開(kāi)始使用全球定位系統(tǒng)

　　本文著眼于從工業(yè)應(yīng)用的GPS設(shè)計(jì)開(kāi)始的選擇，從收發(fā)器到模塊和可用的評(píng)估板，以及考慮的天線問(wèn)題。它著眼于如何模塊供應(yīng)商如Antenova和恩智浦半導(dǎo)體可用于延伸到單個(gè)芯片實(shí)現(xiàn)準(zhǔn)則和Skyworks從。

　　導(dǎo)航和定位在許多設(shè)備中越來(lái)越受歡迎，從專用衛(wèi)星導(dǎo)航手機(jī)到移動(dòng)電話和汽車(chē)的集成。它們現(xiàn)在出現(xiàn)在數(shù)碼相機(jī)中，甚至用于跟蹤高價(jià)值的資產(chǎn)，使得導(dǎo)航技術(shù)的集成成為一個(gè)重要的設(shè)計(jì)元素。然而，這使數(shù)字處理、軟件、模擬和射頻設(shè)計(jì)專業(yè)知識(shí)匯集在一起，可能在一家公司中并不常見(jiàn)。

　　因此，供應(yīng)商正在提供用于評(píng)估衛(wèi)星導(dǎo)航設(shè)備的模塊，這些設(shè)備可直接用于中低容量設(shè)計(jì)。這避免了天線系統(tǒng)的RF和模擬設(shè)計(jì)的許多問(wèn)題，并允許開(kāi)發(fā)人員簡(jiǎn)單地、容易地向產(chǎn)品添加導(dǎo)航功能。對(duì)于更高容量的設(shè)計(jì)，單芯片導(dǎo)航設(shè)備提供更低的成本和更小的占用空間，但需要與諸如微控制器之類的其它設(shè)備進(jìn)行集成。

　　Despite the generic reference to ‘GPS’ systems， there are several satellite navigation systems emerging. A Global Navigation Satellite System （GNSS） receiver can cover the US GPS system， the Russian GLONASS， European Galileo， and Chinese Compass navigation satellite systems. These can be used as standalone navigation systems， taking signals from three out of seven visible satellites， although this can have a slow time to acquisition （TTA） to give an accurate reading of the location. These direct systems can also struggle in cities where ‘urban canyons’ limit how many satellites are visible. Similarly， there is a lot of work currently underway to improve the indoor capabilities of such systems.

　　The GPS L1 input signal is a spread-spectrum signal centered on 1575.42 MHz with a 1.023 Mbps BPSK modulation. The signal level at the antenna is typically -130 dBm in open-sky conditions， dropping to below -150 dBm in masked signal areas such as indoors.