Improved 1/f Noise Measurements for Microwave Transistors

Minimizing electrical noise is an increasingly important topic. New systems and modulation techniques require a lower noise threshold. Therefore, the design of RF and microwave systems using low noise devices is a consideration that the circuit design engineer must take into account. Properly measuring noise for a given device is also vital for proper characterization and modeling of device noise. In the case of an oscillator, a vital part of a wireless receiver, the phase noise that it produces affects the overall noise of the system. Factors such as biasing, selectivity of the input and output networks, and selectivity of the active device (e.g. a transistor) affect the phase noise performance of the oscillator. Thus, properly selecting a device that produces low noise is vital to low noise design. In an oscillator, 1/f noise that is present in transistors at low frequencies is upconverted and added to the phase noise around the carrier signal. Hence, proper characterization of 1/f noise and its effects on phase noise is an important topic of research. This thesis focuses on the design of a microwave transistor 1/f noise (flicker noise) measurement system. Ultra-low noise operational amplifier circuits are constructed and used as part of a system designed to measure 1/f noise over a broad frequency range. The system directly measures the 1/f noise current sources generated by transistors with the use of a transimpedance (current) amplifier. Voltage amplifiers are used to provide the additional gain. The system was designed to provide a wide frequency response in order to determine corner frequencies for various devices. Problems such as biasing filter networks, and load resistances are examined as they have an effect on the measured data; and, solutions to these problems are provided. Proper representation of measured 1/f noise data is also presented. Measured and modeled data are compared in order to validate the accuracy of the measurements. As a result, 1/f noise modeling parameters extracted from the measured 1/f noise data are used to provide improved prediction of oscillator phase noise