An ultra-high ramp rate arbitrary waveform generator for communication and radar applications

Abstract

Currently, the frequency ramp rate of most commercial direct digital synthesizer (DDS) chips is not more than several hundred MHz. In some communication or radar applications, the frequency ramp rate must reach several GHz. In order to greatly increase the frequency ramp rate, this paper proposes a full-custom multi-core & single-channel DDS (MCSC-DDS). This MCSC-DDS consists of some DDS sub-cores which are implemented in a field programmable gate array (FPGA) and a high speed digital analog converter (DAC) whose sampling frequency achieves several GHz. In FPGA, these DDS sub-cores operate in parallel to equivalent achieve ultra-high frequency ramp rate which is equal to the sampling frequency of the DAC. As an example, a compact and portable MCSC-DDS whose frequency ramp rate achieves 2.5 GHz is presented. It is mainly made up of a Virtex-5 FPGA and an AD9739. The measured chirp waveform has a maximum 2.5 GHz frequency ramp rate which demonstrates the efficiency of the MCSC-DDS.