• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.346-351
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• 2001

A new analysis method was proposed, where the even . odd-mode theory for a symmetrical coupled-line directional coupler was applied to a transformer-type directional coupler. In addition, the tap-offs were analyzed by the proposed theory, which are widely used in CATV (Cable Television), DBS (Direct Broad- casting Satellite), CS (Communication Satellite) systems. By comparing the calculation results to the measured ones using the even . odd-mode reflection coefficients only, the validity of the proposed analysis method was confirmed. Then, the tap-off has been broadened from 5 MHz over 4,000 MHz by adopting the proposed theory.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.12
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• pp.22-31
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• 2000

A new analysis method of Tap-011 for CATV and DBS systems was proposed and investigated by using 4-port and 3-port equivalent circuits. As an analysis method the even odd-mode theory for a symmetrical coupled-line directional coupler was introduced, and then it was applied to transformer type directional coupler. By comparing the results of simulation and measurement, the validity of the proposed analysis method was confirmed. Furthermore, the Tap-off has been broadened from 5 MHz to 2.500 MHz by adopting the proposed theory.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.120-127
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• 2005

The design method of the transversal filter using continuously cascaded directional couplers is presented. The coupler can be treated for a continuously varying nonuniform coupled transmission line. The design method is based on the optimum extraction of desired coupling factor by the control of null positions which are inherent to the coupling spectra pattern. In the optimization process, the improved Woodward-Lawson sampling method is applied to easily synthesize the distributed delay and weighting elements for transversal filter properties. For application, the microstrip transversal filter is fabricated and optimum dielectric overlay is introduced for the mode phase velocity compensation for non-TEM coupler nodes by using SDA(Spectral Domain Approach). Experiment results confirm the validity of the proposed method.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.335-339
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• 2000

A $1.31/1.55\mu\textrm{m}$ coarse WDM opncal dIrectional coupler that conslsls of two idenlical straight channel waveguides in BK7 glass has been fabricated. The separatIOn between two channel waveguides is $8\mu\textrm{m}$ and the wavegu.ide width is $4\mu\textrm{m}$ . Especlally, we assumed that the index profile is Gaussian function and complementary error function in the width direction and depth direction, respectrvely. This directional coupler operating at $1.31/1.55\mu\textrm{m}$ with crosstalk of 18dB is demonstrated and has the 16 mm long length with 12.6 mm coupling region.region.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.39-42
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• 1993

In this paper, we performed theoretical simulation for directional coupler using BPM program. Simulation results shored that the optimum optical waveguide refractive index between the guides were 3$\mu\textrm{m}$. Using the parameters of n$_1$=2.25, n$_2$=2.25, n$_3$=2.2, gap=3$\mu\textrm{m}$, W= 30$\mu\textrm{m}$, $\Delta$z=0.l$\mu\textrm{m}$, λ=1.5$\mu\textrm{m}$, we decided other design parameters. When we applied 40[V] in the optimum condition of the directional coupling effect, we concluded the refractive index variation of 0.001.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.5
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• pp.34-42
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• 1993

Due to the low loss, broadband and accurate short time delay properties of optical fiber, it has attracted as a delay medium for high speed and broad-band signal processing. In this paper, we consider the coherent optical fiber filter of lattice structure, which uses coherent light sources and consists of directional couplers and optical fiber delay elements.The differences between the optical fiber filter and the ordinary digital filter are 1) the coupling coefficients of directional couplers are restricted between 0 and 1. 2) the optical signal is divided into ${j\sqrt{a}}and\;{j\sqrt{1-a}}$ at the directional coupler. Considering these restrictions, the design formulae and condition of realibility for optical fiber filter of lattice structure which makes the optimal use of optical signal energy are derived.

• Journal of KSNVE
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• v.4 no.2
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• pp.187-198
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• 1994

This study is to describe the effects of the duct termination conditions conditions upon the active noise attenuation system. The adaptive filtering algorithm using FIR filter is implemented for duct noise attenuation. To avoid the instability caused by the acoustic feedback, two methods are considered. One is to use a compensating FIR filter. The other is to utilize uni-directional detecting microphone and uni-directional control speaker. Experimental results show that the reflections of sound from duct terminations greatly reduce the performance of ANC system. The directionality of detecting microphone and control speaker is a major factor to decide ANC performance. When there are some reflections from both duct terminations, the noise attenuation using finite FIR filter is not enough to model the duct plant. Especially, the reflection from the upstream termination reduces the noise attenuation in the frequencies related to the distance between control speaker and upstream termination. The performance of the noise attenuation is found to be largely enhanced by using uni-directional coupler, both on detecting microphone and control speaker, even if the duct system has an arbitrary termination conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.591-598
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• 2003

A novel transversal filter using triple-coupled-line directional couplers is proposed. Simple design method which uses sinc function for computing coupling coefficients of the proposed transversal filter are also introduced. The frequency characteristics of the proposed filter are seldom degraded by the connecting sections between the cascaded directional couplers while those of the conventional transversal filter are aggravated. Moreover, the less number of the connecting sections and the directional couplers is required in the proposed filter than fer the case of the conventional transversal filter having the same bandwidth. The performance of the proposed transversal filter is verified by measurement and the measured results are compared with the calculated results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1000-1006
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• 2007

This paper presents a power detector circuit which monitors the transmitting power for the application in CDMA cell phones. The proposed power detector are composed of coupler for coupling output power and detector fur monitoring output power. The designed coupler has low loss characteristic because it adopts the stripline structure which consists of two ground planes at both sides of signal plane. The design frequency is 824-849MHz which is the Tx band fur CDMA mobile terminal, and the coupling factor of the stripline coupler is -20dB. A schottky barrier diode is adopted for detector design because of its high speed operation with minimized loss. The required impedance matching is performed to improve the linearity and sensitivity of output voltage at relatively low detector input level where the nonlinear characteristic of diode exists. The package parasitics as well as intrinsic diode model are considered for simulation of the detector. The predicted performances agree well with the measured results.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.147-152
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• 2008

This paper has been fabricated the two different type of variable attenuators using a characteristics of a 3 dB directional coupler and pin diodes. One was not analyzed using the conventional even-odd modes but used simple two-port techniques. The resulting scattering parameters described operation characteristics for the general case where the terminating impedances are equal and unequal. After analyzing resistor role of the ${\pi}$ type fixed attenuator. this paper used a pin diode instead of a resistor. The variable attenuators were fabricated using pin diodes for current-controlled attenuation on the coupled ports of a 3 dB branch-line coupler and ${\pi}$ type fixed attenuator. The realized variable attenuators have more than 33 dB attenuation ranges at 2.1 GHz. and the input and output reflection coefficients are less than -13 dB. These results could be applied to mobile communication systems. It can be varied gain of the power amplifier according to change a outdoor environmental temperature and improved linearity.