Why EMI/EMC Certification Labs Need a 40 GHz Signal Generator

Today, EMI (Electromagnetic Interference) and EMC (Electromagnetic Compatibility) certification laboratories find themselves managing increasingly high frequencies. A signal generator that reaches 40 GHz is not a technological luxury, but an indispensable work tool dictated by stringent regulations, new wireless technologies, and geometric calibration needs.

Here are the main reasons divided by technical area:

Many international standards mandate emission and immunity testing well beyond the classic frequencies used in consumer electronics of the past.

• FCC Part 15 (USA) & ANSI C63.4: The Federal Communications Commission requires that, for digital devices with high internal operating frequencies, radiated emission measurements must be extended up to the fifth harmonic of the highest frequency or up to 40 GHz (whichever is lower).
• MIL-STD-461 (Military) & DO-160 (Avionics): In radiated susceptibility testing (such as the well-known RS103 procedure), devices intended for military, aerospace, or satellite use must demonstrate that they can withstand intense electromagnetic fields generated within a frequency range that reaches precisely 40 GHz (and in some cases exceeds it).

While spectrum analyzers or measurement receivers are primarily used to measure emissions produced by an object (EMI), for immunity testing the laboratory must create the disturbance to see if the equipment under test (EUT) stops functioning properly.

• The signal generator is the "engine" that creates the carrier wave (CW) or the modulated signal at very low power.
• This signal is then sent to a broadband power amplifier (often based on GaN technology or TWT tubes) and finally radiated inside the anechoic chamber toward the product using specific horn antennas. Without a 40 GHz source, it would be impossible to test the product's resilience at such frequencies.

The civil telecommunications landscape has shifted massively toward the millimeter wave (mmWave) spectrum:

• 5G FR2 (Frequency Range 2): Next-generation mobile networks exploit frequency bands around 24 GHz, 28 GHz, and 39 GHz. Laboratories must test radio compliance and blocking immunity for devices embedding these antennas.
• SatCom and Radar: Ka-band satellite communications and automotive or industrial radar systems operate in these portions of the spectrum. Covering up to 40 GHz allows for the analysis of the fundamental frequencies of these systems or their primary harmonics.

A certification laboratory must guarantee measurement uncertainty. Before executing any test, the entire RF chain must be calibrated.

• The signal generator up to 40 GHz is used to inject reference signals into cables, RF switch matrices, and attenuators, and to calculate path loss (the signal loss along the path).
• It is also utilized for the validation of the test site itself (for instance, for site VSWR tests of the chamber), ensuring that the anechoic chamber responds correctly even at the highest frequencies.

Yes, absolutely. In the Italian context, compliance and technical requirements are not established by purely local laws isolated from the rest of the world, but rather by the transposition of European Directives and the adoption of technical standards from the CEI (Comitato Elettrotecnico Italiano).

Owning a generator up to 40 GHz fits into the Italian legal and regulatory framework through specific dynamics.

Any electrical or electronic device placed on the Italian market must bear the CE Marking. In order to apply it, manufacturers must demonstrate compliance with the Italian decrees that transposed the European directives:

• D.Lgs. 128/2016 (transposition of the RED Directive 2014/53/EU for all equipment integrating radio functions).
• D.Lgs. 80/2016 (transposition of the EMC Directive 2014/30/EU for the electromagnetic compatibility of non-radio equipment).

These decrees mandate compliance with "essential requirements" for non-interference and immunity, delegating to Harmonized Standards (technical) the task of defining frequency limits and practical tests to be performed in the laboratory.

There are harmonized reference standards in Italy that explicitly require testing up to 40 GHz:

• CEI EN 300 440 (developed by ETSI): This is the standard applied in Italy for Short Range Devices (such as commercial radar sensors, smart data transmission modules, advanced alarms). The very title of the standard specifies its scope of application: "from 1 GHz to 40 GHz". To test the immunity of these objects, the Italian laboratory must generate signals within that range.
• 5G Standards (mmWave Bands): European specifications adopted in Italy for next-generation mobile networks (for Base Stations and terminals operating at 26 GHz or 39 GHz) dictate spurious emission and blocking immunity testing that push instrumentation beyond the fundamental frequency, establishing a firm requirement for 40 GHz capacity.
• CEI EN 55011 (CISPR 11): Used in Italy for industrial, scientific, and medical (ISM) equipment. If an industrial machine or a medical device internally generates high frequencies, the standard requires extending radiated emission measurements up to 40 GHz to capture higher harmonics.

In the previous section, American (FCC) and military (MIL-STD) standards were mentioned. Do they have legal value in Italy?

• For Italian Exporting Companies (FCC): The Italian industrial fabric (SMEs, automotive, automation) thrives on exports. An Italian EMC laboratory must possess 40 GHz instrumentation to enable Italian companies to test and certify their products according to FCC rules before shipping them to the USA.
• For Italian Defense (MIL-STD / STANAG): The Italian defense industry (e.g., Leonardo and its supply chain) designs equipment that must comply with NATO standards. NATO Standardization Agreements (called STANAG) directly inherit and integrate the procedures and frequency limits (up to 40 GHz) defined by American MIL-STD-461 documents.

In Italy, the sole national accreditation body for laboratories is ACCREDIA. When an Italian laboratory applies for accreditation to perform tests according to the aforementioned standards (under the UNI CEI EN ISO/IEC 17025 quality standard), ACCREDIA inspectors physically verify that the laboratory possesses generators and measurement chains calibrated and functional up to the maximum frequency declared by the standard. If the standard says 40 GHz, the laboratory must have the 40 GHz instrument with a valid calibration certificate.