• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.483-488
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• 2020

In recent years, the demand for wireless devices incorporating several wireless communication systems into one has been increasing in order to provide services that meet the diverse needs of consumers. Wireless devices consisting of various wireless communication systems require many frequency fixed filters. A frequency tunable filter can replace a number of frequency fixed filters in the wireless devices. If a frequency tunable filter is used in wireless systems, the system can be configured more efficiently. In this paper, a 3-pole frequency tunable BPF(bandpass filter) operating in the frequency band of 800 ~ 2400MHz is designed. In order to widen the operating frequency band, a tuning screw is designed to have a step and a linear motor is used to facilitate the adjustment of the tuning screw. The implemented frequency tunable BPF operates in the designed frequency range and has the maximum insertion loss of 2.82dB in the channel band and the minimum attenuation of 18.7dB at ± 50MHz frequency offset from the center frequency of the band.

• Proceedings of the Optical Society of Korea Conference
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• 2006.02a
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• pp.365-366
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• 2006

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2108-2110
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• 2004

In this paper, a novel tunable bandpass filter using tunable series inductors and MEMS switches for wireless LAN applications was proposed. The proposed tunable filter was fabricated using a micromachining technology and performances of the fabricated filter were estimated. The filter consists of spiral inductors, MIM capacitors and direct-contact type MEMS switches, and its frequency tunability is achieved by changing the inductance that is induced by ON/OFF actuations of the MEMS switches. The actuation voltage of the MEMS switches was 58 V, and the measured center frequencies were 2.55 GHz and 5.1 GHz, respectively. The passband insertion loss and 3-dB bandwidth were 4.2 dB and 22.5 % at 2.55 GHz, and 5.2 dB and 23.5 % at 5.1 GHz, respectively.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.1038-1043
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• 2012

In this work, a high tunable capacitor using a multi-layer dielectric of BZN/BST/BZN is designed and characterized for reconfigurable RF applications. By utilizing a high tunable BST ferroelectric and a low-loss BZN paraelectric thin film, a multi-layer dielectric of BZN/BST/BZN obtained a tunability of 47 % and $tan{\delta}$ of 0.005. The fabricated tunable capacitor on a quartz wafer using this multi-layer dielectric achieved a Q-factor of 10 and tunability of 60 % at 800 MHz and 15 V. Its size is $327{\times}642{\mu}m2$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1177-1181
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• 2006

In this paper, we proposed the new wavelength tunable filter for wide tunability of fiber ring laser. The proposed filter consists of the cascaded connection of Fiber Reflection Mach-Zehnder Interferometer and Sagnac filter or of hybrid filter and fiber Reflection Mach-Zehnder Interferometer. The simulation shows that the continuous tunable range of 50nm can be obtained and that more stable single mode operation of ring laser can be expected due to narrow FWHM. of filter spectrum.

• Journal of Advanced Navigation Technology
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• v.14 no.2
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• pp.176-182
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• 2010

This paper proposes that an inverse class-E amplifier is used a tunable parallel resonator at output port in order to maintain a high power-added efficiency(PAE) and output power with wide frequency ranges. A tunable circuit has a constant Q factor at operating frequency ranges and because of using varactor diode, the inductor and capacitor values of resonator can be changed. Also, the inductance value for zero-current switching (ZCS) is implemented a lumped element and the capacitance value is made a distributed element for phase compensation. The inverse class E amplifier using tunable parallel resonator is obtained to deliver 25dBm output power and achieve maximum power added efficiency(PAE) of 75% at 65-120MHz frequency ranges.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1122-1128
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• 2008

A novel tunable bandstop filter was proposed. It is composed of a right-handed transmission line, which has lowpass characteristics, and a left-handed transmission line which has highpass characteristics. Dispersion relations for the unit cells of RHTL and LHTL were derived by the method of ABCD parameter analysis. Varactor diodes and chip inductors were used to make the unit cells of RHTL and LHTL. A tunable bandstop filter was designed and fabricated by the parallel connection of RHTL and LHTL. The measured results of the proposed tunable bandstop filter are agreed well with the simulated results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.2
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• pp.446-450
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• 2011

Tunable SC(Switched Capacitor) bandpass ${\Sigma}-{\Delta}$(Sigma-Delta) modulator used in wireless system receiver occurs a signal attenuation according to tuning of center frequency in signal bandwidth. In this paper, tunable bandpass 4th order SC bandpass ${\Sigma}-{\Delta}$ modulator with novel structure is proposed for rejection of signal attenuation in signal bandwidth. The existing structure uses a ten variable coefficient values for rejection of signal reduction in the modulator. But the proposed structure only use a two variable coefficient values for rejection of signal attenuation in the modulator. Also, an adder and comparator is replaced with a comparator having 4 inputs in the modulator. Therefore, the existing structure has one more OP-AMP. The purposed modulator was designed in $0.18\;{\mu}m$ CMOS technology. The resolution of the modulator within 310 kHz bandwidth and 40 MHz sampling frequency under 6.67 MHz, 10 MHz and 13.33 MHz intermediate frequency are over 10 bit.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.674-679
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• 2003

We fabricated erbium-doped fiber ring laser with a new structure that can operate in C- & L-band wavelength region. The wave-length of the laser can be tuned continuously over 102 nm between 1510.4-1612.6 nm by insertion of the fiber Fabry-Perot tunable filter (FFP-TF) in the ring cavity. By use of the wavelength tunable characteristics of our fiber laser, we measured absorption spectra of more than fifty transition lines of the acetylene ($^{13}$ C$_2$H$_2$) molecule with high signal to noise ratio (SNR).

• Current Optics and Photonics
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• v.4 no.6
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• pp.477-482
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• 2020

Recently, one of the authors has been reported an optically tunable fiber Bragg grating (FBG) with a photomechanical polymer. It was based on a typical FBG with a downsized diameter of 60 ㎛, coated with azobenzene-containing polymer material. Azobenzene is a well-known reversibly photomechanical stretchable material under ultraviolet (UV) light. The small part of the functional-coating region on the FBG absorbed UV light, which pulled the UV-exposed part of the grating. It was selectable as tunable FBG or tunable chirped FBG, by adjusting the position of UV exposure on the grating. As proof of concept for the tunable FBG device, the characteristics just including UV-induced center-wavelength shift and spectral-width changes of the device were reported. In this paper, we report for the first time that the microactuator makes it possible to control the spectral shape of the FBG reflection, according to the specifications (shape and intensity) of the UV beam that reaches the FBG coated with the azobenzene polymer. In addition, we provide the group-delay profiles for the chirped FBG, so that the sign of its dispersion (normal or anomalous) can be tailored by simply selecting the moving direction of the UV light's displacement in the experiment.