A composite analog-to-digital converter (ADC) has a low resolution ADC configured to receive and digitize analog data, the low resolution ADC having a low resolution and a high operating speed, one or more high resolution ADCs configured to receive and digitize the analog data, the one or more high resolution ADCs having a resolution higher than the low resolution ADC, and an operating speed lower than the high operating speed of the low resolution ADC, a sample clock generator to provide a sample clock signal to the low resolution ADC and to a clock divider, a mixer to receive the analog data and connected to the one or more high resolution ADCs, a local oscillator connected to the mixer to allow the one or more high resolution ADCs to be tuned to sample a portion of a spectrum of the first ADC. A test and measurement instrument contains a composite ADC. A method of operating a composite analog-to-digital converter (ADC), includes receiving an analog signal at a low resolution ADC that operates at a high speed, receiving the analog signal at one or more high resolution ADCs that operate at a resolution higher than the low resolution ADC and at a lower speed than the operating speed of the low resolution ADC, tuning the high resolution ADC to phase align and time align a signal path for the one or more high resolution ADCs to the signal path for the low resolution ADC, producing a spectrum from the low resolution ADC, and producing a portion of the spectrum from the one or more high resolution ADCs.

A method of monitoring the performance of a multi-phase electric motor (13), wherein the electric motor comprises a plurality of stator windings (7, 8, 9) connected in a wye configuration to form a wye point. The method comprises measuring an electrical characteristic of the wye point in a time domain; based upon the measured electrical characteristic of the wye point in the time domain, determining an electrical characteristic of the wye point in the frequency domain; and deriving data indicative of at least one parameter of the performance of the electric motor based upon the determined electrical characteristic of the wye-point in the frequency domain.

A method of monitoring the performance of a multi-phase electric motor (13), wherein the electric motor comprises a plurality of stator windings (7, 8, 9) connected in a wye configuration to form a wye point. The method comprises measuring an electrical characteristic of the wye point in a time domain; based upon the measured electrical characteristic of the wye point in the time domain, determining an electrical characteristic of the wye point in the frequency domain; and deriving data indicative of at least one parameter of the performance of the electric motor based upon the determined electrical characteristic of the wye-point in the frequency domain.

The invention relates to a method (1) for monitoring a rotating machine (100) of an aircraft, wherein a measurement signal is acquired from the rotating machine. According to the invention, instantaneous frequencies (f.sub.K(t)) of sinusoidal components of the measurement signal are estimated, and, using a computing module (12), a plurality of successive iterations are carried out in each of which: complex envelopes of the components are updated (C1), parameters of a model of a noise of the signal are updated (C21) on the basis of the envelopes, whether the model has converged from the preceding iteration to the present iteration is tested (C4), with a view to: o if not, carrying out a new iteration, o if so, performing a computation (D) of the complex envelopes on the basis of the iterations that have been carried out.

An arc detector for a RF power supply system, where the RF power supply incudes a first RF power supply and a second RF power supply. A signal applied to a non-linear load varies in accordance with an output from one of the first RF power supply or the second RF power supply. The signal has a frequency. During an arc or arc condition in the non-linear load, the frequency of the signal changes, and if the frequency is outside of a selected range, an arc or arc condition is indicated. The frequency can be determined by digitizing the signal into a series of pulses and measuring a time or period between pulses.

An arc detector for a RF power supply system, where the RF power supply incudes a first RF power supply and a second RF power supply. A signal applied to a non-linear load varies in accordance with an output from one of the first RF power supply or the second RF power supply. The signal has a frequency. During an arc or arc condition in the non-linear load, the frequency of the signal changes, and if the frequency is outside of a selected range, an arc or arc condition is indicated. The frequency can be determined by digitizing the signal into a series of pulses and measuring a time or period between pulses.

A method and device for increasing an accuracy of a phase measurement, wherein the method includes: receiving a measurement signal; performing a frequency-domain transformation to the measurement signal to obtain a frequency-domain measurement sequence; determining phases that correspond to frequency-domain measurement signals, and determining a phase difference between the frequency-domain measurement signals that correspond to two neighboring specified frequency points; according to the phases, the phase difference and a window function, performing a sliding-window-type phase fitting to the frequency-domain measurement sequence, to obtain phase-fitting data that correspond to sliding windows; and according to the phase-fitting data of the sliding windows, determining phase-calibration data that correspond to the sliding windows, and, by using the phase-calibration data of the sliding windows, forming phase-calibration data within a specified frequency band. The method reduces an error of fitting, and increases an accuracy of a phase calibration.

A method and device for increasing an accuracy of a phase measurement, wherein the method includes: receiving a measurement signal; performing a frequency-domain transformation to the measurement signal to obtain a frequency-domain measurement sequence; determining phases that correspond to frequency-domain measurement signals, and determining a phase difference between the frequency-domain measurement signals that correspond to two neighboring specified frequency points; according to the phases, the phase difference and a window function, performing a sliding-window-type phase fitting to the frequency-domain measurement sequence, to obtain phase-fitting data that correspond to sliding windows; and according to the phase-fitting data of the sliding windows, determining phase-calibration data that correspond to the sliding windows, and, by using the phase-calibration data of the sliding windows, forming phase-calibration data within a specified frequency band. The method reduces an error of fitting, and increases an accuracy of a phase calibration.

The present invention is related to a signal spectrum analysis technology based on linear frequency modulation transformation (LFM) and fast digital pulse compression, which comprises two parts: a circuit for linear frequency modulation signal and an algorithm for fast digital pulse compression. Wherein, in the circuit the modulated chirp signals are obtained by the input signals mixing with the LO chirp signal and then filtered by the band-pass filter the intermediate frequency (IF) chirp signals are produced. The IF signals are composed of the chirp signals with the same frequency band and the chirp rate, but different initial times. Due to the IF chirp signals being orthogonal to each other, the spectrum of the input signals is extracted by the initial time and the orthogonal accumulation. The full spectrum of the input signal is obtained by changing the start position of the sampling data sets along the time axis. The present invention achieves fast high-resolution spectrum analysis by combining the circuit for linear frequency modulation signal and the algorithm for fast digital pulse compression.

The present invention is related to a signal spectrum analysis technology based on linear frequency modulation transformation (LFM) and fast digital pulse compression, which comprises two parts: a circuit for linear frequency modulation signal and an algorithm for fast digital pulse compression. Wherein, in the circuit the modulated chirp signals are obtained by the input signals mixing with the LO chirp signal and then filtered by the band-pass filter the intermediate frequency (IF) chirp signals are produced. The IF signals are composed of the chirp signals with the same frequency band and the chirp rate, but different initial times. Due to the IF chirp signals being orthogonal to each other, the spectrum of the input signals is extracted by the initial time and the orthogonal accumulation. The full spectrum of the input signal is obtained by changing the start position of the sampling data sets along the time axis. The present invention achieves fast high-resolution spectrum analysis by combining the circuit for linear frequency modulation signal and the algorithm for fast digital pulse compression.