noise specifications

understanding noisefive parameters commonly used to specify noise

1. Output LevelDepending on system type and application, there are many different ways to specify output power when choosing a noise product: power, dBm/Hz, dBm/band, ENR, V/ Hz, noise temp °K. 2. Output CharacteristicsIt's important to define:Impedance: common levels are 50, 75, 600 ohms and 1 Kohm.Match: When the noise source is not buffered from other system components, a well-matched noise source (less than 2:1 VSWR) is recommended.Frequency:Choose either bandwidth limited or broadband. 3. Noise CharacteristicsSpecify the following:Peak factor (crest factor): the peak to RMS voltage ratio.Symmetry: uniformity of positive and negative excursions.Power distribution (white): relates how the noise power is distributed in separate components over the frequency range. 4. Input PowerSpecify the following:Voltage: There are many different DC voltages/currents to supply bias to activate the noise source.Control: Noise sources are controlled by the bias or a digital (TTL) interface.Speed: The delay between the control signal and the arrival of the output signal. 5. Accuracy/StabilitySpecify the following:Temperature coefficient: The rate at which the output power changes over temperature.Input sensitivity: The amount of output power changes with variations in input power.Long term drift: The amount of time (in years) it will take the output power to change.Flatness: The peak deviation of power across the frequency range.