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Quick Start

Install

pip install doppler-dsp

The wheel bundles all native dependencies — no system libraries required.

Optional extras

pip install "doppler-dsp[specan]"      # terminal spectrum analyzer
pip install "doppler-dsp[specan-web]"  # live spectrum analyzer web UI
pip install "doppler-dsp[cli]"         # compose / Dopplerfile pipeline CLI

See Install → Python for the full extras table.

Signal processing

LO — generate a complex tone

from doppler.source import LO

lo = LO(0.25)          # normalised frequency: 0.25 → Fs/4
iq = lo.steps(8)
print(iq)
# [1.+0.j  0.+1.j  -1.+0.j  0.-1.j ...]

FFT

from doppler.spectral import FFT
import numpy as np

x = (np.random.randn(1024) + 1j * np.random.randn(1024)).astype(np.complex64)
f = FFT(1024)
X = f.execute_cf32(x)  # complex64 in → complex64 out (~2× faster than float64)

FIR filter

from doppler.filter import FIR
from scipy.signal import firwin
import numpy as np

taps = firwin(63, cutoff=0.1, window="hamming").astype(np.float32)
filt = FIR(taps)
y = filt.execute(x.astype(np.complex64))

Resample

from doppler.resample import HalfbandDecimator

decim = HalfbandDecimator()
y = decim.execute(x.astype(np.complex64))  # 2:1 decimation

Streaming

Doppler streams IQ data over ZMQ. Transmit and receive on the same machine or across a network — the API is identical.

Publisher (Python)

from doppler.stream import Publisher
import numpy as np

pub = Publisher("tcp://*:5555")

samples = np.ones(1024, dtype=np.complex64)
pub.send(samples, sample_rate=1e6, center_freq=2.4e9)

Subscriber (Python)

from doppler.stream import Subscriber

sub = Subscriber("tcp://localhost:5555")

msg = sub.recv()
print(f"Received {len(msg.samples)} samples @ {msg.sample_rate/1e6:.1f} MHz")

C transmitter → Python subscriber

Build the C examples once, then mix and match:

make          # builds ./build/examples/c/transmitter, receiver, etc.

# Terminal 1
./build/examples/c/transmitter tcp://*:5555 cf32

# Terminal 2 (Python)
python - <<'EOF'
from doppler.stream import Subscriber
sub = Subscriber("tcp://localhost:5555")
while True:
    msg = sub.recv()
    print(f"seq={msg.seq}  samples={len(msg.samples)}")
EOF

Spectrum analyzer

doppler-specan opens a live FFT display in your terminal or browser.

Requires the specan or specan-web extra

pip install "doppler-dsp[specan]"      # terminal
pip install "doppler-dsp[specan-web]"  # browser

Demo mode (no hardware needed):

doppler-specan --source demo

Browser UI:

doppler-specan --source demo --web

The web UI is served at http://127.0.0.1:8765 by default. See Spectrum Analyzer for configuration options.

Pipeline CLI

Requires the cli extra

pip install "doppler-dsp[cli]"

doppler compose wires blocks into a processing pipeline defined in a YAML file.

doppler compose init --name my_pipeline
doppler compose up --file my_pipeline.yaml
doppler ps
doppler logs

See CLI & Pipelines and Dopplerfile for writing custom blocks.

Build from source

If you need the C library, examples, or Rust FFI bindings:

sudo apt-get install build-essential cmake pkg-config python3-dev python3-numpy

sudo pacman -S --needed base-devel cmake python python-numpy

sudo dnf install gcc gcc-c++ make cmake pkgconf-pkg-config python3-devel python3-numpy

sudo zypper install gcc gcc-c++ make cmake pkg-config python3-devel python3-numpy

brew install cmake python numpy

Windows

doppler does not target Windows natively — build under WSL2, a VM, or a container and follow the Ubuntu / Debian steps.

C++ compiler

gcc-c++ above is needed only for the optional ZMQ/stream component (the vendored libzmq is C++). The core C library and the rest of the Python package are pure C99 — drop it if you don't need streaming.

git clone https://github.com/doppler-dsp/doppler
cd doppler
make           # C library + examples
make pyext     # Python extensions
make test-all  # C + Python + Rust test suites

See Build from Source for CMake options, Docker, and platform-specific notes.

Next steps