Practical Signal Design Based On The DDS Technology

In:electronic measurement, communications, television broadcasting, radar, remote telemetry and so on many areas, the frequency signal is needed which meet the quality requirements in a certain frequency range. Frequency signal is generated by frequency synthesizer technology to achieve. The circuit system to achieve frequency synthesizer is called the frequency synthesizer. Frequency synthesizer occupies an extraordinary position in a modern electronic system. In the test equipment frequency synthesizer is taken as a standard signal source, it is referred to as the "heart" of many electronic systems, with the rapid development of modern electronic technology, the increasingly high demands are made on the signal frequency accuracy and frequency stability. Frequency synthesizer technology has gone through three generations, of which the first second-generation frequency synthesis technique that Direct analog frequency synthesizer and Indirect frequency synthesis has been difficult to meet the requirements of modern electronic technology to the frequency source.The generation and development of direct digital frequency synthesis (Referred to as DDS) gives an effective solution on the subject and has been rapidly applied.The paper summarize the implementation mechanism, advantages and disadvantages of the three methods. The paper’s focuses is on the working principle of direct digital frequency synthesis and it’s current development status and future development trend.The main work of this paper are:the use of direct digital frequency synthesizer chip AD9851and MCU control and flexible features, and developed a function waveform generator, sinusoidal signal generation. However some attenuation of the amplitude of the DDS chip AD9851output signal with load, and the output frequency is higher performance is particularly significant, it is difficult to meet the actual signal a higher magnitude and stability of demand, this paper is designed an automatic gain amplification circuit and power amplifier circuit on the DDS basis so that the output signal amplitude basically stable at6V±1V, also can achieve a variety of modulation functions.The design of the signal source is given on the basis of theoretical studies, as well as hardware and software to achieve. The hardware circuit of the whole system is divided into single-chip control and interface circuit, the AD9851chip, after stage amplifier, AM, FSK, the ASK and other various modulation module, each hardware module schematic is given and analyzed. The software part is written in C to achieve dynamic menu, keyboard scanning, LCD, frequency base conversion, the AD9851interface call, ASK, FSK modulation. The experimental data indicate that the design of this article based on DDS technology sinusoidal signal source to meet expectations.