• Journal of electromagnetic engineering and science
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• v.11 no.2
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• pp.83-90
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• 2011

In this paper, we present the design method for a low-pass type inverter, which can effectively suppress the spurious response associated with band-pass filters. The inverter has a length of ${\lambda}/4$ and employs not only a stepped-impedance configuration but also asymmetrical and bending structures in order to improve frequency selectivity and compactness. The inverter is applied as an impedance/admittance inverter to the ultra-wideband (UWB) band-pass filter. The UWB band-pass filter configuration is based on a stub band-pass filter consisting of quarter-wavelength impedance inverters and shunt short-circuited stubs ${\lambda}/4$ in length. The asymmetrical stepped-impedance low-pass type inverter improves not only the spurious responses, but also the return loss characteristics associated with a UWB band-pass filter, while a compact size is maintained. The UWB band-pass filter using the proposed inverters is fabricated and tested. The measured results show excellent attenuation characteristics at out-band frequencies, which exceed 18 dB up to 39 GHz. The insertion loss within the pass-band (from 3.1 to 10.6 GHz) is below 1.7 dB, the return loss is below 10 dB, and the group delay is below 1 ns.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.348-351
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• 2001

In this paper, the Gm-C filter for low voltage and low power applications using a fully-differential transconductor is presented. The designed transconductor using the series composite transistors and the low voltage composite transistors has wide input range at low supply voltage. A negative resistor load (NRL) technology for high DC gain of the transconductor is employed with a common mode feedback(CMFB). As a design example, the third-order Elliptic lowpass filter is designed. The designed filter is simulated and examined by HSPICE using TSMC $0.35{\mu}m$ CMOS n-well parameters. The simulation results show 138kHz cutoff frequency and 11.05mW power dissipation with a 3.3V supply voltage.

• Journal of Power Electronics
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• v.8 no.4
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• pp.301-308
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• 2008

This paper proposes a method of improving the stability in sensor-less control of permanent magnet synchronous motors. The control method for low-speed region is divided into two: One is a high frequency method, which involves a problem of reverse rotation once misdetection of the permanent magnet polarity should occur, and another one is a current drive method, which has a problem that phase and speed oscillations are caused by quick speed changes. Hence, authors propose adoption of the current drive method for the basic control system with added compensation of stabilization by means of the high frequency method. This combination secures stable control with no risk of reversal and less vibration. In addition, authors have also considered a frequency separation filter of a shorter delay time so that current control performance will not lower even when high frequencies are introduced. This filter has achieved simplified compensation using repetitive characteristic through the utilization of the periodicity of high frequency current. Simulation and experiment have been conducted to verify that the stable performance of this system is improved.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.31-34
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• 1998

CDMA base station SAW filter has been designed and fabricated successfully. Through the computer simulation, SAW filter is designed to have center frequency of 69.99MHz, ripples lower than 0.7dB and rejection level lower than 50dB. To obtain low noise band pass SAW filter, Input electrode has a apodization type and output electrode has a withdrawal type. For the fabrication of the SAW filter, Al thin film is deposited to the quartz substrates. The fabricated SAW filter has center frequency of 70.5MHz, ripples of 1dB and rejection level of 45dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.10 no.4
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• pp.155-158
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• 1985

A simple active-R filter is proposed by utilizing only four resistors and two operational amplifiers. This filter has multi-functional characteristics and decreases the ratio of resistors. The sensitivity of $W_r$ and $Q_r$ as the parameter of filter is very low and the operating frequency of this active-R filter is possible in the high frequency. The integration of this active-R filter is easy due to the decrease in the number of resistors and the lowering of the ration of resistors. The experiment shows that all the characteristics of this active-R filter are in accordance with thory.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.188-192
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• 2003

A multilayer two-stage LC bandpass filter using low-temperature cofired-ceramic (LTCC) is proposed in this paper. The proposed bandpass filter is composed of two ceramic substrates with different dielectric constant instead of single ceramic material from top to bottom layer. The bandpass filter size is $2.0 mm{\times}1.2 mm{\times}0.8 mm$. Positioning of attenuation polefrequency, importance parameter for a performance of filter, is discussed using even-odd mode analysis by tuned capacitance of coupling capacitor and those results is implemented to LTCC filter circuit. Measured filter performances show that the insertion losses are -4.5dB, -4.1dB at 2.45GHz, 2.75GHz and the return losses are -8.5dB, 8.7dB.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.1
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• pp.48-53
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• 2000

The novel integration method with programmable high-pass filter is suggested in order to solve the problem of integration for stator flux estimation in a stator flux oriented direct vector controlled induction motor drive system. The dc offset in a pure integrator is eliminated using high-pass filter with fixed time constant, and then time constant of programmable high-pass filter is controlled with a inverter frequency for integration in a wide frequency range, considering phase lag and attenuation due to both the hardware low-pass filter and high-pass filter. The proposed method is verified with the experimental results implemented by 32-bit DSP.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.10-17
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• 2009

This paper analyze the effect of frequency offset for the IEEE 802.15.4b LR-WPAN(Low-Rate Wireless Personal Area Network) with 915MHz bandwidth noncoherent DSSS O-QPSK based receiver system, and presents a compensation method with addition of differential filter to the system for compensation of frequency offset problem. DSSS PSSS-ASK and DSSS O-QPSK modulation techniques are accepted within the regularization of IEEE 802.15.4b. These new method can obtain 250kbps transmission rate. The DSSS O-QPSK modulation method that is used in this paper has no BER variation below 40ppm(frequency offset 36.6kHz), but if the offset frequency become high above 40ppm, then the system cannot have stable receiving condition due to worse BER. To solve this problem, we present a more stabilized receiver system at maximum frequency offset ${\pm}80ppm$ using MDDF unti a correlator of DSSS O-QPSK modulator. Moreover computer simulation results will be presented to evaluate the performance of the proposed algorithm unde various AWGN and frequency offset environment.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.239-242
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• 1997

In this paper, the new filter that reduced output ripple to zero is proposed. This filter is composed of transformer and capacitor. The operating mode is verified with theoretical analysis of low ripple filter and computer simulation. DC-DC converter of input voltage DC 100[V], output 30[V]/30[A], switching frequency 20[KHz] is manufactured. In the result, computer simulation analysis is same to experimental result.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.357-360
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• 1999

A 20 MHz CMOS continuous low-pass filter using simulated floating inductor consisted of two fully-differential transconductors and a capacitor is presented. The theory of operation is described and simulation results show close agreement between predicted behaviour and experimential performance. Simulation results show that the filter has ripple bandwidth of 22 MHz, pass-band ripple of 0.36 ㏈. and cutoff frequency of 26 MHz at supplay voltage of $\pm$3 V. The power dissipation is 19.2 ㎽.