Near-field gradient probe for the suppression of radio interference

Patent metadata

Field	Value
Publication number	US-9812790-B2
Application number	US-201514677130-A
Country	US
Kind code	B2
Filing date	Apr 2, 2015
Priority date	Jun 23, 2014
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

An antenna system is provided comprising first, second, and third loop antennas, each antenna having a respective loop area and spaced apart from the other antennas. The first and third antennas are configured and driven to form a first independent balanced feed point that is substantially isolated from the second antenna, which is configured to be driven from a second balanced feed point. A sum of the first and second respective loop areas, at a sum port in operable communication with the first and second balanced feed points, is substantially equivalent to the third respective loop area. An automatic control system is configured to automatically and independently adjust, via the balanced feed points, at least one of amplitude and phase for at least one of the three loop antennas, to help to substantially maximize suppression of RFI for a sum of signals from the first and second balanced feed points.

First claim

What is claimed is:

1. An antenna system, comprising:
a first loop antenna comprising a first conductor forming a first loop, the first loop having a first respective loop area;
a second loop antenna spaced apart from the first loop antenna, the second loop antenna comprising a second conductor forming a second loop, the second loop antenna having a second respective loop area;
a third loop antenna spaced apart from both the first and second loop antennas, the third loop antenna comprising a third conductor forming a third loop having a third respective loop area, wherein:
the first and third loop antennas are operably coupled together in electrical opposition to each other, configured to be driven to form a first independent balanced feed point, and configured to be substantially electrically and magnetically isolated from the second loop antenna;
the second loop antenna is configured to be driven from a second balanced feed point;
the first, second and third loops are configured such that a sum of the first and second respective loop areas, at a sum port in operable communication with the first and second balanced feed points, is substantially equivalent, within a predetermined tolerance, to the third respective loop area; and

the first and second balanced feed points are in operable communication with an automatic control system configured to automatically and independently adjust at least one of amplitude and phase for at least one of the first, second, and third loops in operable communication with at least one of the first and second balanced feed points, where each respective automatic and independent adjustment is configured to help to substantially maximize suppression of radio frequency interference (RFI) for a sum of signals from the first and second balanced feed points.

2. The antenna system of claim 1 , wherein the automatic control system comprises:
a first amplitude adjustment circuit under automatic control and in operable communication with a respective one of the first and second loops; and
a first phase adjustment circuit under automatic control and in operable communication with a respective one of the first and second loops;
wherein the first amplitude adjustment circuit is configured to operate independently of the first phase adjustment circuit.

3. The antenna system of claim 1 , wherein the automatic control system further comprises a first tune/match adjustment circuit in operable communication with an automatic control and a respective one of the first and second loops, the tune/match adjustment circuit responsive to a first control signal configured to provide tuning of the respective one of the first and second loops, the tuning configured to adjust a resonant frequency of the respective one of the first and second loops.

4. The antenna system of claim 1 , wherein the automatic control system further comprises a first tune/match adjustment circuit in operable communication with an automatic control and a respective one of the first and second loops, the first tune/match adjustment circuit configured to provide phase matching for the respective one of the first and second loops.

5. The antenna system of claim 1 , wherein the antenna system is in operable communication with a mechanical control configured to adjust a size of one of the first, second, and third loops,
wherein the adjustment provided by the mechanical control cooperates with one or more of the adjustments performed by the automatic control system, to help to substantially maximize suppression of RFI.

6. The antenna system of claim 1 , wherein the first loop comprises an inner loop, the second loop comprises a middle loop, and the third loop comprises an outer loop.

7. The antenna system of claim 6 , wherein, for a given inter-loop ratio factor K, the inter-loop ratios are defined as follows:

K

(

outer
⁢

⁢
loop

)

=
1

K

(

middle
⁢

⁢
loop

)

=

K
2

K

(

inner
⁢

⁢
loop

)

=

[

2
-
K

2

]

8. The antenna system of claim 7 , wherein K is between about 1.125 to about 1.25.

9. The antenna system of claim 1 , wherein at least two of the first, second, and third loops have substantially similar shapes.

10. The antenna system of claim 1 , wherein at least two of the first, second, and third loops are substantially concentric.

11. The antenna system of claim 1 , wherein at least one of the first, second, and third loops comprises a respective set of two or more sub-loops, each sub-loop having a respective sub-loop area, wherein the sum of all the respective sub loop areas in the respective set is substantially equivalent to the respective loop area of the at least one of the first, second and third loops.

12. The antenna system of claim 1 , wherein the first, second and third loops are substantially coplanar.

13. The antenna system of claim 1 , wherein the first and third loops are substantially coplanar and lie within a first plane, and the second loop lies within a second plane that is spaced apart from but parallel to the first plane.

14. The antenna system of claim 1 , wherein:
(a) if any two of the first, second, and third loops have substantially the same respective loop area as each other, then a first spacing S 1 is defined as being between the two loops having substantially the same respective loop area; and
(b) if the respective loop areas of any two of the first, second and third loops, when added together, form a pair of loops that together have substantially the same loop area as the remaining one of the first, second and third loops, then a second spacing S 2 is defined as being between either one of the pair of loops and the remaining one of the first, second, and third loops;
wherein at least one of S 1 and S 2 is selected to help to maximize RFI suppression at a given operational frequency λ, where:

RFI
⁢

⁢
Suppression

Assignees

• Raytheon Co

Inventors

• Lavedas Thomas G

Classifications

• H01Q21/28 Primary

  Combinations of substantially independent non-interacting antenna units or systems {(multiple beam H01Q25/00)} · CPC title

• H01Q7/02

  Collapsible antennas; Retractable antennas · CPC title

• H01Q7/005

  with variable reactance for tuning the antenna · CPC title

• H01Q1/521

  reducing the coupling between adjacent antennas · CPC title

• G01R33/441

  Nuclear Quadrupole Resonance [NQR] Spectroscopy and Imaging · CPC title