A New Noise Generator : for Microwave Communication Systems Error Rate Measurement

For many digital communication systems, the measure of the error rate as a function of the noise level is fundamental. A new noise generator has been developed for the 1.2 - 1.7 GHz range. Originally intended for the French circular waveguide transmission system, the described device can be applied to any microwave communication system (T.V. Satellite...). Systematic measurement made by the French Post Office laboratories has demonstrated that the noise generated by a reverse biased L.T.T. Schottky diode is perfectly gaussian in the 0.2 to 2 mA range with an excess noise which varies from 18 to 28 dB. The complete generator includes besides the Schottky diode a noise amplifier and a 3 dB coupler, and can be remote controlled. To test the error rate of an equipment, the generated noise is added to the received signal through the 3 dB coupler. The noise level can be adjusted in a more than 10 dB range by controlling the diode current. The circuit is realized in microstrip technology on a 42 × 25.4 mm ceramic substrate.