IS-GPS-200H (797934), страница 6
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The resultant nominalcomposite transmitted signal phases as a function of the binary state of only the two modulatingsignals are as shown in Table 3-IV.For Block IIR-M, IIF, and subsequent blocks of SVs, the two L2 carrier components shall beeither in phase quadrature or in the same phase (within ±100 milliradians) - see paragraph3.3.1.5.3 for additional information.
The civil signal carrier component is modulated by any oneof three (IIF) or four (IIR-M) different bit trains as described in paragraph 3.2.3. The resultantcomposite transmitted signal phases will vary as a function of the binary state of the modulatingsignals as well as the signal power ratio and phase quadrature relationship. Beyond theseconsiderations, additional carrier components in Block IIR-M, IIF, and subsequent blocks of SVswill result in composite transmitted signal phase relationships other than the nominal special caseof Table 3-IV. The current phase relationship of the two L2 carrier components (L2C andL2P(Y)) shall be indicated by means of bit 273 of the CNAV Type 10 Message (See section30.3.3), where zero indicates phase quadrature, with the L2C lagging the L2P(Y) by 90 degrees,and one indicates that L2C and L2P(Y) are in-phase.
If the CNAV message is not available, thenthe L2C and L2P(Y) shall be fixed in phase quadrature.3.3.1.5.2 Phase Crosstalk.For Block IIF, the crosstalk between the C/A, when selected, and P(Y) signals shall not exceed 20 dB in the L1 and L2. The crosstalk is the relative power level of the undesired signal to thedesired reference signal.3.3.1.5.3 Phase Continuity.While the satellite is broadcasting standard C/A, P(Y), and L2C codes with data that indicatesthat C/A, P(Y), and L2C signal health (respectively) is OK, there will not be any commandedoperation causing an intentional phase discontinuity.This does not apply to phasediscontinuities caused by signal modulation.
Prior to health data being available on L2C,satellites will be set unhealthy using the non-standard code.3.3.1.6 User-Received Signal Levels.The SV shall provide L1 and L2 navigation signal strength at end-of-life (EOL), worst-case, inorder to meet the minimum levels specified in Table 3-V. Any combining operation done by theSV and associated loss is compensated by an increase in SV transmitted power and thustransparent to the user segment. The minimum received power is measured at the output of a 3dBi linearly polarized user receiving antenna (located near ground) at worst normal orientation,when the SV is above a 5-degree elevation angle.
The received signal levels are observed withinthe in-band allocation defined in para. 3.3.1.1.The Block IIF SV shall provide L1 and L2 signals with the following characteristic: the L1 offaxis relative power (referenced to peak transmitted power) shall not decrease by more than 2 dB15IS-GPS-200H24 Sep 2013from the Edge-of-Earth (EOE) to nadir, nor more than 10 dB from EOE to 20 degrees off nadir,and no more than 18 dB from EOE to 23 degrees off nadir; the L2 off-axis power gain shall notdecrease by more than 2 dB from EOE to nadir, and no more than 10 dB from EOE to 23 degreesoff nadir; the power drop off between EOE and ±23 degrees shall be in a monotonicallydecreasing fashion.The GPS III SV shall provide L1 and L2 signals with the following characteristic: the L1 offaxis relative power (referenced to peak transmitted power) shall not decrease by more than 2 dBfrom the Edge-of-Earth (EOE) to nadir; the L2 off-axis power gain shall not decrease by morethan 2 dB from EOE to nadir; the power drop off between EOE and ±26 degrees shall be in amonotonically decreasing fashion.
Additional related data is provided as supporting material inparagraph 6.3.1.Table 3-IV. Composite L1 Transmitted Signal Phase ** (Block II/IIA and IIR SVs Only)Nominal Composite L1Signal Phase*0°-70.5°+109.5°180°**Code StatePC/A01010011*Relative to 0, 0 code state with positive angles leading and negative angles lagging.Based on the composite of two L1 carrier components with 3 dB difference in the power levels of the two.16IS-GPS-200H24 Sep 2013Table 3-Va. Received Minimum RF Signal Strength for Block IIA, IIR, IIR-M, IIF and III Satellites(20.46 MHz Bandwidth)SignalSV BlocksChannelP(Y)C/A or L2 CL1-161.5 dBW-158.5 dBWL2-164.5 dBW-164.5 dBWL1-161.5 dBW-158.5 dBWL2-161.5 dBW-160.0 dBWL1-161.5 dBW-158.5 dBWL2-161.5 dBW-158.5 dBWIIA/IIRIIR-M/IIFIIITable 3-Vb.
Received Minimum RF Signal Strength for GPS III (30.69 MHz Bandwidth)SignalSV BlocksChannelP(Y)C/A or L2 CL1-161.5 dBW-158.5 dBWL2-161.5 dBW-158.5 dBWIII3.3.1.6.1 Space Service Volume (SSV) User-Received Signal Levels.The SV shall provide L1 and L2 navigation signal strength at end-of-life (EOL), worst-case, inorder to meet the minimum levels specified in Table 3-Vc. The minimum received power ismeasured at the output of a 0 dBi right-hand circularly polarized (i.e. 0 dB axial ratio) userreceiving antenna at normal orientation, at the off-nadir angles defined in Table 3-Vc. Thereceived signal levels are observed within the in-band allocation defined in paragraph.
3.3.1.1.17IS-GPS-200H24 Sep 2013Table 3-Vc. Space Service Volume (SSV) Received Minimum RF Signal Strength for GPS III and SubsequentSatellites over the Bandwidth Specified in 3.3.1.1 – GEO Based AntennasSignalSV BlocksChannelOff Axis AngleRelative To NadirIII andSubsequentL123.5 deg-187.0 dBW*-184.0 dBW*L226.0 deg-186.0 dBW-183.0 dBWP(Y)C/A or L2 C* Over 99.5% of the solid angle inside a cone with its apex at the SV and measured from 0 degrees at the centerof the Earth3.3.1.7 Equipment Group Delay.Equipment group delay is defined as the delay between the signal radiated output of a specificSV (measured at the antenna phase center) and the output of that SV's on-board frequencysource; the delay consists of a bias term and an uncertainty.
The bias term is of no concern to theUS since it is included in the clock correction parameters relayed in the NAV data, and istherefore accounted for by the user computations of system time (reference paragraphs20.3.3.3.3.1, 30.3.3.2.3). The uncertainty (variation) of this delay as well as the group delaydifferential between the signals of L1 and L2 are defined in the following.3.3.1.7.1 Group Delay Uncertainty.The effective uncertainty of the group delay shall not exceed 3.0 nanoseconds (95% probability).3.3.1.7.2 Group Delay Differential.The group delay differential between the radiated L1 and L2 signals (i.e.
L1 P(Y) and L2 P(Y),L1 P(Y) and L2C) is specified as consisting of random plus bias components. The meandifferential is defined as the bias component and will be either positive or negative. For a givennavigation payload redundancy configuration, the absolute value of the mean differential delayshall not exceed 15.0 nanoseconds. The random plus non-random variations about the meanshall not exceed 3.0 nanoseconds (95% probability), when including consideration of thetemperature and antenna effects during a vehicle orbital revolution. Corrections for the biascomponents of the group delay differential are provided to the US in the NAV/CNAV messageusing parameters designated as TGD (reference paragraph 20.3.3.3.3.2) and Inter-SignalCorrection (ISC) (reference paragraph 30.3.3.3.1.1).3.3.1.7.3 Space Service Volume Group Delay Differential.The group delay differential between the radiated L1 and L2 signals with respect to the EarthCoverage signal for users of the Space Service Volume are provided inhttp://www.igs.org/products/ssv.18IS-GPS-200H24 Sep 20133.3.1.8 Signal Coherence.All transmitted signals for a particular SV shall be coherently derived from the same on-boardfrequency standard.
On the L1 carrier, the chip transitions of the modulating signals, C/A andL1P(Y), and on the L2 carrier the chip transitions of L2P(Y) and L2C, shall be such that theaverage time difference between the chips on the same carrier do not exceed 10 nanoseconds.The variable time difference shall not exceed 1 nanosecond (95% probability), when includingconsideration of the temperature and antenna effect changes during a vehicle orbital revolution.Corrections for the bias components of the time difference are provided to the US in the CNAVmessage using parameters designated as ISCs (reference paragraph 30.3.3.3.1.1).3.3.1.9 Signal Polarization.The transmitted signal shall be right-hand circularly polarized (RHCP).
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