| 摘要 |
PURPOSE:To achieve the calibration on the low temperature side at a high accuracy by making the noise temperature of a mixer a low temperature calibration source when a magnetic field is applied to a Josephson element to zero the output of the mixer. CONSTITUTION:A signal received with a receiving antenna 1 is converted into an intermediate frequency with a mixer 13 having a Josephson element inside a very low temperature block 16 and undergoes a rectangular modulation with a switch B9. Thereafter, it is inputted into a synchronous detector 7 through an IF section 5 and a square detector 6 to obtain a voltage proportional to a level difference between an input signal and the output of a comparison noise source 4. Here, when a magnetic field applicator 14 is actuated for the mixer 13, the mixer outputted a noise temperature corresponding to a physical temperature thereof 13. The noise temperature output is switched to the comparison noise source 4 with a switch B9 for modulation to obtain an output voltage corresponding to a difference between the temperature of the mixer 13 and the temperature of the comparison noise source thereby enabling calibration on the low temperature side. |
