[信号与噪声的计算.docxVIP

信号与噪声的计算RECEIVER SENSITIVITY / NOISERECEIVER SENSITIVITYSensitivity in a receiver is normally taken as the minimum input signal (Smin) required to produce a specified output signal having a specified signal-to-noise (S/N) ratio and is defined as the minimum signal-to-noise ratio times the mean noise power, see equation [1]. For a signal impinging on the antenna (system level) sensitivity is known as minimum operational sensitivity (MOS), see equation [2]. Since MOS includes antenna gain, it may be expressed in dBLi (dB referenced to a linear isotropic antenna). When specifying the sensitivity of receivers intended to intercept and process pulse signals, the minimum pulse width at which the specified sensitivity applies must also be stated. See the discussion of post-detection bandwidth (BV) later in this section for significance of minimum pulsewidth in the receiver design.[1]Smin = (S/N)minkToB(NF)receiver sensitivity (black box performance parameter)[2]MOS = (S/N)minkToB(NF)/Gsystem sensitivity i.e. the receiver is connected to an antenna(transmission line loss included with antenna gain)where:S/Nmin = Minimum signal-to-noise ratio needed to process (vice just detect) a signalNF = Noise figure/factork = Boltzmanns Constant = 1.38 x 10-23 Joule/°KTo = Absolute temperature of the receiver input (°Kelvin) = 290 °KB = Receiver Bandwidth (Hz)G = Antenna/system gainWe have a lower MOS if temperature, bandwidth, NF, or S/Nmin decreases, or if antenna gain increases. For radar, missile, and EW receivers, sensitivity is usually stated in dBm. For communications and commercial broadcasting receivers, sensitivity is usually stated in micro-volts or dBv.?There is no standard definition of sensitivity level. The term minimum operational sensitivity (MOS) can be used in place of Smin at the system level where aircraft installation characteristics are included. The black box term minimum detectable signal (MDS) is often used for Smin but can cause confusion because a receiver ma