Rd Order Pll - Safran CORTEX CRT Quantum User Manual

rd
3.3.3.2. 3 Order PLL
The 3rd order loop is used when you have to manage not only Doppler, but also Doppler Rate.


Example: With the same conditions as the 2
track an infinite Doppler rate. The limitation is now on the acceleration of the Doppler shift.
rd
The 3 order loop relaxes the Doppler rate constraint; phase bias is not generated any more by the Doppler rate
but by Doppler acceleration according to the following formula:
In the same idea, the value of
the value is equal to �� ~ 130.
The limitation is done with the kind of equation as 2
The graph below shows the theoretical tracking capacity of the 3
DS is lower (typically ½ the theoretical limit).
1.000E+00
.100E+00
.010E+00
.001E+00
1.000E-04
.100E-04
.010E-04
10
© Safran Data Systems
COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Doppler Rate is the derivative of the Frequency Shift. Unit is Hz.s
Doppler Acceleration is the derivative of Doppler Rate. Unit is Hz.s
nd
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is resulting from internal optimization and experience. In the Cortex CRT-DS,
Max Doppler Acceleration
15 20
Figure 25: 3rd Order PLL Tracking capacity
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rd
order loop, with the 3
× ��������������������������������������
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nd
order loop, i.e �� + ���� <
rd
order PLL. The real limit on the Cortex CRT-
25 30 35
C/N0 (dB.Hz)
Safran Data Systems
.
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
-1
-2
order loop, you are theoretically able to
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.
2
40 45 50
30 Hz
10 Hz
3 Hz
1 Hz
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