للكاتبين :

Nasser H-Ali , Ashor _Alsellami

Computer Engineering Department-Faculty of Eng -.Al-fateh University


In the past few years high-speed data transmission over dialed telephone connection or over

leased lines has growth rapidly.

In this paper a versatile, high speed structure modem was designed .It permits the implementation

of several modulation formats with various speed options from the common TMS320C25 single

chip microprocessor which is controlled by a stored algorithms.

The TMS32C25 on-chip microprocessor can be programmed to produce either a phase or

frequency modulated synchronous signal and to demodulate it.

Using such a single chip signal processor as a basic building block, a low cost, high-speed

modem can be programmed to operate over unconditional lines.

The implemented modem operates at 1200 symbol/sec, with two bits per symbol (2400pbs using

DQPSK or with three bits per symbol (4800 pbs) using 8DPSK,and finally four bits per symbol

(9600 pbs) using D-16QAM with externally carrier recovery.

A series of processing cycle tactics was used to allow the microprocessor like TMS320C25 or

other DSP processors to handle all modem functions in real time. The microprocessor-based

modem is extremely flexible because its software controlled nature, and through programming it

will provide a Varity of additional functions. The system was tested in the case of perfect and

distorted channel.

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