US3262118A - Scanning antenna with gaseous plasma phase shifter - Google Patents

Scanning antenna with gaseous plasma phase shifter Download PDF

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US3262118A
US3262118A US809448A US80944859A US3262118A US 3262118 A US3262118 A US 3262118A US 809448 A US809448 A US 809448A US 80944859 A US80944859 A US 80944859A US 3262118 A US3262118 A US 3262118A
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plasma
energy
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resonance
phase advance
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Roger C Jones
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Melpar Inc
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/26Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
    • H01Q3/30Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array
    • H01Q3/34Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the relative phase between the radiating elements of an array by electrical means

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  • the present invention relates generally to antennas and more particularly to scanning antennas employing gaseous plasma resonant devices and cyclotron plasma resonant devices as variable phase-shift devices which vary the directivities of the radiation patterns of the antennas.
  • both linear scanning and circular scanning may be achieved.
  • energy is transmitted along a wave guide or transmission line, to phase-separated radiating elements. These may be slots in the case of Wave guide, and rods in the case of transmission lines.
  • Either the lines themselves or containers located therein may be filled with a gaseous medium capable of being excited to resonance, either plasma resonance or cyclotron resonance.
  • Phase delays of different relative magnitudes, in energy emanating from the radiating elements may then be induced by varying the exciting voltages or currents utilized to excite the gaseous medium, and the magnetic field distributions employed to achieve cyclotron plasma resonance.
  • Another object of the invention resides in the provision of a linear scanning antenna employing cyclotron plasma resonance phase advance elements.
  • FIGURE 1 is a schematic representation of a linear scanning antenna array, employing plasma resonance controllable phase shift elements
  • FIGURE 2 is a schematic diagram of a modification of the system of FIGURE 1, which employs cyclotronplasma resonance controllable phase shift elements.
  • the wave length of electromagnetic waves in the media is a function of the dielectric constant of the insulating medium employed, for any fixed frequency. Effectively, this is becadse the velocity of such waves is a function of dielectric constant.
  • wave length is further affected by line or guide constants, but for a given line or guide wave length can be controlled as a function of d.
  • Ad in a wave guide or transmission line may be varied if the dielectric material is a gaseous plasma by varying electron density in the plasma, and that this may be accomplished by varying the amplitude of an excitation voltage.
  • the excitation voltage is direct.
  • H type excitation may be employed, i.e., excitation due to R.F. current flow in a coil. This current flow may exist at about 30 mc. for example only.
  • RF. frequency remains constant, and scanning of the beam is accomplished, as a function of amplitude of excitation.
  • the reference numeral 10 denotes a section of wave guide, which may be coupled at one end to a source of RP. energy at about 3 kmc., by menas of a conventional coupling device 12. This energy travels down the wave guide in the TE mode to a tapered load 13, which prevents reflections. Obviously, any other mode may be utilized.
  • slits 14 In the edges of the wave guide 10 are located slits 14, to permit egrees of RF. energy in controlled phase relation. The distances between slits 14 are selected to provide a desired radiation pattern extending generally perpendicular to the plane of the slits.
  • a glass, Pyrex or quartz tube 1-6 which extends longitudinally beyond the slits, and preferably substantially fills the wave guide 10 transversely, although this is by no means essential.
  • the tube 16 includes three vertical extensions 17, about each of which is wound a few turns of wire, to form coils 18.
  • the coils 18 are energized at 3 mc. from an oscillator 19, which feeds the coils 18 via a power amplifier 20, the output of the latter being controlled by a relatively low frequency modulator, say at frequencies below 100,000 c.p.s.
  • the gas in the tube 16 may be one of He, Ar, Kr, Xe, or other inert gas, at a density of .1 to several millimeters of mercury.
  • a resonance plasma is formed, which has a dielectric constant which is a function of degree of excitation, i.e., of current in coils 18.
  • wave velocity of RF. energy in the wave guide 10 is likewise varied, and accordingly the phase relations of RE. energy components reaching the respective slits. Thereby, the directivity of the radiation pattern of en ergy emitted from the slits is altered.
  • a section of S-band wave guide was employed, having four slits as radiators.
  • a gas tube 16 about thirteen (13) inches long was employed, the tube being fabricated of 1" ⁇ D. Pyrex glass. The glass tube was carefully baked out and evacuated, and then filled with 1.5 mm. Hg of spectroscopically pure argon gas.
  • Four turns of copper tubing were used to excite each excitation column 17, and fed in series with 600 watts of about 29 me. signal, to produce the gaseous plasma.
  • a radiation pattern shift of about 15 was obtained, as excitation of the 29 mc. signal was varied in amplitude.
  • Possibility of radical improvement is indicated, on theoretical considerations, by decreasing gas pressure, utilizing a larger active column, and better slit design.
  • FIGURE drawings use of a magneto-static field, impressed across the gas tube 1 6, accompained by decreased gas pressure, results in radically increased performance by virtue of the principle of cyclotron-plasma resonance.
  • the systems of FIGURES 1 and 2 are identical except for inclusion of a magnetic field source 22 in FIGURE 2 and the use of reduced gas pressure. Advantages are (1) lower power loss, (2) less deterioration of noise figure and (3) greater band width.
  • plasma resonance indicates that the electrons in a gaseous plasma are moving in oscillatory motion, at a rate such that there exists mechanical resonance of the electrons with the frequency of the RF. field.
  • This term is synonymous with the term plasma oscillations which Tonks uses to describe the phenomena in volume 33, pages 195 ff. of the Physical Review, 1929.
  • Plasma-cyclotron resonance implies that motion of the electrons occurs in paths affected by a magneto-static field. The latter causes the electrons to travel in spiral paths, while being oscillated in the plasma resonance mode, somewhat in the manner of ionized particles in a cyclotron.
  • dielectric constant of a gaseous discharge plasma depends on the electronic charge density in the plasma.
  • the plasma in this respect acts like a singly resonant electrical circuit having losses.
  • the plasma acts like a singly resonant filter for some frequency w.
  • This frequency can be changed by changing n, the electron density.
  • the RF. energy has a frequency adjacent to the resonant frequency
  • the phase of the RJF. energy suffers rapid shifts in passing through the plasma, just as the phase of a signal passing through a singly resonant circuit would change were the filter slightly detuned with respect to the frequency of the signal.
  • cyclotron resonance is added, several possibilities exist. The cyclotron effect is equivalent to the addition of another tuned circuit. By proper selection of the frequency of the latter, the effect of a doubletuned circuit may be accomplished. Still further, by employing nonuniform excitation of the gas in the plasma and plasma cyclotron, a range of values of n is provided, which has the effect of broad-banding the resonant response band of the plasma.
  • a system for providing a scanning radiation pattern including a plurality of radiators, a constant frequency source of radio frequency energy, means coupling said source of radio frequency energy to said radiators, at least one plasma resonance phase advance device arranged to provide a phase advance of radio frequency energy of extent determined by amplitude of excitation of said plasma, said at least one plasma resonance phase advance device being included in said means coupling said source of radio frequency energy to'said radiators, and'a source'of control energy coupled: a a r a in exciting relation to said plasma resonance phase advance device, said source of control energy being of such amplitude and frequency as to excite the electrons of said plasma into resonance, and means for continuously varying the amplitude of said control energy.
  • said plasma resonance device is a cyclotron plasma resonance device.
  • An antenna array comprising plural antennas, a source of radio frequency energy, means coupling said antennas to said source in parallel, each means including in series a plasma resonant phase advance unit, and means for controlling the excitation of said plasma resonant phase advance units so as to vary the radiation pattern of said array, said last named means including a source of control energy applied to said units, said energy source being of such amplitude and frequency as to excite the electrons of said plasma into resonance.
  • a variable phase shift circuit for a source of electromagnetic energy including a closed tube of dielectric material containing an ionizable gas, means for coupling the energy of said source to said tube, means exciting said gas electromagnetically at a frequency of approximately thirty megacycles per second to excite said gas to plasma resonance, and means for varying the intensity of the electromagnetic excitation to vary the phase shift of the energy from said source, wherein is further provided a source of magnetostatic field coupled with said gas and of intensity sufficient to establish cyclotron plasma resonance in said gas.

Description

July 19, 1966 R. c. JONES SCANNING ANTENNA WITH GASEOUS PLASMA PHASE SHIFTER Filed April 28, 1959 POWER QU T PU T F/G/ I? J /7 17 778W TAPERED LOAD 3 W r /4 l4 -l6 l MOD POWER Al 20 AMP MAG/VET 1 30 MC. W
Roam
IN V EN TOR.
C Jon/Es Arrok/vsrs United States Patent Ofi ice 3,262,118 SCANNING ANTENNA WITH GASEOUS PLASMA PHASE SHIFTER Roger C. Jones, North Springfield, Va., assignor, by mesnc assignments, to Melpar, Inc., Falls Church, Va., a corporation of Delaware Filed Apr. 28, 1959, Ser. No. 809,448 4 Claims. (Cl. 343701) The present invention relates generally to antennas and more particularly to scanning antennas employing gaseous plasma resonant devices and cyclotron plasma resonant devices as variable phase-shift devices which vary the directivities of the radiation patterns of the antennas.
Electrically steerable or scanning antennas are known per se. The presently known scanning mechanisms are, however, inherently complex and lacking in flexibility and versatility and are restricted in speed of scan. By utilizing phase shifters to the plasma resonance types, or of the cyclotron plasma resonance type, in scanning antennas, it is feasible to fabricate scanning antennas of various types, which are simple and versatile, and in which extremely high scanning rates can be achieved.
In accordance with various embodiments of the invention, both linear scanning and circular scanning may be achieved. In the linear scanner energy is transmitted along a wave guide or transmission line, to phase-separated radiating elements. These may be slots in the case of Wave guide, and rods in the case of transmission lines. Either the lines themselves or containers located therein may be filled with a gaseous medium capable of being excited to resonance, either plasma resonance or cyclotron resonance. Phase delays of different relative magnitudes, in energy emanating from the radiating elements, may then be induced by varying the exciting voltages or currents utilized to excite the gaseous medium, and the magnetic field distributions employed to achieve cyclotron plasma resonance.
It is, accordingly, a broad object of the present invention to provide a novel scanning antenna system, employing plasma resonance or cyclotron plasma resonance phenomena in phase shifting elements of the system.
It is a further object of the invention to provide a linear scanning antenna employing plasma resonance phase advance elements.
Another object of the invention resides in the provision of a linear scanning antenna employing cyclotron plasma resonance phase advance elements.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:
FIGURE 1 is a schematic representation of a linear scanning antenna array, employing plasma resonance controllable phase shift elements;
FIGURE 2 is a schematic diagram of a modification of the system of FIGURE 1, which employs cyclotronplasma resonance controllable phase shift elements.
In Wide band transmission media, such as transmission lines and wave guides, the wave length of electromagnetic waves in the media is a function of the dielectric constant of the insulating medium employed, for any fixed frequency. Effectively, this is becadse the velocity of such waves is a function of dielectric constant. The relation of Wave length in a free space, is given by A (1) xd=m where Rd is wave length in a medium, M is wave length in free space, and ed is dielectric constant of the medium.
3,252,118 Patented July 19, 1.966
For wave guides and transmission lines, wave length is further affected by line or guide constants, but for a given line or guide wave length can be controlled as a function of d. i
It is pointed out in US. Patent No. 2,641,702, issued to Cohen et al., that Ad in a wave guide or transmission line may be varied if the dielectric material is a gaseous plasma by varying electron density in the plasma, and that this may be accomplished by varying the amplitude of an excitation voltage. In accordance with the teachings of this patent the excitation voltage is direct. According to the present invention H type excitation may be employed, i.e., excitation due to R.F. current flow in a coil. This current flow may exist at about 30 mc. for example only. In accordance with the teaching of the patent, moreover, a beam of constant direction is maintained as RF. frequency is varied. According to the present invention, RF. frequency remains constant, and scanning of the beam is accomplished, as a function of amplitude of excitation.
Referring now more particularly to FIGURE 1 of the accompanying drawings, the reference numeral 10 denotes a section of wave guide, which may be coupled at one end to a source of RP. energy at about 3 kmc., by menas of a conventional coupling device 12. This energy travels down the wave guide in the TE mode to a tapered load 13, which prevents reflections. Obviously, any other mode may be utilized. In the edges of the wave guide 10 are located slits 14, to permit egrees of RF. energy in controlled phase relation. The distances between slits 14 are selected to provide a desired radiation pattern extending generally perpendicular to the plane of the slits.
Located within the wave guide 10 is a glass, Pyrex or quartz tube 1-6, which extends longitudinally beyond the slits, and preferably substantially fills the wave guide 10 transversely, although this is by no means essential. The tube 16 includes three vertical extensions 17, about each of which is wound a few turns of wire, to form coils 18. The coils 18 are energized at 3 mc. from an oscillator 19, which feeds the coils 18 via a power amplifier 20, the output of the latter being controlled by a relatively low frequency modulator, say at frequencies below 100,000 c.p.s.
The gas in the tube 16 may be one of He, Ar, Kr, Xe, or other inert gas, at a density of .1 to several millimeters of mercury. When excited by current flowing in coils 18 a resonance plasma is formed, which has a dielectric constant which is a function of degree of excitation, i.e., of current in coils 18. By varying this current periodically, wave velocity of RF. energy in the wave guide 10 is likewise varied, and accordingly the phase relations of RE. energy components reaching the respective slits. Thereby, the directivity of the radiation pattern of en ergy emitted from the slits is altered.
In one practical embodiment of the invention, a section of S-band wave guide was employed, having four slits as radiators. A gas tube 16 about thirteen (13) inches long was employed, the tube being fabricated of 1" \D. Pyrex glass. The glass tube was carefully baked out and evacuated, and then filled with 1.5 mm. Hg of spectroscopically pure argon gas. Four turns of copper tubing were used to excite each excitation column 17, and fed in series with 600 watts of about 29 me. signal, to produce the gaseous plasma. A radiation pattern shift of about 15 was obtained, as excitation of the 29 mc. signal was varied in amplitude. Possibility of radical improvement is indicated, on theoretical considerations, by decreasing gas pressure, utilizing a larger active column, and better slit design.
In accordance with a modification of the present in- 2 of the accompanying vention, illustrated in FIGURE drawings, use of a magneto-static field, impressed across the gas tube 1 6, accompained by decreased gas pressure, results in radically increased performance by virtue of the principle of cyclotron-plasma resonance. The systems of FIGURES 1 and 2 are identical except for inclusion of a magnetic field source 22 in FIGURE 2 and the use of reduced gas pressure. Advantages are (1) lower power loss, (2) less deterioration of noise figure and (3) greater band width.
The term plasma resonance indicates that the electrons in a gaseous plasma are moving in oscillatory motion, at a rate such that there exists mechanical resonance of the electrons with the frequency of the RF. field. This term is synonymous with the term plasma oscillations which Tonks uses to describe the phenomena in volume 33, pages 195 ff. of the Physical Review, 1929. Plasma-cyclotron resonance, on the other hand, implies that motion of the electrons occurs in paths affected by a magneto-static field. The latter causes the electrons to travel in spiral paths, while being oscillated in the plasma resonance mode, somewhat in the manner of ionized particles in a cyclotron.
It has been determined that at high frequencies the dielectric constant of a gaseous discharge plasma depends on the electronic charge density in the plasma. The relation between dielectric constant and electron charge density is I 2 e.,=e.,[1 M 1 me This frequency is precise, but in fact collisions take place, which impart to the plasma a relatively wide response curve. The plasma in this respect acts like a singly resonant electrical circuit having losses.
In the presence of collisions, the expression w in the above formula is replaced by W +u In sum, the plasma acts like a singly resonant filter for some frequency w. This frequency can be changed by changing n, the electron density. 'If the RF. energy has a frequency adjacent to the resonant frequency, the phase of the RJF. energy suffers rapid shifts in passing through the plasma, just as the phase of a signal passing through a singly resonant circuit would change were the filter slightly detuned with respect to the frequency of the signal. Where cyclotron resonance is added, several possibilities exist. The cyclotron effect is equivalent to the addition of another tuned circuit. By proper selection of the frequency of the latter, the effect of a doubletuned circuit may be accomplished. Still further, by employing nonuniform excitation of the gas in the plasma and plasma cyclotron, a range of values of n is provided, which has the effect of broad-banding the resonant response band of the plasma.
While I have described and illustrated several specific embodiments of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.
What I claim is:
1. A system for providing a scanning radiation pattern, said system including a plurality of radiators, a constant frequency source of radio frequency energy, means coupling said source of radio frequency energy to said radiators, at least one plasma resonance phase advance device arranged to provide a phase advance of radio frequency energy of extent determined by amplitude of excitation of said plasma, said at least one plasma resonance phase advance device being included in said means coupling said source of radio frequency energy to'said radiators, and'a source'of control energy coupled: a a r a in exciting relation to said plasma resonance phase advance device, said source of control energy being of such amplitude and frequency as to excite the electrons of said plasma into resonance, and means for continuously varying the amplitude of said control energy.
2. The combination according to claim 1 wherein said plasma resonance device is a cyclotron plasma resonance device.
3. An antenna array comprising plural antennas, a source of radio frequency energy, means coupling said antennas to said source in parallel, each means including in series a plasma resonant phase advance unit, and means for controlling the excitation of said plasma resonant phase advance units so as to vary the radiation pattern of said array, said last named means including a source of control energy applied to said units, said energy source being of such amplitude and frequency as to excite the electrons of said plasma into resonance.
4. A variable phase shift circuit for a source of electromagnetic energy including a closed tube of dielectric material containing an ionizable gas, means for coupling the energy of said source to said tube, means exciting said gas electromagnetically at a frequency of approximately thirty megacycles per second to excite said gas to plasma resonance, and means for varying the intensity of the electromagnetic excitation to vary the phase shift of the energy from said source, wherein is further provided a source of magnetostatic field coupled with said gas and of intensity sufficient to establish cyclotron plasma resonance in said gas.
References Cited by the Examiner UNITED STATES PATENTS 2,085,406 6/1937 Zwory-kin 343-909 X 2,106,770 2/ 1938 Southworth et al. 343-701 X 2,466,354 4/1949 Bag-nall 343854 2,505,240 4/1950 Gorn 332--5 2,532,157 11/1950 Evans 333-31 2,641,702 6/1953 Cohen et al 333-31 2,696,566 12/1954 Lion et al. 30752 2,713,161 7/1955 Fiske 343 -816 2,929,058 3/1960 Blasberg et al. 343--777" HERMAN KARL SAALBACH, Primary Examiner.
GEORGE N. WESTBY, Examiner.
W. I. SIMMONS, ELI LlEBER MAN,
Assistant Examiners.

Claims (1)

1. A SYSTEM FOR PROVIDING A SCANNING RADIATION PATTERN, SAID SYSTEM INCLUDING A PLURALITY OF RADIATORS, A CONSTANT FREQUENCY SOURCE OF RADIO FREQUENCY ENERGY, MEANSE COUPLING SAID SOURCE OR RADIO FREQUENCY ENERGY TO SAID RADIATORS, AT LEAST ONE PLASMA RESONANCE PHASE ADVANCE DEVICE ARRANGED TO PROVIDE A PHASE ADVANCE OF RADIO FREQUENCY ENERGY OF EXTENT DETERMINED BY AMPLITUDE OF EXCITATION OF SAID PLASMA, SAID AT LEAST ONE PLASMA RESONANCE PHASE ADVANCE DEVICE BEING INCLUDED IN SAID MEANS COUPLING SAID SOURCE OF RADIO FREQUENCY ENERGY TO SAID RADIATORS, AND A SOURCE OF CONTROL ENERGY COUPLED IN EXCITING RELATION TO SAID PLASMA RESONANCE PHASE ADVANCE DEVICE, SAID SOURCE OF CONTROL ENERGY BEING OF SUCH AMPLITUDE AND FREQUENCY AS TO EXCITE THE ELECTRONS OF SAID PLASMA INTO RESONANCE, AND MEANS FOR CONTINUOUSLY VARYING THE AMPLITUDE OF SAID CONTROL ENERGY.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372394A (en) * 1963-07-29 1968-03-05 Trw Inc Electronically steerable antenna system utilizing controllable dipolar resonant plasma column
US3508268A (en) * 1967-06-07 1970-04-21 Hughes Aircraft Co Waveguide slot radiator with electronic phase and amplitude control
EP0230969A1 (en) * 1986-01-24 1987-08-05 Siemens Aktiengesellschaft Phased array antenna
DE3802662A1 (en) * 1988-01-29 1989-08-03 Licentia Gmbh Phase-controlled antenna
US20020132579A1 (en) * 1994-07-22 2002-09-19 International Mobile Satellite Organization Multi-beam TDMA satellite mobile communications system

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2085406A (en) * 1933-08-31 1937-06-29 Rca Corp Electrical device
US2106770A (en) * 1938-02-01 Apparatus and method fob receiving
US2466354A (en) * 1944-06-28 1949-04-05 American Telephone & Telegraph Directional radio system
US2505240A (en) * 1947-04-22 1950-04-25 Raytheon Mfg Co Frequency-modulating apparatus
US2532157A (en) * 1944-10-31 1950-11-28 Rca Corp Variable reactive microwave device
US2641702A (en) * 1948-10-22 1953-06-09 Int Standard Electric Corp Control of wave length in wave guide and coaxial lines
US2696566A (en) * 1949-10-20 1954-12-07 Kurt S Lion Electric transducer system
US2713161A (en) * 1949-07-27 1955-07-12 Gen Electric Radar scanning system
US2929058A (en) * 1955-04-04 1960-03-15 Hughes Aircraft Co Sequential lobing system with ferrite phase shifters

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2106770A (en) * 1938-02-01 Apparatus and method fob receiving
US2085406A (en) * 1933-08-31 1937-06-29 Rca Corp Electrical device
US2466354A (en) * 1944-06-28 1949-04-05 American Telephone & Telegraph Directional radio system
US2532157A (en) * 1944-10-31 1950-11-28 Rca Corp Variable reactive microwave device
US2505240A (en) * 1947-04-22 1950-04-25 Raytheon Mfg Co Frequency-modulating apparatus
US2641702A (en) * 1948-10-22 1953-06-09 Int Standard Electric Corp Control of wave length in wave guide and coaxial lines
US2713161A (en) * 1949-07-27 1955-07-12 Gen Electric Radar scanning system
US2696566A (en) * 1949-10-20 1954-12-07 Kurt S Lion Electric transducer system
US2929058A (en) * 1955-04-04 1960-03-15 Hughes Aircraft Co Sequential lobing system with ferrite phase shifters

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3372394A (en) * 1963-07-29 1968-03-05 Trw Inc Electronically steerable antenna system utilizing controllable dipolar resonant plasma column
US3508268A (en) * 1967-06-07 1970-04-21 Hughes Aircraft Co Waveguide slot radiator with electronic phase and amplitude control
EP0230969A1 (en) * 1986-01-24 1987-08-05 Siemens Aktiengesellschaft Phased array antenna
DE3802662A1 (en) * 1988-01-29 1989-08-03 Licentia Gmbh Phase-controlled antenna
US20020132579A1 (en) * 1994-07-22 2002-09-19 International Mobile Satellite Organization Multi-beam TDMA satellite mobile communications system

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