Jeong-Il Park

Design, Construction, and Performance Evaluation of a Cryogenic 7-mm Coaxial Noise Standard

A cryogenic 7-mm coaxial noise standard at 77.35 K has been designed and constructed. A ferrite composite-matched termination was used as a thermal noise source in the frequency range of 4.5-18 GHz. The noise temperature of the noise standard has been determined by measuring the temperature distribution and attenuation constant of a thermally isolated coaxial line and the attenuation of the output connector. The effective noise temperature has been evaluated to be 84.07-92.21 K with an uncertainty of 1.26-1.67 K (k = 2)

Determining Noise Temperature of a Noise Source Using Calibrated Noise Sources and an RF Attenuator

A system to measure the noise temperature (NT) of noise sources is implemented in the frequency range of 18-26.5 GHz for the case where noise sources commercially available have only one nominal NT, e.g., 9500 K being equivalent to 15-dB excess noise ratio. For the Y-factor method, two noise sources, i.e., a noise source and another with a radio-frequency attenuator, serve as the standard noise sources. The noise power output of the noise sources are measured using a commercial noise figure measurement instrument. Measurement results are presented, and its uncertainty has been evaluated to be 0.23-0.25 dB (k = 2) .

Uncertainty evaluation of a broadband attenuation standard

A standard step attenuator has been developed. It comprises a build-up chain of ten steps of power ratio measurement and operates in a frequency range of 10 MHz to 18 GHz. The overall system has a dynamic range of 90 dB and an expanded uncertainty of 0.006 dB (k=2). The system is used as an attenuation standard in a series radio-frequency substitution scheme. The uncertainty factors in the attenuation measurement of 40 dB at 5 GHz are fully described. For the calibration of a typical step attenuator, the expanded uncertainties are 0.011 dB for the attenuation range up to 80 dB, including the mismatch uncertainty.

A broadband attenuation standard

A standard step attenuator, composed of ten steps of a build-up chain of power measurement and operating from 10 MHz to 18 GHz, has been developed. Each step shows a nominal attenuation of about 9 dB and an expanded uncertainty of 0.0018 dB at 30 MHz. The overall system has a dynamic range over 90 dB.

Direct comparison technique using a transfer power standard with an adapter and its uncertainty

The direct comparison technique using a transfer power standard with an adapter and its uncertainty are considered. A waveguide thermistor mount with an appropriate waveguide-to-coaxial adapter serves a new combined coaxial power standard. In order to obtain the effective efficiency of the combined standard, the phase as well as the magnitude of the adapter scattering parameters have to be known. Consequently, the adapter scattering parameters give rise to an additional uncertainty to the direct comparison technique. In this paper, a K-band waveguide thermistor mount with a WR42-2.4-mm adapter is used to calibrate a 2.4-mm coaxial power sensor. Measurement results are presented and its uncertainty is evaluated to be 2.5 % (k=2) in the frequency range of 18 GHz to 26.5 GHz.

Comparison of Antenna Parameters of R-/S-Band Standard Gain Horn Antennas

A comparison of the antenna parameters for R-band (1.7?2.6 GHz) and S-band (2.6?3.95 GHz) standard gain horn antennas has been performed by the Korea Research Institute of Standards and Science (KRISS), together with seven domestic participants from private companies and public institutions. Its purpose, as a proficiency test program of the ‘Antenna Measurement Club’ of KRISS, was to check equivalences in antenna parameter measurements between KRISS and the participants, particularly in the R-/S-band, to support antenna manufacturers and end users in Korea. The measurement parameters of this comparison are the power gain, radiation pattern, and reflection coefficient of the traveling standards for R-/S-band pyramidal standard gain horn antennas. The comparison used a gain comparison method and an extrapolation method to measure the power gain of the two traveling standards; the radiation patterns were measured in the far-field region of the transmitting and receiving antennas.

A new method for the determination of the reflection and transmission characteristics of dielectric materials

This paper presents a new method for the determination of the reflection and transmission characteristics of dielectric materials that are the parameters for the calculation of the complex permittivity using the Nicolson-Ross-Weir (NRW) method. In transmission line methods, most widely used methods for broadband permittivity measurements, the NRW method gives a stability problem for low-loss dielectric materials near the thickness resonance frequencies. The proposed method successfully removes the problem using a relationship between the reflection and transmission characteristics. The proposed method is a new iterative transmission/reflection method applicable to permittivity measurements using arbitrary sample lengths in wide-band frequencies.

Determining noise temperature of a noise source using calibrated noise sources and an RF attenuator

A calibration system for noise sources is implemented in the frequency range of 18 GHz to 26.5 GHz. For the Y-factor method, a diode noise source and one with an RF attenuator are used as standard noise sources. Measured results and evaluated uncertainty are presented.

Calibration of a 3.5 mm coaxial power sensor using a transfer standard with 7 mm coaxial or WR42 waveguide connectors

A calibration system of a 3.5 mm coaxial power sensor was implemented using transfer standards with 7 mm coaxial or K-band waveguide input connectors. A 7 mm-3.5 mm or WR42-3.5 mm adapter was used to form a combined transfer standard. The effective efficiency of the combined transfer standard was obtained. The 3.5 mm coaxial power sensor was calibrated using the well-known direct comparison method and measurement uncertainty was evaluated.

Uncertainty improvement of monopole antenna calibration using equivalent capacitance substitution method

In this paper a method to improve the measurement uncertainty from the inaccurate representation of the equivalent capacitance of a short monopole antenna element is proposed for the equivalent capacitance substitution method (ECSM). And some consideration about the model formula of the effective height of a monopole antenna is also discussed.