PARSAX (PARSAX)Themes: Radar for Remote Sensing and Targets Characterization
, Radar technology
PARSAX is "Polarimetric Agile Radar in S- and X-band", a versatile, programmable radar developed by MS3 and located at the roof of the EWI building.
In radar applications, the objective of recovering the most target information, to improve radar target detection, discrimination and classification capabilities, is pursued through the measurement of 2 x 2 complex monostatic target scattering matrix. Because simultaneous measurement of the backscattering matrices of radar targets becomes very important while using high carriers, a new radar system will be developed within the PARSAX project. The PARSAX radar will be able to transmit and receive two orthogonal signals simultaneously. The signals should be orthogonally polarized and orthogonal in time. The four elements of the backscattering matrix are retrieved on reception by correlating the signal on each polarization channl with both orthogonal signals. The nature of the signals might be chosen arbitrarily but in this report we focus mainly on LFM (FMCW) and Phase Coded signals. Note that the use of different kinds of signals such as LFM and Phase Coded signals in the same radar system might be a very citical aspect of the design.
The PARSAX radar system must operate at S-band centred at 3.315 GHz and at X-band centred at a frequency between 9.6 GHz and 10 GHz. The range resolution required for close range measurements is set to 3 m. This value leads to a signal bandwidth of 50 MHz. If we consider noise-like Phase Coded signals modulated by m-sequences, the duration of one pulse is 20ns. We must take into account while choosing the signal duration, that for PSK.
For the S-band version of the PARSAX system, transmit and receive antennas will be those used in the Delft Atmospheric Research Radar (DARR) system. They are located on the roof of the 92 m high building of the faculty of Electrical Engineering in the TU Delft.
As indicated in the project name (Polarimetric Agile Radar in S- and X-band), the system is polarimetric agile, i.e. it will transmit (correspondingly receive) simultaneously two orthogonal signals via two orthogonal polarization channels for the transmitting mode and two channels (co-polar and cross-polar) in the receiving mode. It is a Doppler polarimetric radar. One of the positive aspects of PARSAX is that the sounding orthogonal signals will be digitally generated and the BSM will be chieved with the optimization of the radar parameters (centre frequencies, bandwidth and polarization) in real time. It is important to recall that polarimetry is a methodology for the determination of the polarisation-dependent reflection of a stationary radar target while Doppler-polarimetry is a methodology for the determination of the polarisation-dependent reflection of multiple moving radar targets. Doppler-polarimetric radar is able to characterize more radar details of these targets, which results in possibilities for classification and identification.
The theoretical and validated methods provided by PARSAX will be used in many applications such as atmospheric remote sensing ad surveillance or tracking. Thus not only FMCW signals will be used in the PARSAX radar system but also any arbitrary signal for instance SFCW, PCM (Phase Coded) signals and noise-like signals (binary or multi-level coding). In the first steps of radar system design, a special attention will be given to FMCW (sawtooth or triangular modulation) and PCM signals. Considering that the required range resolution is equal to 3 m, the signal duration should be 20 ns. The sweep frequency for a LFM signal will vary from 2 MHz to 50 MHz. The sweep time must be greater or equal to 0.655 ms.