CALCULATORS / SIGNALS, SAMPLING AND DATA

Anti-alias-filter requirement estimate calculator

Single-pole low-pass attenuation at Nyquist; no complete anti-alias design.

signals-anti-alias-filter.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	nyquistHz	magnitude	attenuationDb
	500	0.196116	14.1497
	400	0.242536	12.3045

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

Nyquist attenuation target in dB14.15 ✓ passes

BASELINE INPUTS

sampleRate1000 Hzcutoff100 Hz

CALCULATED

nyquist500 Hz

magnitude0.19612

attenuationDb14.15

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Anti-alias-filter requirement estimate
# Scope: Single-pole low-pass attenuation at Nyquist; no complete anti-alias design.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

sampleRate = 1000 Hz
cutoff = 100 Hz

nyquist := sampleRate/2 [Hz]
magnitude := 1/sqrt(1+(nyquist/cutoff)^2)
attenuationDb := -20*log10(magnitude)

check Nyquist attenuation target in dB: attenuationDb >= 12

scenario alternative: sampleRate = 800 Hz

Calculated from your source · not saved

Baseline · Baseline

Nyquist attenuation target in dB14.15 ✓ passes

alternative · alternative

Nyquist attenuation target in dB12.30 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

nyquist: nyquist = sampleRate/2 [Hz]
magnitude: magnitude = 1/sqrt(1+(nyquist/cutoff)^2)
attenuation db: attenuationDb = -20*log10(magnitude)

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

sample rate: 1000 Hz
cutoff: 100 Hz

Calculated

nyquist: 500 Hz
magnitude: 0.196116
attenuation db: 14.1497

Assumptions and limits

Single-pole low-pass attenuation at Nyquist; no complete anti-alias design.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Anti-alias-filter requirement estimate. Inputs: sample rate; passband; interfering spectrum; attenuation target. Outputs: transition band; candidate order/model. Model scope: Sampled-data models with stated bandwidth and noise assumptions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: sample rate, passband, interfering spectrum, attenuation target
Outputs: transition band, candidate order/model
Modes: calculate, compare, sweep
Drawing: Signal, samples and spectrum

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS