M. Younis

Planar artificial magnetic conductors and patch antennas

Surfaces act as perfect magnetic conductors (PMC) if the phase shift of the reflection of an electromagnetic wave amounts to 180/spl deg/ compared to the reflection at a perfect electric conductor (PEC). One possibility to create PMC surfaces artificially is an array of closely spaced patches. In this paper, based on the relation between PMC surfaces and patch antennas, an explanation for the functioning of this artificial PMC is given. An equivalent network is derived that allows to understand the functioning and to provide a starting design for a numerical optimization by aid of fullwave methods. A planar PMC is used for the first time as a reflector for a large aperture coupled patch antenna array, especially in order to reduce the parallel-plate modes that are usually present in traditional aperture coupled patch arrays. An additional sidelobe suppression of over 6 dB has been achieved by the planar PMC reflector in comparison to a traditional reflector.

SAR with digital beamforming on receive only

Since their invention, the performance of synthetic aperture radar (SAR) systems has improved considerably. Operation close to the theoretical limits of accuracy and resolution are possible using state of the art processing techniques and hardware components. Nevertheless, the principle is still the same: The SAR is a side-looking radar where resolution is achieved in range by bandwidth and in azimuth by Doppler processing. The price for improved performance is paid through systems which are more expensive, heavier and highly complicated. This paper presents a new system idea for a SAR with digital beamforming on receive only. Multiple receive antennas are used together with one or at most two high efficiency transmit antennas. The return signal is separately recorded from each receiving antenna. Application for groundbased, airborne, or spaceborne systems is possible and the system configuration simplifies considerably.

Array design for automotive digital beamforming radar system

In this paper, a digital beamforming radar system for automotive short range radar system is presented. It takes advantage of multiple transmitters for increasing the angular resolution. The main focus of this paper is on the optimization of the array configuration to obtain a system for integration into vehicles. A digital beamforming simulator shows the comparison of different configurations.

TerraSAR-X active radar ground calibrator system

In April 2006, the TerraSAR-X satellite was launched. This paper describes the development of a novel and highly integrated, digitally-controlled active SAR system calibrator (DARC). It consists of both an active transponder path for absolute radiometric calibration and a calibrated receiver chain for antenna pattern evaluation of the satellite antenna. A total of 16 active transponder and receiver systems and 17 receiver-only systems will be fabricated for a calibration campaign in 2006.

Multistatic GPR data acquisition and imaging

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.

Implementation of ground-based SAR demonstrator system for digital beam forming

In this paper, the ground-based synthetic aperture radar (SAR) for digital beam forming (DBF) is introduced. Multi channel SAR system is paid attention as a future SAR system with low cost, high flexibility and wide coverage with high azimuth resolution. The DBF algorithm for multi channel SAR can be evaluated using the suggested demonstrator. We present the concept of the measurement and the specific considerations for implementation of this system.

High accuracy digitally controlled active radar ground calibrator system for TerraSAR-X

April 2006, the TerraSAR-X satellite was launched. This paper describes the development of a novel and highly integrated, digitally controlled active SAR system calibrator (DARC). It consists of both an active transponder path for absolute radiometric calibration and a calibrated receiver chain for antenna pattern evaluation of the satellite antenna. A total of 16 active transponder and receiver systems and 17 receiver only systems were fabricated for a calibration campaign in 2006.

An evaluation of performance parameters of reconfigurable SAR systems

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 Parallel-Plate Luneburg Lens Sensor Concept for Automatic Cruise Control Applications

A new system concept for Automatic Cruise Control (ACC) is introduced which is able of covering a wide field-of-view and offers the ability of high azimuth resolution for the detection of several object within one range cell. The system makes use of digital beamforming on-receive-only to simplify the hardware requirements and to facilitate the use of high efficiency processing techniques.

Simulation and measurement of 24 GHz Short Range Radar (SRR) Interference

The automotive industry is currently considering the introduction of Short Range Radars operating near 24 GHz for improving road traffic safety. Short Range Radars are intended to observe the full azimuthal space cover around a vehicle using up to eight sensors. The sensors would operate in an ultra wideband (UWB) mode, occupying 3 to 5 GHz of bandwidth. Interference from SRR transmitters with passive microwave remote sensing satellites could occur as the result of several coupling mechanisms, including direct coupling via the transmit antenna beam and scattering and diffraction of the transmitted signals from leading vehicles, buildings, and other nearby objects. In this study, we estimate the amount of coupling anticipated to occur from SRRs, including the direct and scattered contributions. The calculations are based on bistatic scattering measurements at of a typical automobile and ray optical simulations of reflection and propagation in an urban environment.