Noise, high frequency

The high-frequency behavior of electronic devices is of major interest in the field of research and development. In addition to the typical RF device parameters, such as the cutoff frequency of the current gain, f(r), and the maximum frequency of oscillation, f(max), high-frequency noise behavior must be considered for circuit design, especially if noise has a significant influence on system performance, for example, the sensitivity of receivers. Thus there is a demand for simple, but exact RF noise models that have to consider the physically relevant noise phenomena making a significant contribution to the total noise behavior of the device. After an introduction to various physical noise sources a standard description of noisy two-port circuits will be given. Next, a short presentation of a special setup for RF noise measurements in the range of 2 GHz to 18 GHz in relation to temperature (15 K to 400 K) is given. Radio-frequency noise phenomena in special devices are then examined, and high-frequency noise models for heterostructure field-effect transistors (HFETs) and heterojunction bipolar transistors (HBTs) based on the system material InP are presented. In the case of the HFET the capability of the model presented here will be proven with the help of a comparison between measured and modeled RF noise parameters. In the last section modifications of the noise model and applications of this RF noise model are presented.