Won-Sang Yoon

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The novel printed crossed 2times2 dipole array is proposed for broad axial ratio (AR) bandwidth. The broad bandwidth of axial ratio is due to a parasitic dipole crossing over the original dipole that is driven by a semi-rigid coaxial feed with the characteristic impedance of 75 Omega. The crossed dipole, a unit element of the dipole array proposed in this(More)
This letter describes a square patch antenna with a switchable circular polarization (CP) sense. The proposed antenna has four L-shaped slots on the ground plane, and the CP radiation can be generated by current perturbation due to the slotted ground plane. Because the CP sense of the proposed antenna is altered by the current path that is redirected with(More)
A compact circular microstrip patch antenna with a switchable circular polarization (CP) is proposed at 2.4 GHz. An unequal cross-shaped slot on a ground plane is utilized as a perturbation. By switching pin diodes mounted on the slot, the CP sense of each antenna can be simply switched from left-handed (LH) CP to right-handed (RH) CP vice versa. Since the(More)
A novel adaptive phase calibration method is proposed for nonlinear amplifiers. Based on the adaptive process of simple phase vector calculations, the AM/PM distortion can be significantly reduced for various input power. The performance of the proposed method is evaluated for up to 80 % improvements in AM/PM distortions compared with the distortion of a(More)
A single probe-fed reconfigurable circularly polarized microstrip patch antenna with a circular slot is proposed. As one right (left) side point of the circular slot is shorted between the inside of the slot and the rectangular patch, the proposed antenna yields right (left) - handed circular polarization. Each of polarization modes is operated at the same(More)
A frequency tunable super-regenerative oscillator (SRO) is proposed for channel selective receivers in short-range sensor networks. The SRO is designed with the voltage-controlled injection locked oscillator (VC-ILO) and an external quenching signal. A varactor diode is mounted on the resonator in order to achieve frequency tunability. From the experimental(More)
A channel cognitive wireless sensor system is proposed for low-power sensor network applications. Based on an RF spectrum sensing technology, the proposed receiver system is designed with channel-selective operation only for a valid input RF signal at a designated frequency channel. The new receiver architecture was implemented at the ISM band of 2.4-2.5(More)
Linear tapered slot antennas (LTSAs) have been widely investigated as typical examples of coplanar antennas because the LTSAs offer the advantages of wide impedance bandwidth, high gain, and easy fabrication [1], [2]. However, they have high back lobes in the E-plane [3]. In general, the LTSAs are very sensitive to the thickness and the width of their(More)
In this paper we propose a method of removing from synthesizer output spurious signals due to quasi-amplitude modulation and superposition effect in a frequency-hopping synthesizer with direct digital frequency synthesizer (DDFS)-driven phase-locked loop (PLL) architecture, which has the advantages of high frequency resolution, fast transition time, and(More)
A channel cognitive super-regenerative receiver (SRR) system is proposed for low-power sensor network applications. Since the proposed system is designed based on the super-regeneration concept, the receiver is activated and yields the output demodulated signal only for valid incoming RF signals. While the super-regenerative oscillator (SRO) is designed(More)