TCAS bearing estimation receiver using a 4 element antenna
First Claim
1. A direction finding antenna system for determining the relative bearing of an intruder aircraft from a protected aircraft in conjunction with a Traffic Alert Collision Avoidance System (TCAS), the intruder aircraft being equipped to transmit signals received by said antenna system, comprisingfirst and third spaced apart antennas mounted aboard the protected aircraft;
- first and third receivers aboard the protected aircraft for amplifying, converting and limiting the signals received by said first and third antennas;
first switching means at the inputs to said first and third receivers for interchangeably applying the signals received by said first and third antennas to the inputs of said first and third receivers;
second switching means at the outputs of said first and third receivers;
a first phase detector having a reference phase input and a variable phase input,said inputs to said first phase detector being connected to said second switching means,said second switching means operating in synchronism with said first switching means so that in a first position of said first switching means signals from said first and third antennas are applied to said first and third receivers, respectively, and in a first position of said second switching means the outputs of said first and third receivers are applied respectively to said reference phase and said variable phase inputs to said first phase detector and in a second position said first switching means signals from said first and third antennas are applied to the inputs of said third and first receivers, respectively, in a second position of second switching means the outputs of said third receiver and said first receiver are applied respectively to said reference phase and variable phase inputs to said first phase detector; and
first means for processing the outputs of said first phase detector obtained in alternate operations of said first and second switching means to eliminate the errors therein caused by a difference between the phase delays of signals passing through said first and third receivers, the result of said processing means being a first quantity related to the relative bearing to the intruder aircraft from the protected aircraft.
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Accused Products
Abstract
A direction finding receiving system for use on a protected aircraft in which a signal from an ATCRABS transponder on an intruder aircraft is received has been described incorporating a four element interferometer type antenna array, reversing switches, individual receivers, a phase detector and a processor for processing the outputs of the phase detector. The invention overcomes the problem of correcting for the difference in phase delay of signals passing through the receivers.
85 Citations
16 Claims
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1. A direction finding antenna system for determining the relative bearing of an intruder aircraft from a protected aircraft in conjunction with a Traffic Alert Collision Avoidance System (TCAS), the intruder aircraft being equipped to transmit signals received by said antenna system, comprising
first and third spaced apart antennas mounted aboard the protected aircraft; -
first and third receivers aboard the protected aircraft for amplifying, converting and limiting the signals received by said first and third antennas; first switching means at the inputs to said first and third receivers for interchangeably applying the signals received by said first and third antennas to the inputs of said first and third receivers; second switching means at the outputs of said first and third receivers; a first phase detector having a reference phase input and a variable phase input, said inputs to said first phase detector being connected to said second switching means, said second switching means operating in synchronism with said first switching means so that in a first position of said first switching means signals from said first and third antennas are applied to said first and third receivers, respectively, and in a first position of said second switching means the outputs of said first and third receivers are applied respectively to said reference phase and said variable phase inputs to said first phase detector and in a second position said first switching means signals from said first and third antennas are applied to the inputs of said third and first receivers, respectively, in a second position of second switching means the outputs of said third receiver and said first receiver are applied respectively to said reference phase and variable phase inputs to said first phase detector; and first means for processing the outputs of said first phase detector obtained in alternate operations of said first and second switching means to eliminate the errors therein caused by a difference between the phase delays of signals passing through said first and third receivers, the result of said processing means being a first quantity related to the relative bearing to the intruder aircraft from the protected aircraft. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification