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순방향 링크 AOA 측정치를 이용한 CFS 방법의 성능 개선
임현자(Hyun-Ja Im),박지원(Ji-Won Park),송승헌(Seung-Hun Song),성태경(Tae-Kyung Sung) 대한전기학회 2009 전기학회논문지 Vol.58 No.3
This paper presents a modified CFS (Closed-Form Solution) for FLAOA (Forward Link AOA) measurements. During when the pseudo-measurement equation for FLAOA is derived, the angle measurement noise is treated more carefully in approximation. As the covariance matrix of the pseudo-measurement noise is influenced by unknown user positions and azimuth, a two-step estimation technique is used in the proposed CFS. The performance of the proposed CFS for FLAOA is compared to that of the conventional CFS for FLAOA and RLAOA (Reverse Link AOA) in a computer simulation. Simulation results show that the proposed method is potentially suitable for applications involving the localization and guidance of indoor mobile robots..
약 신호 환경의 AGPS를 위한 잔여주파수 추정기의 주파수 영역 성능 분석
박지희(Ji Hee Park),임현자(Hyun Ja Im),송승헌(Seung-Hun Song),성태경(Tae-Kyung Sung) 제어로봇시스템학회 2010 제어·로봇·시스템학회 논문지 Vol.16 No.7
In AGPS method, user position can be obtained even in the shadow region by improving signal sensitivity. A hybrid long integration scheme employing both coherent and non-coherent integration method is commonly used in AGPS receivers. Because coherent loss increases as residual frequency become large, residual frequency should be minimized to maximize coherent integration gain. This paper presents performance analysis of residual frequency estimator using FFT in fine-time assistance AGPS method. Considering the hardware complexity and the estimation accuracy, optimal length of FFT is proposed for GPS L1 C/A signal. Signal sensitivity for estimating the residual frequency is also analysed. By field experimental results, it is found that the residual frequency can be successfully estimated using 1 second snap-shot data when GPS signal strength is larger than -150 dBm and its RMS error is 3Hz.
다중위상-그레이코드 카운터를 이용한 적외선 센서용 저전력 ADC 설계
김영선(Yeong Seon Kim),장병탁(Byung Tak Jang),임현자(Hyun Ja Im),이희철(Hee Chul Lee) 대한전자공학회 2018 전자공학회논문지 Vol.55 No.10
본 논문에서는 저전력 적외선 영상 시스템을 위하여, 다중위상-그레이코드 카운터를 적용한 아날로그 디지털 변환 회로(Analog to Digital Converter, ADC)를 제안하였다. 제안한 회로는 column-level single slope ADC 구조에 다중위상-그레이코드 카운터를 적용하여 기존의 이진수 디지털 카운터에서 요구하는 클럭 주파수를 낮추어 전력소모를 감소시키고, 디지털 노이즈에 강인한 특성을 갖는다. 또한 CTIA ramp 회로, column 별 비교기와 메모리를 통해 다중 column에서 입력되는 적외선 입력 신호를 동시에 변환할 수 있다. 제안한 회로는 0.18um CMOS 공정을 통해 설계 되었으며, 단위 column 회로의 전력소모는 171uW 이다. In this paper, we proposed an analog to digital converter(ADC) with multi phase-gray code digital counter for low power infrared image system. The proposed column-level single slope ADC can reduce clock frequency required in conventional binary digital counter and have lower power consumption with robustness to digital noise. Furthermore, the designed CTIA ramp generator, comparator and memory in each column can convert the multiple column infrared input signal at the same time. The proposed circuit was designed with 0.18um CMOS process. The power consumption result of the proposed unit column circuit was 171uW.