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Item type:Publication, Access status: with files , A novel differential incoherent heterodyne continuous-wave radar receiver architecture with increased phase sensitivity(IEEE, 2026-02); ; ; ; This work presents a novel heterodyne radar transceiver architecture based on two separate, incoherent radio frequency (RF) sources. Unlike conventional continuous-wave (CW) radar systems, the proposed approach measures the square of the channel transfer function, resulting in doubled phase sensitivity. This enhancement arises from a di erential evaluation of the downconverted intermediate-frequency (IF) signals, which enables precise tracking of phase changes without requiring phase-locked local oscillators. The associated signal-processing and calibration methods are derived, allowing for accurate reconstruction of the dynamic target response, even in the presence of static reflections and without needing knowledge of the calibration target’s absolute position. Additionally, the e ect of oscillator phase noise is evaluated. Experimental validation using high-precision linear motion confirms that the system accurately tracks target displacement and delivers results comparable to those obtained with a commercial vector network analyzer (VNA). By eliminating the need for RF phase synchronization between transceivers, the architecture significantly reduces hardware complexity and is well-suited for integration and miniaturization. Although demonstrated with a single transceiver pair, the method scales naturally to multichannel configurations, enabling low-complexity multiple-input–multiple-output (MIMO) radar systems with enhanced sensitivity.Publicationtype: Journal Article49 39 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Calibration of the self-radar-cross-section of continuous-wave radarsThis article presents a calibration method to eliminate measurement errors introduced by the own radar cross section (self-RCS) of continuous-wave (CW) radar systems, which focus on the measurement of relative target motions. By measuring the radar response of an unknown target located at known positions, the proposed procedure retrieves the calibration constants. They allow for eliminating the systematic errors associated with the multiple reflections between the radar device and the target, an effect initiated by the self-RCS. This improves the linearity of the overall transfer function, which enhances measurement accuracy and mitigates nonlinear distortion effects for vibration-sensing applications. The calibration approach is successfully validated by measurements in different conditions. In contrast to conventional techniques that implicitly neglect the self-RCS, the proposed technique achieves a superior and robust accuracy reaching one-thousandth of the operating wavelength.Publicationtype: Journal Article73 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Accuracy limitations of interferometric radar owing to the radar cross section of its antennaThis article analyzes the influence of the intrinsic radar cross section (RCS) of interferometric radar systems on their accuracy. The latter is generally considered to be limited by the electrical imperfections and nonlinearities of the radar front-end. However, it will be derived that even if the front-end is ideal and linear, continuous-wave (CW) radars are inherently nonlinear systems. The cause is multiple reflections between the target and the radar antenna, which itself exhibits a nonzero RCS. Although significantly smaller, the secondary reflections superimpose to the primary one, thereby introducing amplitude and phase deviations, which are then erroneously attributed to target displacement. The established model as well as the derived error estimates are verified by measurements with a vector network analyzer and targets with different RCSs.Publicationtype: Journal Article108 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A hybrid-integrated K-/ Ka-band phased array module with dual-polarized shared apertureIn this work, a passive dual-polarized shared antenna aperture and active beamformer front-ends are integrated into a phased array module. The system operates in the K-/ Ka-band and is intended for satellite communications. It consists of a hybrid assembly of aluminum waveguide components and printed circuit boards that are electrically connected by anisotropic conductive adhesive, containing a heterodyne transceiver with L -band interfaces. For proof of concept, a demonstrator with 64 transmit (Tx) and 32 receive (Rx) elements is fabricated and characterized. It provides full-duplex Tx/Rx operation with bandwidths of 1 GHz centered around 29.5 (Tx) and 19.5 GHz (Rx), beam scanning over wide angular ranges up to 60 ∘ in both H -and E -planes, an equivalent isotropic radiated power of up to 20.4 dBW at 1-dB power compression and an Rx gain to noise temperature ratio of up to − 10.2 dB/K at room temperature. The measured performances are comparable to those of phased array systems with separate apertures and thus validate the integration approach.Publicationtype: Journal Article90 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A Transmission Line Approach for Rough Conductor Surface Impedance Analysis(2023-02-01); ; ; This work proposes a transmission line approach to determine the surface impedance of conductors with rough surfaces. Based on the gradient model, the roughness is represented by a gradual transition of the intrinsic impedance. Discretization and successive impedance transformations then directly yield the surface impedance. Evaluating the fields is not necessary to this end, but still feasible if required. Investigations of the proposed model confirm the field diffusion to be fully characterized by a single dimensionless ratio, which enables a comprehensive analysis of the surface impedance regarding its dependency on frequency, conductivity, and roughness.Publicationtype: Journal Article76 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Construction of Reciprocal Macromodels in the Loewner Matrix FrameworkMany of the passive interconnect systems that arise in applications for analysis of power and signal integrity (PI/SI) are reciprocal by nature, and the transfer matrices of such systems are characterized by symmetry constraints. Therefore, it is natural to think in using reciprocal macromodels for the representation of reciprocal systems. Reciprocal macromodels do not only represent in a more faithful way the systems in which they are based upon, but given a reciprocal stable macromodel, it is computationally cheaper to find its passivity violations. This work shows how to construct reciprocal descriptor systems macromodels from black box data using the Loewner matrix (LM) framework, and also, it shows that it is possible to enforce stability and passivity in reciprocal stable macromodels, keeping its size and structure. Various examples of printed circuit board-based high-speed links and power delivery networks described by scattering parameters are used to demonstrate the effectiveness of the proposed approach.Publicationtype: Journal Article31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Radar-Based Gesture Recognition Using a Variational Autoencoder With Deep Statistical Metric Learning(2022-11-01); ; ; Radar-based gesture recognition systems are a promising concept for new human–machine interfaces. However, the systems are sensitive to user-dependent gesture patterns, sensor noise characteristics, background environments, and unknown gestures or background motions. To overcome such challenges, we propose a variational autoencoder architecture-based deep metric learning, which is optimized using a novel loss function combining a statistical distance triplet loss and the center loss. By learning the statistical distance between distributions, the proposed solution, compared with triplet loss, is able to better learn the nonlinear characteristics in the data, is less sensitivity to training strategy, and is capable of creating close knit embedding clusters. Moreover, it is experimentally demonstrated that the proposed gesture recognition system using radar spectrograms has improved classification accuracy and random gesture rejection accuracy compared with the state-of-the-art deep metric learning approaches. Furthermore, we proof the real-world capability of the system by implementing a real-time demonstrator, which allows playing “Tetris” with hand gestures.Publicationtype: Journal Article73 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Improving accuracy after stability enforcement in the Loewner matrix framework(IEEE, 2022-02-01); ; ; The Loewner matrix (LM) is a powerful macromodeling technique that uses sampled data in the frequency domain for representing dynamical systems in a descriptor form. As stability cannot be enforced during the construction process, a postprocessing step is required to ensure a stable macromodel, which reduces its accuracy. In this article, two techniques are incorporated and evaluated with the LM framework in this postprocessing phase. The first one is an efficient sign-pole-flipping technique for stability enforcement. The other one is a matrix updating technique applied after the stability enforcement of the model. The proposed approaches are evaluated using data in the scattering parameter form for printed circuit board via interconnects examples and an electromagnetic shielding structure and compared to the state-of-the-art stability enforcement algorithms. For completeness, we will also compare the results with respect to the macromodels created by the vector fitting algorithm. It was found that by the proposed flipping and matrix updating approaches, an error reduction by a factor between 2 and 20 was achieved with respect to the previously reported methods.Publicationtype: Journal Article47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Compact Diplexers With Folded Circular SIW Cavity Filters(2021-01); ; ; This work presents diplexers realized with folded circular substrate integrated waveguide (FCSIW) cavity filters. The properties of such cavities are analyzed, and empirical equations for calculating the resonant frequencies are given. The analysis relies on an even-/odd-mode decomposition. A 10-GHz filter is designed based on this approach. In the second step, its size is reduced, still maintaining the passband behavior. An asymmetric taper is used to connect two such filters to realize a diplexer. Two diplexers with center frequencies of 10/15 and 12/13.5 GHz are presented. The diplexers are several times more compact than comparable devices reported in the literature. The components are manufactured, and the functionality is demonstrated by simulation and measurements.Publicationtype: Journal Article204 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , An SIW-Based GaN Power Amplifier Module in LTCC(2020-12); This article reports a solid-state power amplifier module in low-temperature cofired ceramic (LTCC) technology. For compactness and low loss, the package utilizes substrate-integrated waveguides (SIWs). To meet the thermal requirements, the amplifiers are mounted on a metallic plate that is integrated into the LTCC multilayer and transfers the heat to a spreader. Both RF and thermal measurement results for a package with two integrated 10-W gallium nitride (GaN) power amplifiers at the K-band are presented. They demonstrate the suitability of the module for highly integrated transmitters as needed for phased arrays or multiple-feed-per-beam satellite antennas.Publicationtype: Journal Article109