Method and apparatus for precision ranging
US4895441A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 19, 1987 |
| Grant date | Jan 23, 1990 |
| Priority date | — |
| Expiry date | Mar 19, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S13/34
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An improved method and apparatus for precision ranging is described using a frequency-modulated signal source to stimulate creation of interference fringes at a rate proportional to absolute distance to a target. According to the invention, a low frequency modulating signal modulates a relatively high frequency signal source having a predetermined long coherent length compared to the distance to be measured. The resulting frequency-modulated signal is transmitted to the target to generate a reflected version thereof. Because of the long coherent length of the signal source, the transmitted frequency-modulated signal maintains spatial coherence as it travels to and from the target. Moreover, the low frequency modulating signal stimulates production of 360.degree. instantaneous phase differences between the transmitted and received frequency-modulated signals when these signals are superimposed. The number of these 360.degree. phase differences per period of the modulating signal is proportional to a time-of-flight of the transmitted frequency-modulated signal to and from the target and thus absolute distance. In operation, the transmitted and received frequency-modulated signals are…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.