Electrically small antenna

• US 7,830,318 B2
• Filed: 04/30/2008
• Issued: 11/09/2010
• Est. Priority Date: 12/19/2007
• Status: Expired due to Fees

• Current Assignee: Wireless Fibre Systems
• Original Assignee: Wireless Fibre Systems
• Inventors: Hyland, Brendan, Rhodes, Mark
• Primary Examiner(s): Le; HoangAnh T
• Application Number:
  US12/112,315
• Publication Number:
  US 20090322641A1
• Time in Patent Office: 923 Days
• Field of Search: 343/709, 343/710, 343/810, 343/741, 343/742, 343/793
• US Class Current: 343/710
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence

Abstract

An antenna system, with a loop antenna and a loop current, is provided for transmitting an electromagnetic signal through a medium. The loop antenna has an E field transducer that generates an E field, and an H field transducer that generates an H field. The E and H fields are orthogonal in space and have at least one of a magnitude and phase relationship that is matched to an intrinsic impedance of a medium to generate a propagating wave. In an insulating medium the loop current lags an E field plate voltage by 90° to produce in phase E and H fields. In a conductive medium current is applied to the loop with a 135° phase lag with respect to a voltage across the E field plates. The H field is generated by the current component and leads current by 90°.

Claims

1. An antenna system for transmitting an electromagnetic signal through a medium, comprising:

a loop antenna with a loop current and including;

an E field transducer that generates an E field;

an H field transducer that generates an H field, wherein the E and H fields are orthogonal in space and have at least one of a magnitude and phase relationship that is matched to an intrinsic impedance of a medium to generate a propagating wave,

wherein in an insulating medium the loop current lags an E field plate voltage by 90°

to produce in phase E and H fields, and in a conductive medium current is applied to the loop with a 135°

phase lag with respect to a voltage across the E field plates, the H field is generated by the current component and leads current by 90°

.

2. The system of claim 1, wherein the H transducer is a parallel plate transducer that is co-located with a loop or solenoid for H field.

3. The system of claim 1, wherein in the conductive medium is water and the E and H fields are combined such that they have at least one of, a magnitude and phase relationship that is matched to the intrinsic impedance of the water.

4. The system of claim 1, wherein the E field transducer has a pair of parallel conducting plates.

5. The system of claim 4, wherein the parallel plates are arranged at either side of the H field transducer.

6. The system of claim 5, wherein multiple pairs of parallel plates are provided.

7. The system of claim 6, wherein each of a plate is driven with an in-phase voltage referenced to an adjacent plate that creates a constant E field vector across the loop.

8. The system of claim 6, wherein each of an adjacent pair of parallel plates is driven with anti-phase voltage.

9. The system of claim 6, wherein multiple the parallel plates are equally spaced.

10. The system of claim 6, wherein the parallel plates are alternately closely and widely spaced.

11. The system of claim 6, wherein at least one pair of parallel plates is in the H field transducer.

12. The system of claim 1, wherein the E field transducer is covered by an electrically insulating material.

13. The system of claim 1, wherein the H field transducer includes at least one magnetic dipole.

14. The system of claim 1, wherein at least two magnetic dipoles are provided in a Helmholtz coil arrangement.

15. The system of claim 14, wherein multiple dipoles are provided that are each operable to be independently driven.

16. The system of claim 1, wherein the H field transducer is an open cored solenoid.

17. The system of claim 1, wherein the H field transducer has a magnetic field that is substantially uniform in magnitude and direction throughout its volume.

18. The system of claim 1, wherein when the H field transducer has one or more loops volume is defined by the loop or loops.

19. The system of claim 1, wherein an electric field of the E field transducer is substantially uniform in magnitude and direction.

20. The system of claim 1, wherein when the E field transducer includes parallel plates the electric field is substantially uniform in magnitude and direction in a region between the plates.

21. The system of claim 1, wherein the E-field transducer includes a pair of conducting plates arranged at either side of a Helmholtz coil magnetic transducer with a dimension of at least twice a loop radius in a direction of a loop plane, and at least equal to the loop radius in a direction of loop separation, and positioned to generate a substantially uniform E field throughout a volume bounded by the two loops.

22. The system of claim 1, further comprising:

an apparatus for measuring a propagation medium conductivity and providing for adjustment of at least one of magnitude and phase relationship between the E and H fields in response to a measured conductivity.