US3769585A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for earth-space range measurements employing correction for ionospheric group delay
Assignee: SRI International Inc
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Filing: 1971-02-22
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Granted: 1973-10-30
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Expires: 1991-02-22
Abstract
Abstract Excess ionospheric group-delay correction by direct measurement along the transmission path of VHF signals employed for range finding is achieved by transmitting a signal having a triad of frequencies f+fm, f and f-fm. The triadic frequencies are first separated at the receiver. The frequency f is then mixed with each of the other two to obtain two differences. The phase difference Delta 2 phi between the two differences, i.e., the second difference of phase shift versus frequency, a measure of dispersion, is proportional to the integral of electron density along the path and, therefore, to excess inonospheric group delay. To make range corrections, the relationship of Delta 2 phi to Delta T (given at Delta T f/4 pi fm2 Delta 2 phi ) is used.
Inventors
- 👤 E Fremouw
- 👤 A Burns
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:12
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/02; G01S7/40; G01S13/00; G01S13/74; G01S13/82; G01S7/4052; G01S7/4082; G01S7/4091; H; H04; H04B; H04B7/00; H04B7/005
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
162 words
A method of measuring dispersion of a signal transmitted through a dispersive propagation medium between first and second points comprising the steps of transmitting from said first point to said second point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f-fm, mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), detecting the phase difference between said two difference signals to produce a signal which is closely proportional to said dispersion, and multiplying said signal proportional to said dispersion by a constant of proportionality to obtain an excess group delay value, wherein said constant of proportionality for an ionospheric propagation medium is equal to the value of f divided by 4 pi fm2.
Claim 2
Independent Claim
162 words
A method of measuring dispersion of a signal transmitted through a dispersive propagation medium between first and second points comprising the steps of transmitting from said first point to said second point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f-fm, mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), detecting the phase difference between said two difference signals to produce a signal which is closely proportional to said dispersion, and multiplying said signal proportional to said dispersion by a constant of proportionality to obtain an excess group delay value, wherein said constant of proportionality for an ionospheric propagation medium is equal to the value of f divided by 4 pi fm2.
Claim 3
Independent Claim
194 words
A method of making an excess group-delay correction for ranging between first and second points using a signal transmitted through a dispersive propagation medium between said points comprising the steps of transmitting from said first point to said second point with said ranging signal at said first point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, determining the transmission time of said ranging signal from said first point to said second point, separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f - fm), detecting the phase difference between said two difference signals to produce a correction signal as the second difference of phase shift versus frequency, a value which is closely proportional to said excess group delay, multiplying said correction signal by a constant of proportionality to obtain an excess group delay value, and subtracting said value from said transmission time.
Claim 4
Independent Claim
194 words
A method of making an excess group-delay correction for ranging between first and second points using a signal transmitted through a dispersive propagation medium between said points comprising the steps of transmitting from said first point to said second point with said ranging signal at said first point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, determining the transmission time of said ranging signal from said first point to said second point, separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f - fm), detecting the phase difference between said two difference signals to produce a correction signal as the second difference of phase shift versus frequency, a value which is closely proportional to said excess group delay, multiplying said correction signal by a constant of proportionality to obtain an excess group delay value, and subtracting said value from said transmission time.
Claim 5
Dependent Claim
29 words
A method as defined in claim 2 wherein said constant of proportionality for an ionospheric propagation medium is equal to the value of f divided by 4 pi fm2.
Claim 6
Dependent Claim
160 words
Apparatus for measuring dispersion of a signal transmitted through a dispersive propagation medium comprising means for transmitting from said first point to said second point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, means for separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, means for mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), means for detecting the phase difference between said two difference signals to produce a signal which is closely proportional to said dispersion, and means for multiplying said signal proportional to said dispersion by a constant of proportionality to obtain an excess group delay value, wherein said constant of proportionality is equal to the Value of f divided by 4 pi fm2.
Claim 7
Dependent Claim
160 words
Apparatus for measuring dispersion of a signal transmitted through a dispersive propagation medium comprising means for transmitting from said first point to said second point a triadic signal of three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, means for separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, means for mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), means for detecting the phase difference between said two difference signals to produce a signal which is closely proportional to said dispersion, and means for multiplying said signal proportional to said dispersion by a constant of proportionality to obtain an excess group delay value, wherein said constant of proportionality is equal to the Value of f divided by 4 pi fm2.
Claim 8
Dependent Claim
218 words
Apparatus for making an excess group-delay correction for ranging between first and second points using a signal transmitted through a dispersive propagation medium between said points comprising means for transmitting with said ranging signal from said first point a triadic signal to three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, means for receiving said ranging signal at said second point and for producing a signal proportional to the transmission time of said ranging signal from said first point to said second point, means for separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, means for mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), means for detecting the phase difference between said two difference signals to produce a correction signal as the second difference of phase shift versus frequency, a value which is closely proportional to said excess group delay, means for multiplying said correction signal by a constant of proportionality to obtain a signal representing an excess group delay value, and means for subtracting said excess group delay signal from said signal proportional to said transmission time.
Claim 9
Dependent Claim
218 words
Apparatus for making an excess group-delay correction for ranging between first and second points using a signal transmitted through a dispersive propagation medium between said points comprising means for transmitting with said ranging signal from said first point a triadic signal to three distinct frequencies f+fm, f and f-fm, where f and fm are distinct frequencies, means for receiving said ranging signal at said second point and for producing a signal proportional to the transmission time of said ranging signal from said first point to said second point, means for separating the frequencies of said triadic signal received at said second point into three distinct signals at said frequencies f+fm, f and f-fm, means for mixing said three distinct signals with each other to obtain two distinct difference signals of the same frequency as the frequency differences (f+fm) - f and f - (f-fm), means for detecting the phase difference between said two difference signals to produce a correction signal as the second difference of phase shift versus frequency, a value which is closely proportional to said excess group delay, means for multiplying said correction signal by a constant of proportionality to obtain a signal representing an excess group delay value, and means for subtracting said excess group delay signal from said signal proportional to said transmission time.
Claim 10
Dependent Claim
28 words
Apparatus as defined in claim 5 wherein said constant of proportionality for an ionospheric propagation medium is equal to the value of f divided by 4 pi fm2.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-29 | 1977-04-30 | 1977-10-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-29 | 1981-04-30 | 1981-10-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-29 | 1985-04-30 | 1985-10-30 | $7700.00 | Window Closed / Lapsed |