The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 09, 1998
Filed:
Apr. 05, 1996
Eric B Rodal, Morgan Hill, CA (US);
Trimble Navigation Limited, Sunnyvale, CA (US);
Abstract
An apparatus including a hybrid digital-to-analog converter (DAC) (10) for converting a combined digital word (23) into a combined analog output level (21) and a GPS receiver (36) for providing the combined digital word (23) and using the combined analog output level (21) for phase locking a voltage controlled oscillator (VCO) (40) to a GPS satellite signal (34). The combined digital word (23) includes a more significant (MS) digital word (13) having N bits and a less significant (LS) digital word (15) having M bits. The hybrid DAC (10) includes a pulse generator DAC (12) for converting the MS digital word (13) into pulse output signal having a duty cycle and an average MS analog level representative of the MS digital word (13) and a second DAC (14) for converting the LS digital word (15) into an average LS analog level representative of the LS digital word (15). The pulse generator DAC (12) uses a counting technique in order to obtain a high degree of precision. A filter/combiner (18) filters and combines the average MS and the LS analog levels into a combined analog output level (21) representative of the combined digital word (21) to control the VCO (40) for providing a GPS-derived frequency signal (41) and a VCO signal to a correlator (38). The correlator (38) provides the combined digital word (23) representative of a difference between the frequency of the VCO signal and the frequency of the GPS satellite signal (34).