High-Precision Measurement of Sine and Pulse Reference Signals Using Software-Defined Radio

This paper addresses simultaneous high-precision measurement and analysis of generic reference signals by using inexpensive commercial off-the-shelf software-defined radio hardware. Sine reference signals are digitally downconverted to baseband for the analysis of phase deviations. Hereby, we compare the precision of the fixed-point hardware digital signal processing chain with a custom single instruction multiple data x86 floating-point implementation. Pulse reference signals are analyzed by a software trigger that precisely locates the time where the slope passes a certain threshold. The measurement system is implemented and verified using the Universal Software Radio Peripheral (USRP) N210 by Ettus Research LLC. Applying standard 10 MHz and 1 PPS reference signals for testing, a measurement precision (standard deviation) of 0.36 and 16.6 ps is obtained, respectively. In connection with standard PC hardware, the system allows long-term acquisition and storage of measurement data over several weeks. A comparison is given to the dual-mixer time difference and time interval counter, which are state-of-the-art measurement methods for sine and pulse signal analysis, respectively. Furthermore, we show that our proposed USRP-based approach outperforms measurements with a high-grade digital sampling oscilloscope.

[1]  G. Brida,et al.  Comparison of high-precision frequency-stability measurement systems , 2003, IEEE International Frequency Control Symposium and PDA Exhibition Jointly with the 17th European Frequency and Time Forum, 2003. Proceedings of the 2003.

[2]  Masaharu Uchino,et al.  Frequency-Stability Measurement System Using High-Speed ADCs and Digital Signal Processing , 2007, IEEE Transactions on Instrumentation and Measurement.

[3]  Nuno Borges Carvalho,et al.  Designing and Testing Software-Defined Radios , 2010, IEEE Microwave Magazine.

[4]  Robert Jördens,et al.  Oscillator metrology with software defined radio. , 2016, The Review of scientific instruments.

[5]  F. L. Walls,et al.  Characterization of frequency stability in precision frequency sources , 1991, Proc. IEEE.

[6]  Marco Siccardi,et al.  Delay measurements of PPS signals in timing systems , 2016, 2016 IEEE International Frequency Control Symposium (IFCS).

[7]  A. Savitzky,et al.  Smoothing and Differentiation of Data by Simplified Least Squares Procedures. , 1964 .

[8]  Alexander Ihlow,et al.  Using software defined radios for baseband phase measurement and frequency standard calibration , 2017, 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC).

[9]  D. W. Allan,et al.  Picosecond Time Difference Measurement System , 1975 .

[10]  Dominik Sondej,et al.  Subpicosecond-resolution time-to-digital converter with multi-edge coding in independent coding lines , 2014, 2014 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings.

[11]  Józef Kalisz,et al.  Review of methods for time interval measurements with picosecond resolution , 2004 .

[12]  Pawel Kwiatkowski,et al.  Modular time interval counter , 2014, 2014 European Frequency and Time Forum (EFTF).

[13]  E. Hogenauer,et al.  An economical class of digital filters for decimation and interpolation , 1981 .

[14]  Larry Doolittle.  Filtering and Decimation by Eight in an FPGA for SDR and Other Applications , 2010 .

[15]  Pawel Kwiatkowski,et al.  An Eight-Channel 4.5-ps Precision Timestamps-Based Time Interval Counter in FPGA Chip , 2016, IEEE Transactions on Instrumentation and Measurement.

[16]  Jack E. Volder.  The CORDIC Trigonometric Computing Technique , 1959, IRE Trans. Electron. Comput..