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Green Microwave and Satellite Communication Systems
Published in Gurjit Kaur, Akanksha Srivastava, Green Communication Technologies for Future Networks, 2023
Divya Sisodiya, Yash Bahuguna, Akanksha Srivastava, Gurjit Kaur
A transponder is an electronically controlled automatic device that transmits a received signal at various receiving, monitoring, amplifying, and retransmitting frequencies. It is mainly used for wireless communication. The word “sender” consists of two words: transmitter and transponder. Satellite communication channels are also called receivers because each channel is a separate transceiver or repeater. The transponder is not a single unit. It is composed of the duplexer, bandpass filter, broadband receiver, power amplifier, De-Mux in and Mux out, as shown in Figure 13.6. The duplexer is used to allow simultaneous transmission and reception. The duplexer is a bidirectional microwave gate that allows to receive the carrier signal from the antenna and transmit the carrier signal to the antenna. A basic bandwidth of 500 MHz is provided at C-band frequencies in the input link frequency range of 5.925 to 6.425 GHz. To reduce noise and interference, these frequencies are routed via a broadband bandpass filter (BPF). After that, it moved to a broadband receiver to give all channels with common frequency down conversion.
On-site Investigation
Published in Koji Fukuoka, Safer Seas, 2019
AIS is a shipboard broadcast transponder system where vessels continually send the ship’s name, position, course, speed and other data to all other nearby vessels and shore authorities on a common VHF radio channel. AIS messages include static data which is programmed at the time of setting up AIS units, dynamic data and voyage related data. The static data involve maritime mobile service identity (MMSI), IMO number, length and beam, type of ship and location of position fixing antenna on ship by aft of bow, port or starboard of center line. The dynamic data are derived from interfaces with the ship’s GPS and other sensors, and involve the ship’s position, date and time, speed over ground (SOG), course over ground (COG), heading, navigational status and rate of turn. Voyage-related data is entered manually by the crewmember, and includes the ship’s draft, hazardous cargos, destination and estimated time of arrival.
Satellite communications
Published in J. Dunlop, D. G. Smith, Telecommunications Engineering, 2017
In FDMA the bandwidth can be divided on a multi-carrier or single carrier basis. In multi-carrier the transponder bandwidth is divided into sub-bands, each sub-band being assigned to an earth station. The sub-bands need not be all of the same width; the number of channels in each will depend on the earth station’s requirements and the allocation they have been given. This arrangement gives the earth station some flexibility in the allocation of bandwidth within its own sub-band. The main disadvantage of this type of access is that the power output from the transponder must be reduced compared with the output that could be achieved with a single carrier arrangement. Except for a few satellites using solid-state amplifiers, the output device at the transponder is normally a travelling wave tube. It has a non-linear input–output characteristic, and this leads to serious inter-modulation products in the output. This effect becomes more serious as the number of carriers increases. To avoid the non-linearities from producing serious degradation on the output signal, it is necessary to impose an input back-off. This back-off has to be large enough to ensure that the output back-off brings the operating point to a position where the inter-modulating products are insignificant. The nonlinear characteristic means, of course, that the output back-off will be smaller than the input back-off, Fig. 14.11. The amount of back-off required increases with the number of carriers in the system.
Product development, fashion buying and merchandising
Published in Textile Progress, 2022
Rachel Parker-Strak, Rosy Boardman, Liz Barnes, Stephen Doyle, Rachel Studd
The 21st century is steadily becoming the age of The Internet of Things (IoT). The IoT is underpinned by the notion that all the products that people interact with should be interconnected, and that they should exist to make people’s lives easier, fitting into their lifestyle (Roncha, 2019). The IoT is reflected in products being embedded with Quick Response (QR) codes or Radio-frequency identification (RFID) tags (Roncha, 2019). RFID uses radio waves to identify and track products with an RFID tag (a transponder carrying information) and a reader (a device that receives signals from the tag) (BoF, 2022). The deployment of RFID in the fashion supply chain enables access to real-time product information anywhere along the network, supporting the objectives of supply-chain management in this challenging context (Azevedo & Carvalho, 2012). Thus, RFID can be used to track products and orders in real time, helping fashion retailers address issues such as counterfeiting or improve recycling and inventory management (BoF, 2022). For instance, Mulberry are now fitting all their products with digital tags to ensure that they can be verified as genuine at the resale stage (Drapers, 2022).