T değerine periyod ve f=1/t (Hz=1/sec) peryodun tersinede frekans denir. Peryod: Bir x(t) analog işarette x(t+t)=x(t) olacak şekilde T positif bir sayı ise Bu işaret peryodiktir. Bir işaretin alt frekansı =f1, üst frekansı=f2 ise işaretin band genişliği BW=f2-f1 dir. Frekans spektrumunda işaretin başladığı ve bittiği frekans aralığı bant genişliğini verir. O nedenle frekans domaininde analiz edilir. Analog işaret, çok sayıda frekans bileşiminden oluştuğundan zaman domeninde analiz etmek zordur. Frekans, bir sinyalde sürekli tekrarlanan temel benzer parçadır. Frekans, bir saniyedeki titreşim sayısıdır. Farklı sinüsoidal dalgalarının toplamından oluşur. 8ĩ Analog işaret Analog işaret, genliği, frekansı ve fazı zamanla değişen işarettir. In communication systems, it is commonly used periodic analog signals and nonperiodic digital signals. Analog signals can have an infinite number of values in a range digital signals can have only a limited number of values. Digital data have discrete states and take discrete values. Analog data are continuous and take continuous values. 7Ĩ Analogue & Digital Signals Data can be analog or digital. An On/Off light switch applies a fixed, predetermined voltage. Digital signals : A digital signal is a discrete time signal, binary signal. These properties define a large class of tractable, useful signals and will be further considered in the coming lectures 5Ħ Even signal f ( t) f ( t) t odd signal f (t) f ( t) f ( t) t 6ħ Types of Signals Analog signals: An analog signal is a continuous signal and is often represented by a V(t). A step signal is zero up to a certain time, and then a constant value after that time, u(t). Step and pulse signals: A pulse signal is one which is nearly completely zero, apart from a short spike, d(t). A signal is (complex) exponential if it can be represented in the same form but C and a are complex numbers. Exponential and sinusoidal signals: a signal is (real) exponential if it can be represented as x(t) = Ce at. Examples are cos(t) and sin(t) signals, respectively. it can be reflected in the axis at zero). Even and odd signals: a signal is even if x(-t) = x(t) (i.e. Mathematically, signals are represented as a function of one or more independent variables Electrical signals Voltages and currents in a circuit Acoustic signals Acoustic pressure (sound) over time Mechanical signals Velocity of a car over time Video signals Intensity level of a pixel (camera, video) over time 4ĥ Signal Properties Periodic signals: a signal is periodic if it repeats itself after a fixed period T, i.e. Cahit Karakuş, 2019Ģ İçerik Sinyaller Sistemler Temel Analog Sinyaller Sayısal Sinyaller Sayısal İletim Modları Kanal Kapasitesi Haberleşme Ağının Performansı Transmisyon Değerlendirmesi Haberleşme Sinyalleri Elektromanyetik Sinyaller 2Ĥ Sinyal Nedir? Signals are variables that carry information.
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