title: Note: Precise phase and frequency comparator based on direct phase-time measurements.
abstract: We are reporting on the design, performance, and application results of a phase and frequency comparator based on the direct phase-time measurement using a high performance event timer. The advantages of this approach are the simple implementation, a broad frequency range, and the clear interpretation of the measured results. Primarily we analyzed the background instability of the instrument in a common-clock test when a 200 MHz clock signal was connected to both inputs and the noise bandwidth was kept at 5 Hz by a preprocessing of the measured data. The results show that the Allan deviation of the background instability follows 4 × 10(-14)/τ for a wide range of averaging intervals from 0.1 s up to 10(4) s. These results are better than background instability of commercially available state-of-the-art instruments based on the phase difference multiplication. Finally the instrument was used for comparison of two H-masers. This experiment proofed that one of possible applications is a comparison of low-noise highly stable frequency sources and measurement of their frequency stability in the time-domain. The noise background of the instrument was negligible for averaging intervals longer than 100 ms.
authors.affiliation: Czech Technical University in Prague, Brehova 7, 115 19 Prague, Czech Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Prochazka
authors.affiliation: Institute of Photonics and Electronics, Academy of Sciences of the Czech Republic, 182 51, Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Panek
authors.affiliation: Czech Technical University in Prague, Brehova 7, 115 19 Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Kodet