23 07 20 part2 text and solution

Pagina 1

EXERCISE 1 We are interested in the design of an Analog to Digital conversion system to record an ECG signal for clinical diagnosis of atrial fibrillation a) Draw the block diagram of the A/D conversion system which can adequately record the signal. For each stage report the numerical values. Moreover, report and motivate the chosen sampling frequency value. ECG Band 0.05-200 Hz for diagnostic application. Analogue filter is a low pass anti -aliasing filter (LPAA). A LPAA is a filter used before a signal sampler to limit the bandwidth of a signal in order to properly apply the sampling theorem. LPAA 𝑓𝑓 𝑐𝑐𝑐𝑐𝑐𝑐 is chosen to be equal to 220 Hz (10% margin), to limit the corresponding bandwidth of the signals. A/D: Shannon theorem fulfilled so that 𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠≥ 2𝑓𝑓𝑠𝑠𝑠𝑠𝑚𝑚, where 𝑓𝑓𝑠𝑠𝑠𝑠𝑚𝑚 is the equal to the highest frequency content among the previously described signal (after proper limiting the band of the signal). In this context, we choose 𝑓𝑓𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠= 500 Hz. 𝑓𝑓𝑁𝑁𝑁𝑁𝑁𝑁𝑐𝑐𝑠𝑠𝑠𝑠𝑐𝑐= 250 Hz. Quantization is defined upon the signal dynamic and quantization level employed, in terms of bits. For example, we may consider an ADC with FSR equal 5 V and 12 bits. As an example, considering ECG dynamic range approximately equa l to 60 mV each level of quantization q is equal to 5 𝑉𝑉 4096 ≃ 1 × 10−3𝑉𝑉= 1 𝑚𝑚𝑉𝑉 following a proper amplification of the recorded signal. At this point ECG signal is discrete in terms of both time and amplitude. b) Sketch a 5 -seconds duration trace of the signal you acquired. Report units and numerical ranges on the axes. 5 seconds of the signal you ac quired at poi nt a) means that x axis must report the scale in SAMPLES so 5 sec * fs = N of samples c) Design a filter to remove baseline wander in the acquired signal. Which kind of filter is…