Design And Study Of Complete Synchronous Digital Cymometer Based On VHDL Language

Frequency signals have strong anti-interference ability, so they are easy to transport. Compared with other signals, the measurement of frequency signals can obtain higher measuring accuracy. Therefore, frequency is a basic and very important parameter in the electrical measurement field. Frequency measurement also becomes a most important measurement. With the development of the electronic measurement technology, more and more high frequency or uhf(ultrahigh frequency) signal devices are widely applied in production and everyday life, the previous cymometer already can't satisfy the measurement demand, this circumstance requires us to study frequency measurement methods with higher accuracy, faster speed.The development of the EDA technology and the extensive application of programmable logic devices such as FPGA makes the designer to realize and reconfigure the hardware function just by Hardware Description Language and EDA software, which makes the hardware design as convenient as software programming. It has changed not only the traditional electrical design methods, but also the cymometer's traditional design methods.This paper expounds the principles and errors of some commonly used frequency measurement methods. The multi-period synchronous frequency measurement method has eliminated the positive and negative 1 number-counting error of the measured signal, because its measured signal and the real gate signal is synchronous. However, the positive and negative 1 number-counting error of the standard signal still exists. The complete synchronous digital frequency measurement method has thoroughly eliminated the positive and negative 1 number-counting error, because it has realized the synchronization of the measured signal, standard signal and the real gate signal. The realization method of the complete synchronization is:the real gate singal is controlled by the detected phase synchronous pulse of the measured signal and standard signal, when the phase is synchronous, the counters start counting, when the phase is synchronous again, the counters stop working. This cymometer is designed by the complete synchronous digital frequency measurement method based on the programmable logic devices FPGA. First the overall design plan is given according to the block diagram. And then in accordance with the top-down design method, the frequency measuring part is divided into a number of modules by their different functions. The detailed design methods and the simulation in Quartus II of each module are also given. In order to make the cymometer into a complete frequency measurement system, this paper also carries out the hardware design of some auxiliary modules, such as the standard frequency signal generating module and the measured signal reshaping module.In the end, this paper also puts forward the scheme of the complete synchronous digital cymometer based on the SOPC, and introduces the system hardware and software design thought briefly. The cymometer design has important theoretical significance and practical application value, which adopts VHDL language programming, with the FPGA for hardware design carrier and the integrated development tool based on the SOPC.