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Rack-Mount RDMS
TM
Telemetry Receiver
98
Quasonix, Inc.
4.2.3.1.2.9.1 Encoding Menu
The Encoding dropdown menu, available in PCM/FM mode, is used to set the non-return to zero (NRZ) value used
by the receiver. NRZ is a way of encoding binary data on a physical signal. The options are:
•
NRZ-L – Non-return to zero Level
•
NRZ-M – Non-return to zero Mark (1)
•
NRZ-S – Non-return to zero Space
Figure 172: Additional Advanced Settings, Encoding Menu Highlighted, PCM/FM Mode Only
Bi-Phase encoding (box checked) enables the demodulator to process Bi-Phase encoded data (as opposed to NRZ
encoded data) per IRIG 106 Chapter 4.
The Spectrum Inversion option inverts the frequencies (box checked) processed by the demodulator relative to how
they appear at the IF Output port. That is, low frequencies within the IF Filter bandwidth become high frequencies
within the demodulator and vice versa. This can be used to compensate for a frequency inversion elsewhere in the
system.
4.2.3.1.2.9.2 Convolutional Decoder
Convolutional Decoder (box checked) enables the Viterbi decoder.
The Convolutional Decoder (also commonly referred to as the Viterbi Decoder) is available in PCM/FM and legacy
PSK modes. Its purpose is to decode data that has been encoded per “Consultative Committee for Space Data
Systems, Recommendation for Space Data System Standards, TM Synchronization and Channel Coding, CCSDS
131.0-B-1, Blue Book,” September 2003, Section 3.
Convolutional encoding adds redundant information to the transmitted data stream. The Convolutional Decoder uses
this information to detect and correct bit errors that may occur, particularly due to predominantly Gaussian noise.
The encoded data rate is twice the specified data rate, and the occupied bandwidth is also doubled.
For legacy PSK modes that use quadrature modulation (e.g., OQPSK), there are actually two independent decoders,
one for in-phase (“I”) data and one for quadrature (“Q”) data. This approach assumes a similar arrangement for the
encoders in the transmitter, which is true of all Quasonix transmitters.
4.2.3.1.2.9.3 Downconvert Antenna
The DC Antenna option (box checked) is only available when using the 5-band downconverter AND P and C band
are enabled.
•
When the downconverting antenna is not available, this command displays only an assumed value.
•
The downconverting antenna setting only applies to C band frequencies.