mmWave Traceability for Signal Generation and Measurement

The big picture
Traceability boils down to establishing a chain of evidence reaching back SI units to prove the extent to which a system does what it’s supposed to do. Establishing traceability is central to NIST’s mission. Our many labs do this for all variety of systems vital to industry and scientific research, from lab thermometers to gas flow meters, from accelerometers to atomic frequency standards.  NIST’s traceability work helps scientists, engineers and others in industry, government and academia trust their measurements, boosting the consistency, interoperatibility, and quality of their products.

The NIST CTL establishes traceability for radiofrequency systems. In the case of our work in establishing millimeter-wave traceability for signal generation and measurement, we focus on the devices generating the modulated signals that antennas later emit as radio waves. This work is enabling end-to-end wireless-system measurements at mmWave frequencies, starting with a NIST-calibrated signal source and continuing though NIST-calibrated antennas, a known channel, and a NIST-calibrated end receiver. Combined, these measurements impart a high degree of certainty that the behaviors of the high-frequency signals these systems process and transmit are innate to the physical realities of mmWave communications – and not quirks in the systems dealing in them. Such knowledge stands to sharply accelerate the development of future 5G wireless communications.

What we do
Traceability in signal processing has not traditionally been a major wireless-industry concern, and for good reason: at the lower frequencies they’ve historically enjoyed, the data still comes through despite imperfect signals. But next-generation 5G wireless will depend on frequencies in the tens and hundreds of gigahertz. At these speeds, there’s less room for error, and so there’s a growing industry need for measurement systems that can ensure the accuracy of gigahertz waveforms. To this end, CTL’s mmWave traceability efforts focus on:

• Enhancing the NIST on-wafer electro-optic sampling (EOS) system, which uses ultrafast lasers to provide traceability for waveform measurements from 200 MHz into the terahertz range. Due to limits in the speed of today’s optoelectronic sources and broadband coaxial connectors, though, the system tops out at about 70 GHz.
• Improving methods of testing mmWave sources using rectangular waveguides at frequencies above those at which oscilloscopes are useful.
• Developing free-field measurements to verify device performance, with a focus on establishing tests methods using reverberation chambers, which can establish key performance metrics in a repeatable, cost-effective way.

For more detail on specific research initiatives related to this CTL program, please see our mmWave traceability for signal generation and measurement R&D Topics.

NIST Teams involved
Metrology for Wireless Systems Group
Waveform Metrology Project
High-Speed Electronics  Project