Question

choose the correct answer

1-

The spectrum of analog signals is: *

Discrete and repeated every Fs

Continuous and repeated every Fs

Discrete and not repeated

Continuous and not repeated

2-For the following Matlab code, how many tones are going to be played by (sound) instruction? *

4

5

6

2

1

3

3-

In Assembly language, to print any number between 0 and 9 on screen using (INT 21h), you need to: *

Subtract 30h from the number and put it in DL

Subtract 30h from the number and put it in AL

Add 30h to the number and put it in AL

Add 30h to the number and put it in DL

4-

When writing a function in Matlab, only one of the following is correct: *

The function can be called only one time in the main program

The outputs should not be given a value in the function

The m-file containing the function should carry the function name

The inputs should not be more than the outputs

Answer 1

(1)

Signal is usually represented in time domain or frequency domain. Signals carry data in the form of electromagnetic waves from one point to another.

Analog signal

Analog signal is the signal which is continous time varying signal represented by amplitude, time period or frequency and phase. Analog signals are in the form of sine waves. There are simple analog signals and composite analog signals. Simple analog signal is simple the sine wave and it cannot be decomposed whereas composite analog signal can be decomposed to many sine waves. The analog signal values are not limited.  

For example.

is an analog signal with Amplitude A and frequency f Hz.  

Digital signal  

Digital signals are non continous or discrete signals which carry data. Digital signals are in the form of square waves. Digital signals carry data in the form of 1's and 0's that is in the binary form. Digital signal is also represented by amplitude, frequency and phase. The values for digital signal is limited. The signal behaviour is specified with respect to the bit rate and bit intervel. Bit rate is the number of bits transmitted per unit time and bit interval is the time taken to transmitt one bit.

Spectrum

Signals can be represented as a function of the frequencies that make up the signal. This is called the spectrum. The spectrum displays the amplitude (and phase) as a function of the frequency of the sinusoidal components that make up the signal.

The analog signal can be represented as the sum of sinusoidal components as,  

  

Therefore,  

Let   

Therefore,

So inorder to find the sprectrum represent x(t) in the frequency domain.  

The spectrum will be,  

So the analog signal spectrum is discrete and repeated.