Proceedings with Extended Abstracts (single PDF file) - Radio ...

Digital beamforming.The classical papers of Barton (1980) and Steyskal (1987) on digital beamforming describethe complete capabilities of the concept. It was emphasized in the 80’s that the cost of thewhole digital system was beyond the financial capabilities of Research Institutes. Thepermanent decrease of the cost of digital components in one hand and in the other hand theincrease of their performances allow now to many users access to full Digital Beamforming.E=A(t) j(wt-kr)01NVnN+1Down Converter ReceiverADCADCV IN V QN AnalogDigitalYINY’QNComplex Digitalx Weight WNXIN=YIN.WNX’QN=Y’QN.WNDigital Summation∑XX IN , ∑X’ QNFigure 2 (from Steyskal, 1987) : receiving digitalFigure 2 (from Steyskal, 1987) shows a proposed architecture for a digital implementation inthe receiving mode. Each antenna is associated with a complete receiver. After demodulationand analog to digital conversion the time series I and Q go through the unit wherebeamformer weights are applied. Finally all the signals from all the antennas are summed up.The GPR of the NetLander mission.A complete GPR (Ground Penetrating Radar) unit has been developed at CETP for theNetLander space mission devoted to the geophysical exploration of Mars (Ney et al 2002,Berthelier et al 2003). The goal of the radar is twofold: subsurface sounding for mainly waterdetection and ionospheric sounding for measurement of the ionospheric critical frequencythought to be around 3 MHz during the day and 0.5 MHz during night. The main constraintwas the limited available 500g mass for the whole radar including antennas. This led to thedevelopment of a very compact unit integrated on two 15x13 cm boards.374