A multi-phase VFD system with frequency compensated ground fault protection includes a variable frequency drive (VFD) power supply, a motor coupled to the VFD power supply by a plurality of power wires and a relay, an annular magnetic core provided with a sensor winding, where the plurality of power wires extend through the annular magnetic core, an analog signal conditioner, an analog-to-digital (A/D) converter, and a digital processor performing a Fast Fourier Transform (FFT) process on the received digital output of the A/D converter to provide frequency information which is used to develop a frequency equalized transfer function for calculating ground fault current.

A software-defined radiometer includes dual RF front end channels. One RF front end channel processes the horizontal polarization signals and the other RF front end channel processes the vertical polarization signals. Each RF front end channel includes a power splitter for splitting the polarization signals into a plurality of identical polarization signals, a filter bank of N-bandpass filters that have the same bandwidth but different center frequencies and a multi-input switch. The bandpass filters filter the horizontal and vertical polarization signals and provide a plurality of filtered horizontal and vertical polarization signals. A control circuit issues a control signal to the multi-input switch so as to route a desired one of the plurality of filtered horizontal and vertical polarization signals to a programmable frequency converter. The programmable frequency converter includes a programmable local oscillator that is configured to generate signals having any one of N frequencies and is used to produce intermediate frequency representations of the horizontal and vertical polarization signals. The intermediate frequency representations are converted into digital signals and processed to extract desired information and data.

A software-defined radiometer includes dual RF front end channels. One RF front end channel processes the horizontal polarization signals and the other RF front end channel processes the vertical polarization signals. Each RF front end channel includes a power splitter for splitting the polarization signals into a plurality of identical polarization signals, a filter bank of N-bandpass filters that have the same bandwidth but different center frequencies and a multi-input switch. The bandpass filters filter the horizontal and vertical polarization signals and provide a plurality of filtered horizontal and vertical polarization signals. A control circuit issues a control signal to the multi-input switch so as to route a desired one of the plurality of filtered horizontal and vertical polarization signals to a programmable frequency converter. The programmable frequency converter includes a programmable local oscillator that is configured to generate signals having any one of N frequencies and is used to produce intermediate frequency representations of the horizontal and vertical polarization signals. The intermediate frequency representations are converted into digital signals and processed to extract desired information and data.

A measurement apparatus and method for measurement of a radio frequency (RF) signal, said measurement apparatus comprising a signal input adapted to receive an RF-signal being split into a first measurement signal path and into a second measurement signal path of said measurement apparatus, wherein said first measurement signal path is adapted to measure the split RF-signal within a predefined first frequency band around a predefined measurement frequency, wherein said second measurement signal path is adapted to measure a current frequency at a power maximum of the split RF-signal in a predefined second frequency band, and wherein the RF-signal measured in said first measurement signal path is shifted in the frequency domain depending on the current frequency measured in said second measurement signal path.

A measurement apparatus and method for measurement of a radio frequency (RF) signal, said measurement apparatus comprising a signal input adapted to receive an RF-signal being split into a first measurement signal path and into a second measurement signal path of said measurement apparatus, wherein said first measurement signal path is adapted to measure the split RF-signal within a predefined first frequency band around a predefined measurement frequency, wherein said second measurement signal path is adapted to measure a current frequency at a power maximum of the split RF-signal in a predefined second frequency band, and wherein the RF-signal measured in said first measurement signal path is shifted in the frequency domain depending on the current frequency measured in said second measurement signal path.

A sensor circuit usable with capacitive sensors in an electrical potential sensing network is provided. The sensor circuit provides bias current while maintaining a high input impedance for signals in a frequency band of interest by positive feedback of a filtered measurement through a finite impedance. The sensor circuits are suited for technologies such as, but not limited to electroencephalography (EEG), electromyography (EMG) and electrocardiograms (ECG). A neurofeedback system utilizing the capacitive conduction sensor is also described.

A sensor circuit usable with capacitive sensors in an electrical potential sensing network is provided. The sensor circuit provides bias current while maintaining a high input impedance for signals in a frequency band of interest by positive feedback of a filtered measurement through a finite impedance. The sensor circuits are suited for technologies such as, but not limited to electroencephalography (EEG), electromyography (EMG) and electrocardiograms (ECG). A neurofeedback system utilizing the capacitive conduction sensor is also described.

A band pass filter including a microstrip transmission line comprises: a substrate having a grounding surface formed on a rear surface thereof; an input port which is formed on an upper surface of the substrate and receives a transmission signal; an output port which is formed on the upper surface of the substrate and outputs a filtered transmission signal; and a plurality of signal transmission lines spaced at predetermined distance from one another in parallel, each of the plurality of signal transmission lines having one end connected to and in contact with the input port, and having the other end connected to and in contact with the output port.

A band pass filter including a microstrip transmission line comprises: a substrate having a grounding surface formed on a rear surface thereof; an input port which is formed on an upper surface of the substrate and receives a transmission signal; an output port which is formed on the upper surface of the substrate and outputs a filtered transmission signal; and a plurality of signal transmission lines spaced at predetermined distance from one another in parallel, each of the plurality of signal transmission lines having one end connected to and in contact with the input port, and having the other end connected to and in contact with the output port.

An automatic filtering method includes: a step of analyzing an input signal so as to obtain a frequency spectrum of the input signal; and a step of selecting, on the basis of the frequency spectrum, at least one filter from among a plurality of preset filters and filtering the input signal. The step of selecting includes determining, on the basis of the frequency spectrum of, a signal type in the input signal; selecting, on a basis of the signal type, a corresponding filter corresponding to the signal type; filtering the input signal with use of a first parameter of the corresponding filter and setting a second parameter for the corresponding filter on a basis of a result of the filtering; and filtering the input signal with use of the second parameter set for the corresponding filter. The method may ensure a filtering effect against noise.