SIGINT Systems, LLC — Department of Defense SBIR Phase I: N231-003

Description

The proposed system consists of two types of antenna arrays, a low frequency vector sensor for coverage below 300 MHz and a high frequency circularly dispersed array with coverage to 20+ GHz. Both arrays are omni directional  with enhanced response across their entire operating frequency range. Both antenna arrays can handle horizontal, vertical or elliptically polarized waves. The low frequency sensor can handle all HF propagation modes; ground and sky waves including NVIS. Both arrays are designed for operation on ground vehicles and designed to MIL-STD 810H requirements for such systems. Two antenna sets are proposed, one for transmit and the other for receive operations. The receive antennas have built in overload protection to guard against the effect of strong nearby emitters.  The antennas are radio agnostic and can be connected to any set of coherent radios with a standard 50 or 75 Ohms impedance interface. We recommend the use of coherent radios for the DF of modern signals, though nothing stops the high frequency array from being used as a commutated DF system. The low frequency system includes a full RF front-end and can be connected to a set of 3 coherent ADCs if desired. This eliminates the need of radios for that array, reducing system cost. The RF front-end includes a set of programmable notch filters that can be used to eliminate strong interferers. It also supports a programmable gain with a range of 32 dB. The antennas are capable of producing DFs with an accuracy of ~2 degrees RMS. The antennas can also be used for beam forming for enhanced pickup, interferer mitigation or directed transmission.