This paper gives an overview on current activities at Astrium GmbH in Friedrichshafen in the field of technology development for future space-borne X-SAR systems based on Digital Beam Forming. The focus is on the verification of scan-on-receive beamforming in the frame of the DLR funded “High-Resolution-Wide-Swath (HRWS) demonstrator” project.

The factorization method (FM) has been applied to measurement data from a multistatic ground-penetrating radar operating in close proximity to the ground, which was used in a measurement campaign on the Joint Research Centre mine test lane in Ispra, Italy. This paper is targeted toward a future hand-held demining system. The according space limits restrict an independent positioning of transmit and receive antennas. Hence, very small multistatic datasets are obtained, representing a difficult case for the reconstruction with the FM

The rapid progression in digital hardware and signal processing capabilities stimulates the development of radar systems. The tendency is to move the digital interface toward the antenna, replacing, whenever possible, analog RF-hardware. Based on software codes, these digital systems are more flexible and easier to reconfigure than RF-hardware. This letter illustrates the general concept for digital beamforming (DBF) in synthetic aperture radar systems and investigates their principle capabilities, limitations, and performance parameters. It is shown that using DBF a simultaneous improvement in azimuth coverage and resolution can be achieved.

This paper proposes multistatic measurements to increase the information content of ground penetrating radar data. Three different acquisition strategies are distinguished. To obtain measurement data, a flexible setup has been realized. Tomographic backpropagation and the nonlinearized factorization method are discussed with regard to their applicability to multistatic data.

Cryosat is an approved ESA mission. Its objective is to determine fluctuations in the Earth's land mass and marine ice fields. The mission utilizes a completely new SAR/interferometric altimeter concept, which combines a nadir-looking configuration with pulse-limited altimetry. The concept has been verified by simulations, but no dedicated experimental validation has been performed so far. For this reason, an Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) is currently under development in the frame of an ESA contract. Due to the large bandwidth of the system, several components, i.e. the chirp generator, are critical and therefore require innovative solutions. A dedicated software performs SAR- and interferometric radar data processing and, in addition, supports internal instrument calibration. ASIRAS is intended to be tested, verified and optimized on a DO 228/100 aircraft carrier during a measurement campaign scheduled fall 2002 in the area of Fram Street north of Greenland. The paper presents mission objectives, the instrument concept of ASIRAS, and critical building blocks.

The rapid progression in digital hardware systems and signal processing capabilities is increasingly advantageous for the development of radar systems. The trend is to move the digital hardware towards the antenna front-end replacing, whenever possible, RF-hardware. Based on software codes these digital systems are more flexible and easier to reconfigure than RF-hardware. This paper investigates capabilities and limitations of synthetic aperture radar systems utilising digital beamforming.

A novel stochastic channel model for the indoor propagation channel is presented. It is especially for, but not limited to future communication systems with multiple antennas like space division multiple access (SDMA), spatial filtering for interference reduction (SFIR), or multiple-input/multiple-output (MIMO). The model is designed for indoor scenarios, straight forward extendable to urban environments. It is based on physical wave propagation. The new approach describes the channel by multipath components, each characterized by its transfer matrix (including loss), delay, direction of arrival, and departure. The appearance and disappearance of multipath components over time is modeled as a birth and death process, a marked Poisson process. This enables first-time the correct modeling of spatial and temporal correlations. In each modeling step, path properties change according to the motion of transmitter and receiver. The changing delay times of propagation paths yield a realistic Doppler behavior of the channel. Deterministic ray tracing results are used to produce the huge data sets required for the statistical evaluation of the parameters of the proposed model. This method enables an automated parameter extraction for new environments or frequencies. The ray tracing tool has been verified by narrowband, wideband, and directional channel measurements. The novel stochastic spatial channel model allows the simulation of third-generation broadband radio systems including arbitrary antenna configurations and patterns. System simulations for the bit-error rate of radio links can be performed including intelligent antenna configurations like SDMA, SFIR, or MIMO. Furthermore, the capacity of complete systems can be investigated.

A novel stochastic spatial propagation channel model for wide-band spread spectrum applications is presented. The model is set up for indoor scenarios, although in principle it can be extended easily to urban environments. Deterministic ray-tracing results are used to produce the huge data sets required for the statistical evaluation of the parameters of the proposed model. The approach for the stochastic model is based on physical wave-propagation, where the channel is described by multipath components including angles of arrival at the receiver and angles of transmission at the transmitter. In each modeling step, path properties change according to the movement of the radio stations (RSs). The appearance and disappearance of multipath components is modeled by a genetic process. Especially, changing delay times of the propagation paths yield a realistic Doppler behavior of the channel. A new approach to model the directions of multipath components in three dimensions has been developed. By relating the angles of arrival (or transmission) to the direct line between transmitter and receiver, a universal modeling approach, which is independent of the actual geometry, becomes possible. The novel stochastic spatial channel model allows the simulation of complex systems including arbitrary antenna configurations and patterns. A detailed description of the overall model is presented together with some initial simulation results.