Source: http://www.google.com/patents/US8035295?dq=7,007,239
Timestamp: 2017-10-23 02:52:08
Document Index: 618474617

Matched Legal Cases: ['Application No. 143', 'Application No. 297', 'Application No. 299', 'Application No. 318', 'Application No. 334', 'Application No. 407', 'Application No. 450', 'Application No. 545', 'Application No. 649', 'Application No. 821']

Patent US8035295 - Field-emission cathode, with optical control - Google Patents
The invention relates to an optically-controlled field-emission cathode, comprising a substrate (10, 20, 30, 40, 50, 60, 70, 80, 90, 100) having at least one conducting surface (11, 21, 31, 41, 51, 61, 71, 81, 91, 101) and at least one conducting emitter element (16, 26, 36, 46, 56, 66, 76, 86, 96, 106)...http://www.google.com/patents/US8035295?utm_source=gb-gplus-sharePatent US8035295 - Field-emission cathode, with optical control
Publication number US8035295 B2
Application number US 11/721,970
PCT number PCT/EP2005/056701
Also published as EP1825490A1, EP1825490B1, US20090261727, WO2006063982A1
Publication number 11721970, 721970, PCT/2005/56701, PCT/EP/2005/056701, PCT/EP/2005/56701, PCT/EP/5/056701, PCT/EP/5/56701, PCT/EP2005/056701, PCT/EP2005/56701, PCT/EP2005056701, PCT/EP200556701, PCT/EP5/056701, PCT/EP5/56701, PCT/EP5056701, PCT/EP556701, US 8035295 B2, US 8035295B2, US-B2-8035295, US8035295 B2, US8035295B2
Inventors Pierre Legagneux, Laurent Gangloff, Eric Minoux, Jean-Philippe Schnell, Frederic Andre, Dominique Dieumegard
Patent Citations (24), Non-Patent Citations (18), Classifications (17), Legal Events (2)
Field-emission cathode, with optical control
US 8035295 B2
1/ The cathode surface area must be reduced to dimensions significantly smaller than the wavelength of the microwave signal, so that all the points on the cathode surface emit in phase, and therefore the modulation depth of the total emitted current is not attenuated. However, the smaller the surface area, the lower the emitted current and the more the output power is limited.
2/ Furthermore, the need for the cathode to be biased with a high negative voltage with respect to the extraction grid imposes the presence of a galvanic insulation between the cathode and the outer conductor of the input coaxial guide which is grounded. This galvanic insulation can limit the performance at high power.
3/ Moreover, in microwave tube technology, the microwave is coupled with the input cavity of the tube by a connector that is difficult to miniaturize. This is a limitation on the miniaturization of the whole cavity, and consequently, a limitation on the optimum operation.
4/ Also, the bandwidth (in particular, the maximum frequency of operation of the cathode) is limited owing to the fact that the input signal is applied to an input impedance with a significant capacitive component.
Germanium or silicon or alloys of the two, with high concentrations of structural defects formed by irradiation with high-energy electrons (10−10 s).
Silicon implanted with gold
“Low-temperature” GaAs (carrier lifetime: 10−12 s),
Other III-V or “low-temperature” III-V alloys,
Poly-, micro- or nanocrystalline semiconductors (carrier lifetime: 10−9 s to 10−10 s).
Geometries favoring surface recombination of the carriers (dimensions smaller than the diffusion length of the carriers).
Low-temperature III-V materials is understood to mean, as is known, materials whose growth is carried out at an unusually low temperature in such a manner that an excess of V element is produced within them which, by segregating, form particularly efficient recombination regions.
Thus, according to the invention, the emitter or group of emitters, such as have just been described, are connected in series to a photoconducting device Dp as illustrated in FIGS. 3 a and 3 b.
In the diagram in FIG. 3 c, the photoconducting device having a conducting layer on its upper part can have lateral dimensions that are large in comparison with the dimensions of the emitter point. In this case, only the average field value E0 is modified when the photoconductor is illuminated, and it is modified at the most in a ratio. This situation is therefore not very favorable.
β ≈ h r ,
FIGS. 5 a and 5 b illustrate the case of a point on the surface of a localized conducting substrate of dimensions similar to that of the point. More precisely, FIG. 5 a shows a portion of cathode with a single emitter in the presence of a separate series resistor, located under the emitter, and through which the emission current flows. The equipotential RI rises rapidly above the conducting substrate, moving laterally away from the emitter. If the lateral extension of the upper metallization of the resistor is small (lower than the height of the emitter), the shape of the equipotentials above the emitter is similar to that of a shorter emitter, as can be seen in FIG. 5 b.
β ≈ h r × ( 1 - α RI hE 0 )
d h h = d β β = d E E = - α RI hE 0 ,
I = a E 2 exp - b E ,
d E E = d E 0 E 0 = - RI E 0 d ,
u = α d h .
Δ h h = Δβ β = Δ E E ≈ - α Δ ( RI ) hE 0 .
Δ h h = Δβ β = Δ E E ≈ - α Δ ( Δ V ) hE 0 .
Exemplary Embodiments of Cathodes According to the Invention 1) Examples of Cathode Using a Photoresistor in Mobility Mode
The parallelism of the optical control allows all the emitters to be driven in phase, thus allowing higher transconductances for the amplifiers that use these cathodes.
The galvanic isolation inherent in the optical control obviates the need for insulators and allows high-frequency performance to be conserved.
The elimination of the electrical input guides simplifies the connection components and allows enhanced miniaturization notably for triodes.
The elimination of the grid in certain configurations of amplifier tubes leads to a simplification of fabrication and to the elimination of the problems of grid rigidity and grid transparency.
Optical control is compatible with remote control.
In certain types of tubes, the possibility of an optical ‘gate’ on an electrically-controlled device can lead to design simplification. Lastly, generally speaking, the invention allows compact and wideband tubes.
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U.S. Classification 313/498, 313/531, 313/537
International Classification H01J1/62, H01J40/00, H01J40/16
Cooperative Classification H01J1/34, H01J1/304, H01J2201/30469, H01J2223/04, H01J23/04, B82Y10/00, H01J2201/304
European Classification H01J23/04, H01J1/304, B82Y10/00, H01J1/34
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