Jae-Yong Kwon

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.

Field analysis of electro-optic probes for minimally invasive microwave sampling.

We numerically and experimentally investigate the field invasiveness of microwave signals using an electro-optic technique. The distortion of the standing wave voltage and pulse waveform probed by the electro-optic technique is explored through both minimally invasive external and non-invasive internal sensing configurations. First, we analyzed the continuous wave microwave field imaging on a millimeter- scale coaxial transmission line using a highly accurate and stable electro- optic scanning system. The electric field images from the microwave device are attained virtually non-invasively using a miniaturized fiber-coupled electro-optic probe. The accuracy of the field imaging associated with various probe styles is investigated by numerical analysis and experiment. Then, we analyzed the waveform of the coaxial transmission line up to 50 GHz using a pulsed electro-optic system with an external probe set. Finally, the invasive analysis was extended to the sub-millimeter-scale on-wafer coplanar waveguides, where the voltage waveforms are measured using a minimally invasive external probe as well as an internal wafer probe for non-invasive sampling.

The Design of Calculable Standard Dipole Antennas in the Frequency Range of 1~3 GHz

This paper presents the design of a calculable standard dipole antenna with a hybrid balun in the frequency range of 1 GHz to 3 GHz. A new formula of the antenna factor for a dipole antenna with a hybrid balun is derived using the power mismatch-loss concept. The antenna factors derived in this paper are in good agreement with the results calculated from S-parameters. The design results show that the calculable dipole antenna with a hybrid balun can be characterized by power mismatch-loss component factors.

Field-calibrated electro-optic probe using interferometric modulations

A very concise field-calibrated electro-optic probe using interference of modulated beams is presented. A model for interferometric electro-optic sensing with a sensor probe is proposed, utilizing the interference fringing slopes and field-induced electro-optic phase retardations. The sensing dynamic range is experimentally explored by investigating the modulation slopes and retardations with respect to the probe beams polarizations. The probe shows a dynamic range ≥45 dB over the microstrip lines. This sensitivity is acceptable for realizing electric field imaging of radiative electronic devices. The absolute sensitivity of the probe is also determined with a micro-TEM cell that generates accurate electric fields with calculable strength for probe calibrations.

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.

Adiabatic Design for a Coaxial Transmission Line

This paper proposes an air-gap applied adiabatic line for a coaxial transmission line. The adiabatic characteristics with excellent microwave transmission were simulated in terms of the S-parameter and the heat transfer of coaxial lines with a finite-element-method-based tool for the adiabatic microwave design. The detailed design scheme of the air-gap adiabatic line is presented and its performance is evaluated. The adiabatic efficiency associated with microwave feature was analyzed by a resistive equivalent circuit model of the line. We made a stainless steel air-gap adiabatic line that had about 11 times greater thermal resistance than that of a gapless coaxial line, a beryllium copper line, with the increment of just 0.4-dB insertion loss. We also propose a solution to improve the low-frequency transmission of an air-gap adiabatic line with a tunable ground wire for broad-band feature.

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.

Spectro-Temporal Mismatch Analysis of a Transmission Line Based on on-Wafer Optical Sampling

We present an optical sampling technique that enables exploration of mismatches of a microstrip transmission line based on reflection analyses of electromagnetic pulses. The external electro-optic sampling scheme with a minute crystal detects high-speed electrical pulses over arbitrary locations of a line with very low-intrusiveness. The temporal pulsed signals measured with an on-wafer optical probing system and the corresponding spectra are obtained to analyze the transfer characteristics of a microstrip transmission line with 20 GHz bandwidth. The spectro-temporal response was cross-checked with commercial instruments. Applications of this optical probing technique to explore mismatches at the terminal port — based on both time and frequency domain reflectometry analyses — are also presented.

Vector Network Analysis Using a One-Path, Frequency-Multiplied Photonic Link

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.

A design and implementation of 3.5 mm coaxial microcalorimeter for RF and microwave power standards at KRISS

This paper describes the status of RF power standards at KRISS briefly and introduces the on going project which developing a 3.5 mm coaxial microcalorimeter for implementing the national power standard up to 26.5 GHz. Microcalorimeter design and developing process which based on CAD and computer aided engineering (CAE) will be discussed and some results will be shown.