A way to increase the bit ratein ionospheric radio links

The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF-band (3-30 MHz). The applications expected in this study are image transmitting and real-time videoconferencing. Very high rates are required compared to the standard modems. Therefore, an array processing is performed with a set of antennas whose spatial response differs from one another arranged in a circular array or in a collocated sensor. Synchronization (Zero Crossing Detector) and source separation (LMS algorithm) resort to classical well-tested techniques involving training sequences. Experimental results are presented for both antenna configurations. These techniques improve data rate, reaching 20 kbits/s within the 6 kHz bandwidth (QAM 64) without coding or interleaving

Mise en oeuvre de la séparation de sources sur un ensemble d'antennes colocalisées : application à l'augmentation du débit numérique en transmission H.F. ( 3-30 MHz)

Cet article décrit un système opérationnel de transmission numérique en gamme H.F. visant à augmenter le débit binaire de façon significative par rapport au standard actuel. Pour cela, un traitement d'antenne est mis en oeuvre sur un ensemble de quatre capteurs colocalisés présentant une diversité de réponses spatiales. Les techniques utilisées tant pour la synchronisation ( Zéro Crossing Detector) que pour la séparation de sources ( algorithme LMS) sont des solutions classiques et éprouvées faisant appel à des séquences d'apprentissage. Les résultats obtenus sont conformes à l'objectif fixé puisque le débit binaire atteint 15 kbits/s dans une bande de 3 kHz

A non-foster circuit design for antenna miniaturization

International audienceIn this paper, a non-Foster circuit for achieving a negative small capacitance based on Linvill floating-type Negative Impedance Convertor (NIC) is realized. The effect of the parasitic elements and the transmission lines on the circuit performance is discussed. The experimental results show that the circuit presents a negative capacitor of 0.87pF in the UHF band. The circuit linearity test reveals a high output 1dB gain compression point at 7.8dBm and an output saturation point at 15.6dBm. Furthermore, the circuit has relatively high inter-modulation Output Intercept Points (OIPs). © 2016 IEICE

Characteristic modes optimisation approach to design a wideband electrically small antenna

International audienceA design methodology based on the combination of the Theory of Characteristic Modes (TCM) with an Optimization Algorithm, to design a wideband Electrically Small Antenna (ESA) is presented. Unlike other design techniques, loads or matching networks are not needed at the input of the antenna. A design example of an Inverted-L Antenna (ILA) is presented to validate the effectiveness of this technique. © 2017 Euraap

A way to increase the bit ratein ionospheric radio links

The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF-band (3-30 MHz). The applications expected in this study are image transmitting and real-time videoconferencing. Very high rates are required compared to the standard modems. Therefore, an array processing is performed with a set of antennas whose spatial response differs from one another arranged in a circular array or in a collocated sensor. Synchronization (Zero Crossing Detector) and source separation (LMS algorithm) resort to classical well-tested techniques involving training sequences. Experimental results are presented for both antenna configurations. These techniques improve data rate, reaching 20 kbits/s within the 6 kHz bandwidth (QAM 64) without coding or interleaving

ESTIMATION OF DIRECTION OF ARRIVAL (DOA) OF DVB-T SIGNALS IN MOBILE RECEIVING CONFIGURATION

To improve the quality of the mobile reception of DVB-T (Digital Video Broadcasting on Terrestrial networks) signal, the knowledge of the propagation channel characteristics is necessary. In this aim, this paper presents sounding methods and results for the estimation of Direction of Arrival (DoA) of DVB-T signals in mobile receiving configuration. The mobile passive sounder is presented, including postprocessing and radio direction finding tools. Then several results in three kinds of environment are given. 1

Intermodulation distortion and compression point measurement of active integrated antennas using a radiative method

International audienceIn this paper, a measurement procedure allowing the characterization of active integrated antennas in terms of intermodulation distortion and compression point inside of a parallel plate cell is presented. The validity of the radiative measurement is shown and compared to the traditional guided procedure. A good agreement between the two methods shows that this approach allows the evaluation of the overall linearity behavior of arbitrary complex integrated antennas and can serve as a complementary tool when the traditional guided method cannot be applied. © 2017, Electromagnetics Academy. All rights reserved

Capacity estimation of HF MIMO systems

Multiple input multiple output (MIMO) systems utilize multiple antennas at both the transmitter and the receiver. This paper describes some recent experimental work that has been carried out in order to investigate the feasibility of applying MIMO techniques within the high frequency (HF) band. It is a significant development because the potential increase in data rates will benefit not only the existing HF radio systems but also open this band to new low cost communication applications. The capacity estimates for systems employing multiple antennas at the transmitter and receiver in the HF band are computed. Specifically a comparison is made between MIMO configurations employing homogenous antenna arrays and collocated antenna arrays in terms of their envelope correlation and capacity. The results indicate that the HF band can be used for MIMO applications and that compact collocated antennas can replace large homogenous arrays to provide potential capacity gains