US3890571A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radio frequency polarimeter
Assignee: International Telecommunications Satellite Organization
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Filing: 1973-10-17
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Granted: 1975-06-17
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Expires: 1993-10-17
Abstract
Abstract A radio frequency polarimeter is disclosed for measuring the polarization characteristics of an RF signal existing in a round wave guide. The polarimeter includes an RF pick-up head, an RF switch, an RF to IF converter, and switched IF attenuators. One of the IF attenuators is fixed while the other is a precision variable attenuator. The output of the switched IF attenuators is synchronously detected. The polarimeter permits measurement with a high degree of precision and accuracy of both the axial ratio and the relative alignment of the polarization ellipse.
Inventors
- 👤 John P Beyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 23:46
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/08; G01R29/0864; G01R29/0892
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
234 words
A radio frequency polarimeter for measuring the axial ratio and orientation of the principle axis of elliptically polarized electromagnetic signals, comprising: a radio frequency pickup head having a rotatable member and means for measuring radio frequency power at two positions about said head angularly displaced by 90*; a radio frequency switch connected to receive as two inputs the radio frequency power measured at said two positions; converter means connected to the output of said radio frequency switch for converting radio frequency power to an intermediate frequency power; a first intermediate frequency switch connected to the output of said converter means and providing two outputs; a fixed intermediate frequency attenuator connected to one output and a variable attenuator connected to the other output of said first intermediate frequency switch; a second intermediate frequency switch having two inputs connected respectively to said fixed and variable attenuators; switch control means connected to said radio frequency switch and said first and second intermediate frequency switches for causing said switches to operate in synchronism, the frequency of said switch control means being greater than the fluctuations in the signal strength of said elliptically polarized electromagnetic signals; and synchronous detector means connected to the output of said second intermediate frequency switch and providing an output indication proportional to the difference in the power measured at said two positions as modified by the switched gains of said fixed and variable attenuators.
Claim 2
Dependent Claim
234 words
A radio frequency polarimeter for measuring the axial ratio and orientation of the principle axis of elliptically polarized electromagnetic signals, comprising: a radio frequency pickup head having a rotatable member and means for measuring radio frequency power at two positions about said head angularly displaced by 90*; a radio frequency switch connected to receive as two inputs the radio frequency power measured at said two positions; converter means connected to the output of said radio frequency switch for converting radio frequency power to an intermediate frequency power; a first intermediate frequency switch connected to the output of said converter means and providing two outputs; a fixed intermediate frequency attenuator connected to one output and a variable attenuator connected to the other output of said first intermediate frequency switch; a second intermediate frequency switch having two inputs connected respectively to said fixed and variable attenuators; switch control means connected to said radio frequency switch and said first and second intermediate frequency switches for causing said switches to operate in synchronism, the frequency of said switch control means being greater than the fluctuations in the signal strength of said elliptically polarized electromagnetic signals; and synchronous detector means connected to the output of said second intermediate frequency switch and providing an output indication proportional to the difference in the power measured at said two positions as modified by the switched gains of said fixed and variable attenuators.
Claim 3
Dependent Claim
124 words
A polarimeter as recited in claim 1 wherein said synchronous detecting means includes: power detector means providing a square wave output having an amplitude proportional to the difference in the power measured at said two positions as modified by the switched gains of said fixed and variable attenuators and a frequency equal to the switching frequency of the said first and second intermediate frequency switches; a synchronous detector connected to said switch control means and receiving the output of said power detector means; integrating means connected to the output of said synchronous detector and providing an output DC voltage proportional to the amplitude of said square wave output of said power detector means; and indicating means connected to the output of said integrating means.
Claim 4
Dependent Claim
16 words
A polarimeter as recited in claim 2 wherein said power detector means is a square-law detector.
Claim 5
Dependent Claim
15 words
A polarimeter as recited in claim 2 wherein said integrating means is a low-pass filter.
Claim 6
Dependent Claim
45 words
A polarimeter as recited in claim 1 wherein said radio frequency pickup head includes: a circular wave guide input; a slip joint permitting the rotation of a terminating section of said circular wave guide; and first and second orthogonal linear probes in said terminating section.
Claim 7
Dependent Claim
164 words
A polarimeter as recited in claim 5 wherein said slip joint is provided with a calibrated vernier scale for indicating angular displacement and said synchronous switching means includes: a radio frequency switch connected to receive as two inputs the outputs of said first and second orthogonal linear probes; converter means connected to the output of said radio frequency switch for converting radio frequency power to an intermediate frequency power; a first intermediate frequency switch connected to the output of said converter means and providing two outputs; a fixed intermediate frequency attenuator connected to one output and a variable attenuator connected to the other output of said intermediate frequency switch, said variable attenuator being provided with a manually adjustable dial calibrated in decibels; a second intermediate frequency switch having two inputs connected respectively to said fixed and variable attenuator; and switch control means connected to said radio frequency switch and said first and second intermediate frequency switches for causing said switches to operate in synchronism.
Claim 8
Independent Claim
219 words
A method of measuring the axial ratio and orientation of the principle axis of elliptically polarized electromagnetic signals comprising: measuring the maximum linear power difference between two orthogonal positions about the axis of propagation of said electromagnetic signal, synchronously switching the measuring power into two channels, synchronously detecting the output of the two channels and adjusting the relative gain of the two channels to reduce the detected power difference to a null, repeating the measurement of the maximum linear power difference between two orthogonal positions rotated 90* with respect to the first two positions, synchronously switching the second measured power into two channels, synchronously detecting the output of the two channels and adjusting the relative gain of the two channels to reduce the detected power difference to a second null, computing the axial ratio as one-half the difference in the relative gains obtained in the first and second adjustments of the relative gains of the two channels to produce the first and second nulls, adjusting the relative gain of the two channels midway between the relative gains which produce the first and second nulls, and measuring the minimum power difference between orthogonal positions rotated approximately 45* between the first and second two orthogonal positions to produce a third null as a measurement of the orientation of the elliptical axis.
Claim 9
Independent Claim
219 words
A method of measuring the axial ratio and orientation of the principle axis of elliptically polarized electromagnetic signals comprising: measuring the maximum linear power difference between two orthogonal positions about the axis of propagation of said electromagnetic signal, synchronously switching the measuring power into two channels, synchronously detecting the output of the two channels and adjusting the relative gain of the two channels to reduce the detected power difference to a null, repeating the measurement of the maximum linear power difference between two orthogonal positions rotated 90* with respect to the first two positions, synchronously switching the second measured power into two channels, synchronously detecting the output of the two channels and adjusting the relative gain of the two channels to reduce the detected power difference to a second null, computing the axial ratio as one-half the difference in the relative gains obtained in the first and second adjustments of the relative gains of the two channels to produce the first and second nulls, adjusting the relative gain of the two channels midway between the relative gains which produce the first and second nulls, and measuring the minimum power difference between orthogonal positions rotated approximately 45* between the first and second two orthogonal positions to produce a third null as a measurement of the orientation of the elliptical axis.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |