Jeong-Hwan Kim

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.

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.

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)

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.

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 Analysis in EVM Measurement Using a Monte Carlo Simulation

This paper proposes an error vector magnitude (EVM) measurement method for a wideband code-division multiple-access source using a real-time oscilloscope. The EVM values are extracted from the measured waveform using a signal processing that finds the appropriate carrier phase and symbol timing. Measurement uncertainty is also evaluated based on a Monte Carlo simulation, where the errors from the real-time oscilloscope and the signal processing are taken into account. The measured EVM of a source at 900 MHz is (0.2586 ± 0.0040)%, (0.2617 ± 0.0060)%, and (0.2543 ± 0.0078)% at 95% confidence level when the real-time oscilloscope has a bandwidth of 2, 4, and 20 GHz, respectively.

RF Peak Power Calibration of Modulated Signals

A new calibration method of a power sensor for measuring the peak power of digitally modulated signals is introduced. This method uses an amplitude-modulated sine-wave source and is relatively simple to the currently available method that uses a digitally modulated signal source and an oscilloscope. Basic theory and calibration procedures for measuring the correction factor for peak power are described. Using a commercial peak power sensor that is calibrated with the proposed method, the peak power of a Global System for Mobile Communications at 900 MHz modulated signal is measured and compared with that measured by an oscilloscope. Various examples of choosing the calibration parameters are also discussed. The best uncertainty in the calibration of a peak power sensor is estimated to be 0.34% (k = 2).

Fabrication of Small Reference Probe and Its Application

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

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.