Patent ID: 8686741

Claim:
An excessive-noise-ratio deriving device which, in a transmitter/receiver including a noise source which outputs two types of noise different in a level from each other, a plurality of noise-source-side terminals, a power measurement device which measures a power of an input signal, and a plurality of measurement-device-side terminals, wherein one of the plurality of noise-source-side terminals receives the noise output from the noise source, the input signal is fed via any one of the plurality of the measurement-device-side terminals to the power measurement device, and a difference between a first noise figure which is a noise figure when a predetermined measurement-device-side terminal, which is one of the plurality of measurement-device-side terminals, is connected to the power measurement device and a second noise figure which is a noise figure when a measurement-device-side terminal, which is one of the plurality of measurement-device-side terminals, and is other than the predetermined measurement-device-side terminal, is connected to the power measurement device is designated as inter-measurement-device-side-terminal difference, derives an excessive noise ratio when the noise source is connected to each of the plurality of noise-source-side terminals, comprising: a first noise figure deriving unit that derives the first noise figure based on a ratio of one power to the other power of two types of reference noise, which are different from each other in a level, are output from a reference noise source an excessive noise ratio of which is known, and are measured by the power measurement device when the two types of reference noise are fed as the input signals via the predetermined measurement-device-side terminal to the power measurement device, and the excessive noise ratio of the reference noise source; a second noise figure deriving unit that derives the second noise figure based on the inter-measurement-device-side-terminal difference and the first noise figure; and a noise-source-excessive-noise-ratio deriving unit that derives an excessive noise ratio when the noise source is connected to each of the plurality of noise-source-side terminals based on a ratio of one power to the other power of the two types of noise measured by the power measurement device when each of the plurality of noise-source-side terminals and each of the measurement-device-side terminals are connected to each other, and the two types of noise output from the noise source are fed as the input signals to the power measurement device, the first noise figure, and the second noise figure.