• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.6
• /
• pp.548-553
• /
• 2004

In this paper, single, two, and three-section microstrip directional couplers are implemented for realizing the high directivity characteristics. The achievement of the high directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by gap coupling of open stub formed in sub-coupled line. Therefore, insertion loss and power handling capability are not affected by the gap coupling. The proposed structure is easy to fabricate and incorporate another microwave device due to the planner microstrip. We designed and fabricated single, two, and three-section directional coupler with 20 ㏈ coupling. In spite of microstrip structure, the capacitive compensation structure shows 30 ㏈, 27 ㏈, and 25 ㏈ of directivity in single, two, and three-section directional couplers, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.8A
• /
• pp.626-632
• /
• 2003

In this paper, forward-wave -3㏈ directional coupler with finite-thickness conductor and asymmetrical coupled lines are designed and experimentally verified using mode-matching based design methodology. Most of studies published in the literatures about the coupled lines are mainly concentrated on the adjustment of coupling amount by changing various geometric configurations. The analysis results in this paper show that thicker metalization requires reduced coupler length in the forward-wave directional coupler composed of asymmetrical coupled lines. Several forward-wave directional -3 ㏈ couplers with finite metalization thickness composed of asymmetrical coupled microstrip lines have been designed in the 5 ㎓ based on proposed design method. The measured data show -4.05㏈∼-4.09㏈ coupling at center frequency which is very closed to design value. The tight coupling has been implemented with accurate design methodology which take mentalization thickness into account.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.35D no.2
• /
• pp.13-18
• /
• 1998

In this paper, a new type microstrip directional coupler has been designed and a 3dB coupler has been fabricated and measured. The measured and analysed results are agree well each other except difference of 1 dB insertion loss. There are two eigenmodes, e.g. even and odd mode in coupled microstrip lines. By using the difference between these two eigenmodes phase constants, the directional coupler can be designed by adjusting coupling length, which has a desired coupler has a disdvantage that its coupling length is longer than conventional oe, but it may be used as a useful coupler in millimeter wave range. And it has the merit of less discontinuity effects, becuase it is simpler than the other couplers in structure.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.3
• /
• pp.22-28
• /
• 2008

It proposes the novel design conditions to maximize the power coupling of active directional couplers with mismatched access guides. To verify the validity and accuracy of the conditions proposed, a new coupling efficiency is defined and it depends on the reflection coefficients occurred at the discontinuous input/output interfaces. The numerical results reveal that the phase-matched condition and the minimum-gap condition for those couplers are no longer suitable to optimize the design parameters and a new criterion is needed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.10
• /
• pp.1036-1043
• /
• 2003

In this paper, novel lumped equivalent circuits for a conventional parallel directional coupler are proposed. This novel equivalent circuits only have self inductance and self capacitance, so we can design exact lumped equivalent circuit. The equivalent circuit and design formula for the presented lumped element coupler is derived based on the even- and odd-mode properties of a parallel-coupled line. By using the derived design formula, we have designed the 3 dB and 10 dB lumped element directional couplers at the center frequency of 100 MHz and 2 GHz, respectively a chip type directional coupler has been designed with multilayer configurations by employing commercial EM simulator. Designed chip-type directional couplers have a 3 dB-coupling value at the center frequency of 2 GHz and fabricated lumped directional coupler on fr4 organic substrate has a 3 dB, 10 dB-coupling values at the center frequency of 100 MHz. Excellent agreements between simulation results and measurement results on the designed directional couplers show the validity of this paper. Furthermore, in order to adapt to multi-layer process such as Low Temperature Cofired Ceramic (LTCC), chip-type lumped element couplers have been designed by using this method.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.4
• /
• pp.187-192
• /
• 2017

Rigorous longitudinal modal transmission-line theory (L-MTLT) is applied to analyze maximum power transfer in asymmetric grating-assisted directional couplers(A-GADC). By defining a coupling efficiency amenable to rigorous analytical solutions and interference between symmetric and asymmetric supermodes, the power exchange of TE modes as a function of propagation distance is numerically evaluated. The numerical result reveals that maximum power transfer occurs at a grating period ${\Lambda}_{eq}$, in which the insertion loss of supermodes is equal to each other. That is, it is generally different from conventional phase-matching condition of GADC. Furthermore, as the asymmetric profile of grating change to symmetrical profile, the coupling length decreases and the coupling efficiency for power transmission increases.

• Korean Journal of Optics and Photonics
• /
• v.18 no.5
• /
• pp.295-302
• /
• 2007

This paper presents a rigorous comparison of the design characteristics of polarization-insensitive directional coupler (DC) and multimode interference (MMI) coupler based on rib type waveguides, by using longitudinal modal transmission-line theory (L-MTLT). It shows that the multimode mixing and interference property of MMI can be structurally designed through the continuous evolution of the two-mode coupling property of DC. It also compares and analyzes the coupling efficiency along with the coupling length and the wavelength between polarization-insensitive DC and MMI. From the design properties obtained, it demonstrates for the first time the integration of polarization-insensitive DC or MMI with a Bragg grating and evaluates precisely the filtering characteristics. The numerical results reveal that the DC, as long as it is designed to have the same coupling length for TE and TM modes, has better performance than the MMI in polarization-insensitive filtering behaviour. However, it shows that the MMI with much less coupling length than DC is preferred in the miniaturization of integrated devices.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.8
• /
• pp.1108-1116
• /
• 1993

Y-branch directional coupler optica1 switches with two different coupling lengths are fabricated on z-cut LiNbO3 and tested at r = 1.3 rm. The normal mode and coupled mode theories are utilized to calculate device coupling length and switching voltage. Simulation of the beam propagation method (BPM) is also performed to confirm the device coupling lengths. For dc operation, experimental results are in good agreement with the modee theories expectation.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.3
• /
• pp.47-52
• /
• 2011

Directional couplers based on plasmonic waveguides with nano-scale three channels are designed by utilizing mode coupling effect as well as rib-guiding structure. Longitudinal modal transmission-line theory(L-MTLT) is used for simulating the light propagation and optimizing the design parameters. The designed plasmonic coupler operating as power splitter has nano-scale size of about 200~250 nm width. In order to achieve the desired power splitting ratio, the refractive index of guiding modes is evaluated along the width variation of center channel. Finally, a power splitter based on triple rib directional coupler, which ensures maximum power transfer from one outermost guide to the other outermost guide, is designed.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.503-510
• /
• 2004

We propose a novel vertical directional coupler switch using a vertical directional coupler with polarization independent coupling lengths employing the doublesided deep-ridge waveguide structure. This switch is composed of a switching operation induced section with symmetric structures and an extinction ratio enhanced section with asymmetric structures. We present design methods and examples for this switch with very short lengths and very high extinction ratios larger than 30 dB for both TE and TM modes in cases of both cross and bar states.