A cost-effective technique for extending the low-frequency range of a microwave noise parameter test set

The operating frequency range of an on-wafer noise parameter test set based on the multiple-impedance technique has been extended in the low-microwave frequency range (down to the L-band). A simple technique, using a phase sh ifter cascaded with the microwave tuner, allows different reflection coeffi cients of the load impedance to be obtained at the device input. These coef ficients are well distributed over the Smith chart in the entire frequency range. As an example, noise parameters of a passive device have been measur ed between 1 and 8 GHz, and a good agreement between measured and calculate d values is observed. This technique has also been used to measure the nois e parameters of different heterojunction bipolar transistors. A minimum noi se figure of 1 dB was obtained at 1 GHz on a GaAlAs/GaAs HBT which is in ag reement with expected results.