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SIMULATION OF HYBRID ELECTROMAGNETIC SYSTEM
Published in Wenquan Sui, Time-Domain Computer Analysis of Nonlinear Hybrid Systems, 2018
Data sequence dk(t)is a bipolar pulse with values of +1 and -1, representing binary 1 and 0, respectively. For minimum phase change, square pulse for +1 and -1 are modified with sinusoidal pulses, the middle sinusoidal terms in (9.4), as shown in the example of Figure 9-24. The I-Q data sequences are thereafter modulated by a set of orthogonal high-frequency signals, sin(0t) and cos(0t) here, for transmission. The modified I-Q sequences have uniform magnitudes of +1V and -1V and the signal phase would be discontinuous only when the data bit changes from 1 to 0 or from 0 to 1. Signal modulation is for radio systems efficiently transmitting information, either voice or data, to another location. For a receiving system, the signal processing flow is reversed compared to the transmitting one. Modulated signals, carrying voice or data information, are received and then demodulated to get the original I-Q sequences. Through some mathematical derivations, orthogonal signals are selected in modulation for optimal detection and least error performance. In practical communication systems, the modulation and demodulation design processes are much more complicated; interested readers can find many good references on the topic.
Modulation Methods
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Modulation is the process whereby message information is embedded into a radio frequency carrier. Message information can be transmitted in the amplitude, frequency, or phase of the carrier, or a combination thereof, in either analog or digital format. Analog modulation schemes include amplitude modulation (AM) and frequency modulation (FM). Analog modulation schemes are still used today for broadcasting AM/FM radio, but all other communication and broadcast systems now use digital modulation. Digital modulation schemes transmit information using a finite set of waveforms and have a number of advantages over their analog counterparts. Digital modulation is a natural choice for digital sources, for example, computer communications. Source encoding or data compression techniques can reduce the required transmission bandwidth with a controlled amount of signal distortion. Digitally modulated waveforms are also more robust to channel impairments such as delay and Doppler spread, and cochannel and adjacent channel interference. Finally, encryption and multiplexing is easier with digital modulation schemes.
Modulation
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
A prominent use of modulation techniques is found in communication systems. The extremely long wavelengths of electromagnetic waves at frequencies found in a typical audio signal make direct transmission impractical, because of constraints on realistic antenna size and bandwidth. Successful radio communication is made possible by using the original audio (baseband) signal to modulate a carrier signal of a much higher frequency and transmitting the modulated carrier by means of antennas of feasible size. Another example formerly in widespread use is that of modems used to transmit digital data through the telephone network. Digital data are not directly compatible with analog local subscriber connections, but audible signals modulated by digital data could be carried over local telephone lines. Instrumentation systems use modulation techniques for telemetry (where the distances may be on the order of centimeters for implanted medical devices to hundreds of millions of kilometers for deep-space probes), for processing signals in ways for which the original signals may be unsuited (such as avoiding 1/f noise in high-gain amplifiers by processing a high-frequency carrier modulated by a low-frequency signal), and for specialized amplification purposes (carrier and lock-in amplifiers).
Performance improvement of antenna array element for mobile communication
Published in Waves in Random and Complex Media, 2023
Use of a broad band micro strip antenna with a T shape structure for the reasons mentioned above is one of the most promising methods that have been described. The CST software may be used to create a desired radiation pattern and current distributions, as well as conduct a thorough investigation of a Ku band T-shaped antenna design. The antenna is one of the most crucial parts of low-profile wireless communication. To broadcast and receive antenna information, modulation is utilized, in which a career wave is overlaid over a modulating signal. The modulated signal was then received at the intended location, and the original information stream was recovered via demodulation. Patch antennas are narrowband antennas that have a wide beam width. It's manufactured by etching the antenna element design into a metal trace attached to an insulating dielectric substrate, similar to a printed circuit board, with a continuous metal layer connected to the other side of the substrate as a ground plane. Using fractal geometry, patch antennas are reduced in size. Fractal geometries have two common properties: space filling and self-similarity. When you apply fractal geometry, you may find self-repeating structures. When fractal geometry is applied to the antenna, the size of the patch reduces, the resonant length rises, and the number of frequency bands increases.
A Bus Clamping PWM-Based Improved Control of Grid Tied PV Inverter with LCL Filter Under Varying Grid Frequency Condition
Published in IETE Journal of Research, 2023
The main purpose of the PWM is to reduce the THD and switching loss [31–37]. By the use of suitable PWM technique, we can have a linear control of the inverter output voltage and frequency. Bus clamping PWM is a discontinuous PWM method. It can be subdivided into continual clamp and split clamp PWM [36]. It is an advanced form of Space vector PWM technique. There are some advantages of using 60° Bus clamping PWM ahead of other conventional PWM techniques. In case of Sine PWM, the maximum DC bus utilization voltage is 0.5VDC but in case of Space Vector PWM and advanced space vector based bus clamping PWM, the maximum DC bus utilization voltage is 0.58 VDC [38]. It also provides better performance at higher modulation index. The switching loss in bus clamping PWM also get reduced as compared to conventional space vector PWM as the switching loss is during clamping period of specific phase [34]. Moreover, at higher modulation index the dominant component of harmonic present in the line voltage gets shifted by 0.5 times of the average switching frequency (fs) as compared to conventional space vector PWM. Advanced space vector based bus clamping PWM has all the facilities of the SPWM and can control the fundamental voltage, reduce the pulsating torque and heating to a huge extent [39,40].
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.