Radio communications

Содержание и основные понятия

A low frequency information signal is transferred to a high frequency variable amplitude, frequency or phase. The receiver selects the right channel and restores the data.
GEF · 11 grade
PIF · Baseline
Interactive model
loader
Modification
demodulation
Strip
noise
01
The physical picture
What happens and what boundaries the model has.
Main message
A low frequency information signal is transferred to a high frequency variable amplitude, frequency or phase. The receiver selects the right channel and restores the data.
The module makes the antenna a practical size and divides the channels.
The digital signal encodes the sequence of symbols and protects against errors.
The frequency lane limits the transmission speed and requires the sharing of the spectrum.
How to reason
First, name the system and the interaction, then select the values, and only then write down the law. The formula works within the model's assumptions.
02
Laws and values
Symbols should be read as a relationship of values, not as a recipe for substitution.
ν
нес
≫
ν
сигн
\nu_{\text{нес}}\gg\nu_{\text{сигн}}
ν
not covered
​
≫
ν
Signal
​
condition carrying
R
≈
B
log
⁡
2
⁣
(
1
+
S
N
)
R\approx B\log_2\!\left(1+\frac{S}{N}\right)
R
≈
B
lo
g
2
​
(
1
+
N
S
​
)
quality link of lane and speed
Review of the situation
FM-radio transmits a sound of minor changes in the load frequency, keeping it almost constant.
04
Links and application
In the real world
FM-radio transmits a sound of minor changes in the load frequency, keeping it almost constant.
Model verification
Compare the prediction with observation, evaluate the units, the order of magnitude and the influence of the factors not taken into account. Disparity does not always mean an error of law: often idealization is no longer sufficient.
C
What needs to be understood
Outcome 1
Explain the physical meaning of Radiocommunication through the model, not just through the formula.
Outcome 2
Identify and correctly use the terms: load, modularization, demodulation.
Outcome 3
Indicate the conditions for the applicability of the law, verify units and limit cases.
T
Terms of the topic
The definition should indicate the physical meaning, not a substitute for a domestic synonym.
loader
High-frequency fluctuations, one of whose parameters is modified to transmit information.
Modification
Change of load variable parameter according to the information signal.
demodulation
Select information signal from modified high frequency fluctuations.
Strip
Frequency range taken by signal or transmitted by the communication system.
noise
Undesired random signal preventing the release of the information transmitted.
F
Origin and conclusion of the formulas
The fundamental law cannot be "proven" by algebras: for each record, it is stated whether it is a definition, an experimental law, or a model effect.
ν
нес
≫
ν
сигн
\nu_{\text{нес}}\gg\nu_{\text{сигн}}
ν
not covered
​
≫
ν
Signal
​
model effect
The condition is carrying.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
s
(
t
)
=
A
(
t
)
cos
⁡
(
2
π
ν
нес
t
)
s(t)=A(t)\cos(2\pi\nu_{\text{нес}}t)
s
(
t
)
=
A
(
t
)
cos
(
2
π
ν
not covered
​
t
)
In amplitude modularization, a slow information signal triggers a high-frequency bending load.
∣
d
A
d
t
∣
≪
2
π
ν
нес
∣
A
∣
\left|\frac{dA}{dt}\right|\ll2\pi\nu_{\text{нес}}|A|
​
d
t
d
A
​
​
≪
2
π
ν
not covered
​
∣
A
∣
In order for the bending to remain almost unchanged in one period of load, its characteristic frequency must be significantly smaller.
ν
нес
≫
ν
сигн
\nu_{\text{нес}}\gg\nu_{\text{сигн}}
ν
not covered
​
≫
ν
Signal
​
This scale split allows for sustainable modularization and then the signal to be released.
Conditions:
Shortband modularization: the upper significant frequency of the information signal is much lower than the frequency of load.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
R
≈
B
log
⁡
2
⁣
(
1
+
S
N
)
R\approx B\log_2\!\left(1+\frac{S}{N}\right)
R
≈
B
lo
g
2
​
(
1
+
N
S
​
)
model effect
The quality connection of the lane and speed.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
C
=
B
log
⁡
2
⁣
(
1
+
S
N
)
C=B\log_2\!\left(1+\frac{S}{N}\right)
C
=
B
lo
g
2
​
(
1
+
N
S
​
)
Shannon's theorem gives the channel's maximum information speed with an additive white Gaussian noise.
R
≤
C
R\le C
R
≤
C
A reliable gear is possible at a speed not exceeding the tunnel capacity.
R
≈
C
R\approx C
R
≈
C
A sign of approximate equality means work close to the theoretical limit with good coding.
Conditions:
An idealized channel with strip B, additive white Gaussian noise and S/N average capacity ratio; real speed is usually less than the limit.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
!
Model boundaries and typical errors
Error: Forget model condition
You can't move the formula to any situation just because the letters match. The key condition of this topic is that the module makes the antenna practical and divides the channels.
How to Check the Mind
The digital signal encodes the sequence of symbols and protects against errors. Then check the units, vector direction, and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
Radio communications
A low frequency information signal is transferred to a high frequency variable amplitude, frequency or phase. The receiver selects the right channel and restores the data.
The module makes the antenna a practical size and divides the channels.
The digital signal encodes the sequence of symbols and protects against errors.
Any numerical result shall be accompanied by a unit, a sign and an explanation of its physical meaning.
The content is consistent with the FRP on Physics of the OS/OSS 2025 and the subject matter of the current lines of the PNP: I. M. Peryškin and co-authors (7–9), G. J. Mäkishev and coauthors (10–11), and with the lines "Engineers of the Future" and V. A. Kasyanov. The original texts are not reproduced, the text of the textbooks is not reproduced.