| Revision as of 11:52, 19 April 2005 edit192.102.214.6 (talk)No edit summary | Latest revision as of 12:23, 26 December 2019 edit undoAvicBot (talk | contribs)Bots1,227,735 editsm Bot: Fixing double redirect to Satellite navigation deviceTag: Redirect target changed | ||
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| '''High Sensitivity ]''' receivers use large banks of correlators and digital signal processing to search for ] signals very quickly. This results in very fast times to first fix when the signals are at their normal levels, for example outdoors. When ] signals are weak, for example indoors, the extra processing power can be used to integrate weak signals to the point where they can be used to provide a position or timing solution. | |||
| ] signals are already very weak when they arrive at the Earth’s surface. The ] satellites have transmitters that only deliver 27 Watts from a distance of 20,200km in orbit above the Earth. By the time the signals arrive at the users receiver they are typically as weak as –160dBW, equivalent to one tenth of a millionth billionth of a Watt. This is well below the thermal noise level in its bandwidth. Outdoors ] signals are typically around the -155dBW level. | |||
| Conventional ] receivers integrate the received ] signals for the same amount of time as the duration of a complete C/A code cycle which is 1ms. This results in the ability to acquire and track signals down to around the -160dBW level. '''High Sensitivity ]''' receivers are able to integrate the incoming signals for up to 1,000 times longer than this and therefore acquire signals up to 1,000 times weaker. A good '''High Sensitivity ]''' receiver can acquire signals down to -185dBW, and tracking can be continued down to levels approaching -190dBW. | |||
| '''High Sensitivity ]''' can provide positioning in many but not all indoor locations. Signals are either heavily attenuated by the building materials or reflected in as ]. Given that '''High Sensitivity GPS''' receivers may be up to 30dB more sensitive this is sufficient to track through 3 layers of dry bricks or up to 20cm of steel reinforced concrete for example. | |||
Latest revision as of 12:23, 26 December 2019
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