OBJECTIVES:
To explain digital
modulation
To identify the different digital modulation schemes
To discuss the operations and features of the different modules
To identify the different digital modulation schemes
To discuss the operations and features of the different modules
KEY TERMS:
Digital Transmission is the
transmittal of digital pulses between two or more points in a communication
system
Digital Radio is the transmittal of digitally modulated analog carrier between two or more points in a communication system.
Bit Rate is the rate of change in the input of modulator.
Baud Rate is the rate of change in the output of modulator.
Digital Radio is the transmittal of digitally modulated analog carrier between two or more points in a communication system.
Bit Rate is the rate of change in the input of modulator.
Baud Rate is the rate of change in the output of modulator.
Before anything else,
let us first recall or understand the difference between Analog Signals and
Digital Signals; and the difference between Analog Radio and Digital Radio.
HDMI Encoder Modulator,
16in1 Digital Headend, HD RF Modulator at Soukacatv.com
SKD32 IPTV Gateway
SKD18 IP QAM Modulator
SKD3013 3 Channel HD Encode Modulator
The Comparison
between Analog Signals and Digital Signals:
ADVANTAGES of
Digital Signals
Ease of Processing. Rather than being sinusoidal or
having a continuous value of signals, the digital signal has a sequence of two
discrete values. It can either be 1 or 0 but cannot be in between. These look
like square waves.
Ease of Multiplexing. Multiplexing is a method of combining signals so it is easier to combine discrete data than continuous.
Noise Immunity. In [Digital Communication #1: Information Capacity] I explained noise. They are the unwanted signals that interfere with our signals. Because of the type of wave the digital signal possess, it is hard for the noise to penetrate the signal.
Ease of Multiplexing. Multiplexing is a method of combining signals so it is easier to combine discrete data than continuous.
Noise Immunity. In [Digital Communication #1: Information Capacity] I explained noise. They are the unwanted signals that interfere with our signals. Because of the type of wave the digital signal possess, it is hard for the noise to penetrate the signal.
DISADVANTAGES of Digital
Signals
Circuit Complexity.
Higher Cost.
Circuit Complexity.
Higher Cost.
The Comparison
between Analog Radio and Digital Radio:
In digital radio, the
modulating and demodulating signals are digital pulses rather than analog
waveforms.
Digital Radios used Digital Modulation Schemes.
Digital Radios used Digital Modulation Schemes.
What is Digital Modulation?
Digital Modulation is
the transmittal of digitally modulated analog signals (carrier) between two or
more points in a communication system. It is sometimes called as Digital
Radio – Tomasi.
Have you ever wonder
how is it even possible to send information without physical contact? Just like
what I did, I typed this information and sent it here but how? Is it a magic
that the messages we send and post online just appear from nowhere? Of course
not! And everything we believe as magic can be explained through science. So to
correct you and make you understand how things in our electronic communication
been possible keep on reading and let us untangle the curiosity in ourselves.
Whenever we send a
message from a transmitter, there is what we call carriers. These are the
high-frequency signals that carry our information. They undergo a process
called modulation. Modulation is
where the carrier signal is changed and serves as the envelope or capsule of
the information. Why is it that the carrier must be changed? Well that is the
nature of modulation because if ever the information is the one being changed
then the text you sent will also be changed. For instance you texted your
partner the words’ LOVE YOU” but because of the unwanted changes of
information occurred, then he/she may receive” YOU ARE NOT THE ONLY ONE” instead.
It is impractical to use analog modulation so nowadays, we use digital
modulation. In the type of modulation we are currently using, the information
signal is also digital, which could be encoded or computer-generated but still
uses an analog carrier. An Analog-to-Digital Converter is use resulting to a
more complex circuit than an Analog Modulation Technique.
Digital Modulation uses bit rate frequency or bf, which is basically the rate of change to the input of the modulator. It is represented by bits per second or bps.
Digital Modulation uses bit rate frequency or bf, which is basically the rate of change to the input of the modulator. It is represented by bits per second or bps.
SKD121X Encoding & Multiplexing Modulator
SKD81 IP Set Top Box
What are the Kinds of
Digital Modulation?
1. Amplitude Shift Keying
It is simply a double
sideband, full carrier amplitude modulation where the input modulating signal
is in binary waveform. The output signal is always dependent on its input
signal. It is basically an equivalent of an A.M. (Amplitude Modulation) wherein
the amplitude of the signal is what being change. It is sometimes called
as continuous wave modulation or on-off keying since because it
is in binary form, it can only be shifted as on or off.
ASK Operation
If the INPUT logic is HIGH then
the OUTPUT is the
maximum peak amplitude of the carrier. While if the INPUT is LOW then
the OUTPUT is ZERO.
It only follows multiplication.
2. Frequency Shift Keying
It is a form of
constant amplitude angle modulation that was proved by Emily Baudot,
it similar to conventional FM or Frequency Modulation except that the
modulating signal is a binary signal. This signal varies between two discrete
levels. These levels can either be logic 1 known as Mark Frequency or logic 0 known
as * Space Frequency*.
FSK Operation
If the INPUT logic is HIGH then
the OUTPUT is the
Mark Frequency. While if the INPUT is LOW then
the OUTPUT is the
Space Frequency.
3. Phase Shift Keying
This is another form
of angle modulated, constant amplitude digital modulation --Tomasi
This is basically an
equivalent of PM or Phase Modulation but the difference is that its input
signal is in the form of binary.
Types of PSK
Binary PSK
There are two possible output phases for a single carrier frequency which is either logic 1 or logic 0.
When the digital signal changes it state then the phase of the output carrier shifts between two angles that are 180 degrees out of phase of the carrier.
It is a form of suppressed carrier, square wave modulation of a continuous wave signal.
It is sometimes called as Phase Reversal Keying or Biphase Modulation
There are two possible output phases for a single carrier frequency which is either logic 1 or logic 0.
When the digital signal changes it state then the phase of the output carrier shifts between two angles that are 180 degrees out of phase of the carrier.
It is a form of suppressed carrier, square wave modulation of a continuous wave signal.
It is sometimes called as Phase Reversal Keying or Biphase Modulation
Quaternary PSK
The angle is being modulated while there is constant amplitude.
From the its name “Quaternary”, it basically means that there are 4 possible output phases in a single carrier frequency with different input conditions
The angle is being modulated while there is constant amplitude.
From the its name “Quaternary”, it basically means that there are 4 possible output phases in a single carrier frequency with different input conditions
8-PSK
The incoming bits are considered in groups of 3 or known as tribits
The incoming serial bit stream enters in the bit splitter
The I (in- phase) or Q (quadrature) bit determines the polarity while the C (control channels) bit provides the magnitude.
The incoming bits are considered in groups of 3 or known as tribits
The incoming serial bit stream enters in the bit splitter
The I (in- phase) or Q (quadrature) bit determines the polarity while the C (control channels) bit provides the magnitude.
16-PSK
The incoming bits are considered in groups of 4 or known as quad bits
The output does not change until 4 bits have been inputted into the modulator.
The incoming bits are considered in groups of 4 or known as quad bits
The output does not change until 4 bits have been inputted into the modulator.
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: Building 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
没有评论:
发表评论