A method to generate several phase centres on a single parabolic reflector antenna fed by a digital beamforming array is presented. Among other applications, along-track SAR interferometry at higher frequencies, as for example, in the Ka-band, is considered. Flexibility in size, position and amount of phase centres is similar as for a setup using a direct radiating array.

This paper presents a novel concept of a spaceborne Digital Beamforming (DBF) Synthetic Aperture Radar (SAR) based on a multi-beam reflectarray antenna. The proposed solution offers a number of advantages compared to more conventional DBF SAR systems using planar arrays or reflector antennas. The paper focuses on the spaceborne DBF SAR and discusses its architecture, system parameters and an imaging scenario. A reflectarray antenna design to be used in a combination with the considered imaging platform is presented in the paper. The reflectarray model is used to estimate DBF SAR performance characteristics discussed in the final part of the paper.

In this paper different experiments conducted with the TerraSAR-X satellite for a demonstration of digital beamforming in elevation are shown for a spaceborne SAR system. Processing of the data and different options for digital beamforming are presented.

In this paper the flexibility in modifying the resulting antenna characteristics in terms of location of phase centres and aperture widths, independent of the antenna type used by applying linear combinations of digital beams is discussed. Especially a parabolic reflector can be considered to have the same properties as a Direct Radiating Array (DRA) when used for SAR applications like along-track interferometry.

This paper presents a new evolution of SIGNAL's instrument concept that uses novel Digital Beamforming (DBF) techniques to further extend the coverage of the mission. In addition, by introducing two phase centers in azimuth, which are needed to achieve the swath extension, the system recovers the desired along-track interferometric capabilities.

The European Defence Agency (EDA) engages countermeasures against Improvised Explosive Devices (IEDs) by funding several scientific programs on threat awareness, countermeasures IEDs or land-mine detection, in which this work is only one of numerous projects. The program, denoted as Surveillance in an urban environment using mobile sensors (SUM), covers the idea of equipping one or more vehicles of a patrol or a convoy with a set of sensors exploiting different physical principles in order to gain detailed insights of the road situation ahead. In order to give an added value to a conventional visual camera system, measurement data from an infra-red (IR) camera, a radiometer and a millimetre-wave radar are fused with data from an optical image and are displayed on a human-machine-interface (HMI) which shall assist the vehicle's co-driver to identify suspect objects or persons on or next to the road without forcing the vehicle to stop its cruise.This paper shall especially cover the role of the millimetre-wave radar sensor and its different operational modes. Measurement results are discussed. It is possible to alter the antenna mechanically which gives two choices for a field of view and angular resolution trade-off. Furthermore a synthetic aperture radar mode is possible and has been tested successfully. MIMO radar principles like orthogonal signal design were exploited to from a virtual array by 4 transmitters and 4 receivers.In joint evaluation, it was possible to detect e.g. grenade shells under cardboard boxes or covered metal barrels which were invisible for optical or infra-red detection.

A transmit scheme that uses several timed and directed sub-pulses to cover one common swath is proposed. Timing and ambiguity suppression is presented. The advantages of the proposed scheme are an increased sensitivity compared to one transmit pulse per swath and a simpler activation scheme of the receivers in combination with lower data compression effort on-board a satellite.

This paper presents a novel concept of a spaceborne Digital Beamforming (DBF) Synthetic Aperture Radar (SAR) based on a multi-beam reflectarray antenna. The proposed solution offers a number of advantages compared to more conventional DBF SAR systems using planar arrays or reflector antennas. The paper focuses on the spaceborne DBF SAR architecture using a reflectarray antenna designed for the imaging platform. DBF SAR system parameters, an imaging scenario and a reflectarray antenna model are described in detail. The results of a performance analysis of the SAR system are presented and discussed in the paper.

The major objective of the ESA-funded TRP Activity was to design a spaceborne multi-channel Ka-band SAR optimized for detecting targets moving on land and ocean surfaces, and for estimating their position and motion parameters with high accuracy. A further objecitve was to investigate the capability of the system for ocean surface current measurements. At the conference the study results were presented.

Millimeter-wave (mmW) sensors are an interesting option for several short range applications like the imaging of persons or the monitoring of indoor environments. Due to the small antenna dimensions, compact sensor setups can be realised. This paper will discuss different setups for mmW-sensors based on the principle of a frequency-modulated continuous wave radar with respect to system architecture, calibration concepts, resulting sensor capabilities and imaging results.

For MIMO radar systems orthogonal waveforms are required to distinguish between the different transmitted signals at the different receivers. A hardware cost efficient way is the use of time-multiplexing, where the transmitters are active sequentially after each other. In the presence of platform or target movement, the sampling theorem in the spatial domain (along track) might not be fulfilled anymore which causes problems in the azimuth focusing. In this paper an interlaced switching scheme for a FMCW MIMO radar is proposed to overcome this issue. To verify the proposed method measurements were performed.

This paper covers the role of a millimetre-wave (mmw) radar sensor within a European scientific program with the aim of preventing security or supply patrols from harms caused by improvised explosive devices (IEDs), land-mines etc. in hostile conflict zones. In order to give an added value to a conventional visual camera system, measurement data from an infra-red (IR) camera, a visual camera, a radiometer and a millimetre-wave radar are fused and displayed on a human-machine-interface (HMI) which shall assist the vehicle's co-driver to identify suspect objects or persons on or next to the road without forcing the vehicle to stop its cruise. Within an international consortium, a complete demonstration system with the afore mentioned sensors, as well as a data fusion engine were designed, constructed, mounted on a military patrol truck and successfully tested for different objects in different scenarios. Furthermore, this paper introduces the applied radar modes in more detail and gives measurement results. (6 pages)

This paper covers the implementation of a near-range FMCW radar within a joint European scientific program for force protection from IEDs or landmines. The radar is one of four sensors whose data are fused and evaluated to provide a threat classification of suspicious objects or persons on or nearby the road ahead of a patrol or transport vehicle. A fully functionally low-cost demonstrator system has been implemented and successfully tested. Results are given.

Traditionally well-known from communication applications, the multiple-input multiple-output principle (MIMO) has found its way into radar system theory in the last years. Different arrangements of transceivers equipped with orthogonal signals, lead to arrangements of virtual elements which is denoted as virtual array in the context of coherent MIMO approaches. In order to proof practical feasibility of ongoing theoretical considerations, experiments have been started and evaluated.

For arrays the placement of the single elements determines the angular resolution and the unambiguity interval. The width of the total array determines the resolution capabilities. The wider the elements are placed from each other, the more space in Fourier domain is covered by the measurement and the resolution in time domain will improve. On the other hand the density of the elements has an effect on the angular interval in which objects can be detected unambiguously. For objects within the unambiguous interval grating lobes will appear outside this area while objects outside result in grating lobes in the interval of interest. In this paper the properties of arrays regarding resolution and unambiguity interval will be discussed and methods for the suppression of ambiguous grating lobes are suggested. One approach to suppress the influence of the grating lobes lies in the evaluation of different frequency bands.