Noise performance of negative-resistance compensated microwave bandpass filters. Theory and experiments

This paper examines both theoretically and experimentally the dependency of in-band noise performance upon circuit and device parameters of microwave filters employing negative-resistance compensation. By neglecting the influence of the induced gate noise source, a general expression for evaluating the noise figure of a second-order active filter is derived as a function of design parameters such as the transistor´s noise figure, inductor´s quality factor, and filter´s bandwidth. In addition, factors affecting the optimization of the overall noise figure of these filters are discussed. For verification, the measured performance of two 900-MHz experimental MESFET filters are included