Glonass/GPS de-rotation and filtering with ADC sampling at 60-80 MSPS

32 Pages·2014·2.27 MB·English

US008604974B2
United States Patent
(12) (10) Patent N0.: US 8,604,974 B2
Ganeshan et al. (45) Date of Patent: Dec. 10, 2013
(54) GLONASS/GPS DE-ROTATION AND (58) Field of Classi?cation Search
FILTERING WITH ADC SAMPLING AT 60-80 USPC ............. .. 342/357.4, 357.46, 357.73, 357.77;
MSPS 375/340, 350, 355
See application ?le for complete search history.
(71) Applicant: Texas Instruments Incorporated,
Dallas’ TX (Us) (56) References Cited
(72) Inventors: Saravana Kumar Ganeshan, Kamataka U'S' PATENT DOCUMENTS
(IN); Bijoy Bhukanias Kamamka (IN); 7,346,134 B2 * 3/2008 Smith ,,,,,,,,,,,,,,,,,,,,,,,,, ,, 375/346
Allalld K311112111, Karnataka (1N) 2009/0068974 A1 * 3/2009 Smith . 455/304
(73) Assignee: Texas Instruments Incorporated, * Cited by examiner
Dallas’ TX (Us) Primary Examiner * Dao Phan
( * ) Notice: Subject to any disclaimer, the term of this (74) A210" "6)’; Age”?! 0" F17’ m * Lawrence J- Bassuk; Wade
patent is extended or adjusted under 35 J~ Brady’ HI; Fredenck J~Te1eCky> J1
U.S.C. 154(b) by 0 days.
(57) ABSTRACT
(21) APP1~ NOJ 13/850,802 An electronic circuit separates frequency-overlapped GLO
_ NASS and GPS overlapped in an approximately 4 MHZ pass
(22) Flled: Mar‘ 26’ 2013 band. The circuit uses a multiple-path analog-to-digital con
_ _ _ verter circuit (ADC). A sampling rate circuit is coupled to
(65) Pnor Pubhcatlon Data concurrently operate the analog-to-digital converter circuit at
US 2013/0229306 A1 Sep 5, 2013 a sampling rate between about 60 Msps and about 80 Msps. A
_ _ digital processing circuit includes storage de?ning complex
Related U's' Apphcatlon Data de-rotation and loW pass ?ltering. The digital processing cir
(62) Division of application No, 12/897,039, ?led on Oct, cuit is fed by the analog-to-digital converter circuit and is
4, 2010, now Pat, No, 8,427 ,366, operable A) to establish an access rate and respective distinct
phase increments for the complex de-rotation, B) to execute
(30) Foreign Application Priority Data the complex de-rotation by combinations of trigonometric
multiplications using the distinct phase increments approxi
Jul. 27, 2010 (IN) ......................... .. 2l3l/CHE/20l0 mately concurrently and C) to execute the low pass ?ltering
on the complex de-rotation resulting at the access rate and
(51) Int- Cl- respective distinct phase increments, thus delivering GPS and
Gols 19/33 (2010-01) Glonass signals separated from each other.
(52) US. Cl.
USPC ................................................... .. 342/357.73 19 Claims, 14 Drawing Sheets
222,224
I 40 410 GLONASS DIGITAL
\ \ = FILTER CHAIN —>
ANALOG IQ COMMON PART IQ (H9 7A)
TO DIGITAL ' / > OF DIGITAL ’ /
CONVERTER (FIG. 5) GPS D|G|TA|_
I > FILTER CHAIN —>
F (FIG. 7B)
1 45 / SAMP

US. Patent Dec. 10, 2013 Sheet 4 0f 14 US 8,604,974 B2
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US. Patent Dec. 10, 2013 Sheet 5 0f 14 US 8,604,974 B2
.1
FsAlvlP
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VCM
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FIG. 3D
US. Patent Dec. 10, 2013 Sheet 6 0f 14 US 8,604,974 B2
222,224
140 410 GLONASS DIGITAL
\ \ FILTER CHAIN _>
ANALOG IQ COMMON PART IQ (FIG-TA)
TO DIGITAL ' /> OF DIGITAL ’
CONVERTER (FIG. 5) GPS D|G|TA|_
T FILTER CHAIN _>
F (FIG. 7B)
145/ SAMP
FIG. 4
430 410
\ /
T0 DC DC OFFSET
CORRECTION<— HW ENGINE <_
DACs (F|G.1)
“sPuR
AGC HW PROGRAMMABLE
T v A
O 22;; ENGINE ‘H REAL NOTCH =
BLANK FREEZE F'LTER
JAMMER SPUR J’
IQMC $4
CALIBRATION
L4 55O\> t A
AOOIANOQ 1.4, f ‘ IQMC 1.7, >GLOT£ASS
CHANNEL ’ ' COMPENSATION ’ ' GPS
FIG. 5
US. Patent Dec. 10, 2013 Sheet 7 0f 14 US 8,604,974 B2