Block 9 — IQ recording and analysis workflow¶

This block connects RF experiments to real IQ capture files. The main goal is reproducibility: record the file format, sample rate, center frequency, gain settings, I/Q ordering, endian format, duration and processing settings.

Engineering chain¶

flowchart LR
    RF[RF signal] --> RX[Receiver / SDR]
    RX --> IQ[IQ file]
    RX --> META[Metadata JSON]
    IQ --> READ[Reader: ci16/cu8/cf32]
    META --> READ
    READ --> QC[Quality checks]
    QC --> FFT[FFT / peak / SNR]
    FFT --> REPORT[Report artifacts]

Why metadata is mandatory¶

An IQ file without metadata is almost useless: frequency, format, scaling, bandwidth and gain settings are ambiguous. Every capture should have a companion JSON file.

Minimal metadata fields¶

Field	Why it matters
`sample_rate_hz`	correct FFT frequency axis
`center_frequency_hz`	RF reference for baseband data
`iq_format`	correct file reader
`i_first`	I/Q sample order
`endianness`	correct int16/float32 interpretation
`sample_count`	duration and file-size check
`gain_settings`	level reproducibility
`external_attenuation_db`	safety and level context
`expected_signal_offset_hz`	frequency-plan validation

Common IQ formats¶

Format	Description	Typical use
`ci16`	interleaved signed int16 I/Q	AD9363, custom SDR, SignalHound-like flows
`cu8`	interleaved unsigned uint8 I/Q	RTL-SDR raw captures
`cf32`	interleaved float32 I/Q	GNU Radio, MATLAB/Python processing

Capture quality checks¶

Before advanced processing, check that:

the file is not empty;
the size matches the format;
clipping is not excessive;
DC offset is not dominant;
peak frequency matches the frequency plan;
the noise floor is reasonable;
metadata matches the experimental settings.

Connection to previous blocks¶

Block	Connection to Block 9
Block 6	frequencies, gain, AD9363 settings
Block 7	TX/RX chain and DUC/DDC frequency plan
Block 8	synchronization, EVM/BER after reading real IQ

Minimal report¶

capture setup diagram;
metadata JSON;
IQ format parameters;
FFT plot;
peak frequency / frequency error;
SNR estimate;
clipping/DC offset checks;
conclusion on whether the recording is usable for further processing.