Microwave communication by abhishek mahajan
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Transcript of Microwave communication by abhishek mahajan
SHREEJEE INSTITUTE OF TECHNOLOGY AND MANAGEMENT
Microwave communication
• Guided by:- Mr. Prakash Singh Panwar
• By:-Shubham Yadav• EC BRANCH 1ST YEAR
Definition of MicrowaveMicrowave
Microwave is a kind of electromagnetic wave. In a broad sense, the microwave
frequency range is from 300 MHz to 300 GHz. But In microwave communication,
the frequency range is generally from 3 GHz to 30 GHz.
According to the characteristics of microwave propagation, microwave can be
considered as plane wave.
The plane wave has no electric field and magnetic field longitudinal components
along the propagation direction. The electric field and magnetic field components
are vertical to the propagation direction. Therefore, it is called transverse
electromagnetic wave and TEM wave for short.
Development of Microwave Communication
• a
155M
34/140M
2/4/6/8M
480 voice channels
SDH digital microwave communication
system
PDH digital microwave communication
system Small and medium
capacity digital microwave communication system
Analog microwave communication system
Transmission capacity bit/s/ch)
1950s
1970s
1980s
Late 1990s to now
Note:
Small capacity: < 10M
Medium capacity: 10M to 100M
Large capacity: > 100M
Concept of Digital Microwave Communication
• Digital microwave communication is a way of transmitting digital information in
atmosphere through microwave or radio frequency (RF).
– Microwave communication refers to the communication that use microwave as
carrier .
– Digital microwave communication refers to the microwave communication that
adopts the digital modulation.
– The baseband signal is modulated to intermediate frequency (IF) first . Then the
intermediate frequency is converted into the microwave frequency.
– The baseband signal can also be modulated directly to microwave frequency, but
only phase shift keying (PSK) modulation method is applicable.
– The electromagnetic field theory is the basis on which the microwave
communication theory is developed.
Digital Microwave Communication Modulation (1)
• Digital baseband signal is the unmodulated digital signal. The baseband signal cannot be directly transmitted over microwave radio channels and must be converted into carrier signal for microwave transmission.
Digital baseband signal IF signal
Baseband signal rate
Channel bandwidth
Modulation
Service signal transmitted
Digital Microwave Communication Modulation (2)
• The following formula indicates a digital baseband signal being converted into a digital frequency band signal.
ASK: Amplitude Shift Keying. Use the digital baseband signal to change the carrier amplitude (A). Wc and φ remain unchanged.
FSK: Frequency Shift Keying. Use the digital baseband signal to change the carrier frequency (Wc). A and φ remain unchanged.
PSK: Phase Shift Keying. Use the digital baseband signal to change the carrier phase (φ). Wc and A remain unchanged.
QAM: Quadrature Amplitude Modulation. ). Use the digital baseband signal to change the carrier phase (φ) and amplitude (A). Wc remains unchanged
A*COS(Wc*t+φ)
Amplitude
Frequency
Phase
PSK and QAM are most frequently used in digital
microwave.
Types of Digital Microwave Stations
• Digital microwave stations are classified into Pivotal stations, add/drop relay stations, relay stations and terminal stations.
Terminal station
Terminal station
Terminal station
Pivotal station
Add/Drop relay
stationRelay
station
Types of Relay Stations• a
Relay station
• Back-to-back antenna• Plane reflector
Active
Passive
• Regenerative repeater• IF repeater• RF repeater
Active Relay Station Radio Frequency relay station
An active, bi-directional radio repeater system without frequency shift. The RF relay station directly amplifies the signal over radio frequency.
Regenerator relay station A high-frequency repeater of high performance. The regenerator relay station is used to
extend the transmission distance of microwave communication systems, or to deflect the transmission direction of the signal to avoid obstructions and ensure the signal quality is not degraded. After complete regeneration and amplification, the received signal is forwarded.
Passive Relay Station Parabolic reflector passive relay station
The parabolic reflector passive relay station is composed of two parabolic antennas
connected by a soft waveguide back to back. The two-parabolic passive relay station often uses large-diameter antennas. Meters are
necessary to adjust antennas, which is time consuming.• The near end is less than 5 km away.