Broadband isotropic probe system for simultaneous measurement of complex E- and H-fields

• US 4,588,993 A
• Filed: 05/19/1983
• Issued: 05/13/1986
• Est. Priority Date: 11/26/1980
• Status: Expired due to Fees

• Current Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Original Assignee: United States Department Of Health And Human Services (Government of the United States of America)
• Inventors: Bassen, Howard, Babij, Tadeusz M.
• Primary Examiner(s): Blum, Theodore M.
• Assistant Examiner(s): Cain, David
• Application Number:
  US06/496,275
• Time in Patent Office: 1,090 Days
• Field of Search: 343/351, 343/383, 343/703, 343/850, 343/853, 343/855, 343/866, 343/867, 343/893, 324/158 P, 324/72, 324/72.5
• US Class Current: 342/351
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24
• CPC Class Codes: G01R 29/0892 Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
• CPC Class Codes: G01R 33/028 Electrodynamic magnetometers
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• CPC Class Codes: H01Q 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence

Abstract

A broadband isotropic probe system simultaneously measuring the E- and H-field intensities of rf complex, near-field electromagnetic radiation comprises a set of three mutually orthogonal dipole antennas and a set of three mutually orthogonal loop antennas located within the same volume of space. Each antenna has associated circuitry comprising a frequency-response-shaping filter and diode detector to provide a frequency response which is flat over the desired frequency bandwidth. The lengths of the dipoles are kept electrically small so that the EM fields are not perturbed. The diameters of the loops are kept electrically small so that the E-field pickup will be negligible. Coupling between any of the probe'"'"'s antennas is also minimized by the use of electrically small antennas. Circuit means based on the use of square law detectors is also provided, the circuit including an arrangement of analog or digital data processing portions leading into a display means and a data recorder.

Claims

1. An isotropic, broad band, non-directional, rf electromagnetic radiation probe, comprising:

an isotropic set of E-field antennas;

an isotropic set of H-field antennas essentially encompassing the same volume of space as the set of E-field antennas; and

circuit means for simultaneously meauring and displaying the sum of any of the squared vector components of both the E-field and the H-field radiation detected by said probe, said circuit means comprising switching means square law detector means associated with each antenna in each of said sets of antennas, summing means, means for feeding the outputs of said square law detectors to said summing means, display means, and means for feeding the output of said summing means to said display means.

2. A probe as set forth in claim 1, wherein said E-field antennas are dipoles each having a length equal to or less than one-tenth the wavelength of the maximum frequency to be received, and said H-field antennas are loops having diameters equal to or less than one-tenth of the wavelength of the maximum frequency to be received.

3. A probe as set forth in claim 2, further including:

filter means for flattening the response of said antennas over a desired frequency range; and

detection means for detecting the output signals of said filter means.

13. A probe as set forth in claim 1, and said circuit means comprising signal conditioning means positioned in said circuit means between the output of each of said square law detector means and said summing means.

14. A probe as set forth in claim 1, said summing means comprising both analog data processing means and digital data processing means, both arranged in said circuit means between the outputs of said square law detector means and said display means.

15. A probe as set forth in claim 14, said analog data processing means comprising a pair of summing amplifiers, means to feed the outputs of said E-field antennas to one of said summing amplifiers, and means to feed the outputs of said H-field antennas to the other of said summing amplifiers, and means to feed the outputs of said pair of summing amplifiers to said display means.

16. A probe as set forth in claim 15, and three separate manually operable switch means one associated with each of the three inputs to each of said pair of summing amplifiers.

17. A probe as set forth in claim 14, said digital data processing means comprising a multi-channel analog-to-digital converter, and data processing means arranged in said circuit between the outputs of said square law detectors and said display means.

18. A probe as set forth in claim 14, said display means including means to separately display the total E-field and the total H-field detected by said antennas.

19. A probe as set forth in claim 14, said display means including data recording means to permit recording of the electric and magnetic field data for later analysis.

4. An isotropic, broadband, non-directional rf electromagnetic radiation probe comprising:

a set of three mutually orthogonal E-field antennas; and

a set of three mutually orthogonal H-field antennas located such that both sets of antennas encompass essentially the same volume of space; and

circuit means for simultaneously measuring said displaying the sum of a selectable combination of the squared vector components of both the E-field and the H-field radiation detected by said probe, said circuit means comprising square law detector means associated with each antenna in each of said sets of antennas, summing means, means for feeding the outputs of said square law detectors to said summing means, display means, and means for feeding the output of said summing means to said display means.

5. A probe as set forth in claim 4, wherein the physical size of said antennas is small compared to the wavelength of the highest frequency to be received.

6. A probe as set forth in claim 4, wherein said E-field antennas comprise dipoles and said H-field antennas comprise loops.

7. A probe as set forth in claim 6, wherein said E-field antennas have lengths equal to or less than one-tenth the wavelength of the maximum frequency to be received by the probe.

8. A probe as set forth in claim 7, further comprising:

first means coupled to each of said E-field antennas for flattening the response of said antennas over a desired frequency range and for detecting received signals; and

second means coupled to each of said H-field antennas for flattening the response of said antennas over the desired frequency range and for detecting received signals.

9. A probe as set forth in claim 7, further including high-resistance leads to couple out the detected signals.

10. A probe as set forth in claim 8, wherein:

said first means comprises a high-pass RC filter and a diode detector; and

said second means comprises an RC filter and a diode detector.

11. A probe as set forth in claim 10, wherein said diode detectors are Schottky diodes.

12. A probe as set forth in claim 10, further including high-resistance leads connected to couple out the detected signals.

20. An isotropic, broadband, non-directional, rf electromagnetic radiation probe comprising:

a set of three mutually orthogonal dipole antennas;

a set of three mutually orthogonal loop antennas essentially encompassing the same volume of space as set of dipole antennas;

a plurality of filters coupled to said dipole antennas to flatten out the response of each of said dipoles over a desired frequency range;

a plurality of filters coupled to said loop antennas to flatten the response of each of said loops over a desired frequency range;

Schottky diode detectors coupled to said filters to provide detected signals from the outputs of said filters; and

circuit means for simultaneously measuring the total electric field detected by said dipole antennas and total H-field radiation detected by said loop antennas, said circuit means comprising square law detector means associated with each antenna in each of said sets of antennas, summing means, means to read the outputs of said square law detectors to said summing means, display means, and means to feed the output of said summing means to said display means.

21. A probe as set forth in claim 20, further including high-resistance leads connected to couple out the detected signals.

22. A probe as set forth in claim 20, said summing means comprising both analog data processing means and digital data processing means, both arranged in said circuit between the outputs of said Square Law Detector means and said display means.