Radio Altimeter for Small Aircraft Landing

The project was designed to create an accurate radio altimeter with dual-channel homodyne receiver intended as a landing aid for small general-aviation aircraft equipped with synthesized-voice human interface.

Short-range FM radars operating in the 4.2-4.4GHz frequency band are usually designed for aviation radio altimeters where their main use is the instrumented approaches and landings of large commercial aircraft. The resolution and accuracy of aviation altimeters is usually limited to a few feet due to the limited available bandwidth of 200MHZ in the 4.3GHz frequency band.

Developing highly-reliable radio altimeters is the design efforts which will allow parallel operation of two or three instruments on the same aircraft. A separate transmit and receive antennas is contained in most aviation radio altimeters although considerable efforts were invested into developing single-antenna radio altimeter.

The aviation radio altimeters are short-range, low-power, continuous-wave radars that generally require two separate transmit and receive antennas. The radio-wave propagation delay is usually too short to switch a single antenna between the transmitter and the receiver. The receiving antenna of a radio altimeter should only receive the reflected signal from the runway and avoid signal coming directly from the transmitting antenna.

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