Noise in Electrical Circuits, and The Need for Reduction of Noise
Noise Figure Measurement - A Practical Approach
1. Noise in Electrical Circuits, and The Need for Reduction of Noise.
Electronic components are basically made up of materials that contain electrical charges. These electrical charges are built due to electrons movements within
the component. Due to quantum nature of these electrons, an electrical component produces noise at temperatures other than absolute zero (00 K). Due
to this fundamental nature of materials to induce noise, it is impossible to remove noise completely from an electrical circuit at room temperatures (or the
temperatures at which it operates). In other words, material properties, thermal fluctuations, discreteness of electrical charges, and junction temperatures are
the primary cause of noise
Why do we want to remove or contain the noise in an electrical circuit? The reasons for reducing noise may be any of the following:
To improve sensitivity of the circuit to detect desired signals in a receiver.
To reduce harmonic content and phase noise in a transmitter,
To improve output signal to noise ratio.
For example, take satellite TV. The signals your antenna dish receives are of the order of -100dBm
Note: 1 mW (1X10-3 W) = 0dBm,
1 mW(1X10-6W) = -30dBm and so on.
To receive a signal of this magnitude, the noise levels should be comfortably below -100dBm. This requires careful design and manufacture of electrical
components (both active and passive), and assemblies.