AltBOC for Dummies (797920), страница 3
Текст из файла (страница 3)
The carrier and sub-carrier replica shalloptimally be linear sin and cosine functions. A codetracking loop is not required once the code is+ j[c B (t ) − c A (t )]SC 4,sin (t )With SC4,cos (t ) and SC4,sin (t ) being the 4 statecosine and sine sub-carrier function defined so that(18) is true.(18)In fact, expression (17) gives the desired signal inan infinite bandwidth. But if the desired signal isfiltered in a bandwidth ranging from 50 Mhz up to190 Mhz, (the next harmonic of the desired subcarrier is at +/- 105 MHz), the desired signalsION GNSS 21st.
International Technical Meeting of theSatellite Division, 16-19, September 2008, Savannah, GA.I IΔ = RΔΔ (τˆ ) ⋅ sin(θˆ) ⋅ sin(φˆ)C Δ (τˆ )QIWe propose an innovative way to track the pilotcomponent of the Alt-BOC. Making abstraction ofthe data channel, which has orthogonal codes to thepilot channel, the pilot component can be seen as a2-code Alt-BOC, and therefore will have itsproperties described earlier.SC8,SSB (t ) = (SC4,cos (t ) + j SC4,sin (t ))Σ↓C Σ (τˆ )SCsin φˆSRFI IΣ = RΣΣ (τˆ ) ⋅ cos(θˆ) ⋅ cos(φˆ)C Δ (τˆ )IQcos θˆALT-BOC PILOT TRACKINGs (t ) = [c A (t ) + c B (t )]SC 4,cos (t )()SC cos φˆΣ↓C Σ (τˆ )969acquired, the code NCO can be driven by the subcarrier loop, as for BOC subcarrier tracking (See[8]).For example we could use the followingdiscriminators (many others are possible).- for the carrier loop :discricpilot =-discrisc1 =QI I I + QQ I QI I2 + I Q2 + QI2 + QQ21≈ sin (2θ )2REFERENCES[1] L Ries & al, « A Software Simulation Tool forGNSS2 BOC Signals », ION GPS 2002, September2002.[2] L Ries & al, « New Investigations on WidebandGNSS2 Signals », GNSS 2003, April 2003.[3] M.
Soellner and Ph. Erhard, « Comparison ofAWGN Code Tracking Accuracy for AlternativeBOC, Complex-LOC and Complex- BOCModulation Options in Galileo E5-Band », GNSS2003, April 2003.[4]. L. Lestarquit, « Method and device forgenerating a constant envelope navigation signalwith four independent codes »,US patn°2006/0038716 A1 published Feb. 23, 2006.[5] N. Martin, H. Guichon, M.
Revol, M.Hollreiser, J. De Mateo, « Architecture of thegalileo TUS receiver for coherent AltBOC tracking» , 3rd CNES-ESA Workshop on GNSS Signalsand Signal Processing, 21 & 22 April 2008 (IAS)Toulouse, France.[6] N. Gerein, «Hardware architecture forprocessing Galileo alternate binary offset carrier(Altboc) signals », published Jan.20, 2005.[7] N. Martin, V. Leblond “Method for theacquisition of a radio-navigation signal bysatellite”, published the 28th October 2004.[8] A. De Latour, T.
Grelier, G. Artaud , L. Ries, JL. Issler, V. Heiries« Subcarrier TrackingPerformances of BOC, ALTBOC and MBOCSignals » ION GNSS 2007 , International technicalmeeting, September 25-28, 2007, Fort Worth,Texas (US).[9]. A. Simsky, JM. Sleewaegen, M. Hollreiser, «Multipath and tracking performance of Galileoranging signals transmitted by the GIOVEAsatellite », First CNES-ESA Workshop on Galileosignals and signal processing, 12 & 13 october2006, IAS ( Institut Aero Spatial ) Toulouse,France.[10] G. Artaud, G. Menard, L. Ries, J.
Dantepal, JL.Issler “ Juzzle Software Receiver ”, Navitec 2006,11 – 14 december 2006, Noordwijk, theNetherlands.[11] E.Rebeyrol, “Galileo Signal and PayloadOptimisation”, Ph. D. Thesis, Oct. 9, 2007.(21)for the sub-carrier loop :I I I Q + QI QQI + QI2 + I Q2 + QQ22I1≈ sin (2φ )2(22)To sum-up, this receiver architecture achieves thetracking of the 2 sub-carriers that are formed inexpression (19), quite an original way to track theAlt-BOC signal.IONOSPHERIC DELAY FOR SUBCARRIERTRACKINGJust a short word about ionospheric delay.It is easy to show that the sub-carrier will beaffected by a group delay (that is same sign as thecode), and this delay is equal to :I SC =40.3TECfa fbCONCLUSIONTo sum up, the constant envelope Alt-BOC fulfillswhat it was designed for that is provide 2 QPSKnavigation signals at E5a and E5b.Fortunately, the transformation of the 4-code AltBoc to a constant envelope modulation doesn’tdegrade of make any power loss to the desiredsignal that is in the fundamental harmonic of thesubcarrier.The tracking of the Alt-BOC subcarrier of the pilotcomponent is possible and a receiver architecture isproposed.
Due to the SPD properties of the desiredsignal, it is optimal to do the subcarrier trackingwith a LOC sub-carrier.ION GNSS 21st. International Technical Meeting of theSatellite Division, 16-19, September 2008, Savannah, GA.970.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
