- General Noise
General Nois
it’s broadest definition, consists of any undesired signal in a communication circuit. The subject of noice and noise reduction is probably the most important single consideration in transmission engineering.
It is the Text, noise is broken down into four categories.
- Intermodulation Noise
- Impulse Noise
- Cross-talk
- Thermal Noise
Thermal noise occurs in all transmission media and all communication equipment, including passive devices such as waveguide. It arises from random electron motion and is characterized by a uniform distribution of energy over the frequency spectrum with a Gaussian distribution of level.
- Gaussian Distribution
We trun to work of the Australian scientist, Ludwig Boltzmann’s constant, we can write a relationship for the thermal noise level 🎚️ (Pn) in 1 Hz of bandwidth at absolutely zero (Kelvin Scale).
Or
Pn = -228.6 dBW per Hz of bandwidth for a receiver 📞 at absolutely zero.
At room temperature 🌡️ (290 K or 17 C) we have
Pn = -204 dBW per Hz of bandwidth for a perfect receiver.
Or
= -174 dBm / Hz of bandwidth for a perfect receiver.
A Perfect Receiver 📞
A perfect receiver is a receiving device that contributes no thermal noise to the communication channel. Of course, this is an idealistic situation that cannot occur in real life. It does provide us a handy reference, through.
The following relationship converts equation given abeve fya real receiver in a real-life setting.
Pn = -204 dBW / Hz+ NF dB + 10 log B ,
Where
B is the bandwidth of the receiver in question. The bandwidth must always be in Hz or converted to Hz.
NF is noise figure of the receiver. It is a terminology that we use to quantify the amount of thermal noise a receiver ( or any other device) injects into communication channel.
The noise figure unit is the dB.
An example of application of equation given above might be a receiver 📞 with a 3-dB noice figure and a 10-MHz bandwidth.
What would be the thermal noise power (level) in dBW of the receiver 📞?
Using equation
Pn = -204 dBw / Hz + 3 dB + 10 log (10 × 10 6)
= – 204 dBW / Hz + 3 dB + 70 dB
= = – 131dBw.
- Intermodulation noise
Intermodulation IM noise is result of the presence of intermodulation products. If two signals with frequencies Fi and Fa are passed through a non-linear device or medium, the result will certain IM product that are spurious frequency energy components. These components may be present either inside and / or outside the frequency band in interest for a particular device or system.
IM product may be produced from harmonic of the desired signal in question, either as products between harmonics, or as one of the basic signal and the harmonic of the other basic signal or between both signals themselves. The product result when two (or more) signals beat together or “mix”. These products can be sum and / or difference. Look at the mixing possibilities when passing Fi and F2 through a non-linear device. The coefficients indicate the first, second, or third harmonics.
Second-order product Fi ± Fi ≥
Third-order product 2Fi ± Fi; 2F2 ± F and
Fourth-order product 2Fi ± 2F2 ± 3Fi ± F2…
Devices passing multiple signals simultaneously, such as a multi-channel radio equipment, develope IM products that are so varied that they resemble white noise.
Intermodulation noise may result from a number of causes.
- Improper level setting
- If the level of an input to a device is too high. The device is driven into a non-linear operating region (overdrive).
- Improper agreement causing a device to function non-linearly.
- Non-linear envelope delay.
- Device malfunction.
- To Summarize
- What is Impulse Noise?
Impulse noise is the sudden and unexpected electrical noise in a telecom network system. Due to this type of noise that the signal quality can be affected.
This type of noise is usually short-lived. But the effect can be severe. Such as the switching of an electronic device and the noise generated by electric shocks or faults in electrical wiring. Impulse noise can cause errors in data transmission, signal loss and connection drops.
Various techniques are used to prevent this, such as noise filtering and subsequent data error correction algorithms, and noise-resistant transmission formats.
Impulse noice is non-continues consisting of irregular pulse or noise spikes of short duration and of relatively high amplitude.
- These spikes are often called hits, and each spikes has a board spectral content ( i.e ., impulse noise smears a broad frequency bandwidth).
Impulse noise degrades voice Telephony usually only marginally, if at all.
However
It may seriously degrade error performance on data or other digital circuits. The causes of impulse noise are lightning car ignitions, mechanical switches ( even light switches ), fluorescent lights, and so on.
- Data corruption
- Connection drop
- Signal Distortion
Such noise can degrade signal quality and clarity. Which can also cause problems in data transmission.
- Waste of bandwidth
Bad packets need to be retransmitted. Due to which network bandwidth is used unnecessarily.
- Decrease in performance
- Addition of technical errors
This noise can degrade network performance. Due to which users may experience slow internet speed or unstable connection.
The presence of impulse noise increases the various technical defects of the network, which require time and resources to correct. Due to these losses, various techniques and technologies are used to reduce the impulse noise and limit its effects. In order to improve the quality.
