Young-Pyo Hong

Two-tier calibrated electro-optic sensing system for intense field characterization of high-power W-band gyrotron.

We present a field-calibrated electro-optic sensing system for measurement of the electric field radiating from a high-power vacuum oscillator at ~95 GHz. The intense electric field is measured in absolute scale via two probe-calibration steps, associated with a photonic heterodyne scheme. First, a micro-electro-optic probe, fabricated to less than one-tenth the oscillation wavelength scale to minimize field-perturbation due to the probe, is placed on the aperture of a field-calculable WR-10 waveguide to calibrate the probe in V/m scale. Then, using this arrangement as a calibrated reference probe at the first-tier position, another probe-bulkier, and thus more robust and sensitive but not accessible to the aperture-is calibrated at the second-tier position away from the waveguide aperture. This two-tier calibrated probe was utilized to diagnose the sub-MV/m scale of intense electric fields and emissions from a high-power W-band gyrotron. The experimental results obtained proved consistent with calculated analytical results-verifying the efficacy of the developed system.

V- and W-band waveguide microcalorimeters for millimeter-wave power standards

This paper introduces a recently constructed V-band and an under development W-band waveguide microcalorimeters that will serve as primary power standards in KRISS. The design scheme of the V- and W-band microcalorimeters is briefly presented, and their basic performance was checked. We propose a thermoelectric reference standard that will cover V- and W- bands. We also propose an in-house V-band source signal module for high RF power and low signal impurity output.

Radio-frequency characteristic variation of interdigital capacitor having multilayer graphene of various widths

In this paper, a radio-frequency circuit model of an interdigital capacitor (IDC) with a multilayer graphene (MLG) width variation is proposed. The circuit model with three sample configurations, i.e., a bare IDC, IDC-MLG with a width of 5 μm, and IDC-MLG with a width of 20 μm, is constructed via a fitted method based on the measured samples. The simulated results of the circuit model are validated through the RF characteristics, e.g., the capacitance and the self-resonance frequency, of the measured samples. From the circuit model, all samples show not only a similar capacitance behavior but also an identical self-resonance frequency of 10 GHz. Moreover, the R, L, and C values of MLG with a 5 μm width (MLG with a 20 μm width) alone are approximately 0.8 kΩ (0.5 kΩ), 0.5 nH (0.9 nH), and 0.3 pF (0.1 pF), respectively. As a result, we find that the simulated results are in good agreement with RF characteristics of the measured samples. In the future, we expect that the proposed circuit model of an IDC with...

Kilowatt peak-power wideband active phased-array transmitter

In this paper, an active phased-array transmitter that can be used to generate 1-kW peak pulsed output is presented. It consists of 192-channel transmit modules and each transmit module with greater than 6 W of CW output power is connected to rigid tapered slot antenna in the frequency range 6–18 GHz. In transmit module, integrated multi-function corechip is designed in order to individually control both amplitude and phase of array antennas. Far-field radiation pattern of active phased-array transmitter was obtained using field-transformation method after carrying out near-field measurement in anechoic chamber. Electronic beam steering capability of active phase-array transmitter was demonstrated with a scan angle of ±20° in both azimuth and elevation angle. The overall system size is 840×480×630 mm3.

Upper frequency limit depending on potential shape in a QD-based single electron pump

Our quantum-dot (QD) electron pump has uniqueness in design in that the QD potential shape can be manipulated, especially its potential depth can be controlled by a plunger gate. We find that there exist strong correlations between the potential depth of the QD and the upper frequency limit, fm, when the modulating microwave power is fixed. As the depth of the QD potential is deepened, fm shows decreasing characteristics while the flatness of the 1st current plateau is increased. We have semi-quantitatively analyzed these correlations by using the notion of so-called “non-adiabatic Coulomb blockade gap energy,” ΔELU. We find that ΔELU parameter being under control by a plunger gate is proportional to the pumping frequency f.

Measurement of high-permittivity dielectric characteristics at microwave and mm-wave frequencies

This paper describes two methods for measuring the complex permittivity of a dielectric material at microwave (18-25 GHz) and mm-wave (72, 80 and 90 GHz) frequencies. Two separate measurement systems with vector network analyzers are used. One based on rectangular waveguide for microwave frequencies and the other based an open resonator for mm-wave frequencies. Estimates are provided for the uncertainties of the two measurement systems.