Compliance Testing for FM/AM/DAB/DMB Broadcast Receivers

Broadcast receivers cover FM (Frequency Modulation), AM (Amplitude Modulation), DAB (Digital Audio Broadcasting) and DMB (Digital Multimedia Broadcasting).

①　FM (Frequency Modulation) operates in the shortwave band and transmits analog signals.

②　AM (Amplitude Modulation) works in the medium-wave band and transmits analog signals.

③　DAB (Digital Audio Broadcasting) relies on digital communication signals and supports transmission of diverse signal types including high-fidelity audio.

④　DMB (Digital Multimedia Broadcasting) is an upgraded version of DAB that delivers multimedia services.

Testing for FM/AM/DAB/DMB broadcast receivers must cover multiple dimensions: RF performance, audio quality, function verification, environmental adaptability, and regulatory certification. Below is a systematic testing protocol.

RF Performance testing

1.1 Reception Sensitivity

Method: Input the minimum usable signal (e.g., 10μV for AM; -90dBm for DAB) via a signal generator to verify the receiver’s stable demodulation capability.

Tools: RF signal generator, anechoic chamber.

1.2 Selectivity (Anti-interference)

Adjacent/Co-channel Interference: Inject interference signals at ±10kHz of the target frequency (for AM) or adjacent channels (for DAB) to test the receiver’s suppression capability.

Metrics: AM shall meet a suppression ratio of >40dB at ±9kHz; DAB shall comply with the ETSI EN 302 077 standard.

1.3 Frequency Coverage and Stability

Band Coverage: Verify full-band tunability of medium wave (530–1600kHz), AM, and DAB (174–240MHz) bands.

Frequency Error: Use a frequency counter to measure local oscillator stability. The error shall be <±1kHz (for analog signals) or comply with digital broadcasting standards.

Audio Quality Testing

2.1 Objective Metrics

①　Signal-to-Noise Ratio (SNR): >40dB for AM; >60dB for DAB (uncompressed audio).

②　Total Harmonic Distortion (THD): <1% at rated output.

③　Frequency Response: 200Hz–3kHz (±3dB) for AM; 20Hz–15kHz for DAB (depending on encoding format).

2.2 Subjective Listening Evaluation

Test Scenario: Play standard test audio (e.g., human voice, music) and conduct blind scoring by professional evaluators.

Key Focus Areas: Latency in digital broadcasting; background noise in analog broadcasting.

Functionality and Compatibility Testing

3.1 Core Function Verification

①　Automatic Station Search: Test full-band scanning speed and storage accuracy (e.g., automatic Ensemble recognition for DAB).

②　Multi-mode Switching: Verify seamless transition between AM and DAB modes without muting or popping sounds.

③　Additional Functions: RDS (if applicable), Electronic Program Guide (for DAB), scheduled power on/off, etc.

3.2 Compatibility Testing

①　Mixed Signal Scenario: Simulate weak DAB signal conditions to test if the receiver automatically switches to AM (if equipped with hybrid reception function).

②　Data Services: Verify normal decoding of DAB text information and real-time traffic updates.

Environmental and reliability testing

4.1 Extreme Environment Adaptability

①　Temperature: Conduct operational testing at -20℃ to +60℃ to verify frequency drift and sensitivity changes.

②　Humidity: Run continuous operation for 48 hours at 85% RH to inspect circuit stability.

③　Vibration: Simulate vehicle-mounted environments (5–500Hz, 0.5g) to test structural durability.

4.2 Long-term Stability

①　Aging Test: Run continuous operation for 7 days to monitor issues such as system crashes and memory leaks.

②　Battery Life: Measure continuous operating time of portable devices at maximum volume (e.g., >8 hours).

Regulatory and Certification Testing

5.1 EMC/emi testing

①　Radiated Emissions: Comply with CISPR 25 (for vehicle-mounted devices) or en 55032 (for consumer-grade devices).

②　Immunity: Comply with en 61000-4-3 (RF field immunity >3V/m).

5.2 Safety Certification

①　Electrical Safety: Comply with iec 62368-1.

②　Radio Certification: Comply with fcc part 15 (US), CE-RED (EU), and SRRC (China).