AltraraAI
Simulators

Signal processing you can take apart.

Interactive simulators that run entirely in your browser, with every stage shown.

GPS simulator

Three linked simulators: the receiver, the satellites and constellation, and the ground segment that keeps them accurate.

  • GPS receiver
  • GPS satellite and constellation
  • GPS ground segment
Open

ADS-B receiver

Aircraft broadcasts on 1090 MHz, decoded stage by stage: preamble detection, bit slicing, CRC-24 with error correction, message fields, CPR position decoding, and what happens when messages overlap.

  • Aviation
Open

Counter-drone swarm RF

A drone swarm's control, telemetry, video and Remote ID emissions in a busy ISM band, and a multi-sensor receiver that detects, separates by hop pattern, and localizes each drone, scored against ground truth.

  • Counter-UAS
Open

Starlink user terminal

The receive side of a Starlink dish: satellite scheduling and handoffs, a drawable obstruction map, phased-array steering and beam patterns, the link budget with rain fade, and OFDM downlink sync and demodulation.

  • Starlink
Open

Starlink constellation

Orbital shells on a 3-D globe or real TLEs, inter-satellite laser links, coverage and gateways, terminal scheduling, routing latency against fiber, and a model of clock synchronization and what losing it breaks.

  • Starlink
Open

LoRa chirp spread spectrum

How LoRa radios reach far on little power: chirps, whitening, Hamming codes and interleaving, preamble detection and sync, decoding below the noise floor, symbol error rate for every spreading factor, and collisions with the capture effect.

  • IoT radio
Open

FM broadcast with RDS

The full FM stereo multiplex: pilot, L−R subcarrier and RDS, through the discriminator, pilot lock and stereo decode, to RDS block sync, error correction and the station name, with test-tone audio you can listen to.

  • Broadcast
Open

LTE cell search

How a phone finds an LTE cell: resource grid, PSS correlation, frequency offset correction, SSS and the physical cell ID, reference-signal channel estimation, and PBCH decoding of the MIB, with several cells on the air.

  • Cellular
Open

Direction finding and phased arrays

Finding where a signal comes from with an antenna array: phase-difference angle of arrival and its ambiguity, Bartlett and MUSIC spectra, calibration errors, steerable beams and nulls, and accuracy against the Cramér-Rao bound.

  • Direction finding
Open

AIS receiver

Ships sharing two VHF channels: GMSK bursts with NRZI, bit stuffing and HDLC framing, the demodulator and clock recovery, CRC and message fields, SOTDMA slot sharing, and a live chart and message log.

  • Maritime
Open

Meteor-M LRPT weather satellite

One satellite pass from horizon to horizon: Doppler and link budget, Costas loop and symbol timing, frame sync, Viterbi and Reed–Solomon decoding, and a cloud image built line by line, with dropouts at low elevation.

  • Weather satellite
Open

Pager (POCSAG)

Paging messages at 512, 1200 and 2400 baud: 2-FSK, preamble and sync detection, batches and codewords, BCH(31,21) error correction you can break on purpose, and pager screens that fill with made-up messages.

  • Paging
Open

FMCW radar

A car radar from chirp to detection: transmitted and received chirps, beat frequency, range and range-Doppler FFTs, CFAR detection, and how bandwidth and frame time set range and speed resolution.

  • Radar
Open

Blackman-Harris window

What windowing does to an FFT: leakage, sidelobes, resolution and noise, with Blackman-Harris compared against Hann, Hamming, Blackman, flat-top and Kaiser.

  • Signal processing
Open

Euler's helix

e^(iθ) = cos θ + i sin θ drawn along a time axis: a 3-D helix whose shadows are a cosine and a sine, the two counter-rotating helices inside every real cosine, and how sampling folds the rotation and its spectrum.

  • Signal processing
Open