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.