COMMAND RANGING & TELEMETRY UNIT CORTEX
CRT QUANTUM USER'S MANUAL
Ref. DTU 100042
Is.Rev. 5.17
Date: Dec.
03, 2021Sept. 30, 2021
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It cannot be duplicated or distributed without expressed written consent.
3.3.1.3.4. Multi-Symbol PCM/FM Demodulator – Parameters recommended setting
3.3.1.3.4.1. Introduction
Several parameters are available for configuring the MS/FM demodulator. These parameters are described in the
STI 100013_TTC document (refer to “IF receiver Extension” table). Recommendations to set these parameters
are given below.
3.3.1.3.4.2. Modulation index
Using the legacy FM demodulation (when MS-FM is turned off), the demodulator is able to withstand a non-
accurate modulation index. However, with MS-FM demodulation, inaccuracies of modulation index are a critical
point for the receiver performances. The MS/FM receiver must take into account the actual value of the FM
modulation index to work properly and keep the benefits of MS/FM demodulation.
Nominal mode
In this mode, the MS-FM demodulator uses the theoretical value 0.7. This mode is suitable for numerically
modulated PCM/FM signal. For analog FM modulator, this mode is not recommended.
Manual mode
Selecting this mode, the user can define the modulation index in the Index Value field. This mode is only
recommended for digital modulator with a known modulation index.
Automatic Mode
Selecting this mode, the demodulator analyses the received signal and estimates the modulation index.
This mode is recommended when using an analog modulator.
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