| 摘要 |
A system for locating forward observation posts with respect to a base station. A continuous electromagnetic wave with frequency fo is transmitted from an artillery projectile or missile in flight. In addition, a relative time code is transmitted on the same or a separate carrier frequency either from the projectile or from a ground station. The frequency fo of the electromagnetic wave from the projectile or missile is doppler shifted above or below its basic frequency due to the velocity of the projectile. This doppler signal fd always goes through its basic frequency fo or zero doppler at a point which is representative of and identifies an observer's position in the horizontal or subtrack direction of the projectile. This occurs regardless of the observer's distance away from the subtrack. Thus, all observers on a given perpendicular to the subtrack observe fo or zero doppler at the same time. To locate a specific observer, two projectiles or missiles must be fired. The observer is located at the intersection of two such perpendiculars. Any number of observers or sensors can be located with two projectiles or missiles. The relative time at which this zero doppler occurs for each observer is obtained from a time code transmission. This time code is also used to identify the position of the projectile at any time during its flight. The time of flight of the projectile until the referenced frequency is received, determined by each observation post, is sent to the base station so positions may be calculated from firing tables, from the projectiles velocity (only the horizontal component is required) or by actually counting cycles from the projectile to a reference base station, the cycles being equated to units of distance. A combination of the above can be used to improve the accuracy of locating any position of the projectile.
|
