Abstract: Presented in this invention is a technique for producing a null in the frequency spectrum of an FM signal pulse, the null matching an interference that has been superposed on the signal pulse. By matching the null to the interference, the energy in the frequency spectrum is shifted in such a way that when the interference is rejected by a band elimination filter, none of the useful energy would be discarded along with the rejected interference. Consequently, a signal resulting from the technique has a much higher amplitude than previously filtered signals. This leads to the signal being more readily recognized by detection systems, such as a radar detector.

Abstract: A method and system for phased array radar antenna calibration to be made in flight employs a synthesized initial transmission signal having a notch in the main direction of beam. This has the effect of returning reflected receiver signals that are main lobe clutter free, but contain clutter returned solely from the sidelobe radiation. The received clutter data is processed to yield a set of coefficients that, when combined with subsequent radar signal return resulting from a signal having a main lobe, provides a return signal that is free from aircraft induced distortions and misalignments that can result in sidelobe induced false alarms. All data processing is conducted in the time domain rather than the frequency domain, thus, avoiding Doppler frequency foldover problems due to ambiguities from signals received at multiple aspect angles.

Abstract: A hyperthermia treatment apparatus includes an annular radio frequency (RF) antenna array with bolus that is compatible with a magnetic resonance imaging (MRI) machine. Antenna elements polarized parallel to the axis of the cylinder are used for forming a Specific Absorption Ratio (SAR) map as well as for directing the energy to accomplish hyperthermia. The array may be dynamically controlled to focus energy at any specified region within the cylinder. The array is positioned inside an MRI machine and is tuned to the machine's hydrogen resonant frequency. For treatment planning, the array is employed to form an SAR map via RF current density imaging. Using this map, array phase, amplitude, and temporal weighting are optimized until the SAR maxima is congruent with the treatment volume. For treatment, RF radiation is applied to the subject to induce heating of the treatment volume using these optimal array parameters. Temperature is periodically determined via noninvasive MRI methods (i.e.

Abstract: An ultra-broadband transverse electromagnetic (TEM) exponential antenna in which the radiating or receiving structure comprises first and second elongated conductors have a feed end comprising first and second narrow conductor strips. At an opposite radiating or receiving end, the widths of the first and second conductors expand exponentially in the H-plane, and the spacing between the first and second conductors expands exponentially in the E-plane, thereby providing a double flared, exponentially tapered, transverse electromagnetic horn antenna. Two TEM horn design embodiments are described herein and differ only in the lauching device by which the radiating structure is fed, which converts an input unbalanced transverse electromagnetic wave into a balanced transverse electromagnetic wave. A first preferred embodiment employs a stripline infinite balun as a launching device, while a second embodiment employs a cavity backed waveguide as a launching device.

Abstract: A scannable antenna array especially suited for aircraft having a common reflector and a plurality of spaced apart end-fired Yagi type elements each comprising a driver and one or more director segments spaced mutually from each other and the driver in the direction of the field pattern for the array. In the preferred embodiment, the driver is a dipole comprised of two laterally extending hooked-back radiating segments so dimensioned and spaced from the director elements so as to minimize the mutual electromagnetic coupling among elements of the array. In other embodiments, the driver may comprise a slot.

Abstract: An electronically scanned antenna system having a linear array of endfire elements. The endfire elements are laterally spaced between about 0.3 .lambda. to 0.9 .lambda. apart, preferably about 0.55 .lambda. apart, to enhance the effects of mutual coupling therebetween for broadening the radiation signal pattern of the elements in the plane of the array. Advantageously, the endfire elements may be of the Yagi type with each endfire element including a common reflector, a driver, and a plurality of directors.

Abstract: An antenna system is provided having a common reflector and a plurality of spaced apart end-fired yagi type elements each comprising a driver and one or more directors. The elements are positioned longitudinally parallel to each other in separate planes. Adjustable parasitic reflecting rods are located adjacent to the elements so as to cause the generation of a low energy scattering field which, in turn, increases inter-element isolation.