Verfahren und Vorrichtung zum Messen des Rauschens eines aktiven Elementes

1,187,301. Measuring noise figure. MATSUSHITA ELECTRONICS CORP. May 9, 1967 [May 23, 1966], No.21399/67. Heading G1U. The noise figure and equivalent noise resistance of an active electrical element, e.g. a field effect transistor, is calculated from the ratios of noise output voltages obtained for at least two values of a signal source impedance Ri connected to an input electrode of the element. Capacitors Ci are used to test that the equivalent noise resistance is independent of Ri and that the element is not a noise current source. The noise output voltage is fed through a frequency selective amplifier 3 and voltage squarer 4 to an indicator 5. The method is applicable to active circuits as opposed to single element) whose equivalent noise resistance may be assumed constant, and also to low input impedance active elements, provided the signal source impedance is low. The equations required for the calculation are given.