Medical Instrumentation and Signal Filtering

Vocabulary flashcards covering signal filtering, sensor characteristics, noise cancellation techniques, and medical measurement fundamentals.

Inherent Sensitivity

A sensor design approach where the sensor is physically constructed to accept only the target signal and naturally reject energies originating from other directions or sources.

Negative Feedback Loop

A configuration where a portion of the output ($y$) is fed back through a transfer function ($H_f$) and subtracted from the input ($x_d$) to eliminate the influence of sensor transfer function ($G_d$) fluctuations.

Fourier Analysis

A mathematical technique demonstrating that any periodic signal can be decomposed into a sum of sinusoidal functions, each defined by specific frequency, amplitude, and phase shift.

First Harmonic

The fundamental sinusoidal component of a signal that shares the exact same period as the original periodic signal.

Filter Gain

The ratio of the output signal amplitude to the input signal amplitude ($\frac{y}{x}$), expressed as a function of frequency.

White Noise

A noise construct in which every constituent frequency across the spectrum carries identical amplitude or energy.

Notch Filter

A filter designed to reject or attenuate a single specific frequency or very narrow band, commonly used to eliminate power line interference at $60\,Hz$ or $50\,Hz$.

Blood Pressure Signal Frequency Spectrum

The physiological frequency domain of real-time blood pressure signals, which typically ranges from $0\,Hz$ to $20\,Hz$.

ECG Signal Frequency Spectrum

The frequency domain range required for clinical electrocardiogram monitoring, spanning from $0\,Hz$ to $100\,Hz$.

Low-Pass Filter

A filter that preserves low-frequency components with a gain near $1$ while attenuating higher-frequency signals.

Cutoff Frequency

The frequency threshold where a filter's amplitude gain decreases by $-3\,dB$ (approximately a factor of $0.7$ of the input amplitude).

High-Pass Filter

A filter that attenuates low-frequency components while allowing frequencies above the cutoff frequency to pass.

Band-Pass Filter

A filter combination created by placing a low-pass and a high-pass filter in series to preserve frequencies within a specified band and reject those outside.

Band-Stop Filter

A filter configuration that allows frequencies outside a specified range to pass while suppressing frequencies within that target band.

Opposing Inputs

A noise elimination strategy where ambient noise or motion artifacts are recorded, phase-flipped by $180^\circ$, and added back to the signal output to achieve cancellation.

Observational Studies

Medical study designs conducted without a control group where researchers purely gather data from a specified population or cohort.

Interventional Studies

Medical research designs that apply set interventions to experimental groups and measure outcomes relative to an untreated control group.

Biosensors

Devices—either man-made instruments or systems employing living entities like bacteria—that directly interact with biological structures.

Engineering Sensitivity

The quantitative parameter defining the amount of output produced per unit of applied input.

Hysteresis

A non-linear phenomenon where sensor output measurements trace different paths depending on whether input values are transitioning from low-to-high versus high-to-low.

Static Characteristic

The performance parameters of a zero-order sensor evaluated under steady-state inputs where time-dependent dynamic variations are neglected.

Limit of Detection

The smallest input increment above zero required to yield a detectable change in sensor output.

Dynamic Characteristic

The performance behavior of a measurement instrument when responding to time-varying input signals, described by metrics such as frequency response and signal-to-noise ratio.

Signal-to-Noise Ratio ($SNR$)

A dynamic signal quality metric calculated on a logarithmic scale using the formula $20 \log_{10}\left(\frac{\text{amplitude of signal}}{\text{amplitude of noise}}\right)$.