Sampling, aliasing and anti-alias bandwidth
An ideal baseband signal containing no frequencies above B can be reconstructed from exact uniform samples at f_s>2B.
Key knowledge
An ideal baseband signal containing no frequencies above B can be reconstructed from exact uniform samples at f_s>2B. Frequencies differing by integer multiples of f_s can give the same samples; practical acquisition therefore needs an analog anti-alias filter, transition-band allowance and a known sampling clock.
Values and equations
f_s=1/T_s>2B; x(t)=Σ_n x[n] sinc(f_s t−n); sinc(z)=sin(πz)/(πz) for z≠0; sinc(0)=1
- f_s,B
- Sampling frequency and baseband cutoff Hz
- T_s,t
- Sampling interval and time s
- x(t),x[n]
- Continuous/discrete signal; its quantity unit unit of the measured signal
- n,z
- Integer sample label n from −∞ to ∞ and dimensionless interpolation argument z 1
Conditions and scope
- Ideal infinite uniform sampling of a suitably bandlimited signal; exact sinc reconstruction assumes unquantized samples and the specified bandwidth.
- Finite observation, sample-time jitter, filter leakage and quantization introduce error. Digital filtering after sampling cannot recover information already lost to aliasing.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Biomedical Signal Processing: Chapter 1, analog-to-digital conversion: Pages 3–5, §§1.1.2 and 1.2: sinusoid aliasing, Nyquist criterion, sinc interpolation and analog-filter transition/noise warning.
Ideal bandlimited sampling, aliasing and cardinal interpolation use normalized sinc with its continuous value sinc(0)=1.
2026-10-10 · Independent Chemistry, Biology and Earth/Cosmos editor (AI editorial review). Source checks and independent AI editorial review of compact reference claims, equations, units, conditions and conceptual mappings. This is not human specialist certification, laboratory accreditation, whole-book verification, or a claim that all possible foundational knowledge is present.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Scope or convention differs
Ideal uniformly sampled baseband bandlimited signals can be reconstructed by normalized sinc interpolation when sampling exceeds twice bandwidth.
The printed theorem allows equality at Nyquist; ARK uses a strict inequality and keeps practical anti-alias filtering and hardware limitations explicit.
Indian Institute of Technology Bombay · Department of Electrical Engineering
- EE210 Signals and Systems · Handout11 IndiaEnglish
6 Sampling theorem, equations17–21, PDF pp9–11
- EE210 Signals and Systems · Handout11
Entry details
Permanent link to this entry ↗- Record identity
- measurement-sampling-aliasing
- Revision
- foundations-audit.1
- Structured reference record
- University core expansion