Development of a digital HF modem using simulation for design development and proving

Describes a technique undertaken on the strategic adaptive modem (SAM) project using a digital signal processing (DSP) design tool called the signal processing workstation (SPW). The strategic adaptive modem is a general purpose hardware platform for operating modem waveforms. The user selects the required waveform at modem initialisation time. The SAM currently operates two modulation schemes; STANAG 4285 and STANAG 4202. Both schemes were developed using the SPW. STANAG 4285 is a NATO standard waveform for digital HF modems. When the draft STANAG was generated NATO was looking to industry to produce candidate modems that could be trialled to evaluate the performance of the proposed standard. The SPW was selected for the DSP system design as it supports the design and simulation of the whole DSP development. Using standard SPW libraries, design prototyping can be easily carried out allowing early simulation of functional design. The transmission environment that the modem will be operating under can also be described in the SPW providing comprehensive simulation within a single environment. Being able to simulate the transmission environment along with the whole DSP´s operation, enables confidence in the modem´s performance to be assessed before formal trials. This can be carried out in conjunction with bench testing, allowing events observed during testing to be repeated in the simulation environment and isolated for analysis and correction. An enhancement that Siemens Plessey Systems have added to the SPW takes the simulation code and compiles it with the target specific libraries to run on the target processor