| 摘要 |
<p>PROBLEM TO BE SOLVED: To enhance the communication efficiency of a communication unit. SOLUTION: The impedance detection circuit 40 for the communication unit is provided with a voltage detection section 42 and a current detection section 44. The voltage detection section 42 is provided with a resistor Ra, a capacitor C and a resistor Rb connected in series between a main connection line 46 and ground in this connection sequence from the main connection line 46 to the ground, and a voltage between the ground and a connecting point of the capacitor C and the resistor Rb connected to the ground is used for a detection voltage VE. Furthermore, the current detection section 44 has a current transformer 48 whose primary winding is the main connection line 46. A resistor R2 is connected in parallel with a secondary winding of the current transformer 48 and a voltage VI across the resistor R2 is detected. Configuring each circuit component to make an imaginary component of the detected voltage VE equal to an imaginary component of the voltage VI can cancel the imaginary component included in the detected voltage VI and causing an error with the imaginary component included in the detected voltage VE.</p> |
