Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2003-03-10
2004-08-31
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C315S111010
Reexamination Certificate
active
06784620
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to filters for electromagnetic energy, and more particularly to such filters which use plasmas.
BACKGROUND OF THE INVENTION
Plasma is said to be the most common state of matter in the universe. In essence, a plasma is a state of matter in which the electrons of an atom are free from the remainder of the atom, whereby the remainder of the atom is electrically charged or ionized. Plasma has been of interest in the field of communications because of the presence of the ionosphere, which is a plasma lying above the earth's surface. It has long been known that the ionosphere would reflect electromagnetic radiation (also known generally as “radio-frequency” signals or radiation), so long as the frequency of the electromagnetic radiation was below a calculable frequency. The frequency at which the ionosphere reflects is known to vary as a function of at least the charged particle density of the ionosphere.
There is a body of knowledge about plasmas, set forth in texts such as
Fields and Waves in Communication Electronics
by Ramo, Whinnery, and Van Duzer, published 1994 by Wiley and
Introduction to Plasma Physics and Controlled Fusion
, by Chen, published 1994 by Plenum Press. In addition, the Internet is a source of information in regard to plasmas. A fundamental time-scale in plasma physics is the “plasma frequency.” Such a plasma frequency exists for all conductors, where the term “conductor” refers to matter containing free electrons.
The plasma frequency o
p
is given by
O
p
2
=
ne
2
ϵ
0
m
1
where:
n is the charged particle density (charged particle/volume);
e is the charge of the ionized particle (ion or electron);
m is the mass of the charged particle; and
o is permittivity of free space.
It will be clear that the plasma frequency is different as between the electron and the ion species, because of their different masses. The plasma frequency which is commonly referred to in the literature is the electron plasma frequency, which is much higher than the ion plasma frequency. The plasma frequency may be viewed simplistically as being the frequency in a conductor at which the electrons collectively oscillate relative to their ion cores. The plasma frequency may be conveniently measured in a manner analogous to the ionosphere propagation model, namely by applying an electromagnetic signal to the plasma, and determining the frequency at which reflection changes to propagation.
SUMMARY OF THE INVENTION
A frequency-sensitive apparatus according to an aspect of the invention comprises a first path for the flow of electromagnetic energy, and a first plasma lying in the first path. The first plasma has a first plasma frequency. A second plasma lies in the first path. The second plasma has a second plasma frequency, different from the first plasma frequency. In a particular embodiment of the apparatus according to this aspect of the invention, an electromagnetic energy port is coupled to the first path at a location lying between the first and second plasmas. In another embodiment, a first circulator is provided. The first circulator defines first, second, and third ports, and first, second, third paths for the flow of circulator electromagnetic energy from the first port to the second port, from the second port to the third port, and from the third port to the first port, respectively. The first path for the flow of electromagnetic energy of the first circulator lies in the first path for the flow of electromagnetic energy, at a location along the first path for the flow of electromagnetic energy which lies between the first and second plasmas. In another embodiment of this aspect of the invention, a second circulator is provided, with the second circulator defining fourth, fifth, and sixth ports, and fourth, fifth, and sixth paths for the flow of second circulator electromagnetic energy from the fourth port to the fifth port, from the fifth port to the sixth port, and from the sixth port to the fourth port, respectively, of the second circulator. The fourth port is coupled to the first path for the flow of electromagnetic energy at a location, relative to the first plasma, which is remote from the first circulator. In particular embodiments of this aspect of the invention, a first voltage source is coupled to the first plasma for maintaining the first plasma at the first plasma frequency, and a second voltage source is coupled to the second plasma for maintaining the second plasma at the second plasma frequency. In one application of an apparatus according to this first aspect of the invention, a source of electromagnetic energy is coupled to the first path at a location adjacent the first plasma, for transmitting electromagnetic waves along the path toward the first plasma and the second plasma. In a particular application, the electromagnetic waves transmitted by the source of electromagnetic energy include a component at a frequency lower than the plasma frequency of the first plasma, whereby the component of the electromagnetic waves transmitted by the source of electromagnetic energy tends to be reflected by the first plasma. In another particular application of the apparatus according to this aspect of the invention, the electromagnetic waves transmitted by the source of electromagnetic energy include a component at a frequency lying between the plasma frequency of the first plasma and the plasma frequency of the second plasma, whereby the component of the electromagnetic waves transmitted by the source of electromagnetic energy tends to be passed by the first plasma and reflected by the second plasma. In this particular application, it may be advantageous if the apparatus further comprises electromagnetic signal coupling means coupled to the first path at a location lying between the first and second plasmas, for extracting the component of the electromagnetic energy at a frequency lying between the plasma frequency of the first plasma and the plasma frequency of the second plasma. In one version, the electromagnetic signal coupling means is directional. It may be a directional coupler. In yet another application of the apparatus according to this aspect of the invention, the electromagnetic waves transmitted by the source of electromagnetic energy include a component at a frequency lying above the plasma frequencies of the first plasma and the second plasma, whereby the component of the electromagnetic waves transmitted by the source of electromagnetic energy tends to be passed by the first and second plasmas. In such a version, the apparatus may advantageously include utilization means coupled to the first path at a location relative to the second plasma which is remote from the first plasma. In an application of the apparatus according to this aspect of the invention, where the electromagnetic waves transmitted by the source of electromagnetic energy include components having frequencies lying above the plasma frequency of the first plasma and other components having frequencies lying above the plasma frequency of the second plasma the apparatus according to this aspect of the invention may advantageously include electromagnetic signal coupling means, which may be directional, coupled to the first path at a location lying between the first and second plasmas, for extracting the component of the electromagnetic energy at a frequency lying between the plasma frequency of the first plasma and the plasma frequency of the second plasma. It may further advantageously include signal utilization means coupled to the first path at a location adjacent the second plasma and remote from the first plasma, for utilizing the component of the electromagnetic energy at a frequency lying above the plasma frequency of the second plasma. If the electromagnetic signal coupling means comprises a directional coupler, the coupler may define a path between first and second ports, and a third port, with the path between first and second ports lying in the first path at the location lying between the first and second plasmas, for co
Dinh Trinh Vo
Lockheed Martin Corporation
Morris LLP Duane
Wong Don
LandOfFree
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