Showing papers by "Per Ola Börjesson published in 1982"
TL;DR: A mathematical model for the occurrence of nonoverlapping pulse-shaped waveforms corrupted with colored Gaussian noise is considered for the purpose of QRS detection and Adaptivity of the detector is gained by utilizing past as well as future signal properties in determining thresholds for QRS acceptance.
Abstract: A mathematical model for the occurrence of nonoverlapping pulse-shaped waveforms corrupted with colored Gaussian noise is considered for the purpose of QRS detection. The number of waveforms, the arrival times, amplitudes, and widths are regarded as random variables. The joint MAP estimation of all the unknown quantities consists of linear filtering followed by an optimization procedure. A class of filters is introduced which is easy to implement. The mismatching obtained by using this class for detection of model QRS complexes is investigated. The optimization procedure is time-consuming and is modified so that a threshold test is obtained. The model formulation with nonoverlapping waveforms leads to an "eye-closing" procedure covering a segment before as well as after an accepted event. Adaptivity of the detector is gained by utilizing past as well as future signal properties in determining thresholds for QRS acceptance.
71 citations
01 Jan 1982
TL;DR: In this article, the authors describe an approach that uses AD and DA conversion and a computer in order to preshape a transmitted ultrasonic wave, which is then stored in a high speed memory.
Abstract: This p aper describes an a rrangement that uses AD and DA conversion and a computer in order to preshape a transmitted ultrasonic wave. Normally the ultrasonic transducer is excited by a very short e lectrical pulse. Using a DAC, the ultrasonic transducer can be excited by any desired waveform e g the digitally determined inverse filter, chirp signals etc. The desired excitation waveform is stored in a high speed memory. It is shifted out via the DAC to an amplifier and thence to the transducer. The ADC, which is triggered by the DAC equipment, converts one sample per sweep into 12 bits. Therefore, actual sample rate is low. But the virtual sample rate limited by the sample and hold circuit can reach 15 MHz. The ADC and DAC are connected to a microcomputer system that determines the desired excitation waveform. Various waveforms can be stored and it is then possible to change the excitation waveforms interactively during clinical examinations.
9 citations