Reference noise

Previously, in the case of constant detector noise, we then set Var(A s) and Var(A r) equal to the same value. This is the point at which must we now depart from the previous derivation, since in the case of Poisson-distributed noise the sample and reference noise levels will rarely, if ever, be the same. However, we are fortunate in this case that Poisson-distributed noise has a unique and very useful property that we have indeed previously made use of the variance of Poisson-distributed noise is equal to the mean signal value. Hence we can substitute Es for Var(A s) and Er for Var(A r) ... 

Low frequency roll-off High frequency roll-off Notch filter Input referred noise... 

It may be possible to combine a single channel microwave radiometer and a MMCES. In this case, the results of brightness tenqierature measurement will highly depend on the environment temperature, due to the losses in the MMCES. To overcome this problem, it is necessary to use balance zero radiometer and balance the losses of MMCES and losses of reference noise source. In this situation the losses of MMCES do not decrease the performance of the radiometer. 

Microwave radiometer consists of an electronic switch, circulator, isolator, low-noise amplifier, filter, amplitude detector and miniature reference noise source with the temperature sensor. All foregoing components parts must be designed in miniature sizes using MMIC and plastic materials. 

Since the input-referred noise current Sh(s) is defined by Sh(s) is sfated as... 

Here, Cp denotes Cp + Cp, and 1/Rpi can be ignored since Rf, Ri- The input-referred noise in Equation 29.4 can be reduced by increasing R at the cost of larger area and a smaller bandwidth. To further diminish the noise, the both C and ampi should be minimized. 

Channel noise level The ratio of the channel noise at any point in a transmission system to some arbitrary amount of circuit noise chosen as a reference. This ratio is usually expressed in decibels above reference noise, abbreviated dBm. 

In clause 15 of the statutory regulations relating to places of work (Verordnung iiber Arbeitsstatten, 1975) the following maximum values for the reference noise level in the working environment are laid down ... 

The input-referred noise voltage of this amplifier [29] is given by... 

Fig. 6 Equivalent noise sources for the input-referred noise analysis of the transimpedance amplifier.

Input-Referred Noise < 100 mean rms electrons (2-Hz fcame rate, dependent on sampling tedinique)... 

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