Acquisition.jl

GNSS signal acquisition using the FM-DBZP (Frequency-domain Modified Double Block Zero Padding) algorithm (Heckler & Garrison, 2009).

Part of the JuliaGNSS ecosystem. Works with GNSSSignals.jl for signal definitions.

Features

• FM-DBZP algorithm — joint code-phase and Doppler search via a 2-D FFT structure; simultaneous correlation across all code phases and Doppler bins in a single pass
• Pre-computed plans — reuse FFT plans and pre-allocated buffers across acquisitions with plan_acquire / acquire! for zero-allocation hot paths
• Multi-threaded — PRNs processed in parallel automatically when Julia is started with multiple threads (julia -t N)
• Non-coherent integration — accumulate power across multiple signal segments to improve sensitivity at low CN0
• Data bit handling — bit-edge search and sign-combination search for coherent integration spanning GPS L1 C/A data bits
• CFAR detection — built-in constant false alarm rate threshold via is_detected / cfar_threshold
• Sub-sample interpolation — parabolic interpolation for Doppler and code-phase refinement below grid resolution
• Plotting — visualise correlation power surfaces directly with Plots.jl

Installation

using Pkg
Pkg.add("Acquisition")

Quick Start

using Acquisition, GNSSSignals
import Unitful: Hz

system = GPSL1()

# Generate a synthetic GPS L1 signal for PRN 1
(; signal, sampling_freq, interm_freq) = generate_test_signal(system, 1)

# Acquire PRNs 1–32
results = acquire(system, signal, sampling_freq, 1:32; interm_freq)

# Filter to detected satellites (CFAR, 1% false alarm probability)
detected = filter(is_detected, results)

Reusing a Plan

For repeated acquisitions (e.g. processing a recorded file), pre-compute a plan once to avoid repeated FFT planning and memory allocation:

plan = plan_acquire(system, sampling_freq, collect(1:32))
results = acquire!(plan, signal, 1:32; interm_freq)

Non-coherent Integration

At low CN0, accumulate power across multiple successive signal segments:

plan = plan_acquire(system, sampling_freq, [1];
    num_coherently_integrated_code_periods = 10,
    num_noncoherent_accumulations = 8)

results = acquire!(plan, long_signal, [1])

Plotting

using Plots

result = acquire(system, signal, sampling_freq, 1;
    interm_freq, store_power_bins = true)
plot(result)

Documentation

See the documentation for the full usage guide, algorithm details, and API reference.

License

MIT License