When visibility is poor, instrument landing systems (ILS) create a "picture" of the runway for pilots so that they can bring a plane down more safely. But because most systems involve extensive and expensive equipment installation on the ground and in the aircraft, only the busiest airports are equipped. A new, low-cost instrument landing system promises to make ILS more affordable for more airports.
The landing system analyzes RF signals and uses measurements of aircraft attitude and altitude to create the runway image that the pilot can view on display.
Based on monolithic millimeter-wave integrated circuits, the system uses a single, fixed, on-board multi-beam antenna system, called a radiometer, and six RF beacons on the ground. Four beacons outline the runway, and two more widely spaced apart provide a more accurate indication of range.
Since the system uses a minimal amount of equipment, it doesn't produce a "camera-like" picture. However, overlapping RF beams provide an accurate image of the runway relative to the aircraft. Each ground-based emitter uses an amplitude-modulated frequency. Narrow, millimeter-wave-receiving signals from the antenna pick up the RF transmission. Then conversion circuitry converts them into video signals that can be segregated by a fast Fourier transform processor. Another application of the millimeter-wave technology is in a fully populated focal plane array.
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