Rockwell RFX144V24-S23, Руководство дизайнера

Страница: 13 / 198

RFX144V24-S23 and RFX96V24-S23 Modem Designer’s Guide
1070 1-5
1.3 TECHNICAL SPECIFICATIONS
Configurations, Signaling Rates and Data Rates
The selectable modem configurations, along with the corresponding signaling (baud) rates and data rates, are listed in Table
1-2.
Tone Generation
The modem can generate voice-band single or dual tones from 0 Hz to 4800 Hz with a resolution of 0.15 Hz and an
accuracy of 0.01%. Tones over 3400 Hz are attenuated. Dual tone generation allows the modem to operate as a
programmable DTMF dialer.
Data Encoding
The data encoding conforms to ITU-T recommendations V.17 (RFX144 models), V.33 (RFX144 models), V.29, V.27 ter,
V.21 Channel 2, V.23 (-23 Option) and V.23 receive.
Automatic Adaptive Equalizer
An adaptive equalizer in V.17 (RFX144 models), V.33 (RFX144 models), V.29 and V.27 ter modes compensates for
transmission line amplitude and group delay distortion.
Fixed Digital Cable Compromise Equalizer
Compromise equalization can improve performance when operating over low quality lines. The modem has a selectable
fixed digital compromise cable equalizer in the high speed receive and transmit data paths.
The modem includes an optional host programmable Receive Compromise Equalizer for V.23 1200 bps reception and Caller
ID mode (-23 Option).
Transmitted Data Spectrum
The transmitted data spectrum is shaped in the baseband by an excess bandwidth finite impulse response filter (FIR) with
the following characteristics:
When operating at 2400 baud, the transmitted spectrum is shaped by a square root of 20% raised cosine filter.
When operating at 1600 baud, the transmitted spectrum is shaped by a square root of 50% raised cosine filter.
When operating at 1200 baud, the transmitted spectrum is shaped by a square root of 90% raised cosine filter.
The out-of-band transmitter energy levels in the 4 kHz - 50 kHz frequency range are below -55.0 dBm.
Turn-on Sequence
Transmitter turn-on sequence times are shown Table 1-3.
Turn-off Sequence
Transmitter turn-off sequence times are shown in Table 1-4.
Transmit Level
The transmitter output (TXA) level is programmable in the DSP RAM from 0 dBm to -15.0 dBm. The modem adjusts the
output level by digitally scaling the output to the transmitter's digital-to-analog converter.
Scrambler/Descrambler
The modem incorporates a self-synchronizing scrambler/descrambler in accordance with V.17 (RFX144 models), V.33
(RFX144 models), V.29, or V.27 ter recommendations, depending on the selected configuration.