Mode a/c/s transponder positioning system and method for using the same

A system for determining a location of an intruder in airspace, comprising:

• an antenna one, spaced apart along a baseline at a baseline distance from an antenna two at a station two, the antenna two being spaced apart at a sub-wavelength distance from an antenna three, the antenna three being disposed off the baseline;
• the antenna one being configured to send an interrogation signal;
• the antenna one, the antenna two and the antenna three being configured to receive a reply signal from the intruder, in response to the interrogation signal;
• the system being further configured to:
• determine two possible locations of the intruder, using the reply signal of the intruder, received at the antenna one and at the antenna two, respectively;
• and
• discriminate between the two possible locations of the intruder, using the reply signal received at the antenna two and at the antenna three, thereby determining the location of the intruder, comprising:
• measuring a first phase of the reply signal received by the antenna two, and a second phase of the reply signal received by the antenna three, and determine a phase difference between the first phase and the second phase.

In a system for determining a location of an intruder in airspace, comprising an antenna one at a station one, spaced apart along a baseline at a baseline distance from an antenna two at a station two, the antenna two being spaced apart at a sub-wavelength distance from an antenna three at the station two, the antenna three being disposed off the baseline;

• the antenna one sending an interrogation signal;
• the antenna one, the antenna two and the antenna three receiving a reply signal from the intruder, respectively, in response to the interrogation signal:
• a computer memory device having computer readable instructions stored thereon for execution by a processor, causing the processor to:
• determine two possible locations of the intruder, using the reply signal of the intruder, received at the antenna one and at the antenna two, respectively, comprising:
• measuring a first transit time and a second sum time representing times of transit of the reply signal from the intruder to the station one, and the sum time the signal transmit from the station one to the intruder and from the intruder to the station two, respectively;
• determining a first distance from the intruder to the antenna one, and a second sum distance from the antenna one to the intruder and from the intruder to the antenna two, by using the first transit time and the second sum time, respectively;
• and
• determining the two possible locations of the intruder, each location being at intersection of a circle with a radius equal to the first distance and an ellipse formed using the antenna one and the antenna two as two focal points;
• and
• discriminate between the two possible locations of the intruder, using the reply signal received at the antenna two and at the antenna three, thereby determining the location of the intruder.

A method of determining a location of an intruder in airspace, comprising:

• sending an interrogation signal from an antenna one at a station one, spaced apart along a baseline at a baseline distance from an antenna two at a station two, and the antenna two being spaced apart at a sub-wavelength distance from an antenna three at the station two, the antenna three being disposed off the baseline;
• receiving a reply signal from the intruder at the antenna one, at the antenna two and at the antenna three, in response to the interrogation signal;
• determining two possible locations of the intruder, using the reply signal of the intruder, received at the antenna one and at the antenna two, respectively, comprising:
• measuring a first transit time and a second sum time representing times of transit of the reply signal from the intruder to the station one, and the sum time the signal transmits from the station one to the intruder and from the intruder to the station two, respectively;
• determining a first distance from the intruder to the antenna one, and a second sum distance from the antenna one to the intruder and from the intruder to the antenna two, by using the first transit time and the second sum time, respectively;
• and
• determining the two possible locations of the intruder, each location being at intersection of a circle with radius equal to the first distance and an ellipse formed using the antenna one and the antenna two as two focal points;
• and
• discriminating between the two possible locations of the intruder, using the reply signal received at the antenna two and at the antenna three, thereby determining the location of the intruder.

A method of determining a location of an intruder in airspace, comprising:

• sending an interrogation signal from an antenna one, spaced apart at a baseline distance from an antenna two, along a baseline, and the antenna two being spaced apart at an sub-wavelength distance from an antenna three, the antenna three being disposed off the baseline;
• receiving a reply signal from the intruder at the antenna one, at the antenna two and at the antenna three, in response to the interrogation signal;
• determining two possible locations of the intruder, using the reply signal of the intruder, received at the antenna one and at the antenna two, respectively;
• and
• discriminating between the two possible locations of the intruder, using the reply signal received at the antenna two and at the antenna three, thereby determining the location of the intruder, wherein the method further comprises:
• measuring a first phase of the reply signal received by the antenna two, and a second phase of the reply signal received by the antenna three, and determining a phase difference between the first phase and the second phase.

In a system for determining a location of an intruder in airspace, comprising an antenna one, spaced apart at a baseline distance from an antenna two, along a baseline, and the antenna two being spaced apart at a sub-wavelength distance from an antenna three, the antenna three being disposed off the baseline;

• the antenna one sending an interrogation signal;
• the antenna one, the antenna two and the antenna three receiving a reply signal from the intruder, in response to the interrogation signal:
• a computer memory device having computer readable instructions stored thereon for execution by a processor, causing the processor to:
• determine two possible locations of the intruder, using the reply signal of the intruder, received at the antenna one and at the antenna two, respectively;
• and
• discriminate between the two possible locations of the intruder, using the reply signal received at the antenna two and at the antenna three, comprising measuring a first phase of the reply signal received by the antenna two, and a second phase of the reply signal received by the antenna three, and determining a phase difference between the first phase and the second phase, thereby determining the location of the intruder.