Question

Raw data, like that collected above, must normally be processed before it can be used in diagnosis or state recognition. In our case we want to design a system that wltell us if the muscle is flexed or relaxed based on the EMG reading. This can be done with the three-stage system, shown below Stage 2 Rectify (Absolute value of signal) Stage 3 Envelope (Smooth out into shape outline) Stage 1 Remove DC Center at y 0) Stagel: For stage 1 we want to remove the DC component of the signal so that it will be centered at y 0 instead of some other offset. Explain how you would remove the DC component from the raw signal. Design a general circuit to perform the operation explained. (Hint: briefly research notch filters andlor high passfilters). Attach a drawing of your circuit and provide element values for any components used. If results are not ideal or do not match data explain why Stage 2: For our basic signal classification technique, the most important part of the signal is the magnitude of fluctuation or voltage spikes observed. Due to this the positive or negative values of a spike are not important. To simplify the signal and make it easier for stage 3 we want to rectify the signal or make the readings entirely positive. Explain how you would rectify this signal. Design a general circuit to perform this operation. (Hint: Look at previous labs where a signal was made completely positive) Attach a drawing of your circuit and provide values for any components used.

Answer 1

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STAGE 1: If you want to remove particular frequencies from a signal, you generally use a notch filter or a high pass filter. A notch filter is used when you want to remove a single frequency or a narrow range of frequencies. However, in this case, we want to remove the 0 Hz component i.e dc. Thus, we design a high pass filter. Choose f_c > > 0 i.e f_c = 100 Hz Therefore R = 1K, C = 1.6 mu F Stage 2: For rectification, one of the simplest circuits to design is the full wave rectifier. This circuit converts all negative spikes to positive spikes and leaves the positive inputs understand.