High-isolation collocated antenna systems

• US 5,264,862 A
• Filed: 12/10/1991
• Issued: 11/23/1993
• Est. Priority Date: 12/10/1991
• Status: Expired due to Term

• Current Assignee: Hazeltine Corporation (BAE Systems Plc)
• Original Assignee: Hazeltine Corporation (BAE Systems Plc)
• Inventors: Kumpfbeck, Richard J.
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): BROWN, PETER T
• Application Number:
  US07/804,444
• Time in Patent Office: 714 Days
• Field of Search: 343/725, 343/727, 343/844, 343/726, 343/728, 343/799, 343/800, 343/820, 343/846, 343/848, 343/850, 343/853, 343/878, 343/888, 343/844, 333/120
• US Class Current: 343/853
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 9/18 Vertical disposition of the antenna
• CPC Class Codes: H01Q 9/34 Mast, tower, or like self-supporting or stay-supported antennas

Abstract

The need to widely separate antennas (e.g., transmit and receive antennas) for VHF radio and other applications is avoided by high-isolation antenna systems with collocated antennas and cancellation of intercoupled signals. A transmit antenna in the form of a vertical dipole can be mounted atop a mast with a receive antenna comprising a multi-element array of vertical dipoles supported on the same mast below the transmit antenna. Opposing pairs of the dipole receiving elements are located in 180° positions on opposite sides of the mast so as to be symmetrically located in the omnidirectional antenna pattern of the transmit antenna. Resulting intercoupling to the receive dipoles is equal and in-phase and is cancelled out by the antiphase combining of signals from the dipoles of each pair of the receive dipoles. Reciprocally, cancellation of coupled signals is achieved with reversal of the receive and transmit functions of the respective collocated antennas. Dipole and monopole high-isolation antenna systems can also be configured on yardarms and ground planes.

Claims

1. A high-isolation collocated antenna system, comprising:

a first antenna providing an azimuth radiation pattern which is substantially omnidirectional with areas of radially symmetrical signal strength;

a second antenna, displaced in elevation from said first antenna, including two antenna element pairs with each said pair comprising;

first and second vertical dipole elements laterally spaced and substantially symmetrically positioned in areas of radially symmetrical signal strength of said first antenna;

a first signal conductor for feeding signals from an upper arm of said first vertical dipole element; and

a second signal conductor for feeding signals from a lower arm of said second vertical dipole element;

signal cancelling means, coupled to said second antenna, including two junction points each of which directly connects said first and second signal conductors of only one of said two antenna element pairs, for substantially cancelling signals coupled to each said antenna element pair from said first antenna; and

signal combining means, coupled to said two junction points of said signal cancelling means, comprising directional coupler means for coupling together signals from said junction points to provide a first output signal representing a clockwise phased combination of signal portions from each said dipole element of said second antenna and a second output signal representing a counterclockwise phased combination of signal portions from each said dipole element of said second antenna.

2. A high-isolation collocated antenna system, comprising:

a first antenna providing an azimuth radiation pattern which is substantially omnidirectional with areas of radially symmetrical signal strength;

a second antenna, displaced in elevation from said first antenna, including two antenna element pairs with each said pair comprising;

first and second vertical dipole elements laterally spaced and substantially symmetrically positioned in areas of radially symmetrical signal strength of said first antenna;

a first signal conductor for feeding signals from an upper arm of said first vertical dipole element; and

a second signal conductor for feeding signals from a lower arm of said second vertical dipole element;

signal cancelling means, coupled to said second antenna, including two junction points each of which directly connects said first and second signal conductors of only one of said two antenna element pairs, for substantially cancelling signals coupled to each said antenna element pair from said first antenna; and

signal combining means, coupled to said two junction points of said signal cancelling means, for combining portions of signals received by each said antenna element pair to provide output signals including signal portions from all antenna elements of said second antenna for providing a first output signal representative of an azimuth antenna pattern with 360°

progressive clockwise phase variation and a second output signal representative of an azimuth antenna pattern with 360°

progressive counterclockwise phase variation;

whereby said first and second output signals may be independently coupled to separate receivers for signal processing.

3. An antenna system as in claim 2, additionally comprising means for coupling a selected portion of signals from said first antenna for inclusion in said output signals to cancel signals non-symmetrically coupled from said first antenna to said second antenna as a result of nonuniformities in radiation pattern signal strength, whereby compensation may be provided for multi-path reflections caused by objects within the antenna pattern of said antennas.

4. A high-isolation collocated antenna system, comprising:

a first vertical dipole antenna providing an azimuth radiation pattern which is substantially omnidirectional with areas of radially symmetrical signal strength;

a second antenna, displaced in elevation from said first antenna, including two antenna element pairs with each said pair comprising two vertical dipole elements laterally spaced and substantially symmetrically positioned in areas of radially symmetrical signal strength of said first antenna;

signal cancelling means, coupled to said second antenna, for combining signals received by said two vertical dipole elements of each said antenna element pair in an out-of-phase relationship for substantially cancelling signals coupled to each said antenna element pair from said first antenna;

signal combining means, coupled to said signal cancelling means, for combining portions of signals received by each said antenna element pair to provide output signals including signal portions from all antenna elements of said second antenna; and

means for coupling a selected portion of signals from said first antenna for inclusion in said output signals to cancel signals non-symmetrically coupled from said first antenna to said second antenna as a result of nonuniformities in radiation pattern signal strength, whereby compensation may be provided for multi-path reflections caused by objects within the antenna pattern of said antennas.

5. A high-isolation collocated antenna system, comprising:

a first vertical dipole antenna providing an azimuth radiation pattern which is substantially omnidirectional with areas of radially symmetrical signal strength;

a second antenna including two vertical dipole elements laterally spaced and substantially symmetrically positioned in areas of radially symmetrical signal strength of said first antenna;

signal cancelling means, coupled to said second antenna, for forming output signals by combining signals received by said two vertical dipole elements in an out-of-phase relationship for substantially cancelling signals coupled to said dipole elements from said first antenna; and

means for coupling a selected portion of signals from said first antenna for inclusion in said output signals to cancel signals non-symmetrically coupled from said first antenna to said second antenna as a result of nonuniformities in radiation pattern signal strength, whereby compensation may be provided for multi-path reflections caused by objects within the antenna pattern of said antennas.

6. A high-isolation transmit/receive antenna system, comprising:

a first antenna providing an azimuth radiation pattern having areas of radially symmetrical signal strength;

a second antenna including first and second radiating elements substantially symmetrically positioned in first and second areas of radially symmetrical signal strength of said first antenna, a first signal conductor for feeding signals of a first phase from said first radiating element, and a second signal conductor for feeding signals of opposite phase, relative to said first phase, from said second radiating element;

signal cancelling means, coupled to said second antenna, including a junction point directly connecting said first and second signal conductors to directly combine, in an out-of-phase relationship, signals associated with said two radiating elements, for substantially cancelling signals coupled between said first and second antennas to provide output signals; and

means for coupling a selected portion of signals from said first antenna for inclusion in said output signals to cancel signals non-symmetrically coupled from said first antenna to said second antenna as a result of nonuniformities in radiation pattern signal strength, whereby compensation may be provided for multi-path refections caused by objects within the antenna pattern of said antennas.

7. A high-isolation collocated antenna system, comprising:

a first antenna providing an azimuth radiation pattern which is substantially omnidirectional with areas of radially symmetrical signal strength;

a second antenna, displaced in elevation form said first antenna, including two antenna element pairs with each said pair comprising;

first and second vertical elements laterally spaced and substantially symmetrically positioned in areas of radially symmetrical signal strength of said first antenna;

a first signal conductor for feeding signals from said first vertical element; and

a second signal conductor for feeding signals from said second vertical element;

a horizontally extending member upon which said first antenna is mounted so as to extend upward and upon which said second antenna is mounted below said first antenna so as to extend downward from said member, substantially co-axially with said first antenna;

signal cancelling means, coupled to said second antenna, including two junction points each of which directly connects said first and second signal conductors of only one of said two antenna element pairs, for combining said signals from said first and second vertical elements in an out-of-phase relationship for substantially cancelling signals coupled to each said antenna element pair from said first antenna; and

signal combining means, coupled to said two junction points of said signal cancelling means, for combining portions of signals received by each aid antenna element pair to provide output signals including signal portions from all antenna elements of said second antenna for providing a first output signal representative of an azimuth antenna pattern with 360°

progressive clockwise phase variation and a second output signal representative of an azimuth antenna pattern with 360°

progressive counterclockwise phase variation;

whereby said first and second output signals may be independently coupled to separate receivers for signals processing.

8. An antenna system as in claim 7, wherein said horizontally extending member is a ground plane section, said first antenna is a vertical monopole mounted above said ground plane section and said second antenna comprises four vertical monopoles mounted below said ground plane section.