A microprocessor based device (1) for generating a representation of the total harmonic distortion in an ac waveform (W) derives from digital samples of the waveform a fundamental signal (F) representing the value of the fundamental frequency component of each sample. A harmonic signal is then generated as the difference between the sample value and the fundamental component of the sample. An output signal representing total harmonic distortion is then generated as the ratio of the RMS value of the harmonic signal to the RMS value of the fundamental signal converted to a percentage.

Apparatus and method for generating a signal representative of total harmonic distortion in waveforms of an A/C electrical system

A sterilization system and method applies low frequency power to a plasma within a vacuum chamber to remove gas or vapor species from an article. The sterilization system includes a switching module adapted to pulsate the low frequency power applied to the plasma and a low frequency power feedback control system for controllably adjusting the low frequency power applied to the plasma. A power monitor is adapted to produce a first signal indicative of the low frequency power applied to the plasma within the vacuum chamber. A power control module is adapted to produce a second signal in response to the first signal from the power monitor, and a power controller is adapted to adjust, in response to the second signal, the low frequency power applied to the plasma to maintain a substantially stable average low frequency power applied to the plasma while the article is being processed.

Sterilization system employing a switching module adapted to pulsate the low frequency power applied to a plasma

The present invention provides a sterilization system that includes a low frequency power feedback control system for controllably adjusting a power applied to a low frequency plasma within a vacuum chamber of the sterilization system to remove gas or vapor species from the article. The power has a frequency of from 0 to approximately 200 kHz. The low frequency power feedback control system includes a power monitor adapted to produce a first signal indicative of the power applied to the low frequency plasma within the vacuum chamber. The low frequency power feedback control system further includes a power control module adapted to produce a second signal in response to the first signal from the power monitor, and a power controller adapted to adjust, in response to the second signal, the power applied to the low frequency plasma to maintain a substantially stable average power applied to the low frequency plasma while the article is being processed.

Power system for sterilization systems employing low frequency plasma

A sterilization system applies power to a plasma within a chamber to remove gas or vapor species from an article. The sterilization system includes a power feedback control system for controlling the power applied to the plasma. The power feedback control system includes a current monitor adapted to produce a first signal indicative of a current applied to the plasma within the chamber. The power feedback control system further includes a voltage monitor adapted to produce a second signal indicative of a voltage applied to the plasma within the chamber. The power feedback control system further includes a power control, module comprising a programmable digital signal processor. The digital signal processor is adapted to receive and process the first signal and the second signal by multiplying the current and the voltage and producing a third signal indicative of the product of the current and the voltage. The power feedback control system further includes a plasma generator coupled to the power control module and adapted to adjust, in response to the third signal, the power applied to the plasma within the chamber.

Sterilization system with a plasma generator controlled by a digital signal processor

A method and apparatus for controlling the power consumption of a receiver based on current operating conditions is described herein. A receiver according to the present invention applies a received signal to a variable filter. The received signal includes a desired in-band signal. Depending on the current operating conditions, the received signal may further include one or more unwanted out-of-band blocking signals. A filter controller controls one or more operating parameters of the variable filter to maintain the power ratio at the filter output of the power of the blocking signal(s) to the in-band signal at or below a desired level. In so doing, the present invention controls the receiver power consumption while still providing the desired receiver performance.

Automatic filter control

AC coupling is effected by a feedback circuit that detects a DC component in the coupled signal, and adjusts a DC subtraction signal accordingly. In one embodiment, a digital signal processor (DSP) analyzes the coupled signal for a remaining DC component, and controls the subtraction signal. Use of a DSP allows dynamic control of parameters including AC cutoff frequency, gain, and transfer function. Another embodiment provides accurately phase matched AC coupling across two or more signal channels.

Method and apparatus for AC coupling

The accuracy of an automated THD measurement performed by an FFT signal analyzer is improved by refining the estimate of the signal's fundamental frequency on which the THD analysis is based. This refinement is accomplished by calculating a parameter that represents the relative accuracy of the estimate and then varying the estimate to maximize the parameter. The result is a process which permits refinement of the fundamental frequency to an almost arbitrary accuracy, resulting in a highly improved measurement of THD.

Thomas V. Bruhns

Papers

Method and apparatus for AC coupling

Automated method for determining total harmonic distortion