| 摘要 |
An apparatus for measuring the noise characteristics of a device under test (14) comprises a noise source (30) and a broadband admittance tuner (40) which are coupled to the device over a directional coupler (18). The output of the device is analyzed by a measuring block (20). A network analyzer (12) is provided for calibrating the system. The noise source (30) consists of a resistor (30a), the noise signal of which is amplified by an amplifier (30b). The output of the amplifier (30d) is fed through a step attenuator (30d). This arrangement allows the generation of noise at several equivalent noise temperatures, which can be calibrated using network analyzer (12) and a measuring block (20). The apparatus requires no factory-calibration of the noise source and allows a high accuracy because noise powers can be measured at a large number of noise temperatures and input admittances. <IMAGE> |
