The Design And Realization Of The IRIG-B Code Decoding Circuit Board

During the measurement and control process of the missiles' targeting and the aeronautic structures' experimental tasks in the range, the measurement and control equipment in all test fields needs to be unified at the same time standard in order to better analyze and verify the performances and testing data of the tested equipment. So the concept of the time uniform system is been put forward. It refers to the whole set of precise electronic instrument system which provides synchronous time standard for the range experiments.In the use and development process of the time uniform equipment, IRIG-B standard time format code is internationally taken as the code source signal of the transmission of the time information. After modulation, the AC code, which is alternating code for short, can transmit the information for a long distance so this design mainly takes the AC code as the research object and designs a set of time uniform system decoding card that can stably decode the AC code.This thesis introduces the coding method and characteristics of the IRIG-B code concretely. According to the coding format of the IRIG-B code,a method using orthogonal related detection is put forward to detect the synchronous signal in the beginning of the frame after detailed analysis and demonstration. Besides, as for the decoding of the time code, a method using the fault tolerant technique to improve the correct rate of decoding is taken to realize the decoding of the AC code. This design selects TMS320VC5409 DSP manufactured by TI Company as the core decoding device, EPM9320LC84 CPLD manufactured by ALTERA Company as the auxiliary device to realize a kind of IRIG-B code decoding circuit.Compared with the circuit realizing the function by microcontroller assisted by a large number of external circuits, this circuit structure is simple and easy to be modified. The time information decoded is transported to the host computer by ISA bus to realize the display of the time information. The decoding scheme is found mainly by theory verification. The decoding circuit board is designed and the software programmed to decode the time information. Finally,the decoding circuit board is commissioned and the data tested.In the end, plug the card into the card slot and the data is sent to the host computer by ISA bus. The program running on the host computer can stably and reliably receive the data and show the stable running of time by the designed software interface, which verifies the reliability of the IRIG-B code decoding circuit board and the correctness of the software program. It is proved that the decoding card can get the time information real-timely and meet the technical indexes. This decoding card has been applied in a kind of monitoring and controlling time system equipment. It is showed by the experimental process that the card can run effectively and stably.