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IEC 62273-1: Performance Measurement of Terrestrial Digital Television Transmitters
Standardized Test Methods for DVB-T, ATSC, and ISDB-T Transmitter Systems
1. Measurement Conditions and General Characteristics
IEC 62273-1 establishes uniform test conditions and measurement methods for assessing the performance of terrestrial digital television transmitters. Covering all major digital terrestrial television standards including DVB-T (Europe), ATSC (North America), and ISDB-T (Japan/Brazil), the standard ensures that measurements performed by different personnel across different organizations yield comparable and repeatable results. The standard addresses both type approval testing in factories and acceptance testing on site.
The measurement environment is strictly controlled. Temperature and humidity must be maintained within the equipment’s specified range without condensation. Primary power supply conditions are held at nominal voltage within ±2 % and nominal frequency within ±1 % of specified values. The test load impedance must match the transmitter’s designed characteristic impedance, with VSWR tolerances defined in the transmitter’s technical specification. Critical auxiliary equipment such as pass-band filters or multiplexing units must be included during testing if referenced in the technical specification.
Always verify the ASI (Asynchronous Serial Interface) input signal quality using an eye-height measurement before conducting transmitter performance tests. A degraded eye diagram indicates poor input signal integrity that will invalidate all downstream transmitter measurements.
Test signals for performance measurement use a PRBS 223-1 pattern with 8K COFDM 64-QAM 7/8 code rate and 1/4 guard interval as the default configuration unless otherwise specified for a particular system. This standard test signal provides a reproducible reference that exercises the full dynamic range of the transmitter’s modulation chain.
| Measurement | Default Test Signal | Key Instrument | RBW Setting |
|---|---|---|---|
| Output Power | PRBS 223-1 8K 64-QAM 7/8 ¼ | Bolometer / Spectrum analyser | 30 kHz |
| Spurious Emission | PRBS 223-1 8K 64-QAM 7/8 ¼ | Spectrum analyser with filter | 1 kHz – 1 MHz |
| Out-of-Band Emission | PRBS 223-1 8K 64-QAM 7/8 ¼ | Spectrum analyser | 4 kHz (DVB-T) / 10 kHz (ISDB-T) |
| Occupied Bandwidth | PRBS 223-1 8K 64-QAM 7/8 ¼ | Spectrum analyser | 4 kHz / 10 kHz |
| Intermodulation (Shoulders) | PRBS 223-1 8K 64-QAM 7/8 ¼ | Spectrum analyser | Per system specification |
2. Transmitted Signal Quality Metrics
The standard specifies several critical metrics for quantifying signal quality. Intermodulation distortion (shoulder attenuation) is a key concern for COFDM-based systems. The multi-carrier nature of COFDM makes it particularly sensitive to transmitter non-linearity, which generates unwanted spectral energy both in-band (degrading the transmitted signal) and out-of-band (causing adjacent channel interference). The shoulder attenuation measurement quantifies the out-of-band emission caused by intermodulation, and should ideally be performed without the output filter to reveal the true transmitter linearity.
Modulation Error Ratio (MER) measures the aggregate signal degradation by comparing the ideal constellation points against the received symbols in the I/Q plane. MER captures the combined effects of phase noise, I/Q imbalance, amplifier compression, and filter group-delay distortion. For DVB-T systems, MER is typically measured using the post-FFT constellation with equalization enabled, providing a direct indication of the signal quality that a consumer receiver would experience.
Bit Error Ratio (BER) testing is performed before and after Reed-Solomon decoding. The pre-RS BER indicates the raw channel quality, while the post-RS BER confirms whether the error correction is operating effectively. The standard also defines Equivalent Noise Degradation (END), which expresses the total transmitter impairment as an equivalent increase in receiver noise figure, enabling straightforward link budget calculations.
Phase noise measurement is critical for Single Frequency Network (SFN) operation. In SFN mode, all transmitters must maintain frequency within tight tolerances to avoid inter-carrier interference (ICI) and common phase error (CPE) at the receiver. The standard specifies that frequency stability for SFN transmitters may require tighter limits than those defined by the ITU Radio Regulations.
3. Frequency Control and Emission Compliance
Frequency accuracy for digital television transmitters is governed by both the ITU Radio Regulations and the specific requirements of SFN operation. The standard defines characteristic frequency as the identifiable frequency component within the occupied band that corresponds to the assigned channel frequency. Frequency drift — the uncontrolled continuous variation of frequency over time — must be characterized through short-term and long-term measurements using a recording instrument.
The standard provides detailed methods for measuring spurious domain emissions and out-of-band domain emissions, with the boundary between the two set at ±250 % of the necessary bandwidth. Spurious emissions include harmonics, parasitic oscillations, and intermodulation products that fall outside the necessary bandwidth. The measurement setup uses a directional coupler bridging the output transmission line, connected to a spectrum analyser with a minimum dynamic range of 70 dB. For high-power transmitters, appropriate filters extend the measurement dynamic range by suppressing the fundamental signal.
A key engineering insight: the occupied bandwidth of a COFDM signal is defined as the bandwidth containing 99 % of the total mean power. This measurement, performed with the spectrum analyser in channel power mode, provides a definitive check that the transmitter’s output spectrum complies with the allocated channel mask.
Safety requirements follow IEC 60215, protection against atmospheric discharge follows established methods from IEC 60244-1, and acoustic noise measurements ensure the transmitter meets workplace noise regulations. The standard also includes multiple informative annexes covering eye-height characteristics (Annex A), characteristic frequency determination (Annex B), frequency drift measurement (Annex C), directional coupler calibration (Annex D), and detailed measurement procedures for spurious/out-of-band emissions (Annex E), shoulder attenuation (Annex F), MER (Annex G), and BER (Annex H).
Frequently Asked Questions
Q: Does IEC 62273-1 apply to all digital television standards or only DVB-T?
A: The standard covers DVB-T, ATSC, and ISDB-T systems. Where measurement parameters differ between systems (e.g., RBW settings for out-of-band emissions), the standard provides separate specifications for each system in tables and annexes.
Q: Why is the calorimetric method preferred for output power measurement of high-power transmitters?
A: For transmitters above several kilowatts, the calorimetric method (measuring the temperature rise of water circulating through the test load) provides the most accurate and direct measurement of true RMS power, independent of waveform crest factor or modulation characteristics.
Q: What is the significance of the “shoulder” measurement in COFDM transmitters?
A: The “shoulder” refers to the spectral regrowth on either side of the COFDM channel caused by transmitter non-linearity. It directly measures adjacent channel interference potential and is one of the most sensitive indicators of amplifier linearity and predistortion correction effectiveness.
Q: How does SFN operation affect transmitter frequency requirements?
A: In SFN mode, multiple transmitters broadcast the same signal on the same frequency. Any frequency offset between transmitters creates inter-carrier interference (ICI) at receivers in overlapping coverage areas. SFN frequency tolerances are typically 10-100 times tighter than non-SFN operation.
