| 摘要 |
PURPOSE:To reduce the time of measurement and at the same time to obtain a desired result of analysis from the measurement data, by supplying the noise source output to an electronic tuner when the local oscillation frequency is identical with a desired channel and accordingly measuring the NF value from an IF signal superposed by the random noise. CONSTITUTION:The local oscillation frequency of each channel of an electronic tuner 1 to be measured is read in the form of a code signal of the corresponding local oscillation frequency out of an RAM20 based on the dividing number set previously to a CPU23 to be supplied to a synchronous phase detector 15. At the same time, the local oscillation frequency given from a VC05 is divided into 1/n through a divider 13, etc., and the frequency and the phase are compared between a local signal and the set local oscillation. When no coincidence is obtained, a phase incoming signal is detected. Then a PLL loop is automatically formed until a coincidence is obtained. When the local oscillation frequency is identical with a desired channel, the output of a noise source 8 is supplied to the tuner 1. Then the NF value is measured by an NF measuring device 7 from an IF signal superposed by the random noise and then processed by the CPU23. |
