Accurate Noise Temperature Measurements on Mismatched Semiconductor Devices

Abstract

A measurement system has been developed, which allows the direct determination of the noise temperature of a mismatched one-port network without the use of passive nonreciprocal components. Furthermore this radiometer has been extended to measure "cold" noise temperatures without any cooling of the radiometer components used. As an example of application, the radiometer is applied to noise temperature measurements of semiconductor devices. A brief outline of the measurement system is given and practical measurement results are compared with theoretical predictions. INTRODUCTIONThe noise temperature of a mismatched one-port network can be measured with emissivity-balanced radiometers [1]. Conventional measurement systems need passive nonreciprocal components, e.g. isolators or circulators, to avoid measurement errors caused by the reverse noise radiation of the radiometer receiver, when reflected at a mismatched object under test [2]. In the MHz-range, where passive nonreciprocal components are not available with an acceptable performance, tuning procedures are required to account for mismatching effects [3,4]. The measurement system employed in this paper enables the direct noise temperature measurement without the use of passive nonreciprocal components and any tuning procedure. Thus the frequency range of operation can be in the MHz-range as well as in the GHz-range. The former one is the intermediate frequency range of many microwave measurement and communication systems, where the noise performance of the semiconductor devices is important for the system quality. THE MEASUREMENT SYSTEMThe noise temperature measurement system is designed as a correlationradiometer [2]. The basic configuration of the measurement set-up is shown in fig.

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