|Multimode Sensor Suite|||||Antenna Development|||||APS Interceptor Seeker Development|
|Arbitrary Waveform Generator|||||Hostile Fire Indicator Test System|||||Wake Vortex Radar|
Multimode Sensor Suite
TSC developed a multi-mode Ka-band sensor for the U.S. Army in support to the Joint Common Missile program. The sensor was designed to capture high fidelity digital data of target and clutter returns for post-mission playback to aid in algorithm development and evaluation. The sensor incorporates MTI, STI and HRR (6 inch range cell) SAR modes of operation. A 4-channel monopulse antenna, 3 accelerometers, IMU, transmitter, exciter, 3 receiver channels, synchronous detector and A/D converters are to be housed in a volume of approximately 11 in. by 11 in. by 7 in.
Ground mapping by the sensor drove many of the requirements. This functionality main affected the HRR and SAR modes of the radar. The specifications for these modes are
- Detect and Track Stationary Targets and Record Unprocessed Data
- S/N > 10 dB at ranges < 10 km
- Target cross section < -5 dBsm
- Target velocity < 4 m/s
- Range cell < 6 inches
- Cross range cell resolution < 2 meters for 50 m aperture
- Maximum aperture > 600 m
- Unambiguous range < 2 km
- Range cells recorded per dwell < 62
These requirements were flowed down to each of the subsystems and modules within the radar. TSC TSC Operation designed, fabricated and integrated these modules into a test bed system. The test bed was tested in the field and collected data on various targets of interest.
TSC has performed numerous studies related to antenna concepts and developed a wide variety of custom antenna designs. TSC' expertise includes antenna radiators, arrays and feed networks. In addition to analysis and design, TSC also has the capability to build highly-integrated antenna assemblies for advanced RF systems. The following describes a number of recent projects:
RF Seeker Antenna
TSC has designed, constructed, and tested a Ka-band RF seeker for an active protection system application. The seeker features a multi-antenna beamformer for target detection and tracking. Beamformer elements consist of microstrip patches designed for circular polarization. HFSS was used extensively in the antenna design phase of the program to achieve a circularly-polarized array capable of precise target positioning. The seeker mechanical assembly and integration on the missile platform is shown below. The seeker is highly integrated and consists of a number of subassemblies including the front antenna patch array, a three-channel receiver, exciter, digital signal processor, and DC converter.
Ka-Band RF seeker designed and built by TSC.
Compact Circularly-Polarized Waveguide Antenna
TSC has developed a compact circularly polarized Ka-band waveguide antenna for use as a reference receiver on a missile platform. The antenna features an elliptical cavity to synthesize circular polarization with a single feed. The antenna is end-fed with a probe printed on a dielectric substrate. The antenna is located near the missile plume and is designed to handle the high temperature and high-g environment during launch.
Compact circularly polarized end-fed waveguide antenna. HFSS design to working prototype.
VHF Communication Antenna
TSC has developed a custom VHF antenna mounted on a munition platform. The antenna is a quarter-wave microstrip resonant antenna. The design is rugged enough for use on munition during high-g launch and flight dynamics to support communications with the ground station. Testing of the antenna on the platform included live fire demonstration with successful communications packet reception.
VHF Quarter-Wave Microstrip Radiator
C-Band Vivaldi Antennas
TSC has developed a wideband Vivaldi antenna design for use in a short-range proximity sensor. The C-band antenna system utilizes a wideband Vivaldi design, separated by a partition that is printed on a dielectric substrate. The antennas and partition are arranged for high isolation. HFSS was used for the element design and initial isolation optimization. Excellent agreement exists between the hardware prototype measurements and HFSS predictions.
HFSS model and prototype C-band antennas for a short-range proximity sensor.
Ku-Band Tapered Slot Antenna Array
An example of TSC’ custom antenna design experience is a Ku-band phased array antenna developed for the U.S. Army. The antenna array consists of 8 tapered slot antennas with phase shifters, combiners, and integrated digital control. An onboard processor translates beam commands into appropriate phase shift values taking into account calibrated insertion phase values. Chamber testing validated the expected design performance.
Ku-band, low-profile tapered slot antenna array. Integrated antenna system is shown (left) with chamber testing and beamsteering evaluation (right).
Dual-Band Array Antenna
For the U.S. Army, the company analyzed the possibility of modifying an existing air defense asset to provide surveillance for rockets, artillery and mortars. For this analysis, it was assumed that the RCS of targets exhibit a dominant linear polarity in radar backscatter. Therefore, it was the goal of the study to design a 2-D scanning phased array capable of detecting a target’s orientation.
The tasks included: 1) evaluating appropriate layout of the antenna, 2) examining both rectangular and triangular array geometries, 3) evaluating the proper feed architectures including phase shifter performance, 4) evaluating dual-polarization capability and usefulness of polarity detection methods and 5) providing an array with monopulse capability.
Dual-Band Array (front-view) with Separate Monopulse Tracking Capability (Dual waveguide feeds support X-band and C-band operation)
Inflatable Satellite Dish Antenna
TSC has been working with GATR Technologies to develop inflatable antenna technology. GATR is a small company that produces inflatable antennas for satellite communication applications. Their 2.5 meter antenna has a very large aperture for Ku-band, but weighs only 16 lbs. The entire system weighs 70 lbs. which includes electronics plus cables and ties. Compared to rigid antenna technology, which weighs 800-2,000 lbs. and does not fit into man portable enclosures, the inflatable dish has a clear advantage. To sight and lock with a satellite, there is a portable pedestal for autotracking or the antenna can be tethered to the ground with support wires that can be adjusted for manual pointing. The inflatable antenna has been tested in winds up to 50 mph.
TSC has been supporting the development of the antenna technology through development of feed and electronic equipment concepts as well as system integration and calibration efforts. Members of our staff provided support to test the initial concepts including operating specialized test equipment. In addition, TSC provided field support to various measurement and demonstration activities.
Applications for this technology include first responders, newsgathering expeditions and disaster scenarios. When Hurricane Katrina hit, GATR provided an antenna and communication system to the Red Cross. In addition, the antennas are suitable as temporary fixes for military posts in the Middle East where rigid antennas have been destroyed by mortar fire or other terrorist activity.
The United States Army is implementing a modernization program to create a highly mobile, interconnected and effective force. Envisioned in this concept are well equipped Brigade Combat Teams. These Teams rely on a fast and flexible battlefield network of sensors, unmanned aerial and ground vehicles as well as combat ground vehicles for troops. A key facet of the manned vehicles is survivability. Enhanced survivability is achieved through situational awareness, platform elusiveness and active protection systems.
TSC has developed and is currently in limited rate production of a seeker for an active protection system combating kinetic energy weapons. The seeker is a semi-active RF system that operates in conjunction with vehicle sensors. Our engineers led all aspects of the development from requirements generation to design and fabrication through integration and testing. Having all of these capabilities within the same facility created efficiencies and fostered quality. The AMCOM community can now tout its ability to locally produce complex missile seekers at substantially lower cost than traditional industry primes.
The seeker consists of an interferometer front antenna, three receiver channels, exciter, DSP processor, DC converter and a rear reference antenna. The form-factor and weight restrictions required innovative subassembly design. The seeker electronics will fly in an Army-developed interceptor and must meet missile environment specifications.
TSC developed a radar system for NASA’s Langley Research Center to collect data on wake vortices that are a continuous threat to safe aircraft operations. This radar was designated the Wake Vortex Radar. The sensor was built based on TSC’ design and development efforts initially conducted for the Army’s Rapid Cueing Sensor.
The Wake Vortex Radar is a 35 GHz pulsed Doppler system capable of pulse compression and designed for vortex detection in low visibility conditions at short range. The key system characteristics are:
- 35 GHz (Ka-Band)
- 500 W peak power transmitter for developmental testing
- Parabolic antenna, Cassegrain feed, 58 dBi gain
- Antenna scan rate of 1 to 10 degrees/sec
- Beam width of 0.185° in azimuth (approximately 10 m cross range @ 3 km)
- 25 kHz and 12.5 kHz PRF
- Unambiguous ranges of 6 km and 12 km
- 128 range cells and 512 Doppler frequencies
- Pulse compression using 88 bit phase code
- 5m compressed pulse length
- 450m uncompressed pulse length
At 35 GHz, the radar is sensitive to smaller particles than an S-Band weather radar, but is still able to penetrate weather. It employs advanced real-time signal processing to support field studies. A primary design consideration is the resolution cell size. The diameter of a wake vortex normally ranges from a few meters to tens of meters. To resolve the tangential winds, the resolution cells must be small enough such that the tangential velocity of the vortex will dominate the velocity spectrum of the scatterers. The Wake Vortex Radar utilizes a large, agile parabolic dish antenna to obtain a narrow beam and can use either short pulses or pulse compression for a short range cell. Range resolution can be as short as 5 m, compressed or uncompressed.
TSC has developed a low-cost Arbitrary Waveform Generator (AWG) for a next generation Terrain Following Terrain Avoidance (TFTA) radar system. The AWG was based on a successful SBIR program which produced a unit that had a sampling rate of over 2.3 GSPS and a signal bandwidth to over 1 GHz. Two DAC channels were integrated on a single board which allowed synchronization or independent operation. Clocking and triggering options were designed to give the user a choice of using internal or external clocks and triggers. Additionally, a high speed memory interface was developed to support loading the waveforms in real-time.
Raytheon utilized this design in their new TFTA radar system. TSC Phase IV Systems Operation developed the airborne qualified unit and produced five Engineering Development Units (EDUs) for integration with the radar. Our engineers continue to support the integration and test effort. In addition, PIVC has produced six Pilot Production Units (PPUs) for Raytheon’s first deliveries to the Government.
TSC has developed and demonstrated a high-speed infrared source and radiometer system that supports the Hostile Fire Indicator (HFI) test and evaluation requirements. The HFI Test System, or HFITS, is a portable open-air range (OAR) infrared source (omni-directional) that can simultaneously simulate multiple ground-fire signatures. Ground truth is performed with an integrated infrared radiometer system.
The HFITS infrared source consists of computer-controlled propane torches mounted on a portable and self-contained cart. Individual torch control provides temporal and radiant intensity modulation. Signal bursts down to 40 msec (FWHM) can be produced at repetition rates up to 20 Hz. Radiant intensity levels exceeding 300 W/sr can be produced in the infrared band of interest to missile warning systems.
The HFITS infrared radiometer is used to monitor the simulated HFITS signatures. The radiometer detector head or box utilizes a mercury-cadmium-telluride (MCT) mid-infrared detector that is DC-coupled, allowing monitoring of slowly changing signatures. The MCT detector is thermo-electrically (TE) cooled and features fast response and low drift. Analog-to-digital conversion is performed inside the detector box at a 30 kHz rate. The electronics bandwidth is 10 kHz. Multiple detector boxes can be configured for simultaneous monitoring in several infrared bands.
For more information please download the HFI Test System Fact Sheet (PDF)