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US2497093A - High-frequency wattmeter - Google Patents

High-frequency wattmeter Download PDF

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US2497093A
US2497093A US540827A US54082744A US2497093A US 2497093 A US2497093 A US 2497093A US 540827 A US540827 A US 540827A US 54082744 A US54082744 A US 54082744A US 2497093 A US2497093 A US 2497093A
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section
line
wattmeter
liquid
dielectric
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US540827A
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Moreno Theodore
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Sperry Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00—Arrangements for measuring electric power or power factor
    • G01R21/02—Arrangements for measuring electric power or power factor by thermal methods, e.g. calorimetric
    • G01R21/04—Arrangements for measuring electric power or power factor by thermal methods, e.g. calorimetric in circuits having distributed constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R21/00—Arrangements for measuring electric power or power factor

Definitions

  • This invention relates particularly to wattmeters and has reference more particularly to a novel calorimeter type of ultra high frequency wattmeter suitable for measuring the power in concentric lines and wave guides.
  • the novel wattmeter of this invention serves to dissipate the electromagnetic energy of the concentric line or waveguide directly in the coolant employed, thereby not only simplifying the structure of the wattmeter but also obtaining high accuracy in adapting the wattmeter for use in the high power ranges as well as for low powers.
  • the principal object of the present invention is to provide a novel high frequency wattmeter employing a coolant as the dielectric of a concentric line or Wave guide, as the case may be.
  • Another object of the present invention is to provide a novel wattmeter that has very broad band response, being operablersubstantially independent of frequency of the supplied energy over a wide band.
  • Still another object of the present invention is to provide a novel wattmcter of the above character especially valuable for use in the higher power ranges, said wattmeter being extremely accurate and of unvarying characteristics.
  • a further object of the present invention is to provide a novel wattmeter wherein the energyabsorbing medium is accurately matched to the supply line through the intermediary" of a line section employing a diierent suitable dielectric material such as polystyrene.
  • This line section performs the dual function of matching the liquid-filled section to the supply line and sealing the liquid in the line.
  • Fig. l is a perspective view, partly broken away, of one form of wattmeter of the present invention adapted for use in connection with a concentric line;
  • FIG. 2 is enlarged central sectional view of Y the structure of Fig. 1:
  • Fig. 3 is a sectional view of a somewhat modiiied construction
  • Fig. 3a is a fragmentary portion of the structure of Fig. 3 showing a somewhat modved construction
  • Fig. 4 illustrates the wattmeter of the present invention as applied to a waveguide.
  • an outer conductor I is shown mounted within a housing 2, the said conductor l having an inner conductor portion 3 surrounded by a liquid dielectric 4, which may be water for example, and which dielectric serves directly to absorb the electromagnetic energy travelling down the concentric line.
  • a liquid dielectric 4 which may be water for example, and which dielectric serves directly to absorb the electromagnetic energy travelling down the concentric line.
  • the increase in heat of the dielectric 4, which when taken with the rate of flow is a measure of the power, is indicated by calorimetric methods.
  • thermocouple arrangement In order to measure the amount of heat ab- ⁇ sorbed by the dielectric, i. e. to indicate the power of the line, a suitable thermocouple arrangement may be employed, using thermocouples 1 and 8 mounted in the tubes 6 and 5 respectively. the said thermocouples being connected to the meter 9 directly or through a suitable amplifier if desired. Means for measuring the rate of ow of the liquid is preferably employed to obtain uniform results. The meter 9 may be calibrated directly in power units if desired. Instead of using the thermocouple arrangement shown, it is possible to employ thermometers I0 and Il, as y shown in Fig. 3, mounted in the tubes 5 and 6 respectively and by subtracting the readings of the thermometers and measuring the rate of liquid ilow, the energy absorbed may be measured.
  • the length of liquid-filled line should be such as to provide suiicient attenuation so that the reflected wave of energy from the shorted end of the line is small enough to be neglected.
  • Ihe impedance of the liquid-lled line is then transformed to that of the air-filled line by the use of an intermediate section, which employs a solid dielectric such as polystyrene to provide a water seal.
  • the dimensions of this section of line employing a low-loss solid dielectric are chosen so that it will perform the required electrical transformation.
  • the transformation will be effected when the inter mediate section of line is electrically a quarterwavelength long and has a characteristic impedance that is the geometric mean of the characteristic impedances of the adioining air-filled and liquid-lled line sections.
  • the polystyrene section must be electrically a quarter wavelength, i. e. M4 long.
  • the impedance of the polystyrene section must be such as to match the air line section to the water line section.
  • Zo impedance of the air-filled line.
  • Zo/ ⁇ /75 impedance of the water-iilled line.
  • Za' impedance of the polystyrene line.
  • Zo Zo/751/4
  • the form of wattmeter so far described is somewhat limited in band width, it being noted that a deiinite length of transformer section is required for a given wavelength. In order to make this wattmeter present a matched impedance over a wide band of frequencies, it is necessary to choose the diameters of the polystyrene and water-lled sections so as to maintain a constant impedance along the line (neglecting the phase angle in the characteristic impedance of the water section).
  • the radius of the inner conductor a' in the dielectric filled region should be d an (5)# where a is the inner radius of the air-fllled line,
  • b is the outer radius of both lines
  • e is the dielectric constant of the dielectric medium separating the conductors.
  • a constant impedance wattmeter is shown in Fig. 3.
  • the outer conductor is designated I6 and the small inner conductor of the water-filled line is designated I1
  • Il is the polystyrene section, which may be quite short, and not necessarily a quarter-wavelength in length.
  • 'I'he inner conductor of the air-filled line is designated I9 and that of the polystyrene section is designated 20.
  • the small central conductor of the liquid dielectric line section can be reinforced by suitable means.
  • suitable means such as a polystyrene coating shown at 2i in Fig. 3a and the diameters adjusted tov maintain a constant impedance.
  • the central conductor becomes extremely small, i. e., 00053" radius, if it is desired to have the wattmeter matched at all wavelengths for which there is suiiicient attenuation in the water-filled line.
  • water as the power absorbing liquid
  • the diameter of such water filled line is reduced a practical'amount to, say, .050" and the polystyrene section designed to match such a line to the air-filled line, the band width over which the wattmeter is matched will be considerably increased over that shown in Figs. l and 2.
  • the novel wattmeter of this invention is not designed for use in connection with concentric lines alone, but the same may also be used in connection with waveguides.
  • the structure shown in Fig. 4 illustrates the wattmeter applied to a waveguide.
  • the waveguide 22 is shown having a water-filled section 22' through which the water is circulated as shown in connection with Figs. 1 and 2.
  • a metal insert 23 is employed together with a polystyrene insert 24, these inserts being electrically a quarter-wavelength in length.
  • the wattmeter will remain matched as long as there is sufiicient attenuation in the water-filled section, so that reflections from the end of the line will be negligible, and this attenuation per unit length would be linearly proportional to the frequency if the dielectric constant and power factor of water remained unchanged with changing frequency.
  • a microwave wattmeter comprising a coaxial transmission line having a liquid filled section, temperature responsive means for measuring power absorbed by said liquidfilled section, said liquid serving as a dielectric power absorbing medium a supply line section. and a matching section between saidv supply line section and said liquid iilled section, said matching section including inner and outer conductors whose diameters bear a different ratio to each other than the inner and outer conductors of said liquid iilled section, and a body oi' solid. dielectric material lling the space between said conductors in said matching section, said body acting as a seal to maintain said liquid in said liquid lled section.
  • a microwave wattmeter comprising a coaxial transmission line having a liquid lled section, temperature responsive means for measuring power absorbed by said liquid illled section, said liquid serving as a dielectric power absorbing medium a supply line section, and a matching section between said supply line section and said liquid lled section, said matching'section including an inner conductor whose diameter is' substantially greater than that of the inner conductor of said liquid lled section, and a body of solid dielectric material lling the space between said conductors in said matching section,

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Non-Reversible Transmitting Devices (AREA)

Description

Feb. 14, 1950 T. MORENO HIGH-FREQUENCY WATTMETER 2 Sheets-Sheet 1 Filed June 1'7, 1944 INVENTOR THEODORE MORENO Patented Feb. 14, 195o HIGH-FREQUENCY WATTIKETER Theodore Moreno, Garden City, N. Y., assigner to The Sperry Corporation, a corporation of Dela- Application June 17, 1944, serial' No. 540,821
2 Claims.
This invention relates particularly to wattmeters and has reference more particularly to a novel calorimeter type of ultra high frequency wattmeter suitable for measuring the power in concentric lines and wave guides.
The novel wattmeter of this invention serves to dissipate the electromagnetic energy of the concentric line or waveguide directly in the coolant employed, thereby not only simplifying the structure of the wattmeter but also obtaining high accuracy in adapting the wattmeter for use in the high power ranges as well as for low powers.
The principal object of the present invention is to provide a novel high frequency wattmeter employing a coolant as the dielectric of a concentric line or Wave guide, as the case may be.
Another object of the present invention is to provide a novel wattmeter that has very broad band response, being operablersubstantially independent of frequency of the supplied energy over a wide band.
Still another object of the present invention is to provide a novel wattmcter of the above character especially valuable for use in the higher power ranges, said wattmeter being extremely accurate and of unvarying characteristics.
A further object of the present invention is to provide a novel wattmeter wherein the energyabsorbing medium is accurately matched to the supply line through the intermediary" of a line section employing a diierent suitable dielectric material such as polystyrene. This line section performs the dual function of matching the liquid-filled section to the supply line and sealing the liquid in the line.
Other objects and advantages will become apparent from the specification, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.
In the drawings,
Fig. l is a perspective view, partly broken away, of one form of wattmeter of the present invention adapted for use in connection with a concentric line; t
Fig. 2 is enlarged central sectional view of Y the structure of Fig. 1:
Fig. 3 is a sectional view of a somewhat modiiied construction;
Fig. 3a is a fragmentary portion of the structure of Fig. 3 showing a somewhat modiiled construction; and
Fig. 4 illustrates the wattmeter of the present invention as applied to a waveguide.
Similar characters of reference are used in all 2 of the above figures to. indicate corresponding parts.
Referring now to the structure illustrated in Figs. l and 2 of the drawings of the novel wattmeter of this invention, an outer conductor I is shown mounted within a housing 2, the said conductor l having an inner conductor portion 3 surrounded by a liquid dielectric 4, which may be water for example, and which dielectric serves directly to absorb the electromagnetic energy travelling down the concentric line. The increase in heat of the dielectric 4, which when taken with the rate of flow is a measure of the power, is indicated by calorimetric methods.
`In the drawing the dielectric is shown circulating within the concentric line section surrounding the inner conductor portion 3. ',I'o .facilitate this circulation, tubes 5 and 6 are attached to the outer conductor, one at each end of the liquid dielectric section, and the liquid dielectric is forced through these tubes via branch tubes 5' and 6', thereby maintaining a steady ilow of dielectric in surrounding relation to inner conductor 3 and within the outer conductor. I.
In order to measure the amount of heat ab-` sorbed by the dielectric, i. e. to indicate the power of the line, a suitable thermocouple arrangement may be employed, using thermocouples 1 and 8 mounted in the tubes 6 and 5 respectively. the said thermocouples being connected to the meter 9 directly or through a suitable amplifier if desired. Means for measuring the rate of ow of the liquid is preferably employed to obtain uniform results. The meter 9 may be calibrated directly in power units if desired. Instead of using the thermocouple arrangement shown, it is possible to employ thermometers I0 and Il, as y shown in Fig. 3, mounted in the tubes 5 and 6 respectively and by subtracting the readings of the thermometers and measuring the rate of liquid ilow, the energy absorbed may be measured.
In order that the wattmeter present a matched load to the line, the length of liquid-filled line should be such as to provide suiicient attenuation so that the reflected wave of energy from the shorted end of the line is small enough to be neglected. Ihe impedance of the liquid-lled line is then transformed to that of the air-filled line by the use of an intermediate section, which employs a solid dielectric such as polystyrene to provide a water seal. The dimensions of this section of line employing a low-loss solid dielectric are chosen so that it will perform the required electrical transformation. For example, the transformation will be effected when the inter mediate section of line is electrically a quarterwavelength long and has a characteristic impedance that is the geometric mean of the characteristic impedances of the adioining air-filled and liquid-lled line sections.
This is an approximation that neglects any imaginary component in the characteristic impedances of these adjoining line sections. but these imaginary components, if they are ap'- preciable, may be taken into .account by more precise calculations. Y
The following is a typical approximate calculation, such as is performed in designing a wattmeter of this type.
The loss per unit length in the water-filled line is given by a=2"1.3 um y cia/unit length wherein Assuming that er' is equal to 75, and the tangent of i' equal to .13,
20 db. are ample for a termination, so ten inches of water line would be suitable. The polystyrene section must be electrically a quarter wavelength, i. e. M4 long.
The impedance of the polystyrene section must be such as to match the air line section to the water line section.
Zo=impedance of the air-filled line. Zo/\/75=impedance of the water-iilled line. Za'=impedance of the polystyrene line. Zo=Zo/751/4 The form of wattmeter so far described is somewhat limited in band width, it being noted that a deiinite length of transformer section is required for a given wavelength. In order to make this wattmeter present a matched impedance over a wide band of frequencies, it is necessary to choose the diameters of the polystyrene and water-lled sections so as to maintain a constant impedance along the line (neglecting the phase angle in the characteristic impedance of the water section). For the impedance in the dielectriciilled line section to be equal to that of the airiilled line, the radius of the inner conductor a' in the dielectric filled region should be d an (5)# where a is the inner radius of the air-fllled line,
b is the outer radius of both lines, and
e is the dielectric constant of the dielectric medium separating the conductors.
For example, if 2b=.805, 2a=.375. pou.=2.52
a' in the polystyrene dielectric region:
'water-:75 a' in the water dielectric region:
Such a constant impedance wattmeter is shown in Fig. 3. In this iigure, the outer conductor is designated I6 and the small inner conductor of the water-filled line is designated I1, while Il is the polystyrene section, which may be quite short, and not necessarily a quarter-wavelength in length. 'I'he inner conductor of the air-filled line is designated I9 and that of the polystyrene section is designated 20.
Also, if desired, the small central conductor of the liquid dielectric line section can be reinforced by suitable means. such as a polystyrene coating shown at 2i in Fig. 3a and the diameters adjusted tov maintain a constant impedance.
It will be noted that with water as the power absorbing liquid, the central conductor becomes extremely small, i. e., 00053" radius, if it is desired to have the wattmeter matched at all wavelengths for which there is suiiicient attenuation in the water-filled line. However, it should be noted that it is not necessary to use water as the absorbing liquid. Some other liquid could be used having a lower dielectric constant. Also, if the diameter of such water filled line is reduced a practical'amount to, say, .050", and the polystyrene section designed to match such a line to the air-filled line, the band width over which the wattmeter is matched will be considerably increased over that shown in Figs. l and 2.
The novel wattmeter of this invention is not designed for use in connection with concentric lines alone, but the same may also be used in connection with waveguides. The structure shown in Fig. 4 illustrates the wattmeter applied to a waveguide. In this structure the waveguide 22 is shown having a water-filled section 22' through which the water is circulated as shown in connection with Figs. 1 and 2. In order to match the impedance of the air-filled line with that of section 22', a metal insert 23 is employed together with a polystyrene insert 24, these inserts being electrically a quarter-wavelength in length. It will'be borne in mind that the wattmeter will remain matched as long as there is sufiicient attenuation in the water-filled section, so that reflections from the end of the line will be negligible, and this attenuation per unit length would be linearly proportional to the frequency if the dielectric constant and power factor of water remained unchanged with changing frequency.
Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
What is claimed is:
l. A microwave wattmeter comprising a coaxial transmission line having a liquid filled section, temperature responsive means for measuring power absorbed by said liquidfilled section, said liquid serving as a dielectric power absorbing medium a supply line section. and a matching section between saidv supply line section and said liquid iilled section, said matching section including inner and outer conductors whose diameters bear a different ratio to each other than the inner and outer conductors of said liquid iilled section, and a body oi' solid. dielectric material lling the space between said conductors in said matching section, said body acting as a seal to maintain said liquid in said liquid lled section.
2. A microwave wattmeter comprising a coaxial transmission line having a liquid lled section, temperature responsive means for measuring power absorbed by said liquid illled section, said liquid serving as a dielectric power absorbing medium a supply line section, and a matching section between said supply line section and said liquid lled section, said matching'section including an inner conductor whose diameter is' substantially greater than that of the inner conductor of said liquid lled section, and a body of solid dielectric material lling the space between said conductors in said matching section,
6 said body acting as a seal to maintain said liquid in said liquid lled section.
THEODORE MORENO.
REFERENCES CITED The following references are of record in the iile of this patent:
UNITED STATES PATENTS
US540827A 1944-06-17 1944-06-17 High-frequency wattmeter Expired - Lifetime US2497093A (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2576060A (en) * 1945-08-08 1951-11-20 James M Wolf Radio-frequency calorimeter wattmeter
US2669696A (en) * 1949-12-10 1954-02-16 Collins Radio Co High powered wave guide load
US2802986A (en) * 1945-08-23 1957-08-13 David G Chase Method of and an apparatus for measuring radio-frequency power
US2854627A (en) * 1954-11-17 1958-09-30 Hewlett Packard Co Calorimeter
DE1090757B (en) * 1957-01-11 1960-10-13 Varian Associates Broadband centimeter wave power meter
US3110872A (en) * 1962-04-16 1963-11-12 Giordano Salvatore Radio frequency attenuator
US3360750A (en) * 1965-07-23 1967-12-26 Varian Associates High frequency waveguide load comprising a dielectric window in contact with lossy coolant fluid
US3544923A (en) * 1969-10-30 1970-12-01 Varian Associates Microwave waveguide water load employing a quarter wave window of reduced characteristic impedance

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1957454A (en) * 1933-06-21 1934-05-08 Louis A Gebhard Power output indicator for high frequency apparatus
US1959356A (en) * 1933-06-21 1934-05-22 Louis A Gebhard Measuring system for high frequency apparatus
US2151118A (en) * 1935-10-30 1939-03-21 Bell Telephone Labor Inc Termination for dielectric guides
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2262134A (en) * 1938-08-31 1941-11-11 Rca Corp Ultrahigh frequency transmission line termination
US2267268A (en) * 1938-03-03 1941-12-23 Bell Telephone Labor Inc High frequency transmission system
US2282317A (en) * 1940-12-31 1942-05-12 Okonite Co Method of and apparatus for the electrostatic curing of heat curable materials, while under pressure
US2284379A (en) * 1939-12-29 1942-05-26 Rca Corp Ultra high frequency voltmeter
US2333143A (en) * 1940-05-31 1943-11-02 Okonite Co Process of and apparatus for the heat curing of materials
US2365207A (en) * 1944-12-19 High-frequency thermocouple
US2398606A (en) * 1943-03-27 1946-04-16 Westinghouse Electric Corp Ultra high frequency power measurement
US2427094A (en) * 1943-08-31 1947-09-09 Rca Corp Super-high-frequency wattmeter

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2365207A (en) * 1944-12-19 High-frequency thermocouple
US1957454A (en) * 1933-06-21 1934-05-08 Louis A Gebhard Power output indicator for high frequency apparatus
US1959356A (en) * 1933-06-21 1934-05-22 Louis A Gebhard Measuring system for high frequency apparatus
US2151118A (en) * 1935-10-30 1939-03-21 Bell Telephone Labor Inc Termination for dielectric guides
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2267268A (en) * 1938-03-03 1941-12-23 Bell Telephone Labor Inc High frequency transmission system
US2262134A (en) * 1938-08-31 1941-11-11 Rca Corp Ultrahigh frequency transmission line termination
US2284379A (en) * 1939-12-29 1942-05-26 Rca Corp Ultra high frequency voltmeter
US2333143A (en) * 1940-05-31 1943-11-02 Okonite Co Process of and apparatus for the heat curing of materials
US2282317A (en) * 1940-12-31 1942-05-12 Okonite Co Method of and apparatus for the electrostatic curing of heat curable materials, while under pressure
US2398606A (en) * 1943-03-27 1946-04-16 Westinghouse Electric Corp Ultra high frequency power measurement
US2427094A (en) * 1943-08-31 1947-09-09 Rca Corp Super-high-frequency wattmeter

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2576060A (en) * 1945-08-08 1951-11-20 James M Wolf Radio-frequency calorimeter wattmeter
US2802986A (en) * 1945-08-23 1957-08-13 David G Chase Method of and an apparatus for measuring radio-frequency power
US2669696A (en) * 1949-12-10 1954-02-16 Collins Radio Co High powered wave guide load
US2854627A (en) * 1954-11-17 1958-09-30 Hewlett Packard Co Calorimeter
DE1090757B (en) * 1957-01-11 1960-10-13 Varian Associates Broadband centimeter wave power meter
US3110872A (en) * 1962-04-16 1963-11-12 Giordano Salvatore Radio frequency attenuator
US3360750A (en) * 1965-07-23 1967-12-26 Varian Associates High frequency waveguide load comprising a dielectric window in contact with lossy coolant fluid
US3544923A (en) * 1969-10-30 1970-12-01 Varian Associates Microwave waveguide water load employing a quarter wave window of reduced characteristic impedance

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