4. Noise figure measurement

Measuring the noise of a circuit requires the use of a calibrated noise generator and a sensitive wattmeter, or a detector appropriate to the frequency band under study. It should be performed using impedance matching.

Noise generators deliver random amplitude signals with a predetermined frequency spectrum. Their range of use extends from 80 kHz to several hundred MHz.

Figure 18 shows two typical examples of noise spectra from these generators. Curve I corresponds to pink noise whose spectrum is proportional to 1/ $\sqrt{f}$ , where f is the frequency....