The multipurpose software modem provides reliable communications at rates up to 19,200 Kbps over an HF radio circuit. This modem serves as a test bed for selection of optimum communication parameters over specific HF channels. The modem allows easy real-time adaptation of bit-rate, frame size, modulation, coding, and interleaving.

The modem uses a Data Directed Equalizer (DDE), Decision Feedback Equalizers, and a novel Nonlinear Data Directed Equalizer for superior performance. The nonlinear equalizer neutralizes intersymbol interference.

The modem is fully compliant with the mandatory waveform and performance requirements of MILSTD-188-110A. Convolutional coding, interleaving, and Viterbi soft decision decoding further enhance its performance.

Software controls the modem completely. It operates with Analog Devices AD-2106X series SHARC DSP. This allows it to grow upward, operate at low voltage, and interface with other military systems. It provides large reserve capacity for customized applications, such as modulation recognition, feature extraction, and tracking. This modem also allows programmable FSK operation and can be used as a parallel tone modem.

An extremely easy Graphical User Interface (GUI) gives the user control over the modem functions. The modem is entirely PC-based and the GUI is fully compliant with Windows® 95 and NT. Although the modem is PC-based, the user can configure other form factors such as VME.

The software modem’s completely digital implementation allows the user to customize it based on applications

Long-range point-to-point communications Surface wave communication Naval broadcast Ship-to-shore Radio channels Networking Aviation communication Secure digital facsimile Narrow band secure voice Digital video image transmission (DVTTS)