[...]... Goldberger and J Ng (eds.), Practical Signal and Image Processing in Clinical Cardiology, DOI: 10.1007/97 8-1 -8 488 2-5 1 5-4 _1, © Springer-Verlag London Limited 2010 3 4 J Ng and J.J Goldberger Fig. 1.1 Block diagram of basic digital physiologic recording system Table 1.1 Examples of physiologic recording systems and the corresponding transducer and physiologic measurement Physiologic recording Transducer... surface and cardiac motion are continuous functions in time and amplitude J Ng () Department of Medicine, Division of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA e-mail: jsnng@northwestern.edu J.J Goldberger and J Ng (eds.), Practical Signal and Image Processing in Clinical Cardiology, DOI: 10.1007/97 8-1 -8 488 2-5 1 5-4 _2, © Springer-Verlag London Limited 2010 9 10 J Ng. .. of Medicine, Division of Cardiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA e-mail: jsnng@northwestern.edu J.J Goldberger and J Ng (eds.), Practical Signal and Image Processing in Clinical Cardiology, DOI: 10.1007/97 8-1 -8 488 2-5 1 5-4 _3, © Springer-Verlag London Limited 2010 17 18 J Ng and J.J Goldberger Figure 3.1 shows the sine waves with frequencies corresponding to the... continuous amplitude signal ›› Digital signal – Signal characterized by discrete time points and discrete amplitude values having a defined sampling rate and amplitude resolution ›› Sampling – The process of obtaining data points from an analog signal at defined intervals The frequency of the sampling is known as the sampling rate ›› Quantization – The process of assigning sampled data points to discrete... results in a more accurate representation of the true signal than transmitting the original analog signal 2.4 Analog-to-Digital Conversion 2.4.1 Sampling The process of converting an analog signal to a digital signal has two parts: sampling and quantization The sampling process converts a continuous time signal to a discrete time signal with a defined time resolution The time resolution is determined... important in the field of signal processing Concepts such as filtering, sampling, and periodicity detection require at least a basic understanding of the frequency domain 3.2 What is the Frequency Domain? Audio and music are perhaps the applications where most people have experienced working in the frequency domain A single tone or note (e.g., from a piano or guitar) corresponds primarily to a sine wave... reconstructed signal in this case resembles a 2-Hz sine wave, rather than an 8-Hz sine wave Distortion to the point where the original sine wave is unrecognizable because of undersampling is known as aliasing Stated differently, if the signal is changing at a frequency that is faster than the sampling rate, important information about the signal will be lost Consider the three signals in Fig. 2.3 –... multiplying a rounded waveform to the signal as illustrated in Fig. 3.6 Hanning and Hamming windows are two commonly used windows As shown in Fig. 3.6, the power spectrum of a sine wave multiplied with the rectangular window, a window with no attenuation, shows ripples adjacent to the main peaks while the power spectrum of the sine wave multiplied with a Hanning window has a power spectrum with a single... recognized Decreasing 12 J Ng and J.J Goldberger Fig. 2.2 Plots showing a sine wave with a frequency of 8 Hz sampled at rates of 100, 25, and 10 Hz The reconstructed signal with 10 Hz sampling shows aliasing, the distortion resulting from undersampling the sampling rate even further can result in a completely distorted reconstruction of the signal The bottom example of Fig. 2.2 shows the sine wave sampled... required in situations where short time segments are necessary, frequency resolution can be increased using an additional step known as zeropadding prior to applying the FFT Zero-padding essentially increases the length of the segment by appending zero values to the segment to obtain the desired frequency resolution without adding additional power to the signal For example, if we take a 1-s window of the signal . USA Part Fundamental Signal and Image Processing Concepts I 3 J.J. Goldberger and J. Ng (eds.), Practical Signal and Image Processing in Clinical Cardiology, DOI: 10.1007/97 8-1 -8 488 2-5 1 5-4 _1, © Springer-Verlag. x0 y0 w1 h1" alt="" Practical Signal and Image Processing in Clinical Cardiology Jeffrey J. Goldberger • Jason Ng (Eds.) Practical Signal and Image Processing in Clinical Cardiology Jeffrey. the clinical cardiologist, a beginner in the biomedical engineering eld may also nd the review of concepts useful before requiring a more in- depth signal processing text. Signal processing