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The Tud C-band Sar - Geoscience and Remote Sensing Symposium, 1988. IGARSS '88. 'Remote Sensing: Moving Toward the 21st
| Content Provider | Semantic Scholar |
|---|---|
| Author | Lintz, Erik |
| Copyright Year | 2018 |
| Abstract | At the Electromagnetics Institute, Technical University of Denmark, a C-band high resolution airborne SAR i s presently being constructed. The radar uses digital pulse generation with a bandwidth beyond 100 MHz. This ensure large flexibility and a possibility to use predistorted codes to account for a non-perfect transfer function of the modulator and the up-converter. Pulse compression is also performed digitally . The radar data i s preprocessed and dumped to a HDDT (high density digital tape) recorder, for later processing on off-line computers. A later phase of the project i s concerned with constructing a real-time processor and a display facility to be carried with the radar in the aircraft. The calibration fidelity of the radar has been of great concern and this is reflected in the design in several ways: the analog parts of the radar are temperature stabilized, and several calibration loops are incorporated in the system. The TUD C-band SAR is a single frequency system operating at 5.3 GHz. I t is designed to obtain a resolution down to 2 m by 2 m. The maximum range of the system is 80 km and the swath width is between 10 and 50 km depending on the resolution. Both maximum range and swath width are prepared for later upgrading. The radar system is designed for installation in moderate sized jet aircraft. The system parameters are listed in Table 1 and the system block diagram is shown in Figure 1. The basic pulse generation is carried out in the two channel, baseband digital pulse generator, consisting of code storage and D/A converters. This ensure excellent flexibility as the codes can easily be changed. Furthermore the codes can be predistorted to account for predicted or measured modulatodupconverter properties, so that the signal driving the TWT amplifier will be correct ( important as the TWT is not operated in its linear region). The digital codes (up to 4096 samples long and each sample consist of 8 bit I and 8 bit Q data) are converted to analog signals at a 200 MHz sampling rate in dual D/A converters and the analog I and Q channels are transformed to a 300 MHz I F signal in the quadrature modulator. In the up-converter the signal is converted to 5.3 GHz and the signal is amplified to a level sufficient to drive the TWT tube ( 22 dBm). 100 MHz, 300 MHz and 5 GHz local oscillator signals are generated in a refFrequency: 5.3 GHz Transmitter peak power: 2 kW Receiver noise figure: 2.5 dB Total system losses ( estimated): Pulse length: Maximum bandwidth: loo M H Z Antenna g a i n : 27 dB 3 dB from 0.64 to 20 p azimuth beamwidth: 2.7 elevation pattern: 40° section of cosec sqr. polarization: vv Resolution range: Variable 2,4,8 m azimuth: Variable 2,4,8 m Slant range mapping width: Range: 80 km Variable 9.3,21.6, 46.2 km Table 1: System parameters j : ......................................................... 1553hu / ~ ~ T ! ! ? p q 1 1 U s . u k n Figure 1: Block diagram. erence oscillator unit, while 200 MHz is derived in the timing unit. Following the driver the signal is injected into the TWT power amplifier and a sample is directed into the Calibration Switch. The power level of the drive signal i s controlled by a variable attenuator in a closed control loop. The power amplifier is a 2 kW Traveling Wave Tube amplifier with low phase noise. Following the TWT the signal i s guided to the antenna. Proceedings of I G M S '88 Symposium, Edinburgh, Scotland, 13-16 Sept. 1988 Ref: ESA SP-284 (IEEE 88CH2497-6). Published by ESA Publicaiions Division, August 1988 Authorized licensed use limited to: Danmarks Tekniske Informationscenter. Downloaded on July 01,2010 at 09:38:25 UTC from IEEE Xplore. Restrictions apply. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://orbit.dtu.dk/files/4483108/Madsen.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
