Custom Antenna Design
Millitech has over 25 years experience in the design of microwave and millimeter-wave antennas. Millitech has the software, expertise, and test facilities to develop a wide range of custom antennas for millimeter-wave applications such as multi-band MIL-SATCOM terminals, radar, imaging, radio astronomy, environmental remote sensing, autonomous robotic sensors, and industrial sensors. In addition to our own antenna experts, we also have a close relationship with the University of Massachusetts Antenna Center which has world-class faculty in this area.
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Planar Antennas and Arrays
Millitech has developed designs for planar microstrip antennas that are being used for satellite, radar, and LOS communications.
Custom Reflector Antennas
Millitech designs and manufactures custom reflector antennas for application-specific requirements. For example, we designed a reflector used on a new W-band radar system designed to detect foreign objects on airport runways. The system has circularly-polarized fan beams that operate over a wide bandwidth, and a reflector design that provides for convenient co-alignment of the transmit and receive beams. Similarly, we have developed a 48" W-band Cassegrain with high beam efficiency for radiometric measurements. The reflector's surface is true to .001" RMS which has the effect of reducing the residual sidelobe level.
Millitech has developed monopulse antennas with waveguide feeds, and dual polarization monopulse antennas for lenses and reflectors. The most important attributes of these antennas are their compact size and low loss. This figure shows a 3" dual polarization, dual channel (AZ/EL), Gaussian Optical Monopulse antenna for W-band.
Millitech has designed dual polarization multi-band antennas primarily for satellite communication (SATCOM) applications. The key element of these antennas is their multi-band feeds. Multi-band feeds reduce the mechanical complexity for new generation SATCOM antennas, while increasing the communications capacity of existing SATCOM antennas. Mobile "COM on the move" applications have size and weight limitations. These feeds enable single aperture simultaneous mobile coverage. For example, the Wideband Gapfiller satellites will have capability in both Ka-band and X-band. Millitech has developed Dual-, Tri- and Quad-band feeds for these applications.
Gaussian-optic Lens Antennas
Millitech has a 25 year history of designing high performance Gaussian-optic, or quasi-optic antenna systems. Applications include radar, surveillance, remote sensing, material studies, avionics, radio astronomy, and plasma diagnostics. The major advantage of quasioptics is low loss, particularly at near millimeter and submillimeter wavelengths. The actual loss in propagation between focusing elements can be made arbitrarily small by proper system design.
Another important advantage of free space transmission versus waveguide is the ability to support all polarizations. Very high isolation (on the order of 30 dB) can be maintained between orthogonal polarizations. Gaussian optics can also support more than one spatial mode, which is useful for both imaging and monopulse feed systems.
In addition to a robust standard product listing (see GOA), Millitech has developed custom lens antennas up to 24 inches in diameter as well as cylindrical lenses. Custom GOAs can be provided in numerous application-specific configurations. Some recent examples include:
Millitech has been designing transreflectors for 15 years, including designs for use in Automotive Collision Avoidance Radars. A transreflector consists of a metal grid, feed, and a polarization "twist-plate". Incoming linearly-polarized radiation passes through the grid, reflects off the twist-plate in the orthogonal linear polarization, reflects again off the grid, and is focused into the feed. Because of the folded optics, the antenna is more compact than an equivalent standard reflector. The grid provides excellent cross-polarization isolation, and the twist-plate can be mechanically scanned to move the antenna beam. Transreflector benefits include:
Indoor Compact Antenna Range
Millitech has an indoor Compact Antenna Test Range for testing antennas from 2 inches to 10 feet in diameter. The range is optically focused to produce far field simulations from 7 GHz through 220 GHz. Test equipment includes an Agilent PNA capable of vector measurements up to 50 GHz. Millitech-designed frequency converters are used to extend this range. The positioner can handle virtually any load up to 1000 lbs. and testing capability runs 24/7, in a climate-controlled environment.
Millitech's capabilities measuring high gain millimeter wave antennas are unsurpassed with our Near-field Range (NFR). In a traditional Far-field Range, large millimeter-wave antennas can require in excess of 1,000 m of range for accurate measurements. Because of the distance requirements, this often means testing outdoors in an uncontrolled environment, which results in an unacceptable amount of variability in the measurements.
For millimeter-wave phased arrays, accurate measurement of such antennas and the ability to troubleshoot down to specific elements are required. We are currently equipped with a Nearfield Systems 5' x 5' planar Near-field Antenna Range with a granite base for added stability. Our Near-field Range allows us to move this testing into an indoor controlled setting and measure large high gain antennas with sidelobes in some cases 50 dB below the peak, and beam pointing to the 1/100th of a degree from 8GHz to 225GHz using phase coherent Millitech frequency extenders. For a near-field measurement, the phase front measured in a close proximity to the antenna under test is mathematically transformed into a far-field pattern using the FFT algorithm. With higher frequencies, reflector imperfections in a traditional compact range and reflections within the room become a significant source of error.