1 / 49

RF in Science and Industry Jonathan Allen, Ph.D. RF Electronics Consulting Philadelphia CONET

RF in Science and Industry Jonathan Allen, Ph.D. RF Electronics Consulting Philadelphia CONET. What is RF?. Maxwell. James Clerk Maxwell 1831-79. RF Vs. Pwr. or LF. LF: S ystem dimensions << so propagation times are insignificant within system.

thetis
Download Presentation

RF in Science and Industry Jonathan Allen, Ph.D. RF Electronics Consulting Philadelphia CONET

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. RF in Science and IndustryJonathan Allen, Ph.D.RF Electronics ConsultingPhiladelphia CONET

  2. What is RF?

  3. Maxwell

  4. James Clerk Maxwell 1831-79

  5. RF Vs. Pwr. or LF • LF: System dimensions << so propagation times are insignificant within system. • RF: Phase diff. due to propagation times. • RF: Skin effect = (2/ o)1/2 [mks] • In RF plasmas, ion and electron migration per 1/2 cycle generally << sys. Dimensions. • Small L and C values much more important

  6. LF Capacitors & Inductors

  7. RF Capacitors & Inductors

  8. ISM Bands (U.S.)

  9. Examples of ISM RF • Heating of lossy materials • Plastic welding (PVC) • Cooking • Drying • Glue curing • Medical (diathermy, ablation, cautery) • Materials testing • NMR/MRI • Plasma processes • Sputtering & deposition • Etching • Spectroscopy

  10. RF Heating Polar molecules flip orientation as e-field reverses. Some of the energy is dissipated as heat (dielectric loss).

  11. RF Gluing (also plastic welding)

  12. RF Drying • Use for wood, foods, ceramic greenware • Fast • Selective--Heats only wet zones, uncured resins. • Uniform in depth. • Controllable • Reduce RF power as product approaches goal • Often uses 27 or 40 MHz

  13. RF Drying Wood SAGA RF-Vacuum Timber drying system

  14. Drying Potato Chips

  15. RF Induction Heating • Usually uses LF ~100 KHz for metals • Localized heating possible  Zone refining • No combustion products or oxygen (can heat in vacuum)

  16. Induction Heating Metal Rod

  17. Lab Measurement The same properties of polar molecules that enable RF heating also measure moisture content of wood, flour, etc. with an RF capacitance bridge. RF induction coils measure the thickness of metallic films and foils based on skin-depth.

  18. Plasmas Generate: • Free electrons • Positive ions • Radicals • Energetic particles • Spallation of target (sputtering) • Chemical reactions • Excited atoms and molecules • Light (glow discharge)

  19. Paschen Curves--Breakdown vs. PressureMFP (cm) = 5x10-3/p (torr)

  20. Plasma Sputtering Energetic ions impact target and dislodge atoms or molecules. These migrate to the substrate where they deposit to form a thin film. Sputtering may be reactive, such as an aluminum target whose sputtered atoms reacting with oxygen in the process gas to form an Al2O3 film.

  21. Plasma Sputtering

  22. Plasma Etching Plasma produces chemically active radicals which react with unmasked areas of wafer. This etches away material. e.g. Fluorine radicals and ions etch silicon: C F4 + e- C F3 + F + e- Si + 4F  Si F4

  23. Plasma Etching with Mask DC field superimposed on RF helps accelerate F- ions Plasma Mask RF

  24. Amorphous Si Plasma Deposition SiH4 Si  + 2 H2

  25. ICP Spectroscopy

  26. How to Generate RF • Spark generator (obsolete, dirty) • Power oscillator (efficient, cheap, but frequency not well defined) • Oscillator (usu. xtal), driving Power amplifier (present industry standard) • Vacuum tubes • Bipolar transistors • Power FETs

  27. Power Oscillator

  28. Oscillator-Amplifier System

  29. Power Tubes 4-400C, 5CX1500A

  30. RF Power Transistor

  31. Impedance Matching RF generators conventionally have 50 (resistive) output impedance. Loads can have any complex (and varying) impedance. Matching networks allow the generator always to see a 50 resistive load and therefore operate efficiently.

  32. L Network

  33. Pi Network

  34. Univ. Matching Network, Can set as L or Pi

  35. Allen Matching Network

  36. Allen MN Physical Construction

  37. RF Instrumentation • Current measurement • Voltage measurement • Broadband • Frequency selective • Directional power • Circuit analysis

  38. RF Ammeter

  39. RF Ammeter (Square-law scale)

  40. Induction Ammeter

  41. VTVM with HF Probe (hp 410C)

  42. Calibrated Receiver (EMC-25)

  43. Single Frequency Detector

  44. Directional Wattmeter (Bird 43)

  45. RF Impedance Meter (hp 4815A)

  46. Grid Dip Meter (Measurements 59)

  47. Important Uses of RF • Food • Construction • Metallurgy • Semiconductors (Discrete, IC, Photovoltaic) • Optics • Health and Medicine • Laboratory science

More Related