• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.931-936
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• 1994

Although an ideal low-pass filter is not physically realizable, it can be approximated on the basis of time reversal techniques. In this paper, we describe a method to approximately implement the ideal low-pass filter and apply it to the pitch extraction system. Experimental results show that our method is effective to estimate the fundamental frequency of the speech signal.

• 융복합기술연구소 논문집
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• 제7권2호
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• pp.25-30
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• 2017

This paper presents the effects of a virtual mass with a low-pass filter on the stability boundary of a virtual spring in the haptic system. In general, a haptic system consists of a haptic device, a sampler, a virtual impedance model and zero-order-hold. The virtual impedance is modeled as a virtual spring and a virtual mass. However the high-frequency noise due to the sampling time and the quantization error of sampled data may be generated when an acceleration is measured to compute the inertia force of the virtual mass. So a low-pass filter is needed to prevent the unstable behavior due to the high-frequency noise. A finite impulse response (FIR) filter is added to the measurement process of the acceleration and the effects on the haptic stability are simulated. According to the virtual mass with the FIR filter and the sampling time, the stability boundary of the virtual spring is analyzed through the simulation. The maximum available stiffness to guarantee the stable behavior is reduced, but simulation results still show that the stability boundary of the haptic system with the virtual mass is larger than that of the haptic system without the virtual mass.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.178-184
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• 2005

In this paper, using diplexer structure and varactor diode controlled by reverse bias voltage for diplexer switch gives possibilities to improve isolation and current characteristics. 1 have newly designed switch with high isolation by application varactor diode corresponding to capacitor of diplexer. The low-pass filter for proposed tunable diplexer passes the microwave signal in the bandwidth for wireless cellular network systems and high-pass filter passes it in the bandwidth for wireless personal communication services (PCS) network systems. As the capacitance of the low-pass filter increases, the cut-off frequency can be moved to low frequency, so that the switch is on state in cellular bandwidth and off state in the PCS bandwidth, in contrast to, as the capacitance for attenuation characteristic of high-pass filter increases, it can be moved to high frequency, so that the switch is off state and on state in the cellular bandwidth. it is possible to improve isolation and current consumption characteristics by application diplexer design methods and varactor diode. 1 expect that the tunable diplexer circuit and design methods should be able to find applications on MMIC and low temperature copired ceramic (LTCC).

• 전기학회논문지
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• 제63권1호
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• pp.35-41
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• 2014

This paper presents a design method of programmable low pass filter(PLPF) which reduce an estimation error of a zero crossing point(ZCP) for a high speed brushless DC(BLDC) motor drive. BLDC motor sensorless drive is possible by estimation of ZCP. The ZCP estimated by detecting a change of back-EMF polarity has the estimation error because noises exist on the measured back-EMF. Therefore a calculated commutation timing using the ZCP is inaccurate. And the inexact commutation timing leads to ripples of 3-phase current and degradation of drive performance. This paper proposes the design method of the PLPF to overcome these problems. First, a speed calculated a inaccurate period of the ZCP is analyzed in the frequency domain. Then, the PLPF that has varying cut-off frequency according to change of the speed is designed on the frequency analysis result. The proposed method is verified by the experiment.

• 한국음향학회지
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• 제43권4호
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• pp.406-413
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• 2024

본 논문은 임펄스성 잡음에 견실한 시간 지연을 추정 방법을 제안한다. 제안하는 방법은 Generalized Cross Correlation - Phase Transform(GCC-PHAT) 방법에 비선형 전처리와 주파수 영역 저역 통과 필터를 사용한다. 본 논문에서는 GCC-PHAT의 연산 과정을 DFT로 다시 해석함으로써 GCC-PHAT에서 시간 지연 추정에 실제 사용되는 유효한 주파수 대역이 있음을 파악하고, 저역 통과 필터 사용하여 유효 대역만을 사용하면 잡음 성분을 줄여서 시간 추정 성능을 향상시킬 수 있음을 보인다. 제안한 방법을 임펄스성 잡음 환경에서 전통적인 GCC-PHAT와 비교함으로써 추정 견실성이 향상됨을 보인다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권5호
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• pp.675-681
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• 2016

A 41dB gain control range $6^{th}$-order band-pass receiver front-end (RFE) using CMOS switched frequency translated impedance (FTI) is presented in a 40 nm CMOS technology. The RFE consists of a frequency tunable RF band-pass filter (BPF), IQ gm cells, and IQ TIAs. The RF BPF has wide gain control range preserving constant filter Q and pass band flatness due to proposed pre-distortion scheme. Also, the RF filter using CMOS switches in FTI blocks shows low clock leakage to signal nodes, and results in low common mode noise and stable operation. The baseband IQ signals are generated by combining baseband Gm cells which receives 8-phase signal outputs down-converted at last stage of FTIs in the RF BPF. The measured results of the RFE show 36.4 dB gain and 6.3 dB NF at maximum gain mode. The pass-band IIP3 and out-band IIP3@20 MHz offset are -10 dBm and +12.6 dBm at maximum gain mode, and +14 dBm and +20.5 dBm at minimum gain mode, respectively. With a 1.2 V power supply, the current consumption of the overall RFE is 40 mA at 500 MHz carrier frequency.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권2호
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• pp.115-121
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• 2002

This paper presents an evolutionary design of digital IIR filters using the genetic algorithm (GA) with modified genetic operators and real-valued encoding. Conventional digital IIR filter design methods involve algebraic transformations of the transfer function of an analog low-pass filter (LPF) that satisfies prescribed filter specifications. Other types of frequency-selective digital fillers as high-pass (HPF), band-pass (BPF), and band-stop (BSF) filters are obtained by appropriate transformations of a prototype low-pass filter. In the GA-based digital IIR filter design scheme, filter coefficients are represented as a set of real-valued genes in a chromosome. Each chromosome represents the structure and weights of an individual filter. GA directly finds the coefficients of the desired filter transfer function through genetic search fur given filter specifications of minimum filter order. Crossover and mutation operators are selected to ensure the stability of resulting IIR filters. Other types of filters can be found independently from the filter specifications, not from algebraic transformations.

• 전기학회논문지
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• 제57권8호
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• pp.1464-1469
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• 2008

A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is $1.5MHz{\sim}3.5MHz$ and the gain control range is $-2.8dB{\sim}2.6dB$. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using $2.5V-0.25{\mu}m$ CMOS processing parameter.

• 대한전자공학회논문지
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• 제4권1호
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• pp.13-21
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• 1967

RC-NIC LPF 설계를 해석적으로 하는 방법을 취급하였으며 4차 타원함수특성을 갖도록 실제LPF를 설계하여 실험적으로 그 동작특성을 고찰하였다.

• 한국정보통신학회논문지
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• 제20권7호
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• pp.1237-1242
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• 2016

본 논문은 병렬 결합선로(coupled-line)와 부채꼴(radial) 개방형 스터브(stub)를 이용한 고조파가 억압된 저역통과 여파기에 대해 제안을 한다. 본 제안한 저역통과 여파기의 특징은 병렬 결합선로의 구조 때문에 고조파가 광대역으로 억압되었다는 결과를 얻을 수 있었다. 저역통과 여파기의 개방형 스터브는 부채꼴로 구성되어 있으며 이는 여파기의 크기를 조절 할 수 있다. 제안한 저역통과 여파기의 크기는 $6.98{\times}7.60mm2$이며 차단 주파수는 2.45 GHz 이다. 분포정수소자(distributed element)로 구성되어 있어 단가면에서 경제적이고 제작이 쉬우며 대량 생산이 가능한 이점이 있다. 또한 광대역 고조파 억압에 대한 대역폭은 128 %이며 여파기의 삽입 및 반사 손실은 각각 1.07 dB 및 19.5 dB를 얻었다.