Analog And Digital Modulation Pdf

File Name: analog and digital modulation .zip
Size: 16415Kb
Published: 17.04.2021

Digital Modulation Techniques

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer.

In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. In conventional communications systems, information is transmitted by modulating the frequency, amplitude or phase of the carrier signal, which often occurs in a binary fashion over a very narrow bandwidth. Recently, ultra-wideband signal transmission has gained interest for local communications in technologies such as autonomous local sensor networks and on-chip communications, which presents a challenge for conventional electronics.

Spin-torque nano-oscillators STNOs have been studied as a potentially low power highly tunable frequency source, and in this report we expand on this to show how a specific dynamic phase present in vortex-based STNOs makes them also well suited as Wideband Analogue Dynamic Sensors WADS.

This multi-functionality of the STNOs is the basis of a new modulation and demodulation scheme, where nominally identical devices can be used to transmit information in both a digital or analogue manner, with the potential to allow the highly efficient transmittance of data. Spin torque nano-oscillators STNOs are nanoscale tunable multifunctional radio-frequency devices which have been proposed for a diverse variety of applications 1 , ranging from wireless communications 2 , 3 , 4 , 5 , 6 , to nanoscale magnetic field detectors for magnetic hard drive read heads 7 , 8 and bio-sensors 9 and more recently the building blocks of novel bio-inspired computing architectures for neuromorphic computing 10 , 11 , 12 , 13 , With the emergence of the Internet of Things and the realisation of smart industries, cities etc.

STNOs have been proposed for a range of different components of high frequency technologies, from rf signal generation 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 and detection 25 , 26 , 27 , 28 , 29 , to rectification 30 , 31 and mixing 32 , 33 , STNOs have many key strengths which include i multi-functionality 1 , ii scalability 35 , iii tunability 15 , 16 , 17 , iv coupling either via dipolar coupling 36 , spin waves 37 or electrical 38 , 39 , 40 , 41 and v capacity for integration with CMOS technologies.

An STNO usually consists of a magnetic tunnel junction MTJ , with free and fixed magnetic layers separated by an insulating layer, and where the free layer oscillates at high frequencies due to either a dc current, via the spin-transfer torque effect 42 , 43 , or a resonant radio-frequency current 30 or magnetic field 44 , 45 , The magnetisation of the free layer impacts significantly the nature of the resultant dynamics, depending upon whether the free layer is homogeneously in-plane 42 , 43 or non-homogenous i.

In this report we propose a fully spintronic modulation and demodulation scheme, with two nominally identical STNOs, one of which is operating as a variable ac source, which can modulate the information to n possible frequency states by tuning an external parameter i , and the other of which is a broadband frequency to voltage converter which is capable of demodulating the signal, shown schematically in Fig. The modulation and demodulation scheme presented in Fig.

Whilst this type of communications paradigm might be impractical for wireless communications which are heavily restricted to relatively narrow bands i. As STNOs are inherently analogue devices, there are two possibilities for this modulation and demodulation transmission scheme: digital or analogue. If the external input parameter, i , has M discrete values, then an alphabet of M characters can be digitally sent via the carrier frequency, known as M-ary shift keying i.

However, conversely, the input parameter can be varied in a continuous manner, and information can be modulated in an analogue fashion onto the carrier signal. There are distinct advantages to both digital and analogue modulation and the final choice of which scheme is more relevant depends largely on the targeted application.

Analogue modulation makes good use of bandwidth and can efficiently transmit information accurately, but is also in general less tolerant of noise. Digital modulation requires some level of synchronisation and is less efficient, however is in general more tolerant to low levels of noise and is more compatible with existing wireless technologies.

In Fig. The devices are identical to those presented previously in refs. Similar trends were observed for all values of RxA. The magnetisation of the reference layer 2. After switching occurs the magnetisation is in a C-state see micromagnetic simulation as insets in Fig.

A current passing across the antenna will produce a predominantly in-plane magnetic field across the MTJ collinear with the magnetisation direction of the reference layer. S I1 in the supplementary information. It is important to note that in Figs. Voltage measured experimentally a , c , e , g and the magnetisation component collinear to the reference layer m y from micromagnetic simulations b , d , f , h as a function of time for different excitation strengths.

Typical trajectories of the vortex core calculated from the micromagnetic simulations are presented, where A and B are the point of core expulsion and renucleation, respectively.

The insets in c show example time traces, where the free layer is transitioning between the vortex green and QUP blue states. When a radio-frequency signal arrives to the integrated field line antenna, it will result in a dynamic response from the free layer of the MTJ, the nature of which depends on the frequency and power of the incoming signal.

The trajectory of the vortex core calculated from the micromagnetic simulations is presented on the far right of the figure. In all the data shown in Fig. There is qualitatively a close agreement between the experimental results and the simulations about the behaviour of the magnetisation of the free layer.

For the relatively low excitation i. As the excitation strength is increased i. At these low excitation strengths, this effect is strongly hysteretic and after the vortex expulsion, the free layer remains stable in the QUAP state. As the excitation strength is further increased i. When the vortex core is renucleated position B the orbit is initially destabilised but gradually stabilises with time before the vortex core reaches the edge of the nanopillar and is re-expelled position A , and this cycle continues with time in a relatively stochastic manner, switching back and forth between the two states.

When the excitation strength is increased even more i. The dynamical state diagram is presented experimentally by measuring the average resistance i. A good qualitative agreement between the experimental data and the simulations can be seen in terms of the system behaviour. The positions 1—4 are labelled, indicating the regions of different dynamic behaviour as a function of incoming frequency and power i.

The free layer is initially in the vortex state and an rf signal is passed across the antenna at a fixed frequency, and the strength of the signal is swept from low to high.

The first obvious feature of the dynamical state diagram is the transition from the vortex state to the QUAP state i. This hysteretic transition, corresponding to the behaviour discussed in Fig. Within this region of continual state transitions, the amount of time the free layer spends in either the QUAP state or the vortex state is strongly dependent on the excitation signal.

In this region, the time averaged magnetisation, and therefore the resistance via the tunnelling magnetoresistance effect, is strongly dependent on the frequency and amplitude of the excitation signal. If over a certain frequency or power range, it is possible to find a one-to-one relation in the resistance for a specific frequency or power, this can be used to identify the incoming dynamic state of a signal i. Instead of using an rf source as in Fig. A variable dc current is applied to MTJ source , which generates a tunable high frequency signal which is amplified and passed across the integrated field line antenna above MTJ detector , shown schematically in Fig.

The free layer is initially in the vortex state, and when the current in MTJ source is increased there is an initial decrease in resistance as the vortex is expelled and the free layer enters the quasi-uniform parallel QUP state note: the free layer enters either the QUAP or QUP state depending solely on the direction of the dc field produced by the field line antenna, which in this case is positive. The insets in Fig. The average resistance of MTJ detector depends on the relative amount of time the free layer spends in either magnetisation state, and as the frequency and power of the signal generated by MTJ source increase, there is a corresponding change in the dynamic behaviour of the free layer of MTJ detector.

Initially the free layer starts to transition between the QUP state and the vortex state infrequently, and as such the average resistance is closer to the QUP state. As I MTJS is further increased, however, the number of transitions between the QUP and vortex states starts to increase and the average resistance increases quasi-linearly.

An important aspect of many wireless communications systems is shift-keying, where information can be encoded into the frequency, amplitude or phase of a radio frequency signal 50 , Shift-keying has been demonstrated previously with STNOs 3 , 4 but without an integrated means of demodulating the signal and thus de-encoding the information. An arbitrary waveform generator AWG can apply either distinct digital voltages or a ramped continuous variation of the voltage to the MTJ source over a fixed period of time.

This results in either digital or analogue encoding of the information to the carrier signal. This signal is amplified and sent to the field line antenna of an adjacent and nominally identical nanodevice which demodulates the data.

The voltages applied by the arbitrary waveform generator are quasi-dc so that they would be filtered by the bias tee, and not be sent to the MTJ detector. There is significant perspective for improvement for both MTJ detector and MTJ source , in terms noise and modulation and demodulation speed in order to increase the relative data rate.

With respect to the transmission scheme discussed in Fig. Due to the analogue frequency and power dependence of the resistance of MTJ detector , discussed in Fig.

The effective data rate in Fig. In conclusion, we explore the magnetisation dynamics generated in vortex-based STNOs when excited by large radio-frequency magnetic fields, and show how this makes them exciting candidates as wideband analogue dynamic sensors.

Furthermore, we demonstrate an STNO-based digital and analogue modulation and demodulation transmission scheme using two nanoscale nominally identical magnetic tunnel junctions, with one acting as a highly tunable frequency source and the other as a wideband analogue dynamic sensor.

The data that support the findings of this study are available from the corresponding author upon request. Locatelli, N. Spin-torque building blocks. Choi, H.

Spin nano—oscillator—based wireless communication. Google Scholar. Manfrini, M. Frequency shift keying in vortex-based spin torque oscillators.

Ma, R. Spin torque oscillator based BFSK modulation. Ruiz-Calaforra, A. Sharma, R. Modulation rate study in a spin-torque oscillator-based wireless communication system. IEEE Trans. Sato, R. Simulations and experiments toward high-data-transfer-rate readers composed of a spin-torque oscillator. Braganca, P. Nanoscale magnetic field detection using a spin torque oscillator. Nanotechnology 21 , Fried, J. Nanoparticle-modified magnetic vortex dynamics.

IEEE Magn. Grollier, J. Spintronic nanodevices for bioinspired computing. IEEE , — Nikonov, D. Coupled-oscillator associative memory array operation for pattern recognition.

ANALOG & DIGITAL MODULATION TECHNIQUES: AN OVERVIEW

Modulation is the process of converting data into electrical signals optimized for transmission. Modulation techniques are roughly divided into four types: Analog modulation, Digital modulation, Pulse modulation , and Spread spectrum method. This method is divided into single carrier modulation, by which the carrier occupies the entire bandwidth i. In addition, there is a pulse modulation technique used to change the pulse width and spread spectrum method that spreads the signal energy over a wide band. In wireless communication, information is transmitted by encoding voice and data on radio waves of certain frequencies. This technique utilizes the difference in the amplitude of analog signals to modulate digital signals by switching between low frequency and high frequency in order to represent 0 and 1.

To begin with, this chapter quite generally creates a basis for an approach to the digital modulation methods. Following this chapter, it would also be possible to continue e. Experts, of course can simply skip this chapter. Unable to display preview. Download preview PDF. Skip to main content. This service is more advanced with JavaScript available.


Analog and digital modulation pdf. For people without a background in electrical engineering, understanding the finer details of analog and digital modulation.


ANALOG AND DIGITAL MODULATION TECHNIQUES Assignment 1

In electronics and telecommunications , modulation is the process of varying one or more properties of a periodic waveform , called the carrier signal , with a separate signal called the modulation signal that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone , a video signal representing moving images from a video camera , or a digital signal representing a sequence of binary digits, a bitstream from a computer. The carrier is higher in frequency than the modulation signal. The purpose of modulation is to impress the information on the carrier wave, which is used to carry the information to another location. In radio communication the modulated carrier is transmitted through space as a radio wave to a radio receiver.

ANALOG & DIGITAL MODULATION TECHNIQUES: AN OVERVIEW

To browse Academia.

Basic Principles of Digital Modulation

Digital-to-Analog signals is the next conversion we will discuss in this chapter. These techniques are also called as Digital Modulation techniques. Digital Modulation provides more information capacity, high data security, quicker system availability with great quality communication. Hence, digital modulation techniques have a greater demand, for their capacity to convey larger amounts of data than analog modulation techniques.

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Laboratory implementation of some analog and digital modulation schemes using single circuit Abstract: In this work we present laboratory implementation of some experiments in the domain of Analog and Digital Communication. In addition, the same circuit is used to generate natural sampled waveform and the two-channel time division multiplexed waveform.

Modulation Methods

FSK – Frequency Shift Keying

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. In conventional communications systems, information is transmitted by modulating the frequency, amplitude or phase of the carrier signal, which often occurs in a binary fashion over a very narrow bandwidth. Recently, ultra-wideband signal transmission has gained interest for local communications in technologies such as autonomous local sensor networks and on-chip communications, which presents a challenge for conventional electronics.

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Pandey and K. Pandey , K. Pandey Published Engineering. Wireless communications has become one of the fastest growing areas in our modern life and creates enormous impact on nearly every feature of our daily life.

Modulation is the process of varying one or more parameters of a carrier signal in accordance with the instantaneous values of the message signal. The message signal is the signal which is being transmitted for communication and the carrier signal is a high frequency signal which has no data, but is used for long distance transmission. There are many modulation techniques, which are classified according to the type of modulation employed. A signal is pulse code modulated to convert its analog information into a binary sequence, i. The output of a PCM will resemble a binary sequence.

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity.

Though based on the same concepts, digital-modulation waveforms look quite different from their analog counterparts. Though far from extinct, analog modulation is simply incompatible with a digital world. We no longer focus our efforts on moving analog waveforms from one place to another.

Со всех сторон открывались ворота, и люди вливались в поток. Колокола звонили где-то совсем рядом, очень громко. Беккер чувствовал жжение в боку, но кровотечение прекратилось.

2 Response
  1. Jay B.

    Material science for dummies pdf ignore everybody and 39 other keys to creativity pdf free download

Leave a Reply