Won-Sang Yoon

A Reconfigurable Circularly Polarized Microstrip Antenna on a Cross-Shape Slotted Ground

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 perturbation can be made on the ground plane and no bias circuit is required on the patch side, the bias circuit has not effect on the main beam radiation. From the experimental results, the impedance bandwidth and CP bandwidth of the proposed antenna have shown up to 150 MHz and 35 MHz, respectively. The peak gain of the proposed antenna is 1.7 dBi for both CP senses.

Low Phase Noise VCO Using Complimentary Bifilar Archimedean Spiral Resonator(CBASR)

In this paper, a novel voltage-controlled oscillator(VCO) using the complimentary bifilar archimedean spiral resonator(CBASR) is presented for reducing the phase noise characteristic. A CBASR has compact dimension, a sharp skirt characteristic in stopband, a low insertion loss in passband, and a large coupling coefficient value, which makes a high Q value and improve the phase noise of VCO. The proposed VCO has the oscillation frequency of 2.396~2.502 GHz in the tuning voltage of 0~5 V, the output power of 7.5 dBm and phase noise of -119.16~-120.2 dBc/㎐ at the offset frequency of 100 kHz in tuning range.

Voltage Controlled Injection-Locked Oscillator Design at 2.4 GHz Band for Wideband Applications

In this paper, a voltage controlled injection-locked oscillator(VC-ILO) is proposed for wideband applications. From the control of the free-running frequency by a varactor diode, the wide frequency locking range can be obtained for low-level injected signals. The proposed VC-ILO is implemented on an FR-4 substrate with a thickness of 0.8 mm. The free-running frequencies of the oscillator is 2.39~2.52 GHz at the control voltage of 0~5 V. While the frequency locking range of over 50 MHz is presented for -10 dBm injected signal level at a fixed frequency, the locking range of over 90 MHz can be achieved for -30 dBm by controlling the free-running frequency.

A Polarization-Switchable Microstrip Patch Antenna Using Corner Slots on Ground Plane and PIN Diodes

In this paper, a switchable circularly polarized microstrip patch antenna using PIN diodes and corner slots on ground plane is proposed at 2.4 GHz. The proposed antenna has a square microstrip patch and ground plane that consists of two pair of slots and PIN diodes. The electrical lengths of the slots are adjusted by using the switching characteristic of the PIN diode, so the polarization of the proposed antenna can be switchable between linear, left-handed(LH) and right-handed(RH). By separating the ground plane for the DC bias, the size reduction effect is also obtained. When the proposed antenna is operated as linear polarization, the return loss and impedance bandwidth are 15 dB, 59 MHz, and when operated as LH and RH polarization, the minimum axial ratio and 3-dB axial ratio bandwidth are 1.17 dB, 1.67 dB, 28 MHz, and 32 MHz, respectively.

A Switchable Circularly Polarized Microstrip Antenna using Asymmetric U-shaped Slotted Ground Structures

In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

An Adaptive Phase Error Correction System for Nonlinear Amplifiers

Abstract 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 conventional amplifier. Moreover, by means of an additional envelope-compensation technique, the improvement of the adjacent channel power ratio (ACPR) is presented. Key Words : Phase Distortion, AM/PM, AM/AM, Calibration, Nonlinear Devices. * 교신저자 : 한상민 (smhan@sch.ac.kr)접수일 09년 07월 13일 수정일 09년 09월 04일 게재확정일 09년 09월 16일 1. 서론 최근의 전력증폭기는 폴라 송신기 (Polar Tx.), 포락선 추적 증폭기(Envelop Tracking Amplifier), LINC와 같은 시스템 송신기 구조 형태로 발전하여 오고 있다 . 이는 10 dB 이상의 최대전력 대 평균전력비(Peak-to-Average Power Ratio, PAPR)를 갖는 OFDM과 같은 신호원을 선형적으로 증폭하기 위해 증폭기의 성능이 더욱 지능적이고 능동적으로 설계할 필요성이 요구됨에 따른 것이다[1]. 이러한 매우 빠른 속도로 변화하는 입력 신호의 크기와 위상을 보정하여 선형적인 증폭을 수행하기 위해 기존에 수행되었던 보정 방식을 feedforward, feedback, pre-distortion (PD)과 같이 크게 3가지로 분류할 수 있다. 특히 디지털 방식의 PD (Digital PD, DPD)는 DSP에 의한 정확한 보정 성능으로 최근 활발한 연구가 진행되고 있는 분야이다[2,3]. 그러나 기본적으로 PD 방식은 적용되는 증폭기 각각의 비선형 특성을 측정하여, 이의 역함수 매트릭스를 산출하여야 하는 어려움이 따른다[4]. 또한 높은 PAPR로 인해 DPD는 매우 빠른 OFDM 신호를 검출해야 하므로, DSP의 복잡한 프로세싱을 요구하는 단점을 가지고 있는 실정이다 [3-6].본 논문에서는 AM/PM 왜곡을 적응형으로 보상할 수 있는 보정 시스템을 제안하였다. 제안된 시스템은 변화하는 입력 위상 오차에 대해 동적인 측정 및 보상을 동시에