A Polarimetric Phased Array Antenna for E-SAR in L-Band

The design of a new L-band antenna for DLR’s airborne synthetic aperture radar system (E-/F-SAR) is presented. Beside operations in L-band new components for a system upgrade were developed. These components are intro-duced. Special interest of this paper is the development of the dual-polarized L-Band antenna with enhanced bandwidth of 150MHz. The antenna feed network is equipped with 2bit hybrid phase shifters to steer the beam between 25° and 40° in elevation. For mounting the antenna at the fuselage of a Dornier Do 228-212 aircraft a rack is described to house several antenna configuration

Measurements of a Multi Feed Reflector Antenna for SAR Systems Based on Digital Beam Forming

In the last years, the Synthetic Aperture Radar (SAR) systems evolution migrates toward the use of multi-channel systems based on Digital Beam Forming (DBF) techniques [1]. This tendendy allows fulfilling stringent SAR requirements, providing high spatial resolution within a wide swath. Moreover, the combination of DBF techniques with parabolic reflector antennas merges both flexibility and high antenna gain ending up in a high versatile system [2]. One of the main parts in a Digital Beam Forming (DBF) Synthetic Aperture Radar system is constituted by the antenna. An accurate characterization of the antenna radiation pattern is of high interest for the calibration of the system which guarantees the performance and versatility of the DBF network. This paper describes the measurements of a multi- feed single offset reflector antenna designed in X-band. The antenna is part of an on ground multi-channel radar system used to demonstrate ind investigate DBF techniques at HR/DL

Dual-Polarized Multilayer L-Band Asymmetric Subarray with Truncated Electric Walls Separation for Airborne SAR Applications

A novel planar phased array of 5x4 multilayer dual polarized aperture coupled stacked patch elements, operating in L-band, with beam steering in elevation and excited with an asymmetric amplitude distribution in azimuth, is presented in this work. The proposed design exploits the restricted available antenna size (2.45λ0 x 1.97λ0) maximizing the number of array elements by means of an interelement spacing of 0.48λ0 and the use of truncated walls. The measurements of the manufactured prototype show an antenna bandwidth of almost 20%, polarization isolation greater than 23 dB and directivity values above 15 dB. Despite the close proximity among the array elements, the measured coupling levels between the feeding ports are lower than -20 dB for the center frequency of operation 1.325 GHz, which makes the proposed work suitable for airborne Synthetic Aperture Radar systems, where a high degree of integration is require

Highly Integrated Low-Profile Multilayer Dual-Polarized Phased Array Antenna with Truncated Cavities for First Pulsed Bistatic L-band Airborne SAR Sensor

This manuscript presents a novel highly integrated dual-polarized multilayer phased array antenna of 40 elements with beam steering in elevation for a bistatic L-band airborne SAR system. The proposed work exploits efficiently the restricted antenna aperture size on the aircraft by reducing the array interelement spacing and improves the antenna element isolation by means of truncated cavities, which allows to maximize the density of array elements. To further extend the degree of integration, the antenna along with the feeding network is assembled in a flight-certified housing where the electrical interconnection is performed without cables. In comparison with the L-band antenna of the current operative DLR's airborne SAR sensor, F-SAR, the presented design provides 66% more antenna elements considering the same antenna aperture size. Thus, the high density of array elements of the proposed solution allows to enhance the beamforming capabilities that are required for next-generation SAR sensors. Precisely, the proposed antenna will be installed under two aircrafts for the operational implementation of the first pulsed bistatic L-band airborne SAR system that will support the technological development of future bistatic spaceborne SAR missions

First Interferometric Trials with the Airborne Digital-Beamforming DBFSAR System

The Microwaves and Radar Institute of the German Aerospace Center (DLR) is known for its consistent work on the field of airborne Synthetic Aperture Radar and its application. Currently, the Institute is developing a new advanced airborne SAR system, the DBFSAR, which is planned to supplement its operational F-SAR system in near future. The development of DBFSAR was triggered by the various evolving digital beamforming (DBF) techniques for future space-borne SAR systems and the need for an airborne experimental platform for preparation of such missions. Additionally, there is a demand for very high resolution SAR imagery, which cannot anymore be fully satisfied with the existing F-SAR system. This paper should give an overview over the current status and performance of the DBFSAR system, including interferometirc results from test flights performed in spring 2017

Benchmarking of Mutation Diagnostics in Clinical Lung Cancer Specimens

Treatment of EGFR-mutant non-small cell lung cancer patients with the tyrosine kinase inhibitors erlotinib or gefitinib results in high response rates and prolonged progression-free survival. Despite the development of sensitive mutation detection approaches, a thorough validation of these in a clinical setting has so far been lacking. We performed, in a clinical setting, a systematic validation of dideoxy ‘Sanger’ sequencing and pyrosequencing against massively parallel sequencing as one of the most sensitive mutation detection technologies available. Mutational annotation of clinical lung tumor samples revealed that of all patients with a confirmed response to EGFR inhibition, only massively parallel sequencing detected all relevant mutations. By contrast, dideoxy sequencing missed four responders and pyrosequencing missed two responders, indicating a dramatic lack of sensitivity of dideoxy sequencing, which is widely applied for this purpose. Furthermore, precise quantification of mutant alleles revealed a low correlation (r2 = 0.27) of histopathological estimates of tumor content and frequency of mutant alleles, thereby questioning the use of histopathology for stratification of specimens for individual analytical procedures. Our results suggest that enhanced analytical sensitivity is critically required to correctly identify patients responding to EGFR inhibition. More broadly, our results emphasize the need for thorough evaluation of all mutation detection approaches against massively parallel sequencing as a prerequisite for any clinical implementation

Design of an airborne dual-polarized tripel stacked patch antenna for broadband SAR application in P-band

The development of a P-band antenna for airborne SAR application is presented. Wide band operation, static electrical antenna beam pointing and small size were key parameters of this antenna array design. First results are shown

E-SAR P-band System Performance

DLR’s experimental airborne SAR E-SAR is well-known in Europe and beyond. It is a versatile system operating in four major radar frequency bands, one of them being the P-band starting at 300MHz. While the DLR is successfully operating the P-band E-SAR under operational conditions for a couple of years now after having finished the development of a new antenna, not much has been published so far about the performance of the system. In this paper the design of the P-band radar sub-system is reviewed and results of a performance analysis are presented

S/C-Chirp: Ein flexibler Radarsignalgenerator für das zukünftige hochauflösende mehrkanalige Flugzeugradar mit synthetischer Apertur F-SAR 2000

In diesem Bericht wird ein breitbandiger programmierbarer digitaler Chirp-Generator für ein neu aufzubauendes flugzeuggetragenes Radar mit synthetischer Apertur vorgestellt. Dieser S/C-Chirp erzeugt nach dem Phasenakkumulatorverfahren (Direct Digital Synthesis) linear frequenzmodulierte Impulse mit bis zu 400 MHz FM-Bandbreite für ein S/C-Band Subsystem und ermöglicht damit eine Entfernungsauflösung von bis zu 37.5 cm. Vorgestellt wird eine Basisversion mit voller Chirpfunktionalität und das Gesamtkonzept in einem S/C-Subsystem. Die Schnittstellen zum Radar sind teilweise bereits definiert. Ausführlich beschriebene Lösungsvorschläge ermöglichen eine flexible Systemintegration

Do228-212 D-CFFU Labormessungen an einem defekten FQT Typ VT087-1

Dieser Bericht beschreibt die Laboruntersuchung eines defekten Tankfüllstandssensors (Fuel Quantity Transmitter, FQT) des DLR Forschungsflugzeuges Do228-212 D-CFFU. Seit dem Jahr 2000 fallen immer wieder FQTs der D-CFFU aus und müssen zur Reparatur zum Hersteller. Dort werden sie, nach dessen Aussagen, meist gereinigt und kalibriert. Leider kann aus dieser Praxis kein Rückschluss auf die Ursache der Ausfälle gezogen werden. Deshalb wird ein defekter FQT geöffnet und im Labor überprüft. Es wird gezeigt, dass die Elektronik des defekten FQT voll funktionsfähig ist