Radome aberration correcting system
View Patent ↗A system for correcting the effect of radome aberration on line-of-sight signals indicating target position. The aberration is in fact dependent upon both operating frequency and ‘angle-of-look’ and the essence of the present invention is to separate the corrections appropriate to each of these factors. The apparent line-of-sight signals are subjected to a frequency dependent amplification the result being used to address a store of error correction data. The apparent line of sight signals are also used to address a second store of error correction data and the two sets of correction data are added into the apparent line-of-sight signals to give true line-of-sight.
1. A radome aberration correcting system comprising a directional antenna system for tracking a target, a radome enclosing said antenna system, said radome having a profile discontinuity, means for deriving information from the antenna system as to the apparent line of sight of a target, said apparent line of sight having two error components, a first of said error components arising from the presence of said discontinuity and being frequency dependent, and the second of said error components arising from basic refraction and being dependent upon the angle off-boresight of the target line of sight and independent of frequency, first storage means containing data representing a range of magnitude of said first error component predetermined empirically, second storage means containing data representing a range of magnitude of said second error component predetermined empirically, means for providing a first addressing signal to said first storage means, said first addressing signal being a product function of the operating frequency and the angle off-boresight of the apparent line of sight, means for correcting the apparent line of sight in dependence upon the data in said first storage means accessed by said first addressing signal, means for applying a signal representing the apparent line of sight as a second addressing signal to said second storage means, and means for correcting the apparent line of sight in dependence upon the data in said second storage means accessed by said second addressing signal.
2. A system according to claim 1 , wherein said means for providing a first addressing signal comprises a gain-controlled amplifier to the input of which is applied a signal representing apparent line of sight information, and an amplifying circuit producing a signal whose magnitude varies with operating frequency, the amplifying circuit signal being applied as a gain control signal for said amplifier, the output of which provides said first addressing signal.
3. A radome aberration correcting system comprising two parallel systems each according to claim 2 , and providing separate corrections of azimuth and elevation information.
4. A radome aberration correcting system comprising two parallel systems each according to claim 1 , and providing separate corrections of azimuth and elevation information.