The ThermalNoise
object simulates the effects
of thermal noise on a complex, baseband signal.
To add thermal noise to a complex, baseband signal:
Define and set up your thermal noise object. See Construction.
Call step
to add thermal noise
according to the properties of comm.ThermalNoise
.
Note:
Starting in R2016b, instead of using the |
tn = comm.ThermalNoise
creates a receiver
thermal noise System object, H
. This object
adds thermal noise to the complex, baseband input signal.
tn = comm.ThermalNoise(
creates
a receiver thermal noise object, Name
,Value
)H
, with each specified
property set to the specified value. You can specify additional name-value
pair arguments in any order as (Name1
,Value1
,...,NameN
,ValueN
).
step | Add receiver thermal noise |
Common to All System Objects | |
---|---|
clone | Create System object with same property values |
getNumInputs | Expected number of inputs to a System object |
getNumOutputs | Expected number of outputs of a System object |
isLocked | Check locked states of a System object (logical) |
release | Allow System object property value changes |
Wireless receiver performance is often expressed as a noise factor or figure. The noise factor is defined as the ratio of the input signal-to-noise ratio, S_{i}/N_{i} to the output signal-to-noise ratio, S_{o}/N_{o}, such that
$$F=\frac{{S}_{i}/{N}_{i}}{{S}_{o}/{N}_{o}}\text{\hspace{0.17em}}.$$
Given receiver gain G and receiver noise power N_{ckt}, the noise factor can be expressed as
$$\begin{array}{c}F=\frac{{S}_{i}/{N}_{i}}{G{S}_{i}/\left({N}_{ckt}+G{N}_{i}\right)}\\ =\frac{{N}_{ckt}+G{N}_{i}}{G{N}_{i}}\text{\hspace{0.17em}}.\end{array}$$
The IEEE defines the noise factor assuming that noise temperature at the input is T_{0}, where T_{0} = 290 K. The noise factor is then
$$\begin{array}{c}F=\frac{{N}_{ckt}+G{N}_{i}}{G{N}_{i}}\\ =\frac{GkB{T}_{ckt}+GkB{T}_{0}}{GkB{T}_{0}}\\ =\frac{{T}_{ckt}+{T}_{0}}{{T}_{0}}\text{\hspace{0.17em}}.\end{array}$$
T_{ckt} is the equivalent input noise temperature of the receiver and is expressed as
$${T}_{ckt}={T}_{0}(F-1)\text{\hspace{0.17em}}.$$
The overall noise temperature of an antenna and receiver, T_{sys}, is
$${T}_{sys}={T}_{ant}+{T}_{ckt}\text{\hspace{0.17em}},$$
where T_{ant} is the antenna noise temperature.
The noise figure, NF, is the dB equivalent of the noise factor and can be expressed as
$$NF=10{\mathrm{log}}_{10}(F)\text{\hspace{0.17em}}.$$