VSAT Block Diagram : Working Operation and Functions of VSAT Terminal Subsystem

A VSAT system is designed to provide communication via satellite, typically used in remote or rural areas where traditional communication infrastructure is not available. It enables reliable data, voice, and video transmission for various applications such as broadband Internet, private network services, and remote monitoring. The VSAT terminal consists of several subsystems, each playing a vital role in the overall operation. Below is a detailed explanation of the VSAT block diagram and the functions of each subsystem:

VSAT terminal composed of communication equipments and small antenna of diameter about 3.5 meter or 4.5 meter. Typically VSAT intallation requires following items:
• Outdoor Unit (RF Transceiver, RF LNA, RF Power Amplifier, Antenna, OMT (Orthomode transducer) feed horn)
• Indoor Unit (Satellite modem, MUX, telephone or data connection interface cards)
• Link cable between indoor and outdoor units.


VSAT Terminal block diagram

Figure depicts VSAT terminal block diagram. Here MAX acts as baseband interface for FAX, Data terminal, telephone etc. VSAT terminal is a part of large network which is managed by Hub station at central place. It has all the intelligence to operate, maintain and configure all the VSAT terminals. Customer database is maintained at the Hub station for billing purpose.

Hub station is also like VSAT terminal. It houses RF equipment, VSAT interface circuitry, user interfaces etc.

Let us understand VSAT terminal operation:
• VSAT is a two way communication and hence one frequency pair (or two frequencies) are needed for establishing connection. It is also referred as duplex communication.
• Modern VSATs uses FDMA/TDMA/CDMA/DAMA based access techniques for communication.
• VSAT terminal is broadly classified into baseband part and RF part.
• Baseband part consists of modem (modulator, demodulator), EDU (Encryptor, Decryptor) , Mux/Demux and data/voice connection circuitry.
• RF part consists of antenna, Rf Power amplifier, RF LNA, frequency converters (up converter and down converter).
➨ Refer VSAT System Overview➨

How VSAT Works

Following are the functions performed by vsat sub systems in transmission path.
➨The digital data from the user’s device is sent to the modem, where it is modulated into an IF signal.
➨The IF signal is sent to the BUC via the interconnecting cable. The BUC converts the IF signal to the desired RF frequency and amplifies it.
➨The RF signal is then transmitted to the feed horn and directed by the parabolic dish to the satellite in the sky.
Following are the functions performed by vsat sub systems in reception path.
➨The satellite receives the signal and retransmits it back to the ground station or another VSAT terminal.
➨The LNB captures the RF signals from the satellite, amplifies them, and downconverts them to an IF signal.
➨The IF signal is sent to the modem in the IDU, where it is demodulated back into digital data for the user.

VSAT Terminal Vendors

Following table mentions manufacturers or Vendors of VSAT terminal equipments used in VSAT based network.

VSAT Terminal manufacturers or vendors
Viasat
Vizocom
Satellite Engineering Group, Singapore
Paradise, UK
Mitec Telecom
Direct
Hughes Network Systems
Gilat
Comtech EF Data, USA
Comsys, UK
Codan, Australia
Avsatcom

Conclusion

The operation of the VSAT system involves the integration of these subsystems to provide seamless two-way communication via satellite links. This setup allows VSAT to support a wide range of applications, such as Internet access, corporate intranets, SCADA, and video conferencing, making it an essential tool for connecting remote and underserved locations.

VSAT RELATED LINKS