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Signal analyzer DAB
DAB (Digital Audio Broadcasting) is a digital radio broadcasting standard designed to transmit audio programmes and associated data using terrestrial radio transmitters. It was developed as an alternative to traditional analogue FM broadcasting, offering more efficient use of the radio spectrum and additional features for broadcasters and listeners.
DAB allows multiple radio stations to be transmitted together within a single frequency block, known as a multiplex. Listeners can receive these services using a compatible DAB receiver and an appropriate antenna.
Typical bandwidth used by DAB channel is 1.536 MHz.
DAB analyzer looks for a DAB Mode I OFDM signal and displays differential DQPSK constellation information.
- FIC - Fast Information Channel. Part of the DAB multiplex that carries control and configuration information required for the correct reception and decoding of the broadcast signal. The FIC is transmitted as part of every DAB transmission frame. A receiver can decode it to obtain multiplex information without first decoding the audio of a specific radio station.
- OFDM - Orthogonal Frequency Division Multiplexing. DAB uses many narrow carriers in parallel.
- DQPSK - Differential Quadrature Phase Shift Keying, the modulation used by DAB carriers.
- Contrast - level difference used to detect the DAB null symbol and useful OFDM symbol energy.
- Offset - estimated frequency offset of the detected DAB ensemble.
- Null - strength of the null-symbol detection.
- CP - cyclic prefix timing correlation.
- CFO - carrier frequency offset in Hz.
The DAB constellation panel shows differential carrier points. A clean DAB signal should form stable clusters. Spread or rotating points usually indicate low SNR, wrong tuning, insufficient bandwidth or overload.
DAB Mode I uses about 1.536 MHz of useful carrier bandwidth. Select a channel bandwidth wide enough to include the whole ensemble, and avoid clipping in the I/Q analyzer.