| 摘要 |
PROBLEM TO BE SOLVED: To widen a dynamic range for the input signal, to lower the noise level against a main signal regardless of a high or low level of the input signal and to improve the S/N by preparing a ferrimagnetic substrate and a magnetic field application means which selects one of three axial directions of the ferrimagnetic substrate and applies a magnetic field in the selected direction. SOLUTION: The signal inputted via a signal input terminal 2 is amplified by an amplification factor variable amplifier 3 and divided into two signals by a signal distributor 4. Then one of divided signals is inputted to a magnetostatic wave filter 7 with the other signal inputted to a level detection circuit 5 respectively. The circuit 5 detects the level of a main signal, i.e., a 1st signal and the level of a noise, i.e., a 2nd signal based on the inputted signal and inputs these detected levels to a control circuit 6. The circuit 6 decides a mode of the necessary magnetostatic wave based on the main signal and noise levels and controls an electromagnet 8 to generate a magnetic field for the desired magnetostatic wave mode. The circuit 6 also controls the amplifier 3 to input the signal of an optimum level to the filter 7. |
