US3750180A - Magnetic antenna with time variations of core permeability - Google Patents
Magnetic antenna with time variations of core permeability Download PDFInfo
- Publication number
- US3750180A US3750180A US00273694A US3750180DA US3750180A US 3750180 A US3750180 A US 3750180A US 00273694 A US00273694 A US 00273694A US 3750180D A US3750180D A US 3750180DA US 3750180 A US3750180 A US 3750180A
- Authority
- US
- United States
- Prior art keywords
- core
- coil
- antenna
- wound
- pumping
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F7/00—Parametric amplifiers
- H03F7/02—Parametric amplifiers using variable-inductance element; using variable-permeability element
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F21/00—Variable inductances or transformers of the signal type
- H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
- H01F21/08—Variable inductances or transformers of the signal type continuously variable, e.g. variometers by varying the permeability of the core, e.g. by varying magnetic bias
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F29/00—Variable transformers or inductances not covered by group H01F21/00
- H01F29/14—Variable transformers or inductances not covered by group H01F21/00 with variable magnetic bias
- H01F29/146—Constructional details
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
- H01Q7/06—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with core of ferromagnetic material
Definitions
- This invention relates to antenna systems using a magnetic core.
- An object of the invention is to provide an antenna system having a magnetic core provided with coils wound thereon such as to cause time variations of the core permeability so as to cause variations of the inductances of the antenna coil and output coil wound on the core for parametric amplification of the reception signal, to thereby obtain amplified antenna output.
- a further object of the invention is to provide an array antenna, which consists of a plurality of the aforementioned antenna systems used as antenna elements, and whose directional characteristics can be desirably controlled through the adjustment of the amplitude and phase of parametric pumping sources for the individual antenna elements.
- FIG. I is a pictorial representation of a prior-art antenna system having a magnetic core
- FIG. 2 is a graph showing inductances and mutual inductance versus d-c bias current in the same prior-art antenna system
- FIG. 3 shows an equivalent circuit for an embodiment of the antenna system according to the invention
- FIG. 4 is a perspective representation of the construction of the same antenna system according to the invention.
- FIG. 5 is a view showing a magnetic field set up in the magnetic core of the antenna system of FIG. 4 by current flowing in a pumping coil;
- FIG. 6 is a perspective representation of an experimental arrangement, showing a connection of a signal source and a load to the antenna system of FIG. 4;
- FIG. 7 is a graph showing power trarisfer gain plotted against internal resistance R,, with the load resistance R, used as a parameter, in the arrangement of FIG. 7;
- FIGS. 8 to 11 are perspective views showing some other embodiments of the antenna system according to the invention.
- FIG. 12 is a perspective view showing the embodiment of FIG. 8 provided with coils
- FIG. 13 is a perspective view showing the embodiment of FIG. provided with coils.
- FIG. 14 is a pictorial representation of an array antenna embodying the invention.
- the magnetic flux produced in the core 5 by the current flowing in the pumping coil 6 penetrates part of the core sections 1 and 3 extending between the two parts of the antenna coil 2.
- FIG. 2 shows the inductances La and Li of the antenna coil 2 and output coil 4 and mutual inductance M between these two coils, which are plotted against corresponding values of d-c bias current flowing in the pumping coil 6.
- the inductance La of the antenna coil 2 hardly changes, while the inductance Li of the output coil 4 and mutual inductance M appreciably change.
- the d-c bias current By setting the d-c bias current to an appropriate value so as to obtain an optimum coupling between the antenna coil 2 and the output coil 4, the mutual inductance can be varied with frequency of the pumping current, which is supplied to coil 6.
- the mutual inductance between the antenna coil 2 and output coil 4 is caused to vary at the pumping frequency, resulting in parametric amplification of a signal received by the antenna to obtain an amplified antenna output.
- the variation of the mutual inducatance at this time is attributable to changes in the permeability of the magnetic core 3. Accordingly, in order to obtain large changes of the mutual inductance with small pumping current it is necessary to select a reluctance of the core 3 sufficiently high compared to the reluctance of the core 1 to obtain saturation of the core in the operation.
- the antenna efficiency is very low. Also, with such an arrangement of cores 1 and 5 as shown in FIG. I, considerably large pumping power and d-c bias power are required to activate these cores 1 and 5. Further, leakageflux is considerably great.
- the above drawbacks inherent in the conventional antenna system are overcome by providing improvements in the core construction and method of winding of the coils, so that the gain is extremely increased.
- the efficiency of the conventional antennasystem is low because it chiefly utilizes mutual inductance between the antenna coil and output coil whichvaries depending upon the pumping causing saturation of the magnetic core and also because it uses a magnetic core divided into two sections.
- the magnetic core and the coils are so constructed and arranged that time variations of the permeability of the core itself may be caused, and on the basis of this variation the mutual inductance between the antenna coil and output coil is :made variable to obtain a large amplification degree.
- the winding of the pumping coil are arranged perpendicular to the winding of the other coils so that the coupling between the antenna coil circuit and the output coil circuit is made by the time-variable mutual inductance alone, thus eliminating the otherwise possible deterioration of the efficiency.
- FIG. 3 shows an equivalent circuit for the antenna system according to the invention.
- L(t) represents an equivalent inductance accounting for variations in the inductances of the antenna coil and output coil due to time variations of the permeability of the magnetic core.
- the circuit on the left hand side of the inducatance L(t) (hereinafter referred to as signal circuit) consists of an antenna coil tuning :reactance X
- V, and R respectively represent the terminal voltage induced across the antenna coil and the resistance across the antenna coil terminals at the time of resonance.
- the circuit on the right hand side of the inductance L(t) (hereinafter referred to as output circuit) consists of an output coil tuning reactance X, and a load R
- R represents loss re-' sistance in the coils and core.
- the Q of the aforementioned left hand side circuit i.e., signal circuit
- this circuit is not directly coupled by any circuit element but it is coupled by the above inductance L(t).
- the inductance L(t) changing at a pumping angular frequency of w is generally given as L(t) L, 2L, cos 0,:
- the condition for the oscillation is given as
- the output circuit is tuned to (0,, the power transfer gain 6,, may be similarly obtained as tenna coil, which is partly wound round the whole body of the core 7, and some of whose turns 10 pass through the aperture 8 and 8'.
- Numeral ll designates an output coil, which is wound such that all its turns pass through the apertures 8 and 8'.
- Numeral l2 designates a pumping coil, which is wound on part of the core between the apertures 8 and 8' such that its winding are perpendicular to the winding of the antenna and output coils 9 and 11.
- FIG. 6 An experimental circuit as shown in FIG. 6.
- the magnetic core and the state of winding of the individual coils are the same as for the construction of FIG. 4, so they are not described any further.
- a signal source 13 Connected between the terminals of the antenna coil 9 is a signal source 13 at a frequency of 1 MHz with an internal resistance R,.
- a load resistor R Connected across the output coil 11 is a load resistor R, in series with a tuning capacitor C
- the above experimental circuit was put under parametric pumping at a pumping frequency of 4 MHz for measuring the power transfer gain for output frequency w, 3 MHz.
- the power transfer gain 6, in this case is from equation 6 FIG.
- Dashed curves in FIG. 7 show results of calculation of the power transfer gain 6,: from the above values and using equation 9. It will be seen that the measured values shown by the solid curves well agree with the calculated values, and this can well account for the fact that the above embodiment of the antenna system according to the invention operates in conformity to the principles discussed earlier.
- permanent magnets are provided in close contact with the magnetic core, which is the same as that 7 shown in FIG. 4.
- permanent magnets are provided at a spacing from the magnetic core 7.
- two permanent magnets 50 are fitted in close contact to the opposite sides of part of the core between the apertures 8 and 8'.
- FIG. 12 shows the core 7 of FIG. 8, which is provided with individual coils.
- permanent magnets are fixed in close contact to opposite sides of portions of the core on both upper and lower sides of each of the apertures B and 8.
- the coils are wound similarily to the embodiment of FIG. 12. More particularly, the antenna coil 9 is wound partly on the whole body of the core, and some of its winding is passed through'the apertures so that it is wound on permanent magnets 51.
- the pumping coil 12 is wound on part of the core between the apertures8 and 8'.
- the output coil 11 is wound such that all its winding pass through the apertures and are wound on the permanent magnets fixed to core portions on one side of each of the apertures 8 and 8'.
- the coils are partly wound on the permanent magnets. This is acceptable if the permanent magnets 50 or 51 have sufficiently high resistivity, for instance about 10 ohm-cm, as of ferrite magnets. However, with metalmagnets of low resistivity winding the coils on the magnets undesirably results in large core loss.
- the FIG. 10 embodiment uses channel-shaped magnets 53, which are fixed to opposite sides of the core 7 with their legs 52 made of a non-magnetic material in close contact with the core. With this construction, it is possible to adjust the bias field set up by the permanent magnets 53 in the core '7 by varying the thickness of the non-magnetic material.
- the pumping coil 12 is wound directly on the core portion between the apertures 8 and 8 on the inner side of each of the permanent magnets 53. In this case, either metal magnet or ferrite magnet may be used for the permanent magnets 53.
- the FIG. 11 embodiment also uses channel-shaped permanent magnets 54 each applied with a nonmagnetic material 55 on the inner recess side. These magnets 54 are fitted on the respective upper and lower edges of the core 7. In this case, it is of course possible to adjust the bias field produced by the permanent magnets 54 in the core 7 by varying the thickness of the non-magnetic material layer 55. In this embodiment, the coils are wound similarly to the preceding embodiments.
- the antenna system described earlier in connection with FIG. 4 may be used as antenna element to construct array antennas. Such arrayantennas can provide useful advantages over the prior-art array antennas.
- phase shifter and attenuator inserted between the associatedarray element and transmitter or between array element and receiver are appropriately adjusted or a suitable lumped constant circuit or distributed constant circuit is provided.
- phase shifters and attenuators or lumped constant circuits or distributed constant circuits are adjusted either electrically or mechanically to provide the desired directional characteristics of the array antenna.
- phase shifters and attenuators or lumped constant circuits or distributed constant circuits are required to give rise to small energy loss dueto their insertion.
- energy loss of l to 2 dB results.
- variable phase range is limited, and where broader phase ranges should be covered it is necessary to use several phase shifter units in combination with inevitably accompanying increase of the: energy loss. Therefore, the number ofphase shifters inserted in combination is limited due to the increase in energy loss.
- FIG. 14 shows an array antenna according to the invention.
- This array antenna consists of two array ele- Through this variable inductance L(t) power transfer between signal received by the element and pumping signal is effected, that is, the received signal is subjected to parametric amplification.
- L(t) variable inductance
- variable inductance element with inductance L(t) the voltage e induced across the variable inductance element is Also, the output voltages e and e when the out put circuit is tuned respectively to (w, w.) and (w, w.) are g and
- the coefficient L, in the above variable inductance depends upon the material and structure of the magnetic core and coil construction, and is proportional to the amplitude of the pumping current.
- the amplitude and phase of the antenna output can be controlled by varying the amplitude and phase of the pumping current.
- the antenna outputs e (1) and e (2) of the respective array antenna elements 101 and 102 are where k Z-rrd/A, A being wavelength.
- the resultant voltage e is also, the directional characteristics D( b) of the array antenna is given as The L and L," for the respective antenna elements 101 and 102 are respectively proportional to the amplitude of the parametric pumping current in these elements 101 and 102.
- the 0, and 0, are identical with the phases of the parametric pumping sources of the antenna elements 101 and 102 respectively.
- the directional characteristics are controllable by varying the amplitude and phase of the parametric pumping source.
- Such high efficiency antenna array may of course be similarly constructed by using antenna elements shown in FIGS. 12 and 13.
- the invention it is possible to obtain a high efficiency array antenna capable of providing amplified antenna output. Also, according to the invention the d-c biasing can be readily achieved.
- An antenna system comprising an electromagnetic wave reception magnetic core formed with a plurality of apertures a first coil serving as pumping coil for changing the permeability of said magnetic core, said first coil being wound on part of said core between adjacent ones of said apertures, and two second coils linked by magnetic flux produced by said pumping coil, said second coils being wound such that their windings are perpendicular to the winding of said first coil, one of said second coils being wound on said core such that its all winding passes through said apertures, the other of said second coils having some of its winding wound around the whole body of said core and the other of its winding passed through said apertures.
- An antenna system which further comprises at least one permanent magnet affixed to said magnetic core for producing a bias field in said core.
- An array antenna consisting of a plurality of antenna elements, each of which is the antenna system as claimed in claim 1, in which means is connected with said first coil for independently controlling the amplitude and phase of a pumping current flowing through said first coil thereby obtaining desired and controllable directional characteristics of the array antenna.
- An antenna system which further comprises non-magnetic spacers individually provided between said respective permanent magnets and said core, said spacers serving to render variable the intensity of the bias field set up by said magnets in said magnetic core.
- An array antenna consisting of a plurality of antenna elements, each of which is the antenna system as claimed in claim 2, in which means is connected with said first coil for independently controlling the amplitude and phase of a pumping current flowing through said first coil thereby obtaining desired and controllable directional characteristics of the array antenna.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Variable-Direction Aerials And Aerial Arrays (AREA)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5500371A JPS5330976B1 (pt) | 1971-07-22 | 1971-07-22 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3750180A true US3750180A (en) | 1973-07-31 |
Family
ID=12986463
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00273694A Expired - Lifetime US3750180A (en) | 1971-07-22 | 1972-07-21 | Magnetic antenna with time variations of core permeability |
Country Status (6)
Country | Link |
---|---|
US (1) | US3750180A (pt) |
JP (1) | JPS5330976B1 (pt) |
CA (1) | CA961935A (pt) |
DE (1) | DE2235958A1 (pt) |
FR (1) | FR2146477B1 (pt) |
GB (1) | GB1334499A (pt) |
Cited By (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4588994A (en) * | 1982-10-18 | 1986-05-13 | Hughes Aircraft Company | Continuous ferrite aperture for electronic scanning antennas |
US4827272A (en) * | 1984-06-04 | 1989-05-02 | Davis Murray W | Overhead power line clamp and antenna |
US6061030A (en) * | 1996-11-01 | 2000-05-09 | Plantronics, Inc. | Aerial arrays for magnetic induction communication systems having limited power supplies |
US6134420A (en) * | 1996-11-01 | 2000-10-17 | Plantronics, Inc. | Vector measuring aerial arrays for magnetic induction communication systems |
US6396454B1 (en) * | 2000-06-23 | 2002-05-28 | Cue Corporation | Radio unit for computer systems |
US20020080083A1 (en) * | 2000-12-21 | 2002-06-27 | Lear Corporation | Remote access device having multiple inductive coil antenna |
US20020113747A1 (en) * | 2000-05-12 | 2002-08-22 | Virginie Tessier | Transmitter and receiver coil |
US20030155792A1 (en) * | 2002-02-21 | 2003-08-21 | Horst Bohm | Multi-layered vehicle body part and method of manufacture |
US20040252068A1 (en) * | 2003-06-16 | 2004-12-16 | Hall Stewart E. | High efficiency core antenna and construction method |
US20050078045A1 (en) * | 2003-10-09 | 2005-04-14 | Casio Computer Co., Ltd. | Antenna and wristwatch |
US6930646B2 (en) * | 1995-08-22 | 2005-08-16 | Mitsubishi Materials Corporation | Transponder and antenna |
US20100309081A1 (en) * | 2007-12-18 | 2010-12-09 | Murata Manufacturing Co., Ltd. | Magnetic material antenna and antenna device |
US20160005530A1 (en) * | 2014-07-02 | 2016-01-07 | Analog Devices Global | Inductive component for use in an integrated circuit, a transformer and an inductor formed as part of an integrated circuit |
RU2687849C1 (ru) * | 2018-07-04 | 2019-05-16 | Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" (Госкорпорация "Росатом") | Приемная магнитная антенна |
DE102018102895A1 (de) * | 2018-02-09 | 2019-08-14 | SUMIDA Components & Modules GmbH | Ferritstabantenne und Sende- und Empfangseinheit mit entsprechender Ferritstabantenne |
US11404197B2 (en) | 2017-06-09 | 2022-08-02 | Analog Devices Global Unlimited Company | Via for magnetic core of inductive component |
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JP6887624B2 (ja) * | 2016-08-15 | 2021-06-16 | 学校法人自治医科大学 | 自閉症スペクトラム障害及び精神疾患改善剤 |
CN113613639A (zh) | 2019-03-20 | 2021-11-05 | 国立大学法人香川大学 | 利用d-阿洛糖被癌细胞摄取的性质的药物输送载体、药物输送方法和用于治疗肾细胞癌的组合物 |
WO2020195037A1 (ja) | 2019-03-26 | 2020-10-01 | 国立大学法人香川大学 | 尿路臓器腔内に注入可能な尿路上皮癌の予防または治療のための医薬組成物 |
WO2020203086A1 (ja) | 2019-03-29 | 2020-10-08 | 国立大学法人香川大学 | D-アロースおよび/またはd-アルロースを含有してなる腹膜透析液の浸透圧調整剤 |
WO2021193949A1 (ja) | 2020-03-26 | 2021-09-30 | 国立大学法人香川大学 | 新規l-ラムノースイソメラーゼ |
KR20230117115A (ko) | 2020-11-30 | 2023-08-07 | 고쿠리츠다이가쿠호우징 카가와다이가쿠 | 신규 l-람노스 이소머라아제 |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3564551A (en) * | 1970-01-14 | 1971-02-16 | Harry A Mills | Dipole antenna with electrically tuned ferrite sleeves |
US3665476A (en) * | 1965-12-01 | 1972-05-23 | Singer Co | Antenna |
-
1971
- 1971-07-22 JP JP5500371A patent/JPS5330976B1/ja active Pending
-
1972
- 1972-07-21 DE DE2235958A patent/DE2235958A1/de active Pending
- 1972-07-21 CA CA147,655A patent/CA961935A/en not_active Expired
- 1972-07-21 FR FR7226404A patent/FR2146477B1/fr not_active Expired
- 1972-07-21 US US00273694A patent/US3750180A/en not_active Expired - Lifetime
- 1972-07-24 GB GB3456072A patent/GB1334499A/en not_active Expired
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3665476A (en) * | 1965-12-01 | 1972-05-23 | Singer Co | Antenna |
US3564551A (en) * | 1970-01-14 | 1971-02-16 | Harry A Mills | Dipole antenna with electrically tuned ferrite sleeves |
Cited By (25)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4588994A (en) * | 1982-10-18 | 1986-05-13 | Hughes Aircraft Company | Continuous ferrite aperture for electronic scanning antennas |
US4827272A (en) * | 1984-06-04 | 1989-05-02 | Davis Murray W | Overhead power line clamp and antenna |
US6930646B2 (en) * | 1995-08-22 | 2005-08-16 | Mitsubishi Materials Corporation | Transponder and antenna |
US6061030A (en) * | 1996-11-01 | 2000-05-09 | Plantronics, Inc. | Aerial arrays for magnetic induction communication systems having limited power supplies |
US6134420A (en) * | 1996-11-01 | 2000-10-17 | Plantronics, Inc. | Vector measuring aerial arrays for magnetic induction communication systems |
US20020113747A1 (en) * | 2000-05-12 | 2002-08-22 | Virginie Tessier | Transmitter and receiver coil |
US20020080082A1 (en) * | 2000-06-23 | 2002-06-27 | Cue Corporation | Radio unit for computer systems |
US6396454B1 (en) * | 2000-06-23 | 2002-05-28 | Cue Corporation | Radio unit for computer systems |
US6563474B2 (en) * | 2000-12-21 | 2003-05-13 | Lear Corporation | Remote access device having multiple inductive coil antenna |
US20030210198A1 (en) * | 2000-12-21 | 2003-11-13 | Lear Corporation | Remote access device having multiple inductive coil antenna |
US20020080083A1 (en) * | 2000-12-21 | 2002-06-27 | Lear Corporation | Remote access device having multiple inductive coil antenna |
US6940461B2 (en) | 2000-12-21 | 2005-09-06 | Lear Corporation | Remote access device having multiple inductive coil antenna |
US20030155792A1 (en) * | 2002-02-21 | 2003-08-21 | Horst Bohm | Multi-layered vehicle body part and method of manufacture |
US7209090B2 (en) * | 2003-06-16 | 2007-04-24 | Sensormatic Electronics Corporation | High efficiency core antenna and construction method |
US20040252068A1 (en) * | 2003-06-16 | 2004-12-16 | Hall Stewart E. | High efficiency core antenna and construction method |
US20050078045A1 (en) * | 2003-10-09 | 2005-04-14 | Casio Computer Co., Ltd. | Antenna and wristwatch |
US7161551B2 (en) * | 2003-10-09 | 2007-01-09 | Casio Computer Co., Ltd. | Antenna and wristwatch |
US20100309081A1 (en) * | 2007-12-18 | 2010-12-09 | Murata Manufacturing Co., Ltd. | Magnetic material antenna and antenna device |
US8604992B2 (en) * | 2007-12-18 | 2013-12-10 | Murata Manufacturing Co., Ltd. | Magnetic material antenna and antenna device |
US20160005530A1 (en) * | 2014-07-02 | 2016-01-07 | Analog Devices Global | Inductive component for use in an integrated circuit, a transformer and an inductor formed as part of an integrated circuit |
US11404197B2 (en) | 2017-06-09 | 2022-08-02 | Analog Devices Global Unlimited Company | Via for magnetic core of inductive component |
DE102018102895A1 (de) * | 2018-02-09 | 2019-08-14 | SUMIDA Components & Modules GmbH | Ferritstabantenne und Sende- und Empfangseinheit mit entsprechender Ferritstabantenne |
EP3525286A1 (de) | 2018-02-09 | 2019-08-14 | SUMIDA Components & Modules GmbH | Ferritstabantenne und sende- und empfangseinheit mit entsprechender ferritstabantenne |
DE102018102895B4 (de) | 2018-02-09 | 2019-10-24 | SUMIDA Components & Modules GmbH | Ferritstabantenne und Sende- und Empfangseinheit mit entsprechender Ferritstabantenne |
RU2687849C1 (ru) * | 2018-07-04 | 2019-05-16 | Российская Федерация, от имени которой выступает Государственная корпорация по атомной энергии "Росатом" (Госкорпорация "Росатом") | Приемная магнитная антенна |
Also Published As
Publication number | Publication date |
---|---|
GB1334499A (en) | 1973-10-17 |
JPS5330976B1 (pt) | 1978-08-30 |
CA961935A (en) | 1975-01-28 |
FR2146477B1 (pt) | 1977-07-22 |
FR2146477A1 (pt) | 1973-03-02 |
DE2235958A1 (de) | 1973-02-01 |
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