Antenna system having a plurality of fundamental resonances

• US 5,798,736 A
• Filed: 03/28/1995
• Issued: 08/25/1998
• Est. Priority Date: 03/28/1995
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Inventors: Hall, Edward A.
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US08/412,070
• Time in Patent Office: 1,246 Days
• Field of Search: 343/790-792, 343/722, 343/749, 343/752, 343/825, 343/828-830, 343/846
• US Class Current: 343/791
• CPC Class Codes: H01Q 5/321 within a radiating element or between connected radiating elements
• CPC Class Codes: H01Q 5/357 using a single feed point
• CPC Class Codes: H01Q 5/371 Branching current paths
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface

Abstract

An antenna which is adapted to have multiple fundamental resonances includes an outer conductor electrically connected to a feed network and having a generally tubular portion opening through one end to define an internal cavity therein. The antenna also includes an interior conductor electrically connected at a first end to a portion of the outer conductor within the internal cavity. The interior conductor extends through the opening defined in the outer conductor to a second end to thereby define an extended conductor portion which extends beyond the outer conductor. The antenna also includes decoupling means for electrically decoupling the extended conductor portion of the interior conductor from the antenna for signals having frequencies within the upper frequency band. In one embodiment, the internal conductor portion has a predetermined electrical length equal to an odd multiple of a quarter wavelength of a signal having a frequency in the upper frequency band of the antenna. Thus, the extended conductor portion is effectively electrically decoupled from the antenna for signals having frequencies within the upper frequency band.

Claims

1. An antenna adapted to resonate in a plurality of frequency bands without physically reconfiguring the antenna, wherein the antenna is adapted to resonate in a lower frequency band and at least one upper frequency band, the antenna comprising:

an outer conductor electrically conducted to a feed network, said outer conductor having a longitudinally extending tubular portion defining an internal cavity therein; and

a plurality of interior conductors that are each directly connected and interconnected at their respective first ends to a portion of said outer conductor, wherein said plurality of interconnected interior conductors are nested to thereby define an outermost conductor and a plurality of inner conductors, and wherein each inner conductor has a second end which extends longitudinally beyond an adjacent interior conductor which is positioned in an at least partially surrounding relationship thereto such that each inner conductor defines an extended conductor portion which extends longitudinally beyond the at least partially surrounding adjacent interior conductor;

wherein the extended conductor portion of at least one of said interior conductors has a predetermined electrical length equal to an odd multiple of a quarter wavelength of a signal having a frequency in each upper frequency band of the antenna such that the extended conductor portion of at least one of said interior conductors is electrically decoupled from the antenna for signals having frequencies within each of the upper frequency bands.

2. An antenna according to claim 1 further comprising frequency band shifting means for controllably shifting at least one frequency band of the antenna.

3. An antenna according to claim 1 further comprising length controlling means for controlling the electrical lengths of an internal conductor portion of interior conductors.

4. An antenna according to claim 3 wherein said length controlling means comprises an annular conducive disk electrically connected to the second end of said outer conductor.

5. An antenna according to claim 3 wherein said length controlling means comprises a conducive disk electrically connected to the second end of at least one interior conductor.

6. An antenna according to claim 1 further comprising impedance adjusting means for controllably adjusting the impedance of the antenna such that the frequency bands are broadened.

7. An antenna adapted to resonate in a plurality of frequency bands, the antenna comprising:

an outer conductor electrically connected to a feed network, said outer conductor having a longitudinally extending tubular portion defining an internal cavity therein;

a plurality of interior conductors electrically connected at their respective first ends to a portion of said outer conductor, wherein said plurality of interior conductors are nested to thereby define an outermost conductor and a plurality of inner conductors, and wherein each inner conductor has a second end which extends longitudinally beyond an adjacent interior conductor which is positioned in an at least partially surrounding relationship thereto such that each inner conductor portion which extends longitudinally beyond the at least partially surrounding adjacent interior conductor; and

length controlling means for controlling the electrical lengths of the internal conductor portion of said interior conductors, wherein said length controlling means is selected from the group consisting of a reactive impedance element disposed between the first end of said interior conductor and said outer conductor, a reactive impedance element disposed between the respective first end of said outer conductor and a ground plane, and a reactive impedance element disposed between the respective first end of said interior conductor and a ground plane;

wherein the extended conductor portion of at least one of said interior conductors has a predetermined electrical length equal to an odd multiple of a quarter wavelength of a signal having a frequency in each upper frequency band of the antenna such that the extended conductor portion of at least one of said interior conductors is electrically decoupled from the antenna for signals having frequencies within each of the upper frequency bands.

8. An antenna adapted to resonate in a plurality of frequency bands including a predetermined low frequency band, a predetermined high frequency band and at least one intermediate frequency band between the low and high frequency bands without physically reconfiguring the antenna, the antenna comprising:

a base radiating conductor electrically connected to a feed network, wherein said base radiating conductor has a longitudinally extending tubular portion defining an internal cavity therein, and wherein said base radiating conductor is adapted to resonate in each of the plurality of frequency bands;

a plurality of inner conductors that are each directly connected at their respective first ends to said base radiating conductor and extending through at least a portion of the internal cavity;

at least one intermediate radiating element spaced from said base radiating conductor, each intermediate radiating element being connected to a respective inner conductor and defining a longitudinally extending bore therethrough, wherein each intermediate radiating element is adapted to resonate within each frequency band from the predetermined low frequency band to a predetermined maximum intermediate frequency band, and wherein at least one inner conductor extends through the bore of said intermediate radiating element; and

a termination radiating conductor spaced from said base radiating conductor and each intermediate radiating element, said termination radiating conductor being connected to a respective inner conductor and adapted to resonate in the low frequency band;

wherein each inner conductor extends beyond said base radiating conductor to thereby define a respective extended conductor portion, and wherein the extended conductor portion of at least one of said inner conductors has a predetermined electrical length equal to an odd multiple of a quarter wavelength of a signal having a frequency in each of the intermediate and high frequency bands of the antenna such that each respective intermediate radiating element is electrically decoupled from the antenna for signals having frequencies within a frequency band in which the antenna is adapted to resonate and which are higher than the predetermined maximum frequency band in which the respective intermediate radiating element resonates, and such that said termination radiating conductor is electrically decoupled from the antenna for signals within a frequency band in which the antenna is adapted to resonate and which are higher than the low frequency band.

9. An antenna according to claim 8 comprising a twin-axial cable having an annular outer conductor and a first and second inner conductors extending longitudinally therethrough, wherein said annular outer conductor comprises said base radiating conductor, and wherein said first and second inner conductors comprise said plurality of inner conductors.

10. An antenna according to claim 9 wherein said first inner conductor is connected to said intermediate radiating element, and wherein said second inner conductor extends longitudinally through the bore of said intermediate radiating element and is connected to said termination radiating conductor.