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ZWMath›Signal processing›Z-transform and digital filters›Poles, zeros and stability›ZW-POLES-ZEROS-AND-STABILITY-002
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AreaSignal processingCourseSignal processingTopicZ-transform and digital filters
Signals and LTI systems3
  • Linear time-invariant systems
  • Impulse response
  • Linear transformation Linear algebra
Fourier series and transform2
  • Continuous Fourier transform
  • Fourier transform properties
Sampling, DFT and FFT3
  • Aliasing
  • Discrete Fourier transform
  • Complex nth root Complex analysis
Z-transform and digital filters3
  • Discrete transfer function
  • Poles, zeros and stability
  • Zero and pole Complex analysis
Time-frequency and images2
  • Short-time Fourier transform
  • 2D convolution on images

Exercise · ZW-POLES-ZEROS-AND-STABILITY-002 · ★☆☆ Basic

What is the zero of \(H(z)=1-0.4z^{-1}\)?

Choose one option.

Show answer
  • A. \(z=0.4\)

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Explanation

The zero satisfies 1-0.4z^{-1}=0, that is z=0.4. The option with z=2.5 appears when the power of z is solved in the wrong direction.

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Review the concept: Poles, zeros and stability

The poles and zeros of a discrete-time transfer function \(H(z)\) are the values of \(z\) where \(H(z)\) vanishes or diverges.

\[|p_k| < 1 \quad \forall k\]

More practice problems: poles, zeros and stability

  • ZW-POLES-ZEROS-AND-STABILITY-001 A system has H(z)=1/(1-0.6z^-1). Where is its pole?
  • ZW-POLES-ZEROS-AND-STABILITY-003 A causal system has a single pole at z=0.9. Is it stable?
  • ZW-POLES-ZEROS-AND-STABILITY-004 What condition must a pole of a causal system satisfy for the system to be stable?
  • ZW-POLES-ZEROS-AND-STABILITY-005 A system has H(z)=1/(1+0.5z^-1). Where is its pole?
  • ZW-POLES-ZEROS-AND-STABILITY-006 A causal system has H(z)=1/(1-1.2z^-1). Is it stable?
  • ZW-POLES-ZEROS-AND-STABILITY-007 Where are the zeros of H(z)=(1-0.3z^-1)(1+0.7z^-1)?
  • ZW-POLES-ZEROS-AND-STABILITY-008 A system has H(z)=(1-0.5z^-1)/(1-0.8z^-1). What are its pole and zero?
  • ZW-POLES-ZEROS-AND-STABILITY-009 A causal system has poles at z=0.5 and z=-1.5. Is it stable?

← ZW-POLES-ZEROS-AND-STABILITY-001 ZW-POLES-ZEROS-AND-STABILITY-003 →

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