1. Output Level
Depending 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 Characteristics
It'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 Characteristics
Specify 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 Power
Specify 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/Stability
Specify 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.
