Aircraft collision warning system

Claim 2

An aircraft position reporting system comprising an airborne VOR receiver for receiving bearing information signals from a ground station, an airborne DME receiver for receiving range information signals from said ground station, an airborne altimeter, resolver means connected to said VOR receiver for resolving said bearing signals into variable phase and reference phase sinewave components, a telemetry receiver for receiving position location messages from other aircraft, controller means receiving said variable phase output from said resolver means and said received position location messages from said telemetry receiver for generating an output signal representative of the bearing of the aircraft synchronized in time relation to the transmission of position location messages by said other aircraft, a telemetry transmitter, and encoder means connected to said telemetry transmitter and receiving inputs from said DME receiver and altitude transducer and receiving said controller output signal for encoding said bearing, and altitude information and controlling the operation of said telemetry transmitter for transmitting said encoded information as a position location message reporting the location of the aircraft with respect to said ground station.

Claim 3

The aircraft position reporting system as described in claim 1, further comprising decoder means connected to said telemetry receiver for receiving said position location messages of said other aircraft and receiving said reference phase output from said resolver for decoding said position location messages and generating signals representative of the bearing and range of said other aircraft with respect to said ground station, and further generating a signal representative of the altitude of said other aircraft, said controller circuit receiving said telemetry receiver output and generating an output signal for application to said encoder means representative of the bearing of the receiving aircraft only when no position location message is being received by said telemetry receiver.

Claim 4

The aircraft position reporting system as described in claim 2, wherein said controller means comprises squaring circuit means receiving said variable phase sinewave from said resolver and generating a square wave output, means for generating positive going pulses representative of the zero crossing in a positive going direction of said square wave. a counter receiving said positive going pulses for counting a predetermined number of said pulses and generating an output signal in response to said predetermined count, signal detector means receiving the output of said telemetry receiver for generatng a signal when no position location message is detected, and gating means receiving as inputs said positive going pulses, said counter signal output and said signal detector means output signal for generating an output signAl when said inputs occur simultaneously, the output signal of said gating means also being applied as a reset input to said counter.

Claim 5

The aircraft position reporting system as described in claim 2, further comprising coordinate computing means receiving the bearing and range signals of said other aircraft from said decoder and receiving the bearing signal of the receiving aircraft from said VOR resolver means and the range signal of the receiving aircraft from said DME receiver for generating output signals representative of the coordinate location of said other aircraft with respect to the receiving aircraft, and display means receiving said coordinate computing means output for visually displaying the location of said other aircraft with respect to the receiving aircraft.

Claim 6

The aircraft position reporting system as described in claim 2, further including visual display means, and circuit means receiving inputs of bearing and range of said other aircraft from said decoder means, bearing and range of the receiving aircraft from said VOR resolver and DME receiver, position location message start and end signals from said decoder means and a controller means output signal for generating signals applicable to said display means for displaying the location of said other aircraft and the receiving aircraft with respect to said ground station.

Claim 7

The aircraft position reporting system as described in claim 5, wherein said circuit means comprises a pair of ''''track-hold'''' circuit means, a VOR reference phase input from said VOR resolver applied to one of said ''''track-hold'''' circuit means, a 90* phase shift circuit receiving said VOR reference phase input and applying the phase shifted output to said other ''''track-hold'''' circuit means, a pair of multiplying circuits, each one of which receives the output of one of said ''''track-hold'''' circuit means, the outputs of said multiplying circuits being applied as inputs to said visual display means, a pair of electronic switching circuits, one of said circuits receiving the range signal of the receiving aircraft and applying its output to a second input of each of said multiplying circuits, another one of said switching circuits receiving the range signal of said other aircraft and applying its output to a second input of each of said multiplying circuits, said one switching circuit receiving as a switching input said controller means output signal, said another switching circuit receiving as a switching input said position location message end signal from said decoder means, first gate means receiving said output signal from said altitude comparator and said position location message end signal from said decoder and generating an output signal when both said altitude comparator and message end signals are present, second gate means receiving the output signal of said first gate means and said controller means output signal for generating an input signal if either of said signals are applied as inputs, and switching circuit means responsive to the output signal of said second gate means and said position location message start signal and connected to both said track-hold circuits means for switching said circuit means between the track and hold modes of operation.

Claim 8

The aircraft position reporting system as described in claim 6, wherein said circuit means further comprises an output from said switching circuit means applied as an input to said visual display means for unblanking said display means during a predetermined time interval during which the location information of said other aircraft or the receiving aircraft are applied to said display means.

Claim 9

The aircraft position reporting system as described in claim 2, wherein said controller means output signal occurs simultaneously with the occurrence of a zero crossing in a positive going direction of said variable phase sinewave component of saiD VOR signal, the occurrence of said controller signal in time relationship with said reference phase sinewave component being a measure of the bearing of the aircraft receiving said VOR signals.

Claim 10

The aircraft position reporting system as described in claim 2, wherein the synchronization of said encoded position location message is dependent on the phase relationship between said variable phase and reference phase sinewave components of said VOR signals.

Claim 11

The aircraft position reporting system as described in claim 2, wherein the initiation of a position location message as transmitted by said telemetry transmitter in time relation to said VOR signal reference phase sinewave component is a measure of the bearing of the aircraft transmitting said message.

Claim 14

The method as described in claim 11, comprising the additional steps of decoding said position location messages from said other aircraft into bearing, range and altitude information with respect to said ground station, generating signals representative of the bearing and range of said other aircraft with respect to said ground station, and generating a signal representative of the altitude of said other aircraft, said received encoded position location messages from said other aircraft being utilized in controlling generation of a signal representative of the bearing of the receiving aircraft only when no position location message is being received.

Claim 15

The method as described in claim 12, comprising the additional steps of generating signals representative of the coordinate location of said other aircraft with respect to the receiving aircraft in response to receipt of the bearing and range signals of said other aircraft and the bearing and range signals of the receiving aircraft, and visually displaying the location of said other aircraft with respect to the receiving aircraft.