Rohde & Schwarz has introduced the R&S NTS transfer standards, coaxial reference devices that carry RF power traceability to measurements up to 170 GHz. The figure places the new standards beyond the reach of most national-laboratory working standards in common coaxial lines and into the frequency territory where waveguide and D-band measurement now dominate commercial work.

A transfer standard is a calibrated device, typically a thermocouple or thermistor-based power sensor, that carries a unit of power from a national metrology institute to an industrial calibration laboratory. The laboratory measures the standard, compares the result against its certificate, and proves its own reference is in tolerance. Without such devices, any power meter reading above the highest traceable frequency is, by definition, an indication rather than a measurement.

The 170 GHz upper limit matters commercially. D-band, 110 GHz to 170 GHz, is the allocated study ground for sixth-generation radio and is the band where automotive radar test equipment, semiconductor characterization fixtures, and over-the-air chambers now need calibrated power readings. Calibration intervals, the certificate frequency points, and the stated measurement uncertainty at each point will decide whether industrial labs can adopt the NTS units without sending them back to Munich or a partner institute too often. Rohde & Schwarz has not yet published those figures in the announcement material available at press time.

What changes for calibration laboratories?

Until now, laboratories working above roughly 110 GHz in coax have depended on sparse national-institute capabilities or on waveguide-derived comparisons with limited availability. A commercially supported transfer standard from a major instrument vendor gives accredited labs a route to ISO 17025 traceable power calibration across the band in a single chain. That, in turn, shortens the loop for manufacturers who must show calibrated power levels for regulatory filings and for antenna-in-situ measurements.

The company describes the NTS family as unique in covering this range as transfer standards rather than as ordinary working sensors. The claim rests on the distinction between a sensor usable in day-to-day testing and a device whose stability, reflection behavior, and documented history qualify it to carry a certificate between laboratories. Buyers will want the datasheet values for long-term drift and voltage standing wave ratio at the top of the band before treating the uniqueness claim as proven.

Why traceability becomes a purchasing criterion above 100 GHz

At millimeter-wave frequencies, mismatch uncertainty grows because connector repeatability degrades and the physical size of a coaxial line approaches the wavelength. A 1.0 mm coaxial connector, the type used near 110 GHz and above, tolerates far less mechanical variation than a 3.5 mm line at 26.5 GHz. A transfer standard with well-characterized reflection coefficients reduces this dominant uncertainty term, which is often the largest single contributor in a high-frequency power budget. Choosing a traceable standard rather than an uncalibrated reference sensor is therefore not a paperwork decision; it directly changes the uncertainty a laboratory can quote to its customers.

Rohde & Schwarz has not stated pricing, delivery dates, or the identity of the national metrology institutes that will supply the calibration certificates. Those details, together with the published uncertainty budgets, will determine whether the NTS line becomes the default reference above 110 GHz or a niche product for the small number of labs already working in D-band.

The open question for accredited laboratories is compliance: can the NTS certificates slot into an existing ISO 17025 scope, or will each adoption require a new method validation at the upper frequency points?