초록 ▼

A system for calibrating airborne direction finding antenna arrays eliminates the problem of trying to maintain a constant depression angle when flying an airplane directly over a calibration antenna to collect deep depression angle data. The deep depression angle data necessary for calibration is p

A system for calibrating airborne direction finding antenna arrays eliminates the problem of trying to maintain a constant depression angle when flying an airplane directly over a calibration antenna to collect deep depression angle data. The deep depression angle data necessary for calibration is provided by data from a scale model of the aircraft having a direction-finding array which simulates the actual direction-finding array on the aircraft. In order to collect deep depression angle data, the model is pivoted through 360° while maintaining a controlled depression angle. Thus, it is unnecessary for calibration to actually fly a plane to attempt to obtain deep depression angle measurements. In the subject system, only a single depression set of data is required from the aircraft. Thus, with the exception of baseline shallow depression angle data from this plane, the calibration data comes strictly from the scale model, which is much more easily obtained. Optimization techniques are used in which a set of data is collected from the airplane at one shallow depression angle which is used with the data collected from the scale model at the same shallow depression angle to derive a complex set of optimized weights that are then applied to the data collected from the model at the remainder of the depression angles to obtain the appropriate database for use on this aircraft for direction finding. In so doing, the aircraft need only be flown to establish data at a relatively shallow depression angle which can be easily collected by an aircraft flying in circles or banana pattern at some distance from the calibration antenna.

대표청구항 ▼

1. In the system for calibrating an antenna array on an aircraft used for direction finding by flying the aircraft relative to a calibration antenna, a method for calibrating the array for deep depression angles comprising the steps of:providing a scale model of the aircraft with an antenna array ha

1. In the system for calibrating an antenna array on an aircraft used for direction finding by flying the aircraft relative to a calibration antenna, a method for calibrating the array for deep depression angles comprising the steps of:providing a scale model of the aircraft with an antenna array having antennas located at the same positions as on the aircraft;locating the scale model in a range at a distance from a calibrating antenna;collecting data from the scale model at various calibration frequencies, azimuths and depression angles relative to the calibrating antenna to provide model-derived data;flying the aircraft at a distance from the calibrating antenna so as to collect baseline data at a predetermined shallow depression angle, and,combining the baseline data at the shallow depression angle with model-derived data at both the shallow depression angle and other depression angles to create an array manifold for compensating output of the antenna array on the aircraft, whereby accurate direction finding can be achieved when the aircraft files directly over a source of electromagnetic radiation. 2. The method of claim 1, wherein aircraft collected data is collected at only one depression angle. 3. The method of claim 1, wherein the antenna manifold includes a set of complex weights used for correcting the output of the airborne array. 4. The method of claim 3, wherein the set of complex weights includes weights based on the shallow depression angle aircraft-derived data, and a set of weights based on the scale model-derived data, and wherein the last-mentioned sets of weights are compared, with the differences between the two sets being used to create the complete array manifold. 5. A method for minimizing the standoff distance that an aircraft having an airborne antenna direction finding array with a number of antennas at different positions on the aircraft must maintain relative to a source of electromagnetic radiation in order to achieve acceptable direction finding results, comprising the steps of:calibrating the airborne antenna array for deep depression angles by providing a scale model of the aircraft with an antenna array having antennas located at the same positions as on the aircraft; locating the scale model in a range at a distance from a calibrating antenna; collecting data from the scale model at various calibration frequencies, azimuths and depression angles relative to the calibrating antenna to provide model-derived data; flying the aircraft at a distance from the calibrating antenna so as to collect baseline data at a predetermined shallow depression angle, and combining the baseline data at the shallow depression angle with model-derived data at both the shallow depression angle and other depression angles to create an array manifold for compensating output of the antenna array on the aircraft, whereby accurate direction finding can be achieved when the aircraft files directly over a source of electromagnetic radiation.