Need for Modulation:
- The baseband signals can be transmitted directly,
but the baseband transmission has many limitations which can be overcome
using modulation.
- In the process of modulation, the baseband signal is
translated i.e. shifted from low frequency to high frequency.
- This frequency shift is proportional to the
frequency of carrier.
- The modulation process has the following advantages:
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Modulator, 16in1 Digital Headend, HD RF Modulator at Soukacatv.com
Advantages of
modulation:
- Reduction in the
height of antenna:
- When the transmission occurs over free pace, the
antennae radiate the signal out and receiver receives it. In order to
operate efficiently, antennae need to be in order of the magnitude of
wavelength of the transmitted signal.
- For the transmission of radio signals, the antenna
height must be a multiple of (λ/4).Here λ is the wavelength. Λ =c/f where
c is velocity of light and f is the frequency of the signal to be
transmitted.
- The minimum antenna height required to transmit a
baseband signal of f=10 kHz is calculated as follows:
Minimum antenna height= λ/4 = c/4f= (3* 108108)/(410103103 )=7500meters i.e. 7.5 km
It is impossible to
build antennae this big.
- Now consider a modulated signal at f= 1MHz.The
minimum antenna height is given by,
Minimum antenna
height= λ/4 = c/4f=(3108108)/(410*106106 )=75 meter
- This length of the antenna can be built easily and this example clearly shows us how hugely the process of modulation is enabling communication systems.
-Avoids mixing of
signals:
- This is a point from the practical side of things.
Suppose you are transmitting the baseband signal as it is to a receiver,
say your friends phone. Just like you , there will be thousands of people
of people in the city using their mobile phones.
- There is no way to tell such signals apart and they
will interfere with each other leading to a lot of noise in the system and
a very bad output.
- By using a carrier wave of high frequencies and
allotting a band of frequencies to each message, there is no mixing up of
signals and the received signals are absolutely perfect.
-Increase the range
of communication:
- By using modulation to transmit the signals through
space to long distances, we have removed the need for wires in the
communication systems.
- The technique of modulation helped humans to use
wireless equipment in a bug way in their lives.
-Multiplexing is
possible:
- Multiplexing is a process in which two or more
signals can be transmitted over the same communication channel
simultaneously. This is possible only with modulation.
- The Multiplexing allows the same channel to be used
by many signals.
-Improves quality
of reception:
- With frequency modulation
(FM), and the digital communication techniques like PCM, the effect of
noise is reduced to a great extent. This improves quality of reception.
Established in 2000, the Soukacatv.com main
products are modulators both in analog and digital ones, amplifier and
combiner. We are the very first one in manufacturing the headend system in
China. Our 16 in 1 and 24 in 1 now are the most popular products all over the
world.
For more, please access to
https://www.soukacatv.com.
CONTACT US
Dingshengwei Electronics Co., Ltd
Company Address: Buliding A,the first industry park of
Guanlong,Xili Town,Nanshan,Shenzhen,Guangdong,China
Tel : +86 0755 26909863
Fax : +86 0755 26984949
Phone: +86 13410066011
Email:ken@soukacatv.com
Skype: soukaken
Source: ques10
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