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Communications, Signal Processing, and Data Handling
Published in Douglas O. J. deSá, Instrumentation Fundamentals for Process Control, 2019
Amplitude modulation is another method of transmitting data, and to see how this works, let us consider a signal of fixed relatively high frequency and amplitude on which we superimpose another varying signal. The signal of fixed amplitude and frequency is called the carrier frequency. The effect of the imposition of the varying signal on the carrier frequency will be to alter the amplitude of each wave in unison with the varying signal, giving the modulated carrier as in Figure 21.6. On arrival at the receiver, a unit called a demodulator extracts the modulation signal (envelope) from the modified carrier and so obtains the transmitted data. Theoretically, the carrier frequency can be eliminated and just the sideband(s) transmitted, for it does not itself contain any data; however, in practice, a pilot carrier is usually transmitted to facilitate signal recovery at the receiver by synchronizing, i.e., frequency-locking the demodulator. By multiplexing the modulation signal content and/or modulating onto subcarriers multiple signals can be sent. Figure 21.6 may help visualize the idea.
Contemporary Wireless Technologies
Published in G. S. V. Radha Krishna Rao, G. Radhamani, WiMAX, 2007
G. S. V. Radha Krishna Rao, G. Radhamani
Microwave transmission is based on the same principles as radio transmission. The microwave networks require a direct transmission path, high transmission towers, and antennas. Satellite communications are used for a variety of broadcasting applications. The two most popular frequency bands for satellite communications are C-band (frequency range 5.9 to 6.4 GHz for uplink and 3.7 to 4.2 GHz for downlink) and Ku-band (frequency range 14 to 14.5 GHz for uplink and 11.7 to 12.2 GHz for downlink). The radio transmission system consists of a transmitter and a receiver. The main components of a radio transmitter are a transducer, an oscillator, a modulator, and an antenna. A transducer converts the information to be transmitted to an electrical signal. An oscillator generates a reliable frequency that is used to carry the signal. A modulator embeds the voice or data signal into the carrier frequency. An antenna is used to radiate an electrical signal into space in the form of electromagnetic waves. A radio receiver consists of an antenna, an oscillator, a demodulator, and an amplifier. An antenna captures radio waves and converts them into electrical signals. An oscillator generates electrical waves at the carrier frequency that is used as a reference wave to extract the signal. A demodulator detects and restores modulated signals. An amplifier amplifies the received signal that is typically very weak.
S
Published in Carl W. Hall, Laws and Models, 2018
Keywords: astronomy, latitudes, sunspot SPRER, Gustav Friedrich Wilhelm, 1822-1895, German astronomer Sources: Mitton, S. 1973; Thewlis, J. 1961-1964; World Book. 1990. See also HALE SQUARE-CUBE LAW When the dimensions of an object are increased while keeping the shape the same, the area increases as the square of the dimensions, while the volume and mass increase as the cube. Attributed to Galileo Galilei. Keywords: area, dimensions, shape, square, volume, mass GALILEO GALILEI,1564-1642, Italian scientist Sources: de Camp, S. L. 1962; Thewlis, J. 1961-1964. SQUARE LAW DEMODULATOR An electrical device whose output voltage is proportional to the square of its input voltage. A demodulator is used to obtain information from a modulated waveform from the signal imparted to the wave form by a modulator. Keywords: device, modulator, voltage, waveform Source: Considine, D. M. 1976. 1995. See also SQUARE LAW MODULATOR SQUARE LAW MODULATOR An electrical device whose output is proportional to the square of its input. The carrier and modulating signal are added in the input to produce a modulated carrier in the output. Keywords: device, input, modulated, output Source: Considine, D. M. 1976. 1995. See also SQUARE LAW DEMODULATOR SQUARE-ROOT LAW In statistics, the standard deviation of the number of successes divided by the number of trials is inversely proportional to the square root of the number of trials. Keywords: standard deviation, statistics, trials Source: Lapedes, D. N. 1976. 1982. See also INVERSE SQUARE SQUEEZE NUMBER, Sq OR NSq A dimensionless group describing double-squeeze film damping: Sq = 12/pa(r/c)2 where pa r c = = = = = absolute viscosity angular frequency ambient pressure radius unloaded film thickness
Fractional sequential likelihood ascent search detector for interference cancelation in massive MIMO systems in 5G technology
Published in International Journal of Electronics, 2021
Anju V. Kulkarni, Radhika Menon, Pramodkumar H. Kulkarni
Interference is considered as the major problem in the next-generation wireless systems to attain higher throughput. The interference in the signals causes an error or imprecise estimation of the channel for future 5 G transmissions. The main aim of the research is to model a technique that eradicates the interference produced in the massive-MIMO systems. At first, the input signals are transmitted to the encoder for converting the signals from one format to another format. Then, the modulation of the encoded signal is carried out for converting the radio waves by adding information to the signal. The obtained modulated signal is fetched using the transmitting antenna, which helps to transmit the signals and the receiver receives the signals at the receiver side. The obtained modulated signals are demodulated for extracting the original signal from the carrier wave. Finally, the decoding of the signal is done to convert the received signal into codes and is used for recovering the signals sent from the noisy channel. Here, the interference of the signals is eradicated by applying the proposed Fractional-SLAS, which is devised by integrating FC and SLAS algorithm. The proposed interference mitigation method helps to mitigate the interference produced from the signals without any delay or loss of quality of the transmitted signal.