Pseudo-Noise (PN) Ranging Systems - CCSDS

CCSDS INFORMATIONAL REPORT CONCERNING PSEUDO-NOISE RANGING SYSTEMS
– BL=1 Hz;
– chip rate Fc = 2.068 Mchip/s (fRC= Fc/2);
– PR/N0 =30 dBHz:
And finally:
a) T4B: N = P N − LOG ( ξ ) ≈ 29.
45
PRC 0 R 0 20 10 1 dBHz;
b) T2B: N = P N − LOG ( ξ ) ≈ 25.
95
Sequence
PRC 0 R 0 20 10 1 dBHz.
Table 2-9: Station Ranging Jitter Performances
σ Range _ CTL _ sine _ sine σ Range _ CTL _ sine _ sq σ Range_ CTL_
sq_
sq
T4B 0.78 m 0.87 m 1.22 m
T2B 1.17 m 1.29 m 1.82 m
As above underlined, the expressions for the on-board tracking jitter are relevant to a
theoretical CTL behavior; for this reason the Blue Book specifies in addition a value of 2 dB
for the implementation losses. These losses take into account the contributions due to signal
quantization and non-perfect carrier tracking and signal demodulation.
Concerning the signal quantization effects: the signal amplitude quantization (in terms of
number of bit), the time sampling (i.e., finite number of samples per chip) and the chip
asymmetry.
The effects due to amplitude quantization and the chip asymmetry can be considered in
general negligible. Different is the situation for the time sampling. Taking into account that
the sampling frequency is equal to FS, this contribution ( σ εQ
) can be estimated as:
1 1
σ εQ
= (s)
12 F
For instance, at FS = 20 MHz there is an rms error of 14 ns (2.1 m one-way), bigger than the
theoretical values related to the thermal noise at PR/N0=30 dBHz and for BL=1 Hz.
Concerning the time sampling contribution:
– it is constant and independent from the signal to noise ratio’
– at low loop SNR, it is masked by the jitter due to the thermal noise;
– as the thermal jitter, it can be reduced with average processing at ground station.
CCSDS 414.0-G-1 Page 2-35 March 2010
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