WO1998023133A1 - Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference - Google Patents
Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference Download PDFInfo
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- WO1998023133A1 WO1998023133A1 PCT/US1997/020965 US9720965W WO9823133A1 WO 1998023133 A1 WO1998023133 A1 WO 1998023133A1 US 9720965 W US9720965 W US 9720965W WO 9823133 A1 WO9823133 A1 WO 9823133A1
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- waveguide
- frequency
- absorber
- electrodeless lamp
- resonant
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/24—Circuit arrangements in which the lamp is fed by high frequency ac, or with separate oscillator frequency
Definitions
- the present invention pertains to improvements in methods and apparatus for powering an electrodeless lamp with reduced Radio Frequency Interference (RFI).
- RFID Radio Frequency Interference
- This invention has particular, although not limited, utility in lamps of the types disclosed in U.S. Patent Numbers 5,504,391 (Turner et al), 5,448,135 (Simpson ), 5,404,076 (Dolan et al), 4,894,592 (Ervin et al), 4,859,906 (Ury et al), and 4,359,668 (Ury); the disclosures of these patents are incorporated herein by reference.
- Electrodeless lamps of the type with which the present invention is concerned include a light transmissive envelope containing a plasma-forming medium known as fill.
- a microwave or Radio Frequency (RF) energy source has its output energy coupled to the envelope via a waveguide to excite a plasma in the fill, resulting in the discharge of light from the envelope.
- Fig. 1 schematically illustrates one of the many possible configurations for an electrodeless lamp of the type with which the present invention is concerned.
- a lamp module 20 includes a magnetron 22 or some other source of RF or microwave electromagnetic energy. Energy from the magnetron 22 is coupled to a waveguide 24 via a coupling antenna 28 and into a screen cavity 30, in which a bulb 32 is disposed.
- Bulb 32 includes a generally spherical discharge envelope 34.
- the bulb 32 has a high pressure fill material contained within its discharge envelope 34 such as, for example, the material described in the above-referenced Dolan et al patent.
- Bulb envelope 34 is made of quartz or some other suitably transparent material.
- the screen cavity 30 is made from a conductive mesh or screen material opaque to RF or microwave radiation but transparent to light radiation.
- the waveguide 24 directs the electromagnetic energy generated by the magnetron 22 into the screen cavity 30, exciting the fill atoms of noble gas (e.g., xenon, argon, krypton, etc.) in bulb 32, which is initially at room temperature, to effect discharge of electrons.
- the discharged electrons collide with other fill atoms causing a further discharge of electrons, thereby increasing the total population of free electrons.
- the increased population of free electrons results in increased collisions and increased temperature, and other atoms of solid or liquid fill material, such as sulfur, mercury, etc., are vaporized and emit the desired light radiation.
- a coaxial resonator 26 includes screen 30 as an outer conductor, a center conductor 36 which preferably is hollow to carry cooling air, bulb 32, and coupling loop 40 which is used to provide a high voltage, exciting the electrodeless lamp bulb at a high energy density.
- Power is coupled from the waveguide to the resonator by a coupling loop 40 in which a horizontal RF magnetic field enters notch 38 behind conductor 36, inducing current in the base of the center conductor 36.
- Impedance matching in this context, refers to matching the bulb's impedance at full operating temperature to that of waveguide 24 whereby the impedance at antenna 28 is equal to the characteristic impedance for an RF circuit specified by the magnetron's manufacturer.
- a mismatch in impedance causes reflected RF energy to propagate back from the area of the mismatch and produces a higher Voltage Standing Wave Ratio (VSWR) than for a matched RF circuit.
- VSWR Voltage Standing Wave Ratio
- the lamp RF circuit includes the coupling antenna 28, the waveguide 24, the resonator 26 including the screen cavity 30 containing bulb 32, the RF load to be excited.
- the VSWR is within acceptable limits at the selected frequency of operation for the magnetron, according to specifications provided by the manufacturer of the magnetron.
- the magnetron is adversely affected by the short waveguide and resonator 26 and exhibits unexpected behavior. Instead of the single selected frequency, multiple, spurious frequencies are observed in the magnetron output spectrum.
- lamp performance is adversely affected in two ways; the lamp light flickers in an unacceptable manner and the spurious frequencies produced are outside the 2400 MHZ to 2500 MHZ ISM band allocated under governmental guidelines for RF spectrum management. Spurious signals above and below the allocated band have been observed simultaneously. The frequencies produced change with the length of the waveguide between the magnetron and the lamp bulb.
- the magnetron (together with the lamp RF circuit) may also oscillate at a second or third widely separated frequency, 30 MHZ to 100 MHZ to either side of the selected frequency, when a VSWR of 20:1 or greater is present at the widely separated frequency.
- RFI Radio- Frequency Interference
- Another object of this invention to provide an improved compact waveguide for eliminating problems with magnetron frequency pulling.
- a lamp waveguide with an integral frequency selective attenuation has been developed; this waveguide includes resonant absorbers positioned within the waveguide to absorb spurious out-of-band RF energy. The absorbers have a negligible effect on energy at the selected frequency used to excite the plasma in the lamp.
- one or more thin slabs of lossy energy absorbing material is affixed to the sidewalls of the waveguide at a distance approximately one quarter wavelength from an end wall of the waveguide; the position of each slab is chosen as a function of the guide wavelength of the spurious signal.
- the positioning of the lossy material optimizes absorption of power from the spurious signal; otherwise, the spurious signal behaves like a standing wave within the waveguide.
- a quantity of lossy absorber material sufficient to partially terminate the waveguide is used in conjunction with a band rejection waveguide filter that is tuned to the selected operating frequency.
- one or more tuned microstrip energy receiving absorbers are tuned and strategically positioned within the waveguide to absorb the spurious signal energy. All three embodiments absorb negligible energy at the selected frequency and so do not significantly diminish the energy efficiency of the lamp.
- an energy absorber is disposed within the waveguide.
- a broadband lossy absorber is made resonant, or frequency selective, by virtue of the position of the absorber within the waveguide.
- a band rejection filter is used to selectively allow only spurious energy to reach an (otherwise broadband) absorber, thus the absorber is resonant, or frequency selective, by virtue of its use in conjunction with a band rejection filter.
- a frequency selective microstrip absorber is disposed within the waveguide. In each of the three embodiments, therefore, the absorbers are tuned to absorb energy at the frequency of the spurious signal and so, for purposes of nomenclature, each of the three embodiments is deemed to include a resonant absorber.
- Fig. 1 schematically illustrates a cross-section side view of one example of an electrodeless lamp of the type with which the present invention is utilized.
- Fig. 2 is a Smith chart diagram illustrating the impedance of a resonant RF circuit with an ideal resonator matched to a waveguide at the resonant frequency.
- Fig. 3 is a second Smith chart diagram illustrating the effect of adding a one wavelength long section of waveguide to the resonant RF circuit charted in Fig. 2.
- Fig. 4 is a Rieke diagram illustrating observed magnetron output power and frequency as a function of load conductance (and susceptance), for a fixed magnetic field and anode current.
- Fig. 5 is a schematic perspective illustration of the lamp of the present invention with slabs of magnetically absorptive material in the waveguide.
- Fig. 6 is a schematic perspective illustration of a second embodiment of the lamp of the present invention with a bandstop filter element in the waveguide.
- Figs 7a, 7b, 7c, 7d, 7e, 7f, 7g and 7h are schematic cross-sectional illustrations of bandstop filter elements for use in the waveguide of the present invention.
- Fig. 8 is a schematic perspective illustration of a third embodiment of the lamp of the present invention, having a tuned resonant microstrip filter element situated in the waveguide.
- Figs 9a, 9b and 9c are schematic plan-view illustrations of microstrip filter elements for use in the third embodiment of the waveguide of the present invention.
- the mechanism by which unwanted frequency pulling occurs may be understood by considering the impedance of a resonant circuit portrayed on a polar impedance diagram (or Smith Chart), as shown in Fig. 2.
- the Smith Chart is a graphical representation of the impedance of a transmission line (or waveguide), generally. For a given reference position in a waveguide, impedance is normalized to a standard value (e.g., 50 ohms) and then may be plotted as a point.
- the Smith chart is useful for modeling how impedance changes as the reference position is moved toward the generator (i.e., the magnetron 22) or toward the load (i.e., the bulb 32).
- the Smith Chart is also useful to plot impedance changes for a given reference position within a waveguide, as a function of frequency; this is the purpose of Figs. 2 and 3.
- Fig. 2 it is shown that at a reference plane located at the loop coupling resonator 26, a resonant circuit impedance appears as a circle 60, tangent to the edge of the chart 62 at zero impedance.
- the length of the transmission line joining the magnetron to the resonator must place zero impedance point 62 in the "sink" phase of the magnetron's performance characteristic.
- the transmission line length also includes a portion inside the magnetron 22 between the antenna 28 and the anode resonator (i.e., the point inside the magnetron at which the oscillation frequency is determined). Reflections from the load (i.e., bulb 32) experience a phase shift in the transmission line length, the phase shift increasing as a function of frequency.
- Fig. 2 illustrates the impedance plot of an ideal resonator matched to the incoming transmission line or waveguide at resonant frequency f 0 shown at point 64, with a loaded bandwidth of ⁇ 25 MHZ. Impedances for offset frequencies at multiples of ⁇ 25 MHZ are shown (as well as for ⁇ 12.5 MHZ, at points 66 and 68; ⁇ 12.5 MHZ is the unloaded bandwidth for such a resonator).
- Fig. 3 there is illustrated the effect of adding a section of WR-340 waveguide having a length of one full wavelength at 2450 MHZ, assumed herein to be the resonance frequency f 0 . Frequencies below f 0 are shifted counterclockwise while frequencies above f 0 are shifted clockwise, crossing the center line of the chart 70 for both cases.
- the Rieke diagram is a chart showing changes in the output power and frequency of magnetron 22 as a function of load impedance, at a reference plane corresponding to the antenna 28.
- the directional arrow 71 indicates movement toward the load.
- the concentric circles, 72a, 72b, 72c, are lines of constant VSWR and increase with increasing diameter; line 72a corresponds to a VSWR of 5.0, line 72b to a VSWR of 4.0, line 72c to a VSWR of 3.0, and so forth.
- the center of the chart corresponds to a VSWR of 1.0, a perfect impedance match.
- the curved lines of increasing radius, 73a, 73b, 73c are lines of constant output power and decrease with increasing radius; line 73a corresponds to a power of 900 watts, line 73b to a power of 850 watts, line 73c to a power of 800 watts, and so forth.
- the region of higher power 75 is called the sink region and represents the greatest coupling to the magnetron and the highest efficiency. Operation in the sink region, however, typically results in reduced frequency stability.
- the lower power region 76 is where the magnetron is lightly loaded; it is expected that the buildup of oscillations will be more stable there. For magnetrons of the type used in this lamp, data is supplied only for VSWR values of 5:1 to 10:1.
- the mechanism for generation of spurious RFI signals may be similar, since the unwanted signals change frequency when the waveguide lengths are changed.
- Another factor contributing to RFI generation in the larger lamps is the use of unfiltered high voltage Direct Current (DC) power supplies for driving the magnetron.
- DC Direct Current
- Small lamps with narrow resonant bandwidths are apt to require a more highly filtered DC supply in order to maximize bulb coupling.
- Larger lamps can provide high efficiency in spite of the frequency modulation (tens of MHZ) caused by unfiltered operation. Unwanted and out-of-band spurious signals can be produced during periods of low or rapidly changing magnetron supply current.
- a small amount of attenuation is introduced into waveguide 24, thereby reducing the VSWR of the waveguide for spurious signals.
- the unwanted oscillation is reduced to a low amplitude (or preferably eliminated completely); this is so because the impedance contour in Fig. 3 shrinks toward the center and no longer coincides with the points on the frequency pulling characteristic in the region of instability.
- the use of attenuation within the waveguide sacrifices at least some of the useful (forward) power which would otherwise be used to drive the lamp bulb 32. It has been determined experimentally that, for prototypes of the first embodiment of the present invention, this reduction in forward power is in the range of 5% and so is negligible.
- the attenuation is made frequency selective to reduce the impact of the attenuation on the system efficiency. In all cases, it is desirable to maximize the loading at the out-of-band frequencies while minimizing the loading or loss at the selected frequency of operation.
- Fig. 5 there is illustrated a first preferred embodiment for the present invention specially adapted for use with the small bulbs; in this embodiment, broadband attenuators are used within waveguide 24.
- One or more attenuating inserts 80, 82 are placed on the walls of the waveguide 24 at selected locations 86, 88 corresponding to expected high intensity locations in the electric or magnetic field.
- One such location 86 is on the sidewall, as illustrated in Fig. 5.
- the end wall of the waveguide 90 is electrically similar to a short circuit, since the resonant circuit impedance of the loop is nearly a short circuit at the unwanted frequency. Therefore, the electric (E) field is vertical and is at a maximum in the center 92 of the waveguide.
- the magnetic (H) field is horizontal and is at a maximum tangent to the sidewalls 86, 88. Both these maxima occur a quarter guide wavelength away from the end wall 90 (this is a function of the spurious signal wavelength, not the selected frequency wavelength). Both the E and H fields form standing waves and have a nearly doubled intensity at the quarter wavelength sites 86, 88. Power absorption for the spurious signal is thus nearly quadrupled at the spurious signal quarter wavelength locations 86, 88 as compared to absorption of the forward wave of the nearly matched center frequency signal.
- An electric field attenuation element i.e., a lossy absorber of E field power
- a lossy absorber of E field power is preferably thick, in order to couple the E field, since it is perpendicular to the top and bottom waveguide surfaces.
- a magnetic field loss element, 80 can be very thin however. This thinness, and the fact that the magnetic absorber 80 is adhered to the thermally conductive wall 86, improves heat transfer of the energy absorbed from the H field to the mounting wall 86.
- two thin slabs 80, 82 of lossy magnetic material are attached to opposite side walls 86, 88 of the waveguide 24 using a thermally conductive adhesive. Heat generated in the lossy material is conducted to the waveguide walls.
- the absorber material contains a uniform dispersion of a lossy iron compound in a rubber base. The rubber prevents thermal expansion stress from separating the insert from the metal waveguide wall.
- Blocks of silicon carbide, an electric field absorber have also been effective in absorbing the energy of the spurious signals. Higher operating temperatures can be tolerated with the silicon carbide material. However, the lossy iron compound in the rubber base is preferred because it is possible to control the power absorption properties for the iron more closely than the silicon carbide material.
- a suitable magnetic absorber is an iron powder suspended in an elastomeric material such as silicone rubber. A sample 1 3/8" square by 0.15" thick absorbs about 2 percent of forward power at 2450 MHZ, with or without presence of a spurious standing wave, when installed on a side wall of a WR-340 waveguide.
- the second embodiment is illustrated in Fig. 6.
- a narrow-band bandstop (or band rejection) filter 100 is placed between the magnetron coupling antenna 28 and a lossy absorber or attenuator 102. Direct transmission from the magnetron 22 to the lamp resonator 26 is maintained.
- the bandstop filter 100 may take the form of a wire loop suspended in the middle of the waveguide between the magnetron antenna 28 and the end wall of the waveguide opposite lamp 104.
- a microwave load in the form of a large absorber 102 is mounted on this end wall 104.
- the loop 100 is resonant at the magnetron center frequency and effectively functions as a short circuit in the waveguide at the filter plane 108.
- the plane of loop 108 is positioned at the same distance from magnetron coupling antenna 28 as the back wall of the unaltered waveguide 109, as illustrated in Fig. 5.
- the back wall 109 is electrically a short circuit.
- the band rejection filter 100 positioned in plane 108, this end of the waveguide provides an electrical short circuit for the signal at the selected frequency.
- a highly resonant current flows in loop filter 100, causing some loss at the selected frequency.
- Spurious signals at the out-of-band frequencies pass through the band rejection filter 100 and go to the absorber 102 and are at least partially absorbed by absorber 102, preferably a block of silicon carbide.
- bandstop filter as illustrated in Figs. 7a - 7h, may also be employed.
- the filter shown in Fig. 7a is 3.4" long to fit WR-340 waveguide.
- the height is 0.75" and the thickness is 0.120".
- the loop is 2.232" inside the oval.
- the parallel bars are preferably rounded in cross-section to prevent arcing across the 0.5" gap. An earlier version with a 0.25 gap was prone to arcing.
- a vertical rod 132 disposed near the sidewall 88 of waveguide 24 has a resonant frequency determined by its length 140 and coupling is determined by its displacement 142 from the waveguide wall 88.
- a horizontal rod 146 attached to sidewall 88 with asymmetrical tip 148 may also serve as a bandstop filter.
- An off-center screw (not shown), or a small tilt or bend (not shown) can be used to tune a filter having a rod element.
- Fig. 7e illustrates a loop type resonator cut in half to resemble a tuning fork 152.
- Fig. 7g shows a wire loop joined to the top or bottom waveguide wall.
- the filter shape may be rectangular, elliptical or oval. Any of these variations may also be encased in a dielectric material to prevent arcing within the waveguide.
- waveguide end 104 must be extended to separate absorber 102 from the fields of the filter.
- the filter is primarily blocking the TE 10 mode of waveguide propagation. Near field energy at the selected frequency may pass through some of the embodiments illustrated in Figs. 7a-7h such as the vertical rod of Fig. 7f, more than others, such as the centered oval loop illustrated in Fig. 7c. This may necessitate an extension of the distance 160 between absorber 102 and filter 100, as illustrated in Fig. 6.
- the band rejection filter embodiment stops the production of out-of-band spurious signals; however, it also modifies the resonant tuning of the lamp, adding additional complexity to the design and perhaps increasing manufacturing difficulties.
- one or more partially coupled lossy resonant circuits 200 tuned to the spurious out-of-band frequencies, are placed in the waveguide at high field strength locations for those out-of-band frequencies, as above.
- the lossy resonant circuits 200 have a controlled (i.e., tuned) internal loss which absorbs the greatest power at the spurious frequency.
- This embodiment is especially useful for the lamp assemblies with wideband magnetrons where spectral separation (between the selected frequency and spurious frequency) of greater than 100 MHZ is likely to occur.
- the resonant circuit 200 includes a microstrip transmission line upper conductor 202 etched on a dielectric substrate 204.
- the back of the resonant circuit 200 is fully covered with metal and is attached to contact the wall of the waveguide. This insures predictable resonant frequency.
- the back foil could be omitted but any air space between the dielectric and the metal wall would raise the resonant frequency.
- the microstrip resonator 200 is a transmission line confining current and electric field within the dielectric substrate area bounded by the upper conductor 202. If the upper conductor 202 were short-circuited to the ground plane at both ends, the length for resonance would be equal to one-half wavelength in the dielectric substrate 204. Preferably, the ends are not short-circuited and there is a fringing-field capacitance at each end extending the effective length. Thus, the resonant length is approximately one-half wavelength minus twice the thickness of dielectric substrate 204.
- the outer surface of the conductor 202 shields the resonator from external fields. The antenna functions as though the gaps at the ends were slots admitting fields to the interior. Thus, external coupling is proportional to the product of thickness of dielectric substrate 204 and the width of the upper conductor 202. The resonant bandwidth of the resonator is determined by losses on the metal surfaces and in the dielectric plus the coupling to external fields.
- a microstrip receiving antenna is connected to a receiver by a microstrip conductor on its surface or by a lead wire through the substrate and ground plane.
- the impedance of the external load determines the performance of the microstrip antenna.
- the microstrip antenna losses only reduce antenna efficiency.
- the losses within microstrip resonator 200 are the load and determine impedance and bandwidth.
- the resonant microstrip circuit 200 is attached to a wall of the waveguide where currents at the resonant frequency are strong and run parallel to the length of upper conductor 202.
- coupling can be reduced by use of a thinner dielectric substrate and a narrower upper conductor, each requiring a change in circuit length.
- coupling of a particular board may be reduced by rotating the upper conductor toward a direction perpendicular to the waveguide surface currents.
- a resonant microstrip absorber has been built by photolithography and etching as shown in Fig. 9a.
- the substrate material was FR-4, a common circuit board material with moderate microwave loss.
- the board was 1.54" by 1" and 0.06" thick.
- the conducting pattern was 1.388" by 0.788" with a 0.130" hole for a mounting screw.
- Tests with the board on a WR-340 waveguide side wall showed the circuit to be resonant at 2079 MHZ with an under coupled resonance with reflection coefficient of 0.14 at resonance. Loaded bandwidth was 55 MHZ and unloaded Q was 65. At least half the incident power was absorbed by the filter from 2052 to 2106 MHZ.
- the loss in lamp efficiency or loss in forward power is reduced to approximately 1%, a further improvement over the efficiency for the first embodiment of Fig. 5 or the second embodiment of Fig. 6.
- Narrow bandwidth filters require a lower dielectric loss substrate material than FR-4, e.g., Teflon-fiberglass composite, or the like.
- a small piece of carbon-coated card could be placed on top of the upper conductor 202 near the center thereof, placed to overhang the edges, such that some of the current on the underside of conductor 202 is spread to the resistive surface, increasing loss.
- a gap may be included in the conductor under the resistor card.
- Magnetic loss material may similarly be placed adjacent to the edge, at the high current center of conductor 202. The greatest effectiveness is obtained if magnetic loss material is used in place of some of the substrate thickness between conductor 202 and the ground plane.
- FIG. 9a shows a constant width strip.
- the metal is etched back away from all edges of the substrate to allow the fringing fields to be contained within the dielectric.
- the corners of the strip are rounded to reduce peak electric fields which can occur at square corners, thus reducing the likelihood of arcing, should a high power signal occur at the resonant frequency.
- a hole is provided at the center for a fastener to attach the resonator to the waveguide wall.
- Frequency is determined by the length of the metal strip, augmented by fringing fields at its tips as is well known in the patch or microwave antenna art.
- the length of strip required for a particular frequency to be absorbed may be reduced by shaping it as an hourglass shape as illustrated in Fig. 9b.
- the strip ends 210, 212 are capacitive while the center 214 is inductive.
- a narrow center 214 has more inductance and thus the resonant frequency and coupling are reduced.
- the resonant absorbers 200 are made by common photo-etching methods to obtain highly repeatable properties, well suited to large quantity manufacture. If a lamp requires suppression of several frequencies, multiple strips 216, 218 may be etched on a single dielectric substrate 204 (as illustrated in Fig. 9c), thereby providing a multi-frequency resonant absorber which is simple to install in a waveguide.
- resonant filters described herein are chosen for their compact size and ease of manufacture. Other forms of filters are well known in the literature. Some of these could also be incorporated to reduce interference; however, the size of the lamp system might thus be increased. For example, rectangular cavities with dimensions comparable to the waveguide cross-section could be coupled to either the narrow or the broad wall of the waveguide through appropriate slots.
- an energy absorber is disposed within the waveguide.
- a broadband lossy absorber 80 is made resonant, or frequency selective, by virtue of the position of the absorber within the waveguide.
- a band rejection filter is used to selectively allow only spurious energy to reach the (otherwise broadband) absorber 102, thus absorber 102 is resonant, or frequency selective, by virtue of its use in conjunction with filter 100.
- a frequency selective microstrip absorber 200 is disposed within the waveguide.
- the absorbers 80, 102 and 200 are tuned to absorb energy at the frequency of the spurious signal and so, for purposes of nomenclature, each of the three embodiments includes a resonant absorber.
- the structure and method of the present invention is specially adapted to solve the problem described above in compact electrodeless lamp RF circuits, but is not limited to use with electrodeless lamps.
- Compact waveguide structures with highly resonant RF circuits may be used in conjunction with magnetrons in a number of applications, such as in microwave ovens or compact microwave transmitters.
- the resonant absorbers of the present invention can be utilized in such waveguides; any of the three preferred embodiments may be employed in overcoming problems with magnetron frequency pulling and related problems with RFI, as discussed above.
- the foregoing describes the preferred embodiments of the present invention along with a number of possible alternatives. A person of ordinary skill in the art will recognize that modifications of the described embodiments may be made without departing from the true spirit and scope of the invention. The invention is therefore not restricted to the embodiments disclosed above, but is defined in the following claims.
Abstract
Description
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU52608/98A AU5260898A (en) | 1996-11-22 | 1997-11-18 | Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference |
EP97947557A EP0940062A4 (en) | 1996-11-22 | 1997-11-18 | Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference |
JP52378998A JP2001504634A (en) | 1996-11-22 | 1997-11-18 | Method and apparatus for powering an electrodeless lamp with reduced RF interference |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/754,858 | 1996-11-22 | ||
US08/754,858 US5910710A (en) | 1996-11-22 | 1996-11-22 | Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference |
Publications (1)
Publication Number | Publication Date |
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WO1998023133A1 true WO1998023133A1 (en) | 1998-05-28 |
Family
ID=25036667
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1997/020965 WO1998023133A1 (en) | 1996-11-22 | 1997-11-18 | Method and apparatus for powering an electrodeless lamp with reduced radio frequency interference |
Country Status (6)
Country | Link |
---|---|
US (1) | US5910710A (en) |
EP (1) | EP0940062A4 (en) |
JP (1) | JP2001504634A (en) |
AU (1) | AU5260898A (en) |
TW (1) | TW377452B (en) |
WO (1) | WO1998023133A1 (en) |
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- 1997-11-18 AU AU52608/98A patent/AU5260898A/en not_active Abandoned
- 1997-11-18 WO PCT/US1997/020965 patent/WO1998023133A1/en not_active Application Discontinuation
- 1997-11-18 EP EP97947557A patent/EP0940062A4/en not_active Withdrawn
- 1997-11-21 TW TW086117463A patent/TW377452B/en active
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WO2002011181A1 (en) * | 2000-07-31 | 2002-02-07 | Luxim Corporation | Plasma lamp with dielectric waveguide |
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CN107548222A (en) * | 2017-07-25 | 2018-01-05 | 华东师范大学 | A kind of wireless activation miniaturization microwave micro-plasma array source based on Meta Materials |
CN107548222B (en) * | 2017-07-25 | 2019-04-26 | 华东师范大学 | A kind of wireless activation miniaturization microwave micro-plasma array source based on Meta Materials |
Also Published As
Publication number | Publication date |
---|---|
AU5260898A (en) | 1998-06-10 |
TW377452B (en) | 1999-12-21 |
JP2001504634A (en) | 2001-04-03 |
US5910710A (en) | 1999-06-08 |
EP0940062A1 (en) | 1999-09-08 |
EP0940062A4 (en) | 2000-02-02 |
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