Introduction: White-Noise RF Source (DC-200 MHz)

By kavea blog

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

Step 1: Materials

  • 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

Step 2: Construction

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.

Step 3: Measurement

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.