Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
IEC 63098 — Transmitting Equipment for Radiocommunication — Methods of Measurement
Technical Report on Radio Transmitter Measurement Methods
1. Scope and Application of IEC TR 63098-1
IEC TR 63098-1 specifies standardised methods of measurement for transmitting equipment used in radiocommunication systems. Covering frequency ranges from HF through microwave bands, this technical report provides a comprehensive framework for characterising transmitter performance parameters including output power, frequency accuracy, modulation quality, spurious emissions, intermodulation distortion, and adjacent channel power. The standard is applicable to fixed, mobile, and portable radio transmitters operating in licensed and unlicensed spectrum.
While many radio equipment standards focus on type approval testing, IEC TR 63098-1 is designed for engineering development, factory acceptance testing, and field commissioning. Its measurement procedures are structured to be reproducible across different laboratories and test environments.
The standard addresses both analogue modulation schemes (AM, FM, PM) and digital modulation formats (PSK, QAM, OFDM, GMSK). For each modulation type, it defines the specific measurement configurations, test signal characteristics, detector types, and post-processing algorithms required to obtain repeatable results. The measurement uncertainty framework follows the ISO/IEC Guide 98-3 (GUM) methodology, ensuring that reported results include a statistically valid uncertainty budget.
| Parameter | Frequency Range | Typical Measurement Method | Uncertainty Target (k=2) |
|---|---|---|---|
| RF carrier power | 1 MHz – 40 GHz | Thermoelectric power sensor / spectrum analyser | ±0.5 dB |
| Frequency error | All bands | Frequency counter with GPSDO reference | ±1 × 10−9 |
| Adjacent channel power (ACP) | 30 MHz – 6 GHz | Channel power measurement with RBW correction | ±1.0 dB |
| Spurious emissions | 9 kHz – 40 GHz | EMI receiver / spectrum analyser with preselection | ±2.0 dB |
| EVM (error vector magnitude) | 100 MHz – 6 GHz | Vector signal analyser with demodulation | ±0.5% (EVM) |
| Intermodulation (IM3) | HF – microwave | Two-tone test with notch filter | ±1.5 dB |
2. Measurement Methods and Engineering Considerations
The standard defines three categories of measurement: conducted (directly at the transmitter RF output port), radiated (using calibrated antennas in an anechoic chamber or open-area test site), and coupled (using directional couplers or near-field probes in situ). For conducted measurements, the test setup must include appropriate attenuation to protect measurement instruments while maintaining signal fidelity. IEC TR 63098-1 specifies the maximum allowed VSWR (voltage standing wave ratio) at each interface point to minimise measurement uncertainty due to impedance mismatch.
One of the most common measurement errors is inadequate attenuation between the transmitter output and the spectrum analyser input. High-power transmitters (above 100 W) require careful cascade attenuation planning to avoid analyser front-end damage while keeping the signal above the noise floor. A good rule of thumb is to design the attenuation chain such that the analyser input level is between −30 dBm and −10 dBm for optimal dynamic range.
For digital modulation measurements, the standard provides detailed guidance on equaliser configuration during EVM measurements. The default recommendation is to use a reference equaliser that compensates for linear channel impairments without correcting for transmitter-specific nonlinearities. This approach ensures that the EVM measurement reflects the transmitter’s true modulation quality rather than the test system’s channel characteristics. The standard also addresses time-domain measurements such as transmitter ramp-up/ramp-down timing and burst power envelope for TDMA systems.
Implementing automated measurement sequences based on IEC TR 63098-1 can reduce test time by 60-80% compared to manual measurements. The standard provides explicit pass/fail criteria templates that can be programmed into vector network analysers and signal analysers for production-line go/no-go testing. This is particularly valuable for high-volume manufacturing of radio modules.
3. Engineering Design Insights for Transmitter Characterisation
From an RF engineering perspective, the choice of measurement detector type significantly affects results. The standard specifies the use of RMS detectors for digital signals (because the peak-to-average power ratio varies with modulation format and pulse shaping), while peak detectors are reserved for assessing transient phenomena such as power ramping and switching transients. Sample detectors are explicitly discouraged for modulated signals due to their statistical bias.
Cable and connector integrity is another critical but often overlooked factor. At frequencies above 6 GHz, the insertion loss and phase stability of the test cable assembly directly impact measurement repeatability. IEC TR 63098-1 recommends using phase-stable cables with torque-controlled connectors and performing a full two-port calibration at the measurement plane before each test session. The standard also specifies minimum cable bend radii and recommends against using adapters wherever possible, as each adapter introduces additional VSWR uncertainty.
The standard also covers the specific challenges of measuring broadband transmitters (e.g., 100 MHz instantaneous bandwidth). Traditional swept-tuned spectrum analysis is inadequate for such signals; instead, the standard mandates real-time spectrum analysis (RTSA) with sufficient bandwidth to capture the full instantaneous bandwidth of the transmitter. This is particularly relevant for modern software-defined radios and cognitive radio systems where frequency agility and adaptive modulation are inherent features.
4. Frequently Asked Questions
Q: Can IEC TR 63098-1 be used for 5G NR base station transmitter testing?
A: Yes, the measurement methods are applicable, but they should be supplemented by 3GPP TS 38.141 for 5G-specific parameters such as beam-specific EIRP and ACLR under different beam configurations. IEC TR 63098-1 provides the foundational measurement methodology.
A: Yes, the measurement methods are applicable, but they should be supplemented by 3GPP TS 38.141 for 5G-specific parameters such as beam-specific EIRP and ACLR under different beam configurations. IEC TR 63098-1 provides the foundational measurement methodology.
Q: What is the recommended calibration interval for test equipment used in these measurements?
A: The standard recommends annual calibration for most instruments, but power sensors and RF attenuators should be calibrated every 6 months due to their susceptibility to drift from thermal stress and connector wear.
A: The standard recommends annual calibration for most instruments, but power sensors and RF attenuators should be calibrated every 6 months due to their susceptibility to drift from thermal stress and connector wear.
Q: How should pulsed radar transmitters be measured?
A: Pulsed measurements require special attention to analyser sweep time and video bandwidth settings. The standard recommends using time-gated spectrum analysis with the gate synchronised to the radar pulse repetition interval, measuring within the pulse for peak power and across the full period for average power.
A: Pulsed measurements require special attention to analyser sweep time and video bandwidth settings. The standard recommends using time-gated spectrum analysis with the gate synchronised to the radar pulse repetition interval, measuring within the pulse for peak power and across the full period for average power.
Q: What is the minimum dynamic range required for the test system?
A: The test system dynamic range should be at least 20 dB greater than the specified spurious emission limit. For example, if the required spurious suppression is −60 dBc, the measurement system must have at least −80 dBc dynamic range, which typically requires notch filtering of the fundamental carrier.
A: The test system dynamic range should be at least 20 dB greater than the specified spurious emission limit. For example, if the required spurious suppression is −60 dBc, the measurement system must have at least −80 dBc dynamic range, which typically requires notch filtering of the fundamental carrier.
