WO1997027611A1 - Inductive tuners for microwave driven discharge lamps - Google Patents

Inductive tuners for microwave driven discharge lamps Download PDF

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Publication number
WO1997027611A1
WO1997027611A1 PCT/US1997/001106 US9701106W WO9727611A1 WO 1997027611 A1 WO1997027611 A1 WO 1997027611A1 US 9701106 W US9701106 W US 9701106W WO 9727611 A1 WO9727611 A1 WO 9727611A1
Authority
WO
WIPO (PCT)
Prior art keywords
waveguide
lamp
power
disposed
cavity
Prior art date
Application number
PCT/US1997/001106
Other languages
French (fr)
Inventor
James E. Simpson
Original Assignee
Fusion Lighting, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fusion Lighting, Inc. filed Critical Fusion Lighting, Inc.
Priority to IL12529597A priority Critical patent/IL125295A0/en
Priority to JP9527008A priority patent/JP2000504144A/en
Priority to EP97903942A priority patent/EP1016124A4/en
Priority to AU18372/97A priority patent/AU1837297A/en
Publication of WO1997027611A1 publication Critical patent/WO1997027611A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J65/00—Lamps without any electrode inside the vessel; Lamps with at least one main electrode outside the vessel
    • H01J65/04—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels
    • H01J65/042—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field
    • H01J65/044—Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating plasma display panels by an external electromagnetic field the field being produced by a separate microwave unit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/56—One or more circuit elements structurally associated with the lamp

Definitions

  • This invention refers to the field of radio-frequency driven arc lamps in which the structure includes a closed waveguide, and particularly to those lamps which utilize a magnetron as the source of power.
  • lamps employ an ionizable medium enclosed in a sealed transparent envelope which produces visible light or ultraviolet light when excited by an intense microwave field.
  • the lamp envelope or bulb is enclosed in a metal container or cavity which confines the microwaves while providing for the escape of the light, usually by means of a metal screen.
  • Microwaves are admitted into the cavity through an aperture which connects to the adjoining waveguide, the other end of which couples to the magnetron.
  • Rf power from the magnetron travels through the waveguide to the cavity and excites the discharge lamp. Any power that is not absorbed by the lamp reflects back to the magnetron.
  • the aperture defining the end of the cavity may be used to define a resonance in the cavity which intensifies the fields at the bulb to provide increased power absorption, thus reducing the reflected power.
  • a magnetron is a self-excited oscillator with a direct connection between its resonator and the output load. Any reflection from the load has a strong effect on the performance, changing the operating frequency, the power output and the operating stability. Strong reflections at a particular phase known as the "sink" reduce the stored energy in the magnetron's resonator, causing instability and frequency jumping.
  • the lamp itself places several different requirements on its power source. Before ionization, gases in the bulb do not absorb microwave power. The electric field intensity within the bulb must be built up to a high level to achieve breakdown. Once ionization occurs, the bulb must heat to evaporate any condensed fill materials. The impedance of the bulb is much lower than the non-ionized case, and changes as the bulb heats, bringing the condensates into the discharge. And finally the long term operating condition is reached in which light output efficiency is the dominant concern.
  • the designer can adjust the aperture of the cavity, the length of the waveguide and may add a variety of tuning elements into the waveguide.
  • the goal is to keep the high reflection before ionization away from the sink, to avoid frequency-jumping during the warm-up cycle and to provide a good match with stable characteristics during long-term operation.
  • Other considerations may also enter into the design.
  • the product needs to be economical, compact in size, durable, and reproducible. Cost prevents the use of isolators. Compact size holds the waveguide to a minimum length.
  • the tuning element frequently used in microwave arc lamps is the capacitive screw or a fixed height knob of the same size. This has the advantage of attaching to only one wall and is more easily installed than a post which must contact two opposite walls.
  • this capacitive tuner may be used to match a moderate mismatch or any phase.
  • the tuner has two effects. The reflection coefficient is added to the reflection coefficient of the load beyond it. Secondly, the effective length of the waveguide is increased by a small amount.
  • An inductive tuner was placed on the side wall of the waveguide between the magnetron and the cavity aperture.
  • a metal protrusion at the side of a waveguide acts like an inductive iris, raising the cutoff frequency of the waveguide at its location.
  • the tuner provides a reflection coefficient with an inductive phase and shortens the effective length of the waveguide a small amount.
  • the lamp design operates efficiently with this tuner.
  • the inductive tuner may be a single block, semi-cylinder, or hemisphere or combination thereof attached to one side wall, or two such objects may face each other on opposite walls. These shapes are appropriate where the tuners are to be installed in a waveguide after it is built, as for example, by screws, soldering or welding.
  • the tuner may also be molded into the waveguide wall. Depending upon the method of construction it may be advantageous to form the tuner to join to the upper and/or lower broad wall of the waveguide as a thick iris.
  • Figure 1 is a schematic representation of a microwave lamp.
  • Figure 2 illustrates an inductive tuner in the form of a single block.
  • Figure 3 illustrates an inductive tuner in the form of two blocks which face each other on opposite waveguide walls.
  • Figure 4 illustrates an inductive tuner in the form of a semi- cylinder contacting the broad walls of a waveguide.
  • Figure 5 illustrates an inductive tuner in the form of a semi- cylinder which does not contact the broad walls of a waveguide.
  • Magnetron 2 has antenna 4 which protrudes into closed waveguide 6.
  • coupling slot 8 is located, which couples microwave power into the resonant cavity defined by bottom 10 and screen 12 in which bulb 9 is located.
  • inductive tuner 14 is attached to a side wall of the waveguide.
  • the waveguide has broad walls and narrow walls (side walls) . Since the magnetic field is high at the side walls, a metal protrusion placed there will act as an inductive tuner.
  • the location of the tuner as well as its size and shape are determined by experimentation, with the aid of a network analyzer.
  • the network analyzer is first calibrated with the aid of a sliding short. The impedance is then observed with the lamp in the starting and running conditions without a tuner. If significant reflection is present when the lamp is at operating temperature a tuner of trial size and shape is used and its position changed to determine the position of optimum operation. If significant reflection is still present, the size and/or shape of the tuner is varied, and various positions again tried.
  • rectangular waveguide 6 is 1.7" high, 2.84" wide, and 4.8" long on the inside.
  • the distance from the middle of the tuner to the slot end of the waveguide is about 1 7/8", and the tuner is about 5/8" wide, 1 1/4" long, and has a thickness of about .35".
  • the coupling slot 8 is 2 3/8" long and .53" wide.
  • the microwave cavity is 2.93" in diameter and 6.2" tall.
  • the bulb 9 is 35 mm inside diameter and contains a fill of sulfur and rare gas such as argon.
  • Both the waveguide and the tuner may be made of aluminum. It is preferable to make the waveguide and the tuner of the same material to minimize corrosion.
  • a motor rotates both the shaft 20 to which bulb 9 is attached and blower wheel 22 which provides air for cooling the magnetron.
  • Figure 2 is a cut-away detail of waveguide 6 of Figure 1, and shows the inductive tuner in the form of metal block 14.
  • Figure 3 shows an alternative embodiment wherein two such blocks 14'a and 14'b face each other on opposite waveguide walls.
  • Figure 4 shows a further alternative embodiment which utilizes a protrusion in the form of semicylinder 14" which contacts the top and bottom broad walls 30 and 32 of the waveguide.
  • Figure 5 shows still a further embodiment which utilizes semi- cylinder 14 ' ' ' which does not contact the broad walls of the waveguide.

Abstract

An RF powered electrodeless lamp (9) utilizing an inductive tuner (14) in the waveguide (6) which couples the RF power (2) to the lamp cavity (10, 12), for reducing reflected RF power and causing the lamp (9) to operate efficiently.

Description

INDUCTIVE TUNERS FOR MICROWAVE DRIVEN DISCHARGE LAMPS
BACKGROUND OF THE INVENTION a. Field of the Invention This invention refers to the field of radio-frequency driven arc lamps in which the structure includes a closed waveguide, and particularly to those lamps which utilize a magnetron as the source of power.
b. Description of the Prior Art These lamps employ an ionizable medium enclosed in a sealed transparent envelope which produces visible light or ultraviolet light when excited by an intense microwave field. The lamp envelope or bulb is enclosed in a metal container or cavity which confines the microwaves while providing for the escape of the light, usually by means of a metal screen. Microwaves are admitted into the cavity through an aperture which connects to the adjoining waveguide, the other end of which couples to the magnetron.
Rf power from the magnetron travels through the waveguide to the cavity and excites the discharge lamp. Any power that is not absorbed by the lamp reflects back to the magnetron. The aperture defining the end of the cavity may be used to define a resonance in the cavity which intensifies the fields at the bulb to provide increased power absorption, thus reducing the reflected power. A magnetron is a self-excited oscillator with a direct connection between its resonator and the output load. Any reflection from the load has a strong effect on the performance, changing the operating frequency, the power output and the operating stability. Strong reflections at a particular phase known as the "sink" reduce the stored energy in the magnetron's resonator, causing instability and frequency jumping.
The lamp itself places several different requirements on its power source. Before ionization, gases in the bulb do not absorb microwave power. The electric field intensity within the bulb must be built up to a high level to achieve breakdown. Once ionization occurs, the bulb must heat to evaporate any condensed fill materials. The impedance of the bulb is much lower than the non-ionized case, and changes as the bulb heats, bringing the condensates into the discharge. And finally the long term operating condition is reached in which light output efficiency is the dominant concern.
These impedance changes result in a variety of reflected values at the magnetron. The designer can adjust the aperture of the cavity, the length of the waveguide and may add a variety of tuning elements into the waveguide. The goal is to keep the high reflection before ionization away from the sink, to avoid frequency-jumping during the warm-up cycle and to provide a good match with stable characteristics during long-term operation. Other considerations may also enter into the design. The product needs to be economical, compact in size, durable, and reproducible. Cost prevents the use of isolators. Compact size holds the waveguide to a minimum length.
While many types of irises and posts are well-known in microwave design, the tuning element frequently used in microwave arc lamps is the capacitive screw or a fixed height knob of the same size. This has the advantage of attaching to only one wall and is more easily installed than a post which must contact two opposite walls. When a waveguide length (between the magnetron antenna and the coupling slot) greater than half a guide-wavelength is available, this capacitive tuner may be used to match a moderate mismatch or any phase. The tuner has two effects. The reflection coefficient is added to the reflection coefficient of the load beyond it. Secondly, the effective length of the waveguide is increased by a small amount.
SUMMARY OF THE INVENTION In the course of making a new lamp design, the cavity and the coupling iris were established. The waveguide length and magnetron position were also established. However, the impedance match was not optimum and the waveguide length (referred to in the preceding paragraph) was less than half a wavelength. Attempts to add a capacitive tuner showed that it was unsuitable, the best location being directly above the magnetron antenna.
An inductive tuner was placed on the side wall of the waveguide between the magnetron and the cavity aperture. A metal protrusion at the side of a waveguide acts like an inductive iris, raising the cutoff frequency of the waveguide at its location. Thus, the tuner provides a reflection coefficient with an inductive phase and shortens the effective length of the waveguide a small amount. The lamp design operates efficiently with this tuner. The inductive tuner may be a single block, semi-cylinder, or hemisphere or combination thereof attached to one side wall, or two such objects may face each other on opposite walls. These shapes are appropriate where the tuners are to be installed in a waveguide after it is built, as for example, by screws, soldering or welding.
The tuner may also be molded into the waveguide wall. Depending upon the method of construction it may be advantageous to form the tuner to join to the upper and/or lower broad wall of the waveguide as a thick iris.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic representation of a microwave lamp. Figure 2 illustrates an inductive tuner in the form of a single block. Figure 3 illustrates an inductive tuner in the form of two blocks which face each other on opposite waveguide walls.
Figure 4 illustrates an inductive tuner in the form of a semi- cylinder contacting the broad walls of a waveguide. Figure 5 illustrates an inductive tuner in the form of a semi- cylinder which does not contact the broad walls of a waveguide.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Figure 1, a microwave lamp is shown. Magnetron 2 has antenna 4 which protrudes into closed waveguide 6. At the other end of the waveguide, coupling slot 8 is located, which couples microwave power into the resonant cavity defined by bottom 10 and screen 12 in which bulb 9 is located. In accordance with the invention, inductive tuner 14 is attached to a side wall of the waveguide.
It is noted that the waveguide has broad walls and narrow walls (side walls) . Since the magnetic field is high at the side walls, a metal protrusion placed there will act as an inductive tuner.
In any given lamp, the location of the tuner as well as its size and shape are determined by experimentation, with the aid of a network analyzer. As known to those skilled in the art, the network analyzer is first calibrated with the aid of a sliding short. The impedance is then observed with the lamp in the starting and running conditions without a tuner. If significant reflection is present when the lamp is at operating temperature a tuner of trial size and shape is used and its position changed to determine the position of optimum operation. If significant reflection is still present, the size and/or shape of the tuner is varied, and various positions again tried.
In the embodiment of Figure 1, rectangular waveguide 6 is 1.7" high, 2.84" wide, and 4.8" long on the inside. The distance from the middle of the tuner to the slot end of the waveguide is about 1 7/8", and the tuner is about 5/8" wide, 1 1/4" long, and has a thickness of about .35". The coupling slot 8 is 2 3/8" long and .53" wide. The microwave cavity is 2.93" in diameter and 6.2" tall. The bulb 9 is 35 mm inside diameter and contains a fill of sulfur and rare gas such as argon.
Both the waveguide and the tuner may be made of aluminum. It is preferable to make the waveguide and the tuner of the same material to minimize corrosion.
A motor rotates both the shaft 20 to which bulb 9 is attached and blower wheel 22 which provides air for cooling the magnetron.
Figure 2 is a cut-away detail of waveguide 6 of Figure 1, and shows the inductive tuner in the form of metal block 14. Figure 3 shows an alternative embodiment wherein two such blocks 14'a and 14'b face each other on opposite waveguide walls.
Figure 4 shows a further alternative embodiment which utilizes a protrusion in the form of semicylinder 14" which contacts the top and bottom broad walls 30 and 32 of the waveguide.
Figure 5 shows still a further embodiment which utilizes semi- cylinder 14 ' ' ' which does not contact the broad walls of the waveguide.
While the invention has been disclosed employing illustrative embodiments, it is to be understood that variations will occur to those skilled in the art. For example the tuners may have different shapes than illustrated, or cylindrical posts may be used. The scope of the invention is defined by the following claims.

Claims

1) An RF powered electrodeless lamp comprising, means for generating RF power, a bulb containing a discharge forming medium disposed in a cavity, a waveguide for coupling said RF power to said cavity, said waveguide having a coupling slot, and an inductive tuner disposed in said waveguide.
2) The lamp of claim 1 wherein said inductive tuner comprises at least one metal protrusion disposed on a waveguide wall.
3) The lamp of claim 2 wherein said waveguide has narrow walls and broad walls, wherein said metal protrusion is disposed on a narrow wall.
4) The lamp of claim 3 wherein said at least one metal protrusion comprises a metal block.
5) The lamp of claim 4 wherein said metal block is rectangular.
6) The lamp of claim 5 wherein said at least one metal block comprises two rectangular metal blocks disposed on opposite waveguide walls. 7) The lamp of claim 4 wherein said at least one metal block comprises a semi-cylindrical metal block.
8) The lamp of claim 7 wherein said metal block contacts said broad walls at its extreme ends.
9) The lamp of claim 7 wherein said metal block at its extreme ends does not contact said broad walls.
10) The lamp of claim 2 wherein said means for generating RF power is a magnetron having an antenna and wherein the waveguide length from the antenna to said coupling slot is less than half a wavelength.
11) An RF powered electrodeless lamp comprising means for generating RF power, a bulb containing a discharge forming medium disposed in a cavity, a waveguide for coupling said
RF power to said cavity, and inductive tuning means disposed in said waveguide for minimizing power which is reflected back to said means for generating RF power.
12) The lamp of claim 11 wherein said waveguide has a coupling slot.
PCT/US1997/001106 1996-01-26 1997-01-24 Inductive tuners for microwave driven discharge lamps WO1997027611A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
IL12529597A IL125295A0 (en) 1996-01-26 1997-01-24 Inductive tuners for microwave driven discharge lamps
JP9527008A JP2000504144A (en) 1996-01-26 1997-01-24 Induction tuner for microwave driven discharge lamp
EP97903942A EP1016124A4 (en) 1996-01-26 1997-01-24 Inductive tuners for microwave driven discharge lamps
AU18372/97A AU1837297A (en) 1996-01-26 1997-01-24 Inductive tuners for microwave driven discharge lamps

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US1067196P 1996-01-26 1996-01-26
US60/010,671 1996-01-26

Publications (1)

Publication Number Publication Date
WO1997027611A1 true WO1997027611A1 (en) 1997-07-31

Family

ID=21746850

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1997/001106 WO1997027611A1 (en) 1996-01-26 1997-01-24 Inductive tuners for microwave driven discharge lamps

Country Status (12)

Country Link
US (1) US5977712A (en)
EP (1) EP1016124A4 (en)
JP (1) JP2000504144A (en)
KR (1) KR19990081919A (en)
CN (1) CN1055783C (en)
AU (1) AU1837297A (en)
CA (1) CA2244166A1 (en)
HU (1) HUP9901854A3 (en)
IL (1) IL125295A0 (en)
TW (1) TW388909B (en)
WO (1) WO1997027611A1 (en)
ZA (1) ZA97606B (en)

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KR100442374B1 (en) * 2001-07-20 2004-07-30 엘지전자 주식회사 Microwave lighting system
EP1612842A1 (en) 2004-06-30 2006-01-04 Lg Electronics Inc. Waveguide system for electrodeless lichting device
EP1458011A3 (en) * 2003-03-11 2006-05-10 Lg Electronics Inc. Electrodeless lamp system

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JP3580205B2 (en) * 2000-01-18 2004-10-20 ウシオ電機株式会社 Electromagnetic energy excitation point light source lamp device
AU2001255308A1 (en) * 2000-04-26 2001-11-07 Cornell Research Foundation Inc. Lamp utilizing fiber for enhanced starting field
US6922021B2 (en) * 2000-07-31 2005-07-26 Luxim Corporation Microwave energized plasma lamp with solid dielectric waveguide
KR20030026806A (en) * 2001-09-28 2003-04-03 주식회사 엘지이아이 Apparatus and method for intercepting leakage of microwave
US6577074B1 (en) * 2001-12-28 2003-06-10 Fusion Uv Systems, Inc. Lighting system
WO2005015607A1 (en) * 2003-08-08 2005-02-17 Expantech Co., Ltd. Plasma lamp and manufacturing method thereof
KR100668259B1 (en) * 2004-11-09 2007-01-12 전제일 Electrodeless Cascade Multiple Fluorescent Lighting Device Using Microwave
KR101943321B1 (en) * 2012-11-12 2019-01-29 엘지전자 주식회사 Lighting apparatus
CN103165401B (en) * 2013-02-06 2015-11-04 湖北源光电器科技有限公司 A kind of electrodeless Metal halogen lamp of microwave plasma of miniaturization
CN109553155A (en) * 2018-12-07 2019-04-02 四川麦克优威环保科技有限责任公司 Electrodeless ultraviolet sterilization device for sewage treatment plant

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
KR100442374B1 (en) * 2001-07-20 2004-07-30 엘지전자 주식회사 Microwave lighting system
EP1458011A3 (en) * 2003-03-11 2006-05-10 Lg Electronics Inc. Electrodeless lamp system
EP1612842A1 (en) 2004-06-30 2006-01-04 Lg Electronics Inc. Waveguide system for electrodeless lichting device
EP1612842B1 (en) * 2004-06-30 2010-10-27 LG Electronics, Inc. Waveguide system for electrodeless lighting

Also Published As

Publication number Publication date
AU1837297A (en) 1997-08-20
IL125295A0 (en) 1999-03-12
EP1016124A1 (en) 2000-07-05
TW388909B (en) 2000-05-01
US5977712A (en) 1999-11-02
JP2000504144A (en) 2000-04-04
EP1016124A4 (en) 2000-07-05
CA2244166A1 (en) 1997-07-31
ZA97606B (en) 1997-09-16
CN1055783C (en) 2000-08-23
KR19990081919A (en) 1999-11-15
HUP9901854A2 (en) 1999-09-28
CN1209904A (en) 1999-03-03
HUP9901854A3 (en) 2002-04-29

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