Christmas card 2023

This year’s Christmas card shows a high-resolution reflection image of a metallic snowflake measured at 76.5 GHz. The image was generated with the new reflection option of our successful Radome Measurement System RMS-D-77/79G.

The metallic snowflake is scanned line by line with a precision linear stage and a reflection measurement is triggered every 1.6 mm. A high-resolution two-dimensional radar image is then calculated from the more than 24 thousand individual measurements using synthetic aperture radar (SAR) methods. SAR originally comes from remote sensing to measure high-resolution radar terrain maps from satellites or airplanes. Today, SAR methods are also used in automotive radar sensors to generate high-resolution radar maps of the environment almost independent of the weather conditions. The information can be used for automated parking applications, for example. In our measurement system, we use the technology to analyze the reflectivity of radar covers in high resolution. In doing so, we can detect and visualize even smallest defects (inhomogeneities) of about 2 mm size.

Our first Christmas card from 2016 was also measured with an SAR setup. With the integration in our product RMS-D, we are making this measurement available to our customers.

Please do not hesitate to contact us if you have any questions.

Specification of the Christmas card

• Measurement system:
  Radome Measurement System (RMS-C-77/79G) with SAR option
• Measurement aperture: 255 mm x 245 mm
• Resolution 126 x 126 pixels
• Measurement time: 5 min
• Acquired frequency range: 75 to 78 GHz (millimeter wave range)

Christmas card 2022

For the design of this year’s Christmas card, we were able to win MERCK as a specialist for color pigments. Colored pigments in automotive coatings have a significant influence on their radar behavior.

Due to newly implemented automated driving functions, such as automated overtaking, the requirements for radar sensors are increasing constantly. Since these sensors are typically placed on vehicle corners behind bumpers which are painted in the vehicle color, the radar influence of paints must be considered. Especially, conductive aluminum pigments, can have a negative effect on radar transparency. Our measurement technology provides our customers the ability to optimize their pigments and paints, to ensure optimal radar transparency. Beside research and development, our radar measurement systems are also used in production to test complete bumpers and therefore ensure that the radar sensors have a clean view through the bumper.
The idea for this Christmas card was born from our collaboration with MERCK. The ingredients: a good idea, a bit of ‘masking’ work, some of MERCK’s Meoxal® pigments (Aluminum Substrate based), a few colorants and some binder, 6 application- and masking steps – and all this created a wonderful painted candle. The candle was then measured in our lab with a robot-based Radome Measuring System (RMS) and here is the result…
The radar image shows the one-way transmission through the painted foil. You can clearly see the influence of the paint increasing with higher metal content. The first image shows the phase value, representing the electrical thickness, while the second image shows the transmission of the electromagnetic wave, and thus the attenuation.

Specification of the Christmas card

• Measurement system:
  Radome Measurement System (RMS-C-77/79G) with linear stage and robot, perisens
• Frequency: 76.5GHz
• Transmission (1way) image with 294 x 234 pixels (pixel size 1.5mm)
• PET foil with Dk=3.22 and d=350um
• Aluminum substrate based Meoxal® paint

With kind support from Merck

Christmas card 2021

Our Christmas card for 2021 shows our WiFi Channel State Information (CSI) analysis while the song “Jingle Bells” was being played with a trumpet.

The CSI is available in the received packet preamble of the OFDM (Orthogonal Frequency Division Multiplexing) based WiFi standards such as IEEE 802.11a/n/ac/ax. Typically, the receiver uses it for channel equalization to recover data and then discards it. But the WiFi CSI is very sensitive to the changes in wireless environment and by processing it over time, it is possible to use the WiFi chip as a sensor. This technology is called WiFi Sensing and its typical applications areas are human presence detection, gesture recognition, intrusion detection and contactless vital signal (breathing and heart rate) monitoring. These applications can be implemented on consumer devices and run parallelly with existing connections, without limiting the data transfer.

For our Christmas card, we created IEEE 802.11ax PHY (Physical Layer) baseband waveform using MATLAB. This waveform is then upconverted, transmitted and received over-the-air using Ettus X300 Software-Defined-Radios (SDRs) in 2.4 GHz band. The received signal was converted back to baseband and analyzed in MATLAB. The WiFi CSI amplitude was plotted in a spectrogram. In the spectrogram we can see the effect of finger movements of our colleague while he was playing “Jingle Bells” with a trumpet. Our WiFi CSI analysis framework uses signal processing algorithms and can perform more tasks, such as detecting and counting breathing movements of a person.

As we see on our Christmas card, the WiFi CSI can even track very small movements in the environment. Currently, access to the WiFi CSI is implemented only on small number of devices, which also limits the number of available applications basing on it. This situation is expected to be change with the upcoming WiFi Sensing standard IEEE 802.11bf and WiFi is expected to become a full sensing paradigm and change the way we interact with devices. Once the WiFi CSI becomes available on customer devices, processing it correctly for the target application will gain high importance.

More information about CSI sensing can be found in our publication “In-Vehicle Breathing Rate Monitoring Based on WiFi Signals” from the European Microwave Week (EuMW2020). Download here.

Specification of the Christmas card

• Measurement system:
  Ettus X300 Software-Defined-Radios and Laptop with MATLAB WLAN Toolbox
• Center frequency: 2.385 GHz
• Signal bandwidth: 40 MHz
• Packet format: IEEE 802.11ax Single User SISO (Single Input Single Output)
• Antennas: Stub antenna with 3 dBi gain
• Antenna polarization: Vertical

Christmas card 2020

Our Christmas card from 2020 was measured with our Radome Measurement System (RMS-D-77/79G) equipped with a scanning positioning unit.

It shows a spatially resolved 1way-transmission image of a Christmas tree sprayed onto a PET foil in amplitude and phase. The tree is sprayed in uni green and the balls in metallic silver paint. The 100um thick uni paint creates a 6 degree phase shift with minimal impact on the attenuation. The much thinner metallic paint of only 20um creates a phase shift of 10 degree and increases the 1way attenuation by 0.7dB. This shows the strong impact of metallic base coatings. The aluminium pigments in the metallic paint used to generate a visual flip-flop effect significantly increase the electrical density (=permittivity) from ~3 for the uni paint to ~30 for the metallic paint. This increases reflections and reduces the transmission which can become critical, especially for radar sensors used for highly automated driving functions.

Therefore, it is important to investigate the influence of paint and painted surfaces (e.g. bumpers) on automotive radar sensors. The RMS allows characterization of material including automotive  paint layers in thicknesses of only 10um. Automotive paint and pigment manufacturer are using the RMS system worldwide to analyze paints properties and develop more radar transparent paints.

Specification of the Christmas card

• Measurement system:
  Radome Measurement System (RMS-D-77/79G) with xy linear stages, perisens
• Frequency: 76.5GHz
• Transmission image with 51 x 84 pixels (pixel size 3mm)
• PET foil with Dk=3.22 and d=350um
• Unigreen paint with Dk=2.3 and d=100um
• Metallic silver paint with Dk=31 and d=20um