Paradyne DMD15 Front Panel Interface, Clock, Watchdog Timer, Program Flash ROM, 8 RAM, Modulator

Operation DMD15/DMD15L IBS/IDR Satellite Modem

3.9.4 Front Panel Interface

The M&C operates the Front Panel, which includes a 2 x 12 backlit LCD, Indicator LEDs, and a Numeric Keypad.

3.9.5 Clock

The time and date is kept in order to ‘time-tag’ system events.

3.9.6 Watchdog Timer

The Watchdog Timer monitors the health of the M&C Subsystem.

3.9.7 Program Flash ROM

The 512K of reprogrammable program ROM (expandable to 1 MB) is available to the M&C.

3.9.8 RAM

128K RAM (expandable to 512K)

3.9.9 Non-Volatile RAM

8K of Non-Volatile RAM (expandable to 32K) is provided in order to hold the modems current configuration. In the case of power interruption, the M&C will reconfigure the modem identically to the state before power was lost.

3.10 Universal Modem

The Universal Modem (UM) Card contains a complete variable rate modulator/demodulator intended for satellite communications. The UM utilizes the latest digital technology for high reliability and versatility. The modulator and demodulator sections may be configured independently under processor control. The UM includes a duaL-Band 70/140 MHz IF, QAM Modulator/Phase Lock Receiver, Convolutional Encoder/Viterbi Decoder, sequential decoding option, Differential Encoder/Decoder, and a V.35 Scrambler/Descrambler.

3.10.1 Modulator

Processed baseband data ready for transmission enters the modulator and undergoes, if the functions have been enabled, V.35 Scrambling and Differential Encoding. The data then undergoes convolutional encoding and is fed to the Dual Variable Interpolating FIR Filter. The FIR Filter shapes the data waveform to a predefined spectral mask and vectorizes the data for mapping into a PSK Constellation. The data is then converted to an analog waveform and is vector modulated onto an RF Carrier produced from the Transmit IF Synthesizer Circuitry. The final output is then fed to the IF Loopback Circuitry where under microprocessor control the Transmit Signal may be routed to the demodulator. Due to its nearly complete digital implementation, the modulator is capable of performing virtually any modulation format, and can produce almost any desired spectral mask. The modulator also houses the SCT and Reference Oscillators. The Reference Oscillator provides the frequency standard for both the modulator and demodulator. An external reference may also be selected. In this case, the Reference Oscillator is locked to the external reference.

3-10 TM051 – Rev. 5.8