Hyoung-Jong Kim

2.46 GHz solid-state high-power oscillator with planar cavity resonator

In this paper, we have studied a high power oscillator of a high RF output power and a good phase noise. We designed the high power oscillator using LDMOS(laterally diffused metal oxide semiconductor) device by the use of an Agilent advanced design system (ADS). We also designed the rectangular cavity resonator in order to obtain a good phase noise by using a 3-D high frequency structure simulator (HFSS) code. In Section II, the simulation and measurement results of the planar cavity resonator (PCR) were described. In section III, the output characteristics of a high power oscillator using PCR was described.

Pulse Operation of an Inverse Class-F GaN Power Amplifier

This paper presents an inverse class-F power amplifier (PA) based on gallium nitride (GaN) high electron mobility transistor (HEMT) at 1 GHz. The implemented PA has a peak power-added-efficiency (PAE) of 74.1%, drain efficiency (DE) of 77.36%, and a gain of 13.76 dB at an output power of 39.58 dBm with a continuous wave operation at 28 volts. We have carried out the experiments with various pulsed operating conditions. A RF performance peak PAE of 74.28% with drain efficiency of 77.57% and a gain of 13.73 dB, at an output power of 39.66 dBm, was obtained at a pulse width of 100 mus with a duty of 10%. To evaluate the linearity of the inverse class-F amplifier, two-tone measurements have been tested. At a tone spacing of 100 kHz, the measured third-order intermodulation distortion (IMD3) was 13.2 dBc at peak PAE.

A Study on Design and Fabrication of SRD Impulse Generator and Antenna for Ground Penetrating Radar System

In this paper, a ground penetrating radar(GPR) system is implemented for landmine detection. The performance of the GPR system is associated with the characteristics of local soil and buried target. The choice of the center frequency and the bandwidth of the GPR system are the key factors in the GPR system design. To detect a small and shallow target, the higher frequencies are needed for high depth resolution. We have been designed, fabricated and tested a new impulse generator using step recovery diodes. The measured impulse response has an amplitude of 6.2V and a pulse width of 250ps. The implemented GPR system has been tested real environmental conditions and has proved its ability to detect a small buried target.

A Study on Efficiency Improvement of X-Band Power Amplifier Using Harmonic Control Circuit

Abstract In this paper, a simple and effective active load-pull method is proposed, and the method to improve the efficiency of X-band power amplifier using harmonic control circuit is presented. The proposed active load-pull system mainly consists of directional coupler, phase shifter, short circuit, and power amplifier, and allows a user to access reflection coefficients near the edge of the Smith chart( Γ 1) easily. The device used in this paper is Mitsubishis GaAs FET MGF1801, and the operating frequency of the power amplifier is 9 GHz, The amplifier had output power of 21.65 dBm and drain efficiency of 24.9 % at class-A, and had output power of 21.46 dBm and drain efficiency of 53.3 % at class-AB. Harmonic control circuit is designed only second and third harmonic components because of the bandwidth limitation of the microwave components. The drain efficiency is improved as much as 6.4 % compared with class-AB power amplifier. Key words : Active Load-Pull, Harmonic Load-Pull, High Efficiency, Switching-Mode Amplifier