DDS

Features

A complete cycle of function waveform is stored in the memory look-up table shown above. The phase accumulator tracks the current phase of the output function. To output a very low frequency, the difference phase (Δ) between sampled samples will be very small. For example, a very slow sine wave might have a delta phase of 1 degree. Then the sample No. 0 of the waveform acquires the amplitude of the sine wave at time 0, and the sample No. 1 of the waveform acquires the amplitude of the sine wave at time 1 and so on. After 360 samplings, all 360 degrees of the sine curve, or exactly one cycle, will be output. A faster sine wave may have a delta phase of 10 degrees. Thus, 36 samples will output one cycle of the sine wave. If the sampling rate is kept constant, the slower sine wave will be 10 times slower than the faster sine wave. Furthermore, a constant delta phase will inevitably result in a constant sine wave frequency output. However, DDS technology allows the delta phase of the signal to be changed quickly through a frequency table. The function generator can specify a frequency table, which includes segments composed of waveform frequency and duration information. The function generator generates each defined frequency band in sequence. By generating a frequency table, complex frequency sweep signals and frequency hopping signals can be constructed. DDS allows the phase of the function generator to change continuously from one stage to another. Vector signal generators provide highly flexible and powerful solutions that can be used in scientific research, communications, consumer electronics, aerospace/defense, semiconductor testing, and some emerging fields such as software radio, radio frequency identification (RFID), and wireless sensing Network etc. Some companies also provide many other analog output products that use DACs to generate analog signals. The basic structure of the analog output board is to connect a small FIFO memory to a DAC. Most analog output boards are used to generate static voltages, and many can be used to generate low-frequency waveforms.