RADIO FREQUENCY ANTENNA SYSTEM

• US 3,790,943 A
• Filed: 02/09/1972
• Issued: 02/05/1974
• Est. Priority Date: 02/09/1972
• Status: Expired due to Term

• Current Assignee: Dean S. Thornberg, Sidney Pickles
• Original Assignee: Dean S. Thornberg, Sidney Pickles
• Inventors: Pickles, Sidney, Thornberg, Dean S.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Buczinski, S. C.
• Application Number:
  US05/224,783
• Time in Patent Office: 727 Days
• Field of Search: 343/16R,833,761,872,791
• US Class Current: 342/399
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: H01Q 3/14 for varying the relative position of primary active element and a refracting or diffracting device

Abstract

Tactical radio navigation systems provide distance measuring information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, the system also provides bearing and identification information. The transponder receives pairs of interrogation pulses which are decoded into a single pulse for operation of a reply transmitter. Bearing, distance and identification determining signals are generated by the reply transmitter and its antennas. A single antenna functions to both receive the interrogation pulses and radiate the position determining signals. To provide the required bearing information, the antenna radiates pulses from a central antenna array that is stationary with respect to a support housing. These pulses are modulated at a 15 Hz frequency by parasitic elements rotating around the stationary central array. Further modulation of the transmitted pulses at a 135 Hz frequency, superimposed on the 15 Hz frequency, is provided by additional parasitic elements also rotating about the central antenna array. Both the low band frequency parasitic elements and the high band frequency parasitic elements have a configuration to provide improved radiation from the antenna above the horizontal. Also to improve the antenna radiation pattern, the 135 Hz parasitic elements are positioned on a rotating drum of a dielectric material, such as fiberglass. To still further improve the amount of radiation energy above the horizontal reference, radio frequency chokes are coupled to the central antenna array in the feed line from the signal transmitter.

Claims

1. An antenna system for obtaining uptilt of radiation above the horizon and energized from a radio frequency source, comprising in combination:

a central antenna array including;

a. a coaxial transmission line connected to the radio frequency source and having a feed point, b. a first energy radiator coupled to said feed point along the transmission line to have a current therein with a lagging phase relationship with reference to a current in the feed point, and c. a second energy radiator coupled to said feed point along the transmission line to have a current therein with a leading phase relationship with reference to current in a feed point and said first radiator, and at least one radio frequency choke positioned along the transmission line of said antenna array in a spaced relationship with the second radiator to produce a leading current with reference to a current in the second radiator along said transmission line between the second radiator and said choke to uptilt the radiation pattern from the antenna system.

2. A radio frequency antenna system as set forth in claim 1 including a cavity at the end of said central antenna array filled with an energy absorbing material.

3. An antenna system for obtaining uptilt of radiation above the horizon and energized from a radio frequency source, comprising in combination:

a support including a drive motoR, a central antenna array mounted to the support and including;

a. a feed point connected to the radio frequency source, b. a first energy radiator coupled to said feed point to have a current therein with a lagging phase relationship with reference to a current in the feed point, and c. a second energy radiator coupled to said feed point to have a current therein with a leading phase relationship with reference to current in the feed point and said first radiator, a plurality of spaced lagging current reflectors positioned radially from the first radiator and responsive to energy therefrom to generate a current therein with a lagging phase relationship with reference to a current in said first radiator and said feed point, a plurality of spaced leading current reflectors positioned in alignment with the lagging current reflectors and radially from the second radiator and responsive to energy therefrom to generate a current therein with a leading phase relationship with reference to the current in said second radiator and said feed point, and a support drum of a dielectric material with one end coupled to the drive motor and the lagging and leading current reflectors attached to the wall of said drum.

4. A radio frequency antenna system as set forth in claim 3 wherein said drum of dielectric material further includes spacers mounted to said drum with a filament stretched between pairs of said spacers and the leading and lagging current reflectors attached to said filaments.

5. An antenna system as set forth in claim 3 wherein said drum has a diameter substantially larger than a maximum dimension of said support to minimize radiation reflected from said support to said spaced current reflectors.

6. An antenna system as set forth in claim 3 including a coaxial transmission line with the radiating feed point as a part thereof and said radiators positioned along the transmission line.

7. An antenna system as set forth in claim 6 including at least one radio frequency choke coupled to the transmission line of said antenna array in a spaced relationship with the second radiator to produce a leading current with reference to a current in the second radiator along said transmission line between the second radiator and said choke.

8. An antenna system for obtaining uptilt of radiation above the horizon and energized from a radio frequency source, comprising in combination:

a central antenna array including;

a. a feed point connected to the radio frequency source, b. a first energy radiator coupled to said feed point to have a current therein with a lagging phase relationship with reference to a current in the feed point, and c. a second energy radiator coupled to said feed point to have a current therein with a leading phase relationship with reference to current in the feed point and said first radiator, a plurality of spaced lagging current reflectors positioned radially from the first radiator and responsive to energy therefrom to generate a current therein with a lagging phase relationship with reference to a current in said first radiator and said feed point, and a plurality of spaced leading current reflectors positioned along the same radial as the lagging current reflectors and radially from the second radiator and responsive to energy therefrom to generate a current therein with a leading phase relationship with reference to the current in said second radiator and said feed point.

9. A radio frequency antenna system as set forth in claim 8 including support means including a drum of a dielectric material with one end coupled to a drive motor and the leading and lagging current reflectors attached to the walls of said drum.

10. A radio frequency antenna system as set forth in claim 8 wherein the lagging current reflectors have an impedance to cause current flow to be retarded with respect to current flow in the leading current reflectors when both are excited simultaneously.

11. A radio Frequency antenna system as set forth in claim 8 wherein the lagging current reflectors are longer than a half wavelength of the electromagnetic wave radiating from said central antenna array and the leading current reflectors are shorter than a half wavelength.

12. An antenna system as set forth in claim 8 including a coaxial transmission line with the radiating feed point as a part thereof and said radiators positioned along the transmission line.

13. An antenna system as set forth in claim 12 including at least one radio frequency choke positioned along the transmission line of said antenna array in a spaced relationship with the second radiator to produce a leading current with reference to a current in the second radiator along said transmission line between the second radiator and said choke.

14. An antenna system as set forth in claim 8 wherein said first energy radiator and said second energy radiator are half wavelength dipoles.

15. A radio frequency antenna system for obtaining uptilt of radiation above a reference line, comprising in combination:

a support including a drive motor, a central antenna array of two stacked omni-directional dipole radiators mounted to said support to be fixed in position with respect thereto along a coaxial transmission line having a radiating feed point energizing one dipole to have a leading current with respect to the feed point and the second dipole to have a lagging current with espect to the feed point to radiate a pattern above a reference line, at least one radio frequency choke positioned along the transmission line of said antenna array at the support and in proximity to one of said dipoles to reflect radiation along the transmission line from said omni-directional antenna to further uptilt the radiation pattern from said central antenna array, a plurality of spaced, parasitic reflectors radially positioned from said central antenna array, and support means for positioning said plurality of parasitic reflectors and coupled to the drive motor of said support and rotated thereby to produce a rotation of said reflectors around the central array for modulating electromagnetic waves radiated therefrom.

16. A radio frequency antenna system as set forth in claim 15 wherein said support means includes a drum of a dielectric material with one end coupled to the drive motor and the parasitic antenna element attached to the wall of said drum.

17. A radio frequency antenna system as set forth in claim 15 wherein said support means includes a drum of a dielectric material with one end coupled to the drive motor and further including spacers mounted to the walls of said drum with a filament stretched between pairs of said spacers and the reflectors attached to said filaments.

18. A radio frequency antenna system for obtaining uptilt of radiation above a reference line, comprising in combination:

a support including a drive motor, a central antenna array of omni-directional dipole radiators mounted to said support to be fixed in position with respect thereto, one of said radiators having a lagging current with reference to a feed point and the second radiator having a leading current with reference to the feed point to radiate a pattern above the reference line, a first plurality of two-part, spaced, parasitic reflectors radially positioned from said central antenna array, one part of each of said reflectors having a length greater than the second part with the longer of the two positioned radially from the first of said radiators and having a lagging current with reference to a current in said first radiator and said feed point and the second part positioned radially from the second of said radiators and having a leading current with reference to a current in said second radiator and said feed point to further uptilt the radiation pattern from said central array, a second plurality of spaced parasitic reflectors radially positioned between said central antenna array aNd said first plurality of parasitic reflectors, first support means for positioning said first plurality of parasitic reflectors and coupled to the drive motor of said support and rotated thereby to provide rotation of said reflectors around the central array for modulating the electromagnetic waves radiated therefrom at a first frequency, and second support means for positioning said second plurality of parasitic reflectors and coupled to the drive motor of said support and rotated thereby to provide rotation of said reflectors around the central array for modulating electromagnetic waves radiated therefrom at a second modulation frequency.

19. A radio frequency antenna system as set forth in claim 18 wherein each of said second plurality of spaced parasitic reflectors includes a first part having a length greater than the second part with the longer of the two parts positioned above the reference line to uptilt the radiation pattern from said central antenna array.

20. A radio frequency antenna system as set forth in claim 18 wherein said first support means includes a drum of a dielectric material with one end coupled to the drive motor and the parasitic reflectors attached to the walls of said drum.

21. A radio frequency antenna system as set forth in claim 18 wherein said first support means includes a drum of a dielectric material with one end coupled to the drive motor and further including spacers mounted to the walls of said drum with a filament stretched between pairs of spacers and the two parts of each parasitic reflector attached to said filaments.

22. A radio frequency antenna system as set forth in claim 18 including at least one radio frequency choke coupled to the omni-directional antennas of said central array to provide a main lobe beam angle above the reference line.