Transponder having directional antennas

A method for acquiring Air Traffic Control Radar Beacon System format signals and transmitting directional reply signals in response, the method comprising the steps of:

• using a first and second directional antennas to independently acquire an Air Traffic Control Radar Beacon System format interrogation signal at each of first and second directional antennas;
• alternately configuring a switch in a first receive mode coupling said first directional antenna to a transponder receiver and in a second receive mode coupling said second antenna to said transponder receiver;
• receiving said interrogation signal using said transponder receiver;
• determining a vertical directional source of said received interrogation signal;
• determining an azimuthal directional source of said received interrogation signal;
• generating an Air Traffic Control Radar Beacon System format reply signal;
• configuring said switch to transmit said reply signal in a directional radiation pattern toward said determined vertical and said determined azimuthal directional source of said received interrogation signal;
• and
• transmitting said directional radiation pattern toward said determined vertical and said determined azimuthal directional source of said received interrogation signal.

An airborne directional transponder device for detecting and responding to Air Traffic Control Radar Beacon System format interrogation signals using a pair of directional antennas, the device comprising:

• first and second directional antennas;
• a switch coupled to of each said first and second antenna;
• a transponder receiver coupled to said switch for receiving and decoding an interrogation signal, said receiver including a circuit for determining a relative directional source of a received and decoded interrogation signal;
• a transmitter coupled to said switch for transmitting a signal in response to said received and decoded interrogation signal;
• and
• a transmit and switch control circuit coupled to said switch for coupling said switch to a predetermined one of said first and second directional antennas for transmitting said response signal toward said relative directional source of said received and decoded interrogation signal.

An directional transponder device for monitoring, detecting and responding to Air Traffic Control Radar Beacon System format interrogation signals using a pair of directional antennas, each antenna having a plurality of antenna elements, the device comprising:

• first and second directional antennas mounted on opposing surfaces of an aircraft;
• a switch coupled to each of said antenna elements of each said first and second antenna;
• a transponder receiver coupled to said switch for monitoring, receiving and decoding an Air Traffic Control Radar Beacon System format interrogation signal, said receiver including a circuit for determining a relative vertical directional source and a relative azimuthal directional source of a received Air Traffic Control Radar Beacon System format interrogation signal;
• a transponder transmitter coupled to said switch for transmitting an Air Traffic Control Radar Beacon System format reply signal in response to said received and decoded Air Traffic Control Radar Beacon System format interrogation signal;
• and
• a transmit and switch control circuit responsive to a signal generated by said transponder transmitter, said transmit and switch control circuit coupled to said switch for coupling said switch to a predetermined one of said antenna elements of a predetermined one of said first and second directional antennas for transmitting said reply signal toward said relative vertical and azimuthal directional source of said received and decoded Air Traffic Control Radar Beacon System format interrogation signal.