A novel white noise generator as the tracking generator for filter measurements

A novel and low-cost white noise generator using an ordinary Zener diode as the source of noise is presented. The Zener diode is driven by a stable dc current source such that the noise signal power generated by the Zener diode increases with increasing frequency under right dc current biasing. A 6-stage MMIC amplifier block was designed to increase the noise power further. Since the gain-frequency response of the amplifier block has a negative slope as the frequency increases, the positive slope of the noise power produced by the Zener diode is balanced with the negative slope of the amplifier gain. The resulting amplified noise signal appears to have almost constant power at the output of the amplifier. As a result, the designed noise generator exhibits white noise characteristics, and is used as a tracking generator to measure insertion loss of a RF/microwave filter.