單邊帶接收機(jī)需要將射頻FRF本振FLO進(jìn)行混頻輸出中頻FIF,射頻頻率(FLO±FIF)兩個(gè)頻率都會(huì)混頻成中頻,,其中含有有用信號(hào)的只有一個(gè)邊帶,,另一個(gè)邊帶為無(wú)用雜波信號(hào)被稱作鏡像頻率。鏡像頻率會(huì)增大系統(tǒng)噪聲系數(shù)約3 dB,,在下變頻前加入鏡像頻率抑制濾波器可以有效抑制鏡像噪聲,,提高系統(tǒng)靈敏度,文獻(xiàn)[3]-[6]中對(duì)此皆有論述,,但是卻沒(méi)有給出簡(jiǎn)單實(shí)用的計(jì)算公式,。本文分析帶有鏡像抑制濾波器的接收系統(tǒng)級(jí)聯(lián)噪聲系數(shù)計(jì)算公式以及噪聲系數(shù)受鏡像頻率抑制度的影響情況。




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作者信息:

張廣顯

(中國(guó)電子科技集團(tuán)公司第十三研究所,,河北 石家莊050051)

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