A WiFi Router as the Device Under Test
At the Rohde & Schwarz booth at the EMC exhibition in Cologne this January, the demo setup next to the full-height instrument rack had an unexpectedly familiar device on the table:
An AVM FRITZ!Box — a consumer WiFi router that sits in millions of European homes.
Next to it: a double-ridged horn antenna. Behind it: a floor-to-ceiling instrument rack labeled R&S TS8996, filled with seven layers of measurement hardware. Above: a banner reading EMC & REGULATORY TESTING OF DUT WITH RADIO FUNCTIONALITY.
The FRITZ!Box was the point. Not as a simplified stand-in for a complex device — but as a precise representative of the product category that makes traditional EMC testing fundamentally inadequate: a device whose primary function depends on a continuously active radio link, and whose EMC test cannot be separated from the question of whether that radio link is still working.
The Problem: EMC Testing Assumes the DUT Is Silent
Traditional EMC test methodology was developed for products that are passive from a radio perspective during testing. A switching power supply, a motor drive, a microcontroller-based industrial controller — these emit unintentional electromagnetic noise, and the test measures that noise against limit lines. The DUT's function during the test is irrelevant to the measurement.
A WiFi router, a 5G smartphone, a Bluetooth headset, a connected ECU — these products are different. Their primary function is intentional radio transmission and reception. The radio is not a side effect of their operation. It is their operation.
This creates three distinct problems for EMC testing:
→ The DUT's own transmitter interferes with the EMC measurement — a WiFi radio transmitting at 2.4 GHz at +20 dBm will saturate an EMI receiver trying to measure unintentional emissions in the same frequency range. The measurement cannot proceed with the radio active.
→ But switching the radio off changes the DUT's operating state — power consumption, thermal conditions, software state, and the emission profile of the digital processing circuitry all change when the radio is disabled. An EMC measurement made with the radio off may not represent the device's actual operational emissions.
→ Regulatory testing requires the radio to be in a defined, controlled state — ETSI, FCC, and RED (Radio Equipment Directive) requirements specify that certain measurements must be made with the radio in specific configurations, which requires a controllable link to the DUT's radio subsystem throughout the test.
The TS8996 is R&S's answer to all three problems simultaneously.
The R&S TS8996: Easy Link Configuration and Monitoring
The system architecture diagram visible on the screen behind the demo table described the TS8996's solution precisely. The key elements:
→ R&S® SGP-B1(x4) signal conditioning unit — four signal conditioning channels handling the DUT's radio signals during the EMC test. This unit manages the over-the-air link between the DUT and the communications antenna inside the anechoic chamber, ensuring the link remains stable regardless of the test environment's RF conditions.
→ Communications antenna in anechoic chamber — the antenna that maintains the controlled radio link to the DUT. Physically separated from the EMI measurement antenna, allowing simultaneous radio link maintenance and emission measurement.
→ EMI test receiver / spectrum analyzer — the measurement instrument receiving from the test antenna and measuring the DUT's emissions against compliance limits.
→ R&S® ELEKTRA EMC test software — the orchestration layer coordinating all system elements: radio link control, test sequence execution, antenna positioning, measurement acquisition, and result evaluation.
→ Mast/TT controller + 3D turntable — automated antenna height and DUT rotation for full radiated emissions characterization.
The product card's three capability claims map directly to the three problems described above:
→ "Link control by R&S CMX and R&S CMW integrated in R&S ELEKTRA" — the radio link to the DUT is controlled by the same software that controls the EMC test sequence. The tester doesn't manage two separate systems; ELEKTRA handles both.
→ "Covers 2G/3G/4G/5G FR1/5G FR2/Wi-Fi®/Bluetooth®" — the complete spectrum of current wireless standards in consumer and automotive electronics, from legacy 2G through 5G mmWave and all major ISM band protocols.
→ "Optimized setup for stable over-the-air link" — the signal conditioning hardware maintains link stability even as the EMC test environment changes — when the chamber's RF conditions shift during frequency scans, antenna repositioning, or interference injection, the radio link to the DUT is maintained without the engineer having to manually reestablish it.
The Instrument Rack: A Complete Automated Test System in One Cabinet
The instrument rack — labeled R&S TS8996 with the maturo automation platform designation at the top — is a fully integrated system. Reading from top to bottom:
→ maturo platform controller + emergency stop — the system-level safety and automation controller. The red emergency stop button signals that this system operates with live RF stimulus that can reach hazardous levels at the DUT.
→ R&S CMW communication tester — the instrument that generates and monitors the radio link to the DUT. For a 5G device, this provides the base station simulation. For a WiFi device like the FRITZ!Box, it provides the access point that the DUT associates with during the test.
→ Routing and switching modules — signal path management between the multiple RF instruments in the rack and the anechoic chamber connections.
→ R&S ESW EMI Test Receiver (display showing ~400 MHz) — the compliance-grade measurement instrument capturing the DUT's radiated emissions while the radio link is maintained.
→ Multi-channel signal conditioning unit (8+ red coaxial connections) — the SGP-B1 units that condition and route the radio signals between the DUT's antenna and the communications antenna. The red coaxial harness represents the multiple signal paths maintained simultaneously for MIMO antenna configurations.
→ Signal generator — for injection of specific stimulus signals or interference scenarios during testing.
→ Dense RF switch matrix — the routing backbone that connects the multiple instruments to the multiple antenna ports and DUT connections, allowing software-controlled reconfiguration of the signal paths for different test configurations without physical reconnection.
→ Power distribution and Knürr rack infrastructure — the physical housing platform from Knürr, a specialist in precision instrument racks for T&M applications.
The rack represents approximately 50,000–150,000 EUR of measurement hardware — not as a collection of independent instruments, but as a single integrated system designed to be deployed in a test lab, validated as a unit, and operated through the ELEKTRA software without the test engineer interacting with individual instruments.
Radio Sensitivity in the Presence of a Jammer
The small display visible in image1 — partially readable as "RADIO SENSITIVITY IN PRESENCE OF THE JAMBER" [sic] — reveals a specific test scenario running during the demo: measuring the DUT's radio receiver sensitivity while an interference source (jammer) is simultaneously active.
This test scenario is directly relevant to the RED (Radio Equipment Directive) and ETSI harmonized standards that wireless products must comply with for European market access. The requirement is not just that the DUT's radio works in a clean RF environment — it must maintain a defined minimum receiver sensitivity even when in-band and out-of-band interferers are present at specified levels.
For a WiFi router like the FRITZ!Box, this maps to real-world conditions: a home where multiple WiFi networks, microwave ovens, baby monitors, and Bluetooth devices are all active simultaneously. The "jamber" in the test scenario represents those interferers, applied at controlled levels, while the TS8996 maintains the link to the DUT and measures whether the received signal quality remains above the threshold the standard requires.
This is the measurement that answers whether the product will work in the environment it is actually sold into — not the controlled RF environment of a development lab, but the electromagnetically noisy reality of European homes and offices.
The RED Compliance Dimension
The "regulatory testing" in the booth title refers specifically to compliance with the Radio Equipment Directive (RED, 2014/53/EU) — the EU regulatory framework that governs all products with radio functionality sold in European markets. RED requires demonstration that the product:
→ Does not cause harmful interference to other radio services
→ Can tolerate interference from other radio services without degradation below a defined level
→ Uses the radio spectrum efficiently
These three requirements cannot be validated separately from each other, or separately from the product's functional operation. A test system that can simultaneously maintain the DUT's radio link, measure its emissions, inject controlled interference, and evaluate its receiver performance — while coordinating all of these through a single software platform — is the direct implementation of what RED compliance testing requires.
The TS8996 with ELEKTRA is positioned as the instrument system that makes this testing tractable at production scale: a validated, calibrated, traceable measurement system that can run a complete RED compliance test sequence for a wireless product and produce the test report that supports the CE marking declaration.
What This Represents in the T&M Landscape
The TS8996 demo in Cologne sits at the intersection of two trends that are reshaping the compliance test equipment market.
The first trend is the proliferation of wireless functionality: products that previously had no radio — industrial sensors, automotive ECUs, home appliances, medical devices — are now incorporating WiFi, Bluetooth, Zigbee, or cellular connectivity. Each of these products requires radio regulatory testing that their predecessors did not. The test infrastructure for this category is growing faster than any other segment of the compliance test market.
The second trend is the integration of test disciplines that were previously separate: the radio communications test (is the link working?) and the EMC test (are the emissions compliant?) are now a single, inseparable measurement problem. The test equipment must handle both simultaneously, which is a fundamentally different system architecture from either a standalone EMI receiver or a standalone communications tester.
The R&S TS8996 — a rack of instruments unified by the maturo platform and ELEKTRA software — is a direct product of that convergence. The FRITZ!Box on the table was the clearest possible illustration of why: you cannot test a device whose function is its radio without keeping the radio on, and you cannot keep the radio on without a system sophisticated enough to manage the link while the measurement proceeds.
System observed: Rohde & Schwarz TS8996 Wireless DUT Test System · R&S maturo automation platform · R&S CMW communication tester · R&S ESW EMI Test Receiver · R&S SGP-B1 signal conditioning units · R&S ELEKTRA EMC test software · RF switch matrix · with AVM FRITZ!Box as DUT · double ridged horn antenna
All photos: Thomas · @SignalByThomas