Provided is an active filter circuit connected to a power-receiving terminal of a power line for an alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid, or for a direct-current power supplied from the direct-current power source for reducing a harmonic component of a conduction noise propagating to the power line and outputting the reduced harmonic; and a controller for monitoring a variation in the state of an input power entering a power source module for generating drive power for an active element constituting the active filter circuit, or a variation in the state of the drive power supplied from the power source module, and diagnosing an abnormality of a circuit operation for a circuit including the active element of the active filter circuit therein.

Provided is an active filter circuit connected to a power-receiving terminal of a power line for an alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid, or for a direct-current power supplied from the direct-current power source for reducing a harmonic component of a conduction noise propagating to the power line and outputting the reduced harmonic; and a controller for monitoring a variation in the state of an input power entering a power source module for generating drive power for an active element constituting the active filter circuit, or a variation in the state of the drive power supplied from the power source module, and diagnosing an abnormality of a circuit operation for a circuit including the active element of the active filter circuit therein.

Dual mode filters having two reconfigurable multi-stage filters. In a dual band mode, each reconfigurable filter filters an input signal in a different band using every filter stage. In a single band mode, both reconfigurable filters are effectively divided into two sub-chains that include either the odd-numbered filter stages or the even-numbered filter stages. Together, the four sub-chains in the single band mode filter an input signal in a single band with a higher parallelization than each reconfigurable filter in the dual band mode. In some embodiments, the dual mode filter is a decimation filter. In other embodiments, the dual mode filter is a resampling filter. In still other embodiments, the dual mode filter is an interpolation filter.

Dual mode filters having two reconfigurable multi-stage filters. In a dual band mode, each reconfigurable filter filters an input signal in a different band using every filter stage. In a single band mode, both reconfigurable filters are effectively divided into two sub-chains that include either the odd-numbered filter stages or the even-numbered filter stages. Together, the four sub-chains in the single band mode filter an input signal in a single band with a higher parallelization than each reconfigurable filter in the dual band mode. In some embodiments, the dual mode filter is a decimation filter. In other embodiments, the dual mode filter is a resampling filter. In still other embodiments, the dual mode filter is an interpolation filter.

A communication system includes a demodulator configured to demodulate a modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit. The filter is configured to generate a filtered first signal based on a first signal. The first signal is a product of the first carrier signal and the modulated signal. The filter has a gain adjusted based on a set of control signals. The gain adjusting circuit is coupled to the filter, and is configured to generate the set of control signals based on at least a voltage of the filtered first signal. The gain adjusting circuit includes a first peak detector coupled to the filter. The first peak detector is configured to output a peak value of the voltage of the filtered first signal.

An inductive synthesis circuit that mimics an ideal inductor over a wide range of inductance values, from less than 1 mH to more than 100 H, can be used in place of an inductor in any electrical circuit. One application of a synthesized inductor is in an integrated circuit in which it is impractical to construct a coil of wire. The inductive synthesis circuit is suitable for use in a calibration instrument for testing an inductance meter. The inductive synthesis circuit, together with a resistive synthesis circuit and a capacitive synthesis circuit, can be used to calibrate a multi-meter. Alternatively, the inductive synthesis circuit can be used to mimic an ideal inductor in a filter circuit that includes an inductor component, such as a high pass filter, a notch filter, or a band pass filter.

A differential signal represented by a voltage difference between two signals that propagate through two signal lines is input to a signal processing circuit from a connector. A first suppressing circuit and a second suppressing circuit suppress peak values of the two signals. A DC removing circuit removes DC components of the two signals. A common mode choke coil (noise removing circuit) removes common mode noise included in the two signals. The DC removing circuit and the noise removing circuit are disposed between the first suppressing circuit and the second suppressing circuits. If the voltage of the signal line is a first threshold voltage, a current flows through a first suppressing device (first connection device). If the voltage of the signal line is a second threshold voltage, a current flows through a second suppressing device (second connection device). The second threshold voltage is less than the first threshold voltage.

A differential signal represented by a voltage difference between two signals that propagate through two signal lines is input to a signal processing circuit from a connector. A first suppressing circuit and a second suppressing circuit suppress peak values of the two signals. A DC removing circuit removes DC components of the two signals. A common mode choke coil (noise removing circuit) removes common mode noise included in the two signals. The DC removing circuit and the noise removing circuit are disposed between the first suppressing circuit and the second suppressing circuits. If the voltage of the signal line is a first threshold voltage, a current flows through a first suppressing device (first connection device). If the voltage of the signal line is a second threshold voltage, a current flows through a second suppressing device (second connection device). The second threshold voltage is less than the first threshold voltage.

A passband filter includes a first and second microelectromechanical resonator system, each including a resonating beam, a drive electrode, and a sense electrode. An AC input signal is coupled to the drive electrode of the first and second microelectromechanical resonator system. A differential-to-single ended amplifier has a first input and second input respectively coupled to the sense electrodes of the first and second microelectromechanical resonator systems. An output of the differential-to-single ended amplifier is an output of the passband filter that provides a bandpass filtered signal of the AC input signal. A DC bias signal is coupled to the resonating beams of the first and second microelectromechanical resonator systems. The first microelectromechanical resonator system exhibits a hardening nonlinear behavior defining an upper stop frequency of the passband and the second microelectromechanical resonator system exhibits a softening nonlinear behavior defining a lower stop frequency of the passband.

A passband filter includes a first and second microelectromechanical resonator system, each including a resonating beam, a drive electrode, and a sense electrode. An AC input signal is coupled to the drive electrode of the first and second microelectromechanical resonator system. A differential-to-single ended amplifier has a first input and second input respectively coupled to the sense electrodes of the first and second microelectromechanical resonator systems. An output of the differential-to-single ended amplifier is an output of the passband filter that provides a bandpass filtered signal of the AC input signal. A DC bias signal is coupled to the resonating beams of the first and second microelectromechanical resonator systems. The first microelectromechanical resonator system exhibits a hardening nonlinear behavior defining an upper stop frequency of the passband and the second microelectromechanical resonator system exhibits a softening nonlinear behavior defining a lower stop frequency of the passband.