Research On The Frequency Measurement System Of Phase Detection Broadband Based On FPGA

The market demand of electronic measurement system is pretty big, especially with the tremendous strides in communication and television market, the electronic measurement market increased rapidly. Recently, the electronic measurement apparatus becoming digitalized and intelligentized, the manufacturers making more digitalized products and rapid development in certain types, which have big demand both in domestic and foreign market.The frequency measurement is the fundamental one in electronic measurement field. As the traditional method - count value is adopted in measuring frequency and cycle time,±1 error cannot be voided in measuring the signal, therefore, pretty big defect exists in actual electronic measurement system, and the result is not accurate. The equal precision measurement, which is established on the basis of direct measurement, is not only precise, but also synchronizes with standard frequency signal, as well as starts the broadband measurement. Although the equal precision measurement eliminates the±1 error that exists in traditional frequency and cycle time measurement, inherent error exists in it– error caused by desynchronization with standard frequency signal.The system introduced in this article–phase detection broadband measurement is based on FPGA. The advantage of it is FPGA, which not only speeds up the system, but also increases the stability and integrity. In addition, the±1 error is eliminated, the desynchronization is improved, and the range of equal-precision measurement is enlarged to 1 Hz~2.4GHz, and the precision in 1s gate lock reaches 0-1 level.phase detection broadband system here is the time-frequency measurement, which is summarized from the phase difference variation rules of any two stable-cycled frequency within their minal common multiple. phase detection broadband system mainly researches the phase coincident point rules of any two stable-cycled frequency, the coincidence does not mean accurate one, which has mere error. Gate time is set in phase coincident point, the phase time can be caught to eliminate the±1 count error in the past. Additionally, FPGA is added in this system, which make the system more highly-integrated, digitalized, stable and lower noised, and the most important one is the measurement precision is increased by a thousand times and starts a new age of frequency measurement.FPGA and VHDL are introduced in this article. The whole system is introduced in two parts: one is design of hardware circuit, the other is to imitate the whole circuit with MAX + PLUSII.In designing the hardware circuit, signal F0 comes out of Schmitt trigger, which is formed by standard frequency signal f0 through circuit 555, and input into FLEX 10K. Signal Fx formed by fx (the detected signal lower than standard frequency one), which comes out of Schmitt trigger through circuit 555 and bilaterial switch 74LS153, enters into FLEX 10K. Signal fxgao, which is higher than standard frequency one, goes through mb506 high frequency division and bilaterial switch 74LS153, signal Fx inputs into FLEX 10K. In FLEX 10K, the standard frequency f0 and detected signal fx produce phase coincidence through the same phase's inspection. The preset gate signal and same phase point, which come out of singlechip AT89C2051, go through D trigger module in FLEX 10K, and control the counting of f0 and fx. N0 and Ns are transmitted to AT89C2051 for processing and calculation, finally the frequency measurement is displayed on LED.The design of main program is the basis in software imitation, subprogram is the second, as well as the imitation of whole circuit and checking of its functions. The meaning of the system in practice:i. The system reveals the relationship of quantized phase shift resolution of bi-frequency signal and the frequency value of max common factor and couple signals, which has great practical value in theory and practice of precision frequcncy measurement and precision measurement and research of cycle movement.ii. High precision measurement of medium and high broad-frequency with the theory of max common factor frequency and phase checking, is of high precision in result and simple equipment requirement, which is a brand new technology that worthy of spreading. Not only can it replace many professional measurement apparatus, but also develops lots of multi-functional apparatus for measuring frequency and cycle signals.iii. It has many advantages to combine the broadband phase-frequency with computer technology, not only in wider range and high precision, but also has better cost performance.The precision in measuring frequency punctuation with this new technology can be higher, which is good to resolve the comparation of some non-standard frequency source. It can also be used as high-precision cymometer, or to replace some single-purpose frequency adjustment apparatus. Not only can it be used in national defense, production and daily life, but also has pretty good expection in development.