Terje Johnsen

Simultaneous use of multiple pseudo random noise codes in multistatic CW radar

In multistatic continuous wave radar, the choice of codes and frequencies used for transmission has a strong influence on detection and ease of parameter extraction. The paper describes the various effects of using single and multiple codes in a number of separated transmitters, either with the same or separated carrier frequencies. To visualize some of the results, synthetic radar data have been generated and used in the processing.

Hovering helicopter measured by bi-/multistatic CW radar

The use of bi-/multistatic radar to detect and extract parameters for classification of a hovering helicopter has been studied. An experimental continuous wave bistatic radar has been used in a series of measurements covering a range of bistatic geometries. Variations in detection of rotor tip velocity, number of blades of main and tail rotor and direction of Doppler shift is observed. The use of a series of bistatic receiver pairs (multistatic radar) will increase the ability to extract characteristic parameters that would enhance classification.

Change detection and detailed analysis of stacking configuration of containers in TerraSAR-X SAR images

This paper analyses two SAR images recorded on different dates of the same container harbor. To understand the detailed structure and stacking order of different areas of the harbor, theoretical and model studies has been applied. These studies revealed the predominant scattering regions of container stacks. This knowledge is used to quantify stacking heights, orientation and steps in the container structure of the two TerraSAR-X SAR magnitude images. Calculations from a change detection algorithm provided an image that emphasized regions in the two where major changes to the stacking configuration were observed. Detailed analysis is focused on a few selected regions resulting in knowledge of numbers of containers moved and structure in the clusters.

Coherent change detection in SAR images of harbors with emphasis on findings from container backscattering

The use of Coherent Change Detection (CCD) in analysis of TerraSAR-X images with high fidelity co-registration reveals a rich set of information. In this study, the harbor of Oslo is depicted and three container terminals with different orientation of containers towards the radar have been of special interest. In this paper, results are visualized by use of color composite images where the RGB channels contain day 1 and 2 intensity images and sample coherence, respectively. Extraction of details of container stacking, cluster configuration and rearrangements has been explored. The visualization shows clearly the appearance of various objects in the scene that has been removed, moved in or been replaced from day 1 to day 2 with distinct coloring differences. Examples also present other objects typically found in harbors and their appearance for a more complete understanding of the scene activity and as an important input for monitoring the area and scheduling new recording geometries.

DVB-T passive radar dual polarization measurements in the presence of strong direct signal interference

A dual-polarization passive bistatic radar is used to evaluate the potential benefit of cross-polarized measurements for the suppression of strong direct signal interference in the DVB-T band. The linear array antenna consists of 10 bowtie elements, 5 of which measuring horizontal and 5 vertical polarization. Two small GPS-equipped aircraft were used as targets, flying prescribed patterns. Two antenna locations were used, one in which the broadcasting transmitter was only 20° from the antenna boresight, causing strong direct signal interference, and one in which the antenna was partially shielded from the transmitter. In both polarization channels, reconstruction of the reference signal and reciprocal filtering was used to suppress interference. GPS data from the aircraft was used to find the bistatic range, Doppler, and azimuth location, and the signal to interference pluss noise ratio (SINR) at this location was measured. In addition, the azimuth inferred from GPS was compared with the direction derived from the radar measurements. We find no advantage using cross polarization, even in the case with strong direct signal interference: On average there is no significant difference between co- and crosspolarized SINR, and the co-polarized channel is slightly better predicting the correct azimuth.