Saab (Sweden)

We evaluate Forward Error Correction (FEC) codes in the context of a novel routing protocol HDARP+ for airborne networks. HDARP+ uses directional antennas and dynamic FEC coding to avoid detection by adversaries. The use of FEC coding is dynamic in the sense that different FEC codes, or no FEC code, will be used depending on the relative position of friendly and adversary aircraft. Due to the real-time restrictions in airborne networks, encoding and decoding must be fast and done through table lookup. Since we use table lookup, the FEC codes must be short. We evaluate two types of short FEC codes: Reed-Solomon (RS) codes, and FEC codes found using greedy search (called GS codes). The results show that the RS codes are better than the GS codes at handling error bursts. However, the GS codes are more flexible when it comes to finding attractive trade-offs between the code's ability to increase the number of the cases when hostile detection can be avoided (related to the coding gain), the code rate and the amount of memory required for implementing lookup tables. This paper was originally presented at the NATO Science and Technology Organization Symposium (ICMCIS) organized by the Information Systems Technology (IST) Science and Technology Committee, IST-209-RSY - the ICMCIS, held in Oeiras, Portugal, 13–14 May 2025.

This article proposes a method for improved model verification within Large-Scale Simulators (LSS). The approach relies on machine-interoperable traceability of model verification information, such as model Operational Domains (ODs). This enables automated evaluation of model relevance and facilitates the combination of models for a broader evaluation of credible simulation results. The paper introduces a proof-of-concept testbed for verification of black-box models against model requirements. Furthermore, the results also include a proposal for a machine-readable format to capture model requirement Verification & Validation (V&V) results, along with the resulting model and updated model OD information.

The dynamic thermal coupling within gallium nitride (GaN) high electron mobility transistors (HEMTs) is characterized and modeled in a finite element method (FEM) solver to determine the thermal impedance of the HEMT. The study presents a method for calibrating the FEM model based on transient measurements with integrated temperature sensors placed 7.5, 91.5, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$175.5~\mu $ </tex-math></inline-formula> m away from a heat source. A sensitivity analysis is presented to show that the influence of the epitaxial layers, substrate, and die-attach layer can be differentiated. The method is used to calibrate a model that accurately replicates the measured thermal coupling. The model is assessed for different baseplate temperatures and a time-varying signal. Finally, an example is presented to show how thermal coupling changes the thermal impedance of GaN HEMTs and how the results can be used for layout optimization. The presented model and calibration method can also be used to evaluate how the device’s packaging influences its thermal impedance.

The dynamic thermal coupling in integrated GaN power amplifiers is studied based on transient measurements on an amplifier structure with integrated temperature sensors. The results show that the thermal coupling from a transistor can modulate neighboring transistors with a low pass filtered response. Here, the cut-off frequency and amplitude of the modulation effect are reduced with separation while the phase shift increases. When applied to a large power amplifier, it is shown that the temperature gradient over the amplifier will vary dynamically, where five distinct time regions are identified. A numerical model is presented to validate the measurements. The results can be used to improve the accuracy of electro-thermal models of GaN power amplifiers.

A novel approach to on-chip temperature sensors for non-invasive thermal characterization and monitoring of packaged GaN MMICs is presented. The proposed sensor is fully compatible with commercial GaN foundry processes and enables improved reliability estimation of highly integrated systems. A dedicated test structure is developed to demonstrate the capabilities of the sensor, and an accurate calibration method of its temperature response is proposed. This combination allows for continuous temperature monitoring during operation with electrical acquisition of temperature transients. The method also enables the thermal characterization of the device and package.

Here we present a novel routing protocol HDARP+ for airborne tactical networks that use directional antennas. HDARP+ extends the existing protocol HDARP (Hostile-Direction Aware Routing Protocol) by reducing the risk for detection by adversary aircraft even further. Compared to HDARP, the extension in HDARP+ introduces dynamic Forward Error Correction (FEC) coding. The FEC code is dynamic in the sense that different FEC codes, or no FEC code, will be used depending on the relative position of the receiver and adversary aircraft. We evaluate three different Reed-Solomon FEC codes based on three criteria: the ability to transmit in the presence of adversaries without being detected, the reduction of the effective communication bandwidth, and the implementation cost in terms of the sizes of lookup tables for encoding and decoding. We argue that (variations of) HDARP+ will be implemented in future airborne tactical networks. This paper was originally presented at the NATO Science and Technology Organization Symposium (ICMCIS) organized by the Information Systems Technology (IST) Panel, IST-205-RSY - the ICMCIS, held in Koblenz, Germany, 23–24 April 2024.

In this study, we present spectral enclosures and accumulation of eigenvalues of a class of operator functions with several unbounded operator coefficients. Our findings have direct relevance to the third-order Moore-Gibson-Thompson equation with memory and additional damping. The new results include sufficient conditions for the accumulation of branches of eigenvalues to the essential spectrum and new spectral enclosures for operator functions with several unbounded operator coefficients. To illustrate the analytical results, we apply the abstract findings to concrete equations of the Moore-Gibson-Thompson type. Additionally, we employ numerical computations to further elucidate the analytical results.

The optimal antenna array excitation vector is derived that maximizes the (realized) array gain in a particular direction while preventing the coupled input power to the low-noise amplifiers on the receive side to exceed a certain maximum threshold level. This is very useful for in-band full-duplex systems where the hardware complexity for self-interference cancellation must be minimized. In this approach, the perfect nulling of interference on the RX side is not required, sparing degrees of freedom for the TX beamformer. We evaluate the performance of the proposed TX beamforming algorithm by showing numerical results of the 25 x-polarized TX and 25 RX with 0.5$\lambda$ element spacing and $\lambda$ gap distance between the TX and RX sub-array.

One of the major challenges in communication, radar, and electronic warfare receivers arises from nearby device interference. This article presents a 2–6-GHz gallium-nitride (GaN) low-noise amplifier (LNA) front end with onboard sensing, processing, and feedback utilizing microcontroller-based controls to achieve adaptation to a variety of interference scenarios through power and linearity regulations. The utilization of GaN LNA provides high-power handling capability (30 dBm) and high linearity (OIP3 = 30 dBm) for radar and EW applications. The system permits an LNA power consumption to tune from 500 mW to 2 W ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> increase) in order to adjust the linearity from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {1 dB,IN}}=-10.5$ </tex-math></inline-formula> to 0.5 dBm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times $ </tex-math></inline-formula> increase). Across the tuning range, the noise figure increases by approximately 0.4 dB. Feedback control methods are presented with backgrounds from control theory. The rest of the controls consume <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\leq 10\%$ </tex-math></inline-formula> (100 mW) of nominal LNA power (1 W) to achieve an adaptation time < 1 ms.

Variational quantum algorithms (VQAs) represent a promising approach to utilizing current quantum computing infrastructures. VQAs are based on a parameterized quantum circuit optimized in a closed loop via a classical algorithm. This hybrid approach reduces the quantum processing unit load but comes at the cost of a classical optimization that can feature a flat energy landscape. Existing optimization techniques, including either imaginary time-propagation, natural gradient, or momentum-based approaches, are promising candidates but place either a significant burden on the quantum device or suffer frequently from slow convergence. In this work, we propose the quantum Broyden adaptive natural gradient (qBang) approach, a novel optimizer that aims to distill the best aspects of existing approaches. By employing the Broyden approach to approximate updates in the Fisher information matrix and combining it with a momentum-based algorithm, qBang reduces quantum-resource requirements while performing better than more resource-demanding alternatives. Benchmarks for the barren plateau, quantum chemistry, and the max-cut problem demonstrate an overall stable performance with a clear improvement over existing techniques in the case of flat (but not exponentially flat) optimization landscapes. qBang introduces a new development strategy for gradient-based VQAs with a plethora of possible improvements.