Signals And System

Prereqisting Discussion

A Signal is defined as any physical quantity that changes with time, distance, speed, position, pressure, temperature or some other quantity. A Signal is physical quantity that consists of many sinusoidal of different amplitudes and frequencies.

A System is a physical device that performs an operations or processing on a signal. Ex Filter or Amplifier.

Classification Of Signal Processing

1) ASP (Analog signal Processing) : If the input signal given to the system is analog then system does analog signal processing. Ex Resistor, capacitor or Inductor, OP-AMP etc

2) DSP (Digital signal Processing) : If the input signal given to the system is digital then system does digital signal processing. Ex Digital Computer, Digital Logic Circuits etc. The devices called as ADC (analog to digital Converter) converts Analog signal into digital and DAC (Digital to Analog Converter) does vice-versa.

Most of the signals generated are analog in nature. Hence these signals are converted to digital form by the analog to digital converter. Thus AD Converter generates an array of samples and gives it to the digital signal processor. This array of samples or sequence of samples is the digital equivalent of input analog signal. The DSP performs signal processing operations like filtering, multiplication, transformation or amplification etc operations over this digital signals. The digital output signal from the DSP is given to the DAC.

Advantages Of Dsp Over Asp

1. Physical size of analog systems are quite large while digital processors are more compact and light in weight.

2. Analog systems are less accurate because of component tolerance ex R, L, C and active components. Digital components are less sensitive to the environmental changes, noise and disturbances.

3. Digital system are most flexible as software programs & control programs can be easily modified.

4. Digital signal can be stores on digital hard disk, floppy disk or magnetic tapes. Hence becomes transportable. Thus easy and lasting storage capacity.

5. Digital processing can be done offline.

6. Mathematical signal processing algorithm can be routinely implemented on digital signal processing systems. Digital controllers are capable of performing complex computation with constant accuracy at high speed.

7. Digital signal processing systems are upgradeable since that are software controlled.

8. Possibility of sharing DSP processor between several tasks.

9. The cost of microprocessors, controllers and DSP processors are continuously going down. For some complex control functions, it is not practically feasible to construct analog controllers.

10. Single chip microprocessors, controllers and DSP processors are more versatile and powerful.

Disadvantages Of DSP over ASP

1. Additional complexity (A/D & D/A Converters)

2. Limit in frequency. High speed AD converters are difficult to achieve in practice. In high frequency applications DSP are not preferred.