lora链路预算.pdf

发布时间：2022-06-01 发布人：admin 分类：说明书资料大小：0.17M 资料格式：pdf 举报版权申诉

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LORA / LORAWAN TUTORIAL 8 Link Budget & Link Margin mobilefish.com ANT ANT Tx radio cable path loss cable Rx radio v1.0.1

INTRO • In this tutorial I will explain what link budgets, maximum link budgets and link margins are. mobilefish.com

mobilefish.com MODULATION & DEMODULATION • If an input signal (=message) is imposed onto a carrier signal this process is called modulation. The modulated signal is broadcasted to the receiver. • Demodulation is the opposite, where the original signal (= message) is recovered from the modulated carrier wave. ANT ANT message Tx radio cable modulated carrier wave cable Rx radio message carrier wave sender receiver

LINK BUDGET AND LINK MARGIN ANT ANT mobilefish.com gain loss Tx radio cable path loss cable Rx radio +20dBm +10dBi -5dB ) m B d ( r e w o P +12dBi -115dB -2dB Rx power or RSSI Link margin Rx sensitivity Distance

mobilefish.com LINK BUDGET AND LINK MARGIN • A link budget is the sum of all of the gains and losses from the transmitter, through the medium (aka free space), to the receiver in a telecommunication system.  It is a way of quantifying the link performance. • Transmitter:The radio transmitter value must be speciﬁed in dbm, otherwise you do not know its absolute value. • Gains: Antenna (Unit: dbi) • Losses: cables, connectors, signal propagating thru the medium (Unit: db) • When a signal propagates thru the medium, the signal loses strength.   This is called the path loss or path attenuation.

mobilefish.com LINK BUDGET AND LINK MARGIN • A simple link budget equation looks like this:  Received Power = Transmitted Power + Gains − Losses  For example: Received Power = 20 - 5 + 10 - 115 + 12 - 2 = -80 dBm • The receiver sensitivity is the lowest power level at which receiver can receive or demodulate the signal.  For example: Receiver sensitivity = -90 dBm • The link margin is the difference between the received power and receiver sensitivity.  Link margin = Received power - Receiver sensitivity  Link margin in dBm  Received power in dBm  Receiver sensitivity in dBm 

LINK BUDGET AND LINK MARGIN mobilefish.com ANT Example:  Link margin = Received power - Receiver sensitivity cable Rx radio Received power = -80dBm Receiver sensitivity = -90dBm  Link margin = -80 - (-90) = 10 dBm = 10 mW Rx power or RSSI margin Rx sensitivity

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