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The DART RF Measurement System is an ultra-wideband radar capable of detecting, locating and classifying targets at short range. It can be employed in a number of configurations:
• Laboratory/anechoic chamber
‒ Fixed location for the measurement of moving targets
‒ Moving platform for the measurement of fixed targets
• Mounted on a ground vehicle for remote measurements of fixed and moving targets.
DART supports:
• Doppler processing for the detection of moving targets
• SAR and ISAR imaging
• Dual polarization measurements on receive
• Extended target shape (including wires attached) analysis using the generalized inner product (GIP) processing
• Analysis of resonances (late-time returns)
System Description
The DART RF Measurement System consists of:
1) Radar Hardware, 2) Transmit and Receive Antennas, 3) Radar Controller, 4) Experiment Controller, and 5) Mounting Platform. This system has been employed in a number of configurations.
The DART System
DART radar is a real-time implementation of a dual 2 port network analyzer, i.e. one stimulus channel transmits and two independent response channels receive and process the received radar signal. These channels record co-polar and cross-polarized data referenced to the transmit beam.
A wideband stepped frequency waveform is generated and transmitted. It is then received, on the cross-pol and co-pol antennas. The received signals down-converted by a similar generator with a small offset
(250 KHz), A/D converted (16 bits @ 1 MHz sample rate), and recorded continuously. Each complete frequency sweep is 80 msec., followed by a short fly-back time.
During normal operation, the transmit drive sweep is sent to the antenna, where a final power amplifier boosts the power to approximately +20 dBm. This reduces mismatch effects caused by the antenna, since the transmit drive signal is terminated at the power amplifier, and a very short cable is used from the amplifier to the antenna.
The receive signals run through receiver protection limiters and amplifiers, are then converted to low IF signals by the swept offset LO. These signals, centered at 250 KHz, are converted to digital signals and recorded. The three channels of data are stored on a rack mounted dual-core server in the truck, which also controls the other radar functions. The data is processed and displayed real-time on a laptop in the vehicle cab.
Platform
| The DART system can be employed in a laboratory or chamber, or it can be mounted on a vehicle. It has been mounted in a Chevy Blazer truck. It has a 28V generating system that we invert to supply 120VAC 60 Hz for the equipment. All the radar power supplies are linear to reduce noise. The coaxial lines are RG-141 hard line. |
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Transmit and Receive Antennas
The antennas are cavity-backed spirals that radiate circular polarization. The gain is fairly low due to their wideband response and small size, so a wide area ahead of the vehicle is radiated. One antenna transmits, and the two receive co-polar and cross-polar relative to the transmit antenna. The present configuration consists of a transmit antenna mounted on one side and the two receive antennas mounted one above the other on the other side. This configuration reduces parallax between the two polarization and permits calculation of the ratio of these two returns.
The antennas can be mounted on a rack extending over the hood of a vehicle. In this configuration, the antenna bar is moveable: 0,90, and 30 degree points using holes that are predrilled.
DART RF System Specifications
Transmitted power: 100 mW
Transmit frequency range: 300-3000 MHz
Polarization: circular
Antenna directivity: 3 dBi
Receiver noise figure: 5 dB
Weight: approximately 250 pounds (600 kg)
Power requirements: 120VAC 60 Hz, or 13.8 VDC negative ground, 600 watts.
Display: 15 inch laptop PC internetted with signal processor PC
Instrumented range: 50 meters
Dynamic range: 60 dB
PRF: 80 msec.
Shipping case: rotomolded polyethylene shock-mounted shipping case, 19 inch EIA , 16U high, with automatic ambient pressure equalization valve pressure (MIL-STD-648C), spring-loaded handles, and removable casters.
Size, radar unit (cm): 94 wide, 69 deep, 99 high
How to Order Your DART RF System
To order your DART RF System, or for more information, please contact Stiefvater Consultants:
Stiefvater Consultants, Inc.
10002 Hillside Terrace
Marcy NY 13403
PHONE: (315) 334-4365
FAX: (315) 733-0474
E-mail: k.stiefvater@sc-radc.com
SAC Hill office:
584 Phoenix Drive
Rome NY 13441
PHONE: (315) 338-0932 or (315) 338-0934
FAX: (315) 338-0935
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