| 摘要 |
PURPOSE:To eliminate disturbance due to an external noise by constituting a tuning circuit by utilizing the secondary winding of a balanced-unbalanced transformer connected to a loop antenna. CONSTITUTION:The balance coil 10 of a balance-unbalance coil (balun) 9 is connected across the antenna coil 3 of a loop antenna 1. On the other hand, a variable capacitor 4 is connected across the secondary unbalance coil 11 of the balun 11, and a tuning curcuit 5 is formed depending upon the inductance L2 of said coil 11 and the capacity value of the variable capacitor 4. Then, a maximum output is obtained when L=M<2>QL2/L2, where L is the inductance of the antenna coil 3, L2 the inductance of the unbalance coil 11 of the balun 9, M the mutual inductance between the coils 10 and 11 of the balun 9, and QL2 the load Q of the tuning circuit 5. |
