3. Noise measurement

The parameters that characterize a system's ability to handle low-level signals are sensitivity, bit error rate (BER) for digital communication systems, and noise figure. The latter characterizes both the system as a whole and its constituent components, such as the preamplifier, mixer and intermediate-frequency amplifier. Thus, by controlling the noise figure and gain of system components, the noise figure of the overall system can be directly controlled. Once the noise figure is known, sensitivity can easily be estimated from the system's bandwidth. Noise figure is one of the key parameters that differentiates one...