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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.
Principles of Control Algorithm Design for Complex Radar System Functioning at Dynamical Mode
Published in Vyacheslav Tuzlukov, Signal Processing in Radar Systems, 2017
An elementary basic flowchart presenting the subsystems usually found in a radar is shown in Figure 6.1. The transmitter, which is shown here as a power amplifier, generates a suitable waveform for the particular job the radar is to perform. It might have an average power as small as milliwatts or as large as megawatts. The average power is a far better indication of the capability of a radar’s performance than its peak power. Most radars use a short-pulse waveform so that a single antenna can be used on a time-shared basis for both transmitting and receiving. The function of the duplexer is to allow a single antenna to be used by protecting the sensitive receiver from burning out while the transmitter is on and by directing the received echo signal to the receiver rather than to the transmitter. The antenna is the device that allows the transmitted energy to be propagated into space and then collects the echo energy on receiver. It is almost always a directive antenna, one that directs the radiated energy into a narrow beam to concentrate the power as well as to allow the determination of the direction of the target. An antenna that produces a narrow directive beam on transmit usually has a large area on receive to allow the collection of weak echo signals from target. The antenna not only concentrates the energy on transmit and collects the echo energy on receive but it also acts as a spatial filter to provide angle resolution and other capabilities.
Radar Systems - Basic Concepts
Published in Bassem R. Mahafza, Introduction to Radar Analysis, 2017
Figure 4.1 shows a simplified pulsed radar block diagram. The time control box generates the synchronization timing signals required throughout the system. A modulated signal is generated and sent to the antenna by the modulator/transmitter block. Switching the antenna between the transmitting and receiving modes is controlled by the duplexer. The duplexer allows one antenna to be used for both transmit and receive. During transmission it directs the radar electromagnetic energy towards the antenna. Alternatively, on reception, it directs the received radar echoes to the receiver. The receiver amplifies the radar returns and prepares them for signal processing. Extraction of target information is performed by the signal processor block. The target’s range, R, is computed by measuring the time delay, Δt, that it takes a pulse to travel the two-way path between the radar and the target. Since electromagnetic waves travel at the speed of light, c = 3 × 108m/second, then () R=(cΔt)/2
Interference Cancellation in Wireless Communications: Past, Present, and Future
Published in IETE Journal of Education, 2022
S. M. Zafaruddin, Pranay Bhardwaj
Technically, radios are half-duplex systems that transmit and receive signals simultaneously using TDD or FDD duplexing techniques. Full duplexing allows the system to transmit and receive on the same time-frequency resource doubling the spectral efficiency compared with half-duplex methods [22]. The major impediment to the practical implementation of full-duplex communication is self-interference when the receiver picks the signal transmitted by its own transmitter. The signal received directly from the transmitter has a very high power due to the proximity of the transmitter in comparison to the desired far-end signal. Notwithstanding the knowledge of the transmitted signal, the self-interference cancelation is challenging since the known signal gets transformed to an entirely new signal when received as the self-interference. The last few years have witnessed breakthroughs in self-interference cancelation for full-duplex radios for terrestrial wireless systems using combined analog and digital methods. It should be mentioned that echo canceler for the interference signal caused at the hybrid circuit for the telephone system and digital subscriber lines (DSL) is already implemented for practical applications [23, 24].