White-Noise RF Source (DC-200 MHz)

In this tutorial we present an easy to build RF noise generator. Schematic, construction details as well as the measurement results are discussed here. Additional results from a Spice simulation are available on : http://kavea.free.fr

• 2 x BFR93A
• 1 x 9V Zener diode (Panasonic DZ2409100L is used here)
• 1 x 7812 voltage regulator
• Prototype board
• Couple of resistors and capacitors (see schematic)
• Optional : 1 x SMA connector and 1 x Aluminium case

Build the circuit using the electric schematic. For better RF performances and stability of the amplifier we recommend to use a full ground plane on the bottom side of the circuit board. In our case a copper tape is used for this purpose.

The amplifier was designed to have a 50 Ohm output impedance. In order to validate the noise source we can than connect it to a spectrum analyzer (SA). On the first picture, the noise floor of the SA is shown. The noise spectral density in this case is -135 dBm/Hz. When we turn on the noise source (second picture) the spectral density increased up to -105 dBm/Hz which represent an ENR (Excess Noise Ratio) of 69 dB.