The field of Affective Computing AC expects to narrow the communicative gap between the highly emotional human and the emotionally challenged computer by developing computational systems that recognize and respond to the affective states of the user. Affect-sensitive interfaces are being developed in number of domains, including gaming, mental health, and learning technologies. Emotions are part of human life. Recently, interest has been growing among researchers to find ways of detecting subjective information used in blogs and other online social media.
Types[ edit ] Three types of synthesizer can be distinguished. The first and second type are routinely found as stand-alone architecture: The third type are routinely used as communication system IC building-blocks: One of its big advantages is to allow a much finer resolution than other types of synthesizers with a given reference frequency.
Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. February Learn how and when to remove this template message Prior to widespread use of synthesizers, in order to pick up stations on different frequencies, radio and television receivers relied on manual tuning of a local oscillatorwhich used a resonant circuit composed of an inductor and capacitoror sometimes resonant transmission lines; to determine the frequency.
The receiver was adjusted to different frequencies by either a variable capacitor, or a switch which chose the proper tuned circuit for the desired channel, such as with the turret tuner commonly used in television receivers prior to the s. However the resonant frequency of a tuned circuit is not very stable; variations in temperature and aging of components caused frequency driftcausing the receiver to drift off the station frequency.
Automatic frequency control AFC solves some of the drift problem, but manual retuning was often necessary.
Since transmitter frequencies are stabilized, an accurate source of fixed, stable frequencies in the receiver would solve the problem. Quartz crystal resonators are many orders of magnitude more stable than LC circuits and when used to control the frequency of the local oscillator offer adequate stability to keep a receiver in tune.
However the resonant frequency of a crystal is determined by its dimensions and cannot be varied to tune the receiver to different frequencies.
One solution is to employ many crystals, one for each frequency desired, and switch the correct one into the circuit. This "brute force" technique is practical when only a handful of frequencies are required, but quickly becomes costly and impractical in many applications.
Cable television can support even more frequencies or channels over a much wider band. A large number of crystals increases cost and requires greater space. The solution to this was the development of circuits which could generate multiple frequencies from a "reference frequency" produced by a crystal oscillator.
This is called a frequency synthesizer. The new "synthesized" frequencies would have the frequency stability of the master crystal oscillator, since they were derived from it.
Many techniques have been devised over the years for synthesizing frequencies. Some approaches include phase locked loopsdouble mix, triple mix, harmonic, double mix divide, and direct digital synthesis DDS.
The choice of approach depends on several factors, such as cost, complexity, frequency step size, switching rate, phase noiseand spurious output. Coherent techniques generate frequencies derived from a single, stable master oscillator.
In most applications, a crystal oscillator is common, but other resonators and frequency sources can be used. Incoherent techniques derive frequencies from a set of several stable oscillators.
Synthesizers used in commercial radio receivers are largely based on phase-locked loops or PLLs. Many types of frequency synthesizer are available as integrated circuitsreducing cost and size. High end receivers and electronic test equipment use more sophisticated techniques, often in combination.
System analysis and design[ edit ] A well-thought-out design procedure is considered to be the first significant step to a successful synthesizer project. Crawford says that these are mutually contradictive requirements. Gardner his Phaselock techniques  and by Venceslav F. Kroupa his Frequency Synthesis.
Variable-frequency synthesizers, including DDSare routinely designed using Modulo-N arithmetic to represent phase.
Principle of PLL synthesizers[ edit ] See main article:A Fully Integrated Fractional-N Frequency Synthesizer for Wireless Communications A Thesis Presented to The Academic Faculty By Han-Woong Son. Nokia Bell Labs (formerly named AT&T Bell Laboratories and Bell Telephone Laboratories) is an industrial research and scientific development company, owned by Finnish company initiativeblog.com headquarters are located in Murray Hill, New Jersey, in addition to other laboratories around the rest of the United States and in other countries..
The historic laboratory originated as the Western Electric. International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research. A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single reference frequency.
Fractional N dividers are readily available. Practical considerations.
Philips TDATT - 5 V mixer/oscillator and low noise PLL synthesizer for hybrid terrestrial tuner. To the Graduate Council: I am submitting herewith a thesis written by Timothy R.
Grundman entitled "Design and Analysis of a Delta Sigma Modulator for a Fractional N Phase Locked Loop Frequency Synthesizer Operating at Poly-Phase Fractional-N Frequency Synthesizer Andrey Martchovsky June Abstract The aim of this thesis is to present a phase-hopping frequency synthe-.