US3205459A - Waveguide termination with magnetic metal walls wherein the curie temperature thereof is exceeded during operation - Google Patents
Waveguide termination with magnetic metal walls wherein the curie temperature thereof is exceeded during operation Download PDFInfo
- Publication number
- US3205459A US3205459A US273416A US27341663A US3205459A US 3205459 A US3205459 A US 3205459A US 273416 A US273416 A US 273416A US 27341663 A US27341663 A US 27341663A US 3205459 A US3205459 A US 3205459A
- Authority
- US
- United States
- Prior art keywords
- waveguide
- curie temperature
- guide
- dissipative
- power
- 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
Links
- 239000002184 metal Substances 0.000 title description 7
- 229910052751 metal Inorganic materials 0.000 title description 7
- 230000008859 change Effects 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000007769 metal material Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 description 16
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 5
- 230000035699 permeability Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000002238 attenuated effect Effects 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 239000000696 magnetic material Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000002500 effect on skin Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/24—Terminating devices
- H01P1/26—Dissipative terminations
- H01P1/264—Waveguide terminations
Definitions
- Dissipative loads are available in a variety of forms and may be required to absorb the total output power of a radio or radar transmitter when it is undesirable to radiate the power from an aerial. These conditions arise, for example, when setting up and adjusting a transmitter to its proper frequency and maximum power output.
- the so-called water load in which a flow of water is maintained through a dielectric tube located within a section of waveguide, can be used to absorb high-power energy, but its use depends on a plentiful water supply or requires a closed water-flow circuit including a heat exchanger. Moreover, the arrangement is fragile and the escape of water into the waveguide system could be disastrous.
- a lossy ceramic material has been used to form a thickwalled Waveguide with an internal taper for impedance matching purposes, energy being absorbed by the ceramic mass and radiated as heat. These also are mechanically weak both as regards the material itself, which is fran- A gible, and as regards the junction between the material and the metal flange which secures it to the waveguide system. This junction is liable to be broken by stresses due to differential expansion. Such material is porous and water absorbed by it may be released as steam to damage the structure when the system is in operation. The material may be shielded from the atmosphere by a metal cover but this cover must be in good thermal contact with the material and the risk of breakage through differential expansion is increased.
- An object of the invention is accordingly to provide for a waveguide system a high-power dissipative load which is to a large extent free from the disadvantages above set forth.
- a high-power dissipative load for a waveguide system includes a length of dissipative waveguide short-circuited at one end and made of magnetic metal material which has an electrical resistance such that energy introduced at the other end thereof during operation is sufficiently attenuated by the time it is received back at said other end after reflection at the short-circuited end.
- a dissipative load for a waveguide system includes a length of rectangular waveguide having the sectional dimensions appropriate to the system.
- the guide is coiled to form two flat helical coils 11 and 12, see the accompanying drawing, secured side by side on a frame, omitted from the drawing for clarity, which includes spacers between adjacent turns of each coil and, if necessary, is fitted with radiating fins to provide the necessary degree of heat dissipation.
- the inner ends of the coils are coupled together by a short portion of waveguide 13.
- the outer ends of the respective coils thus form the ends of the dissipative guide as a whole.
- the other end 15 is flanged for coupling to the waveguide system.
- the material of the guide is a magnetic nickel-iron alloy having an appreciable electrical resistance and a Curie temperature the values of which will be indicated shortly.
- the energy entering the guide from the system at end 15 gives rise to currents which, being at a high frequency, are confined by the skin effect to flow mainly in the interior surface regions of the guide walls.
- the skin depth and hence the cross section available for current flow is inversely dependent on the magnetic permeability of the guide material-that is, the skin depth is smaller with a magnetic material than with a nonmagnetic.
- the use for the guide walls of magnetic material of appreciable permeability instead of the usual non-magnetic material of unity permeability, together with the appreciable electrical resistance of the material, and possibly other magnetic loss mechanisms such as hysteresis imparts a heavy resistive loss to the energy throughout its double journey along the guide to the short circuit at 14 and back to the end 15.
- the resistance of the material is chosen such that, at the frequency concerned, this overall resistive loss has effected the required degree of attenuation by the time the energy is returned from the guide to the system.
- the energy dissipated appears as heat in the waveguide wall and the temperature reached at any point along the length of the guide depends on the power level at that point. Since the power level is being attenuated progressively along the guide a temperature gradient is produced. As the temperature coefficient of resistance of most suitable waveguide materials is positive, the resistivity of the hotter parts of the guide becomes higher than the resistivity of the cooler parts. The temperature gradient is therefore increased, since proportionately more power is now being dissipated in the hot parts near the entrance to the dissipative load.
- the material is chosen to have a Curie temperature which is reached through the resistive heating of the guide walls in dissipating energy above a predetermined power level.
- This power level is passed near the input end of the waveguide load but not over the whole length.
- the effect of reaching this temperature is to reduce the permeability of the guide material substantially to unity, thereby removing the source of magnetic losses; thus the attenuation over this part of the waveguide load is lowered and more power is transmitted to more distant cooler parts of the guide.
- the temperature in these more distant parts is increased, but beyond'a certain distance the power level is so attenuated that the Curie temperature is not reached. In this Way a more uniform temperature distribution is achieved and in particular the temperature near the input end of the waveguide load is prevented. from becoming so high as to encourage arcing of the radio frequency power across the guide due to ionised particles provided by burnt dust, etc.
- the nickel-iron alloy of the guide material has an electrical conductivity of approximately 16,000 mhos per centimetre cube and a magnetic'permeability of approximately 2 at room temperature and at the working frequency of 10,000 mc./s., the Curie point being 360 C.
- a dissipative guide of that material suitable for input powers of 2 or 3 kw. at the above frequency has a length of about 27 feet.
- the cold loss is'about 0.5 db per foot and the hot loss 0.3 db per foot for parts of the guide where the temperature is above the Curie level.
- a dissipative load in accordance with the invention is free from the disadvantage of the known kind in which the energy is absorbed in interior dielectric wedges and as a consequence there is poor heat transfer to the metal.
- a high-power dissipative load for a waveguide system including a length of dissipative waveguide short-' circuited at one end and having walls made of continuous magnetic metal material having a Curie temperature considerably above the ambient temperature, whereby parts of saidwalls are subject to a change in magnetic properties through resistive heating thereof to a teml perature above the Curie temperature during normal operation.
- dissipative waveguide is coiled to form two .fiat helical coils secured side by side and coupled together at their inner ends by a portion of waveguide extending parallel to the common axis of the coils, the said one end which is shortcircuited being one of the outer ends.
- a high-power dissipative load for a waveguide system including a length of dissipative waveguide shortcircuited at one end and having walls of uniform cross section made entirely of a magnetic nickel-iron alloy which has an electrical resistance such that energy introduced at the other end thereof during operation is sufliciently attenuated by the time it is received back at said other end after reflection at the short-circuited end, said electrical resistance being such that the resistive heating of said walls during normal operation is eifective' to raise the temperature of a part of the dissipative Waveguide above the'Curie temperature of said nickel-iron alloy, whereby said rise in temperature serves to change the magnetic properties of said part of the Waveguide.
Landscapes
- Non-Reversible Transmitting Devices (AREA)
- Constitution Of High-Frequency Heating (AREA)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB15703/62A GB1030225A (en) | 1962-04-25 | 1962-04-25 | Improvements relating to waveguide systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3205459A true US3205459A (en) | 1965-09-07 |
Family
ID=10063960
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US273416A Expired - Lifetime US3205459A (en) | 1962-04-25 | 1963-04-16 | Waveguide termination with magnetic metal walls wherein the curie temperature thereof is exceeded during operation |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3205459A (xx) |
| GB (1) | GB1030225A (xx) |
| SE (1) | SE314121B (xx) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3309634A (en) * | 1964-12-14 | 1967-03-14 | Hazeltine Research Inc | Transmission line attenuators for high power |
| US3940719A (en) * | 1974-10-25 | 1976-02-24 | Raytheon Company | Microwave waveguide dissipative load comprising fluid cooled lossy waveguide section |
| US3964072A (en) * | 1975-02-25 | 1976-06-15 | General Electric Company | Suppression of unwanted radiation from unavoidable openings in shielded enclosures |
| EP0191790A1 (en) * | 1984-07-30 | 1986-08-27 | The Commonwealth Of Australia | Waveguide delay |
-
1962
- 1962-04-25 GB GB15703/62A patent/GB1030225A/en not_active Expired
-
1963
- 1963-04-16 US US273416A patent/US3205459A/en not_active Expired - Lifetime
- 1963-04-24 SE SE4505/63A patent/SE314121B/xx unknown
Non-Patent Citations (1)
| Title |
|---|
| None * |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3309634A (en) * | 1964-12-14 | 1967-03-14 | Hazeltine Research Inc | Transmission line attenuators for high power |
| US3940719A (en) * | 1974-10-25 | 1976-02-24 | Raytheon Company | Microwave waveguide dissipative load comprising fluid cooled lossy waveguide section |
| US3964072A (en) * | 1975-02-25 | 1976-06-15 | General Electric Company | Suppression of unwanted radiation from unavoidable openings in shielded enclosures |
| EP0191790A1 (en) * | 1984-07-30 | 1986-08-27 | The Commonwealth Of Australia | Waveguide delay |
| EP0191790A4 (en) * | 1984-07-30 | 1987-01-20 | Commw Of Australia | Waveguide delay. |
Also Published As
| Publication number | Publication date |
|---|---|
| GB1030225A (en) | 1966-05-18 |
| SE314121B (xx) | 1969-09-01 |
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