Design Of High-Resolution Frequency Measurement Module Based On Analog Interpolation

As one of the most important physical quantities in scientific research and engineering applications,frequency is widely used in many fields such as electronic communication,aerospace,measurement,space exploration,navigation and positioning.Therefore,high-precision and high-resolution frequency measurement has gradually become an important part of electronic measurement systems.As the increasingly widespread application of signal frequency measurement in modern electronic systems,the requirements for measurement accuracy,resolution,frequency range,and other indicators of frequency measurement systems are also increasingly high.Focusing on the above topic,this article conducts an in-depth analysis of frequency measurement methods and resolution improvement theory.Frequency measurement methods based on multi period synchronous measurement method and analog interpolation method are selected,and a new measurement gate generation method and data processing algorithm are proposed on this basis.Then completed frequency measurement module design in the frequency range of 100m Hz～300MHz,measurement resolution of 12 digits/second and measurement time of 1ms～1000s.The main work is as follows:1.Research on high-resolution frequency measurement technology.Aiming at the quantization error problem of traditional digital counting measurement method,the measurement resolution improvement method based on multi-period synchronous measurement method and analog interpolation method is studied.The synchronization error between the pre-gate and the actual gate in the multi-period synchronous measurement method for measuring the gate design mode.The combined effect of this error and the quantization error in the counting process will complicate the change of the odd time,which is not conducive to analyzing its change information.When it is designed as a continuous gate measurement,the change analysis of the odd time is simplified,then the relationship between the odd time and the input signal frequency is easily obtained.By analyzing the relationship between the phase of adjacent measurement gate odd time and the measured signal,the measurement results can be compensated and the measurement resolution can be improved.2.The design and implementation of hardware circuit and logic of module.By analyzing the requirements of module measurement index,the hardware scheme based on"conditioning channels+comparison converter+measurement controller+analog interpolator"is determined,and the design of signal input channel,signal conversion circuit,FPGA circuit,analog interpolation circuit,clock circuit and power circuit is completed.Then,based on the research of measurement methods,the logic design of channel function switching control,measurement gate generation and counting,odd time generation and processing,and upper computer communication has been completed.During the process of gate generation,gate parameters are calculated by preset measurement time,and based on these gate parameters,continuous non waiting time gates and synchronous counting gates are generated respectively;During the capacitor charging process,the odd time calibration under different conditions is achieved by increasing the reference pulse along the circuit,reducing the temperature drift caused by the environment during the working process of the simulator device;During the interpolation sampling process,the measured odd time and reference pulse are output to the charging capacitor,and the ADC is controlled to obtain the capacitor sampling voltage,achieving analog interpolation measurement of odd time and ultimately improving the resolution of frequency measurement results.After testing and verification,the measurement resolution of the high-precision frequency measurement module designed in this paper reaches 12 digits per 1 second,and the measurement uncertainty within 1 s measurement time is less than 2.5×10^-11,can realize the signal measurement of multiple waveforms in a large dynamic range,besides the frequency measurement range and measurement time can meet the predetermined indicators.