Acquisition and Fine Acquisition of Weak GPSL2C and L5 Signals under High DynamicConditions for Limited-Resource Applications

摘要

Acquisition and fine acquisition algorithms are developedrnto work with weak L2C and L5 GPS signals. The algo-rnrithms utilize the structures and properties of the new sig-rnnals to achieve high performance with reduced processingrnand memory requirements. This is to allow the use of thernnew signals with applications that have limited resources.rnLong coherent and incoherent integrations are used, with-rnout requiring any assisting information. Correlation is per-rnformed using new versions of the modified Double BlockrnZero Padding (MDBZP) that was introduced for weak L1rnC/A signals.rnThe acquisition of the L2C signal consists of three stages:rnAcquisition of the CM signal; fine acquisition of the phase,rnDoppler shift and Doppler rate; and acquisition of the CLrnsignal. The acquisition of the I5 and Q5 channels is per-rnformed separately. The Q5 channel is used for the fine ac-rnquisition of the carrier.rnThe coherent integration used with the acquisition of thernL2C/CM code and the L5/I5 channel is a multiple of onerndata bit interval. The most likely data bit combination is es-rntimated over each PIT and used to remove the data bits priorrnto including each coherent integration result into a longer incoherent accumulation. The coherent integration used withrnthe data-less L2C/CL and Q5 channel can take any length.rnIn addition, a method is introduced to deal with the acquisi-rntion of high dynamic signalsrnThe performance of the developed algorithms are (lemon-rnstrated using simulated GPS signals with carrier to noise ra-rntio down to 10 dB-Hz, and TCXO clocks. The results havernshown the ability of the algorithms to work reliably withrnsuch weak signals.