Improvement of the Q-factor measurement in RF cavities

A frequently used Q factor measurement procedure consists of determining the values of the input reflection coefficient vs. frequency with the use of a network analyzer, and processing the measured values with a data-fitting procedure to evaluate the location and the size of the corresponding Q-circle. That information is then used to compute the value of the loaded and unloaded Q factors and the coupling coefficient of the resonator being tested. This paper describes a novel method of post-processing the measured data, which also provides information on the uncertainty of the obtained results. Numerical examples show that this a-posteriori procedure can not only provide the uncertainty estimates but also improve the accuracy of results, even in the presence of a significant level of random measurement noise.

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Q Factor Measurement

The Measurement, Instrumentation and Sensors Handbook on CD-ROM ◽

10.1201/9780415876179.ch52 ◽

1999 ◽

Author(s):

Albert Helfrick

Keyword(s):

Q Factor ◽

Factor Measurement

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Data Processing For Q Factor Measurement

19th ARFTG Conference Digest ◽

10.1109/arftg.1994.327064 ◽

1994 ◽

Author(s):

Darko Kajfez

Keyword(s):

Data Processing ◽

Q Factor ◽

Factor Measurement

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On-Chip Measurement of Quality Factor Implemented in 0.35μm CMOS

Journal of Circuits System and Computers ◽

10.1142/s0218126616500870 ◽

2016 ◽

Vol 25 (08) ◽

pp. 1650087

Author(s):

Xiaojiao Ren ◽

Ming Zhang ◽

Nicolas Llaser ◽

Yiqi Zhuang

Keyword(s):

Quality Factor ◽

Time Domain ◽

Cmos Technology ◽

Micro Electro Mechanical System ◽

Measuring System ◽

Q Factor ◽

Mems Resonator ◽

Transconductance Amplifier ◽

Factor Measurement ◽

On Chip

Based on time-domain quality factor (Q-factor) measurement principle, we have proposed an architecture which has the potential to be integrated on-chip. Thanks to the proposed original reconfigurable structure, the main measurement error from the offset of the operational transconductance amplifier (OTA) used can be cancelled automatically during the measurement operation, leading to a high accuracy Q-factor measurement. The digital control circuit plays an important role in the automatic passage between the two configurations designed, i.e., peak detector and comparator. The main advantages of the proposed time-domain Q-factor measurement lay on the possibility of being integrated next to the Micro Electro Mechanical System (MEMS) resonator to be measured, the miniaturization of the whole measuring system as well as the enhancement of the measurement performance, and to guide the design of such architecture, a theoretical analysis linking the required accuracy and the given Q-factor to the circuit parameters have been given in this paper. The proposed circuit is designed and simulated in a 0.35[Formula: see text][Formula: see text]m Complementary Metal Oxide Semiconductors (CMOS) technology. The post-layout simulation results show that the operating frequency can reach up to 200[Formula: see text]kHz with an accuracy of 0.4%.

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