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Low Spurious Image Rejection Mixer for K-band Applications
Lee, Moon-Que,Ryu, Keun-Kwan,Kim, Hyeong-Seok The Korean Institute of Electrical Engineers 2004 KIEE International Transactions on Electrophysics Vol.4C No.6
A balanced single side-band (SSB) mixer employing a sub-harmonic configuration is designed for up and down conversions in K-band. The designed mixer uses anti-parallel diode (APD) pairs to effectively eliminate even harmonics of the local oscillator (LO) spurious signal. To reduce the odd harmonics of LO at the RF port, we employ a balanced configuration for LO. The fabricated chip shows 12$\pm$2dB of conversion loss and image-rejection ratio of about 20dB for down conversion at RF frequencies of 24-27.5GHz. As an up-conversion mode, the designed chip shows 12dB of conversion loss and image-rejection ratio of 20 ~ 25 dB at RF frequencies of 25 to 27GHz. The odd harmonics of the LO are measured below -37dBc.
Dielectric Band-Pass Filter with Attenuation Poles at Desired Frequencies
Lee, Moon-Que The Korean Institute of Electrical Engineers 2004 KIEE International Transactions on Electrophysics Vol.4C No.6
An analytic design formula is proposed for a TEM mode dielectric bandpass filter with attenuation poles at desired frequencies in the stop band. In order to sustain the constant ripple in the passband due to attenuation poles, the initial resonant frequencies of the various resonators adopted in a filter with attenuation poles are newly calculated. The proposed design theory is verified by designing various bandpass filters with attenuation poles in the stop band.
Lee, Moon-Que,Ryu, Keun-Kwan,Yom, In-Bok Electronics and Telecommunications Research Instit 2001 ETRI Journal Vol.23 No.4
The phase noise reduction in a configuration of the HEMT oscillator with a dielectric resonator coupled by a quarter-wavelength impedance inverter is investigated. Two HEMT oscillators for a satellite payload system are manufactured in the same configuration except for the coupling configuration of the dielectric resonator (DR) in order to empirically demonstrate the phase noise reduction. Experimental result shows that a phase noise reduction by 14 dB can be enhanced by increasing the characteristic impedance of a coupling microstrip impedance inverter.
Six-port QPSK demodulator for optimal K-band multiport amplifier calibration
Lee, Moon-Que,Yu, Jong Won,Lee, Han Lim,Moon, Seong-Mo Institution of Electrical Engineers 2014 Electronics letters Vol.50 No.8
A wideband six-port-based demodulator is proposed and applied as a quadrature phase shift keying (QPSK) demodulator for optimal K-band multiport amplifier (MPA) calibration circuitry. The proposed six-port demodulator adopts wideband ring hybrids for optimal 180 degrees phase balance in local oscillator signal paths. In addition, a voltage-controlled reflection-type phase shifter and an attenuator are integrated into the six-port structure to ensure accurate magnitude and phase balance over broadband operation, resulting in optimal phase and amplitude error detection for the MPA system. To verify the proposed structure, RF demodulation of the K-band QPSK modulated signal was demonstrated for purpose of MPA calibration.
Moon-Que Lee,Han Lim Lee,Dong-Hoon Park 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.4
This letter proposes a reconfigurable directional coupler that uses a variable impedance mismatch reflector to achieve high isolation characteristics in the antenna front end. The reconfigurable coupler consists of a directional coupler and a single-pole four-throw (SP4T) switch with different load impedances as a variable load mismatch reflector. Selection of the load impedance by the reflector allows cancellation of the reflected signal due to antenna load mismatch and the leakage from the input to isolation port of the directional coupler, resulting in high isolation characteristics. The performance of the proposed architecture in separating the received (Rx) signal from the transmitted (Tx) signal in the antenna front end was verified by implementing and testing the reconfigurable coupler at 917 MHz for UHF radio-frequency identification (RFID) applications. The proposed reconfigurable directional coupler showed an improvement in the isolation characteristics of more than 20 dB at the operation frequency band.
짧은 결합길이를 갖는 초소형 발룬 및 이를 응용한 평형 필터 설계
李文揆(Moon-Que Lee) 대한전기학회 2006 전기학회논문지C Vol.55 No.4
A distributed balun such as Marchand balun typically shows good phase and amplitude balances, but its size is somewhat large especially in lower frequency band. In contrast, a lumped balun has compact size but its performance is not good compared with that of a distributed one. In this paper the distributed-coupled line can be reduced effectively by using the lumped-distributed implementation. Designed balun has two coupled line of each λ/72 and shows magnitude balance of 0.05 ㏈, phase balance of 0.7° in passband. Balanced-type filter is designed using balun and it has insertion loss of 8 ㏈, return loss of 7 ㏈, magnitude balance of 0.2 ㏈, and phase balance of 1.2° in passband.