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 down-converted 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 (SIMD) 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 ps 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 (DMTD) and Time Interval Counter (TIC), 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.

We devise a novel phase and time error measurement technique for 10 MHz and 1 PPS reference signals, based on Software Defined Radios (SDR) and Digital Signal Processing (DSP). The proposed measurement setup allows us to employ two synchronized type N210 Universal Software Radio Peripheral (USRP) devices with LFRX daughterboards to realize an economically priced and easy-to-use quad-channel measurement setup. Our real-time C++ DSP software is based on the USRP Hardware Driver and enables flexible long-term measurements with verified sub-nanosecond precision. We demonstrate our intended use case, the calibration of two off-the-shelf rubidium standards (SRS FS725) against each other, using their RS 232 interface. By means of two 120 hour long-term measurements with a power cycle and cold start in between, we verify it is possible to reproducibly maintain a relative drift of ±5 parts-per-trillion, which is an order of magnitude better than specified by the FS725 data sheet. Additionally, we investigate the influence of the ambient temperature on short-term stability

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In this paper, practical investigations of level accuracy and uncertainties using a Rohde & Schwarz signal generator (R&S SMB-B140) and spectrum analyzer (R&S FSV40) are performed up to 30GHz. We show that it is possible to measure frequency responses of DUTs with uncertainties below ±0.05dB up to 30 GHz instead of ±0.5...1.5dB using auto settings, standard setup, or relying on datasheets. The level linearity of instruments with integrated step attenuators is shown to be improved to ±0.03dB instead of ±0.3...1dB by using a special “hybrid” procedure. Furthermore, it is shown how computer aided measurements procedures should be programmed with these instruments to attain low deviations between measurements