Compact, high performant prepare-and-measure photon source based on indistinguishable VCSELs. - In: Quantum Computing, Communication, and Simulation IV, (2024), 129110W, S. 129110W-1-129110W-10
We present an ultra-compact, hybrid faint pulse source (FPS) at 850 nm, making use of a linear eight VCSELs array at spectral (<1 pm wavelength difference, and >90% overlap at FWHM) and temporal (<1 ps) indistinguishability, as well as polarization quality in the four H/V/D/A BB84 channels >20 dB. A common VCSEL array on a single substrate is used, at a pitch of 250 μm and with integrated polarizers, having a spectral indistinguishability if the substrate is temperature levelled < 0.5 K. Each VCSEL represents either faint or full amplitude signal for the H/V/D/A channels of the BB84 protocol. The temperature levelling heatsink is made of Molybdenium, integrated on LTCC board to host the emitter substrate and its respective DAC driving circuit at speeds up to 10 GHz. VCSEL integrated micro-lenses and two additional micro-lens arrays fully collimate the beams and refocus them into a waveguide combiner chip which realizes the polarization independent coupling of all eight VCSEL free-space beams with a pulse delay variation <0.2 ps.
https://doi.org/10.1117/12.2691176
Impact of antenna position and radiation patterns on target detection in a highway environment utilizing ICAS extended model. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), S. 140-147
In this paper, we explore the impact of different antenna positions and radiation patterns on the channel per-formance of an Integrated Communication and Sensing (ICAS) extended model in a highway environment. We have considered a 3-dB omnidirectional Transmitter (Tx) and a directive Receiver (Rx) for our analysis. The antenna radiation patterns of patch and horn antennas are used for the directive receiver. In our system, we have considered three different setups. In the first setup, Rx has a directive antenna (either horn or patch) installed on the car's front bumper. In the second setup, the directive antenna is installed on the car's back bumper. For the third setup, the radiation patterns for the front and back bumper of the car are combined, thus giving rise to Combined Gain Pattern (CGP). The channel responses for the front and back bumper-placed antenna setups are evaluated and compared with the respective CGP setup channel response. The performance of an I CAS system depends on the successful detection of targets. We have considered two types of scatterers in our system. The moving vehicles on the road represent Dynamic Targets (DT) whereas, stationary point reflection sources along the sides of the highway represent Diffuse (DI) scattering components. We have shown in our results that the CGP setup outperforms the front and back bumper-located antenna setups in terms of channel magnitude and accurate target detection capabilities. Moreover, CGP setup helps in modeling the environment better as compared to front and back-bumper installed setups. The horn antenna setup results in superior performance in contrast to the patch antenna setup due to its high directivity.
https://doi.org/10.1109/VNC61989.2024.10576005
Coupled block-term tensor decomposition for near-field localization in multi-static MIMO radar systems. - In: 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, (2024), S. 13331-13335
This paper presents a high-resolution coupled rank-(L r ,L r ,1) block-term decomposition-based near-field localization scheme for multi-static MIMO radar systems. The proposed COBRAS (COupled Block-term decomposition for multi-static RAdar Systems) algorithm uses the exact wavefront model to estimate the target location parameters in 3D space and can be applied to arbitrary array geometries. Compared to the far-field models, the exact near-field wavefront model allows exploiting the distance information for high-accuracy positioning. Moreover, we consider a system with massive antenna arrays, which increases the Fresnel region and expands the range of the near-field assumption. The COBRAS algorithm includes the initial tensor decomposition of the data and further post-processing steps that allow extracting the location parameters. Additionally, we compare the performance of different rank-(L r ,L r ,1) block-term decomposition algorithms and demonstrate how the employment of coupling improves the localization performance compared to the non-coupled solutions.
https://doi.org/10.1109/ICASSP48485.2024.10445930
Jointly learning selection matrices for transmitters, receivers and Fourier coefficients in multichannel imaging. - In: 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, (2024), S. 8691-8695
Strategic subsampling has become a focal point due to its effectiveness in compressing data, particularly in the Full Matrix Capture (FMC) approach in ultrasonic imaging. This paper introduces the Joint Deep Probabilistic Subsampling (J-DPS) method, which aims to learn optimal selection matrices simultaneously for transmitters, receivers, and Fourier coefficients. This task-based algorithm is realized by introducing a specialized measurement model and integrating a customized Complex Learned FISTA (CL-FISTA) network. We propose a parallel network architecture, partitioned into three segments corresponding to the three matrices, all working toward a shared optimization objective with adjustable loss allocation. A synthetic dataset is designed to reflect practical scenarios, and we provide quantitative comparisons with a traditional CRB-based algorithm, standard DPS, and J-DPS.
https://doi.org/10.1109/ICASSP48485.2024.10448087
Robust near-field beamforming for millimeter wave communication system with aperture perturbations. - In: 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, (2024), S. 8726-8730
In this paper, we develop a near-field beamforming algorithm that is robust against aperture deformations. We derive analytical expressions on the bounds of the elements of the steering vector as a function of the known bounds of the coordinate displacement. We apply these bounds during the optimization procedure to design beamformers that are robust to aperture perturbations. Simulation results show that the proposed robust near-field beamforming algorithm outperforms the available benchmark in the literature.
https://doi.org/10.1109/ICASSP48485.2024.10447507
Modelling micro-Doppler signature of drone propellers in distributed ISAC. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), insges. 6 S.
Integrated Sensing and Communication (ISAC) comprises detection and analysis of non-cooperative targets by exploiting the resources of the mobile radio system. In this context, micro-Doppler is of great importance for target classification, in order to distinguish objects with local movements. For developing algorithms for target classification, it is necessary to have a large amount of target signatures. Aiming to generate these data, this paper proposes a mathematical model for the micro-Doppler of drone rotating propellers, and validate the proposed model by comparing it to measured micro-Doppler. Results show that the proposed mathematical model can generate micro-Doppler data very similar to those from measurement data.
https://doi.org/10.1109/RadarConf2458775.2024.10548468
Gridless parameter estimation in partly calibrated rectangular arrays. - In: 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, (2024), S. 8796-8800
Spatial frequency estimation from a mixture of noisy sinusoids finds applications in various fields. The widely used subspace-based methods provide super-resolution parameter estimation at a low computational cost. However, they require an accurate array calibration, which is difficult for large antenna arrays. Sparsity-based methods have been shown to be more robust than subspace-based methods in difficult scenarios, e.g., in the case with a small number of snapshots and/or correlated sources. In this paper, we consider the direction-of-arrival (DOA) estimation in partly calibrated rectangular arrays comprising several calibrated and identical subarrays. We derive a gridless sparse formulation for DOA estimation based on the shift-invariance properties of the array and develop an efficient algorithm in the alternating direction method of multipliers (ADMM) framework. Numerical simulations show the superior error performance of our proposed method compared to subspace-based methods.
https://doi.org/10.1109/ICASSP48485.2024.10446959
Leveraging tensor subspace prior: enhanced sum of nuclear norm minimization for tensor completion. - In: 2024 IEEE International Conference on Acoustics, Speech, and Signal Processing, (2024), S. 7655-7659
Tensor completion has attracted increasing attention in signal processing, computer vision, and biomedical engineering. By using nuclear norm minimization, a tensor completion problem can be converted into a convex program and enjoys properties gained from matrix completion. The low rank property has been widely used for tensor/matrix completion. However, the prior subspace information can also be utilized, which has been ignored and does not exhibit its full power in the existing formulation. In this paper, we propose a new framework leveraging tensor subspace prior for the sum of nuclear norm (SNN) minimization, which supports a range of tensor decompositions. By using the knowledge of the self-prior (SP)/nonself-prior (NSP) and further designing an efficient algorithm based on the Alternating Direction Method of Multipliers (ADMM), the performance of tensor completion can be enhanced. The superiority of the proposed method is verified by extensive numerical experiments.
https://doi.org/10.1109/ICASSP48485.2024.10447654
Improving the spatial correlation characteristics of antenna arrays using linear operators and wide-band modelling. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), S. 67-73
The analysis of wireless communication channels at the mmWave, sub-THz and THz bands gives rise to difficulties in the construction of antenna arrays due to the small maximum inter-element spacing constraints at these frequencies. Arrays with uniform spacing greater than half the wavelength for a certain carrier frequency exhibit aliasing side-lobes in the angular domain, prohibiting non-ambiguous estimates of a propagating wave-front’s angle of arrival.In this paper, we present how wide-band modelling of the array response is useful in mitigating this spatial aliasing effect. This approach aims to reduce the grating lobes by exploiting the angle- and frequency-dependent phase-shifts observed in the response of the array to a planar wave-front travelling across it.Furthermore, we propose a method by which the spatial correlation characteristics of an array operating at 33 GHz carrier frequency with an instantaneous bandwidth of 1 GHz can be improved such that the angular-domain side-lobes are reduced by 5-10 dB. This method, applicable to arbitrary antenna array manifolds, makes use of a linear operator that is applied to the base-band samples of the channel transfer function measured in space and frequency domains. By means of synthetically simulated arrays, we show that when operating with a bandwidth of 1 GHz, the use of a derived linear operator applied to the array output results in the spatial correlation characteristics approaching those of the array operating at a bandwidth of 12 GHz. Hence, non-ambiguous angle estimates can be obtained in the field without the use of expensive high-bandwidth RF front-end components.
https://doi.org/10.1109/WSA61681.2024.10511328
Excitation signal design for THz channel sounding and propagation parameter estimation. - In: 18th European Conference on Antennas and Propagation, (2024), insges. 5 S.
In this publication, we analyze how the performance of propagation parameter estimation for THz channel sounding can be improved by the power spectrum design of a multicarrier waveform. To this end, we discuss the Fisher information of the propagation parameters and the corresponding deterministic Cramèr-Rao lower bound (CRB) as well as their relation to the carrier powers of the excitation signal. We use these quantities to design waveforms that improve range estimation. In practice, evaluating the Fisher information requires prior knowledge of the propagation scenario which is usually unavailable. Hence, we propose two solutions which we compare numerically to the classical approach of equal power distribution. The evaluation shows that an optimized power distribution can improve the CRB comparable up to a 4 dB gain in signal-to-noise ratio (SNR) if knowledge about the propagation scenario is available and slightly less if the scenario is unknown.
https://doi.org/10.23919/EuCAP60739.2024.10501423