System and method for monitoring substances and reactions

• US 20010019271A1
• Filed: 12/21/2000
• Published: 09/06/2001
• Est. Priority Date: 07/26/1994
• Status: Active Grant

• Current Assignee: Bentley N. Scott, Samuel R. Shortes
• Original Assignee: Bentley N. Scott, Samuel R. Shortes
• Inventors: Scott, Bentley N., Shortes, Samuel R.
• Granted Patent: US 6,593,753 B2
• Time in Patent Office: Days
• US Class Current: 324/637
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: G01N 22/04 Investigating moisture content
• CPC Class Codes: G01R 1/06772 High frequency probes
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24

Abstract

Systems, methods, and probe devices for electronic monitoring and characterization using single-ended coupling of a load-pulled oscillator to a system under test

Claims

1. A system for detecting the composition and microstructure of materials, comprising:

an RF oscillator, which includes

a gain element capable of providing substantial gain at frequencies greater than 100 MHz;

a feedback path, coupling the output of said gain element to the input thereof, said feedback path including a tunable resonant circuit;

a single electromagnetic propagation structure which is RF-coupled, in a single-ended configuration, to said oscillator and in which electromagnetic wave propagation is electrically loaded by a portion of the material to be characterized; and

circuitry connected to monitor the frequency of said oscillator to ascertain changes in the composition and/or microstructure of the material.

2. A system for detecting the composition and microstructure of materials, comprising:

an RF oscillator, which includes a gain element capable of providing substantial gain at frequencies greater than 100 MHz, and a feedback path, coupling the output of said gain element to the input thereof, said feedback path including a tunable resonant circuit; and

an electromagnetic propagation structure which is RF-coupled to said oscillator and in which electromagnetic wave propagation is electrically loaded by a portion of the material to be characterized,

said propagation structure including a distributed impedance transformation section which includes at least one tapered element and which is itself also electrically loaded by proximity to a portion of the material; and

circuitry connected to monitor the frequency of said oscillator to ascertain changes in the composition and/or microstructure of the material.

3. The system of

claim 2

, wherein said propagation structure, including said impedance transformation section thereof, is entirely included on a planar substrate.

4. The system of

claim 2

, wherein said propagation structure is nonresonant at all frequencies of operation of said oscillator.

5. A single-ended RF probe, for providing a bidirectional RF interface, over a wide range of frequencies, to unknown materials of widely varying permittivity, comprising:

an external RF connection mechanically connected to a support structure; and

a patterned and substantially planar conductive structure which is electrically connected to said connection and mechanically supported by said support structure;

said conductive structure being shaped to provide a distributed impedance transformation section therein, extending over multiple half-wavelengths at all of said range of frequencies.

6. The probe of

claim 5

, wherein said propagation structure is nonresonant over at least a predetermined range of operating frequencies.

7. The probe of

claim 5

, wherein said distributed impedance transformation section consists essentially of a tapered planar stripline section.

8. The probe of

claim 5

, wherein said propagation structure, including said impedance transformation section thereof, is entirely included on a planar substrate.

9. A method for detecting the composition and microstructure of materials, comprising the steps of:

providing a oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a single-ended probe which itself includes a distributed impedance transformation section which is itself electrically loaded by proximity to a portion of the material under test; and

observing changes in the frequency of said oscillator.

10. The method of

claim 9

, wherein said observing step also monitors insertion loss as seen by said oscillator.

11. The method of

claim 9

, wherein said oscillator is a voltage-controlled oscillator, and said observing step monitors the dependence of oscillator frequency on tuning voltage as said oscillator is tuned across a range of frequencies.

12. The method of

claim 9

, wherein said propagation structure is nonresonant at all frequencies of operation of said oscillator.

13. A single-ended RF probe, for providing a bidirectional RF interface over a range including at least one predetermined operating frequency, to unknown materials of widely varying permittivity, comprising:

an external RF connection mechanically connected to a dielectric substrate; and

a substantially planar metal film structure which is patterned to provide a transmission line extending from said connection for at least three half-wavelengths at said predetermined operating frequency;

said metal film structure being electrically connected to said RF connection and mechanically supported by said substrate.

14. A method for detecting the composition and microstructure of materials, comprising the steps of:

providing a oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a single-ended probe which includes a substantially planar metal film structure which is patterned to provide a transmission line extending from said connection; and

observing changes in the frequency of said oscillator.

15. A single-ended RF probe, for providing a bidirectional RF interface over a range including at least one predetermined operating frequency, to detect the presence of at least one target species in a quantity of material, comprising:

an external RF connection mechanically connected to a support structure; and

a conductive structure which is electrically connected to said external connection and mechanically supported by said support structure, and which provides a transmission line extending from said external connection; and

a selective absorption material, which is selective to preferentially absorb a predetermined target species, and which is mechanically connected to said support structure in a relation which provides efficient electromagnetic coupling to said selective transmission line.

16. A method for detecting the composition and microstructure of materials, comprising the steps of:

providing an oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a single-ended probe which includes a substantially planar metal film structure which is patterned to provide a transmission line extending from said external connection, and which also includes a selective absorption material, which is selective to preferentially absorb a predetermined target species, and which is mechanically affixed to said probe to provide efficient electromagnetic coupling to said transmission line; and

observing changes in the frequency of said oscillator.

17. A system for detecting the composition and microstructure of materials, comprising:

an oscillator, which includes a gain element capable of providing substantial gain at frequencies greater than 100 MHz and a feedback path, coupling an output of said gain element to an input thereof;

an electromagnetic propagation structure which is RF-coupled to said oscillator and in which electromagnetic wave propagation is electrically loaded by a portion of the material to be characterized,

said propagation structure being mechanically connected to a selective absorption material, which is selective to preferentially absorb a predetermined target species, and electrically configured to provide efficient electromagnetic coupling to said propagation structure, and also to a heater integrated with said propagation structure in a common package; and

circuitry connected to monitor the frequency of said oscillator to ascertain changes in the composition or microstructure of the material, and to activate said heater selectively which said absorption material has become loaded.

18. The system of

claim 17

, wherein said transmission line is nonresonant at all frequencies of operation of said oscillator.

19. A single-ended RF probe, for providing a bidirectional RF interface over a range including at least one predetermined operating frequency, to detect the presence of at least one target species in a quantity of material, comprising:

an external RF connection mechanically connected to a support structure;

a conductive structure which is electrically connected to said external connection and mechanically supported by said support structure, and which provides a transmission line extending from said external connection; and

a resistive heater which is mechanically supported by said support structure, and connected to receive a drive current; and

a selective absorption material, which is selective to preferentially absorb a predetermined target species, and which is mechanically connected to said support structure in a relation which provides efficient electromagnetic coupling to said transmission line.

20. The probe of

claim 19

, wherein said transmission line is nonresonant over at least a predetermined range of operating frequencies.

21. A method for detecting the composition of materials, comprising the steps of:

providing an oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a single-ended probe which includes

connecting said load connection to the material under test through a single-ended probe which includes a conductive structure which is patterned to provide a transmission line extending from said external connection, and which also includes a selective absorption material which is selective to preferentially absorb a predetermined target species and which is mechanically affixed to said probe to provide efficient electromagnetic coupling to said transmission line, and a resistive heater which is integrated with said probe; and

observing time t changes in the frequency of said oscillator to detect the rate of uptake of said target species and the cumulative loading of said absorber; and

activating said heater, whenever said absorber becomes excessively loaded, to cause desorption of said target species.

22. The method of

claim 21

, wherein said transmission line is nonresonant at all frequencies of operation of said oscillator.

23. A method for monitoring the status of a fermentation process, comprising the steps of:

introducing selected active microorganisms into an aqueous solution containing nutrient substances, and isolating said solution in a substantially sterile vat;

electromagnetically coupling a nonresonant RF probe to said solution in said vat, and connecting said probe to an oscillator operating at more than 100 MHz, with no RF buffer stage being interposed between said oscillator and said probe, and

observing time-dependent changes in the frequency behavior of said oscillator, to indicate changes in the composition of said solution.

24. A method for initiating a fermentation process, comprising the steps of:

introducing selected active microorganisms from a starter culture into a nutrient solution, while also

monitoring the flow rate of said introducing step and

monitoring the frequency of an RF oscillator which is connected to said starter culture through a nonresonant RF probe which is electromagnetically coupled by proximity to be loaded by said starter culture, with no RF buffer stage being interposed between said oscillator and said probe; and

terminating said flow to provide a desired total biomass transferred from said starter culture into said nutrient solution.

25. The method of

claim 24

, wherein said RF probe is a single-ended probe.

26. The method of

claim 24

, wherein said RF probe is a single-ended probe including a section of transmission line which is electromagnetically coupled to materials in proximity thereto.

27. The method of

claim 24

, wherein said RF probe is inserted through a load lock into said solution.

28. The method of

claim 24

, wherein said RF probe is immersed in said solution.

29. The method of

claim 24

, wherein behavior of said RF probe is observed immediately after introduction of said microorganisms, to determine whether said microorganisms are viable.

30. The method of

claim 24

, wherein behavior of said RF probe is observed near completion of fermentation, and is used for endpoint detection.

31. The method of

claim 24

, wherein said microorganisms are yeast.

32. A method for monitoring the state of curing (or microcrystalline change) of solid materials, comprising the steps of:

combining precursor components to provide a body having a desired physical shape;

electromagnetically coupling a single-ended nonresonant RF probe to said body, and connecting said probe to an oscillator operating at more than 100 MHz, with no RF buffer stage being interposed between said oscillator and said probe; and

observing time-dependent changes in the frequency behavior of said oscillator, to detect changes in the composition and/or microcrystalline structure of said body.

33. A method for controlling a process of curing a predetermined solid material, comprising the steps of:

combining precursor components to provide a body of said material;

electromagnetically coupling a single-ended nonresonant RF probe to said body, and connecting said probe to an oscillator operating at more than 100 MHz, with no RF buffer stage being interposed between said oscillator and said probe; and

observing time-dependent changes in the frequency behavior of said oscillator, to detect changes in the composition and/or microcrystalline structure of said body.

34. The method of

claim 33

, wherein said RF probe is a single-ended probe including a section of transmission line which is electromagnetically coupled to materials in proximity thereto.

35. The method of

claim 33

, wherein said RF probe is a single-ended probe including a section of transmission line which is electromagnetically coupled to materials in proximity thereto.

36. The method of

claim 33

, wherein said RF probe is inserted into said body.

37. The method of

claim 33

, wherein said RF probe is not inserted into said body, but is placed in proximity therewith.

38. A method for food and analogous material, comprising the steps of:

providing multiple process feeds of ingredient materials

electromagnetically coupling a single-ended nonresonant RF probe to at least one said feed of ingredient materials, said probe being electrically connected to a free-running RF oscillator, with no RF buffer stage being interposed bete said oscillator and said probe; and

observing the frequency behavior of said oscillator, to detect variation in the composition of said respective feed of ingredient materials; and

combining and processing said feeds of ingredient materials to provide a food product, while dynamically controlling one or more process parameters in accordance with results of said observing step.

39. The method of

claim 38

, wherein said observing step monitors said materials for spoilage.

40. The method of

claim 38

, wherein said observing step monitors said materials for fat content.

41. The method of

claim 38

, wherein said observing step monitors said materials for sugar content.

42. A method for drying organic materials, comprising the steps of:

providing a process feed of a material which varies in water content;

electromagnetically coupling a nonresonant RF probe to said feed, said probe being electrically connected to a free-running RF oscillator, with no RF buffer stage being interposed between said oscillator and said probe;

observing the frequency behavior of said oscillator, to detect the moisture content of said feed; and

adding water to said feed whenever said observing step indicates that the moisture content of said feed is below a target level; and

drying said feed in a dryer stage;

whereby the moisture content of said feed is dynamically controlled to be high enough to assure reliable and high-quality operation of said dryer, but no higher than necessary for reliable operation.

43. A method for cooking food and analogous materials, comprising the steps of:

introducing a mixture of predetermined ingredients into a cooking vessel;

applying heat to said vessel in a controlled temperature-versus-time relationship, to cook said mixture;

electromagnetically coupling a nonresonant RF probe to said mixture in said vessel, and connect said probe to an oscillator operating at more than 100 MHz, with no RF buffer stage ben interposed between said oscillator and said probe;

observing the frequency behavior of said oscillator, to detect changes in the molecular composition and/or conformation of said mixture; and

unloading said vat at a time which is at least partially determined by the results of said observing step.

44. A system for detecting the composition and microstructure of materials, comprising:

an oscillator, which includes a gain element capable of providing substantial gain at frequencies greater than 100 MHz, and a feedback path, coupling an output of said gain element to an input thereof;

a patch antenna which is RF-coupled to said oscillator and which is placed in proximity to a portion of the material to be characterized so that electromagnetic wave propagation in said antenna is electrically loaded thereby; and

circuitry connected to monitor the frequency of said oscillator to ascertain changes in the composition or microstructure of the material.

45. The system of

claim 44

, wherein said patch antenna is a planar spiral antenna with backside shielding.

46. The system of

claim 44

, wherein said oscillator is a voltage-controlled oscillator.

47. A method for detecting the composition and microstructure of materials, comprising the steps of:

providing a free-running oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a patch antenna which is RF-coupled to said oscillator and which is placed in proximity to a portion of the material to be characterized so that electromagnetic wave propagation in said antenna is electrically loaded thereby; and

observing changes in the frequency of said oscillator.

48. The method of

claim 47

, wherein said oscillator is a voltage-controlled oscillator, and wherein said observing step sweeps said oscillator across a wide range of frequencies while monitoring the dependence of the oscillator frequency on the tuning voltage.

50. The method of

claim 47

, wherein said RF interface consists of a single-ended probe.

51. The method of

claim 47

, wherein said RF interface consists of a single-ended probe which is immersed in a fluid stream of said process.

49. A method for controlling a process, comprising the steps of:

providing a voltage-controlled oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto, and which is connected to be tuned by a tuning voltage applied thereto;

connecting said load connection to an RF interface which is electrically loaded by proximity to material undergoing the process;

sweeping said tuning voltage across a predetermined range of voltages;

integrating the oscillation frequency of said oscillator, as a function of tuning voltage, across said range of voltages, to provide a process index value;

comparing said process index value with a known range of values for comparable process conditions; and

taking action conditionally, within said process, in dependence on the result of said comparing step.

52. A single-ended RF probe, for providing a bidirectional RF interface to materials to be characterized, comprising:

an external RF connection mechanically connected to a dielectric support structure; and

an RF switch mounted on said support structure and electrically connected to said external connection; and

first and second transmission line structures, each connected to said switch and mounted on said support structure;

wherein said switch is connected and configured to connect said first transmission line structure to said external connection selectively, in accordance with a bias signal received at said external connection.

53. The probe of

claim 52

, wherein said switch is connected and configured to connect either said first transmission line sure or said second transmission line structure to said external connection selectively, in accordance with DC bias received at said external connection.

54. The probe of

claim 52

, wherein said first transmission line structure, but not said second transmission line suture, is located in proximity to a selective absorption material, which is selective to preferentially absorb a p mind target species, and which is mechanically connected to said support structure in a relation which provides efficient electromagnetic coupling to said first transmission line structure.

55. The probe of

claim 52

, wherein said support structure is a planar subs, and said first and second transmission line structures are mutually coplanar.

56. A method for detecting the composition and microstructure of as, comprising the steps of:

providing an oscillator which is connected to be pulled by the varying susceptance seen at a load connection thereto;

connecting said load connection to the material under test through a single-ended probe which includes an RF switch and first and second transmission line structures, said switch being connected and configured to connect said first transmission line structure to said external connection selectively under remote command;

positioning said probe so that at least one of said transmission line structures is electrically loaded by proximity to a portion of the material to be characterized; and

observing changes in the frequency of said oscillator, while switching said RF switch to activate said first and second transmission lines alternately.

57. The method of

claim 56

, wherein said observing step monitors not only the frequency of said oscillator, but also insertion loss of said probe.

58. Systems substantially as herein shown and described.

59. Methods for characterization and/or process control substantially as herein shown and described.