Microwave Transistor Noise Model Extraction Methods and a Non-Contacting Scattering Parameter Measurement Method

Doktorsavhandling, 2001

This thesis has two parts. The first part discuss noise model extraction methods for FETs. The second part describe theory and implementation of a non-contacting S-parameter measurement method. Noise is an important aspect for a circuit designer, because noise generated in the circuit is a sensitivity limiting factor. Models are used to predict the noise performance of a circuit. The thesis present three methods for noise model extraction. The methods were developed and tested with commercial and in-house HFET and MESFET transistors, using the Pospieszalski temperature noise model (all three cases) and the PRC noise model (the third method). The first two methods are designed for noise models containing thermal noise sources only, as is the case for the Pospieszalski model. In the PRC model correlation between noise sources is necessary and this problem is treated in the third paper. This paper also presents a comparison of the Pospieszalski and PRC model for the case of a SiC MESFET. The first two methods rely on noise figure measurements for one and two source impedances respectively. They can be used with noise parameter data as well, and this is recommended for the second method. The third method use noise parameter data explicitly. The second part contains a discussion of a new non-contacting S-parameter measurement method. The basic idea is to provide means for measuring S-parameters of circuits assembled on a circuit board. This is done by transmitting the test signal through the signal path of the system under test and measuring the waves on transmission lines connected to the device under test. The signal is picked-up by a capacitive and inductive probe pair connected to a network analyzer. For calibration ordinary network analyzer calibration algorithms can be used. In addition a method for power calibration, which supports measurement of power in the forward and backward waves on the lines connecting the device under test, is discussed.