The Lamp on the Table Is the Point
At the Gauss Instruments booth at the EMC exhibition in Cologne this January, the booth next to the TDEMI Ultimate had a different kind of demo running.
No rotating turntable. No biconical antenna on a tripod. No engineering evaluation board with gold-plated connectors.
Just a white table lamp. Switched on. Sitting next to a compact instrument chassis on a black desk — and on that instrument's screen, a two-layer display: a multi-trace EMI spectrum on top, and a broad green-to-yellow density plot filling the bottom half.
The banner above said: 40 GHz · Real-Time Scanning · TDEMI® Technology.
The product card below confirmed: TDEMI ULTRA Series · DC – 40 GHz · Best RF Performance. Lowest Noise Floor. The New Benchmark.
The lamp was the device under test. And that choice — a €15 consumer product as the EMI source — was making a more precise statement about this instrument than any spec sheet could.
DC to 40 GHz: What That Frequency Range Actually Requires
The TDEMI ULTRA's DC – 40 GHz coverage is not a marketing range. It is the complete span of frequencies that matter in modern EMC compliance testing, mapped onto a single instrument without mode-switching or external conversion for the lower portion of the range.
To understand what it covers:
→ DC – 150 kHz: below the CISPR conducted emissions range, but relevant for power quality and low-frequency magnetic field emissions
→ 150 kHz – 30 MHz: conducted emissions per CISPR 32, EN 55032, CISPR 25 — the switching regulator harmonics, clock fundamentals, and digital bus noise that show up on power lines
→ 30 MHz – 1 GHz: radiated emissions Class B range — the primary domain of most consumer electronics compliance testing
→ 1 GHz – 6 GHz: upper radiated emissions range for devices with intentional radiators, automotive radar pre-compliance, 5G sub-6 GHz
→ 6 GHz – 40 GHz: automotive 77 GHz radar precursor bands, 5G FR2 mmWave, satellite downlinks, military and aerospace
Covering this entire span in a single instrument — continuously, in real time, without re-configuring front-end hardware — is what "DC – 40 GHz" as a TDEMI specification claims. The extension to THz via external mixer preserves that architectural continuity into the ranges beyond what the instrument's native front-end can reach.
The Two-Layer Display: Spectrum and Behavior Simultaneously
The TDEMI ULTRA's screen shows two distinct views of the same signal, stacked vertically — and both views are live, running simultaneously from a single real-time acquisition.
Top layer: EMI spectrum with limit lines
Multiple colored traces — peak hold, average, quasi-peak, ambient reference — overlaid with horizontal limit lines. This is the compliance-oriented view: the engineer can see directly whether any emission exceeds the applicable standard limit, at which frequency, and by how much margin. The cursor and marker tools on the right panel allow specific frequency points to be interrogated without interrupting the live measurement.
Bottom layer: density/spectrogram display
The broad green-to-yellow field below the spectrum trace is a probability density representation — the same architecture described in Article 020's 510 MHz system, now operating across the full DC–40 GHz span. Green indicates emissions that appear occasionally; yellow and toward red indicates emissions present in the majority of acquisitions. The horizontal extent of the display maps to the full frequency range.
The combination of these two views in a single live display is the practical expression of the TDEMI architecture's core capability: the spectrum trace tells you what the emission levels are, and the density plot tells you how reliably those levels appear. An emission that shows up at −5 dB below the limit line but only appears in 10% of acquisitions is a fundamentally different engineering problem than one that sits at −5 dB below the limit in every single acquisition.
Traditional swept EMI receivers show you only the first type. The TDEMI shows you both.
Why a Table Lamp Is the Right DUT for This Demo
The table lamp on the demo desk is not a coincidence and not a simplification. It is a deliberate signal about the instrument's intended market position.
A table lamp with an LED driver is one of the most electromagnetically complex consumer products relative to its apparent simplicity. The switch-mode power supply inside a modern LED lamp generates conducted and radiated emissions across a wide frequency range — switching fundamental typically in the 50–150 kHz region, harmonics extending into the tens of MHz, and depending on layout quality, radiated components reaching into the hundreds of MHz. These emissions must comply with EN 55015 (lighting equipment) and CISPR 15, which specify limits across the conducted and radiated ranges.
A product that looks simple but generates complex EMI across a wide frequency span is exactly the kind of DUT that demonstrates real-time broadband capture's advantage over swept measurement. The conducted emissions from the lamp's LED driver don't stay at one frequency — they modulate with load, thermal state, and input voltage. Capturing the complete emission profile across the full frequency range simultaneously, as the TDEMI ULTRA does, means you see the complete picture in one acquisition pass rather than potentially missing frequency-time correlations during a multi-minute sweep.
The second device on the desk — a small electric appliance, possibly a shaver or similar — reinforces the same message: this instrument is positioned for the consumer electronics compliance market, where the DUTs are everyday products and the testing volume is high.
"Lowest Noise Floor. The New Benchmark." — What That Claim Requires
The product card's language — Best RF Performance. Lowest Noise Floor. The New Benchmark. — is specific enough to unpack technically.
In EMI measurement, noise floor determines the minimum detectable emission level. CISPR Class B limits for radiated emissions in the 30–230 MHz range start at 30 dBµV/m at 10 m. To have meaningful measurement margin, a receiver's noise floor needs to sit well below that limit — typically 10–20 dB below the lowest applicable limit line.
Achieving a low noise floor across a DC–40 GHz span in a real-time architecture is significantly harder than in a traditional narrowband superheterodyne receiver. The reasons are architectural:
→ A superheterodyne receiver filters aggressively at each frequency point, processing a narrow bandwidth and therefore a narrow noise bandwidth. Low noise is "free" because most of the spectrum is filtered out before reaching the detector.
→ A real-time wideband system processes a much larger instantaneous bandwidth. Every Hz of bandwidth captured contributes thermal noise. Maintaining low noise floor across 40 GHz of real-time capture requires a front-end with exceptional noise figure and an ADC with sufficient dynamic range to resolve weak signals in the presence of strong ones.
The "lowest noise floor" claim is therefore a direct statement about front-end RF performance: Gauss Instruments is asserting that their TDEMI ULTRA's real-time architecture achieves noise floor performance comparable to — or better than — the narrowband superheterodyne receivers it is positioned to replace. Whether that claim holds across the full DC–40 GHz range and under the specific detector conditions required by CISPR 16 is precisely the question a compliance engineer would want to verify before substituting a TDEMI for a certified EMI receiver.
The Architecture Behind the Numbers
DC – 40 GHz real-time scanning via TDEMI® technology describes a specific signal chain. The fundamental departure from traditional EMI receivers is at the detection stage:
→ Traditional superheterodyne: RF front-end → bandpass filter (RBW) → envelope detector → display. Frequency coverage via local oscillator stepping.
→ TDEMI architecture: wideband RF front-end → high-speed ADC → DSP/FPGA computing FFT → simultaneous frequency bins across the full capture bandwidth → software-implemented detectors (peak, quasi-peak, average, RMS) applied to the digitized IQ data stream.
The "real-time scanning" in the DC–40 GHz context means the system moves its real-time capture window across the full frequency range rapidly enough that no transient emission event lasting longer than the window dwell time is missed. The density plot is the visual evidence of this: it shows the statistical distribution of emissions across the full frequency range accumulated over the complete measurement duration, not just the instantaneous peak at a single moment.
The extension to THz range via external mixer is a logical consequence of this architecture. Above 40 GHz, the TDEMI front-end acts as the IF processing stage, with the external mixer performing the frequency downconversion. The software processing chain — FFT, detectors, density display, data storage — remains identical regardless of whether the input is native or downconverted.
Three Displays on One Booth, One Coherent Argument
Seen together, the three Gauss Instruments displays at this Cologne exhibition — the 510 MHz TDEMI S (Article 020), the 1000 MHz TDEMI Ultimate with 3D spectrogram (Article 021), and the DC–40 GHz TDEMI ULTRA — form a product family with a consistent architectural argument across three different performance tiers and three different target applications.
The 510 MHz S Series targets conducted EMI pre-compliance and development debugging, where a 510 MHz window covers the primary conducted emissions range and the IQ capture enables replay and multi-detector analysis.
The 1000 MHz Ultimate targets formal radiated emissions characterization, where the wider capture bandwidth enables the 3D spectrogram generation during automated turntable scans.
The DC–40 GHz ULTRA targets full-range compliance testing — the instrument that sits at the center of a compliance lab and handles everything from conducted power line emissions to upper radiated emissions bands, with the density display providing the intermittent-event visibility that justifies replacing a traditional swept receiver.
The table lamp on the desk was measuring its own electromagnetic biography — from DC through 40 GHz — in real time. That is what the TDEMI ULTRA is built to do.
Instrument observed: Gauss Instruments TDEMI® ULTRA Series · DC – 40 GHz Real-Time Scanning · TDEMI® Technology · "Best RF Performance. Lowest Noise Floor. The New Benchmark." · extendable to THz range via external mixer
All photos: Thomas · @SignalByThomas