Martin, S.R.; Genesca, M.; Romeu, J.; Arcos, R. IEEE transactions on aerospace and electronic systems Vol. 50, num. 2, p. 1330-1346 DOI: 10.1109/TAES.2013.120176 Data de publicació: 2014-04-01 Article en revista
A passive acoustic method to locate moving sound sources is applied to maneuvering aircraft. The advantages of the method are that it is suitable for all kinds of aircraft, not only propeller-driven, and is not restricted to low height above the ground. Its applicability could be, for instance, to supplement aircraft noise monitoring systems or to supervise small airports' activities. The method is based on the relation between the relative Doppler effect observed from a set of at least seven microphone receivers, distributed in the airport surroundings, and the aircraft position and speed. The method requires knowledge of the position of the aircraft at the start of takeoff. The ambiguity function is used to calculate the relative Doppler stretch of the spectrum of the sound between pairs of microphones. The results of applying the ambiguity function are the inputs to a system of equations that relates the aircraft position and speed to the relative Doppler frequency stretches. This system of equations is solved using a genetic algorithm. The performance of the method was tested by computer simulation. The results showed that the location errors are of the same order of magnitude as the size of an average aircraft, even if the takeoff position is not accurately known.
Aja, B.; Pascual, J.; Fuente, L.; Detratti, M.; Artal, E.; Mediavilla, A.; Paco, D.; Pradell, L. IEEE transactions on aerospace and electronic systems Vol. 41, num. 4, p. 1415-1430 Data de publicació: 2005-10 Article en revista
This work describes the principle of operation, assembly and performance of one branch of the 44 GHz back end module (BEM) for the Planck low frequency instrument (LFI). This subsystem constitutes a fully representative branch of the qualification-model version (QM). It includes waveguide to microstrip transition, GaAs pseudomorphic high electron mobility transistor (PHEMT) low noise amplifiers (LNA), bandpass filter, square-law detector and dc amplifier. The fundamentals of the design of the RF part are described and all of the components have been tested individually before integration. Using single tone and wideband noise stimuli, the output voltage has been measured for several input powers, in order to obtain the sensitivity factor of the complete BEM. The effective bandwidth and the equivalent noise temperature have been calculated from the measurements, taking into account the frequency dependence on the noise source and the BEM. Finally, the low frequency output power spectrum has been obtained and a maximum 1/f knee frequency around 200 Hz has been measured with a 3 dB output signal video bandwidth above 50 KHz.
Elias, A.; Broquetas, A.; Antequera, J.; Yuste, J. IEEE transactions on aerospace and electronic systems Vol. 28, num. 1, p. 276-285 DOI: 10.1109/7.135453 Data de publicació: 1992-01 Article en revista
Detection systems with distributed sensors and data fusion are increasingly used by surveillance systems. A system formed by N inhomogeneous constant false alarm rate (CFAR) detectors (cell-averaging (CA) and ordered statistic (OS) CFAR detectors) is studied. A recursive formulation of an algorithm that permits a fixed level of false alarms in the data fusion center is presented, to set the optimum individual threshold levels in the CFAR receivers and the optimum `K out of N' decision rule in order to maximize the total probability of detection. The algorithm also considers receivers of different quality or with different communication channel qualities connecting them with the fusion center. This procedure has been applied to several hypothetical networks with distributed CA-CFAR and OS-CFAR receivers and for Rayleigh targets and interference, and it was seen that in general the fusion decision OR rule is not always the best
It is necessary for automatic detection radars to be adaptive to variations in background clutter in order to maintain a constant false alarm rate (CFAR). A CFAR based on an ordered statistic technique (OS CFAR) has some advantages over the cell-averaging technique (CA CFAR), especially in clutter edges or multiple target environments; unfortunately the large processing time required by this technique limits its use. The authors present two new OS CFARs that require only ahlf the processing time. One is an ordered statistic greatest of CFAR (OSGO), while the other is an ordered statistic smallest of CFAR (OSSO). The OSGO CFAR has the advantages of the OS CFAR with only a negligible increment to the CFAR loss
Figueiras, A.; Casar, J.; Lagunas, M.; García, R. IEEE transactions on aerospace and electronic systems Vol. 18, num. 6, p. 724-729 DOI: 10.1109/TAES.1982.309293 Data de publicació: 1982-11 Article en revista
The problem of sampling signals maintaining the theoretically minimum (average) sampling rate and allowing a separate interpolation is considered from a general point of view. The formulation will follow a recently published method for multichannel sampling; this way there is the advantage of working with functions depending only on the frequency and not on time and frequency as in other approaches. This simplifies the general expressions and the determination of separation conditions. Under the assumption of nonsingularity of certain matrices, we obtain the necessary and sufficient conditions for a separate interpolation and discuss them. Finally, an especially important case is considered as an example.