Abstract: A noise suppressing circuit comprises: windings (W11, W12) inserted to conductor lines (3, 4) at respective points (P11a, P11b) and coupled to each other through a magnetic core (11); a winding (W13) coupled to the windings (W11, W12) through the core (11); capacitors (12, 13) having ends connected to the conductor lines (3, 4) at respective points (P12a, P12b) and the other ends connected to an end of the winding (W13); and windings (W14, W15) inserted to conductor lines (3, 4) at respective points (P13a, P13b) and coupled to each other through a magnetic core (14). These components reduce common mode noise. Capacitors (16, 17) reduce normal mode noise in cooperation with leakage inductances produced by the windings (W14, W15).

Abstract: A signal suppression filter (22) that inhibits high-frequency signals contained in power voltage and a signal separation filter (23) that prevents transmission of the high-frequency signals are provided in series on power lines (21A), (21B) connected to a power input terminal (T1), and a common-mode signal detection circuit (25) and a normal-mode signal detection circuit (26) are provided separately from each other. While bi-directionally blocking transmission of a high-frequency signal (noise) between the power supply and the device to be measured by the signal suppression filter (22) and the signal separation filter (23), the common mode signal and the normal mode signal generated in the device to be measured (3) and entering through a power output terminal (T2) are detecting separately. The analysis of the cause of occurrence of a high-frequency signal produced in the device to be measured (3) is facilitated, and proper noise countermeasure may be taken.

Abstract: A noise suppressing circuit (1) suppresses noise emerging from an electronic apparatus (2) and propagating through conductive lines (3a and 3b). The noise suppressing circuit (1) comprises a low-band noise reducing circuit (10) and a high-band noise reducing circuit (80). The low-band noise reducing circuit (10) is connected to the electronic apparatus (2) through the conductive lines (3a and 3b). The high-band noise reducing circuit (80) is cascade-connected to the low-band noise reducing circuit (10) and connected to conductive lines (4a and 4b) of a power line (4).