## ECE 222-3: Errata in Signals & Systems, Oppenheim & Willsky

This web page lists known errata in Oppenheim & Willsky's Signals & Systems, 2nd ed. - 1st Printing, Copyright 1997, ISBN 0-13-814757-4.

### Chapter 1

• Page 20: One of the exponents in equation 1.39 is missing the variable t.

### Chapter 2

• Page 109: The left sides of the four equations after (2.65), which are not labeled, should list y[n] and y(t) on the left hand sides rather than x[n] and x(t), respectively.
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### Chapter 3

• Page 191: Just below equation 3.39 the word "fundamental" is misspelled as "fundamnetal".
• Page 224: Near the bottom of the page "whenever" is misspelled as "whenver".
• Page 250: In the second paragraph "attenuate" is misspelled as "attentuate".

### Chapter 5

• Page 391: In Table 5.1 under "Symmetry for Real, Even Signals" the "Aperiodic signal" should list "x[n] real _and_ even". The letter "d" is missing from the word "and".

### Chapter 6

• Page 443: The last sentence in the first paragraph should end with "... sum of the impulse responses - i.e.,".

### Chapter 8

• Page 586: The third line states "... x(t) is recoverable from y(t) only if wm > wc, since ..." The condition should be "... only if wm < wc, since ..."
• Page 592: The signal plotted for the voltage w(t) in Figure 8.11b is incorrect. The RC part of the circuit shown in Figure 8.11a acts like a first-order lowpass filter. Since the signal is 0 approximately half of the time, the signal w(t) should be centered at less than half the average amplitude of the envelope. It would not reach each of the peaks shown and its variation would be significantly less than the variation of the envelope.
• Page 595: In the second and third plots from the top of Figure 8.16, the center of the spectra on the right is labeled with a negative frequency (it should be +wa and + wb).
• Page 614: The book states that "the modulating signal has a phase difference of pi/2 in relation to the amplitude-modulated carrier." This is wrong. The modulated components have different phase shifts, 0 and pi, from the carrier, not pi/2.
• Page 616: The word "the" is used twice in the first line of the first paragraph.