Principles of construction and structural and circuit designs of direct digital synthesizers based on the method of direct digital frequency and signal synthesis are described. The block and circuit diagrams of the direct digital synthesizer of compound wideband signals are presented. This synthesizer is used to synthe size signals with the amplitude, frequency, and phase modulation in a frequency range from 0.001 to 200 MHz.

No abstract

Modern systems of radio engineering systems are very widely used in radar and radio communications. An important component of the work of radio systems is the creation of diagnostic equipment with high resolution, noise immunity, improved security and reliability, which become more accessible with the advent of digital computer frequency synthesizers. Digital computer synthesizers using the direct digital signal synthesis method are the main nodes of modern diagnostic equipment for radar and radio communication systems. The article considers a number of advantages of digital computing synthesizers, which include a wide range of synthesized frequencies, an extremely small step of the frequency grid, extremely fast frequency tuning speed, phase continuity during frequency tuning, low phase noise, a simple algorithm for generating complex signals, the possibility of independent amplitude control, phase and frequency of the synthesized signal. The principles of construction and structural and circuitry solutions of digital computational synthesizers based on the method of direct digital synthesis of frequencies and signals are given. The principle of constructing structures of digital multiphase signal synthesizers is proposed, in which the initial phases of the synthesized signals can be set in software. Structural diagrams of digital computational synthesizers based on digital code storage devices and with an M-shaped law of frequency variation which allow synthesizing signals with amplitude, frequency and phase modulation in the frequency range from 0.001 to 400 MHz are presented.

In radar detection and radio navigation ensuring the reception of signals transmitted over the meteor channel of radio communication is often controversial[1-3]. Solving these problems requires the ability to synthesize precision signals directly[4, 5] for heterodyning systems in addition to modern analog-to-digital conversion devices, correlation analysis, and statistical processing of signal-noise complex. The step of adapting four channel receivers to dynamically changing conditions of transmitting information may include determining the composition of the signal-noise mixture, determining the phase characteristics of the communication channel, estimating the channel transmission rate, and obtaining QoS information. In addition, adaptation often implies the use of a logical channel control loop, which entails the need for complex feedback procedures. Software-defined radio systems are radio and telecommunication systems that can be tuned to an arbitrary frequency band and receive various types of modulated signal, consisting of programmable equipment with program control. SDR performs a significant part of digital signal processing on a conventional personal computer, signal processor or FPGA. In such systems and complexes, the parameters are changed by software configuration. The article considers the implementation of DDS for heterodyning an intermediate frequency signal on the FPGA basis for four channel receiver 1288хк1т (mf-01), which allows you to work with both narrow-band and wide-band communication channels (with simultaneous operation of 4 channels, the band can be expanded) and can be used in modern telecommunication communication systems.