| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve an S/N ratio of a beat signal made of a transmission wave signal and a reception wave signal. SOLUTION: A high level transmission wave signal and a low level reception wave signal are supplied to a diode 6, while a high level reception wave signal and a low level transmission signal are supplied to a diode 7 respectively with an internal path of a hybrid ring 5. In addition, since forward bias current is supplied from a negative power source 12 only to the diode 6, sensitivity of the diode 6 is reduced, and a noise component due to an oscillator 1 included in the transmission wave signal to be supplied to the diode 6 is hardly detected. On the other hand, the beat signal made of the high level reception wave signal and the low level transmission wave signal is detected with high sensitivity and the S/N ratio of the beat signal to be obtained at an output terminal 8 is improved in the diode 7 to which no bias current is supplied.</p> |
