Apparatus and method for an amplitude monopulse directional antenna

• US 5,191,349 A
• Filed: 08/08/1990
• Issued: 03/02/1993
• Est. Priority Date: 08/08/1990
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Smith, Mark D., Dinsmore, Bruce E.
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US07/564,430
• Time in Patent Office: 937 Days
• Field of Search: 343/789, 343/872, 343/705, 343/749, 343/751, 343/752, 343/826, 343/841, 343/853, 342/368
• US Class Current: 343/751
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 25/02 providing sum and difference patterns H01Q25/04 takes precedence
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

A directional antenna suitable for use with the transmission and reception of information related to the traffic alert and collision avoidance systems (TCAS) of a monitoring aircraft is disclosed. The directional antenna includes four monopole antennas positioned and electrically coupled in a manner to produce a radiation pattern having unique directional characteristics. The disclosed antenna can transmit radiation in a directional pattern. The antenna can also receive radiation from a transponder equipped intruder aircraft (i.e., an aircraft within a predetermined range of the monitoring aircraft). By comparing the amplitudes of the signals induced in the plurality of antenna elements by the received radiation, the bearing (direction) of the intruder aircraft relative to the monitoring aircraft can be determined. The antenna is fabricated to provide a reduced cross-sectional profile, for example by providing a folded monopole antenna structure, thereby reducing the antenna profile in aircraft applications.

Claims

1. A directional antenna comprising:

a dielectric material radome having an interior surface wherein predetermined first regions of said radome interior surface are shaped to form a multiplicity of folded monopole antenna elements wherein each of said folded monopole antenna elements comprises a feed portion, a grounded portion and a capacitive hat coupling said feed portion to said grounded portion, and wherein each of said folded monopole elements further comprises an electrically conductive coating covering each of said first regions, and wherein a predetermined second region of said radome interior surface is shaped to form a decoupling element wherein said decoupling element comprises an electrically conductive coating covering said second region;

a first ground plate coupled to said folded monopole antenna element grounded portions;

a multiplicity of electrical connectors for electrically coupling said antenna to electrical apparatus;

impedance matching devices coupled to each of said antenna element feed portions; and

a beam forming network electrically coupling said impedance matching devices to said electrical connectors, such that a predetermined directional radiation pattern is obtained when only one of said electrical connectors is energized in a transmit mode, and the shape of a received energy amplitude pattern for each of said connectors in a receive mode is the same as said predetermined radiation pattern, but displaced at a predetermined physical angle of rotation from those of the remaining connectors such that the direction from which a signal is received by said directional antenna may be uniquely determined by measuring only the relative amplitudes of the signals received at said electrical connectors, wherein said beam forming network includes resistances and capacitors for uniquely defining an electrical connector resistance to a DC input signal.

2. A directional antenna comprising:

a dielectric material radome having an interior surface wherein predetermined first regions of said radome interior surface are shaped to form a multiplicity of folded monopole antenna elements wherein each of said folded monopole antenna elements comprises a feed portion, a grounded portion and a capacitive hat coupling said feed portion to said grounded portion, and wherein each of said folded monopole elements further comprises an electrically conductive coating covering each of said first regions, and wherein a predetermined second region of said radome interior surface is shaped to form a decoupling element wherein said decoupling element comprises an electrically conductive coating covering said second region;

a first ground plate coupled to said folded monopole antenna element grounded portions;

a multiplicity of electrical connectors for electrically coupling said antenna to electrical apparatus;

impedance matching devices coupled to each of said antenna element feed portions; and

a beam forming network electrically coupling said impedance matching devices to said electrical connectors, such that a predetermined directional radiation pattern is obtained when only one of said electrical connectors is energized in a transmit mode, and the shape of a received energy amplitude pattern for each of said connectors in a receive mode is the same as said predetermined radiation pattern, but displaced at a predetermined physical angle of rotation from those of the remaining connectors such that the direction from which a signal is received by said directional antenna may be uniquely determined by measuring only the relative amplitudes of the signals received at said electrical connectors, wherein said antenna includes four monopole antenna elements and four electrical connectors.

3. The directional antenna of claim 2 wherein at least two of said antenna elements have a physical spacing less than 1/2 wavelength.