Design of a synchronous FFHSS modulator on a FPGA with system generator

Abstract

This work is based on a previous Fast Frequency Hopping Spread Spectrum (FFHSS) transceiver designed for wireless optical communications. The core of the transmitter was a discrete Direct Digital Synthesizer (DDS). In the first prototype the DDS control and the digital synchronization signal were generated using a Programmable Logic Device (PLD), besides a discrete external filter was necessary to eliminate high frequency components of digital synchronization signal and generate analog synchronization signal. The FFHSS and analog synchronization signals were emitted by two separated Light Emitting Diodes (LED) to avoid adding them with discrete analog circuits. The peak emission wavelength of the LED was 650 nanometers. The objective of this work is redesign the modulator on a Field Programmable Gate Array (FPGA) using System Generator from Xilinx and analyse the performances of this design methodology. System Generator is one design tool in Simulink of Matlab. It allows fast design of digital systems using block diagrams. The compilation generates the files necessary for the Integrated System Environment (ISE) for FPGA of Xilinx, where the description of the circuit is obtained in a standard hardware description language. In ISE it is possible to compile the hardware description language files, simulate the system, assign pins, obtain the program file and program the FPGA.