Papers by Jacques Sombrin
We address the problem of partitioning a network of nano-satellites to distribute fairly the netw... more We address the problem of partitioning a network of nano-satellites to distribute fairly the network load under energy consumption constraints. The study takes place in a context where this swarm of nano-satellites orbits the Moon and works as, but not limited to, a distributed radio-telescope for low-frequency radio interferometry. During an interferometry mission, each nano-satellite collects observation data, then shares them with the other swarm members to compute a global image of space. However, the simultaneous transmission of large volumes of data can cause communication issues by overloading the radio channel, leading to potential packet loss. In this context, we investigate three division algorithms based on graph sampling techniques. We prove that random walk-based algorithms overall perform the best in terms of conservation of graph properties and fairness for group sizes down to 10% of the original graph.
International Journal of Microwave and Wireless Technologies, Feb 1, 2011
We investigate a set of methods aimed at enhancing the resilience and robustness of a mobile comm... more We investigate a set of methods aimed at enhancing the resilience and robustness of a mobile communication network, with a focus on a case involving a nanosatellite swarm network. The proposed method focuses on graph division techniques, aiming to recover from impairments while preserving the primary function or mission of the mobile network. By examining the effects of exploration and random selection algorithms on network robustness and resilience, our findings indicate that fair graph division consistently strengthens system robustness by reducing the number of packets to transmit, regardless of the algorithm employed. Additionally, our analysis highlights the superior performance of exploration algorithms, such as MIRW, in enhancing robustness and resilience.
2022 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS)
2022 IEEE Radio and Wireless Symposium (RWS), 2022
In this paper, we introduce correlation technologies both at RF/mmWave and Base-Band frequencies.... more In this paper, we introduce correlation technologies both at RF/mmWave and Base-Band frequencies. At RF and mmWave frequencies power-spectra and energy-spectra metrics are introduced for measuring the power-density of mobile devices and systems. The use of unified power-spectra and energy-spectra metrics leads to innovative Electromagnetic-Thermal sensing solutions for OTA-Testing. At Base-Band frequencies, DSP-based Convolutional-Accelerators are proposed for fast and accurate measurement of EVM (Error Vector Magnitude) using correlation technologies. New ASIC-embedded Smart-Connectors are developed for bringing correlation-based signal processing close to antenna-in-package (AiP) modules. Porting of the DSP-based Convolutional-Accelerators into advanced FD-SOI-ASIC platforms for co-integration with adaptive RF/mmWave FrontEnd-Modules will enable real-time extraction of auto-correlation and cross-correlation functions of stochastic signals for mobile devices and systems. Perspectives toward optically synchronized interferometric-correlation technologies are drawn for accurate measurements of stochastic EM fields in noisy environments.
2021 51st European Microwave Conference (EuMC)
2015 Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC), 2015
This paper deals with the modeling of a Traveling-Wave Tube (TWT) amplifier. The continuous-time ... more This paper deals with the modeling of a Traveling-Wave Tube (TWT) amplifier. The continuous-time modeling approach is presented and the model is used to capture the carrier memory effect of the TWT amplifier. Some processing on measurements are described and an assessment of the model under 2-tone signals is achieved for validation.
2016 88th ARFTG Microwave Measurement Conference (ARFTG), 2016
An Unequally Spaced Multi-Tone signal (USMT) is used for the assessment of nonlinear devices and ... more An Unequally Spaced Multi-Tone signal (USMT) is used for the assessment of nonlinear devices and circuits. The statistical properties of the signal are described. The setup measurements for such a signal are given either by using a Large Signal Network Analyzer (LSNA) or a Nonlinear Vector Network Analyzer (Keysight PNA NVNA with SA option). A USMT Load Pull (USMT-LP)set-up has been developed using a LSNA and it is shown how to extend this set-up to a NVNA receiver. The set-up is fully on-wafer calibrated at all the frequencies of interest. The USMT-LP set-up is configured to make measurements with USMT signals up to eight frequencies and allows measuring simultaneously the MT output power, gain, Power Added Efficiency (PAE), Carrier to Intermodulation (C/I) ratio or Noise Power Ratio (NPR) in order to derive the Error Vector Magnitude (EVM) induced by the device.
2016 11th European Microwave Integrated Circuits Conference (EuMIC), 2016
An innovative on-wafer multi-tone load-pull (MTLP) bench is presented in this paper. It has been ... more An innovative on-wafer multi-tone load-pull (MTLP) bench is presented in this paper. It has been used to assess the linearity performances of different GaN HEMT transistors from two international foundries according to both single- and multi-carrier figures of merit. Time-domain characteristics studies suggest complementary distortion analysis. The transistors are operated at C-band in deep Class-AB. That bias appropriately copes with efficiency and linearity dilemma. The bench currently supports successful telecommunication and radar qualifications.
Acta Astronautica, 2000
ABSTRACT The RADAR SAIL concept is based on the use of a rectangular antenna lying in the dawn–du... more ABSTRACT The RADAR SAIL concept is based on the use of a rectangular antenna lying in the dawn–dusk orbital plane with the length (along speed vector) smaller than the height. Such geometry makes it possible to place the solar cells on the back of the antenna, to use gravity gradient stabilisation, and (optionally) to implement multipath-free GPS interferometric measurement of the antenna deformation thus allowing structural relaxation. Less obviously, the geometry favours the RADAR design too, by allowing grating lobes and therefore a lower density of built-in electronic in the active antenna. The antenna can be thin and packed for launch inside a cylinder-shaped bus having pyrotechnic doors for the antenna deployment and bearing the rest of the payload and the service equipment. With respect to a standard design of high performance missions, cost savings come from the bus, whose functions (AOCS, power supply) are simplified, from the launch since the mass budget and the stowing configuration become compatible with medium size rockets (LLV2/3, DELTA-LITE, LM-4…), and from the active antenna built-in electronics. Moreover, long satellite life-time can be achieved (10 years instead of 5).The RADAR SAIL concept is all the more cost effective when the mission requires a large, high and short antenna, i.e. high resolution (
We present a method to derive a rational model from scattering data for electrical parameter extr... more We present a method to derive a rational model from scattering data for electrical parameter extraction. Unlike other methods, the stability and the MacMillan degree of the rational approximation are guaranteed. In order to improve the usability of our method in computer-aided tuning , we also present an algorithm performing automatic reference plane adjustment. Results obtained on a 10 order dual mode IMUX filter are presented.
This paper presents a set-up which enables the generation and the calibrated time domain measurem... more This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power – 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects.
A low-orbiting radar observation or telecommunication satellite comprising an element with one or... more A low-orbiting radar observation or telecommunication satellite comprising an element with one or more antennas lying in a plane passing through the centre of the Earth, e.g. the orbital plane. The antennas operate on one or both sides of the element (11). The height of the antenna element (11) is greater than its dimension in the forward direction of the satellite, such that said satellite is naturally stabilised by a gravity gradient. The cells of the solar generator (13) are supported on the surface of the antenna element (11) that continuously faces the sun in the case of a sun-synchronous orbit at a local time of 0600 hours/1800 hours. The antenna element (11) consists of a plurality of pivotable panels (14) over which means are distributed for affecting the phase of the received or transmitted wave, and comprises a plurality of GPS sensors (15) distributed over said panels (14) to enable phase shifters to measure then compensate for the deflection of said element. At the time ...
This paper describes a Volterra-based model of frequency dependent AM-AM and AM-PM conversions of... more This paper describes a Volterra-based model of frequency dependent AM-AM and AM-PM conversions of a nonlinear traveling wave tube amplifier (TWTA) for use in communication system level simulation. The proposed method provides a systematic way to identify the model and ensures numerical stability in coefficient extraction. Comparison between simulation results and measurements are presented in terms of gain and noise power ratio (NPR).
The CNES (French Space Agency) has studied memoryless predistortion techniques for power amplifie... more The CNES (French Space Agency) has studied memoryless predistortion techniques for power amplifier nonlinearity of satellite payload telemetry. These techniques are applied to high order modulations taken from the DVB-S2 standard and the associated CCSDS blue book. An easy-toimplement calibration method was also developed. The predistortion was implemented at two times the symbol rate after Square Root Raised Cosine shaping on a breadboard model of a 16APSK modulator associated to a Solid State Power Amplifier. It allows to reduce the amplifier back-off and thus to increase the power added efficiency for an equivalent signal quality.
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Papers by Jacques Sombrin