Cross-Spectral Phase Noise Is Measured On Terahertz Source

With traditional phase-measurement systems generally unable to perform beyond 125 GHz and spectrally pure sources increasing in frequency, the race is on to conquer phase-noise testing of terahertz sources.
April 9, 2013
2 min read

To ensure the characterization of phase noise for applications that will integrate terahertz components into usable products, many are developing terahertz phase-noise measurement capabilities. The National Institute of Standards and Technology (NIST), for example, is working on phase-noise measurement systems that support 670 GHz, 850 GHz, and 1.05 THz. Recently, the first cross-spectral phase-noise measurement of a spectrally clean terahertz source was presented by NIST’s J.A. DeSalvo, A. Hati, C. Nelson, and D.A. Howe.

Their approach is to combine even-harmonic mixers with a 2.5-GHz frequency comb. The result is a phase-noise measurement system in waveguide (WR1.5), which is achieved by use of cross-spectral and digital phase-noise measurement techniques. At 670 GHz, an upper bound of this system’s noise floor is -20, -40, and -60 dBc/Hz at 1-, 100-, and 10,0000-Hz offsets, respectively. The team also measured a commercial, low-phase-noise, 670-GHz source at offset frequencies from 0.1 Hz to 1.0 MHz.

To tighten the upper bound of the system’s noise floor, the team is now planning to include a residual phase-noise measurement of a WR1.5 harmonic mixer. Plans also are in the works to extend the measurement range to higher carrier frequencies. See “Phase-Noise Measurement System for the Terahertz-Band,” IEEE Transactions on Terahertz Science And Technology, Nov. 2012, p. 638.

About the Author

Nancy Friedrich

Nancy Friedrich

RF Product Marketing Manager for Aerospace Defense, Keysight Technologies

Nancy Friedrich is RF Product Marketing Manager for Aerospace Defense at Keysight Technologies. Nancy Friedrich started a career in engineering media about two decades ago with a stint editing copy and writing news for Electronic Design. A few years later, she began writing full time as technology editor at Wireless Systems Design. In 2005, Nancy was named editor-in-chief of Microwaves & RF, a position she held (along with other positions as group content head) until 2018. Nancy then moved to a position at UBM, where she was editor-in-chief of Design News and content director for tradeshows including DesignCon, ESC, and the Smart Manufacturing shows.

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