A novel approach for MODFET noise parameter extraction and its application in mm-wave MMICs

The noise behavior of MODFET transistors is modeled using the "Noise Temperature Model" developed by Pospieszalski. This model relates the transistor noise parameters to the transistor circuit model by assigning an equivalent noise temperautre to each resistor in the small signal equivalent circuit model. The ambient temperature Ta is assigned to all the resistive circuit elements apart from the output conductance, which is modeled to be at a higher temperature Td. Applying this model allows the noise parameters to be extracted from measured data as follows; first the circuit element values are extracted from s-parameter measurements, then the value of Td is extracted from a single noise figure measurement (performed in a 50 Omega system). Once these parameters are known, all four transistor noise parameters are then calculated even up to mm-Wave frequencies. In addition, implementing the "Noise Temperature Model" in commercial CAD software packages allows the noise performance of mm-W ave MMICs to be accurately predicted during circuit design.