Design of direct digital synthesizers signal generator

Abstract

— An integral element of most radio devices is systems of frequency and signal synthesis. Most of the known circuits use analog elements, which are characterized by the change of parameters under the influence of external factors. However, with the development of digital technology that uses only mathematical calculations and logical functions resistant to changes in external factors, a new method of generating signals was developed, which is called a direct digital synthesis. One of the main types of frequency synthesizers are direct digital synthesizers (DDS). High frequency and phase resolution, the fastest possible transition to another frequency without phase discontinuity, the ability to control the frequency, phase and amplitude through the digital interface are constantly expanding the DDS implementation area in various fields of technology, such as satellite communication, radar-location, radio navigation, measuring equipment, etc. A direct digital synthesis is a method of generating a signal of the desired frequency and waveform using digital resources. Owing to the digital solution, the generated signal has the accuracy inherent in digital systems. The frequency, amplitude and phase of the signal at any given time are known and controlled. With these advantages, direct digital synthesis is increasingly replacing analog solutions. The relevance of the study stems from the lack of domestic equivalents of frequency synthesizer chips, the implementation on the modern element base. The article describes a method for designing a direct digital synthesizer (DDS) with a quarter-wave transformer (QWT) based on FPGA.