News

We were pleased to welcome Prof. Dustin Schroeder from Stanford University to the Institute of Microwave Engineering. As part of the KoRaTo seminar, he gave a talk on his interdisciplinary research on radar systems and the geophysical interpretation of the resulting data, with applications ranging from Antarctic ice sheets to icy moons.

We congratulate Julian Kanz on receiving the “Südwestmetall-Förderpreis” for his outstanding dissertation on “System Concepts for Multistatic UAV-Borne Synthetic Aperture Radar”. Congratulations!

Thesis: System Concepts for Multistatic UAV-Borne Synthetic Aperture Radar

Image: SWM/Eppler

Next week, we will be presenting two papers at the European Conference on Antennas and Propagation (EuCAP) in Dublin. On Tuesday, April 21, at 1:30 p.m., we will present a poster in the session “Aerospace, space, and non-terrestrial networks.” In addition, on Friday, April 24, at 9:10 a.m., we will give a presentation in the session “Computational and Numerical Techniques: Array Analysis and Design.”

Within the framework of a Joint Communication and Sensing (JCAS) approach, communication signals offer attractive possibilities for environmental sensing. However, they typically have limited bandwidth and are distributed across several separate frequency bands, which makes high-resolution radar imaging difficult. In this work, we investigate Frequency-Hopping Synthetic Aperture Radar (SAR) as a means of overcoming this limitation. Using vehicle-based measurements, we demonstrate that sub-bands from 4G, 5G and Wi-Fi can be combined to achieve reliable SAR imaging and target detection with an effective total bandwidth of approximately 100 MHz. The results demonstrate that distributed frequency bands can be effectively combined to achieve reliable SAR imaging.

Paper: Sub-6GHz SAR Imaging With Frequency Hopping Toward JCAS Applications in Automotive Scenarios

We are delighted to be taking part in the German Microwave Conference (GEMIC2026) in Karlsruhe next week. Our presentations will take place in the sessions Additive Manufacturing for RF Systems (Tuesday at 10:30 am), Amplifiers (Tuesday at 2:10 pm), Focus Session 05 – UAV Radar Instruments (Tuesday at 3:20 pm) and Radar Imaging and Localisation (Wednesday at 10:40 am).

Holographic antennas offer the decisive advantage that the aperture dimension is decoupled from both the number of feed points and the width of the main lobe, which represents a significant degree of freedom for next-generation automotive radar systems. In this paper, we present a novel multi-layer PCB integration concept for connecting a holographic multi-port Tx and Rx antenna based on glass technology to a MIMO radar demonstrator. In addition to a significant improvement in the range spectrum compared to a reference antenna array, both static and dynamic measurement scenarios, including moving pedestrians, demonstrate precise angular resolution, a clear Doppler spectrogram and robust target detection performance.

Paper: Multi-Feed Holographic-Based Leaky Wave Antennas for MIMO Radar Applications

We are proud to announce that David Werbunat was awarded the Ulm University Society’s Dissertation Prize at the Dies Academicus 2026. The prize recognises his outstanding doctoral thesis “Coherent Networks of Uncoupled Digital Radars”, which makes a significant contribution to cutting-edge research in the field of radar.

Thesis: Coherent Networks of Uncoupled Digital Radars

We are proud to announce that three outstanding theses from our institute have been honoured with the Argus Science Award 2025.
1st place – Bachelor’s thesis: Oliver Gentner – “Phase noise in uncoupled OFDM radar networks”.
1st place – Master’s thesis: Daniel Laqua – “Drone-assisted detection and differentiation of crops using 77 GHz radars”.
2nd place – Master’s thesis: Lukas Paulus – “Signal processing-based synchronisation of uncoupled digital radars”.
We congratulate all the winners on their outstanding achievements.

Imaging with optical radar sensors promises potentially higher resolution due to the short wavelength compared to conventional radar sensors. This article presents a novel, coherent optical sensor operating at a wavelength of 1550 nm, which enables high-resolution Synthetic Aperture Radar (SAR) imaging. By applying a multi-stage phase correction algorithm, phase errors in the system can be corrected, thereby enabling coherent radar measurements over a long period of time. This allows for a significant increase in the signal-to-noise ratio (SNR) through integration into static and dynamic measurement scenarios. Both the coherence over an extended period and the SAR imaging are verified by measurements.

Paper: Coherent Synthetic Aperture Radar (SAR) Imaging with a 1550 nm Optical Sensor

Congratulations to Nicolai Kern on winning the 2025 IEEE Sensors Letters Best Paper Award for his paper "Virtually Augmented Radar Measurements With Hardware Radar Target Simulators for Machine Learning Applications".

Julian successfully defended his doctoral thesis on the topic "System Concepts for Multistatic UAV-Borne Synthetic Aperture Radar" on 22 September 2025. Congratulations on passing your doctoral examination!

Biomimetic antenna arrays (BMAAs) can increase phase sensitivity through the targeted coupling of antenna signals. This paper is the first to analyse how this biomimetic coupling affects angle estimation accuracy, target separation capability and the radiation pattern. Analogue BMAAs demonstrate particular advantages over conventional antenna systems in terms of target separation capability and the avoidance of ambiguities in angle estimation. The easily implementable digital emulation of biomimetic coupling in post-processing allows, depending on the array configuration, an improvement in angle estimation accuracy without significant implementation effort or loss of radar system range. Published in IEEE Transactions on Antennas and Propagation.

Paper: Sensing Capabilities of Analog and Digital Biomimetic Antenna Arrays: Advantages and Limitations

Next week we will be attending the International Conference on Electromagnetics in Advanced Applications (ICEAA) in Palermo. Our presentations will take place in the special sessions ‘mmWave Sensors and Devices’ (Thursday at 9.40 am) and ‘Dielectric waveguides and polymer microwave fibre technology’ (Thursday at 11.00 am, 11.20 am and 2.40 pm).

As part of the conference programme, we are organising a workshop on ‘Automotive Radar Research Trends’, bringing together experts to discuss the future of radar technology in mobility and beyond. During this workshop, Julian Aguilar will give a presentation on ‘Synchronisation Concepts for Automotive Radar Networks’. We look forward to insightful discussions and an inspiring scientific exchange!

On 21 August 2025, Timo successfully defended his doctoral thesis on the topic of "Grid-map, SAR and SLAM approaches for incoherent networked radar sensors for high-resolution imaging". We congratulate him on passing his doctoral examination!

Distributed radar sensors across multiple UAVs enable new applications and improved imaging. But how are the individual sensors synchronised so that the synthetic aperture radar (SAR) principle can still be utilised? In our article, we present a concept in which synchronisation is achieved through signal processing, thereby enabling lossless imaging. Published in IEEE Transactions on Radar Systems, available as an early-access article.

Paper: Coherent Multistatic UAV-Based SAR

Next week we will be attending the International Geoscience and Remote Sensing Symposium (IGARSS) in Brisbane. There we will be chairing session TH1.P2: Advancing UAV and Airborne Remote Sensing I (Thursday from 8:00 am), in which we will also be presenting a paper.

After around three years of intensive work – structuring, writing, revising – our book Millimeter Wave Radar has been published! We are delighted that the English-language edition is now available as an eBook from Springer Verlag. Download eBook
The printed version will follow in a few weeks. A big thank you to everyone involved – and, of course, we hope all interested readers enjoy reading it and find it inspiring!
Christian Waldschmidt, Christina Bonfert, Timo Grebner

On 8 July 2025, Alex successfully defended his doctoral thesis on the topic of "UAV-Borne Synthetic Aperture Radar Imaging of Surface and Subsurface Objects". Congratulations on passing your doctoral examination!

We are delighted to be attending the 6G Conference at the Berlin Congress Centre this week. The annual networking event organised by 6G Platform Germany will take place here from 1 to 3 July. As part of the 6G-ICAS4Mobility project, we will have a stand near the entrance and will be presenting a poster entitled ‘Towards Grid Mapping with ICAS Systems in Automotive Scenarios’.

In this article, Alexander Grathwohl presents a new method for UAV-based synthetic aperture radar (SAR) imaging for arbitrary non-linear trajectories. This method is characterised by an extension of the backprojection algorithm using a weighting factor that depends on the geometry and the properties of the ground surface. The method is demonstrated for targets placed on a grassy area and observed from a highly non-linear trajectory. Published in the Journal of Microwaves, available as an early-access article.

Paper: UAV-Based SAR Imaging of Objects From Arbitrary Trajectories Using Weighted Backprojection

Christian Gesell has received the VDI Prize for his Master’s thesis entitled ‘Coherent bistatic radar imaging with uncoupled digital radars’. Congratulations!

We congratulate Julius Hense on winning the VDE Prize for his bachelor’s thesis entitled ‘Investigation of the dynamic behaviour of antenna patterns during active swivelling using liquid crystals’.

How can the tensor of an anisotropic surface be extracted more efficiently to improve the performance of holographic antennas? In our latest work, we present a novel method for the efficient and precise extraction of anisotropic impedance tensors for arbitrarily shaped unit cells and pixel geometries. The eigenvectors of the purely isotropic tensor are modified using the rotation matrix to obtain the anisotropic impedance tensor. This approach enables highly efficient characterisation of metasurfaces and, consequently, the realisation of high-performance holographic antennas.

Paper: High Efficient Impedance Tensor Extraction Method for Arbitrarily Shaped Metasurface Elements

On 12 May 2025, Vinzenz successfully defended his doctoral thesis on the topic of "Coherent Automotive Radar Networks". Congratulations on passing your doctoral examination!

In our latest work, we present a thorough analysis of the achievable separability, detection capability and height estimation performance of 113 different array configurations. These are subsets of the latest version of our widely known and frequently cited high-performance 4D imaging radar with 1728 virtual channels. We can thus demonstrate that a paradigm shift is required in the optimisation of antenna arrays for automotive systems, as simply increasing aperture size does not lead to the best performance. Instead, we can demonstrate that a low side-lobe level is also of great importance for the detection of objects with small radar cross-sections (e.g. pedestrians) in the vicinity of stronger objects (e.g. cars). For example, in an array with 500 virtual channels, a signal-to-background ratio of 5 dB can be achieved for the detection of a pedestrian if the aperture is reduced to 1/3 and, consequently, the fill factor is increased from 40% to 100% (i.e. a URA).

Paper: Influence of Channel Count and Array Sparsity on the Detection Performance of 4D Imaging Radars

How can scan blindness in planar array antennas be minimised? In our latest paper, we present a novel antenna concept featuring an electronically controllable coupling network based on varactor diodes. This enables adaptive control between adjacent unit cells, thereby allowing for targeted improvements in radiation efficiency.

Paper: A Millimetre-Wave Antenna Array With Tunable Element Coupling for Enhanced Scan Capabilities

Next week marks the start of the lecture period for the 2025 summer semester. A brief overview of the Bachelor’s and Master’s modules offered by the MWT can be found at www.uni-ulm.de/in/mwt/lehre. For the first time, the MWT is offering the lecture ‘Biomedical High-Frequency Technology’ with a project component.

We are delighted to be attending the European Conference on Antennas and Propagation (EuCAP2025) in Stockholm this week. On Friday, 4 April, we will be giving a presentation on ‘A Tensor-Based Holographic Multi-Feed Antenna Synthesis for MIMO Radar Applications’.

Congratulations to Julian Aguilar on winning the Best Paper Award at GeMiC 2025 in Dresden for his paper “Radon-Fourier Transform for Timing Correction in Uncoupled Digital Radar Networks”.

This week we will be attending the German Microwave Conference (GeMiC) in Dresden. The presentations will take place on Monday at 14:10 in Radar Session 1, on Tuesday at 17:30 in Radar Session 2 and on Wednesday at 11:10 in Poster Session 2.

In this work, the authors pursue the idea of creating a low-loss phase shifter by using p-i-n diodes to tune the electrical response and liquid crystals to tune the magnetic response of a stacked multi-material unit cell. They demonstrate the concept at 10 GHz using a single element integrated into a waveguide enclosure to directly characterise the phase tuning. In the current configuration, the response time is extremely slow, but this is expected to improve at higher frequencies.

Paper: Hybrid fishnet metamaterial based on liquid crystals and P-I-N diodes for reconfigurable transmit arrays at 10 GHz

Prof. Christian Waldschmidt is a new member of the German Academy of Science and Engineering (acatech). He was elected at the last general meeting, along with 24 other researchers.

Article: Ulm radar researcher is new acatech member