Jin-Seob Kang

Development of a 3.5-mm Coaxial Microcalorimeter for RF and Microwave Power Standards at KRISS

We have developed a 3.5-mm coaxial microcalorimeter that will become a national power standard up to 26.5 GHz. Several core parts such as a thermostat, an adiabatic line, a thermopile, and reference standards are described in detail. Some measurement data are shown for a system performance check. A finite-element method simulation of the adiabatic line is shown. A model of the effect of the adiabatic line on thermopile measurement is introduced. Effective efficiency at selected frequencies is presented for the reference standards.

Characterization Method of Electric Field Probe by Using Transfer Standard in GTEM Cell

In this paper, we introduce a simple and wideband characterization method for electric field probes using a transfer standard. As a transfer standard, a thin disk-type reference probe that can operate from 50 to 1000 MHz is used and calibrated using a micro transverse electromagnetic (mu-TEM) cell. A gigahertz transverse electromagnetic (GTEM) cell is used to generate a reference electric field. It has been shown that the uncertainty of the proposed method can be increased due to the imperfection of the field condition in the cell. According to the measurement result, the proposed characterization method for the electric probes agrees within 6.3%, compared with the method that uses the TEM cell and standard antennas in a fully anechoic chamber.

Novel attenuation standards at microwave frequencies and evaluation of their uncertainty

We have developed two coaxial-type microwave attenuation standards using the power ratio transfer method. One standard operates in the frequency range of 18 GHz to 26.5 GHz, and has a dynamic range of 80 dB. Its expanded uncertainty (k = 2) is estimated to be 0.01 dB/80 dB. The other operates in the frequency range of 26.5 GHz to 40 GHz, and has a dynamic range of 60 dB and an expanded uncertainty of 0.009 dB/60 dB. We present an example for calibration of a 40 dB step attenuator using the attenuation standard in a series radio-frequency substitution scheme. The expanded uncertainty (k = 2) is 0.01 dB including the mismatch uncertainty.

A W-Band Millimeter-Wave Power Standard Transfer System Using the Direct Comparison Method

This paper introduces a W-band millimeter-wave power standard transfer system using the direct comparison method. The transfer system was developed to evaluate the effective efficiency and calibration factor of a W-band waveguide power sensor. The evaluation method and the measured results of the directional coupler that characterizes the calibration system are studied. The uncertainties of the standard transfer system are investigated, and the major uncertainty contributors are discussed as well. The performance of the realized W-band power standard transfer system was verified by comparing results with reference values.

Intercomparison of Standard Gain Horn Antennas at

An intercomparison of two W-band (75-110 GHz) standard gain horn antennas of nominal gains 24 and 27 dB has been performed at the Korea Research Institute of Standards and Science (KRISS), National Physical Laboratory (NPL), and National Institute of Standards and Technology (NIST). The measurement parameters for this comparison are the power gain and complex reflection coefficient of the traveling standards measured at 75, 95, and 110 GHz, and, as an option, the swept-frequency power gain measured over the frequency range of 75-110 GHz with a finite frequency step. All participants performed the fixed-frequency antenna measurements, whereas the swept-frequency antenna measurements were carried out by the NPL and the NIST. This paper describes the comparison and its measurement results with uncertainties. Generally, the agreement between the results in all the measurements is within the uncertainty of each participant, except for fixed-frequency gain results of the high-gain antenna at 110 GHz, reflection coefficient results at some fixed frequencies, and swept-frequency gain results of the high-gain antenna in the low- and high-frequency regions of the W-band.

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This paper presents a disk-type small reference probe operating up to 1 GHz as an electric field transfer sensor. The probe is calibrated using a mu-TEM cell and demonstrates a wide useable electric field strength range. Design and calibration methods are presented. The probe is suitable for testing and comparing the performances of reference field generation systems, both TEM cells and antennas. As an application, a technique for measuring the antenna gain is proposed and applied to open-ended waveguide antennas

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A W-band waveguide noise measurement system has been developed for noise temperature (NT) standards. The system consists of two standard noise sources and a waveguide radiometer. A horn-type cryogenic noise source operating at the liquid nitrogen temperature and an ambient temperature termination have been employed as standard noise sources. To measure noise power radiated from the noise sources including a device under test, a total-power waveguide radiometer has been constructed and its performance has been evaluated. Measured NT of a commercial waveguide noise source is presented with the measurement uncertainty of 0.10-0.13 dB (k=2) in W-band.

Fabrication of Small Reference Probe and Its Application

A cryogenic noise reference standard consists of an antenna, a cavity, an electromagnetic absorber, and a liquid nitrogen container. The horn antenna is installed at the upper part of the cavity to measure the thermal noise radiated from the absorber carefully placed at the bottom of the cavity. By filling liquid nitrogen to an appropriate level the electromagnetic absorber is maintained at approximately 77 K. In this paper, some design considerations are discussed to minimize the diffraction from the internal surface of the horn antenna. Using the resultant dimension of the horn, the attenuation of the overall horn antenna is evaluated to be 0.033 dB to 0.037 dB in the frequency range of 75 GHz to 110 GHz. The calculated attenuation with other relevant parameters is used to obtain the calculable output noise temperature of the cryogenic noise reference standard.

A Thermal Noise Measurement System for Noise Temperature Standards in

In this paper, a free-space material measurement technique is discussed in W-band(75~110 GHz). For the accurate measurement of S-parameters of an MUT(Material Under Test) in free space, a W-band quasi-optical free-space material measurement system, less affected by the measurement environments, is discussed, and GRL(Gated Reflect Line) method for calibrating the measurement system is described. Proposed technique is verified for `Air` and measurement results for arystal plates of thickness 1.1 mm, 2 mm, 2.75 mm and 5 mm are also shown.

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A simplified, practical vector network analyzer (VNA) that uses mature radio-over-fiber technology has been designed and demonstrated. The measurement concept allows the full S-parameters of a microwave device (or antenna) to be obtained while minimizing the detrimental effects of electrical cables, which are replaced with a photonic link. A variety of high-frequency light modulation schemes with frequency sweeping capabilities are presented to realize a one-path (single, forward), frequency-multiplied optical link for VNA applications. Using the photonic one-path link, full two-port S-parameters have been extracted based on five-term error modeling, which has half the error terms compared with the standard duplex configuration. The S-parameters of a microwave filter and antenna measured using frequency-multiplied optical links are found to be in good agreement with those obtained using a conventional VNA.